# Micro-level water-resources engineering—10: A bridge to end droughts?…

Let me ask you a simple question: Why are bridges at all necessary? I mean to refer to the bridges that get built on rivers. …Why do you at all have to build them?

Your possible answer might be this: Bridges are built on rivers primarily because there is water in the rivers, and the presence of the water body makes it impossible to continue driving across the river. Right? OK. Good.

In India, “kachchaa” (untarred) roads often exist on the sides of the main road or a high-way, as we approach a bridge on a river. These side-roads usually aren’t built after planning, but simply are a result of the tracks left by the bullock-carts plying through the fields, on both sides of the road. People from nearby villages often find such side roads very convenient for their purposes, including accessing the river. The sand-smugglers too find such approach-roads very convenient to their purposes. The same roads are also found convenient by journalists and NGO workers who wish to visit and photograph the same river-bed as it turns totally dry, for quite some time before summer even approaches.

If there were to be no water, ever, in these rivers, then no bridges would at all be necessary. Yet, these bridges are there. That’s because, in monsoon, it rains so much that these rivers begin to flow with full capacity; they even overflow and cause extensive flooding in the adjacent areas. So, naturally, bridges have to be built.

Yet, come even just late winter time, and the river-bed is already on its way to going completely dry. The bridge might as well not have been there.

Thus, the bridges, it would seem, are both necessary and not necessary in India. That’s the contradiction I was talking about.

But why not turn this entire situation to your advantage, and use the very site of a bridge for building a small check-dam?

After all, the very fact that there is a bridge means:

there is enough water flowing through that river, at least during monsoons. We only have to find a way to use it.

Here are some of the advantages of building check-dams nearby a bridge—or may be even directly underneath its span:

• The patterns of water-flow across the pillars of the bridge, and even the pattern of flooding near the site of the bridge, has become well known, even if only because there is a better access to this site (as compared to other potential sites for a check-dam)—because of the existence of the main road.
• There is already a built structure in place. This means that the nature of the rocks and of the soil at the site is already well studied. You don’t have to conduct costly geological surveys afresh; you only have to refer to the ready-made past reports.
• Another implication of there being a pre-existing structure is this: The nearby land has already been acquired. There is no cost to be incurred in land acquisition, and the cost and other concerns in relocating the people.
• Columns/pillars of the bridge already exist, and so, the cost of building the wall of a check-dam can come down at least a bit—especially if the wall is constructed right underneath the bridge.
• Many times, there also is a lower-level cause-way, or an older and abandoned bridge lying nearby, which is no longer used. It can be dismantled so that the stones used in its construction can be recycled for building the wall of the check-dam. It’s another potential reduction in cost (including in the material transportation cost).
• The existence of a bridge at a site can often mean that there is likely to be a significant population on either sides of the river—a population which had demanded that the bridge be built in the first place. Implication: If a water body comes to exist at this same site, then the water doesn’t have to be transported over long distances, because a definite demand would exist locally. Even if not, if the check-dam is equipped with gates, then the stored water can be supplied at distant locations downstream using the same river—you don’t have to build canals (starting from the acquisition of land for them, and further costs and concerns down the way).
• Easy access to transportation would be good for side-businesses like fisheries, even for building recreational sites. (Think agro-tourism, boating, etc.)

Of course, there are certain important points of caution or concern, too. These must be considered in each individual case, on a case-to-case basis:

• The local flow pattern would get adversely affected, which can prove to be dangerous for the bridge itself.
• There is a likelihood of a greater flooding occurring in the nearby locations—esp. upstream! A blocked river swells easily, and does not drain as rapidly as it otherwise would—the causeway or the spillway can easily turn out to be too small, especially in the case of small dams or check-dams.
• The height of the bridge itself may be good, but still, the river itself may turn out to be a little too shallow at a given location for a check-dam to become technically feasible, there. Given the importance of the evaporation losses, the site still may not turn out to be suitable for building a check-dam. (For evaporation losses, see my last post in this series [^].)

But overall, I think that the idea is attractive enough that it should be pursued very seriously, especially by students and faculty of engineering colleges.

We all know that there has been a great proliferation of engineering colleges all over the country. The growth is no longer limited to only big cities; many of them are situated in very rural areas too.

When a problem to be studied touches on the lives of people, say a student or two, it becomes easy for them to turn serious about it. Speaking from my own personal experience, I can say that BE project-reports from even relatively lower-quality engineering colleges have been surprisingly (unexpectedly) good, when two factors were present:

(i) When the project topic itself dealt with some issue which is close to the actual life of the students and the faculty, to their actual concerns.

For instance, consider the topic of studies of design of check-dams and farm-ponds, and their effectiveness.

During my stint as a professor, I have found that rural students consistently show (across batches) reporting of the actual data (i.e., not a copy-paste job).

In fact, even if they were not otherwise very bright academically, they did show unexpectedly better observation abilities. The observation tables in their reports would not fail to show the more rapidly falling water levels in check-dams. Invariably, they had backed the data in the tables with even photos of the almost dried up check-dams too.

Yes, the photos were often snapped unprofessionally—invariably, using their cell-phones. (Their parked bikes could be easily visible in the photos, but then, sometimes, also the Sun.) No, these rural students typically didn’t use the photo-quality glossy paper to take their printouts—which was very unlike the students from the big cities. The rural students typically had used only ordinary bond-paper even for taking color printouts of their photos (invariably using lower-resolution ink-jet printers).

But still, typically, the set of photos would unambiguously bring out the fact of multiple field visits they had made, per their teacher. The background shrubs showed seasonal variations, for instance; also the falling water levels, and the marks of the salt on the dam walls.

Invariably, the photos only corroborated—and not even once contradicted—the numbers or trends reported in their observation tables.

Gives me the hope that one relatively easy way to identify suitable bridges would be to rely on students like these.

(ii) The second factor (for good, reliable field studies) was: the presence of a teacher who guides the students right.

No, he doesn’t have to have a PhD, or even ME for that matter. But he has to know for himself, and pass on to his students, the value of the actual, direct and unadulterated observations, the value of pursuing a goal sincerely over a course of 6–8 months—and the fun one can have in doing that.

OK, a bit of a digression it all was. But the point to which I wanted to come, was academics, anyway.

I think academic institutions should take a lead in undertaking studies for feasibility of converting a bridge into a check-dam. Each academic team should pick up some actual location, and study it thoroughly from different viewpoints including (but not limited to):

• CFD analysis for predicting the altered water-flow and flooding patterns (with the water flow possibly designed to occur over the main wall itself, i.e. without a side-weir), especially for a dam which is situated right under a bridge);
• FEM analysis for strength and durability of the structures;
• Total costs that will be incurred; total savings due to the site (near a bridge vs. far away from it at some location that is not easy to access); and overall cost–benefits analysis; etc.

The initiative for such studies could possibly begin from IITs or other premier engineering colleges, and then, via some research collaboration schemes, it could get spread over to other engineering colleges. Eventually, this kind of a research—a set of original studies—could come to take hold in the rural engineering colleges, too. … Hopefully.

Should the government agencies like PWD, Irrigation Dept., or “private,” American concerns like the Engineers India Limited, etc., get involved?

Here, I think that the above-mentioned academic teams certainly are going to benefit from interactions with certain select institutes like (speaking of Maharashtra) CDO Nasik, and CWPRS Pune.

However, when it comes PWD etc. proper, I do think that they operate rather in a direct project-execution mode, and not so much in a “speculative” research mode. Plus, their thinking still remains grooved in the older folds such as: either have multi-purpose large dams or have no dams at all!, etc.

But, yes, CWPRS Pune has simulation facilities (both with physical scale-models, and also via computational simulation methods), and CDO Nasik has not only design expertise but also data on all the bridges in the state. (CDO is the centralized design services organization that is responsible for engineering designs of all the dams, canals, bridges and similar structures built by the state government in Maharashtra.) The cooperation of these two organizations would therefore be important.

In the meanwhile, if you are not an engineering student or a faculty member, but still, if you are enthusiastic about this topic, then you can do one thing.

The next time you run into a site that fulfills the following criteria, go ahead, discuss it with people from the nearby villages, take a good set of snaps of the site from all sides, write a very small and informal description including the location details, and send it over by email to me. I will then see what best can be done to take it further. (The fact that there were so few engineering colleges in our times has one advantage: Many of the engineers today in responsible positions come from the COEP network.)

The absolutely essential criteria that your site should fulfill are the following two:

1. The river gorge must be at least 25 feet deep at the candidate location.
2. The under-side of the bridge-girder should itself be at least 35 feet above the ground or at a higher level (so that there is at least prima facie enough of a clearance for the flood water to safely pass through the bridge). But please note, this figure is purely my hunch, as of now. I may come back and revise this figure after discussing the matter with some researchers/IIT professors/experienced engineers. For visualization, remember: 10 feet means one storey, or the height of a passenger bus. Thus, the road should lie some 4 stories high from the river-bed. Only then can you overcome evaporation losses and also have enough clearance for flood water to safely pass through without doing any damage to the bridge or the dam.

Further, the preferred criteria (in site selection) would be these:

1. The upstream of the site should not have too steep a gradient—else, the storage volume might turn out to be too small, or, severe flooding might occur upstream of the check-dam! For the same reason, avoid sites with water-falls nearby (within 1–2 km) upstream.
2. The site should preferably be situated in a drought-prone region.
3. Preferably, there should be an older, abandoned bridge of a much lower height (or a cause-way) parallel to a new bridge. Though not absolutely necessary I do include this factor in searches for the initial candidate locations, because it indirectly tells us that enough water flows through the river during the monsoons that the cause-way wouldn’t be enough (it would get submerged), and therefore, a proper bridge (which is tall enough) had to be built. This factor thus indirectly tells us that there is enough rainfall in the catchment area, so that the check-dam would sure get filled to its design capacity—that one wouldn’t have to do any detailed rainfall assessment for the catchment region and all.

So, if you can spot such a site, please do pursue it a bit further, and then, sure do drop me a line. I will at least look into what all can be done.

But, yes, in India, bridges do get built in the perennially drought-prone regions too. After all, when the monsoon arrives, there is flooding even in the drought-prone regions. It’s just that we haven’t applied enough engineering to convert the floods into useful volumes of stored water.

… For a pertinent example, see this YouTube video of a bridge getting washed away near Latur in the Marathwada region of Maharashtra, in September 2016 [^]. Yes, Latur is the same city where even drinking water had to be supplied using trains, starting from early April 2016 [^].

So, we supplied water by train to Latur in April 2016. But then, in September 2016 (i.e. the very next monsoon), their local rivers swelled so much, that an apparently well-built bridge got washed away in the floods. … Turns out that the caution I advised above, concerning simulating flooding, wasn’t out of place. …  But coming back to the drought-prone Latur, though I didn’t check it, I feel sure that come April 2017, and it was all back to a drought in Latur—once again. Fatigue!

PS: In fact, though this idea (of building check-dams near bridges) had occurred to me several years ago, I think I never wrote about it, primarily because I wasn’t sure whether it was practical enough to be deployed in relatively flatter region like Marathwada, where the drought is most acute, and suitable sites for dams, not so easy to come by. (See my earlier posts covering the Ujani and Jayakawadi dams.) However, as it so happened, I was somewhat surprised to find someone trying to advocate this idea within the government last year or so. … I vaguely remember the reports in the local Marathi newspapers in Pune, though I can’t off-hand give you the links.

On second thoughts, here are the links I found today, after googling for “check dams near bridges”. Here are a couple of the links this search throws up as of today: [^] and [^].

… Also, make sure to check the “images” tab produced by this Google search too. … As expected, the government agencies have been dumb enough to throw at least some money at at least a few shallow check-dams too (not good for storage due to evaporation losses) that were erected seemingly in the regions of hard rocks and all (generally, not so good for seepage and ground-water recharge either). As just one example, see here [^]. I am sure there are many, many other similar sites in many other states too. Government dumb-ness is government dumb-ness. It is not constrained by this government or that government. It is global in its reach—it’s even universal!

And that’s another reason why I insist on private initiative, and on involvement of local engineering college students and faculty members. They can be motivated when the matter is close to their concerns, their life, and so, with their involvement the results can turn out to be very beneficial. If nothing else, a project experience like this would help the students become better engineers—less wasteful ones. That too is such an enormous benefit that we could be even separately aiming for it. Here, it can come as a part of the same project.

Anyway, to close this post: Be on the lookout for good potential sites, and feel free to get in touch with me for further discussions on any technical aspects related to this issue. Take care, and bye for now…

A song I like:

(Hindi) “chori chori jab nazare mili…”
Lyrics: Rahat Indori
Music: Anu Malik
Singers: Kumar Sanu, Sanjeevani

[A song with a very fresh feel. Can’t believe it came from Anu Malik. (But, somehow, the usual plagiarism reporting sites don’t include this song! Is it really all that original? May be…)]

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# Micro-level water-resources engineering—9: Your enemy no. 1 is…

I am not sure how the elections affect the actual, on-the- ground activities related to the water conservation efforts, this year. However, the point I want to emphasize here is urgent—and it is technical in nature. It is also of very real consequences. I have made this same point several times over the past few years, but still find that, unfortunately, it still remains worth repeating even today. The point I want to remind you is the following:

Regardless of the scale of your water conservation project (whether farm-pond, small check-dam, big check-dam, KT weir, percolation tanks, dams, etc.), and regardless of whether it’s the building of a new structure or just the maintenance of an old one, remember that:

Evaporation loss is the least appreciated but also a most real factor that is actually operative in India.

Expect that depth-wise, water body that is about 8–10 feet deep will simply get evaporated away in a single year. There is nothing you can do about it. (So far, no suitable technology has ever been invented to cost-effectively counter or circumvent the evaporation losses.)

Also, realize that

A small pond (say 5 feet by 5 feet in area) and a large dam (say 1 km by 5 km in area) both lose the same height of water in the same time period.

For ease in visualization, remember, 10 feet is the height of a typical single storey building.

10 feet also is the height of a typical passenger bus.

Thus, if your farm-pond has water 20 feet deep when fully filled (say at the end of a monsoon), then expect that it will come to hold only about 8–10 feet deep water during the month of May next year—even if no one has taken even a single liter of water out of it, for any use whatsoever.

Further, realize that in any water-conservation structure, you are going to have some clearance in between the top level of the water-body and the top level of the dam-wall (or the pond-wall).

Thus, to have a water body that is at least 20 feet deep, you must have the top of the wall at a height of about 24–25 feet or more, when measured from the bottom of the water body. In contrast:

If the wall of your farm-pond or check-dam itself is only about 12 feet tall, then expect it to go absolutely completely dry during summer.

Don’t blame the failure of a shallow check-dam on any one. Most of all, don’t blame it on the vagaries of nature, don’t blame it on a lack of enough rain-fall “last year.” Blame it squarely on your own ignorance, your own poor design choices.

If your check-dam is not deep enough so as to fully overcome the evaporation loss, and further hold some additional useful depth of water, then it is by design going to be completely useless, absolutely non-functional. It is going to be a pure waste of money.

So, this year even if you are planning to undertake only the maintenance of older structures, drop from your list all those structures which won’t have at least 20 feet deep water body when fully filled (or 25 feet tall walls).

Remember, a penny saved is a penny earned. The same money can be used for building check-dams at better geographical sites, or even doing away with the whole idea of building check-dams (if no suitable site exists nearby a given village, as often happens in the Marathwada region of Maharashtra) and instead going in for just a set of farm-ponds—of sufficiently deep water bodies.

Just throwing money at schemes—whether by government agencies, or NGOs, or even by private parties—is not going to help, if you don’t pay attention to even simplest technical points like the minimum depth of water body.

Foreign authors don’t always adequately highlight this factor of the evaporation loss, because is not very significant in their climates. But it is, to us, in India.

Bottom-line:

If you are in water conservation, remember:

In India, your enemy no. 1 is not a lack of enough rain-fall. It is not even the uneven or non-uniform pattern of the rain-fall, though these certainly are a matter of concern. But they are not your enemy no. 1.

In water resources engineering in India, your enemy no. 1 is: the evaporation loss.

And realize, no feasible technological solution has ever been found to counter it.

All that you can do is to just build farm-ponds or check-dams that are deep enough—that’s all. … Having deep enough water bodies is the most intelligent way of going about it.

I wish all of you ample water supply at least during the next summer—if you spend money intelligently, this summer.

My two cents.

Addendum: My past blog-posts dealing with the topic of water resources may be found here: [^]. In general, the posts which appeared earlier in the series are more technically oriented; the posts that appeared later have been more in the nature of topical repetitions. The post with a high technical content—and also a simplest Python script to estimate evaporation losses—was this one [^]. Also see the next one in the series, here [^].

A late thought: A good project for ME/MTech in water resources engineering:

Given a geographical area (such as a state, region, district, or otherwise, a region defined via watershed areas), estimate the extent of floods that occur every monsoon. Then, estimate the potential amount of storage possible, and the amount actually realized. Be realistic for the second estimate—include seepage and evaporation losses, as well as cost considerations. Develop methodologies for making estimates of all kinds (flooding, seepage and groundwater storage, total on-surface storage potential, the potential that is realized). In the end, consider whether the following statement is defensible: So long as news of floods keep flooding in, we cannot say that the root-cause of water scarcity is the lack of sufficient rains, or uneven (in time) and non-uniform (in space) patterns of rainfall.

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In the recent couple of weeks, I had not found much time to check out blogs on a very regular basis. But today I did find some free time, and so I did do a routine round-up of the blogs. In the process, I came across a couple of interesting posts by Prof. Dheeraj Sanghi of IIIT Delhi. (Yes, it’s IIIT Delhi, not IIT Delhi.)

The latest post by Prof. Sanghi is about achieving excellence in Indian universities [^]. He offers valuable insights by taking a specific example, viz., that of the IIIT Delhi. I would like to leave this post for the attention of [who else] the education barons in Pune and the SPPU authorities. [Addendum: Also this post [^] by Prof. Pankaj Jalote, Director of IIIT Delhi.]

Prof. Sanghi’s second (i.e. earlier) post is about the current (dismal) state of the CS education in this country. [^].

As someone who has a direct work-experience in both the IT industry as well as in teaching in mechanical engineering departments in “private” engineering colleges in India, the general impression I seem to have developed seemed to be a bit at odds with what was being reported in this post by Prof. Sanghi (and by his readers, in its comments section). Of course, Prof. Sanghi was restricting himself only to the CS graduates, but still, the comments did hint at the overall trend, too.

So, I began writing a comment at Prof. Sanghi’s blog, but, as usual, my comment soon grew too big. It became big enough that I finally had to convert it into a separate post here. Let me share these thoughts of mine, below.

As compared to the CS graduates in India, and speaking in strictly relative terms, the mechanical engineering students seem to be doing better, much better, as far the actual learning being done over the 4 UG years is concerned. Not just the top 1–2%, but even the top 15–20% of the mechanical engineering students, perhaps even the top quarter, do seem to be doing fairly OK—even if it could be, perhaps, only at a minimally adequate level when compared to the international standards.

… No, even for the top quarter of the total student population (in mechanical engineering, in “private” colleges), their fundamental concepts aren’t always as clear as they need to be. More important, excepting the top (may be) 2–5%, others within the top quarter don’t seem to be learning the art of conceptual analysis of mathematics, as such. They probably would not always be able to figure out the meaning of even a simplest variation on an equation they have already studied.

For instance, even after completing a course (or one-half part of a semester-long course) on vibrations, if they are shown the following equation for the classical transverse waves on a string:

$\dfrac{\partial^2 \psi(x,t)}{\partial x^2} + U(x,t) = \dfrac{1}{c^2}\dfrac{\partial^2 \psi(x,t)}{\partial t^2}$,

most of them wouldn’t be able to tell the physical meaning of the second term on the left hand-side—not even if they are asked to work on it purely at their own convenience, at home, and not on-the-fly and under pressure, say during a job interview or a viva voce examination.

However, change the notation used for second term from $U(x,t)$ to $S(x,t)$ or $F(x,t)$, and then, suddenly, the bulb might flash on, but for only some of the top quarter—not all. … This would be the case, even if in their course on heat transfer, they have been taught the detailed derivation of a somewhat analogous equation: the equation of heat conduction with the most general case, including the possibly non-uniform and unsteady internal heat generation. … I am talking about the top 25% of the graduating mechanical engineers from private engineering colleges in SPPU and University of Mumbai. Which means, after leaving aside a lot of other top people who go to IITs and other reputed colleges like BITS Pilani, COEP, VJTI, etc.

IMO, their professors are more responsible for the lack of developing such skills than are the students themselves. (I was talking of the top quarter of the students.)

Yet, I also think that these students (the top quarter) are at least “passable” as engineers, in some sense of the term, if not better. I mean to say, looking at their seminars (i.e. the independent but guided special studies, mostly on the student-selected topics, for which they have to produce a small report and make a 10–15 minutes’ presentation) and also looking at how they work during their final year projects, sure, they do seem to have picked up some definite competencies in mechanical engineering proper. In their projects, most of the times, these students may only be reproducing some already reported results, or trying out minor variations on existing machine designs, which is what is expected at the UG level in our university system anyway. But still, my point is, they often are seen taking some good efforts in actually fabricating machines on their own, and sometimes they even come up with some good, creative, or cost-effective ideas in their design- or fabrication-activities.

Once again, let me remind you: I was talking about only the top quarter or so of the total students in private colleges (and from mechanical engineering).

The bottom half is overall quite discouraging. The bottom quarter of the degree holders are mostly not even worth giving a post X-standard, 3 year’s diploma certificate. They wouldn’t be able to write even a 5 page report on their own. They wouldn’t be able to even use the routine metrological instruments/gauges right. … Let’s leave them aside for now.

But the top quarter in the mechanical departments certainly seems to be doing relatively better, as compared to the those from the CS departments. … I mean to say: if these CS folks are unable to write on their own even just a linked-list program in C (using pointers and memory allocation on the heap), or if their final-year projects wouldn’t exceed (independently written) 100+ lines of code… Well, what then is left on this side for making comparisons anyway? … Contrast: At COEP, my 3rd year mechanical engineering students were asked to write a total of more than 100 lines of C code, as part of their routine course assignments, during a single semester-long course on FEM.

… Continuing with the mechanical engineering students, why, even in the decidedly average (or below average) colleges in Mumbai and Pune, some kids (admittedly, may be only about 10% or 15% of them) can be found taking some extra efforts to learn some extra skills from the outside of our pathetic university system. Learning CAD/CAM/CAE software by attending private training institutes, has become a pretty wide-spread practice by now.

No, with these courses, they aren’t expected to become FEM/CFD experts, and they don’t. But at least they do learn to push buttons and put mouse-clicks in, say, ProE/SolidWorks or Ansys. They do learn to deal with conversions between different file formats. They do learn that meshes generated even in the best commercial software could sometimes be not of sufficiently high quality, or that importing mesh data into a different analysis program may render the mesh inconsistent and crash the analysis. Sometimes, they even come to master setting the various boundary condition options right—even if only in that particular version of that particular software. However, they wouldn’t be able to use a research level software like OpenFOAM on their own—and, frankly, it is not expected of them, not at their level, anyway.

They sometimes are also seen taking efforts on their own, in finding sponsorships for their BE projects (small-scale or big ones), sometimes even in good research institutions (like BARC). In fact, as far as the top quarter of the BE student projects (in the mechanical departments, in private engineering colleges) go, I often do get the definite sense that any lacunae coming up in these projects are not attributable so much to the students themselves as to the professors who guide these projects. The stories of a professor shooting down a good project idea proposed by a student simply because the professor himself wouldn’t have any clue of what’s going on, are neither unheard of nor entirely without merit.

So, yes, the overall trend even in the mechanical engineering stream is certainly dipping downwards, that’s for sure. Yet, the actual fall—its level—does not seem to be as bad as what is being reported about CS.

My two cents.

Today is India’s National Science Day. Greetings!

Will stay busy in moving and getting settled in the new job. … Don’t look for another post for another couple of weeks. … Take care, and bye for now.

[Finished doing minor editing touches on 28 Feb. 2017, 17:15 hrs.]

# More on the project ideas. Also, a new CFD software benchmark-cum-shop-floor test.

Update added on 2015.05.17; check out the near the end of this post.

* * * * *   * * * * *   * * * * *

More on the project ideas:

In my last post [^], I had given a description of 3 different ideas for student projects. I would be interested in guiding all these projects in the near future, once I get a suitable job.

If you had gone through my earlier post about my current research interests [^], you would have sure noticed how the project idea no. 2 and 3 relate to my current research in computational modeling of the ceramic injection moulding (CIM) process.

These ideas are basically meant to provide reliable experimental bench-marks for validating separate aspects of the software that I will be writing. (I am still considering and reconsidering the issue of whether to write the software starting from the scratch, or only adapt/extend OpenFOAM.)

The project idea no. 3 (viz., paste-filling in cavity) completely keeps out the aspects of heat transfer and phase transformations, and instead selectively focuses on the aspect of mould-filling using a non-Newtonian material. Thus, if the momentum equations are handled right, predictions about the progress in the filling and the instantaneous shapes of the front at different times would be accurate. If not, the software would have to address only the momentum equations, but with better models/parameter values for the wall friction, viscosity, and surface tension.

In contrast, the project idea no. 2 (viz., melting of wax by a source) tries to selectively focus on the heat transfer and phase transformation aspects, but without significantly involving any momentum transport. (It is anticipated that the symmetry of the configuration means that convection within the molten wax would not be of much significance. However, this part, too, will have to be carefully looked into, at a later stage.)

The CIM process itself involves a liquid-to-solid phase transformation. In contrast, what the idea no. 2 models is the opposite phase transformation, viz., from solid-to-liquid. However, it does have a travelling interface. If the software handles the energy equation, the phase-transformations, and the motion of the liquid-solid interface right, then the speed of the interface should get predicted accurately. If not, the software development work would have to selectively focus only on this part.

Thus, the two project ideas split up the CIM process into two different parts. The reason is the complexity of such problems—the accurate predictions of the instantaneous positions of the moving boundary.

I was only partly successful while comutationally modeling the melting snowman (which I did during my PhD research). The software I wrote had qualitatively predicted the evolution of the shape right, but the speed of the evolution was quantitatively off the mark. I therefore knew that I had to further simplify even just this much part: of transient heat transfer, phase transformation and moving interface, but without any momentum exchanges involved in it. The project idea no. 2 tries to do precisely that: simplify just the heat-related part even further.

In the case of the melting snowman, the outer boundary happens to be the singular location where all the action happens: heat enters, phase-transformation occurs, and then, importantly, the resulting liquid gets drained away, traveling under gravity over the outer surface, and in the process exposing a new surface for the heat to enter, and also moving back the phase-transformation interface. The process thus has a kind of a loop built into it, and so, despite the apparent simplicity, from a modeling viewpoint, it actually is quite complex. Something went wrong with the timings at which the successive processes took place in the simulation. But I could not reliably locate precisely where; I didn’t have any experimental data to be able to do so. My experimentation was too simple; I could not get funds for instrumented data logging, and therefore, I had to remain content with just photographically capturing the outer profiles at successive instants; continuous monitoring of temperatures at various points within the volume of the snowman was not possible.

The current project idea tries to rectify the situation. It reduces the complexity a bit further, by completely doing away with the draining part—the molten wax remains in the jar.

However, in the process, I now realized, the experimental part has become perhaps a bit too simple for a project at the ME level. Some more work could be thrown in. So, here are two possibilities:

1. Also model solidification of wax (instead of only its melting). The liquid-to-solid is anyway the direction of the phase transformation in the actual CIM process.

The simplest model to try would be just to take an instrumented jar, pour some molten wax in it, and let it solidify. If the predictions for the solidification front—its shape and size at various times—are accurate enough, then well and good.

Realize that the project idea no. 2 (viz., wax-melting using a rod for heat input) remains absolutely essential, because experimental errors involved in determining the geometry of the phase transformation front are minimal in it: the boundary of the front has a very simple geometry (ideally, circular on the top surface), and its biggest section remains at the top surface, and therefore easily visible, throughout the process. For both these reasons, its motion would be very accurately measurable. In contrast, in solidification studies, the shape of the solidification front would remain more complicated. Further,  since the front would lie interior to the block, it would not be as easy to measure ina continuous nondestructive manner.

2. Another idea is related to bench-marking and testing. I will later on post this part (may be with a little additions and editing) on iMechanica and CFD-related fora, so as to solicit some informal comments about it. Let me note down a preliminary description here, in the next section.

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A new software benchmark-cum-shopfloor test:

In CFD, the utility of suitable bench-marks is well-established. Think of some typical cases: flow through a converging-diverging channel, flow at a corner or at a T-joint, lid-driven flow with formation of vortices at the corners, flow past an obstacle or over a step and the resultant vortex shedding, the Ahmed body, the Rayleigh-Taylor instability, the dam-break simulation, the falling droplet, etc. These have proved very helpful in validating CFD techniques and software codes/packages—at least for comparing different packages against each other. The idea I propose is in a similar vein.

The proposed experiment is very simple to perform, and yet, it is expected to be very useful. At least I am convinced about its utility enough that I have decided to write a short journal paper on it, just for proposing this test—I mean just for putting forth only the idea of the test, without performing any experimentation/simulation involving it.

Here is the idea.

Take a small solid object, say, a ball-bearing ball made of alloy steel, or a small machined cube of copper, or a small cone of brass. (The surface roughness would need to be specified.)

Hold the object at a suitably high temperature for a sufficiently long of time that it develops a steady temperature throughout its section. Or, assuming that it initially has  been at the room temperature for a sufficiently long time, now place it inside a furnace (or over a hot-plate) of a well-controlled constant temperature for a specified period of time. Basically, the idea is that we come to specify the entire temperature profile of the object.

Take a block of wax of a specified grade i.e. material properties. (Shape and size is to be given some thought, and the issue is to be finalied after some preliminary experiments.) Drill a small hole of a specified shape and size at the center of its top surface. The size of the hole should slightly exceed that of the heated small object.

Place the block snugly fitting inside a well-insulated enclosure (of specified dimensions and material/properties). Or, may be, just place it on a ceramic tile on the laboratory table. (This in fact should work better.)

Rapidly take the small object out of the furnace (or from the hot plate) and gently place it in the hole drilled in the block of wax.

Initially, the hot object will give off its heat to the air above and to the portions of the wax block surrounding it, and so, the wax will melt locally. The object being heavy will displace the molten wax underneath, and thus it will slide deeper into the block. The molten wax will rise from the side-ways. The object will soon get completely covered with a layer of the so-molten wax now convected also onto its top surface. Simultaneously, the column of the molten wax above the object will begin to solidify from the top, by giving off its heat to the air as well as to the surrounding unmolten portions of the block. Also, the heat of the object will continue to get transferred to the wax, and so, its own temperature will go on dropping down, even as it slides down. All these processes will continue until a time when the temperature of the object goes below the melting point of the wax, and so, unable any more to melt the wax, it will come to a stand-still. All of the molten wax wouldn’t have solidified by this time, and so, so we have to wait a little longer for this to happen.

Then (i.e., after waiting for sufficient time), carefully cut through the block, and measure the shape of the region of the wax affected by the heat—in particular, the depth of penetration.

The software should be able to accurately predict the extent of the heat-affected zone, esp. its depth, say as measured by the penetration depth of the object.

This experiment is very simple to perform—it involves no instrumentation. Yet it yields a very specific measure, viz., the extent of the heat affected zone, and most particularly, the depth of the penetration.

However, the process involved in the test is expected to pose a sufficiently difficult case for any CFD software to handle. There is transient heat transfer in two different phases, two successive phase transformations (solid-to-liquid, and then, also liquid-to-solid), convection of liquid wax, buyoancy effects for both the molten wax and the hot object, and motion of the solid-liquid interface. Yet, the overall geometry remains simple enough.

In CFD, people have been studying things such as rising of bubbles and rising/falling of droplets of a second-phase fluid. The process here is somewhat similar.

It is anticipated that during the experimentation, the test should also show good repeatability, provided the wax is homogeneous, and different blocks carry the same material properties.

For processes such as the CIM, the proposed test should be of definite help in two completely different ways: not just as a benchmark for validating software, but also in industrial practice, as a convenient shop-floor test for characterizing the feedstock (i.e. for the routine process quality-control purposes).

For the latter purpose, the feedstock would have to be pressed into the form of a block. This may be achieved via simple cold-pressing, say by filling the feedstock in a container of a square base and then simply placing a specified weight on its top for a specified period of time. These aspects need to be looked into and finalized after some preliminary experimentation.

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This update concerns the software benchmark. A couple of points occurred to me after publishing the post.

1. Note the difference of this test from the hot penetration test of bitumen, or the hot hardness test of metals.

In the proposed test here, the hot object gets completely immersed within the wax block. We are interested not only in melting, but also in the relative motion between the hot and cold objects even as cooling takes place simultaneously. Further, we are also interested in solidification. Finally, unlike those two tests, we are not interested in measurements of forces.

(Indeed, when I thought of this idea, the hot hardness/penetration tests were not even in my peripheral awareness; I was just trying to have as simple a test suitable for processing like CIM, as might be possible.)

2. On the second thoughts, completely doing away with instrumentation may not be such a good idea.

Going by my experience of simulating the melting snowman (as well as my browsing of the transient simulations, and their experimental validations), I think that if this test is to be used as an experimental benchmark for software validation (rather than just as a quick quality-control test on the shopfloor), then it should also specify measuring the precise positions of the hot object at different times, and not just the final depth of penetration it reaches.

In other words, the software should be able to predict the times required to reach the intermediate positions, too, accutately. The intermediate times would come out right only if the software handles the entire process right.

Coming to timings, we should not ask only for the final time when the object comes to a rest. After all, it is possible that the computational technique is such that it errs on the intermediate timings, but it does so in such a way that these errors get cancelled out, and so, the total time taken for the object to come to a rest still is predicted right. Such computational techniques will still not be reliable for modeling the actual CIM processing. So, the time-position profile is of primary importance.

Since the wax (and feedstock in general) is not transparent, for experimental measurements of positions, we cannot use light, and so, a simple technique like video shooting wouldn’t work.

However, since the hot object anyway would be metallic (read: electrically conducting), it would always be possible to sense its internal positions using electromagnetic induction. From my experience of the eddy current NDT, I think, it wouldn’t necessarily have to be an LVDT, and the sensing coil wouldn’t have to necessarily enclose the entire block of wax. If my feel is right (though this will have to be determined after a bit of a trial), a simple “one-way” coil placed on one side of the wax block, should also turn out to be sensitive and accurate enough. Of course, the issue of a differential vs. a direct solenoid is something that needs to be looked into separately.

Now, inductive sensing does make the test much more complicated—you have to firsst calibrate the output of the sensing coil. However, realize, the time-position measurements would be performed only in a laboratory, not under the routine production environments. So, it should be OK. …

… Research is always multi-disciplinary. Indeed, knowledge itself cannot be compartmentalized—regardless of what many influential academicians from the Savitribai Phule University of Pune evidently think. (Though, it was not to show them down that I wrote this post/update. I was mainly concerned only with the research, here.)

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A Song I Like:

(Marathi) “manmohana juLatil naa, taaraa punhaa”
Music: Kedar Pandit
Singer: Ketaki Mategaonkar
Lyrics: ??

[There are two versions of this song, both by the same music director, the same singer, the same melody, and in fact, both also come in the same album! One is in the usual Marathi “bhavgeet” style, whereas the other one is in the “jazz” style. (Not quite jazz all the way through, but it does use some Western instruments someway along that genre.) Surprisingly, the melody fits both the styles so well! I honestly cannot decide which one I like better, though perhaps it’s an indication of my age that I am at times inclined ever so slightly towards the “bhavgeet” version. Or may be, it’s because of Kedar Pandit’s restrained but competent “tablaa” which comes only in that version. (I didn’t know anything about him, but the Wiki tells me that he accompanies Pandit Jasraj on all concerts.) Ketaki is young, and does have limitations to her voice, but the songs here have come out very well. May be with a little help coming in from all those track-editing and pitch-correcting software they all use these days. I don’t know really, but that could easily be the case. But it also is a fact that this kind of a melody would suit her well. And, in any case, the final outcome has come out pretty neat. That counts. … I was driving in the Pune city when I first heard the jazz version on radio, and wished I were driving through a lonely rural patch, instead. So, noted down the words, and looked up the ‘net later on. … Give both the versions a try, even if you don’t know Marathi.]

[E&OE]

# An evening by a candle light

Yesterday, it rained in Pune. The newspaper reports today suggested a heavy downpour; 102 mm in 1.5 (or 3) hours. But in the parts of the city where I live, it couldn’t possibly have been 10 cm; by my rough estimates, it seemed like, may be, about 5–6 cm, at the most, about 7–8 cm.

But closer to the point at hand, as is usual in Pune after about 0.00001 cm of rainfall anywhere within a 100 km radius of the city any time within a preceding 1 hour, the electricity was gone.

It was evening, and the clouds had made it a bit darker than what it usually would be at this time of the evening—about 7:30 PM or so. And so, I first stumbled around a bit to find a candle, then realized that I had a cell phone, and so, using its light, I searched for and found the candle, and lit it—I mean the candle.

But as soon as I brought the lit candle to my room, the stronger winds in my room blew it out.

I then remembered a certain gift that my Idea Cellular subscription had generated for me on my birth-day this year (or on the day the last year). It was a scented candle jar. It’s a nice little jar of glass, say about 6–7 cm in diameter and height, with wax filled up to, say, half way through. The jar is thus a nice little thing, and the color of the wax is very beautiful: a faint yellow. It’s actually more or less the same yellow as what Idea Cellular’s brand carries. On a computer monitor (or on the plastic-coated printed paper they un-necessarily insert in the newspapers) it sometimes looks almost pierceingly bright. But a more or less the same hue, now used for the wax, had become, may be due to the dullness of the wax, a very pleasantly soft yellow shade to look at. And, the scent they used for the wax also is nice. (Being a male, both my sense of scent and vocabulary come to an end right at this level of resolution discrimination.) So, all in all, a pretty and neat gift, it was. And, precisely for that reason, I had not yet used it thus far. In the middle-class India, we naturally develop this habit of procrastinating when it comes to using up beautiful things like that.

However, in the faint light of my cell-phone, I now noticed that the level of the wax was such that if the candle were to be lit, its flame would rise up to a level that is only so slightly below the open top end of the jar. If a strong wind were to blow horizontally over its top, how would the flame behave? How fast would it flicker? Would it go out?

To preserve the battery of the cell-phone, I switched it off, and then decided to spend a little time trying hard to very carefully consider the decision: whether to use this candle in the jar right away or not. I could not succeed in it—I mean, in pursuing a nice, prolonged, fair, even-handed, two-sided, balanced, etc. kind of a vacillation about it. There were issues of engineering importance here, and about a minute had already been wasted by now. Thusly, I assured myself to my entire satisfaction that I had waited for a sufficiently long time in very carefully considering the decision. And so, I grabbed that candle-in-the-jar, lit it up, and brought it to my room.

The flame fluttered. But, no, not even the relatively strong winds would put it off.

The lights (I mean the electricity) came back a little while later. But, a couple of ideas for student projects had been born, in the meanwhile. I mean, projects at the master’s level; in particular, in mechanical engineering; and in more particular, in CFD. Here I am going to share these with you.

No, I no longer much care whether I divulge such ideas on the ‘net or not. If someone on the ‘net steals my ideas, he/his work would sure come up during my regular searches, and then I would make him feel ashamed. At least, I would bring out the theft to the notice of the research community. That would be enough for me.

Just one more point before we proceed. While reading the project descriptions, if you catch yourself thinking whether these are serious projects in mechanical engineering proper or not, do one exercise after you finish reading their descriptions: (i) note down the more advanced features of the equipment and experiments, and especially of the CFD simulations/software development, (ii) note down the ranges of the parameters involved in these experiments, perform some dimensional analysis, and then, (iii) think, do ‘net searches, discuss with other people, and thereby come up with at least three separate industrial applications for each.

If you cannot do the last bit, then the next course of action depends on who you are:

(A) If you are a student, then realize that you can always do a project under some other professor, but not with me.

(B) If you are a professor of mechanical engineering yourself, send your resume to the engineering colleges in the Savitribai Phule University of Pune, including COEP; they always very highly appreciate professors like you.

Ok. Let’s now move on to the project ideas themselves.

Project Idea 1:

(2–4 PG students)

Build a longish channel of rectangular cross section out of perspex. Place it horizontally on a table top. Divide the volume of the channel into a few (say 3–4) sections, by inserting vertical perspex walls mounted at the bottom/side-ways, and going up to some 80% of the height of the channel. Let water run through the channel, say from left to right, at various controllable speeds. Sprinkle some tracers in the water, shine some bright light on it, and make a video of the flow. Image process the individual video frames and thus experimentally determine the local flow velocities. Extend and refine the experiment a bit. For instance, think of using a converging channel, channels with uneven thicknesses and depths, inclined obstacle plates, water with suspended particles, or using precision sensors for local water flow, etc. Perform a CFD analysis of all such flows, starting with modeling just one compartment as the lid-driven (but not oscillatory) flow, and then build in the increasing complexity in a step-by-step manner. Some students may focus entirely on writing/adapting software, whether in C++ or Python. Compare the simulations with the experiments. For instance, can you accurately predict the pressure drops across the successive chambers? Can you accurately predict the amount of precipitation of the sediments in the various compartments of the channel? Their location profiles?

Project Idea 2:

(1–2 PG students)

Take a glass jar of roughly the same dimensions as the one mentioned above (some 8–10 cm dia, and roughly the same height). Take some white candle wax, melt it, pour the wax into the jar, introduce some die in it, and let the melt solidify. The solidified wax should continue to show some die streaks. (If the die thingie doesn’t work, sprinkle some bright shiny particles such as the one they use at the time of the Ganapati decorations.) Take a thin copper rod (say 5–10 mm dia) and using the ordinary funnel-holding stand they use in the XI–XII chemistry labs, hold the rod vertically such that its bottom tip pierces the top wax surface to a measured depth (say 5 mm). Now, use a resistance heater (e.g. a circuit similar to that used in the ordinary soldering iron) to heat the copper rod at some distance below the holder. Attach a few thermocouples over the length of the rod between the heater and the wax; also insert a few at various places in the wax, and a few on the outer surface of the jar. Switch on the power supply and continuously record the temperatures at various places, using data-logging cards on a computer. Also, make a video of the wax undergoing melting. During image-processing, the streaks (or the embedded shiny particles) are expected to help locate the molten front. Make careful measurements, and model this process using CFD techniques.

One of the students may focus just on writing a custom-built software to simulate the process (or adapting existing Open Source software). In case you think this is a very easy problem, the answer is both yes and no. Yes, because simulations of melting and flow were done in the computer graphics field more than a decade ago; include in your ‘net search strings such as: “melting” + “flowing” + “Stanford bunny.” The answer is also a no, because as a mechanical engineering software, accuracy is of primary importance to us; mere attractive or realistic looking graphics with fluid dynamical approximations wouldn’t be enough. And, the problem is, in a way, challenging: multiple phases, transient heat transfer with phase change, and a moving interface.

Project Idea 3:

(3–4 PG students)

Design and build a working machine to experimentally study how a toothpaste fills a mould cavity. The mould cavity should be made in some transparent material. In real experiments, for reasons of costs, it would be just a simple chalk-paste, not a bought out tooth-paste. Also design and build apparatus for, or otherwise conduct, suitable experiments to accurately characterize variables/parameters such as: viscosity, wall friction, surface tension, etc. The mould-filling machine itself should allow for variations in the geometry of the inlet, the ram velocity, etc. Make videos of the filling process. Model the process using CFD software and compare with experiment. Once again, the CFD simulation here is complicated: multi-phase flow, moving boundaries, and, more importantly, non-Newtonian fluid (and flow).

Additional possibility: use a shear-thinning material such as the tomato ketchup. Pursuade some one in the food-processing industry that this is worth-while project, and obtain a large supply of the ketchup for free. As to pursuading the faculty of engineering that this is not a research in agricultural engineering alone, leave that worry alone. As with the other projects here, if our results are good, we will publish them only in the mechanical engineering journal(s).

Some of the students may focus just on writing a custom-built software. The problem again is challenging because there is a multi-phase flow, with complex boundary conditions (wall-friction is variable and important, and surface tension is important), and also, there are both moving and coalescing boundaries.

Compare the simulation with the experiment.

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Note: Each of the above projects could also use 2–4 undergraduate students. The mix is approximate; the depth of research and the intricacy and accuracy of experiments is always a variable: sometimes, conducting even simplest-looking experiments, or building a working software, can take students a long time to complete. It all depends, on a lot of factors—including the ability of the student and the amount of hard work he puts in.

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A Song I Like:

[Yeah, sure, Mumbaikars, go ahead and say it: “angrez gaye to zaroor, lekin jaane se pahele, apani aulaad yahaan pe chhoD gaye.” Yes, the language is not a limitation at such times; Hindi, too, is perfectly acceptable at such times, even though, the same thing can of course be expressed also in “assal” Marathi: “ingraz ithun gele tar khare, paN (or better still, pan), jaataanna aapli aulaad maatr ithech soDoon gele.” Also laugh and/or heavily clap thereafter, or exchange friendly slaps with each other, in your typical style(s).]

(Western Classical)
Composer: Mozart
Work: The Piano Concerto no. 21 in C-major (k. 467)