Simulation of Thermal Flows in ANSYS Fluent

In this tutorial, I will explore the case of a pipe (or a channel) further adding in the temperature boundary conditions. The concept of hydrodynamic and thermal boundary layers would be described in this tutorial using an example from the book of Cengel – Heat and Mass Transfer. I will also teach you how you can plot any variable such as velocity or temperature across any cross-section. This tutorial shall serve as a beginner level introductory lesson for a student.

Part 1:

Part 2:

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A new speed workout

Like I mentioned in my previous post about taking control of the breath while running no matter if its a slow or fast run. When you’re slower, you can force yourself easier to control the breath and experiment your running but when you take your running up a notch, it tends to become difficult. At higher speeds, there is more rigorous breathing (you have felt that before, right?) and that becomes a bit difficult to control. You can’t say no to a breath when you are panting, it has to come in and get out.

So, this week in my speed training, instead of going for a total of 5 sets of (2 minute fast and 3 minute slow), I changed it to 4 sets of (1 minute fast and 45 seconds slow/walk rather). So, after getting warmed up for about ten minutes, I did these 4 sets. And what I observed was. I could handle my breathing just fine while I was running and during recovery, I was gasping for breath. Just before the end of every recovery period, I thought to myself that I won’t be able to run fast now, given that I am breathing like a crazy animal here. But, once my feet started their way, that abnormal breathing pattern fades away automatically and it gets easier to run faster than to recover on a slow pace.

After I was through this, I warmed down for 5 more minutes and did these 4 sets again! God, that was a wonderful workout! I never knew I could handle speed so well and simultaneously recover in that short time. Of course there was a bit of fluctuation in the speeds during the fast pace zones but nevertheless, I didn’t skip any of the set. And I am so very happy about it.

Forces and their unification

There are four forces known that govern everything in this cosmos. Gravity, electromagnetic, strong and the weak force. We usually only feel the first two because the last two are responsible for activities at atomic level. Like the beautiful mass-energy equivalence given by Einstein, people believe that there should be a simple mathematical equation which can constitute all of these fundamental forces and that is how a unified theory can be achieved. However it has not been yet done. I have been quite amused by the symmetry that exists in many parts of nature. If I talk about mathematics, when I used to solve the maxima and minima problems, they usually occurred at symmetry. In physics, Newton’s third law is a beautiful example of how symmetry exists. This symmetry, this simplicity, has always been a thing of pondering for me. I also have this hope that no matter how complex one system is, it’s governing equations could be extremely simple.

Science is a beautiful subject. But sometimes, when it is expressed too scientifically, it becomes difficult to understand even for scientists themselves. Its language should be simple so that people could know it. Most of the fundamental ideas of science are essentially simple, and may, as a rule, be expressed in a language comprehensible to everyone. This quotation of Einstein completely explains it well. But if science is this beautiful, then there should be a unification of these forces, after all these independent entities are keeping this cosmos together. We may not get this unified theory so soon. It may or may not exists. But if it exists and if we are able to find it, that would be a much greater example of how this cosmos which looks so complex, is yet so simple.

A disaster of Science

Nature is usually silent. It does not make much sound. If you listen to the birds chirping in the morning or the evening breeze echoing in your ears, it is pleasant. But is this silence, is this beauty a result of something beautiful? The answer would be NO. To establish this world we live in, Earth has struggled a lot. It has faced a tremendous series of changes in its ecosystem and more importantly, it has been patient enough to host the life it presently has.

But is this equilibrium forever? Of course not. Internal and external disturbances are unavoidable. Luckily, I have not seen any serious external disturbance so far like the dinosaurs saw in their time. But if I talk about internal disturbances in Earth, I must have heard(and felt) many. Earthquakes and thereby generated Tsunamis, floods, volcanic eruptions, cyclones etc. are some of the imperfections in our almost perfect world. These little imperfections are not so serious if I see it from Earth’s point of view considering all those massive collisions, impacts which Earth had in it’s past. But we humans are not as strong as our bearer, we are highly sensitive to these tiny disturbances. Mankind has suffered extremely in some of these situations.

Most recently, Nepal has been a victim of an internal disturbance in Earth’s tectonic plates. What we can do? Obviously nothing. These things are bound to happen. It looks like we have to pay a price every now and then for our habitat on Earth. This universe we live in, it looks so empty and silent. But at the time when it makes some noise, it makes others cry.

(Twenty) Six Degrees of Separation

We live in a big world, indeed a very big world. You can estimate it from the fact that the surface area of Earth is more than 5000000000 sq. km. (do not bother to count the zeros, I am telling you it’s huge) and there are not many people who travel it in their lifetimes. But we, earth-livings, are not really attentive towards the vastness of this universe. We hardly wonder about the extremities of sky while we look at it.

Last week, I was reading a book called “You are here” by Christopher Potter where I found about the classification of this extreme vastness. All the things of this universe can be put into twenty six levels or degrees.

The first degree is from 1 meter to 10 meter i.e up to 10 raise to the power one.  All the humans, many animals (not all) falls in this range. Robert Wadlow was the tallest human (2.72m) in our history. These are the things that we can see when we are near to them and can not be observed as we go far away.

The second degree is from 10 meter to 100 meter i.e 10 raise to the power two. This range includes large animals such as the dinosaurs of whose fossils give us the estimation of their lengths.

Similarly, the third degree covers human things up to skyscrapers. Burj is about 818 meters which is currently the tallest one.

The fourth degree extends up to 10km, Mt. Everest is an example within this range.

Higher levels include orbits of satellites. Hubble telescope orbits at around 600km (Sixth degree). High orbit Earth satellites orbit in the Eighth degree while the natural satellite of Earth, Moon, orbits in Ninth degree.

After the satellites, comes the planets, Venus at it’s closest is in Eleventh degree. And after the planets, our mighty sun can be considered which is at the average distance which falls into Twelfth degree of separation.

This is the criterion that is further extended to estimate the measure of bigger things than sun, such as galaxies and galaxy clusters.

P. S. Six degree of separation is a theory/play that any two persons can be connected to each other with a maximum of up to six interconnections. This is a personal separation space while I talked about what I probably can call cosmic separation.

Truman syndrome

Yes, you are right! I am talking about the famous Jim Carrey movie – The Truman Show. In this, a person’s life is being broadcasted on TV right from his birth. All around him is a fake television set which he believed to be his world. From fake people around him to the fake atmosphere, everything is created artificially around him. This idea takes me back to one of the theories of our world that we all are in some kind of simulation as was Truman.

Though we are usually not that special that we would be watched every moment but after this movie, many persons began to assume this. Perhaps till the time of this movie, they were pretty much not bothered about it whether they were being watched or not. It created some kind of “awareness” among that segment of people. May be because of such people, writer of the movie once said : “You know you’ve made it when you have a disease named after you”

I perceive this movie as an extreme optimistic one as Truman tries to find the reality and the truth by going beyond his fears and limits. He listened to his inner voice when all the voices around him tried to distract him. And this is a very important thing one should do in his life.

Happy Birthday Ludwig Prandtl

I had almost forgotten about him. Thanks to the Physics Today’s Facebook page of whose post hit me right into the face. It was the birthday of one of the marvelous pioneers of my research field, Ludwig Prandtl. Right from my undergraduate days, I have been learning about his work in my favorite subjects of fluid dynamics and heat transfer.

Those who do not know about him, Prandtl, by many people is called as the father of modern fluid mechanics. In fluid dynamics, he has given the very important boundary layer theory which forms the basis of solution of many flow situations. While in heat transfer, he has given a dimensionless number known as Prandtl number, which related the hydrodynamic and thermal aspects of a heat transfer situation.

He must has also been a good teacher. Among his students, I have read about Blasius, Pohlhausen and von-Karmon. They have contributed significantly just like their adviser. To an awesome researcher and a good teacher, Happy Birthday.

P.S. I have known an incredible person who has done excellently in the field of Science and also bears the same first name. He is Ludwig Boltzmann. Though he is famous now, but he was not, till his suicide.