computational mechanics: differences between solid and fluid mechanics?

seif.H.S · January 29, 2015, 20:20

hey
I am first year master student, in the next few days i should choose between solids and fluids mechanics as branch of computational mechanics to do the theses in !!
what i dont understand if i choose solids, is it still I could find jobs as CFD engineer !! and of course dose it run the opposite way

thank you in advance
Kind regards

Dyls · February 2, 2015, 16:38

Now that you are in graduate school you will probably choose a path and become an expert in that area. You might be good at both, but the more focused you become in one specification, the less you will be called upon in other fields. Solids and Fluids problems have some similarities but mostly they are quite different.

Dylan

seif.H.S · February 4, 2015, 10:25

thank you for your reply, but indeed whats confusing is I feel lost as I am not sure of which approach I should take!!
if you have any suggestion, I will be happy to hear from you !!

Seif

mprinkey · February 10, 2015, 10:29

I don't think anyone can tell you what to study. If you are going be doing computational work in either solid or fluid mechanics, the best I can do is give you a flavor for what is involved in each. The greater field of continuum mechanics encompasses both and can make the fields seems more similar than they really are. In truth, they share some similar basic mathematical underpinnings on the front end and they draw on some of the same techniques for solving linear and nonlinear equations on the back end, but the bulk of two fields...even in computational areas...are very different.

I am going to speak in generalities here. What I will say will be true for 90% of what you would do in each. There are cross-over fringe areas of course.

Solid mechanics formulations are often concerned with minimal energy configurations and eigen mode analysis. Some areas may focus on large scale deformations where there is something resembling a "convective" movement of mass or momentum, but for many (most?) cases, this is not true. Deformations will be small. You will talk in terms of strain tensors and nodal displacements. More often then not, these problems will be couched in terms of finite elements which meshes very nicely with the minimal energy/functional calculus aspects of solid mechanics.

Fluid mechanics formulations almost all begin as statements of conservation and flux balances. Flow of mass, momentum, energy, chemical species from one control volume to another with reactions and inter-field coupling occurring in those control volumes. If you look (most) everywhere in CFD, you will see transport equations written for turbulent energy transport, radiation transport, etc. That is the way most CFD is constructed. And as energy minimization principles in solid mechanics leads to finite element formulations, the flux/control volume principles lead naturally to finite volume formulations.

Those are the two paths in front of you. There are side roads connecting the two. They may even be a "grand unification" in the works called the Discontinuous Galerkin Method. Of course, you can do CFD with finite elements, but it is not as common and (IMO) not as natural a fit. And I remember seeing solid mechanics being done with finite volumes. (I think it was Hrv Jasak of OpenFOAM fame...but that was back when OpenFOAM was still FOAM, if memory serves).

As I said, none of us can gauge where your interest may lie. I hope that this gives you a (grossly simplified) flavor of what you might expect.

January 29, 2015, 20:20	computational mechanics: differences between solid and fluid mechanics?	#1
seif.H.S New Member Join Date: Jan 2015 Posts: 3 Rep Power: 11	hey I am first year master student, in the next few days i should choose between solids and fluids mechanics as branch of computational mechanics to do the theses in !! what i dont understand if i choose solids, is it still I could find jobs as CFD engineer !! and of course dose it run the opposite way thank you in advance Kind regards

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February 2, 2015, 16:38		#2
Dyls New Member Dylan Join Date: Mar 2012 Posts: 25 Rep Power: 14	Now that you are in graduate school you will probably choose a path and become an expert in that area. You might be good at both, but the more focused you become in one specification, the less you will be called upon in other fields. Solids and Fluids problems have some similarities but mostly they are quite different. Dylan

February 4, 2015, 10:25		#3
seif.H.S New Member Join Date: Jan 2015 Posts: 3 Rep Power: 11	thank you for your reply, but indeed whats confusing is I feel lost as I am not sure of which approach I should take!! if you have any suggestion, I will be happy to hear from you !! Seif

February 10, 2015, 10:29		#4
mprinkey Senior Member Michael Prinkey Join Date: Mar 2009 Location: Pittsburgh PA Posts: 363 Rep Power: 25	I don't think anyone can tell you what to study. If you are going be doing computational work in either solid or fluid mechanics, the best I can do is give you a flavor for what is involved in each. The greater field of continuum mechanics encompasses both and can make the fields seems more similar than they really are. In truth, they share some similar basic mathematical underpinnings on the front end and they draw on some of the same techniques for solving linear and nonlinear equations on the back end, but the bulk of two fields...even in computational areas...are very different. I am going to speak in generalities here. What I will say will be true for 90% of what you would do in each. There are cross-over fringe areas of course. Solid mechanics formulations are often concerned with minimal energy configurations and eigen mode analysis. Some areas may focus on large scale deformations where there is something resembling a "convective" movement of mass or momentum, but for many (most?) cases, this is not true. Deformations will be small. You will talk in terms of strain tensors and nodal displacements. More often then not, these problems will be couched in terms of finite elements which meshes very nicely with the minimal energy/functional calculus aspects of solid mechanics. Fluid mechanics formulations almost all begin as statements of conservation and flux balances. Flow of mass, momentum, energy, chemical species from one control volume to another with reactions and inter-field coupling occurring in those control volumes. If you look (most) everywhere in CFD, you will see transport equations written for turbulent energy transport, radiation transport, etc. That is the way most CFD is constructed. And as energy minimization principles in solid mechanics leads to finite element formulations, the flux/control volume principles lead naturally to finite volume formulations. Those are the two paths in front of you. There are side roads connecting the two. They may even be a "grand unification" in the works called the Discontinuous Galerkin Method. Of course, you can do CFD with finite elements, but it is not as common and (IMO) not as natural a fit. And I remember seeing solid mechanics being done with finite volumes. (I think it was Hrv Jasak of OpenFOAM fame...but that was back when OpenFOAM was still FOAM, if memory serves). As I said, none of us can gauge where your interest may lie. I hope that this gives you a (grossly simplified) flavor of what you might expect.