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Is it true that fluid and thermo dynamic are difficult? 
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#1
Jul111, 04:52 AM

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i heard that fluid dynamics and thermo dynamics are the hardest subjects in mechanical engineering and physics, can somebody elaborate on this issue ?



#2
Jul111, 05:02 AM

PF Gold
P: 7,120

Thermodynamics does have this tendency to really baffle some people. One great quote I've read is:
"Thermodynamics is a funny subject. The first time you go through it, you don't understand it at all. The second time you go through it, you think you understand it, except for one or two small points. The third time you go through it, you know you don't understand it, but by that time you are so used to it, it doesn't bother you any more. " 


#3
Jul111, 08:58 AM

Sci Advisor
P: 5,517

The mathematics of fluid dynamics (classical field theory) is mostly identical to general relativity differential geometry and tensor analysis but I'm starting to see more and more functional analysis: http://www.powells.com/biblio?isbn=9783211826874 Thermodynamics is also a classical field theory, but typical physics curricula spend as little time as possible on this, preferring instead to focus instead on statistical formulations. I was fortunate to have taken a continuum mechanics class through the Mech E department, and I know Chem E departments have excellent courses on thermodynamics/transport theory. If you want to learn those subjects, you may be better off taking engineering classes for the material. I honestly think the 'canonical' US undergraduate physics curriculum is outdated and needs a new structure. For example, I would cut out about half of the typical introductory textbook and replace that with (introductory) quantum mechanics/solid state, computational/modeling, and multidisciplinary topics like colloids and polymers. 


#4
Jul111, 10:14 AM

P: 867

Is it true that fluid and thermo dynamic are difficult?



#5
Jul111, 11:35 AM

P: 1,017

Honestly, I think it depends a lot on how well the subject is taught and on the individual student. I personally found fluid mechanics and thermodynamics to be two of the most enjoyable subjects that I've had to this point. However, they do require some thinking and analysis that is very different from a lot of what most students have done prior to those classes, and as a result, a lot of people do struggle.
The mathematics of fluid dynamics is largely boundary value problems and tensor analysis, with a decent amount of integrals in vector and scalar fields. Some of it depends on the exact course (compressible vs incompressible, as well as differential vs integral formulations of the equations), but that covers the majority of what is needed. Differential geometry might be somewhat applicable, but I would say that it would be far less helpful for fluid mechanics than a good course on tensor analysis and more advanced techniques for differential equations (preferably including numerical methods). Oh, and at least at my school, tensor analysis is taught to the aerospace engineering graduate students. The undergraduate curriculum only includes one semester of fluid mechanics, which doesn't go into enough detail to require tensors. The graduate students are basically required to learn it though, and my graduate fluids courses have been heavily tensor based. 


#6
Jul111, 11:56 AM

P: 1,345

1.) Anything useful is numerical simulations (most of which have been written for you) 2.) Non math majors are not in the best position to learn a lot of the mathematics involved. 


#7
Jul111, 12:40 PM

P: 197

Fluid mechanics is definitely one of the most interesting subjects to me in Mechanical Engineering, and it involves dealing with lot of equations. I believe that's why some people think it is hard. The math behind those equations are not very deep (at least in the undergraduate intro fluid course), but you have to be very careful to understand the assumptions made when those equations are derived, or you will suffer the consequence of applying it wrongly. In a UG level ME intro fluid course, you are unlikely to see tensor analysis. I don't think you will even see how the Navier Stoke equation is derived. In general, in any UG ME continuum mechanics class (solid/fluid etc), tensor technique might be used for some of the analysis, but I don't believe anyone will tell you that's call tensor.
On the other hand, I felt very differently when I took UG ME thermodynamics class. A big part of it involve analyzing engine cycles and related processes, which got boring pretty quick. It has a very different taste than the thermophysics/statistical mechanics course offered by physics dept. The ME course is much more narrow in scope. 


#8
Jul111, 01:47 PM

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#9
Jul111, 01:55 PM

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#10
Jul111, 02:03 PM

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(I'm an aerospace masters student focusing on fluid mechanics and propulsion) 


#11
Jul111, 02:35 PM

Sci Advisor
P: 5,517

Good engineers, like good scientists, don't limit their knowledge to what was taught in class. "lifelong learning" is a silly buzzword, but it's a requirement to stay employable. 


#12
Jul111, 02:54 PM

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#13
Jul111, 03:54 PM

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#14
Jul111, 11:26 PM

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#15
Jul111, 11:30 PM

P: 6,863

For example, if you pump water down a pipe and the Reynold's number goes past a critical value, the flow will become turbulent. Now you can simulate this with various degrees of accuracy, and you can put fluid down a pipe and just see what happens, but no one knows how to calculate the critical Reynolds number from first principles. 


#16
Jul111, 11:33 PM

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#17
Jul111, 11:39 PM

P: 6,863

Also, there is stuff in the physics curriculum that isn't in the engineering curriculum, but the reverse is also true. Most physicists don't get much exposure to finite element methods, which are essential for most engineering. 


#18
Jul211, 12:33 AM

P: 1,017




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