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September 23, 2001, 16:53 
PhD in turbulence

#1 
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Dear all,
after my MSc studies I am planing to become a PhD student. I am interested in Turbulence. Esp. in Simulation (LES coupling with combustion, Aeroacoustics). Ideal is a combination of simulation and experimental work for me. My question: Does smb, know important Centers, Universities (worldwide) working in Turbulence where I can apply for an PhD position. Thanks for help Hans 

September 23, 2001, 17:41 
Re: PhD in turbulence

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(1). There is no guarantee that you will be able to get a PhD even if you are planning to become one. So, the first thing to do is to get yourself qualified first. (2). Then, even if you have a PhD thesis subject to work on, no one knows whether you will be able to come up with something new, so that you can pass the final thesis defense. (3). So, if you are interested in getting a degree, then I would suggest that you find an easier way to do so. Look for a place or university where you can get a degree easily. You definitely must avoid some private universities where a PhD normally will take five to seven years to finish. (4).The subject of research normally is part of your advisor's project. So, in that case, there is not much you can do but to work and follow his guidance. LES is a fancy name, and combustion is pretty complex. (5). My suggestion in this area is: look at the practical aspects of real problems in industries first. Then try to get a little deeper to see whether there is a chance to improve the products and the performance. If you still have problems in understanding some of the subjects you just identified, then go back to school and discuss it with the teachers. Combustion has been around for thousands of years, and LES is mostly number crunching by computer. (6). Anyway, if you have to find a place,then you are talking at a school with supercomputer facility to do simulation and combustion.


September 23, 2001, 19:20 
Re: PhD in turbulence

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Go to the job section. There seems to be a few listed phD studentships applied to LES. http://www.cfdonline.com/Jobs/listj...p?category=PhD%20Studentship
You question is good. Not all people post PhD opennings here. If you find out which Universities to check, then you can go to the professors homepage itself and see if they posted any opennings. 

September 23, 2001, 23:24 
Re: PhD in turbulence

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September 24, 2001, 02:26 
Re: PhD in turbulence

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(1). A good suggestion indeed. (2). I think, it is a good idea to go through the research fields of each professor first. So, You have a good overview of what they are doing. (3). Another important issue is: what are opportunities after PhD in this field. You need to consider this before jumping into it.


September 24, 2001, 04:36 
Re: PhD in turbulence

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Check out UMIST (Launder), Imperial College or City University (Younis) in the UK.


September 24, 2001, 05:20 
Re: PhD in turbulence

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Dear John,
You are right. What are opportunities after PhD in this field ? I would very much like to know your opinion. It seems that LES is quite hot for the time being from the research point of view. Regards Li Yang 

September 24, 2001, 08:02 
Re: PhD in turbulence

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Hi there,
I would suggest you contact Prof. Bill Jones in Imperial college London. He is in the Mechanical Engineering Department. I am going starting a Ph.D with him in about 3 weeks time on the subject of LES and unsteady Combustion. You can find hime at this link: http://www.me.ic.ac.uk/thermofluids/staff/wpj.html To the best of my knowledge he is stil looking for someone to work on LES in the application of wall functions in gas turbines. I am sure he will be able to give you more information regarding other possible projects he may have. John. 

September 24, 2001, 18:51 
Re: PhD in turbulence

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(1). From the transient NavierStokes equations to the timeaveraged Reynolds equations, it represents a quantum jump in modeling of the turbulent flow. (2). What the old master did was to open a door to do practical modeling, with the input from the experimental observations. (3). In other words, with the Reynolds equations, one is able to model the global behavior of turbulent flows. It is very important to know that it was done in the time before the computer age. That's why he is a master. He has the vision beyond his time.(4). The Reynolds equations and its applications to the turbulent flows using experimental data, have been proved to be practical using modern computers. So, this approach should be continued and expanded. Our limitation in computing turbulent flows mainly comes from the unfortunate conflict (or stupid approach of promotion) between the wellestablished experimental approach (which was the main stream in 40's, 50's,60's and 70's, ) and the newly evolved CFD in 70's,80's and 90's. (5). Most of the current twoequation turbulence models created drawed heavily from the careful experimental test data of early days. Without the experimental data, there would be no CFD for turbulent flows today. This fact has to be viewed very seriously by any longterm planner. (6). And the lack of accurate predictions of turbulent flow today mainly is a consequence of inadequate research in doing careful experimental testing to provide reliable test data. So, for the CFD approach to be successful, it is necessary to do more careful experimental testing. (period) It is naive to say that CFD will replace experimental testing. Because, CFD depends on the very best experimental test data. (7). So, my definition of "CFD" should be revised to say "CFD is Numerical Analysis and Mathematical Modeling in Fluid Mechanics, based on accurate experimental test data". In other words, there is no way one can get accurate CFD prediction without accurate experimental test data. (8). So, a professional in CFD must also be a professional in experimental testing. The components technology such as meshing and graphic presentation can exist as separate entities, but its application in CFD still requires the knowledge about the test data, especially the behavior of the solution or the physics of the solution. In other words, meshing must follow the solution physics, and the graphics must also be able to see the results. (9). Once we have good experimental test data, and have fully understood the physics of the solution, then we can proceed to do the numerical analysis and modeling. The goal, naturally is to expend the envelope of the experimental test data.(hopefully in the similar category of the problem with similar physics. thus extensive testing costs can be saved. it is no fun to do testing over and over again for the similar environment or problems)(10). Because of the computing time limitation, currently the turbulence modeling has been limited to twoequation model level, which is known to have limitations for certain types of problem and certain region of the flow. At the same time, it is known that certain types of vortices exist in the mixing flow under certain conditions. One of the most famous one is the Von Karman vortex street and jet mixing between flows of different densities.(big white elephant) (11). In a real combustion system, you always have air jets , fuel jets, air cooling jets. So, the jet mixing is always there. (12). Also, in the confined jet system, there is always flow oscillations (or acoustics), coupled or noncoupled. This was a serious problem in the high pressure system of a rocket engine combustor, liquid rockets or solid rockets. As a result, for this type of flow systems, the transient formulation becomes an option even though it is always time consuming to compute transient flows. (13). At this point, you will always see the transient flow behavior, whether it comes from the initial flow field guess, nonconsistent boundary conditions, truncation errors of the numerical scheme used, or the true nature of the flow. (14). The idea is then: to see whether it can capture more features of the global flow behavior which was not possible in the simple twoequation model. (15). At the capturing of the unsteady wake portion, especially if it is real and organized, the transient approach is useful. But if the flow structure is organized, then, the turbulence modeling at the Reynolds equation level should be able to do it, provided that a good set of test data is available. (16). It is important to know that there are periodic flows in turbomachinery. And I think, it is just transient flow, or transient turbulent flow. (17). So, the large eddy simulation or LES, from my point of view, is trying to produce additional flow features, which up to now is missing from the Reynoldsaveraged equations. Perhaps, it is important before things got fully mixed, I don't know. But I think, in most reacting flow system, the flow is fully turbulent, and it is hard to identify the large structures from the timeaveraged behavior. (I think it is difficult to say this cell is laminar flame and that cell is turbulent flame, even if it exists) (18). So, my feeling is, for certain types of reacting flow system, LES (I have no precise definition of it yet) is one natural extension of transient analysis. After all, most density based formulations are transient in nature. It is already taking a lot of time. (unless one is interested in the final steady state solution. in that case, there are ways to speed up the convergence) (19). For experts in the fields, LES could be another new approach to identify new features of the flow. For the rest, modeling using the Reynoldaveraged equations is just the begining. It provides the foundation for modeling of practical turbulent flows. With careful experimental test data, great results can be obtained even in complex flow problems. (20). So, "CFD" is "Test Data based Simulation". You must know how to get accurate test data first, before you can perform meaningful simulation. Otherwise, what you are getting will be "beautiful pictures" only. This applies to the LES also, even though it is a special case of CFD. Will the LES provide more accurate features of the flow field? I don't know. It is up to the expert in this field to answer. (21). By the way, LES should be defined more precisely first, otherwise, it will be another item in the MS name convention, that is the definition becomes a function of time.


September 26, 2001, 07:23 
Re: PhD in turbulence

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Thanks, John. It is very insightful.
Regards Li Yang 

September 26, 2001, 10:01 
Re: PhD in turbulence

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In the Netherlands, there is a national graduate school in fluid dynamics, called the "J.M. Burgers Centre". Some 40 different professors in fluid dynamics (spread over 5 universities in the country) participate in this national school and they all offer PhD positions in various aspects of (computational) fluid dynamics. Turbulence and combustion are core topics in the research program of the J.M. Burgers Centre. Competition for a PhD position in the Centre is quite tough, but they pay (!) a pretty good salary to PhD students (approximately 2000 Euro/month). The thesis must be written in English and obligatory courses are taught in English. Required entrance level is an MSc with sufficient knowledge of fluid dynamics. For BSc's, a special MSc program in fluid dynamics is offered, which prepares you in 1 or 2 years for entering the PhD program. For positions available, check out www.burgerscentrum.org, and look for 'vacancies'.


October 1, 2001, 11:42 
Re: PhD in turbulence

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Try jobs.ac.uk to search for PhD positions in your subject area


October 5, 2001, 05:50 
Re: PhD in turbulence

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Hi peopel It was very interesting to read all your comments on the aproach of the status for experimental turbulence and simulations. Hans if you are still interested to do research on the feald, after all this know how you get, you are verry verry but verry lucky if you understand german and have a look on this home page : project A2. http://www.sfb557.tuberlin.de/
In th same institute Hermann Foettinger Institute was Prof.H.E. Fiedler how did a lot of experimenta work on shear flow an turbulence. The aplication fieldl after a phD in that fieald could be RollsRoyce/Dahlewitz. If hou did it, and have a place at the HFI, thinck about me if I have a question, thanks. 

October 5, 2001, 06:47 
Re: PhD in turbulence

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October 8, 2001, 04:03 
Re: PhD in turbulence

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respected sir, tks for ur message.i would like to pursue my p.hd.,in the cfd area.so if possible please find a problem and give me the guidance to me. i will keep touch with u thro the mail. tks for yr guidance g arun kumar


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