Large Eddy Simulation (LES) of combustion chamber and gas turbine
شبیه سازی گردابه های بزرگ (LES) محفظه احتراق و توربین گاز
@cfdgroup کانال تلگرام
In my aero talk I mentioned that cfd is great as long as you can trust the results, and that given correct setup cfd will always give you an answer.
So then looking at the idealized diffuser geometry does the results look reasonable? (Hint you are looking at the surface velocity contour plot). Make a guess and then read further.
Well, the answer is no, the results arent correct. In this case the input boundary condition for the body was accidently set as 'slip' instead of 'noslip'. But how did I know that this case was wrong?
Going back to fundamental fluid dynamic theory if you are studying a real world (ie viscous flow) flow there is something called the no slip boundary condition. I've talked about this before but this means that the fluid velocity at the body surface must match that of the body. In this study the body was stationary so the surface velocity contours should all be zero!
This is a very simple mistake, but it creates non physical results. Cfd is an amazing tool, but like all tools you need to know how to use it and when things just aren't correct. Just because you can get a pretty cfd picture doesnt mean that the data you've gotten is any good. Also another reason why it is important to know theory.