Computational Aerodynamics Questions & Answers  
Question by Student 201427564
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Professor, I have a question about last Tuesday class. In attached figure, You coded is=1, js=1 in line 8. But you put zero in command 'Corners' in line 27. It works well but I can not understand. Please explain the reason. Also, I think is3 should be declared before is2. Because is2 contains is3. Am I right?
04.01.17
The first two zeros in the Corners() command are for the $x$ and $y$ positions of the lower-left corner. The next two values are for the $x$ and $y$ positions of the upper-right corner. For the second question, yes, if is2 depends on is3, then you should initialize is3 before initializing is2. Two points bonus boost.
Question by Student 201427564
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Professor, when you did this example you coded Block1 and Block4 again(I mean you coded twice for one block.). When I try to coded only {Block1 again!} and {Block4 again!}, it did not work. Could you explain me the reason?
04.03.17
Hm, I don't understand what could be wrong.. You need to explain this more carefully.
Question by Student 201227141
Professor, I think i did assignment. And i found export button in paraview but i could't see the bottom side of the export page. So i just pushed enter of my keyboard but exporting didn't work. How can i do well?
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04.04.17
An easy way around this is by moving the window so you can see the buttons at the bottom. You can move the window by pressing the key “alt”, the left mouse button, and moving the mouse around. Alternately, you can increase the resolution of your screen, but this is more involved..
Question by Student 201527110
Professor, in my opinion, we have to consider about the change of properties when flow pass through the shock for the supersonic flow example you explained today, but there was any no mention about shocks. Could you explain why we can ignore the changing of properties by shock?
04.06.17
Hmm, I didn't mention about the shock today and there is no reason to at this stage.. But I'll give you 0.5 point bonus for the effort.
Question by Student 201127151
Professor, I have a question about the flux jacobian $A$. You explained that the scalar equation for a wave is $$ \frac{\partial u}{\partial t} + a \frac{\partial u}{\partial x} =0 $$ I understood that 'a' is a wave speed. And then you taught that the Euler equations for a wave in 1D is $$ \frac{\partial U}{\partial t} + A \frac{\partial U}{\partial x} =0 $$ Here, 'A' is the flux jacobian and I understood it mathematically. I think that it means the notion of a wave speed like 'a'. But I can't clearly comprehend the meaning of 'A'. What does it means exactly?
04.11.17
Well the mathematical definition of $A$ is the flux jacobian, i.e. $$ A\equiv \frac{\partial F}{\partial U} $$ This was mentioned in class. 0.5 point bonus.
Question by Student 201127151
Professor, I am so curious about the boundary condition of the supersonic inflow. At question #1 - (a) of assignment #6, I find that the boundary condition is the supersonic inflow. So I think that all properties at node 1 are extrapolated externally as follows : $$ T_1^{n+1}=T_{\infty},\; P_1^{n+1}=P_\infty,\; M_1^{n+1}=M_\infty $$ If so, I think $u_1^{n+1}$ and $v_1^{n+1}$ are also regarded as $u_\infty$ and $v_\infty$ respectively. Am I solving it correctly?
04.28.17
Yes, that is correct. But you need to demonstrate why this is through the perpendicular Mach number and wave speeds. 2 points bonus.
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