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-   -   Simulation of transonic flow over NACA0012 airfoil (https://www.cfd-online.com/Forums/siemens/55539-simulation-transonic-flow-over-naca0012-airfoil.html)

 MSc Student August 3, 2006 14:41

Simulation of transonic flow over NACA0012 airfoil

Hi Im trying to simulate a flow of Mach no. 0.8 and angle of attack of 1.25deg over a NACA0012 airfoil. I have some results from a paper for validation purposes. This is shown below. Shock waves can clearly be seen. http://serv4.imagehigh.com/view.php?...&path=/imgs///

In my results i dont see any shockwaves on the upper or lower surface. These are shown below. (the mach no. link doesnt work on its own for some reason please copy and paste the total link to see it please)

http://serv4.imagehigh.com/view.php?id=30449_Mach_No. Plot1&path=/imgs///

http://serv4.imagehigh.com/view.php?...&path=/imgs///

Ive set the density to ideal f(T,P) set the viscosity to use the sutherland equation and the rest of the material properties are default. Air is my working fluid. Temperature cal. is on and conservation is set to total enthalpy. And the turbulence model is k-epsilon/high reynolds number

The pressure reference cell number has been set to a cell right at the inlet and the pressure is 1.e+05 and the temp is 293k for the reference cell.

The mesh is shown below and has 26200 cells:

http://serv4.imagehigh.com/view.php?...&path=/imgs///

http://serv4.imagehigh.com/view.php?...&path=/imgs/// The inlet(red) and outlet(green) boundaries have two sides as shown above in order to simulate more than 1 angle of attack using the same mesh.

The outlet BC is left at default and the inlet boundary is defined as shown below in the pic.

http://serv4.imagehigh.com/view.php?...&path=/imgs///

Ive used MARS differencing schemes on all variables and my factors are set as shown below

http://serv4.imagehigh.com/view.php?...&path=/imgs///

Im not sure why Im not capturing shocks I clearly have mach numbers over the top of the airfoil greater than 1.2.

I have completed the tutorial 6 in the user guide where you capture shockwaves in supersonic flow. Although inviscid flow was used in that case. Can anyone help me please? Are there any tips anyone could give me. Thanks in advance.

 MSc Student August 8, 2006 07:29

Re: Simulation of transonic flow over NACA0012 air

Just an update.

In all cases of my simulation I get the following warning in my .info file that confuses me:

Warning #001 fluid inflow detected at some outflow boundaries where mass fluxes are forced to zero if this condition persists, your results might be wrong. The outflow boundary might not be well specified or the grid might be too coarse near the outflow boundary.

I have an inlet and outlet boundary condition situation with this type of flow.

 Ben August 9, 2006 13:49

Re: Simulation of transonic flow over NACA0012 air

Use a pressure instead of an outlet, unless you have very uniform outflow at a outlet boundary you always get stability and convergence problems. I never use them (well I used them at first a long time ago but gave up long since) if you must insist on using an outlet make sure it is a LOOOOONG way downstream. This is what the error is about too, as I say I cant stand the things, usefull as a chocolate tea pot they are!

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