Fluid slows down before reaching airfoil

itb7 · February 16, 2020, 12:11

To all,
I am trying to run a 2-D simulation of compressible flow past a cone in ANSYS Fluent. However, the air seems to slow down immediately after the inlet boundary for some reason, and I don't understand why. I've included a picture of the issue, and my settings are as follows:
model: realizable k-epsilon, standard wall functions
fluid: air, ideal gas
boundary conditions:
velocity inlet, 375 m/s
walls: no slip on the cone, specified shear of 0 on the boundaries

Any advice on this would be appreciated!
https://imgur.com/a/Qs3FyQ5

vinerm · February 16, 2020, 17:14

The image shows temperature and not velocity, hence, it is little difficult to say whether the flow slows down or not. But there are other settings that imply improper setup. You need to make following changes

1. Use SST $k-\omega$ instead of $k-\varepsilon$ . You may also use SA. If you wish to continue with $k-\varepsilon$ , use ML instead of SWF.

2. Velocity inlet is wrong boundary condition for compressible flows. Use farfield or pressure-inlet or mass flow inlet. Farfield is most optimum.

February 16, 2020, 12:11	Fluid slows down before reaching airfoil	#1
itb7 New Member Join Date: Jan 2020 Posts: 2 Rep Power: 0	To all, I am trying to run a 2-D simulation of compressible flow past a cone in ANSYS Fluent. However, the air seems to slow down immediately after the inlet boundary for some reason, and I don't understand why. I've included a picture of the issue, and my settings are as follows: model: realizable k-epsilon, standard wall functions fluid: air, ideal gas boundary conditions: velocity inlet, 375 m/s walls: no slip on the cone, specified shear of 0 on the boundaries Any advice on this would be appreciated! https://imgur.com/a/Qs3FyQ5

February 16, 2020, 17:14	Issues	#2
vinerm Senior Member Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 36	The image shows temperature and not velocity, hence, it is little difficult to say whether the flow slows down or not. But there are other settings that imply improper setup. You need to make following changes 1. Use SST $k-\omega$ instead of $k-\varepsilon$ . You may also use SA. If you wish to continue with $k-\varepsilon$ , use ML instead of SWF. 2. Velocity inlet is wrong boundary condition for compressible flows. Use farfield or pressure-inlet or mass flow inlet. Farfield is most optimum. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

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