# How to use BC for supersonic inlets? How to split models and use profiles?

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June 29, 2020, 19:05
How to use BC for supersonic inlets? How to split models and use profiles?
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GRed
Join Date: Jun 2020
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Dear Community,

I am a new member to this community and I would like to start by expressing my gratitude to everyone who spends his/her time to answer questions and help fellow ANSYS users.

I am facing the following issue: I have a 2D axisymmetric model of a converging-diverging nozzle with an exhaust region. The structured mesh is used and the inlet BC is pressure inlet, with 3 x10^6 gauge total pressure and 3 x 10^5 supersonic initial pressure. The inlet temperature is 623k. At the pressure outlet, the gauge pressure is 0Pa and the temperature is 293K. I use a density-based solve, Realizable K-e, Non- Eq wall Fn. I use Implicit formulation, Roe-FDS and least shares Cell-based where the flow is second-order upwind and the rest first order. The geometry of is this one:

This gives the following velocity profile on the axis of symmetry:

The issue is : I want to split the model into nozzle and exhaust region. I start with the nozzle geometry shown below and the same inlet conditions described above. The exhaust region is again defined as pressure outlet and left as default.

The velocity profile along the axis is shown in attached images. This is what was expected. It is the same as with the full nozzle + exhaust region model except that it stops at the end of the nozzle.

Then I export the static pressure, total pressure and total temperature profiles at the outlet of the nozzle.
Then I try to create the exhaust region only.

The red lines are the pressure outlet (0 Pa gauge pressure and 293K ). The white lines are the wall, and the blue line is defined as the pressure inlet. I use the static pressure profile in the Supersonic/Initial pressure box, the total pressure profile in the Total pressure box and the total temperature profile in the total temperature box. In the initialisation pane, i click on the "USE SPECIFIED INITIAL PRESSURE ON THE INLETS".

My model doesn't converge, it throws an error "Wrong type". I do not know how to make it work. I can see that the profile data and the Interpolated data are the same. However after it throws an error, when I try to plot the pressures at the inlet they are slightly different than the input profile interpolated profiles (images attached)

Does anyone got any clue as to what is going on? Should my inlet BC be different (its supersonic)? Should my reference Values be different ( i have it as default)?
Any help is greatly appreciated... I spent hours and hours on this =) Thank you very much beforehand for spending the time to read through it. Let me know for any further clarifications.

Best regards,
G.K.
Attached Images
 Nozzle + exhaust axisymm VELOCITY.png (12.3 KB, 1 views) Nozzle only VELOCITY.png (12.5 KB, 0 views) Exhuast only interp SuperSonic Press PLOTaftercalc.png (9.9 KB, 0 views) Exhuast only interp SuperSonic Press prof.png (10.3 KB, 0 views) Exhuast only interp SuperSonic Press INPUTStatic Press.png (7.8 KB, 0 views)

 Tags de laval nozzle, pressure inlet, profile, supersonic flows, supersonic inlet