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Hypersonic- Solver Problem with Star CCM+

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Old   March 7, 2013, 11:40
Default Hypersonic- Solver Problem with Star CCM+
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Hussein
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Hi,

I am currently doing My Final year project and I am using Star-CCM+7.06.009 to model Hypersonic flow and Really need help with the things mentioned below.

I am Modelling Hypersonic flow past a waverider (simple caret shaped). I am importing my part from Proe. I have a fluid box around the waverider. I am modelling the inlet and other four sides as free stream while the outlet is modeled as pressure outlet.

I think modelling the outlet as pressure outlet is kind of wrong because the outlet flow is still supersonic. I have contacted other academic and he suggested using what he called "Continuative" boundary i.e. the values at the cells of the outlet boundary is the same as the values of the previous cells which makes sense. However, I cannot find such boundary in Star-CCM+. Does Anyone knows how to set such boundary or what is the best way to model the outlet boundary in a Hypersonic flow?

Does anyone know whether the size of the fluid box around the WR Matters? I currently do not think that it matters because the flow is supersonic?

Also, I am finding it hard to obtain convergence in the Y&z momentum does any one knows of optimal Mesh size and Courant Number? Because currently higher Mesh size with Courant number~0.5 gives better convergence then the same mesh with Courant number=0.1?

Since the waverider is intended to be cruising I am modelling the flow as steady do you think this model is correct?

Any suggestion on modelling Hypersonic flow is appreciated.

Your help is much appreciated.

Regard,
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Old   May 21, 2013, 22:23
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Abdullah Karimi
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Quote:
Originally Posted by h.jaz View Post
Hi,

I am currently doing My Final year project and I am using Star-CCM+7.06.009 to model Hypersonic flow and Really need help with the things mentioned below.

I am Modelling Hypersonic flow past a waverider (simple caret shaped). I am importing my part from Proe. I have a fluid box around the waverider. I am modelling the inlet and other four sides as free stream while the outlet is modeled as pressure outlet.

I think modelling the outlet as pressure outlet is kind of wrong because the outlet flow is still supersonic. I have contacted other academic and he suggested using what he called "Continuative" boundary i.e. the values at the cells of the outlet boundary is the same as the values of the previous cells which makes sense. However, I cannot find such boundary in Star-CCM+. Does Anyone knows how to set such boundary or what is the best way to model the outlet boundary in a Hypersonic flow?

Does anyone know whether the size of the fluid box around the WR Matters? I currently do not think that it matters because the flow is supersonic?

Also, I am finding it hard to obtain convergence in the Y&z momentum does any one knows of optimal Mesh size and Courant Number? Because currently higher Mesh size with Courant number~0.5 gives better convergence then the same mesh with Courant number=0.1?

Since the waverider is intended to be cruising I am modelling the flow as steady do you think this model is correct?

Any suggestion on modelling Hypersonic flow is appreciated.

Your help is much appreciated.

Regard,
When you define the pressure outlet and if the conditions are supersonic/hypersonic, the boundary pressure you give would be ignored and the pressure and other quantities would be extrapolated from the adjoining cells from inside of the computational domain (which is what you mentioned). So, pressure value you would give does not really matter and it is absolutely correct way.

Convergence depends on many factors and you should try to keep a track of CFL.
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