Assistance for modelling unsteady supersonic flow in FLUENT
 

Dear Sir,

Project : Supersonic flow past rectangular cavity located in

at the bottom wall of the rectangular test section.

The inlet condition from CD nozzle to test section having rectangular cavity at bottom wall is constant at 1.5 mach & 3.6bar. Due to presence of cavity, the flow becomes unsteady. There willbe oscillating shock waves & acoustic oscillations generated from cavity. Hence I need to evaluate pressure at every approx 10 microsecond for 25000 times at selected nodal points on the top wall so that with this data I can determine the frequencies of pressure oscillation in the test test section using FFT.

I would like to use fluent package for this.

Kindly clarify me the following: 1. Is it possible to model this unsteady, compressible, viscous 2D/3D supersonic flow with fluent package. 2. How to evaluate pressure at selected nodes at every 10 microsecond for 25000(25 thousand) times?

Thanking in anticipation of response.

Re: Assistance for modelling unsteady supersonic flow in FLUENT
 

I don't know how well fluent handels this kind of flow. Rampant should do this.

For reporting tasks I normally use a user-defined-subroutine to write out these data to a file. So you get a table suitable for a fft without the need to stop the calculation or doing a nasty transient postprocessing. Good luck

Re: Assistance for modelling unsteady supersonic flow in FLUENT
 

I think Rampant is now part of Fluent 5. You get at it by choosing the coupled solver instead of the segregated solver

Re: Assistance for modelling unsteady supersonic flow in FLUENT
 

Coupled solver in FLUENT 5 will do the job. For recording pressure history, you should generate the points first. And record time history of pressure signal at those points. For details, please contact your support engineer.

supersonic cavity flow
 

Hi

I am trying to solve such a problem now. Did you solve the problem in fluent? please let me know.

Thank you

Ya fluent will work in supersonic flow,u can monitor the data based on your requirements

Supersonic cavity flow
 

Hi Venkatesh

Thank you. i am trying to solve internal flow of M =1.65 over a cavity. I tried transient simulation initiated by a steady state solution. But no unsteady effects was noted and the shear layer did not oscillate. i am using Density based solver. I have tried mesh refinement and also time step of 1e-6 to 1e-10.

Regards

Hi Venkatesh

Thank you. i am trying to solve internal flow of M =1.65 over a cavity. I tried transient simulation initiated by a steady state solution. But no unsteady effects was noted and the shear layer did not oscillate. i am using Density based solver. I have tried mesh refinement and also time step of 1e-6 to 1e-10.

Regards

Supersonic
 

Hi rajeev

how your confirming there is no change in flow? r u monitoring any location?

Pressure based coupled solver will work better based on my experience, it will vary based on BC

Hi Venkatesh

I am using pressure inlet and pressure outlet and the remaining as wall boundary conditions.
To see oscillations I am monitoring pressure at front and aft wall of the cavity. Animation of Mach no. contour is made but no oscillation of shear layer is observed.

Hello Rajeev,

Did you figure out the solution to the problem? I am doing something similar, though subsonic, but I too can't see the oscillation in the shear layer!

Regards,
Dhaval