[tranhophu]

Dear all,
I’m a PhD student in France and my question is about the problem “spurious oscilation” in Solid Rocket Motor.
I’m using the source code of my group to solve Navier-Stokes compressible equation 3D (written in DENSITY BASE form) with collocated grid and Explicit Scheme Euler 1st order with Upwind TVD 2nd order and Splitting Flux with ROE approximation scheme used.


We’re looking forward to Mach number which is equal to 1 at throat. After some iteration, we have had the Mach number which is equal to 1 at throat and the mach number in the chamber is about 0.3. In addition, the field of vorticity seems also ok. But when we observe the field of pressure into small range near the mean pressure in chamber (1.7 bar) , we have the problem . There is “spurious oscilation”. On the contrary, into large range of pressure the “spurious oscilation” doesn’t occur. Oscillation pressure in the chamber is like the following figure :





I don’t know how to define the problem which I met and how to resolve it. I wonder if my problem is “pressure-velocity decoupling” on collacated grid or anything else?
Many thanks,
Best regards, and thank you very much for your helpful advices.