[desaim]

Users,

I have read through many posts here on the forum and love this place. I am working on my thesis at Embry-Riddle and have come into a little issue. I am supposed to validate experimental results of a NASA technical memorandum. I was given some generic shapes of launch vehicles and am supposed to study the steady and fluctuating pressure of each body.

Currently I am in the process of running some 2D-axisymmetric cases and from there will be setting up a 3D quarter model case. Once I verify that the flow-field is correct and my steady cases are good, I will switch over and start meshing for DES. I have a few questions that could use clearing up.

1.) I noticed that when meshing the boundary layer, there seems to be high aspect ratio cells due to my delta s. I am trying to keep my y-plus around 25-30 for my RANS cases. Normally I understand that aspect ratio should be kept below 10, but from my reading, having a high aspect ratio cell in the flow direction seems to be normal. I also hear running double precision can clear this up. My high aspect ratio cells can be as large as 2,000

2.) I understand that DES is going to take some computational power and so I heard that Scaled Adaptive Simulations(SAS) in fluent may be a good alternative. Can anyone verify this?

3.) Most of my cases are transonic starting out at a M=0.788. I understand that this is a compressible flow and I have a choice between pressure based or density based. I have divergence issues when using a pressure based solver with a coupled scheme. I am not sure if I can just use a density based solver without any preconditioning. This is a little hazy for me. Maybe I can run a transient case with a large time step to initialize the flow?

BTW all meshing is done in pointwise. Thank you in advance for your help and I plan on sticking around the forums and helping many other people!