artifcats in an radialy expending flow

Mehdi

Hi,

I am trying to model the 2D shock between two compressible hypersonic flows. one of my two flows is expending radialy form a source placed in the middle of my space domain. I am using an Upwind-Lax-Friedrich scheme to resolve my Euler's equations, with an cartesian structured grid.

I have a problem in modeling the radial expansion of my first flow. The circular source is discretised using 32*32 cells. When my flow start to radially expend from the source, artifacts occurs showing anomalies between the grid aligned direction and the diagonal directions.

I saw that the major part of works done on that subject (expanding flow or detonation) use curviliniar mesh more appropriate to treat radial expansion.

Infortunatly I need to use my cartesian grid. Is there any solution to minimize the effect of these artifacts (other than using an extreme level of refinement near the source).

Thank you in advance

Mehdi