ghost fluid method (shock tube problem)
 

Hello

I wnat to solve shock tube problem by ghost fluid method as a boundary condition at the discontiniuty. (such as Fedkew's paper 'GFM for shocks,detonation and deflagration') but in Rieman problem, at first there is not shock and after a very short time shock will appear.

In period of time that shock does not exist, can I use ghost fluid boundary condition for shock? or should I use GFM method after the shock appear?