The effect of viscosity on the mach stem length in unsteady strong shock reflection

Consider a plane shock wave I travelling from right to left with a constant speed q_s into a uniform gas at rest relative to an inertial frame. Let the shock strike a plane wedge whose leading edge is parallel to the plane of the shock. Let the wedge be at rest relative to the same inertial frame. The interaction of the shock wave with the wedge usually causes a reflected shock R to be generated