Large-eddy simulation of compressible turbulent flow in convergent-divergent nozzles with isothermal wall

We present results from high-order accurate large-eddy simulations of compressible flow through convergent-divergent nozzles with and without bell-shaped divergent portions. The nozzles have isothermal walls and circular cross-sections. The incoming flow is a turbulent, subsonic fully-developed pipe flow at M = 0.37 and friction Reynolds number 214. A smooth transition from subsonic to supersonic flow occurs in the nozzles when the back pressure is kept small, accompanied by a reduction of turbulence intensities in the diverging portion of the nozzles. Strong reductions in production and pressure-strain correlations are observed as the flow undergoes acceleration and expansion. When the back pressure is high, the flow in the nozzle remains subsonic, accompanied by a reduction in turbulence in the convergent portion and an amplification in the divergent portion.