Computational Study of Interaction Between Shock and Rarefaction Waves in Expanded Supersonic Nozzle

Supersonic nozzle was studied numerically for different pressure ratios at constant nozzle-throat Reynolds number (Re-t) of 5.9 x 10(6). Two different values of exit-to-throat ratios, e.g. A(e)/A(t) = 1.5 and 2.0 were investigated to analyze the interaction of shock and rarefaction waves behind nozzle exit using rhoCentralFoam solver. The results show that overexpanded condition occurred for both nozzle with 1.5 and 2 exit-to-throat ratios with pressure ratio of p(0)/p(infinity) = 5. Oblique shock waves were formed for both cases at the nozzle exit with much stronger shock occurred for A(e)/A(t) = 2.0 as appeared in the formation of Mach disk. When the pressure ratio was increased further for the case of A(e)/A(t) = 1.5, rarefaction waves was generated, resulting in flow acceleration to much higher Mach number in an underexpanded condition. The interaction between oblique shock and rarefaction waves in nozzle with A(e)/A(t) = 1.5 and p(0)/p(infinity) = 5 showed a similar pattern with that of A(e)/A(t) = 2 and p(0)/p(infinity) = 10.