To research abnormal phenomenon of thrust reduction of a range rocket nozzle was chosen to study

nozzle with the same inlet pressure and different environment pressures were simulated numerically by applying the AUSM+ (advection upstream splitting method)scheme

SST(shear-stress transport) turbulence model and LU-SGS(lower-upper symmetric Gauss-Seidel)implicit algorithm were used to solve 2-D axial symmetry RANS(Reynolds-averaged Navier-Stokes) equations. The differences in thrust characteristics were obtained when the environment pressure varied from 50.67kPa to 101.32kPa

and the cause of these differences was analyzed. Results indicate that static thrust of the outer nozzle exit boundary rises toward the negative direction when the environment pressure gradually decreases

absolute value increases firstly and then decreases. Dynamic thrust and total thrust of the outer nozzle exit boundary slightly changes at the environment pressure ranging from 60.80kPa to 101.32kPa

but dynamic thrust and total thrust of the outer nozzle declines sharply when the environment pressure is less than 60.80kPa.