Numerical study of bypass dual throat nozzlewith parallelogram cross-section

A parallelogram section bypass dual throat nozzle(BDTN) was proposed by combining the heterotypic outlet design with the fluidic thrust-vectoring nozzle, and then a comparative study of the flow filed structure and aerodynamic performance with the basic rectangle BDTN was carried out. The results of three-dimensional numerical simulation showed that the parallelogram configuration had the same aerodynamic parameter variation law as the rectangular configuration. Compared with the basic rectangle BDTN, the flow field of the parallelogram configuration changed due to the inclination of sidewalls, resulting in the decrease of the pitch vector angle and thrust coefficient in vectoring mode, while it had little effect on the thrust coefficient and flow coefficient in non-vector mode. The sidewall inclination angle was an important factor for the change of nozzle performance. Under the same nozzle pressure ratio, the lager inclination angle indicated the smaller vector angle. When inclination angles were not less than 60°, stable vector angles above 10° and maximum vector angles above 15° could be obtained. The parallelogram outlet had a better blending effect on the exhaust jet, which could greatly accelerate the attenuation of the centerline velocity of jet flow and contribute to improve the infrared stealth characteristics.