Computational study of axisymmetric divergent bypass dual throat nozzle

A bypass dual throat nozzle (BDTN) is a fluidic thrust-vectoring nozzle (FTVN) that is based on the conventional dual throat nozzle (DTN). The BDTN provides high thrust vectoring (TV) efficiency with low thrust loss and does not consume additional secondary flow. A fixed-geometry axisymmetric divergent BDTN (ADBDTN) that has flow adaptive capability and can provide high TV efficiency in the pitch and yaw directions without substantially changing the working state of the engine is investigated in this study. In addition, the TV mechanism and the effects of the expansion ratio, bypass width, and rounding radii at the nozzle throat and cavity bottom on the nozzle performance under the vectored state are presented in detail. Results show that the TV mechanism of the ADBDTN is similar to that of the DTN, which deflects the primary flow through the separation zone inside the recessed cavity. Larger expansion ratios and rounding radii at the nozzle throat contribute to the large pitch thrust-vector angle and high discharge coefficient. Decreasing the expansion ratio and increasing the rounding radius at the nozzle throat can improve the thrust coefficient. As the bypass width increases, the thrust and discharge coefficients increase and the pitch thrust-vector angle reaches its maximum. The effect of the rounding radius at the cavity bottom on the nozzle performance is relatively small. For the configuration with flow adaptive capability, the largest pitch thrust-vector angle is 25.37 degrees and the highest thrust and discharge coefficients are 0.957 and 0.983, respectively. (C) 2019 Elsevier Masson SAS. All rights reserved.