The flow field in a typical inward-turning inlet was visualized using the Planar Laser Scattering(PLS)method in a shock tunnel with a nominal Mach number of 6.The opaque inlet,which is truncated at a series of section...The flow field in a typical inward-turning inlet was visualized using the Planar Laser Scattering(PLS)method in a shock tunnel with a nominal Mach number of 6.The opaque inlet,which is truncated at a series of sections,and the following transparent isolator,are combined to enable the optical access at different streamwise locations.The sequential PLS images provide a tomography-like flow visualization,which confirm the existence of streamwise Counter-rotating Vortex Pairs(CVPs)in both external and internal flow field of the inlet.Generation mechanisms of these CVPs are unraveled with the help of a numerical simulation,among which the cowl notch plays an important role in the generation of surface trailing CVPs along the centerline of the cowl.Moreover,the cowl shock sweeps the internal boundary layer towards the body side,which ultimately accumulates low-momentum flow on the body side in forms of a large CVP propagating downstream through the isolator.The CVPs formed in the shape-transition are responsible for the nonuniform flow field of the inward-turning inlet.This study indicates that the V-shaped cowl notch affects the downstream flow significantly and,therefore,should be examined thoroughly in practical applications.展开更多
In order to get a deep insight of a submerged inlet on the plane surface, the integrated flow field of the inlet and fuselage has been numerically studied. The investigation is mainly focused on the formation of the t...In order to get a deep insight of a submerged inlet on the plane surface, the integrated flow field of the inlet and fuselage has been numerically studied. The investigation is mainly focused on the formation of the total pressure distribution at the exit of the inlet, the structure of the inner flow and the effects of the boundary layer along the fuselage on the performance of the inlet. Moreover, in comparison with the experimental data at different angles of attack, yaws and mass flow ratios, the reliabilities of the computational fluid dynamics（CFD） studied are verified. Results indicate： （1） the CFD results agree well with the experiment results and the relative errors of the total pressure coefficient is less than 1% ; （2） at the inlet＇s exit, the contour of total pressure obtained by CFD is similar to the experiment result except the contour in the low total pressure zone in CFD is slightly larger; （3） the secondary flow at the cross section behave as two counter-rotating vortices. Along the flow direction, the fields influenced by the vortex pair transport downstream and expand to the whole section at the exit; （4） the total pressure loss at the exit of the submerged inlet can be divided into external loss and internal loss. Usually, the external loss is greater than the internal loss, and both decrease with the augment of the Mach number at the exit. In addition, when the angle of attack ranges from -2° to 8°, the total pressure coefficient ascends gradually, due to the reduction of the external loss caused by the less boundary layer flow captured and the invisible change of the internal loss.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11772325,11872356 and 11621202)。
文摘The flow field in a typical inward-turning inlet was visualized using the Planar Laser Scattering(PLS)method in a shock tunnel with a nominal Mach number of 6.The opaque inlet,which is truncated at a series of sections,and the following transparent isolator,are combined to enable the optical access at different streamwise locations.The sequential PLS images provide a tomography-like flow visualization,which confirm the existence of streamwise Counter-rotating Vortex Pairs(CVPs)in both external and internal flow field of the inlet.Generation mechanisms of these CVPs are unraveled with the help of a numerical simulation,among which the cowl notch plays an important role in the generation of surface trailing CVPs along the centerline of the cowl.Moreover,the cowl shock sweeps the internal boundary layer towards the body side,which ultimately accumulates low-momentum flow on the body side in forms of a large CVP propagating downstream through the isolator.The CVPs formed in the shape-transition are responsible for the nonuniform flow field of the inward-turning inlet.This study indicates that the V-shaped cowl notch affects the downstream flow significantly and,therefore,should be examined thoroughly in practical applications.
文摘In order to get a deep insight of a submerged inlet on the plane surface, the integrated flow field of the inlet and fuselage has been numerically studied. The investigation is mainly focused on the formation of the total pressure distribution at the exit of the inlet, the structure of the inner flow and the effects of the boundary layer along the fuselage on the performance of the inlet. Moreover, in comparison with the experimental data at different angles of attack, yaws and mass flow ratios, the reliabilities of the computational fluid dynamics（CFD） studied are verified. Results indicate： （1） the CFD results agree well with the experiment results and the relative errors of the total pressure coefficient is less than 1% ; （2） at the inlet＇s exit, the contour of total pressure obtained by CFD is similar to the experiment result except the contour in the low total pressure zone in CFD is slightly larger; （3） the secondary flow at the cross section behave as two counter-rotating vortices. Along the flow direction, the fields influenced by the vortex pair transport downstream and expand to the whole section at the exit; （4） the total pressure loss at the exit of the submerged inlet can be divided into external loss and internal loss. Usually, the external loss is greater than the internal loss, and both decrease with the augment of the Mach number at the exit. In addition, when the angle of attack ranges from -2° to 8°, the total pressure coefficient ascends gradually, due to the reduction of the external loss caused by the less boundary layer flow captured and the invisible change of the internal loss.
