An experimental study was conducted on turbulent separation behaviors induced by blunt fins with different sweep angles at Mach number 6.0.The Nano-particle based Planar Laser Scattering technique(NPLS)was applied to ...An experimental study was conducted on turbulent separation behaviors induced by blunt fins with different sweep angles at Mach number 6.0.The Nano-particle based Planar Laser Scattering technique(NPLS)was applied to visualize the flowfield,complemented by pressure tests.Sweep angles of the fins were 10°,20°,...,60°,with the same leading edge diameter of 10 mm.Fine structures of the interference flowfield induced by blunt fins have been obtained,including the shock systems and vortexes.It was found that the features and shapes of the detached shock depended on sweep angle.When sweep angle<50°,the detached shock appeared as the form of trailing shock,and the supersonic jet with its reflection could be observed.The detached shock would be curved for the 50°and 60°fins and became a transmitted shock.The Scale-Invariant Feature Transform(SIFT)was successfully applied to obtain the velocity field from NPLS images,and the extent of the separated region was found to decrease with increasing sweep angle.No separation appeared as sweep angle>30°.Two peak values were detected on the centerline pressure distribution.The first peak did not rely on sweep angle,while the second peak value decreased with increasing sweep angle.展开更多
An experimental study was conducted on the interactions of shock wave/turbulence or laminar boundary layer caused by fin-type protuberance, as the lack of detailed understanding of fluctuating pressure loads inside an...An experimental study was conducted on the interactions of shock wave/turbulence or laminar boundary layer caused by fin-type protuberance, as the lack of detailed understanding of fluctuating pressure loads inside and outside the laminar or turbulence boundary layer separation region in hypersonic flow. The changes of fluctuating pressure in separation region were focused on in this paper. The study shows that the existence of fin changes flowfiled on the plate significantly. The laminar boundary layer separation occurs earlier and the separation region is more extensive. Similar flow is observed between a couple of measurement points outside the laminar separation region. However, there are significant differences between the flow inside and outside the separation region. The level of fluctuating pressure of laminar boundary layer is smaller than that in turbulent case. Even so, in laminar case, the peak fluctuating pressure still reaches a high level. Therefore, the structural influence （damage and/or early fatigue） of fluctuating pressure loads caused by the laminar boundary layer separation should not be ignored.展开更多
基金supported by the National Natural Science Foundation of China(No.11902354)。
文摘An experimental study was conducted on turbulent separation behaviors induced by blunt fins with different sweep angles at Mach number 6.0.The Nano-particle based Planar Laser Scattering technique(NPLS)was applied to visualize the flowfield,complemented by pressure tests.Sweep angles of the fins were 10°,20°,...,60°,with the same leading edge diameter of 10 mm.Fine structures of the interference flowfield induced by blunt fins have been obtained,including the shock systems and vortexes.It was found that the features and shapes of the detached shock depended on sweep angle.When sweep angle<50°,the detached shock appeared as the form of trailing shock,and the supersonic jet with its reflection could be observed.The detached shock would be curved for the 50°and 60°fins and became a transmitted shock.The Scale-Invariant Feature Transform(SIFT)was successfully applied to obtain the velocity field from NPLS images,and the extent of the separated region was found to decrease with increasing sweep angle.No separation appeared as sweep angle>30°.Two peak values were detected on the centerline pressure distribution.The first peak did not rely on sweep angle,while the second peak value decreased with increasing sweep angle.
基金Acknowledgements The authors acknowledge the support from the Key National Natural Science Foundation of China （No. 91116009 ＆ No. 91216114）. The support provided by the FD-20 wind tunnel staff is greatly appreciated.
文摘An experimental study was conducted on the interactions of shock wave/turbulence or laminar boundary layer caused by fin-type protuberance, as the lack of detailed understanding of fluctuating pressure loads inside and outside the laminar or turbulence boundary layer separation region in hypersonic flow. The changes of fluctuating pressure in separation region were focused on in this paper. The study shows that the existence of fin changes flowfiled on the plate significantly. The laminar boundary layer separation occurs earlier and the separation region is more extensive. Similar flow is observed between a couple of measurement points outside the laminar separation region. However, there are significant differences between the flow inside and outside the separation region. The level of fluctuating pressure of laminar boundary layer is smaller than that in turbulent case. Even so, in laminar case, the peak fluctuating pressure still reaches a high level. Therefore, the structural influence （damage and/or early fatigue） of fluctuating pressure loads caused by the laminar boundary layer separation should not be ignored.
