在北京航空学院水槽中,用氢泡法对绕凹半球模型流动进行了研究。模型前后流速分布是用氢泡时间线测量的,它与在起动开始时由无旋流理论估算值接近,但当起动旋涡变大以后,在尾流中流速差别变大。在模型后部诱导出较大的反流速席。所以由无旋估计的虚质量只在开始时是可用的,并且在起动涡变大时,虚质量应更大。 在定常流中,在模型前有时形成一个大旋涡,这个旋涡是非定常的并且可能引起侧向力和伞的非定常运动。模型上适当开孔可减小甚至消除此旋涡。 In the Beijing Institute of Aeronautics in the sink, the bubble hemisphere hemisphere model was studied. The velocity distribution before and after the model was measured by the bubble time line and approximated by the theory of no-swirl theory at the start of the start-up. However, when the start-up vortices became larger, the velocity difference in the wake became larger. The back of the model induced a larger backfill. Therefore, the imaginary mass estimated by the non-rotation is only available at the beginning, and the virtual mass should be larger when the starting vortex becomes larger. In steady flow, a large vortex sometimes forms in front of the model, which is unsteady and can cause lateral forces and unsteady movement of the umbrella. Appropriate openings in the model reduce or eliminate this vortex.