摘要
根据线性稳定性理论研究点源产生的波包在二维和三维不可压边界层中的传播特征 .发现点源波包在二维边界层中呈楔形向下游传播 ,其横向偏角为 1 0°,与相关的试验图片相吻合 .波包的最大幅值在点源附近区域偏离中心线 ,随着波包向下游传播 ,波包的三维性很快减小 ,最大幅值沿中心线增长 .同时发现波包的幅值放大因子远小于最不稳定单色波 .波包在后掠平板三维边界层的传播与二维不同 ,其波形基本不变 ,最大幅值的增长路径和势流的夹角变化很小 ,且幅值增长迅速 .证明流场显示观测到的条纹结构是波包的等位线 ,在三维边界层中应用 e N方法应沿着波包增长方向积分 .
The propagation of wave packet produced from a point source in two and three dimensional incompres sible boundary layer is investigated numerically on the basis of linear stability theory.It is found that in two dimensional case the wave packet propagates downstream in the wedge shape,the angle of the half wedge is 10° which is in good consistence with the experiment data.Near the source,the maximum amplitue occurs at spanwise locations away from the centerlines,but it approaches quickly to the centerline,than amplifies downstream along the centerlines and the three dimensionality gradually disappears.The amplification factor of the maximum amplitude of the wave packet is much smaller than the most unstable normal mode.In the three dimensional boundary layer of the swept flat plate the wane pattern changes slightly,the maximum amplitude amplifies quickly downstream along a path which has a almost unchangeable angle with the potential flow direction.It is proved that the streaks observed in the flow visualization are equivalent to the constant phase lines of wave packet;the e N method applied in 3D boundary layer should be evaluated in the direction along which the wave packet amplifies.
出处
《天津大学学报(自然科学与工程技术版)》
EI
CAS
CSCD
2000年第3期285-289,共5页
Journal of Tianjin University:Science and Technology
基金
国家自然科学基金资助课题! (19872 0 50 )