摘要
通过风洞实验研究了均匀流与湍流边界层中一端固定于壁面、另一端为自由端的有限长正方形棱柱气动力特性。实验模型宽度d=200 mm,高宽比H/d=5。基于自由流风速U_∞与d的雷诺数Re_d=0.68×10~5~5.47×10~5。研究发现,均匀流与湍流边界内有限长正方形柱气动力均不存在明显的雷诺数效应。棱柱局部时均阻力系数C_D、脉动阻力系数C＇_D和脉动升力系数C＇_L沿展向存在明显差异。湍流边界层会增大C＇_D与C＇_L。且均匀流中脉动风压与气动力的双稳态现象在湍流边界层内基本消失。经POD分析,确定了对称与反对称等两种典型风压分布状态对脉动风压的贡献率。均匀流中,柱体两端附近风压脉动由对称或准对称风压分布所控制;而柱体中部则由反对称风压分布控制。湍流边界层中所有高度风压脉动均由反对称风压分布控制。两种边界条件下,仅反对称形态的POD模态具有明显周期性并对柱体气动力周期性起支配作用。尽管对称风压POD模态在某些位置占支配地位,但其无明显周期性。
The effects of boundary layer conditions on aerodynamic forces of a finite-length square prism were experimentally investigated in a wind tunnel. The width of the tested model d = 200 mm,and the aspect ratio H / d = 5.The tested Reynolds number based on oncoming flow velocity（ U_∞） and d had a range of 0. 68 × 10~5 to 5. 47 × 10~5. It was found that Reynolds number has no obvious effects on aerodynamic forces of the finite-length square prism in both uniform flow and turbulent boundary layer; the local aerodynamic forces coefficients C_D,C＇_Dand C＇_L are significantly different along the prism span; both C＇_D and C＇_L remarkably increase in turbulence boundary layer relative to those in uniform flow; the bi-stable phenomena of the fluctuating pressure and aerodynamic forces observed in uniform flow disappear basically in turbulent boundary layer; contributions of the symmetrical and asymmetrical wind pressure distribution modes to the pressure fluctuation are determined based on POD analysis; in uniform flow,pressure fluctuations near both ends of the cylinder are controlled by the symmetrical wind pressure distribution,while that at the cylinder midspan is controlled by the asymmetrical wind pressure distribution; in turbulent boundary layer,asymmetrical pressure distribution controls all wind pressure fluctuations along the height; under both boundary layer conditions,only the asymmetrical POD mode has an obvious periodicity that determines the periodicity of aerodynamic forces,no obvious periodicity is observed for the symmetrical POD mode though it is dominant at some positions.
出处
《振动与冲击》
EI
CSCD
北大核心
2016年第5期39-46,共8页
Journal of Vibration and Shock
基金
国家自然科学基金资助项目(11472312
51108468)
关键词
有限长棱柱
气动力
边界层条件
双稳态
POD
finite-length prism
aerodynamic forces
boundary layer conditions
bi-stable phenomenon
POD
