三棱柱绕流流场实验研究

(厦门大学航空航天学院,福建 厦门 361005)

粒子成像测速; 本征正交分解; 时间空间关联; 剪切层

Experimental Study on Flow Characteristics Around a Triangular Prism
QIU Yue,JIANG Jianhua,LIU Zhirong*)

(School of Aeronautics and Astronautics,Xiamen University,Xiamen 361005,China)

DOI: 10.6043/j.issn.0438-0479.201705032

备注

应用粒子成像测速(particle image velocimetry,PIV)技术对尺度比H为45°的三棱柱在不同雷诺数Re下的尾流场进行定量测量,结合本征正交分解法研究尾流场相干结构,同时利用时间空间关联法确定了不同雷诺数下涡街流向运输速率的变化情况.研究发现前二阶模态流场结构代表流场中卡门涡街结构,第三阶模态流场结构可表征尾流场中自由剪切层形态,且该形态对雷诺数相对敏感.Re=400工况下,三棱柱绕流流场中自由剪切层形态出现不稳定现象,抑制了自由来流与尾流区内流体间的动量交换,使得尾流区内流体恢复系数减弱,尾流场中阻力系数Cd突增.

Particle image velocimetry was used to quantitatively measure the wake field under different Reynolds numbers for triangular prisms with a scale ratio of 45°,and the coherent structure of the wake field was studied by using the proper orthogonal decomposition method.The time-space cross correlation method is used to determine the influence of the vortex streamwise transport rate on the Reynolds number.Analysis of coherent structures of the flow field using proper orthogonal decomposition method indicates that the last two order modes of flow structure are on behalf of the Karmen vortex structure,the third order mode structure could represent the free shear layer morphology which is sensitive to the Reynolds number.The free shear layer exhibits unsteady phenomenon with the condition of Reynolds number around 400,which retards the exchange of fluid between the free flow and the wake region,leading to a weakened fluid recovery coefficient and a sudden increase in the drag coefficient.

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