并列双方柱在偏向流流态下的气动性能

Aerodynamic Characteristics of Two Side-by-side Square Cylinders in Biased Flow Regime

小间距并列双方柱存在独特的偏向流现象,为了进一步揭示并列双方柱在偏向流流态下的气动性能,在雷诺数(Re)为8.0×104、间距比(T/B,其中T为方柱中心间距,B为方柱边长)范围为1.25~5条件下,通过测压风洞试验方法研究了并列双方柱的表面风压、气动力、Strouhal数等气动参数随间距比的变化规律,重点探讨了发生偏向流现象时气动力的时频特性和气动力展向相关性.并列双方柱的偏向流现象主要发生在T/B=1.25~2的范围内,气流的偏转方向具有随机性,这一现象会随间距比的增大而逐渐消失;发生偏向流现象时,两个方柱的平均阻力系数、脉动风压系数均小于单方柱,但两个方柱间隙侧壁面受到的负压远强于单方柱;与宽尾流方柱相比,窄尾流方柱的平均阻力系数更大,脉动气动力系数更大,间隙侧壁面受到平均负压更强,气动力系数沿方柱展向的相关性更强.

The biased flow occurs when two side-by-side square cylinders are closely arranged.Wind tunnel tests are performed to investigate the aerodynamic characteristics of two side-by-side square cylinders in the biased flow regime.The Reynolds number Re is 8.0×10~4 and the spacing ratio T/B is in the range of 1.25~5,where T is the central spacing and B is the breath of a square cylinder.The variations of surface pressure coefficients,aerodynamic forces,and Strouhal number with spacing ratio are studied through the lateral wind tunnel tests.With respect to the biased flow regime,the temporal characteristics,spectral characteristics,and spanwise correlation of the aerodynamic forces are significantly discussed.The biased flow phenomenon mainly occurs in the range of T/B=1.25~2,its direction is random and it disappears with the increase of spacing ratio.In the biased flow regime,the mean drag coefficients and fluctuating pressure coefficients of both cylinders are smaller than that of a single square cylinder,while the negative pressure on the gap-side surfaces of two cylinders is stronger than that on the side of a single square cylinder.Compared to the cylinder with a wider wake,the square cylinder with a narrower wake is characterized by stronger mean drag,fluctuating forces,gap-side negative pressure,and spanwise correlation of aerodynamic forces.