矩形断面抖振阻力空间分布特性试验研究

为了研究紊流作用下钝体抖振阻力的空间分布特性及流固相互作用机理，以2：1矩形断面为例，通过刚性模型测压试验研究了抖振阻力的跨向相关性及空间能量分布特性。结果表明，当紊流积分尺度与钝体特征尺寸相当时，抖振阻力的相关性高于纵向脉动风，这也许是由漩涡沿展向发生拉伸引起。而在分离点附近，来流漩涡会发生剧烈畸变，顺流向大尺度漩涡会破碎成小尺度漩涡，在此过程中能量由低频向高频的转移，并导致脉动压力的跨向相关性也会有所减弱。与迎风侧不同，背风侧脉动压力主要受钝体尾流中的紊流成分影响，其漩涡沿跨向拉伸程度可能要高于迎风侧，以致背风侧脉动压力的跨向相关性强于迎风侧。顺流向分离涡在由分离点向中部运动过程中，其高频的小尺度漩涡可能并没沿顺流向拉伸，而是直接耗散，从而导致脉动压力谱在低频保持不变，而在高频区下降。

EXPERIMENTAL INVESTIGATION OF THE SPATIAL DISTRIBUTION OF BUFFETING DRAG ON BLUFF BODY WITH RECTANGULAR CROSS-SECTION

In order to study the spatial distribution of buffeting drag on bluff bodies and the mechanism of flow-structure interaction, the span-wise correlation and the energy distribution of buffeting drag on stationary rectangular cylinder with side ratio B/D=2 were investigated by synchronically surface pressure measurement. The results show that the buffeting drag is more correlated than the longitudinal turbulent component when oncoming flow approaches the windward side of the cylinder, which may be accounted for the stretch of the vortices in the turbulence along the span. Meanwhile, the vortices will be distorted at separation point. The large scale coherent vortices are contaminated by small eddies, which would attenuate the span-wise correlation of the fluctuating pressures. In addition, the energy will be transferred from lower frequency to higher frequency when the longitudinal large scale vortices break into smaller eddies at the separation point. The experiments also indicate that the fluctuating pressures on the leeward side are mainly determined by the signature turbulence generated by the bluff body. It is inferred that the shedding vortices on the leeward side are stretched larger than the ones on the windward side along the span, which may causes larger span-wise correlation of surface pressures on the leeward side. Contrary to the longitudinal energy transition pattern, small scale eddies with higher frequency are possibly not stretched longitudinally but dissipated when the separation bubble moves from the separation point to mid part of the leeward side. Thus, the spectra of fluctuating pressures keep constant at lower frequency and decrease at higher frequency.