Vortex wakes of oscillating rectangular prisms in Turbulent Flows

• Main Authors: Kao, chung-ren, 高忠人
• Other Authors: Po-Chien Lu
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/09240139905687398834

碩士 === 淡江大學 === 水資源及環境工程學系 === 84 === An experimental investigation was carried out to study the characteristics of the rectangular cylinders due to forced oscillation.The turbulence intensityand length scale of flow field were under control as the paramenters of experiments.to measure of the lateral pressure(Cp),base pressure(Cpb),lock-in range,pressure and wake velocity spectrum,vortex formation length,Andmeasurements of the phase angle between lateral pressure and body displacement. The results showed that the rapid phase angle change through vortex resonantproduced a large out-of-phase force component.The pressure coefficients are much higher in the lock-in range.The peak value of pressure coefficient take place at resonant frequency.High turbulence intensity will weaken the vortex shedding. The lateral pressure(-Cp)will reduce and the peak values of the pressure spectrum will be descreased,but when the depth-to-width ratio is less than 0.5 the base pressure(-Cpb) will be increase. The critical geometry can be obtained from the pressure coefficient. Increase of the turbulence intensity or forced oscillation rectangular cylinderswill cause the critical value to move to a low depth-to-width ratio.The cylinder oscillation will reduce the vortex formation length.