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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Experimental study of the near wake of a circular cylinder and its detached shear layers
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Experimental study of the near wake of a circular cylinder and its detached shear layers

机译：圆筒近尾及其分离剪切层的实验研究

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The near wake of a cylinder (x < 1.6D) and its detached shear layers are studied at Re = 3.5 x 1(0)4 through phase averaging of 2D-PIV snapshots using as trigger the pressure at phi = 90 degrees. The shedding cycle is examined at 8 time instants as well as at 16 time instants based on POD analysis. In the shear layer region, the flow becomes fully turbulent at x similar to 0.45D according to the momentum thickness spatial variation, whereas based on the velocity profile shapes there is a transition from convective to absolute type of instabilities at the same x station. The Karman vortices once formed at (0.8D, +/- 0.5D),accelerate streamwise towards the wake centre line following curved trajectories with speeds much smaller than those at the distant field. The Reynolds stresses and the turbulent kinetic energy production of each phase exhibit peaks downstream of the vortex centres in contrast to the spanwise vorticity, swirling strength and turbulent kinetic energy which maximize at the vortex centres, seen from a moving frame of reference. In the wake, normally <(v)over bar>'(2) > (u) over bar'(2) in contrast to the shear layer region in which (u) over bar'(2) > (v) over bar'(2). The Reynolds shear (u) over bar 'v being the smallest of the Reynolds stresses in the wake, shows two peaks of opposite sign, one being close to the vortex. The pressure at phi = 90 degrees (which might be related to the lift applied on the cylinder) takes its peak values with a time delay after the Karman vortex formation and particularly when the latter passes through x similar to 1.05D, its fluctuations being high or low according to the size of the vortex.
机译：在Re = 3.5×1（0）4通过PHI = 90度的压力触发压力，在RE = 3.5×1（0）4上通过相位平均来研究圆柱（x <1.6d）及其分离的剪切层的近尾。在8次时刻以及基于POD分析的16次时刻检查脱落周期。在剪切层区域中，根据动量厚度空间变化，流动在X处变得完全湍流，而基于速度曲线形状，在相同的X站的情况下，存在从对流到绝对类型的不稳定性的转变。在（0.8D，+/- 0.5d）上形成的Karman涡旋，在弯曲的轨迹之后将朝向唤醒中心线加速，速度远小于远距离场的速度。与涡旋中心下游的每个相表现出涡旋中心下游的峰值峰值，与涡旋中心最大化的涡旋强度和湍流动能最大化，从移动框架中最大化。在唤醒中，通常与条形>'（2）>（U）相反，与剪切层区域相比，其中（U）上方（2）>（V）上方的条形'（2）。雷诺斯剪切（U）在尾术中是最小的雷诺胁迫，显示了两个相反的符号的峰，一个接近涡流。 PHI = 90度（它可能与施加在汽缸上的升程有关的压力）在Karman涡流形成后的时间延迟，特别是当后者通过x类似于1.05d时，其波动高或根据涡旋的大小而低。

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