A synthetic jet in crossflow creates a momentum deficit in the crossflow downstream of the jet. In the literature, this deficit is ascribed to viscous blockage by the jet and the upwash of low-momentum fluid caused by the vortical structures of the jet. This paper proposes a third effect contributing to the momentum deficit: a velocity induced by the vortical structures in the direction opposite to the crossflow. A reconstruction technique - quantifying the vortex-induced velocity - is developed to determine the momentum deficit caused by the proposed effect. This is applied to a test case of a rectangular synthetic jet (St - 0.5, r = 0.88) issuing into a turbulent boundary layer (Re_τ = 1220, U_∞ = 10 m/s, 5 - 45 mm). The streamwise and wall-normal velocity components are measured in the symmetry plane of the jet using two-dimensional two-component PIV. The momentum deficit created by the vortex-induced velocity is compared to the total measured momentum deficit. It is shown that the newly proposed effect accounts for approximately 65% of the measured in-plane momentum deficit, while not being mentioned in the known literature.
展开▼
机译：横流中的合成射流会在射流下游的横流中产生动量不足。在文献中，这种缺陷归因于射流的粘性阻塞以及由射流的旋涡结构引起的低动量流体的上冲。本文提出了造成动量不足的第三个影响：涡结构在与横流相反的方向上引起的速度。开发了一种量化涡旋感应速度的重建技术，以确定由所提出的效应引起的动量不足。这适用于将矩形合成射流（St-0.5，r = 0.88）喷入湍流边界层（Re_τ= 1220，U_∞= 10 m / s，5-45 mm）的测试案例。使用二维两分量PIV在射流的对称平面中测量流向和壁法向速度分量。将由涡流引起的速度产生的动量不足与总的测量动量不足进行比较。结果表明，新提出的效应约占所测平面内动量不足的65％，而在已知文献中并未提及。
展开▼
