Sattarzadeh Sohrab S, Fransson Jens H M, Talamelli Alessandro, Fallenius Bengt E G
Linné Flow Centre, KTH Royal Institue of Technology, SE-10044 Stockholm, Sweden.
Linné Flow Centre, KTH Royal Institue of Technology, SE-10044 Stockholm, Sweden and Dipartimento Ingegneria delle Construzioni Meccaniche, Alma Mater Studiorum, Università di Bologna, I-47100 Forlì, Italy.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Jun;89(6):061001. doi: 10.1103/PhysRevE.89.061001. Epub 2014 Jun 17.
Miniature vortex generators (MVGs) are able to delay the transition to turbulence in a flat plate boundary layer if properly designed. Unfortunately, the natural recovery of the modulated laminar base flow in the streamwise direction is of exponential space scale and hence the passive laminar control fades away fairly rapidly. Here we show that by placing a second array of MVGs downstream of the first one it is possible to nourish the counter-rotating streamwise vortices responsible for the modulation, which results in a prolonged streamwise extent of the control. With this control strategy it is possible to delay the transition to turbulence, consecutively, by reinforcing the control effect and with the ultimate implication of obtaining a net skin-friction drag reduction of at least 65%.
微型涡流发生器（MVG）如果设计得当，能够延迟平板边界层中向湍流的转变。不幸的是，调制层流基流在流向的自然恢复具有指数空间尺度，因此被动层流控制会相当迅速地消失。在此我们表明，通过在第一个MVG阵列的下游放置第二个MVG阵列，可以滋养负责调制的反向旋转流向涡旋，这导致控制在流向的范围延长。采用这种控制策略，可以通过增强控制效果连续延迟向湍流的转变，最终意味着获得至少65%的净表面摩擦阻力降低。
