Experimental and computational investigation of the two-dimensional channel flow over two fences in tandem

Measurements and computations of the mean streamwise velocity and its fluctuations are reported for an arrangement of two similar fences mounted in tandem in fully developed channel flow. The influence of Reynolds number and blockage ratio, in terms of the size and location of the primary and secondary recirculation zones, were investigated. The flow field around each fence was found to be similar to one another as well as to the corresponding single fence flow, for Reynolds numbers (based on the fence height) of up to 100. For higher Reynolds numbers, the shear layer developing from the first fence was significantly disturbed by the second fence resulting in earlier transition and higher turbulence intensities. This effect was most evident in the measured differences of the recirculation lengths downstream of each fence.