An Experimental Study of Vortex-Induced Vibrations of a Cylinder in Shear- and Extensional-Thinning Flows

We present experimental results of the response of a one-degree-of-freedom cylinder placed in shear- and extensional flows. A flexibility-mounted rigid cylinder is subjected to flow generated in a water channel. The thinning of the fluids is increased by increasing the concentration of Xanthan gum in water. For the low concentration fluids, the VIV response follows the response of a Newtonian fluid. As the concentration is increased, the lock-in range and the maximum amplitude of oscillations decrease until VIV is completely suppressed for the maximum concentration tested here within the range of Reynolds numbers considered in these experiments (Re<100). We discuss differences between these experiments and our previous numerical results on VIV of a cylinder in purely shear thinning fluids