Scaling of the elastic regime in turbulent flow with polymer additives*

We present an experimental study of the effect of polymer additives on the turbulent energy cascade in Von Karman swirling (VKS) system. The three components of the velocity at the center of the VKS in a vertical plane along a diameter of the system are measured by stereoscopic Particle Image Velocimetry (PIV) in pure water (Newtownian) case and polymer solution case. It is found that the inertial range of the velocity structure function is “truncated” at the smaller scale due to the addition of the polymer additives. At scales less that the “truncation scale”, the second order structure function exhibits a new scaling with exponent around 1.38. This new scaling range is dominated by polymer’s elasticity and its range is extending with increasing polymer concentration. The three regimes (dissipation, elastic and inertial ranges) can be well described by the modified Batchelor’s parametrization. With this parametrization, we successfully determined the “truncation scale”. Scaling exponents of high order velocity structure functions are also presented.