A Description of the Available Position

This project is a continuation of efforts at the lab for the last several years to develop various techniques and methodology to prepare polymer solutions and to conduct precise measurements with goal to study turbulent drag reduction (TDR) as a function of polymer concentration and elasticity of polymer solutions. Meantime we finalized measurements of only global quantities, torque and pressure fluctuations, that are sufficient to characterize turbulence in swirling flow of Newtonian fluids as well as polymer solutions. On next step, more detailed characterization of fully developed turbulence and TDR should be conducted using conventional techniques, such as particle image velocimetry, laser Doppler velocimetry, and hot-wire velocity measurements as well as a new acoustic scattering method of direct measurements velocity and vorticity fields in spatial and temporal domains, developed at the lab. Since the acoustic scattering technique gives information about temporal dynamics of the spatial vorticity distribution, we will be able to measure the structure function of the vorticity, which provides rather complete information about its statistical properties. The measurements were performed with a detector array consisting of 64 elements, and the ability of the method was demonstrated on two types of turbulent flow: (i) von-Karman swirling flow between two co-rotating disks to characterize large scale vorticity (dynamics of a single vortex), and (ii) von-Karman swirling flow between counter-rotating disks to study small scale turbulence. This research requires rather good acquaintance with hydrodynamics, electronics and programming in Matlab.