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THREE-DIMENSIONAL TURBULENT VELOCITY FLUCTUATION MEASUREMENTS USING MAGNETIC RESONANCE IMAGING

Christopher J. Elkins
Department of Mechanical Engineering Stanford University 488 Escondido Mall Stanford, California 94305

Marcus Alley
Department of Radiology Stanford University Stanford, CA 94305, USA

Lars R. Saetran
Department of Mechanics, Thermo and Fluid Dynamics Norwegian University of Science and Technology N-7034 Trondheim, Norway

John K. Eaton
Dept. of Mechanical Engineering Stanford University 488 Panama Mall Stanford, CA 94305 USA

Abstract

Experimental measurements made using Magnetic Resonance Velocimetry (MRV), a technique based on Magnetic Resonance Imaging (MRI) principles, are presented for the 3D velocity field in the turbulent flow downstream of a backward facing step in a square channel with a Reynolds number of 48,000 based on the step height and the freestream velocity at the step edge. Results include the three-component mean velocity field measured using phase-contrast MRI methods and turbulent Reynolds stresses measured using a method based on diffusion imaging principles. MRV results are compared to particle image velocimetry (PIV) measurements made in the centerplane of the flow at several locations downstream of the step. The MRV and PIV mean velocity measurements show excellent agreement in all regions of the flow. The MRV measurements for the Reynolds normal stresses are in agreement with the PIV to within +/-20%.