Experimental and computational study of flow over a rotating cylinder with surface roughnes
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Date
2016-03-01
Authors
Mohamad Tarmizi Abu Seman
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Abstract
Experimental and computational approaches are taken in this thesis, to understand
how rotation and surface roughness affects the dynamics of a cylinder in flow. The
roughness was simulated by attaching three types of sandpaper with various
roughness, to the cylinder surface. The experiment takes place in a wind tunnel,
applying a free stream velocity within the range from 0.65 to 13.21 m/s. The range of
average rough cylinder (Ra) is 5.0μm to 77.0μm and the range of rotation speeds of
up to 400 rev/m. The study focuses on calculating the lift and the drag forces using a
“Light Weight Smart Motor (LWSM)” and a rotating two-dimensional circular
cylinder. The cross-section of the test section for the open circuit wind tunnel is
300mm by 300mm. Apart from testing lift and drag forces, the flow behind the
rotating cylinder is measured, and images of vortices shedding are captured during
experimentation. A wide range of data is gathered by repeating the observations for
various Reynolds numbers. Furthermore, Computational Fluid Dynamics (CFD)
simulations verify vortex shedding and provide an indication of where to place the
experimental device, comprised of small obstacles, to achieve the best suppression of
vortex shedding. ANSYS FLUENT® commercial CFD software simulated the flows
with respect to rotation and surface roughness. A comparison of the simulation and
the experimental results shows close agreement, with approximately 10% variation.
For Re > 20000, the rotation has an extremely small effect on the overall forces
acting on the flow field around the cylinder with surface roughness.