Numerical study of the steady-state uniform flow
past a rotating cylinder
Results from the numerical simulation of the two-dimensional incompressible unsteady
Navier–Stokes equations for streaming flow past a rotating circular cylinder
are presented in this study. The numerical solution of the equations of motion is
conducted with a commercial computational fluid dynamics package which discretizes
the equations applying the control volume method. The numerical set-up is validated
by comparing results for a Reynolds number based on the free stream of Re = 200
and dimensionless peripheral speed of q˜ = 3, 4 and 5 with results from the literature.
After the validation stage, various pairs of Re and q˜ are specified in order to carry out
the numerical experiments. These values are Re = 200 with q˜ = 4 and 5; Re = 400
with q˜ = 4, 5 and 6, and Re = 1000 with q˜ = 3. In all these cases, gentle convergence
to fully developed steady state is reached. From the numerical vorticity distribution,
the position of the outer edge of the vortical region is determined as a function of the
angular coordinate. This position is found by means of a reasonable criterion set to
define the outmost curve around the cylinder where the vorticity magnitude reaches
a certain cut-off value. By considering the average value of this profile, a uniform
vortical region thickness is specified for every pair of Re and q˜.
Inviscid, Incompressible Flow Past Circular
Cylinders and Joukowski Airfoils
Considered steady, 2-D, inviscid, incompressible, adiabatic and irrotational flow,
also called potential flow. The influence of gravity will be neglected.
Lift of a Rotating Circular Cylinder in Unsteady Flows
A cylinder rotating in steady current experiences a lift known as the Magnus effect. In the present study, the effect of
waves on the Magnus effect has been investigated. This situation is experienced with the novel, floating offshore vertical
axis wind turbine (VAWT) concept called the DEEPWIND concept, which incorporates a rotating spar buoy and thereby
utilizes seawater as a roller bearing. The a priori assumption and the results suggest that the lift in waves, to a first
approximation, may be represented by a formulation similar to the well-known Morison formulation. The force coefficients
are experimentally found to depend primarily on the ratio between the surface speed of the cylinder and the outer flow
velocity.
QUESTION ANSWER
CFD_cylinder
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