Abstract:
Unsteady boundary layer development over a flat plate under the influence of wake
vortices induced from a rotating circular cylinder has been investigated by numerical
computations. The ratio of peripheral speed of the rotating cylinder to the free stream
velocity, a is varied from 0.5 to 1.75 keeping the rotating cylinder positioned at
different locations from the plate. The unsteady two-dimensional flow is simulated
numerically using finite element formulation. Quadratic triangular elements and
discontinuous linear triangular elements are used for velocity and pressure
interpolation respectively. A finite element package FEMLAB is used for the present
computation. Investigations are carried out for low Reynolds number based on
cylinder diameter and undisturbed free stream velocity in the range of 200 to 800.
Initial development of the flow field up to certain time period is considered.
Instantaneous streamlines of the disturbed flow field, instantaneous velocity field,
instantaneous boundary layer integral parameters, and skin friction are presented on
different streamwise locations. The location of the onset of transition is also
identified. The wake vortices strongly affect the boundary layer development
compared to undisturbed flow over flat plate. The computational results showed two
types of interactions, one is the strong wake-boundary layer interaction and another
being the weak wake-boundary layer depending on the speed ratio, a and the cylinder
to plate relative positions. Comparisons are also shown between the parameters
. obtained for the rotating cylinder to those of the stationary cylinder.
