Vortex-Induced Vibration of a Circular Cylinder With Low Mass Ratio Near a Plane Wall

Vortex induced vibration of a circular cylinder with low mass ratio in vicinity of a wall boundary is investigated experimentally in a water tunnel facility. Simultaneous measurements of the flow field via planar Particle Image Velocimetry and amplitude response have been carried out across a wide range of reduced velocities and cylinder-wall gap ratios (S* = S/D). For S* ≥ 3, both the amplitude response and the wake development are not significantly affected by the presence of the wall boundary. As S* is decreased below 3, the amplitude response decreases until S* ≈ 0.5, where the cylinder begins to periodically impact the wall. For all S* ≤ 0.5, the cylinder continues to impact the wall in a periodic fashion, and the reduced velocity range over which this occurs increases. Mean field and RMS field statistics revealed strong asymmetric wake development for S* < 3. Proper Orthogonal Decomposition of the velocity data was used to investigate the energy distribution in the coherent wake structures, and to filter the incoherent fluctuations via construction of a Reduced Order Model. Reconstructions of instantaneous vorticity fields obtained from the ROM illustrate the changes in vortex shedding patterns with the cylinder response.