Near wake models for the hydrodynamics forces on a cylinder in periodic flow
- Univ. of Texas, Austin, TX (United States)
- Univ. of Virginia, Charlottesville, VA (United States). School of Engineering and Applied Science
The relationship between hydrodynamic forces and the reversing near wake flow field around a cylinder in oscillatory farfield flow was experimentally investigated. A computer controlled pressurized water tunnel was employed to generate a planar harmonic flow past a stationary cylinder of Keulegan-Carpenter numbers (KC) in the inertia-drag flow regime and at subcritical Reynolds numbers (Re). Streamwise (u-) and cross-stream (v-) velocities near the cylinder and u-velocities at the far flow field were measured using a three-component LDV system. Inline and lift forces on the cylinder were measured using a very sensitive six-component load cell. A modal phase averaging technique was applied to the velocity data to estimate averaged velocity cycles that distinguish between positive and negative flow modes. A positive (negative) flow mode signifies dominant vortex shedding and motion occurring from the top (bottom) of the cylinder, respectively. The force measurements were likewise phase averaged into positive and negative mode force cycles. u- and v-velocity profiles for KC = 10, 15, and 20, based on modal phase averages of velocity measurements, were used to estimate averaged wake u- and v-velocities. These wake velocities were used in the place of the undisturbed farfield u-velocity as inputs to Morison`s equation for the inline force, and to the quasi-steady model for the lift force. It was found that, for KC = 15 a significant improvement in the prediction of lift force was achieved using the wake-based lift force model, whereas a smaller improvement in the inline force prediction was obtained from the wake-based Morison`s equation.
- OSTI ID:
- 182725
- Report Number(s):
- CONF-950695--; ISBN 0-7918-1306-1
- Country of Publication:
- United States
- Language:
- English
Similar Records
Flow mapping of the reversing vortex wake of a cylinder in planar harmonic flow
Experimental/numerical mapping and analysis of the nearfield flow around a cylinder in planar oscillatory farfield flow