Fluctuation Mitigation for Ship at Yaw Using Streamwise Suction Active Flow Control

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Abstract
The control of a ship’s airflow is especially tricky under yaw effects. This paper numerically studies the streamwise suction (SS) active flow control (AFC) on the Chalmers ship model (CSM) for suppressing force fluctuations on the ship body and turbulent fluctuations in the wake region. There are two yaw angles of interest, which are 15 and 45 deg, typically representing mild and severe yaw effects. The SS AFC is implemented immediately downstream of the sharp-edged front surface as inspired by prior studies in suction control. Beyond achieving effective mitigation of fluctuations, the goal here is to understand the flow control mechanism by analyzing flow characteristics and vortical activities. A large-eddy simulation with a wall-adapting local-eddy viscosity model is conducted and is complemented by experimental tests for validation. Two cases are studied at each yaw condition: the baseline CSM without control and the AFC case with SS activated along the leading edges (LEs) of the roof and of the leeward superstructure surfaces. Results show that full-flow attachments are achieved downstream of the suction slots, regardless of the sharp superstructure LEs. The airwake vortex structure and vortex dynamics are altered substantially, leading to the reduction of drag and side-force fluctuations. Turbulent fluctuation is also effectively suppressed at both yaw conditions, which can benefit maritime helicopter operations. As indicated by the proper orthogonal decomposition analysis, the suppression mechanism differs between the two cases, where the 15 deg case links to the weakening of shedding activities and the 45 deg case results from limiting vortex–vortex interactions.
Funding Information
  • National Academic Infrastructure for Supercomputing in Sweden
  • University of Maine
  • Chalmers Tekniska Högskola

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