Flow control around a circular cylinder by internal acoustic excitation

• Published in: Journal of fluids and structures Vol. 17; no. 7; pp. 903 - 913
• Main Authors: Fujisawa, N., Takeda, G.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01-06-2003; Elsevier
• Subjects: Exact sciences and technology; Flow control; Fluid dynamics; Fundamental areas of phenomenology (including applications); Instrumentation for fluid dynamics; Physics; Rotational flow and vorticity; Separated flows; Vortex shedding; Wind tunnel test; Instrumentation; Velocity distribution; Experimental study; Drag reduction; Flow control; Wakes; Circular cylinder; Particle image velocimetry; Vortex flow; Pressure measurement; Acoustic waves
• ISSN: 0889-9746; 1095-8622
• DOI: 10.1016/S0889-9746(03)00043-4

The possible drag reduction and the corresponding variation of the flow field around a circular cylinder are studied in a wind tunnel using flow control with acoustic excitation, which is supplied internally through a slit to the flow over the cylinder. The drag and the lift force acting on the cylinder are evaluated from the measurement of pressure distributions over the cylinder. The results indicate that the drag is reduced about 30% in comparison with a stationary cylinder, when the control parameters are optimized, such as the slit angle, the forcing Strouhal number and the excitation amplitude. The corresponding flow field around the cylinder with and without control is measured by particle image velocimetry. It is found that the wake of the circular cylinder is elongated downstream and the streamwise mean velocity is accelerated on both sides of the cylinder by the influence of acoustic excitation. On the contrary, the velocity fluctuations and the Reynolds stress in the near wake of the cylinder are strongly diminished under acoustic excitation. These variations of the wake flow support the drag reduction observed in the present measurements.