Predetermined control of turbulent boundary layer with a piezoelectric oscillator

Abstract

With a piezoelectric (PZT) oscillator, the predetermined controls of the turbulent boundary layer (TBL) are effective in reducing the drag force. The stream-wise velocities in the TBL are accurately measured downstream of the oscillator driven by an adjustable power source. The mean velocity profiles in the inner and outer scales are reported and the skin friction stresses with different voltage parameters are compared. Reduction of integral spatial scales in the inner region below y + of 30 suggests that the oscillator at work breaks up the near-wall stream-wise vortices responsible for high skin friction. For the TBL at Re θ of 2183, the controls with a frequency of 160 Hz are superior among our experiments and a relative drag reduction rate of 26.83% is exciting. Wavelet analyses provide a reason why the controls with this special frequency perform best.

Active control of multiscale features in wall-bounded turbulence

“…As a representative of the passive control methods, Wash and Choi et al [13][14][15] achieved considerable drag reduction on riblet surfaces by conducting experiments and direct numerical simulations. In comparison with the passive control method, the active control method has wider adaptability to complex flows, and it enhances the control effectiveness [16][17][18][19], which has been confirmed by several experimental and simulation investigations [20][21][22][23][24][25][26][27][28][29]. Bai et al [2] used a spanwisealigned array of piezoceramic actuators to generate a transverse traveling wave along the wall surface.…”

“…Berger et al [30] obtained a drag reduction of 40% via an open loop-controlled oscillating spanwise Lorentz force that disturbed the semi-equilibrium state between the near-wall streamwise vortices and the wall in channel flow. Zheng et al [19] applied a single PZT actuator to break the near-wall streamwise vortices and achieved a drag reduction of 27%. Herein, we employed an active strategy based on the aforementioned achievements.…”

Active Control for Wall Drag Reduction: Methods, Mechanisms and Performance

“…Zheng et al [146] studied the interference characteristics of micro vibration generated by cantilever piezoelectric actuator on the turbulent boundary layer, based on wind tunnel experiments, as shown in Fig.22. They obtained the average flow velocity and friction stress of the near-wall fluid when the piezoelectric actuator was loaded with different voltage amplitudes and frequencies, and obtained the drag reduction rate with the maximum value of 26.83%.…”

Local dynamic perturbation effects on amplitude modulation in turbulent boundary layer flow based on triple decomposition

“…A wall-mounted piezoelectric (PZT) actuator provides such a potential way to achieve the local wall deformation in TBL flows. [48][49][50] Zheng et al 49 utilized a single wall-mounted PZT actuator to disturb the streamwise vortices. They found that the most drag reduction is obtained when the oscillator frequency is matched with the wavelength of the near-wall coherent structures containing the most energy.…”

“…Experiments were conducted in a closed-circuit wind tunnel in Tianjin University, as described in previous studies. 42,44,49 The test section of the tunnel was 2.0 m long, 0.6 m tall, and 0.8 m wide, and a smooth boundary-layer plate was vertically fastened at the test section. Zero-pressure-gradient conditions were achieved by adjusting the inclination angle of the experimental plate.…”