The turbulent boundary layer control on NACA 0012 airfoil with Mach number ranging from 0.3 to 0.5 by a spanwise array of dielectric barrier discharge (DBD) plasma actuators by hot-film sensor technology is investigated. Due to temperature change mainly caused through heat produced along with plasma will lead to measurement error of shear stress measured by hot-film sensor, the correction method that takes account of the change measured by another sensor is used and works well. In order to achieve the value of shear stress change, we combine computational fluid dynamics computation with experiment to calibrate the hot-film sensor. To test the stability of the hot-film sensor, seven repeated measurements of shear stress at Ma = 0.3 are conducted and show that confidence interval of hot-film sensor measurement is from −0.18 to 0.18 Pa and the root mean square is 0.11 Pa giving a relative error 0.5% over all Mach numbers in this experiment. The research on the turbulent boundary layer control with DBD plasma actuators demonstrates that the control makes shear stress increase by about 6% over the three Mach numbers, which is thought to be reliable through comparing it with the relative error 0.5%, and the value is hardly affected by burst frequency and excitation voltage.
It is a very difficult task to develop a method of reducing turbulent boundary layer drag. However, in recent years, plasma flow control technology has demonstrated huge potential in friction drag reduction. To further investigate this issue, a smooth plate model was designed as a testing object arranged with a bidirectional dielectric-barrier-discharge (DBD) plasma actuator. In addition, measurement of skin friction drag was achieved by applying hot wire anemometry to obtain the velocity distribution of the turbulent boundary layer. A method of quantifying the friction drag effect was adopted based on the Spalding formula fitted with the experiment data. When plasma actuation was conducted, a velocity defect occurred at the two measuring positions, compared with the no plasma control condition; this means that the DBD plasma actuation could reduce the drag successfully in the downstream of the actuator. Moreover, drag reduction caused by backward actuation was slightly more efficient than that caused by forward actuation. With an increasing distance from plasma actuation, the drag-reduction effect could become weaker. Experimental results also show that the improvement of drag-reduction efficiency using a DBD plasma actuator can achieve about 8.78% in the local region of the experimental flat model.
This paper studies the turbulent drag reduction (TDR) effectiveness of a flat-plate model using a series of slot blowing pulsed plasma actuator (SBP-PA) with a type of spanwise layout. Wind tunnel experiments are carried out under a Reynolds number of 1.445×104. Using a hot-wire anemometer and an electrical data acquisition system, the influences of millisecond pulsed plasma actuation with different burst frequencies and duty cycles on the microscale coherent structures near the wall of the turbulent boundary layer (TBL) have been studied. The experimental results show that the slot blowing pulsed plasma actuator can effectively reduce the TBL frictional drag. When the duty cycle exceeds 30%, the TDR rate is greater than 11%, and the optimal drag reduction rate of 13.69% is obtained at a duty cycle of 50%. Furthermore, optimizing the electrical parameters reveals that increasing the burst frequency significantly reduces the velocity distribution in the logarithmic region of the TBL. When the normalized burst frequency reaches f+=2πfpd/U∞=7.196, the optimal TDR effectiveness is 16.97%, indicating a resonance phenomenon between the pulsed plasma actuation and the microscale coherent structures near the wall. Therefore, reasonably selecting the electrical parameters of the plasma actuator is expected to significantly improve the TDR effect.
Poiseuille–Rayleigh–Bénard (PRB) flow has been observed in nature as well as many industrial applications. Enhancing the rate of heat transfer of PRB flow has long been a subject of interest in the relevant research. This study proposed a novelty non-intrusive method to control PRB flow through numerical simulations by using jets generated by nine groups of alternating-current dielectric-barrier-discharge (AC-DBD) plasma actuators arranged in the spanwise direction. We considered PRB flows ( Pr = 2/3) in air in channels with an aspect ratio equal to length/height = 20, with Reynolds numbers in the range of 10 ≤ Re ≤ 100 and a Rayleigh number of Ra = 10 000. The effect of plasma control on PRB flow was qualitatively and quantitatively analyzed. The results showed that at a low Reynolds number ( Re = 10, 20, 30), the jet generated by the plasma actuators promoted the plume on the wall to form stable transversal rolls and enhance mixed convection. At a high Reynolds number ( Re = 50, 100), the jet suppressed Poiseuille flow, promoted the rise in the flow of heat at the bottom wall, and enhanced the vertical temperature gradient. Moreover, steady DBD plasma actuation-based control significantly improved the coefficient of heat transfer of the flow, at times providing up to a tripling of transport compared to the unactuated case. The results here are useful for technological and industrial applications.
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