Experimental investigation of wall-bounded turbulence drag reduction by active control of double piezoelectric vibrator
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Experimental investigation on wall-bounded turbulence drag reduction by double piezoelectric vibrator active control*
Jian-xia Bai 1, 2, Yong-xiang Huang 3, Nan Jiang 1, 4, Xing-yu Ma 1, 4, Zhan-qi Tang 1, 4 1. Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300354, China 2. Department of Mathematics, Tianjin University Renai College, Tianjin 301636, China 3. State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China 4. Tianjin Key Laboratory of Modern Engineering Mechanics, Tianjin 300354, China (Received May 24, 2019, Revised September 3, 2019, Accepted September 15, 2019, Published online April 7, 2020) ©China Ship Scientific Research Center 2020 Abstract: In order to manipulate large-scale coherent structures in the wall-bounded turbulence and reduce the skin-friction, an active-control experimental investigation was performed through synchronous and asynchronous vibrations of double piezoelectric vibrators embedded spanwisely on a smooth flat plate surface. A TSI-IFA300 hot-wire anemometer and TSI-1621A-T1.5 hot-wire probe were used to measure the time series of instantaneous velocity at different locations. Influence of the vibrations on wall-bounded turbulence are compared in a multi-scale point of view. A disturbance Reynolds Number Red d f is introduced to represent the disturbance. A probability density functions (PDFs) of the multi-scale components of the turbulence velocity and multi-scale conditional phase-averaged waveform are studied in detail using the Wavelet transform. The results show that the maximum drag reduction rate 18.54% was obtained at 100V/160Hz and Red 0.54 case with an asynchronous vibration mode. The disturbances generated by the vibrators have a significant influence on the sweep events of burst. The asynchronous vibration model is more effective than synchronous vibration one. A possible physical mechanism is recognized to explain why the disturbance frequency of 160Hz leads to an optimal parameter set for drag reduction. 2
Key words: Wall-bounded turbulence, active control, drag reduction, piezoelectric vibrator, multi-scale analysis, conditional phase-averaged waveforms, coherent structure
Introduction Wall-bounded turbulence contributes the most part of the frictional drag for vehicles and causes a large amount of fuel consumption and environment pollution. For instance, for a modern commercial aircraft, the skin friction contributes more than 50% of drag [1]. It has been widely accepted that large-scale coherent structures are the key structures in generation and maintaining of wall-bounded turbulence [2-4]. Hence, the control of wall-bounded turbulence and drag reduction should begin with and focus on the * Project supported by the National Natural Science Foundation of China (Grant Nos. 11732010 ， 11972251 ， 11872272，11902218，11802195) Biography: Jian-xia Bai (1982- ), Female, Ph. D., E-mail: [email protected] Corresponding author: Nan Jiang, E-mail: nanj
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