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MECHANISM OF DISSIMILAR MOMENTUM AND HEAT TRANSFER INDUCED BY A TRAVELING WAVE-LIKE BLOWING/SUCTION IN TURBULENT CHANNEL FLOW

Yosuke Hasegawa
Institute of Industrial Science, The University of Tokyo, Komaba 4-6-1, Meguro-ku, Tokyo 153-8505, Japan; Center of Smart Interfaces Technical University Darmstadt Petersenstr. 32, 64287 Darmstadt, Germany

Nobuhide Kasagi
Center for Research and Development Strategy, Japan Science and Technology Agency; Department of Mechanical Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Аннотация

The suboptimal control theory is applied for achieving dissimilar control of enhancing heat transfer, while keeping the skin friction not increased considerably in a fully developed channel flow. The Frechet differentials clearly show that the responses of velocity and temperature fields to wall blowing/suction are quite different due to the fact that the velocity is a divergence-free vector while the temperature is a conservative scalar. This essential difference allows us to achieve dissimilar control even in flows where the averaged momentum and energy transport equations have the identical form. It is also found that the resultant optimized mode of control input exhibits a streamwise traveling wave-like property. By exploring the phase relationship between the traveling wave-like control input and the velocity and thermal fields, we reveal that such control input contributes to dissimilar heat transfer enhancement via two different mechanisms.