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Flow Control scaling

Flow Control scaling. Yoshi Kubota. Outline . What is the flow control? Introduction of the flow control Objectives Reynolds stress Production, reduction of the Reynolds shear stress Effect of flow control Summary. Make more efficient. Satisfy the desire. More convenient our life.

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Flow Control scaling

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  1. Flow Control scaling Yoshi Kubota

  2. Outline • What is the flow control? • Introduction of the flow control • Objectives • Reynolds stress • Production, reduction of the Reynolds shear stress • Effect of flow control • Summary

  3. Make more efficient Satisfy the desire More convenient our life Why we should do flow control? • Drag reduction • Thrust producing • Fluid noise reduction • etc….

  4. Optimal control Feedback Steady & pulsed mass injection SPL level feedback Oscillating fences, flaps Reactive Dynamical system Active Feedforward Physical model Flow control strategy Preditermined Passive Fences Spoilers Passive mass injection Cylinders and rods Adaptive What is flow control? [1] Gad-el-Hak, M.: Modern developments in flow control, Appl. Mech. Rev., 49 (1996) 365-379.

  5. Objectives • What is the concept of flow control? • What is the effect of flow control? • Relation of scale, Reynolds stress with flow control

  6. Mean flow equation Reynolds stress term Reynolds stress continue equation Reynolds stress tensor Reynolds decomposition

  7. Production and diffusion of Reynolds shear stress in near-wall • Low pressure region correspond the core of streamwise vortex • High pressure region generate by streamwise vortex work • Reynolds shear stress product by vortex work • Reduction of wall friction drag, production of Reynolds stress and TKE can control by streamwise vortex. [2] Kasagi, N., Sumitani, Y., Suzuki, Y. and Iida, O.: Kinematics of the quasi-coherent vortical structure in near-wall turbulence, Int. J. Heat Fluid Flow, 16 (1995) 2-10.

  8. Conceptual diagram of energy flow • Conceptual diagram of energy flow between the near-wall vortices and the large-scale outer-layer structures • Streamwise vortex product near wall and transport to outer low speed region by large scale vortex [5] Iwamoto, K., Kasagi, N. and Suzuki, Y.: Dynamical Roles of Large-Scale Structures in Turbulent Channel Flow, Proc. Computational Mechanics, WCCM VI in conjunction with APCOM'04, Sept. 5-10, 2004, Beijing, China (2004) MS022-174.

  9. Reynolds number effect by stream wise vortex scale • Many of turbulent flow has very small length and time scale streamwise vortex. [3] N.Kasagi, Y.Suzuki and K.Fukagata.: Turbulent Flow control Pality, 18:2 (2003) 20-26

  10. Effect of flow control by DNS • Reynolds shear stress in channel flow at Re = 650 with damping in the near-wall layer • Effect of flow control is clearly at inside of controlled area • Also, effect is clearly at outside of controlled area [5] Iwamoto, K., Kasagi, N. and Suzuki, Y.: Dynamical Roles of Large-Scale Structures in Turbulent Channel Flow, Proc. Computational Mechanics, WCCM VI in conjunction with APCOM'04, Sept. 5-10, 2004, Beijing, China (2004) MS022-174.

  11. High Low uncontrolled controlled Example result of flow control • Cross-sectional view of instantaneous streamwise velocity in channel flow • Structure size is uncontrolled < controlled in outer region. • Flow control is effective in outer region. • Reynolds shear stress reduce at outer region [4] N.Kasagi.: Feedback Control of Turbulent Wall Shear Flow, Nagare 25 (2006) 13-22

  12. Summary • Show the concept and effect of flow control • Show the relation between Reynolds stress with flow control

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