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Research

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Fukagata et al. (2006)
1. Drag reduction and heat transfer enhancement in wall-turbulence

The skin friction drag in turbulent flow on a wall is significantly larger than the laminar flow at the same Reynolds number. This is a major cause of energy loss in the high-speed transportation such as high-speed trains, aircrafts, ships. In this study, we attempt to reduce such friction drag by using active control or passive control techniques. We also attempt to enhance heat transfer while keeping the friction drag at the same level.
2. Drag reduction and suppression of vibration in flow around a bluff body

Also in the flow around a bluff body, such as circular and square cylinders, the drag (mainly pressure drag) can cause energy loss. Flow around a bluff body often separates to alternately emit vortices in the wake, which will cause vibration and noise. In this study, we attempt to reduce these by using active or passive control technique. As one of the passive control techniques, we also attempt to dynamically optimize the shape of bluff bodies by using numerical simulations.
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Naito & Fukagata, Phys. Fluids (2012)
hasebe-kiron11.jpg3. Suppression of wing-tip vortices

The vortex generated at the tip of a wing, called "wing-tip vortex," will remain far downstream of the wing. It causes so-called "wake turbulence" and limits the interval between takeoff and landing of aircraft. In this study, we attempt to suppress the wing-tip vortex by active control techniques using e.g. plasma actuators. By using wind tunnel experiments and numerical simulations, we first clarify the dependency on the angle of attack and the generation mechanism of wing-tip vortex, and investigate the effect of actuation.
4. Control of mixing layer

"Mixing layer," a layer involving two different streams such as the flow of fuel and oxidizer in engines, can be seen everywhere. If we can flexibly suppress or promote this mixing, more efficient and clean combustion can be achieved. On the other hand, in a small-scale flow, such as that in bio-chips, two reagents do not easily mix with each other; we need to actively promote mixing. In this study, we aim at flexible control of these mixing layers by means of experiments and numerical simulations.
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Hoepffner et al., J. Fluid Mech. (2011)
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Tamura & Fukagata (2010)
5. Numerical simulation of two-phase flows

The target of flow control is not only single-phase flows, but also multiphase flows composed of different fluids. In bio-chips, for instance, it is needed to predict the behavior of cells in the fluid and to control it. For friction drag reduction using superhydrophobic surfaces like lotus leaves, we need to understand the behavior of air-water two-phase flow under shear. Even today, numerical simulation of multiphase flows is a challenging issue involving many difficulties. We are conducting study in order to overcome these difficulties.
6. Development of actuators for flow control

Once the effect of proposed active control technique has been confirmed by numerical simulation, we will verify it by physical experiment. Actuators are required on that stage. In this study, we develop actuator devices, such as piezo-film actuators and plasma actuators and evaluate their characteristics and performance. Numerical simulation is also used to study the detailed working principle and to improve the actuator performance.
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Fukagata et al., Nagare (2010)
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Nakayama et al. (2012)
7. Development of dynamic parameter-optimization methods

Problems of flow control and shape optimization of a body in flow eventually require optimization of multiple parameters so as to minimize (or maximize) the prescribed cost function. In this study, we develop control theory-based methods to dynamically optimize such parameters while running flow simulation.

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Last-modified: 2016-11-22 (Tue) 06:15:47 (305d)
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