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.
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. Construction of low-dimensional model extraction method of flow

Recent development of numerical and experimental techniques has enabled us to easily acquire time-space data of complicated flow including turbulence. However, millions to tens of billions of degrees of freedom of those data make modeling and control difficult. In this research, we are working on a feedback control method of turbulent flow based on linear theory such as Resolvent analysis. We are also working on turbulence modeling and development of turbulent inflow generator using machine learning. Our final goal to construct a feature extraction method by combining linear theory and machine learning.
Hoepffner et al., J. Fluid Mech. (2011)
Tamura & Fukagata (2010)
5. Numerical simulation of multiphase flows

The target of flow control is not only single-phase flows, but also multiphase flows composed of different fluids. In a classification device for PM2.5, for instance, it is needed to predict the behavior of charged particles in the air flow 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.
Fukagata et al., Nagare (2010)


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Last-modified: 2018-04-10 (Tue) 03:48:25 (43d)
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