In recent past, a wide variety of applications have been found for the use jets in fields of stud... more In recent past, a wide variety of applications have been found for the use jets in fields of study of flow control and many researchers have worked on jet flow control to enhance mixing and/or reduce noise. In order to develop a new mixing procedure, a direct numerical simulation (DNS) of dynamic controlled free jets was conducted. To achieve a high accurate computation, space discretisation method was performed using the hybrid scheme consisting sine or cosine series and 6th order compact scheme. The dynamic control proposed here are single and multiple rotating jets which are rotated unidirectionally around streamwise direction. According to the instantaneous vortex structures and, it is found that the flow pattern changes considerably with the rotating frequency. From the contour of streamwise velocity, in both cases, it is clear that the radial jet expansion of controlled jets are significantly enhanced compared to the uncontrolled one. We also concluded that, using the statisti...
The flow and heat transfer over a step (a forward- or backward-facing step) result in complicated... more The flow and heat transfer over a step (a forward- or backward-facing step) result in complicated flow conditions, such as a shear flow field, flow separation, and generation of vortices, and provide some interesting information that improves understanding of the heat transfer on the surface. This is a very frequent flow, and basic to various kinds of chemical equipment, fluid machinery, combustion furnaces, and IC-packages. Recently, there have been many studies on this flow situation by numerical analysis, measurement of mean and fluctuating velocities within the separation bubble using laser Doppler anemometer, and heat transfer analysis. A flow passage having two steps in tiers (forward- or backward-facing double steps) is also frequent, and it is very important to clarify the effects of each step on the flow and the heat-transfer characteristics. This however, has not yet been investigated. This study presents the results of an experimental investigation on the flow and forced convective heat transfer over forward-facing single and double steps. Measurements of velocity and turbulence intensity, flow visualization, pressure distribution, and heat transfer over forward-facing double steps were carried out for various step ratios, L/a (L: step length, a: step height). From these results, the effects of the stepmore » ratio on the flow and heat-transfer characteristics were clarified and the following results were confirmed. Heat-transfer enhancement of a double step is considerable compared with that of a single step or a flat plate.« less
In recent past, a wide variety of applications have been found for the use jets in fields of stud... more In recent past, a wide variety of applications have been found for the use jets in fields of study of flow control and many researchers have worked on jet flow control to enhance mixing and/or reduce noise. In order to develop a new mixing procedure, a direct numerical simulation (DNS) of dynamic controlled free jets was conducted. To achieve a high accurate computation, space discretisation method was performed using the hybrid scheme consisting sine or cosine series and 6th order compact scheme. The dynamic control proposed here are single and multiple rotating jets which are rotated unidirectionally around streamwise direction. According to the instantaneous vortex structures and, it is found that the flow pattern changes considerably with the rotating frequency. From the contour of streamwise velocity, in both cases, it is clear that the radial jet expansion of controlled jets are significantly enhanced compared to the uncontrolled one. We also concluded that, using the statisti...
The flow and heat transfer over a step (a forward- or backward-facing step) result in complicated... more The flow and heat transfer over a step (a forward- or backward-facing step) result in complicated flow conditions, such as a shear flow field, flow separation, and generation of vortices, and provide some interesting information that improves understanding of the heat transfer on the surface. This is a very frequent flow, and basic to various kinds of chemical equipment, fluid machinery, combustion furnaces, and IC-packages. Recently, there have been many studies on this flow situation by numerical analysis, measurement of mean and fluctuating velocities within the separation bubble using laser Doppler anemometer, and heat transfer analysis. A flow passage having two steps in tiers (forward- or backward-facing double steps) is also frequent, and it is very important to clarify the effects of each step on the flow and the heat-transfer characteristics. This however, has not yet been investigated. This study presents the results of an experimental investigation on the flow and forced convective heat transfer over forward-facing single and double steps. Measurements of velocity and turbulence intensity, flow visualization, pressure distribution, and heat transfer over forward-facing double steps were carried out for various step ratios, L/a (L: step length, a: step height). From these results, the effects of the stepmore » ratio on the flow and heat-transfer characteristics were clarified and the following results were confirmed. Heat-transfer enhancement of a double step is considerable compared with that of a single step or a flat plate.« less
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Papers by Toshihiko Shakouchi