Chaotic mixing in six types of curved-rectangular channel flows has been studied experimentally and numerically. The wall of channel rotates around the center of curvature and a pressure gradient is imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flow. We have investigated the effects of two different types of moving walls, inner and top walls (B.C.1), and an inner wall (B.C.2) on chaotic mixing. The non-dimensional parameters concerned are the Dean number De and the Taylor number Tr. The secondary flow is measured using PIV and LIF methods to examine secondary flow characteristics. Also we performed three-dimensional numerical simulations for the exactly same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing is obtained in the case of De ≤ 0.1Tr. This tendency appears more strongly if the aspect ratio is large and B.C.1.

The microtube heat exchanger performs heat exchange by setting up alley tube group in a duct. In the conventional analysis, since the wall thickness of the pipe is thin, the analysis was performed by applying isothermal conditions to the side of the pipe. However, in recent years, as the processing technology is digitized, the increase in the wall thickness with respect to the pipe diameter becomes remarkable. Therefore, in this analysis, numerical analysis of the flow channel with tubes with different wall thicknesses was conducted, and the flow characteristics of the fluid and the heat transfer characteristics inside the tube were investigated.

In semiconductor production, efficiency and precision of the cleaning process are very important. In this study, we handle “Single Wafer Cleaner” that is one of the washing methods in the way of blowing air to a wafer with a turning disk at a high speed. However, the flow in the device becomes turbulent, which causes the problem that water drops and dusts re-attach to the wafer surface. Therefore, it is necessary to understand the flow in the device exactly to solve this problem. In previous studies, we experimented to establish the method of understanding the flow in the semiconductor wafer cleaner without a covering cup that is used for liquid splash preventing. In this study, numerical calculations were performed to observe the flow in the device to study influence of covering cup and find a suitable turbulence model to simulate the experiment.

For large-eddy simulation (LES) of turbulent flow within a realistic computational time, assessment of the accuracy of subgrid scale model, especially in the case where the computational grid is very coarse is of significant importance. We perform a comprehensive grid resolution study of the WALE model in a turbulent pipe flow. The LES is performed under a constant flow rate at the bulk Reynolds number of 5300. The results show that the turbulent statistics such as the mean velocity profiles and the second order moments significantly depend on the spanwise grid resolution, while less sensitive to the streamwise grid resolution. Moreover, the statistics are reasonably well reproduced using only 6 computational points in the radial direction if only the first computational point is located within 5 wall units from the wall.

The sorting devices of microfluidic system have a passive method and an active one. Curved microchannels are often used in these systems due to secondary flows. Because sorting or mixing can be used with the secondary flow in these systems, it is necessary to clarify the characteristic of the secondary flow. In this study, we investigate behavior of particles in spiral rectangular microchannel, and effects of particle density and of Dean number De on the particle sorting. We performed three-dimensional numerical simulations using the particle tracking method (PTM) to analyze the particle sorting. When particle density is large than water density, it is found that good sorting is obtained in the case of De ≈ 20.

To avoid global warming, high-performance of Double Tube Heat Exchanger constituting car air conditioner is required. In order to realize this, Attention has been paid to placing dimples in the heat exchanger that are expected to improve heat transfer efficiency. However, there are few studies that clarified the optimal shape of dimples and the detailed flow structure inside the tube depending on the arrangement method. So, in this study, for establishing an optimum design method for dimples at a low cost, numerical thermal flow analysis by in-house code is carried out and investigation was conducted on the influence of the dimples inside the pipe on the flow structure and heat transfer characteristics. As a result, elliptical shaped dimple did not result in favorable results compared with the circular shaped dimple. In addition, it was suggested that protrusion is more effective when comparing recesses and protrusions with the same shape.

We conducted numerical simulations of the benchmark experiments of the pump sump conducted by Matsui et al. (2006 & 2015) and compared the simulation with the experimental data to investigate the effects of turbulence model, grid density and detection method of the vortices. We determined a threshold of the gas-liquid fraction function of VOF method (α) and the second invariant of velocity gradient tensor (Q2) to detect the air-entraining and submerged vortices by using vorticity, respectively. This method well detected the vortices and well reproduced the experiments for the RANS simulation using SST k-ω model. Large eddy simulation using Smagorinsky model, however, was sensitive to the grid system and difficult to reproduce the experimental vortex structures even for the finest grid system having 3.7 mil-lion cells.

Velocity measurements by PIV system have been done for the laminar backward-facing step flow in a duct at the Reynolds number of 400. The aspect ratio and the expansion ratio of the stepped duct were 16 and 2, respectively in this study. Attention was paid to grasp the spanwise variations of both of the instantaneous and the phase-averaged reattachment points and their relationships to the flow structures. The fluid flow characteristics varied in the spanwise direction was confirmed. Near the center of the duct, the fluid flow characteristics changed periodically. The vortices generated periodically and moved toward downstream and then disappeared by redevelopment of flow. Owing to this, the instantaneous reattachment points appeared downstream of these vortices, that is, they appeared upstream, and as time advanced they moved toward downstream, and then new ones appeared upstream. It was also found that the periodicity became weak as it approached from the center to the side wall.

This paper describes the intra-thoracic flow. Dean vortices are generated by the larynx and upper respiratory tract. Dean vortices are generated by a bent pipe that simulates the larynx and upper respiratory tract. This bent pipe is attached to the human bronchus model. In this paper, velocity profiles in the human bronchus model are examined experimentally by particle image velocimetry (PIV). Dean number was changed by curvature radius of bent pipes. As a result, the flow separation occurred on the wall surfaces on both sides of the first branch. However, the flow separation was restrained when Dean number was raised.

Impulsive decelerated flow in a pipe is important for development of turbulence, and when we attempt drug delivery in human lung, so turbulence is important for drug deposition. When pipe end is closed, turbulence develop from pipe end. But We suppose the middle of unbound long pipe to ignoring the effect of pipe end. This research focuses on this development of turbulence, and considers its characteristics by using CFD. Turbulence at high Re(≥5000) rise and to be dispersed whole region of pipe, and this turbulence accelerates deposition of particle. And compere Poiseuille flow and impulsive decelerated flow by analyzing spectrum. it was found that turbulence of impulsive decelerated flow develops faster than Poiseuille flow, and turbulence was prominent at R/D~0.6.

An experimental study is performed for multiple-passage duct flows. The multiple-passage is a reverse flow type, and consists of the five branch ducts. The dielectric barrier discharge plasma actuator (PA) is used for the flow control of reverse flow passages. The duct flows are investigated from the view point of flow uniformity and pressure loss reduction. The location in which the actuator is installed is changed in three positions of the outside wall at the inlet manifold and the outlet manifold. Reynolds number based on the bulk velocity and hydraulic diameter at the inlet duct are varied from 6.0×10² to 2.0×10³. The results show that the pressure loss decreases and the flow rate in each branch duct passages improves by the effect of induced flow with the PA. The effect is remarkable when the PA is installed near the first branch of the inlet manifold.