박승오 교수

This paper reports velocity measurement data in the interaction region between the impeller and vaned diffuser and the results of numerical flow simulation of the whole machine (impeller, vaned diffuser and volute) of a single stage centrifugal fan. Two-dimensional instantaneous velocity measurement is done using particle image velocimetry (PIV). Numerical simulation of impeller-diffuser-volute interaction is performed using CFX-Tascflow commercial code. A frozen rotor simulation model is used f

When two-equation turbulence models are used, unrealistically large values of turbulence variables can appear due to the infringement of a realizability condition or to numerical error. To cure this in practical calculations, various limiters on the source terms are often employed. In the present work, a mathematically correct bound for eddy viscosity is obtained from the realizability condition itself. From this, realizability bounds for several terms of model equations are given. The effects o

An experimental investigation was carried out to study the unsteady, near wakes behind an oscillating airfoil. the airfoil was given the harmonic pitching motion about the one-quarter chord axis at two reduced frequencies, 0.1 and 0.2. The amplitude of oscillation was 7.4 degrees. To assess the effect of mean incidence, the mean incidence of oscillation was varied from 104 degrees. When the mean incidence was 4 degrees, the airfoil was found to undergo a deep stall.

To investigate positive and negative thermophoretic effects for polystyrene latex (PSL) spheres of diameter between 0.3 and 0.8 μm, the average deposition velocity toward a horizontal wafer surface in vertical airflow is measured keeping the wafer surface temperature different from the surrounding air temperature. The temperature difference ranges from -10° to 4°C. The number of particles deposited on a wafer surface is obtained from the measurements by using a wafer surface scanner (PMS SAS-360

The average particle deposition velocity toward a horizontal semiconductor wafer in a vertical airflow was measured by a wafer surface scanner (PMS SAS-3600) to shorten the exposure time and hence to improve repeatability. Polystyrene latex (PSL) spheres with diameters between 0.2 and 1.0 μm were used. For the present experiment, convection, diffusion, and sedimentation comprise important agents of the deposition mechanism. The mean and standard deviation of average deposition velocities were ob

Introduction R ECENTLY unmanned vertical takeoff and landing vehicles have attracted aeronautical engineers’ attention. One of those is a canard rotor/wing (CRW) aircraft, and several studies have been reported.1−3 CRW aircraft usually employs a two-bladed rotor to takeoff the ground; after taking off, it locks the rotor to act as a fixed wing, allowing it to cruise at high speed. This requires that the cross section of the rotor blades be elliptic. Flow past an elliptic cylinder or ellipse cros

Stability of a supersonic boundary layer over two-dimensional smooth humps with their heights considerably smaller than the local boundary layer thickness is studied by using parabolized stability equations (PSEs). Influence of humps on linear and non-linear evolution of first mode oblique wave in Mach 1.6 boundary layers is investigated. Overall destabilization influence of the hump is confirmed for both linear and non-linear cases. For the case of linear stability, an overall effect of the hum

A flow visualization study was made to examine qualitatively the unsteady wing-tip vortex roll-up of an oscillating wing. A rectangular wing of aspect ratio 4 with NACA 0012 airfoil cross-section was mounted on one side of the wind tunnel wall, and the wing was pitched sinusoidally about the quarter chord. Both the mean incidence and the amplitude of oscillation were set at 15°. The reduced frequency of the oscillation was 0.09. Visualized flow patterns both in streamwise and in cross-sectional