Hiromu Sugiyama

Numerical and Experimental Investigations on the Mach 2 Pseudo-Shock Wave in a Square Duct

This paper describes numerical and experimental investigations for the multiple shock wave/turbulent boundary layer interaction in a Mach 2 supersonic square duct. The numerical simulation is carried out with the Harten-Yee second-order accuracy TVD scheme and the Baldwin-Lomax turbulence model. The flow conditions are a free-stream Mach number ofM∞≈=2.0 and a Reynolds number ofRe∞;=2.5×107 and the flow confinements are δ∞/h=0.15 (case A) and δ∞/h=0.25 (case B), respectively. The computational results for both cases show good agreement with the experimental results. Based on these agreements, the flow quantities, which are very difficult to obtain experimentally, are analyzed by numerical simulation. Moreover, the effect of flow confinement on the pseudo-shock wave characteristics is also presented.

Internal structure of Pseudo‐shock waves in a square duct

This paper is concerned with the internal structure of pseudo‐shock waves in a straight square duct. The experiments were carried out for M1=1.77 using a dual‐beam Laser Doppler Velocimeter (LDV) and Double Exposure Laser Holographic Interferograms, where M1 was the flow Mach number just ahead of pseudo‐shock wave were measured in detail, and the variations of velocity and the boundary layer displacement thickness were clarified. The displacement thickness increased at the shock wave locations and decreased in the regions between the shock waves. The velocity distributions calculated from the density distributions, which were measured by holographic technique, were compared with the results obtained by LDV. As each shock wave in the pseudo‐shock wave was very weak, the flow in the central part of the duct seemed to be an isentropic flow, while the flow near the wall seemed to be an irreversible adiabatic flow.

H2 Concentration Profile in Cold Supersonic Hydrogen-Air Mixing Layer* (Evaluation using Catalytic Reaction on Constant Temperature Pt Wire)

Hydrogen was injected normally to a Mach 1.8 cold air stream with a backward-facing step to investigate mixing flow field in a scramjet combustor. Catalytic reaction on constant temperature Pt wire was used to measure the mixing condition of t^ and C>2. It was new technique to investigate H2 mixing condition. The amount of heat release due to the catalytic reaction, which corresponds to the concentration of H2 and/or C>2 on the surface of the catalyst, was measured spatially so that the local mixing condition of H2 and O2 was cleared. The results showed that there were two core regions, which would have good mixing condition for supersonic combustion, in the mixing layer. The development of core regions along flow direction was also clarified.

LDV Investigation of Turbulence Phenomena in Multiple Shock Wave/Turbulent Boundary Layer Interactions

The turbulence phenomena in multiple shock wave/turbulent boundary layer interactions in a square duct have been investigated using a two-component laser Doppler velocimeter (LDV). The free stream Mach number M ∞, flow confinement δ ∞/h and unit Reynolds number Re just upstream of the interaction were of 1.78, 0.3 and 13×106 m−1, respectively. First, the interaction flow fields were visualized by using schlieren photographs and laser holographic interferograms. Second, the time-mean and fluctuating velocity fields were explored in detail using the LDV. Spatial distributions of turbulence intensity, Reynolds shear stress, turbulence kinetic energy and turbulence production are presented.

Three-dimensional structure of pseudo-shock waves in a rectangular duct

The three-dimensional structure of a pseudo-shock wave in a straight square duct was investigated using a 2 color 4 beam LDV and a color schlieren method. The Mach number just upstream of the pseudo-shock wave was 1.83, the Reynolds number was 6.8xl04, and the confinement parameters were about 0.2 for the upper and side walls. It was shown that the structure of the pseudo-shock wave depends on the characteristics of the wall boundary layer and that the formation of the second shock is due to the variation of the displacement thickness of the boundary layer (aerodynamic nozzle) in the pseudo-shock wave.

An experimental and numerical study of the shock wave‐induced flows past a circular cylinder in a dusty‐gas shock tube

An experimental and numerical study was made on the shock wave‐induced flows past a circular cylinder in a dusty‐gas shock tube. Air containing fly ashes (mean diameter 5 μm) was used for dusty‐gas. Flow visualization studies were conducted by a shadowgraph method and an Imacon high speed camera, and a pulsed laser holographic interferometry. The behavior of shock waves past a circular cylinder in a dusty‐gas, the development of dust‐free regions and the formation of vortices behind a circular cylinder were clarified by those flow visualization method. The experimental results of the shock wave‐induced dusty‐gas flow past a circular cylinder were also compared with the numerical simulation using the TVD finite difference scheme applied to the Navier‐Stokes equations. Good agreement was obtained between the interferograms and the numerical simulations.

Dynamic Characteristics of a Check Valve for Drain Pumps

Check valves for checking reverse water flows in drainage systems sometimes make large impacts through their sudden closure caused by accidental cutoff of drain pumps. In order to characterize such phenomena and to find design criteria for impactless check valves, we observed the motion of a check valve and measured its impact acceleration and pressures in the drainage pipe, using a subscale drainage system. Two peaks of impact acceleration were observed; The first one seemed due to collision of the check valve and the valve seat, whereas the second one did due to water column separation and recombination caused by the low pressure during the contact of the valve with the seat. The former can be reduced by adding mass to the check valve and by setting an appropriate valve-seat angle. The latter possibly can be reduced by relaxing the low pressure during the contact. Subsequently, the check valve opened through the water-column recombination impacts.Copyright

Numerical and experimental study of the Mach 2 pseudo-shock wave in a supersonic duct

This paper presents an investigation on the structure and characteristics of the multiple shock wave/turbulent boundary layer interaction in a Mach 2 supersonic square duct by numerical simulation and experiment. The numerical simulation is carried out with the Harten-Yee’s second-order accuracy TVD scheme and the Baldwin- Lomax’s turbulence model. The flow conditions are: free stream Mach number M∞ = 2.0, unit Reynolds number Re∞/m = 2.5xl07m−1, and the flow confinement is δ∞/h = 0.25. Good agreements between the numerical analysis and the experiment for the shape of the shock train and wall pressure distribution along the duct are obtained. Based on these agreements, the flow quantities, which are difficult to obtain by experiment, are analyzed by numerical simulation.

Mixing Enhancement by Normal Gas Injection in Supersonic Mixing Layer

It is important to understand the supersonic mixing layer in Scramjet engine combustor. In this paper, the helium gas through the tube (outer diameter: 1.0mm, inner one: 0.7mm) was injected normally into the supersonic mixing layer in order to enhance the supersonic mixing. The flows were analyzed by LDV measurements. It was found that the supersonic mixing was enhanced by the helium gas injection and shock-wave induced by the tube. Furthermore, the some terms in turbulence kinetic energy equation were also discussed.

Visualization of a Pseudo-Shock Wave in a Rectangular Duct

The internal structure of a pseudo-shock wave in a straight square duct was visualized using a color schlieren and a laser holographic methods. The Mach number just upstream of the pseudo-shock wave was 1. 8, and the Reynolds number was 6.8X104. The velocity distributions in the pseudo-shock wave were also measured in detail using a two-dimensional LDV system. The density distribution in the pseudo-shock wave and the effect of top and side wall boundary layers on the structure of the pseudo-shock wave were clarified.