The powered resonance tube: From Hartmann's discovery to current active flow control applications

The mechanism of the oscillatory phenomena of an underexpanded jet impinging on a flat plate is studied numerically. Pressure changes generated in the flow field near the plate propagate radially in the surrounding region of the jet. The configuration of the jet boundary is changed by them and so, the waves forming the underexpanded jet are displaced when they are reflected from the jet boundary. And then, the pressure disturbances return to the region near the plate. Unsteady flow with repetition of growth and decay of the separation bubble on the plate is also found under certain conditions

Numerical Study of Oscillation Mechanism in Underexpanded Jet Impinging on Plate

Visualization of Ambient Air Motion and Entrainment into a Transient Gas Jet Impinging on a Flat Wall

In this paper, the oscillation phenomena of underexpanded jet and the motion of the vortex induced by the jet are discussed. The jet becomes underexpanded when the nozzle pressure ratio of convergent nozzle discharging it exceeds the critical value. The underexpanded jet is not uniform and has a typical cell structure because the expansion wave, the compression wave and the shock wave are periodically formed in it. A vortex is induced one after another in the vicinity of the jet boundary due to shear stress and interacts with the jet as it moves downstream. The interaction of vortex and jet is closely related to the strong noise radiating from such flow field. This flow field is often observed as the assist gas of laser cutting, the exhaust jet of VSTOL aircraft and rocket, and so on. In this paper the flow field is experimentally visualized in order to analyse the behavior of cell structure of jet. Furthermore, a simple system for measuring the advective velocity and the frequency of vortex generation is...

A Study on behavior of underexpanded jet and induced vortex

In this study, flow characteristics are experimentally and numerically discussed, especially concerning shock-cell structure and oscillatory phenomena of supersonic jet. The jet becomes underexpanded when the nozzle pressure ratio of convergent nozzle exceeds the critical value. The underexpanded jet is not uniform because of the presence of the expansion wave, the compression wave and the shock wave formed in it. Many vortices are induced in jet boundary region by shearing stress generated between supersonic jet flow and atmospheric air. They interact with shock waves composing cell node of jet, which is closely related to a noise radiating from the jet. In experiment, flow field is visualized and the shape of cell structure is examined. Furthermore, frequency of vortex generation is measured. The jet is simulated using TVD scheme and the results are compared with the experimental ones. Distortion of cell structure caused by three dimensional oscillation of jet and behavior of vortices are discussed.

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Structure and Oscillation of Underexpanded Jet

This study is concerned with an underexpanded free jet flowing from an axisymmetric convergent nozzle and its impingement on a flat plate placed perpendicular to the jet axis. In the experiment, shadow photography was used to visualize the flow field and the sound pressure level of the noise generated in the jet was measured. As a result, the relation between the location and shape of the plate shock in the jet and the nozzle-plate spacing was established. Furthermore, we found how the sound pressure level of the noise changes with the jet structure, or the nozzle-plate spacing.

https://www.jstage.jst.go.jp/article/kikaib1979/60/579/60_579_3873/_pdf

Study on the Noise Generated from Underexpanded Free and Impinging Jet.

The purpose of this study is to clarify the jet tip velocity and mixing process between the jet and its surrounding fluid. The analysis was made with the time history of injection velocity which monotonously rises up just after the opening of injection valve and is steady later. The jet is injected into quiescent ambient air. The jet tip velocity first increases, then decreases, increases and last decreases with time lapses from injection. Therefore, the growing process of the jet is composed of four periods from the standpoint of the jet tip velocity. The jet tip velocity is maximum at the time boundary between the first and second growing periods, when the rate of increase of the injection velocity is maximum. The mixture between the jet and surrounding fluid is very active at this time. The growing period between the first period to the initiation of the fourth period corresponds to the unsteady period of injection velocity.

Study on Characteristics of Transient Gas Jats. Jet Tip Velocity and Mixing Process in Front.

Impingement of an axially-symmetric, underexpanded sonic jet on a perpendicular flat plate is studied using flow visualization and a numerical technique. The numerical results which are obtained by a two-step Lax-Wendroff scheme under the assumption of inviscid flow are in good agreement with the experimental results. It is found that the maximum pressure is not always at the center on the plate, and that there may be a reverse flow in the central area on the plate.

On the flow pattern when an underexpanded jet impinges on a flat plate.

The unsteady, one-dimensional flow in an H-S tube was calculated using the Random-Choice Method, in which the wall friction and the heat transfer wre taken into account. In particular, the effect of the length of the tube was examined, and the following conclusions were drawn: 1. The amplitude of the pressure oscillation decreases with an increase in the tube length. 2. for a tube of L=10m, the initial penetration length of the contact surface is 60% of the tube length measured from the open end, and after the interference of the contact surface with the shock wave, it becomes stationary without flow oscillation. 3. The maximum penetration length of the contact surface for a tube of L=1m is 37% of the tube length.

Junjiro Iwamoto

Papers

Study on the Noise Generated from Underexpanded Free and Impinging Jet.

Study on Characteristics of Transient Gas Jats. Jet Tip Velocity and Mixing Process in Front.

On the flow pattern when an underexpanded jet impinges on a flat plate.

The effect of tube length on wave phenomena in an H-S tube.