Underexpanded Impinging Jet Research Articles

Relation between Sound Radiated from Underexpanded Impinging Jet and Disturbance Convection Velocity

An underexpanded jet perpendicularly impinging on a flat plate was experimentally studied in this study. The flow field radiates noise including screech, and its frequency and sound pressure are varied against the nozzle pressure ratio and the nozzle-plate spacing. A feedback loop in the flow field is known to describe the screech phenomena well, and disturbances moving along the jet boundary play an important role in the feedback loop. This study focused on contribution of the disturbance velocity to the sound pressure variation of the screech. The jet issued from a circular convergent nozzle with a diameter D. Sound pressure measurement and visualization were carried out at different nozzle-plate spacings l/D. The sound pressure measurement showed the screech due to the jet impingement was very weak in a certain range of l/D. The Schlieren photographs described the disturbance did not develop in such range. The disturbance velocity is one of the parameters for the screech phenomena. The disturbance velocity was estimated from frequency characteristics of the sound pressure. Characteristics of the disturbance velocity changed in the weak screech range of l/D, where there are disturbances with different velocities. This denotes the change of the disturbance velocity characteristics attenuated the sound pressure of the screech.

Study on Underexpanded Impinging Jet Issued from Rectangular Nozzle

This research is concerned primary with pressure distributions and oil flow on the plate to figure out the flow structures for the rectangular nozzles by comparing three-dimensional calculations to the experiments. Flow visualizations were performed using the oil-flow method and schlieren method in our experiments. Underexpanded impinging jet issued from rectangular nozzle of three aspect ratio (1, 3 and 5) were investigated. The flow field was calculated by solving three dimensional compressible Navie-Stokes equations. According to the flow visualization on the plate using oil flow method, it is confirmed that the flow is separated on the impinging plate from center point toward outside at only aspect ratio 1. These experimental results tell us that the flow on the plate avoids the four high pressure areas near the center point only for aspect ratio 1. The corresponding calculations were fairly good agreement with the experimental ones.

11405 円錐に衝突する不足膨張噴流の圧力分布とプレート衝撃波の挙動に関する研究(流体工学(1))

In order to investigate the pressure distribution of underexpanded impinging jet on a cone and its behavior of plate shock in the vicinity of the cone, the flow field is visualized by schlieren and shadowgraph method and the pressure distributions on the cone are measured. Cones used for the experiment have a vertical angle of 60 and 120deg. The pressure ratio of stagnation of the jet to the ambient is fixed to 4.0 and the nozzle-cone distance is varied in the range of 1.0 to 3.5 nozzle diameters. It is shown that the plate shock changes in its shape according to the nozzle-plate distance. The expansion and compression regions are found to be present in the wall jet. The comparison of these results with pressure distributions is made, and the flow behavior is examined and discussed.

213 不足膨張衝突噴流に関する研究 : プレート衝撃波近傍における流れ場について

213 不足膨張衝突噴流に関する研究 : プレート衝撃波近傍における流れ場について

201 不足膨張衝突噴流に関する実験的研究 : 不足膨張衝突噴流流れ場における噴流構造の解明

201 不足膨張衝突噴流に関する実験的研究 : 不足膨張衝突噴流流れ場における噴流構造の解明

Temperature and Pressure Distributions on Plate in Underexpanded Impinging Jets. 1st Report, Circular Jet Impinging Normal to Plate.

The temperature and the pressure distributions on a plate in underexpanded impinging jets are experimentally and numerically studied in this paper. The experiments were performed by measuring the adiabatic wall temperature using infrared imaging camera and the wall static pressures on the impinging plate and by visualizing density fields using schlieren method. Numerical calculations were conducted by solving two dimensional axisymmetric compressible Navier-Stokes equations and three dimensional compressible Euler equations. The comparison between the experiments and the calculations shows that the decrease in the stagnation temperature is caused by a recirculating flow carrying the cold air from the jet boundary to the stagnation point. The temperature and pressure ; contours on the impinging plate illustrate azimuthal structures for the circular nozzle, which are also confirmed by the three dimensional calculations.

Experimental Study on Oscillation Mode of Underexpanded Impinging Jet and Behavior of Plate Shock Waves.

Experimental Study on Oscillation Mode of Underexpanded Impinging Jet and Behavior of Plate Shock Waves.

112 円形および矩形噴口による不足膨張衝突噴流に関する研究

112 円形および矩形噴口による不足膨張衝突噴流に関する研究

Oscillatory Phenomena of Underexpanded Impinging Jets.

Oscillatory Phenomena of Underexpanded Impinging Jets.

Experimental Study on Oscillation of Underexpanded Impinging Jet and Behavior of Plate Shock Wave.

In order to investigate the oscillation of an underexpanded impinging jet and the behavior of plate shock wave in the vicinity of a plate, we visualize the flow field mainly using the Mach-Zehnder technique and measure the pressure on the plate. At a nozzle pressure ratio of 3.0, the shape of the plate shock wave changes periodically with nozzle-plate spacings. However, when the spacing exceeds a certain value, the type of oscillation changes markedly. The change of oscillation is confirmed by interferograms and pressure measurements. Comparing the jet structure with the oscillation, the change can be considered to be caused by instability of the jet boundary.