Review of aerospace-oriented spray cooling technology

The use of modern ultra-high speed cameras to acquire time-resolved schlieren image sequences of supersonic jet impingement is presented. The use of these cameras, with framerates of up to 1 million frames per second, allows for the first time-resolved visualizations of the impinging jet acoustic feedback loop. The role of upstream travelling acoustic waves in generating perturbations in the jet shear layer at the nozzle exit is also directly observed for the first time. The arrival of the acoustic wave at the nozzle lip generates a sinusoidal variation in density gradient that persists until a distance of $$\frac{x}{d}=0.3$$
 . A structure that rapidly evolves into a large-scale vortex ring forms at the trailing edge of this initial instability, first observed at approximately $$\frac{x}{d}=0.25$$
 .

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The visualization of the acoustic feedback loop in impinging underexpanded supersonic jet flows using ultra-high frame rate Schlieren

In 1971, the U.S. National Aeronautics and Space Administration (NASA) published a seminal report-NASA SP-8072-which compiled the results of the early supersonic jet noise studies and provided methods to calculate the noise produced from launch vehicles. Fifty years later and despite known limitations, SP-8072 remains the foundation for much of the launch vehicle noise modeling today. This article reviews what has been learned about the physics of noise generation and radiation from free and impinging rocket plumes since the completion of SP-8072. State-of-the-art methods for the mitigation of launch vehicle noise are also reviewed. A discussion of launch vehicle noise modeling, from empirical to numerical and including reduced-order models of supersonic jets, points to promising approaches that can describe rocket noise characteristics not captured by SP-8072.

Supersonic jet noise from launch vehicles: 50 years since NASA SP-8072.

The thermal environment of four-engine liquid rocket exhaust plume impinging on the flame deflector with different impingement and uplift angles is analysed. The supersonic exhaust gas impinging mo...

https://www.tandfonline.com/doi/pdf/10.1080/19942060.2020.1761453

Numerical study for the flame deflector design of four-engine liquid rockets

A concentrated sunlight energy wireless transmission system for space solar energy harvest

A review of impinging jets during rocket launching

Supersonic jets are in common use in aerospace, where the Mach-disk height is an important parameter to the aerothermodynamic and acoustic effects of the related interaction. To understand the Mach disk and predict its height, two-dimensional supersonic underexpanded jets are analyzed and a theoretical model is proposed in this work. First, through analyses of the viscous term in the Navier–Stokes equation, the dominance of an inviscid mechanism is verified upstream of the Mach disk. The pressure downstream of the Mach disk is a primary parameter to the prediction of the Mach-disk height. Then, the region dominated by the inviscid mechanism is divided into the following three regions: homogeneous, simple, and nonsimple by contour lines of the Riemann invariants. Analytical description of the simple region is achieved through analyses of the characteristic curves. Fan-shaped approximation to the nonsimple region is deducted based on analyses of expansion fans. Finally, a theoretical prediction of the Mach-disk height is developed based on the pressure downstream of the Mach disk. For either the freejet or the lateral jet interaction, it is feasible to obtain prediction with errors below 10%, which is much better than existing empirical models, especially for supersonic underexpanded jets. 

Tianyixing Han

Papers

A review of impinging jets during rocket launching

Theoretical Prediction for the Mach-Disk Height in Two-Dimensional Supersonic Underexpanded Jets