Influence of the elliptical and circular orifices on the local heat transfer distribution of a flat plate impinged by under-expanded jets
TL;DR: In this paper, the influence of nozzle profile on heat transfer for underexpanded impinging jets was explored and it was observed that plate shock and pressure distribution over the plate have significant influence on the local heat transfer.
Abstract: Experimental study is carried out to explore the influence of nozzle profile on heat transfer for underexpanded impinging jets. Circular and elliptical orifices are used to generate underexpanded jets for underexpantion ratio ranging from 1.25 to 2.67. The supply pressure maintained in the present study ranges from 2.36 to 5.08 times the ambient pressure.
IR thermal imaging camera is used to measure surface temperature of thin foil at different nozzle to plate distances. Shadowgraph and pressure distribution are used to understand the flow structure and distribution of circular and elliptical nozzle. It is observed that plate shock and pressure distribution over the plate have significant influence on the local heat transfer. The performance of the circular orifice is far better at lower z/d. The axis switching is observed for an elliptical orifice. Correlation for local heat transfer predicts Nusselt number comparable within 15 % of experimental results.
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TL;DR: In this paper, the authors explored the basic characteristics of the underexpansion jet flame in premixed H2/air explosion venting, and discussed the formation of two under-expansion structures (Mach disk and diamond shock wave) of such jet flames.
71 citations
TL;DR: In this article, the authors present an overview on progress and perspectives of the jet impingement research for rocket launching and discuss the interaction of impinging jets with multiphase flows.
31 citations
TL;DR: In this article, the effects of nozzle-pressure-ratio and separation distance variations on the standoff shock formations were investigated with schlieren visualizations and a visual hull based three-dimensional (3D) shock reconstruction technique to provide deeper insights into their 3D features.
19 citations
TL;DR: In this article, the thermal behavior of flat and curved surfaces with impinging jets employing circular and elliptical nozzle for identical equivalent diameter (de) was reported, and tests were performed w.r.t.
Abstract: The present paper reports the thermal behavior of flat and curved surfaces with impinging jets employing circular and elliptical nozzle for identical equivalent diameter (de). Tests are performed w...
9 citations
Journal Article•
TL;DR: In this paper, the results of an experimental and computational study of a moderately underexpanded axisymmetric supersonic jet issuing from a converging nozzle and impinging on a ground plane are presented.
Abstract: The results of an experimental and computational study of a moderately underexpanded axisymmetric supersonic jet issuing from a converging nozzle and impinging on a ground plane are presented. The goal of this work is to develop a better understanding of the impinging jet flowfield, which is of significant practical interest because of its presence in short takeoff and vertical landing (STOVL) aircraft during hover as well as in other aerospace-related and industrial applications. The experimental measurements include flow visualization, surface-pressure distributions, and velocity field data obtained using particle image velocimetry (PIV). The experimental data, especially the velocity field measurements, were used to verify the accuracy of computational predictions. Computational results obtained using two different turbulence models produced almost identical results
4 citations
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TL;DR: The material presented in this paper covers the method of describing the uncertainties in an engineering experiment and the necessary background material, as well as a technique for numerically executing uncertainty analyses when computerized data interpretation is involved.
6,868 citations
TL;DR: In this article, the authors examined the local heat transfer characteristics of air jet impingement at nozzle-plate spacings of less than one nozzle diameter using an infrared thermal imaging technique.
553 citations
TL;DR: In this article, the mean properties of the flow field are established for three types of jet flow issuing from a circular convergent nozzle, and measured distributions of surface pressure are given which result when the jets impinge both normally and obliquely at various distances on several surface shapes.
Abstract: In this, the first part of a two-part experimental study of the behaviour of impinging jets, the mean properties of the flow field are established. Velocity profiles are given for three types of jet flow issuing from a circular convergent nozzle. Measured distributions of surface pressure are given which result when the jets impinge both normally and obliquely at various distances on several surface shapes. The pressure distributions are used to compute the radial velocity gradient at the impingement stagnation point. It is found that for normal impingement this gradient correlates with the free jet centreline velocity and half-radius at the same axial location. A fall-off in the correlated value is noted as the impingement is made oblique. Measurements of the azimuthal distribution of momentum flux in the resulting wall jet are also given. The general behaviour of all three types of jet is found to be similar at locations downstream of any local effects due to the shock waves present in the under-expanded types. A special study of the close-range impingement of an under-expanded jet containing a normal shock disk reveals a region of separated flow surrounding the stagnation point. This condition results in a negative value of the radial velocity gradient at the centreline.
549 citations
TL;DR: In this article, the effect of jet-to-plate spacing and Reynolds number on the local heat transfer distribution to normally impinging submerged circular air jet on a smooth and flat surface was investigated.
277 citations
TL;DR: In this article, an extensive experimental study of the flows due to underexpanded axisymmetric jets impinging on flat plates is presented, where the main emphasis is on the behavior in the first shock cell.
Abstract: This paper reports on an extensive experimental study of the flows due to under-expanded axisymmetric jets impinging on flat plates. The range of plate locations extends to a point where the jet is just subsonic but the main emphasis is on the behaviour in the first shock cell. Plate inclinations from 90° to 30° were investigated by means of comprehensive surface pressure measurements and shadowgraph pictures. Wherever possible, the main features of the results have been reconstructed using inviscid analyses of the wave interactions.The flows are shown to be extremely complex due to the local structure of the free jet and, particularly, due to interactions between shock waves in the free jet and those created by the plate. In the near field, these interactions tend to be the controlling factors but at larger distances from the nozzle, mixing effects become increasingly important.The maximum pressure on the plate when it is inclined can be very much larger than when the plate is perpendicular, owing to the possibility of high pressure recoveries through multiple shock systems. Correlations are presented for some of the main features on perpendicular plates and it is shown that the integrated pressure loads for both normal and inclined plates can be predicted well by a simple momentum balance.
236 citations