Supersonic Impinging Jets Research Articles

Unsteady Standoff Shock Behaviour Associated With Supersonic Impinging Jets

It was observed in an earlier study [Lim, H. D., New, T. H., Mariani, R., & Cui, Y. D. (2019). Effects of bevelled nozzles on standoff shocks in supersonic impinging jets. Aerospace Science and Technology, 94, 105371.] that standoff shocks in M=1.45 supersonic impinging jets produced by non-bevelled and bevelled nozzles under small separation distances may undergo large and abrupt fluctuations in their positions above the impingement points. This occurs when the separation distance is h/d=1.5 and for nozzle-pressure-ratio (NPR) between NPR=4 and 5, where h is the distance between the nozzle exit and flat-wall and d is the jet diameter. It has to be highlighted that the observed behaviour is unlike the more minor positional fluctuations typically associated with supersonic impinging jets. To reveal further details on the unsteadiness of the standoff shock, color schlieren results will be presented here to shed more light on the flow phenomenon, while initial modelling efforts to reproduce these standoff shock behaviour will be elaborated. Present results reinforce the notion that the large standoff shock fluctuations are due to the standoff shock trying to achieve pressure equilibrium through abrupt displacements when variation in the NPR changes the location of the shock reflection point. Considering the small separation distance used, small NPR changes are able to trigger abrupt standoff shock unsteadiness.

Experimental study of the noise suppression of supersonic impinging jets with chevrons

Supersonic impinging jets may cause many adverse ground effects, including surface erosion, nonuniform surface heat transfer, lift loss, and acoustic loading. In this study, chevron nozzles are used to suppress the noise generation of supersonic impinging jets originated from a circular convergent nozzle with the jet Mach number of 1.2. An array of microphones is used to measure the far-field acoustic fields, and a schlieren system is employed to measure the near-field flow structures. Three impinging distances are considered to examine the differences between the impinging jets and the free jet, and to assess the effect of impinging distance on the noise characteristics. Two chevron nozzles with different penetration angles are designed to investigate the potentials of chevron nozzles in controlling the supersonic-impinging-jet noise. Results show that the chevron nozzles do not alter the directivity of overall sound pressure levels, but significantly reduce the amplitude at all emission angles. The discrete tones in the impinging jets are dramatically mitigated or eliminated, and the levels of broadband noise are also significantly reduced over a wide range of frequency band, regardless of the impingement distance. The influences of chevrons on the near-field flow structures are checked with the root-mean-square values and proper orthogonal decomposition of schlieren images, which provide more evidence on the noise suppression mechanism with chevrons.

Effect of Different Flame Deflectors Plate Geometry on Supersonic Jet Impingement Flow and Heat Characteristics from Rocket Exhaust

The numerical investigation has been carried out on an under-expanded supersonic jet impingement on the perpendicular and inclined deflector plates of various shapes, such as flat, sinusoidal, and wedge types. The numerical study considers flat plates at Mach number of 2.2, and pressure ratio of 1.2, and results of flow and heat transfers are obtained using the Reynolds averaged Naiver Stokes (RANS) two-equation turbulence models. Various two-equation models (especially Standard k-ε, Reynolds Normalization Group k-ε, Realizable k-ε, Shear Stress Transport k-ω, and Baseline k-ω) were employed to predict the deflector’s surface temperature and pressure ratios. The pressure ratios are plotted with various two-equation turbulence models, and it is observed that among all turbulence models, the Shear Stress Transport k-ω shows close agreement with experimental results. Moreover, among the three deflectors, the wedge-shaped deflector shows improved performance in deflecting the rocket exhaust plume away from the surface. However, the maximum temperature on the deflector surface for a wedge-shaped deflector is 8.19% and 26% higher than the flat and sinusoidal-shaped deflectors, respectively.

A data-driven approach to guide supersonic impinging jet control

A data-driven framework using snapshots of an uncontrolled flow is proposed to identify, and subsequently demonstrate, effective control strategies for different objectives in supersonic impinging jets. The open-loop, feed-forward control approach, based on a dynamic mode decomposition reduced-order model (DMD-ROM), computes forcing receptivity in an economical manner by projecting flow and actuator-specific forcing snapshots onto a reduced subspace and then evolving the dynamics forwards in time. Since it effectively determines a linear response around the unsteady flow in the time domain, the method differs materially from typical techniques that use steady basic states, such as stability or input–output approaches that employ linearized Navier–Stokes operators in the frequency domain. The method presented naturally accounts for factors inherent to the snapshot basis, including configuration complexity and flow parameters such as Reynolds number. Furthermore, gain metrics calculated in the reduced subspace facilitate rapid assessments of flow sensitivities to a wide range of forcing parameters, from which optimal actuator inputs may be selected and results confirmed in scale-resolved simulations or experiments. The DMD-ROM approach is demonstrated from two different perspectives. The first concerns asymptotic feedback resonance, where the effects of harmonic pressure forcing are estimated and verified with nonlinear simulations using a blowing–suction actuator. The second examines time-local behaviour within critical feedback events, where the phase of actuation becomes important. For this, a conditional space–time mode is used to identify the optimal forcing phase that minimizes convective instability growth within the resonance cycle.

Two distinct mechanisms of tonal sound production in supersonic jet impingement

The interaction of high-speed jets with a perpendicular surface produces not only broadband sound, but “impingement tones,” that can be more than 30 dB above the broadband noise. It is well recognized that these tones are the result of an aeroacoustic resonance, driven by a feedback loop between the jet nozzle and the plate. However, the exact mechanism by which the tones are produced remains a topic of some dispute; some researchers locate the source within the core of the impinging jet, others in the wall jet generated after impingement with the plate. In this work, we demonstrate that both camps have correctly identified sources; there are two distinct mechanisms, with two distinct locations. The relative strength of these sources depends on the geometry of the problem, but we show that they can actually coexist at a single condition. Decomposition of high-speed schlieren data directly visualizes the location of these sources as a function of jet operating condition.

Heat transfer investigation on under-expanded supersonic impinging jets

In this study, wall-resolved large-eddy simulations are performed to investigate the underpinning physics of impingement heat transfer in under-expanded supersonic impinging jets. The jet is generated with an infinite-lipped nozzle of diameter D, has a nozzle-to-wall distance of 5D, a nozzle pressure ratio (NPR) of 3.4 and a Reynolds number of 6×104 based on the ideally-expanded jet velocity. Two thermal boundary conditions of a heated isothermal wall and an adiabatic wall for the impingement plate are considered.Both impinging jets in the current study feature a strong stand-off shock, which oscillates periodically in front of the impingement plate at two dominant frequencies. These oscillations result in two local peaks of the mean heat transfer coefficients with the first peak located in the stagnation region but shifted away from the stagnation point (i.e. jet axis), whilst the second peak is located in the wall jet region. The instantaneous fields of pressure, vorticity and Nusselt number are first discussed to study qualitatively the connection between these two peaks of the mean heat transfer coefficient and the near-wall flow structures. The characteristics of these two peaks are then analysed using the near-wall statistics and spectra of the pressure, axial velocity and Nusselt number distribution.It is found that the first peak of the Nusselt number forms as a consequence of the jet impingement of the non-periodic turbulent structures, whilst the second peak is linked to the reattachment of the recirculation bubble in the wall jet. It is shown that the unsteady separation and reattachment processes are strongly related to the oscillatory motion of the stand-off shock at the dominant frequencies. Last but not the least, the first local minimum close to the stagnation point is also found to be associated with the strong oscillatory behaviour of the stand-off shock.

Identification of Discrete Tonal Noise in Inclined Jet Impingement Using Pressure-Sensitive Paint

This paper presents the utilization of fast-responding pressure-sensitive paint (fast PSP) to identify the discrete tonal noise generated in 55 deg inclined jet impingement. Cases of subsonic () and supersonic () jet impingement with nozzle-to-plate distances of , and 8 are investigated. The fluctuating wall-pressure field measured using fast PSP at high spatiotemporal resolutions provides unique insights into the discrete tonal noises associated with inclined jet impingement. A far-field microphone is used to validate the frequency of each tonal noise. The fast PSP data are subjected to spectral proper orthogonal decomposition, and the results demonstrate wave propagation along the wall surface. At , the circumferential propagation characteristics of the identified discrete tones correspond to the toroidal mode of the shear layer instability wave. As increases, the dominant tone decays, and several secondary tones disappear. Screech tones are identified at and and 8. Two perpendicular flapping modes are identified at the discrete tone for each , and the dominant flapping direction varies with .

Investigating Shear-Layer Instabilities in Supersonic Impinging Jets Using Dual-Time Particle Image Velocimetry

Flow unsteadiness in supersonic impinging jets due to the aeroacoustic feedback can lead to practical problems like ground erosion in short takeoff and vertical landing aircraft, high noise levels, and high unsteady structural loading. The shear-layer instabilities of the jet play an important role in the flow dynamics. A full study of these instabilities requires time-resolved measurements of the flow velocity field. However, experimentally obtaining time-resolved velocity fields, derived from particle image velocimetry (PIV) techniques, has its challenges in high-speed flow applications due to the simultaneous requirement of high spatial and temporal resolution. A novel approach is presented in this paper, which uses time-unresolved dual-time digital PIV coupled with dynamic mode decomposition (DMD) analysis (DT–DPIV–DMD) of the velocity field pairs and applies it to study the dynamics of the shear-layer instabilities in supersonic impinging jets. DT–DPIV–DMD involves the acquisition of a pair of instantaneous velocity fields separated by a small time delay using two covisual PIV systems. The time delay must be sufficiently small to provide the necessary bandwidth to capture all the relevant dynamics of the flow being investigated. This is followed by DMD analysis of all acquired digital PIV velocity field pairs. A large-eddy simulation of an underexpanded impinging jet at Reynolds number 60,000, with nozzle-to-wall distance was first used to investigate the required measurement scales for the application of DT–DPIV–DMD. Using the optimum measurement scales, the technique was then experimentally demonstrated using DT–DPIV–DMD for two supersonic impinging jets cases and validated with acoustic measurements.

Investigation of the transient heat transfer to a supersonic air jet impinging on a high-temperature plate based on a discrimination-experiment method.

A discrimination-experiment method is developed to investigate the transient heat transfer of air jet impingement by discretizing the solid domain into mutually adiabatic test cylinders. This method can not only reduce the influence of the transverse heat transfer of a solid domain on the heat transfer characteristics of the jet but can also simplify the two-dimensional or three-dimensional heat conduction problem into a one-dimensional problem. Moreover, the discrimination-experiment method eliminates the embedment of thermocouples into the solid domains, further improving the accuracy and reliability of the proposed method. The transient heat transfer characteristics of a supersonic air jet impinging on a high-temperature target (860°C) and the effects of thermo physical parameters, such as the density, specific heat capacity, thermal conductivity and nozzle-to-target distance (H/D = 3, 4, and 5) are analyzed in detail using the discrimination-experiment method. The results provide important guidance for the thermal design of supersonic air jet impingement.

Dynamics and Response to Control of Single and Dual Supersonic Impinging Jets

An impinging jet produces a highly unsteady flowfield which results in very high noise levels, harmful structural vibrations, and significant loss of lift and stability in applications such as the short takeoff and vertical landing aircraft. An understanding of the flowfield and implementation of an effective flow control technique are necessary to reduce these adverse effects. The presence of multiple impinging jets leads to the generation of a fountain flow, which further adds to the complexity of the flowfield dynamics. In the present study, flowfields of a single supersonic round jet (Mach 1.5) and dual impinging jets (consisting of a Mach 1.5 supersonic jet and an additional sonic jet) are explored. A microjet-based control method is applied to attenuate flow unsteadiness by modifying shear layer instability characteristics of the supersonic jet. Passive and active influence of the microjet hardware on acoustics are examined over a range of impingement distances (2.25D–10D) with a fine resolution (D/16) to obtain detailed resonance characteristics. Based on the resonance tone behavior as a function of impingement distances, detailed flowfield characteristics at certain impingement distances are investigated with the help of schlieren visualization, near-field acoustics, and unsteady surface pressure measurements. The effectiveness of the microjet flow control method in reducing noise is also evaluated in the flowfield of single and dual impinging jets. For single and dual impinging jets configuration, relative to their respective baseline cases, the microjet control on dual impinging jets shows better noise attenuation of overall sound pressure level within short impingement distances ().

Influence of nozzle external geometry on wavepackets in under-expanded supersonic impinging jets

In this study, large-eddy simulations are utilised to unravel the influence of the nozzle's external geometry on upstream-travelling waves in under-expanded supersonic impinging jets. Three configurations, a thin-lipped, a thin-lipped with a sponge and an infinite-lipped nozzle are considered with the other non-dimensionalised geometrical and flow variables identical for the three cases. Spectral proper orthogonal decomposition is applied to the Mack norm, i.e. the energy norm based on the stagnation energy, to obtain the spatial modes at their corresponding frequency. The spectral decomposition of the spatial modes at optimal and suboptimal frequencies is used to isolate the wavepackets into upstream- and downstream-propagating waves based on their phase velocity. It is found that the external geometry of the nozzle has a significant influence on the first-order statistics even though the governing non-dimensional parameters are the same for all three cases. Multiple peaks emerge in the energy spectra at distinct frequencies corresponding to axisymmetric azimuthal modes for each case. The downstream-propagating wavepackets have a high amplitude at the shear layer of the three jets with the mode shapes resembling Kelvin–Helmholtz instability waves, while the upstream-travelling wavepackets exist in the three regions of the near field, shear layer and inside of the jet. The barrel shock at the nozzle exit appears as a flexible shield, which prevents upstream-travelling waves from reaching the internal region of the nozzle, where the upstream-travelling waves travel obliquely with one side of the wavefront is crawling on the reflected shock while the other side is guided by the shear layer. These latter waves can reach the nozzle lip via inside of the jet. The spectral decomposition of the spatial modes at optimal and suboptimal frequencies show that all three forms of the near field, shear layer and inside jet upstream-travelling wavepackets contribute to the receptivity process while their contributions and strength are altered by the change of the external geometry of the nozzle.

Experimental study on effects of plate angle on acoustic waves from supersonic impinging jets.

This study experimentally investigates the generation mechanism of a higher-angle lobe which is an acoustic field feature of a supersonic jet impinging on an inclined flat plate. The overall sound pressure level distribution and spectra, the conditional averages of near field schlieren movies, and the time-averaged wall pressure distribution were obtained for three cases of Mach 1.8 ideally expanded impinging jets with plate angles of 45°, 22.5°, and 10° to the jet downstream axis. In the 45° and 22.5° cases, a higher-angle lobe appears. The dominant acoustic waves in the higher-angle lobe are radiated from the source region that contains shock waves and are suggested to be correlated with large-scale turbulent structures. These results suggest that the higher-angle lobe is dominated by acoustic waves generated by the interaction between the shock waves and large-scale turbulent structures. This inference is supported by the fact that the near-field acoustic wave patterns are qualitatively reproduced by the interference of monopoles located near the shock waves in the 45° and 22.5° cases and that neither the shock wave nor the higher-angle lobe is observed in the 10° case.

Investigation of the shear-layer instabilities in supersonic impinging jets using dual-time velocity measurements

Motivated by applications in the propulsion industry, the fundamental study of phase-locked shear-layer instabilities in supersonic impinging jets has been of research interest for long time. While such flows have been experimentally investigated in various research studies using time-unresolved particle image velocimetry (PIV) techniques, the understanding of the shear-layer dynamics is limited, due to the absence of temporal information. Time-resolved PIV measurements for high-speed flows require a large bandwidth, which is challenging to achieve with the current state of technology. An alternate approach using time-unresolved double-PIV measurements is presented in the current study, which provides multiple samples of dual-time data, depicted in figure 1. Such data can be obtained using two co-visual PIV systems, triggered at a user-selectable time-offset, ∆t. As shown by Sikroria et al. (2020), the application of techniques like dynamic mode decomposition (DMD) on time-unresolved dual-time data provides valuable information about the flow structures governing the shear-layer instabilities. The experimental setup for such measurements in supersonic impinging jets, followed by the determination of the relevant dynamical flow structures from the data, will be presented in the conference.

Effect of Impact Cavity Shape Induced by Supersonic Oxygen Jet on the Dynamic Characteristics of Molten Bath in Converter

The cavity shape formed by the impinging of the supersonic oxygen jet on liquid metal surface is of importance to the converter steelmaking process. This work adopts the volume of fluid (VOF) model to numerically study the behavior of four‐nozzle supersonic jet impinging on molten steel bath in a 100 ton converter. First, the model is validated by comparing the jet velocity with that obtained from the literature. After validation, the dynamic interaction between supersonic jet and molten bath is studied. Moreover, the effects of lance height and operating pressure on the impact cavity depth and diameter are investigated. Compared with operating pressure, lance height shows a larger influence on altering the cavity dimensions. To quantitatively describe the profile of the scattered cavities, a dimensionless number called the modified cavity shape index (I cm) is put forward, which has a significant influence on the velocity distribution and specific kinetic energy of molten bath. The modified cavity shape index is found to be a function of the specific kinetic energy. With the modified cavity shape index ranging from 1.47 to 1.72, the dynamic flow of the molten bath becomes beneficial to the stirring and mixing of the molten bath.

Characteristics of acoustic and hydrodynamic waves in under-expanded supersonic impinging jets

Abstract

Numerical Studies on Flowfield Characteristics of Four-Engine Rockets Impinging Jet with Different Flame Deflectors

[Objective] To explore the further deep space, many countries are developing the new generation launch vehicle which has higher effective loads [1, 2]. To upgrade capacity, a scheme with multiple engines working simultaneously has often been adopted in the propulsion system of heavy launch vehicles [3, 4]. Therefore, the rocket jet impact problem has been the vital factor which seriously affected the launch safety. Due to the rocket engines are close to the launch platform during launching phase, the exhaust jets of rocket engine not only disturb the attitude of rocket in the take-off, but also have a thermal impact on the rocket base and ground control system [5]. Potential dangers would threaten secure and stable of launch missions if these problems could not be solved properly. Therefore, carrying out research on the flow field characteristics of multi-engine rockets exhaust plume has a great significance for the risk aversion and improvement of achievement ratio in launching [6-9]. This paper researches the four-engine rockets flow field during launching phase, compares and analyzes the plume impact characteristics with two shapes of flame deflector by numerical simulation methods. [Methods] The study object of this paper is a three-stage liquid rocket which utilizes kerosene/liquid oxygen (LOX) propellant as propulsion system for the first stage. Structured meshes with tensor product structure have better numerical ability than unstructured grids that using a multi-block, structured mesh to improve the fidelity of the flow solutions and assure a good resolution of shock waves in the flow field. The liquid rocket exhaust is considered as an ideal gas with the continuum assumption. The numerical solution of the compressible, multi-species, Reynolds-Averaged Navier-Stokes equations for multi-component flow has been obtained with finite volume spatial discretization on a structured three-dimensional grid implemented. The supersonic jet impingement on deflector was computed the realizable k-ε turbulence model. The model has shown superior improvements over the standard-model where the flow features include strong streamline curvature and vortices. The accuracy and effectiveness of the impact model was verified by comparison between the calculated results and the measured date. [Results] The temperature, pressure, and contours on the symmetry plane with wedge-shaped and cone-shaped deflectors are obtained, three shock cells are established before the plume impacts the deflector surface. A high temperature region occurs immediately through excessive high temperature gas accumulation on the deflector surface. The core and developed region and boundary of plume are clearly visible downstream of flow field. The supersonic exhaust plume was diverted into outlet with two directions and circumferential direction in the wedge-shaped and cone-shaped flame deflector, respectively. It can be shown from the temperature and pressure contours in the deflector surface that the region of peak temperature and pressure occur directly under the rocket nozzle, and the temperature drops gradually from the center to the outlet of the flame deflector. The simulation results show the planar static temperature contours for the rocket motor gas impingement on wedge-shaped and cone-shaped deflectors at Z/D = 3, 4.5, and 6 in axial plume direction, where Z/D = 0 corresponds to the nozzle exit. The exhaust gas inlet of the wedge-shaped deflector has the same temperature as atmosphere except for jet flow region, and not affected by the reverse flow. The temperature edge region of planar in the cone-shaped deflector, as well as the central region, is much higher than ambient temperature. The temperature in the edge at Z/D =3 where is closest to the exhaust gas inlet may reach up to 800 K. [Conclusions] By comparative analysis between the four-engine rockets impinging jet on different deflector, the main conclusions are as follow. The region of peak temperature and pressure occurs directly under the rocket nozzle. The wedge-shaped and cone-shaped deflectors have different diversion directions. The maximum pressure and temperature in the wedge-shaped deflector are, respectively, 62% and 18% higher than those in the cone-shaped flame deflector. Compared with the wedge-shaped deflector, the cone-shaped deflector has better performance for deflecting, and increased the distance and optimized the structure of the sidewalls can further improve the exhaust gas flow conductivity. The results provide engineering guidance and theoretical significance for design of the flame deflector of the launch platform.The full version of this extended abstract will appear in Defence Technology in 2020.

Receptivity characteristics of under-expanded supersonic impinging jets

The receptivity of an under-expanded supersonic impinging jet flow at a sharp nozzle lip to acoustic impulse disturbances is investigated as a function of geometric and flow parameters. The under-expanded supersonic jets emanate from an infinite-lipped nozzle, i.e. the nozzle exit is a circular hole in a flat plate. Two specific cases have been investigated corresponding to nozzle-to-wall distances of h = 2d and 5d, where d is the jet diameter, at a nozzle pressure ratio of 3.4 and a Reynolds number of 50 000. Receptivity in this study is defined as originally coined by Morkovin (Tech. Rep. AFFDL TR, 1969, pp. 68-149; see also Reshotko, AGARD Special Course on Stability and Transition of Laminar Flow, N84-33757 23-34) as the internalisation of an external disturbance into the initial condition that either initiates or sustains a vortical fluid dynamic instability. Notionally, receptivity can be considered as a transfer function between the external disturbance and the initial conditions of the vortical instability. In the case of under-expanded supersonic impinging jet flow subjected to an acoustic disturbance, this transfer function is located at the nozzle lip and, thus, is amenable to an impulse response analysis using the linearised compressible three-dimensional Navier-Stokes equations. In this study, the transfer function at the nozzle lip is defined as the ratio of the output flow energy to the input acoustic energy of the acoustic disturbance. The sensitivity of this transfer function to the angular acoustic disturbance location, its azimuthal mode number and Strouhal number has been investigated for the two under-expanded supersonic impinging jet flow cases. It is found that for both the h = 2d and 5d cases, acoustic disturbances located at angles greater than 80° from the jet centreline, with Strouhal numbers in the range between 0.7 and 6.5, have the highest receptivity for all azimuthal mode numbers investigated, except the azimuthal mode number 2 in the case of h = 5d. The case with h = 5d is found to also have high receptivity to acoustic disturbances located at angles between 15° and 50° from the jet centreline for acoustic disturbances of all azimuthal mode numbers.

Flowfield Characteristics of a Supersonic Jet Impinging on an Inclined Surface

The study of the flowfield and noise characteristics of supersonic impinging jets is important as these configurations can be found in many engineering applications, such as short takeoff and landing vehicles, hot surface cooling mechanisms, cold gas dynamic spray processes, and turbomachinery systems. This study experimentally investigates the flowfield characteristics of supersonic jets impinging on an inclined surface with nozzle-to-plate distances of and ( is the jet hydraulic diameter) and nozzle pressure ratios () of 3.7 and 5.9. The two-dimensional two-component velocity fields were acquired in the central plane of the test nozzle and along the 45° inclined impingement surface by using a planar particle image velocimetry (PIV) technique. The flow characteristics of supersonic impinging jets, such as mean velocity and turbulent kinetic energy, were computed from the acquired PIV velocity vector fields, and the statistical profiles were compared to study the effects of the impingement surface and on the flow characteristics. The obtained statistical results have shown the presence of shock cells near the nozzle outlet, oblique plate shocks near the impingement, and tail shocks along the inclined surface. In addition, spatial two-point cross-correlations of turbulent velocity were computed using the PIV velocity vectors to study the sizes, shapes, and orientation of turbulent flow structures in the impinging jets. Finally, a proper orthogonal decomposition analysis was performed on the collections of velocity snapshots extracting the coherent flow structures of a supersonic jet impinging on an inclined surface.

Effects of bevelled nozzles on standoff shocks in supersonic impinging jets

Abstract Moderately under-expanded jets issuing from a circular baseline and two bevelled circular nozzles impinging upon a perpendicular flat plate were experimentally studied. 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. Across all flow configurations arising from the different combinations of these parameters, results indicated that the bevelled nozzles are effective in introducing asymmetry to the standoff shock geometries. Depending on the exact flow configuration, standoff shock locations may also undergo significant upstream displacements. In particular, the single-bevelled nozzle produces highly unsteady standoff shocks with asymmetric oscillation amplitudes along both side of the nozzle lip regions. Changes to the standoff shock key characteristics were observed to be sensitive towards the jet shock structures and reflection point modified by the bevelled nozzle exits. In particular, the strength and relative position of the reflection point are identified as the major contributing factors influencing the upstream static pressure distribution of the standoff shock, hence leading to the observed changes in the standoff shock behaviour.

Mathematical modelling of a single supersonic jet impingement with a flat obstacle

In this paper the mathematical modeling of the interaction of a single supersonic jet with a flat obstacle in a rarefied atmosphere and Mach numbers at the nozzle exit 4 are considered. Mathematical modeling using free OpenFOAM-Extended software and authors’ program are done. Comparison of calculation methods: PISO algorithm, Rusanov and Godunov schemes was carried out. The comparison results show a qualitative coincidence in the shape of the supersonic jet, wall jet and the system of shock waves. But the numerical results are quantitatively different, pressure on flat obstacle varied within 7-14 kPa. The peak of pressure is on the periphery for results of sonicFoam and dbnsFoam. For all solvers average pressure at axis of jet is 8 kPa and the first barrel of wall jet is started about at 0.4 meter from axis was obtained.