Heating enhancement caused by a transverse control jet in hypersonic flow

Parametric study on the sonic transverse jet in supersonic crossflow and analysis of the jet-crossflow interaction instability

This paper presents the effect of blowing (transpiration flow) on hypersonic flow over a flat plate at different flow regimes. The investigation involves the study of the interaction between the free stream flow of argon gas at Mach 5 and transpiring gas introduced at the fluid–solid interface. The freestream Knudsen number considered for the present analysis are 0.002, 0.01, 0.05, and 0.25, extending from continuum to rarefied through transitional flow conditions. Flow simulations are performed using the open source particle-based direct simulation Monte Carlo (DSMC) solver called Stochastic PArallel Rarefied-gas Time-accurate Analyzer (SPARTA). In the DSMC framework, the transpiring gases are introduced as jets with specified velocity, number density, and temperature uniformly throughout the surface in the direction normal to the surface. The variation in flow field properties, such as density, temperature, and velocity with and without transpiration, is studied. The influence of rarefaction on surface heat flux distribution is studied at different flow Knudsen numbers. Furthermore, the effect of introducing the transpiring gas at different densities into the flow field is investigated and its impact on the surface heat flux is discussed. It is interesting to note that in certain cases, the heat flux actually increases locally as a result of the interaction between transpiring gas and freestream flow.

Hypersonic laminar flow past a rearward facing step has been numerically investigated using computational fluid dynamics (CFD). The flow parameters were : total specific enthalpy ho ≈7.6 MJ/kg; unit Reynolds number Re ≈1.82 × 106 1/m ; and Mach number M∞ ≈7.6. A detailed grid independent study has been carried out to investigate the sensitivity of the surface heat flux in the regions of separation and reattachment. The nature of the flow in the close vicinity of the step is particularly emphasised. The influence of real-gas effects such as the thermal and chemical non-equilibrium are studied using Park's two-temperature model and finite-rate chemistry models respectively. The numerical results are then compared with the available experimental data of surface heat flux measurements.

Various methodologies used to derive free-stream conditions in hypersonic wind tunnels using different sets of experimental inputs are reviewed. The accuracy of a relevant but seldom used approach, involving free-stream static pressure measurements, is improved in the present work by solving numerically shock conservation equations and by accounting for the high-temperature effects typically expected in hypersonic flows (vibrational excitation, dissociation, and ionization). The numerical method implemented is also extended to handle free-stream thermal non-equilibrium provided that free-stream vibrational temperature measurements are available. The performances of the present approach are evaluated against conventional methods by determining free-stream flow properties in the von Karman Institute Longshot hypersonic wind tunnel. Uncertainties are quantified for each of the derived free-stream flow conditions. It is demonstrated that methodologies limited to Pitot pressure diagnostics in the test section fail to detect departures from ideal nozzle flow expansions, due to their inherent isentropic flow assumptions. Involving free-stream static pressure diagnostics does, however, improve the results, as validated by independent investigations. It is shown that the non-ideal nozzle flow expansion is not induced by free-stream thermal non-equilibrium since this phenomenon leads to opposite trends on free-stream flow properties with respect to those observed. Overall, free-stream static pressure probes represent a useful complement and their benefits for free-stream rebuilding methodologies are emphasized. The present free-stream rebuilding methodology is recommended to enhance the relevance of every hypersonic ground experiment.

Numerical simulation of scramjet asymmetric nozzle flow is carried out to visualize and investigate the effects of interaction between engine exhaust and hypersonic external flow. The Single Expansion Ramp Nozzle (SERN) configuration studied here consists of flat ramp and a cowl with different combinations of ramp angle and cowl geometry. Using PARAS 3D, simulations are performed for a free stream Mach number of 6.5 that constitutes the external flow around the vehicle. Appropriate specific heats ratio has been simulated for the jet and free stream flow. External shock wave due to jet plume interaction with free stream flow, the internal barrel shock wave and the shear layer emanating from the cowl trailing edge and sidewalls are well captured. Wall static pressure distribution on the nozzle ramp for different nozzle expansion angles has been computed for both with and without side fence. Axial thrust and normal force have been evaluated by integrating the wall static pressure. Effect of cowl length variation and side fence on the SERN performance has also been studied and found to be quite significant. Based on this study, an optimum ramp angle at which the SERN generates maximum axial thrust is obtained. SERN angle of 20o was found to be optimum when the flight axis coincides with nozzle axis.

An experimental investigation is performed on the occurrence of Görtler vortices in a hypersonic flow by means of infrared thermography. A double compression ramp model with varying second ramp angle is tested at Mach 7.5 in a hypersonic Ludwieg tube. Due to the concave curvature of the streamlines in the separated region, a centrifugal instability exists that is responsible for generating stream-wise vortices. In the investigation vortices are generated with varying span- wise wavelengths by means of a comb-shaped element near the nose of the model. Using infrared thermography the amplification of these vortices is measured so that a critical wavelength and Görtler number can be identified. It is found that the vortex growth rate is the highest for the largest second ramp angle. Furthermore it is found that the growth rate decreases with increasing Görtler number.

This study investigates the origin and sustenance of self-induced oscillations of shock structures in a hypersonic flow over a double wedge configuration. Previously, various researchers have considered the double wedge flow configuration for inviscid flow with variations of different inflows as well as geometric parameters such as inflow Mach number ( M ∞), wedge angles, and wedge lengths. Few recently published articles reveal an unsteady flow physics involved with the hypersonic viscous flow for double wedge configuration with large second wedge angles. However, the reason for such self-sustained flow oscillations is not completely clear. The present work seeks out to investigate the origin of such oscillations in a low enthalpy hypersonic flow with different aft-wedge angles and wedge length ratios. In the current study, viscous flow over a double wedge at M ∞ = 7 and fore-wedge angle of 30° is considered. An improved version of rhoCentralFoam solver in OpenFOAM is used to investigate the double wedge flow over different grid resolutions in the separation region and shock–shock interaction region. This study corroborates the observation from the previous literature with an improvement in the range of parameters which results in a self-sustained periodic oscillation. The present study also suggests that the unsteadiness becomes possible when the incidence shock is in the proximity of the aft-wedge expansion corner as a consequence of different wedge length ratios ( L 1 / L 2) or aft-wedge angles (θ2). Flow can still be steady at a large aft-wedge angle if the incidence shock is far ahead of the aft-wedge expansion corner.

A method for combined 3D/1D-modeling of thermohydraulics of a once-through steam generator (SG) based on the joint analysis of three-dimensional thermo- and hydrodynamics of a single-phase heating coolant in the intertube space and one-dimensional thermohydraulics of steam-generating channels (tubes) with the use of well-known friction and heat-transfer correlations under various boiling conditions is discussed. This method allows one to determine the spatial distribution of temperatures and heat fluxes of heat-exchange surfaces of SGs with a single-phase heating coolant in the intertube space and with steam generation within tubes. The method was applied in the analytical investigation of typical operation of a once-through SG of a nuclear power installation with an RBEC fast-neutron heavy-metal reactor that is being designed by Kurchatov Institute in collaboration with OKB GIDROPRESS and Leipunsky Institute of Physics and Power Engineering. Flow pattern and temperature fields were obtained for the heavy-metal heating coolant in the intertube space. Nonuniformities of heating of the steam–water coolant in different heat-exchange tubes and nonuniformities in the distribution of heat fluxes at SG heat-exchange surfaces were revealed.

Experimental investigation of the low subsonic, two-dimensional transverse hot-air jet. In the study jet-to-freestream angles of 90, 120, 135, and 150 deg and jet-to-freestream velocity ratios of 5, 10, and 20 were investigated. In the tests the jet velocity and temperature fields were measured using a temperature-compensated hot-wire anemometer. Photographs of the flowfield were also made. The tests results are compared with the available data and analysis. Results indicate a relatively minor deflection of the freestream by the jet and the presence of a large separated flow region behind the jet.

Hypersonic flow over Stardust Re-entry Capsule using ab-initio based chemical reaction model

In this article, a correlation for the incipient separation angle is presented being valid for laminar boundary layers in supersonic and hypersonic flows. Such correlation is based on physical reasoning and numerical flow simulations whereby the latter were performed for a Mach number range of 1.5 and 15, unit Reynolds numbers of 10 6 1/m to 10 7 1/m and wall temperature ratios of 1.35 to 2.7. The derived correlation was verified with additional numerical simulations featuring different Mach number, wall temperature and Reynolds number combinations compared to the combination employed for the derivation of the correlation. The comparison of the newly developed correlation with correlations of Rizetta et al. (1978), Edelmann et al. (2007), Katzer (1989), Greber et al. (1958), Needham and Stollery (1966), and Holden (1971) shows good agreement within the range of free stream conditions, under which the other correlations had been developed with. The new correlation spans a wide range of free stream conditions thus includes all free stream conditions employed by the researchers mentioned above.

11 Kaufman, L. G., II et al., of Hypersonic Flow Separation and Control Characteristics, ASD-TDR-62-168, March 1962, Grumman Aircraft Engineering Corp., New York. 12 Werle, M. J., A Critical Review of Analytical Methods for Estimating Control Forces Produced by Secondary Injection/' NOLTR 68-5, Jan. 1968, United States Naval Ordnance Lab., White Oak, Md. 13 Hawk, N. E. and Amick, J. L., Two-Dimensional Secondary Jet Interaction with a Supersonic Stream, AIAA Journal, Vol. 5, No. 4, April 1967, pp. 555-660. 14 Zakkay, V., Erdos, J., and Calarese, W., An Investigation of the Interaction Between a Transverse Sonic Jet and a Hypersonic Stream, NYU AA-68-27, Aug. 1968, Aerospace Labs., New York University, N.Y.

A computational study of the counterflow drag reduction by a cold supersonic jet from a hemispherical cylinder at four different hypersonic freestream flows is conducted by solving the unsteady Reynolds-averaged Navier-Stokes (RANS) equations with the two-equation k-ɛ turbulence model. The investigations focused on two different flow regimes, SPM (short penetration mode) → LPM (long penetration mode) and LPM to ensure that the maximum drag reduction is achieved. For the present configuration, the oscillatory flow regime SPM→LPM remains dominant over the most of the pressure ratios at all the freestream flows investigated. A higher drag reduction is obtained for the higher Mach number flows at a constant pressure ratio which can be attributed to the increase in relative mass flow rate of the jet. The physical mechanism suggests that the drag reduction using a counterflow jet with different oncoming freestream flows can be expressed as a function of mass flow ratio. A relation describing the drag reduction at various freestream flows as a function of the relative mass flow rate is proposed.

SummaryThis paper describes an experimental study of the interaction between a hypersonic flow and a transverse jet which issues radially from a slender conical model. Measurements in the region far upstream of the jet show qualitative agreement with free interaction analyses, while downstream a film cooling effect appears to reduce the heat transfer rate substantially. The effect of changes in Reynolds number, jet pressure ratio and mass flux is examined and compared with similar phenomena caused by fixed disturbances such as compression corners. The shape of the interaction shock wave is found to agree with the predictions of the second-order blast wave theory. Finally a correlation is found between the boundary layer separation length and a local mass flux parameter.

The characteristics of arc pressure, current density and heat flux distribution are important factors in understanding physical arc phenomena, which will have a marked effect on the penetration, size and shape of a weld in TIG welding. The purpose of this study is to find out the effect of the heat flux on the melting efficiency and penetration shape in TIG welding using the results of the previous investigators. The conclusions obtained permit to draw a proper method which derived the heat flux distributions by arc pressure distribution measurements, but previous researchers calculated heat flux and current distribution with the heat intensity measurements by the calorimetry. Heat flux of Ar gas arc was concentrated at the central part and distributed low from the arc axis to the radial direction, that of He mixing arc was lower than that of Ar gas, and it was wide distributed to radial direction. That showed a similar characteristic with the Nestor's by calorimetry calculated values. Throughout heat flux drawn in this study was discussed melting efficiency and penetration shape on Ar gas and He mixing gas arc.