Body In Supersonic Flow Research Articles

Shock-related unsteadiness of axisymmetric spiked bodies in supersonic flow

Shock-related unsteadiness over axisymmetric spiked body configurations is experimentally investigated at a freestream supersonic Mach number of 2.0 at 0 $$^\circ $$ angle of attack. Three different forebody configurations mounted with a sharp spike-tip ranging from blunt to streamlined (flat-face, hemispherical, and elliptical) are considered. Steady and unsteady pressure measurements, short-exposure high-speed shadowgraphy, shock footprint analysis from $$x-t$$ plots, and identification of dominant spatiotemporal modes through modal analysis are carried out to explain the unsteady flow physics. The present investigation tools are validated against the well-known events of ‘pulsation’ corresponding to the flat-face case. The hemispherical case is characterized by the formation of a separated free shear layer and associated localized shock oscillations. The cycle of charging and ejection of fluid mass from the recirculation zone is identified to drive the flow unsteadiness. Such an event triggers the movement of the separated and reattachment shocks in the opposite direction with respect to each other (out-of-phase shocks motion). In the elliptical case, the overall flow field resembles that of the hemispherical case, except with dampened unsteadiness. The value of the cone angle ( $$\lambda $$ ) associated with the recirculation region is found responsible for the fluctuations caused by the charging and ejection of fluid mass. Thereby, it controls the extent of out-of-phase shocks motion. In the elliptical case, shock unsteadiness is reduced as $$\lambda $$ is observed to be smaller. Based on the gathered results and understanding, the reduction in unsteadiness associated with the aerodisk mounted on the hemispherical forebody is demonstrated and explained via the almost complete elimination of the out-of-phase shocks motion.

Visualization of asymmetric separation induced by lateral jet interaction on a slender body in supersonic flow

The lateral jet interaction on a slender body in supersonic flow was investigated by numerical simulation. The spatial and surface flow characteristics induced by jet interaction were shown. As a result, when the lateral jet is not in the longitudinal symmetry plane, the jet interaction causes asymmetric separation flow of surface and space, and destroys the pressure distributions of the slender body. With different angle of attack and circumferential positions of jet, the flow characteristic of the after body for jet in asymmetry plane changes greatly. The results with and without jet interaction also show that the far-field interaction played a major role in the lateral jet interaction.

Influences of lateral jet location and its number on the drag reduction of a blunted body in supersonic flows

ABSTRACTThe analysis of the aerodynamic environment of the re-entry vehicle attaches great importance to the design of the novel drag reduction strategies, and the combinational spike and jet concept has shown promising application for the drag reduction in supersonic flows. In this paper, the drag force reduction mechanism induced by the combinational spike and lateral jet concept with the freestream Mach number being 5.9332 has been investigated numerically by means of the two-dimensional axisymmetric Navier-Stokes equations coupled with the shear stress transport (SST) k-ω turbulence model, and the effects of the lateral jet location and its number on the drag reduction of the blunt body have been evaluated. The obtained results show that the drag force of the blunt body can be reduced more profoundly when employing the dual lateral jets, and its maximum percentage is 38.81%, with the locations of the first and second lateral jets arranged suitably. The interaction between the leading shock wave and the first lateral jet has a great impact on the drag force reduction. The drag force reduction is more evident when the interaction is stronger. Due to the inclusion of the lateral jet, the pressure intensity at the reattachment point of the blunt body decreases sharply, as well as the temperature near the walls of the spike and the blunt body, and this implies that the multi-lateral jet is beneficial for the drag reduction.

Drag and heat flux reduction induced by the pulsed counterflowing jet with different waveforms on a blunt body in supersonic flows

The drag and heat flux reduction characteristics plays a very important role in the conceptual design phase and engineering realization of the aerospace vehicle. In the current study, the flow field properties around a blunt body with three different pulsed counterflowing jets in the supersonic flow with the freestream Mach number being 3.98 are investigated numerically. In this paper, there are three different kinds of pulsed jets with the sinusoidal, triangular and rectangular waveforms are established, and the periods of the pulsed jets are all set to be T = 1.0 ms. The jet nozzle is placed at the nose of the blunt body. In the numerical investigation, an axisymmetric numerical simulation model of the counterflowing jet on the supersonic vehicle nose-tip is established, and the two-dimensional axisymmetric Reynolds-averaged Navier-Stokes (RANS) equations coupled with the two equation k-ω shear stress transport (SST) turbulence model are employed. The wall Stanton number distributions, as well as the surface static pressures, are extracted from the flow field structures in order to evaluate the drag and heat flux reduction characteristics. Further, the influence of the pulsed jet waveform on the drag and heat flux reduction is analyzed based on the wall Stanton number and surface pressure distributions. The obtained results show that the variations of the wall Stanton number and surface pressure distributions induced by the pulsed jet with the same period but different waveforms, all have an obvious periodicity and hysteresis phenomenon. At the same time, it is found that the drag and heat flux reduction under the triangular wave has the best effect, and the pulsed jet with the triangular wave has a better comprehensive performance than the other two waveforms.

V-shaped wings with the central body in supersonic flow

The results of a theoretical investigation of the flow pattern of V-shaped wings at supersonic flow velocities are presented. Data are presented on the flow structure near V-shaped wings with a central body in the form of a part of a circular cone within the framework of the ideal gas model. The applicability of the criteria for the existence of nonviscid vortex structures has been determined, but with differences due to the shape of the body. Influence of the central body on the aerodynamic quality of its layout with a V-shaped wing was studied. A significant dependence of geometry of the optimal body on the lift coefficient was established.

Drag and heat flux reduction induced by the pulsed counterflowing jet with different periods on a blunt body in supersonic flows

In the current study, three different kinds of pulsed jets with the period being 0.5 ms, 1.0 ms and 2.0 ms are established, and sinusoidal waveforms are used in all three pulsed jets. The pulsed counterflowing jets with the same amplitude but different periods on the nose of a blunt body in supersonic flows are investigated numerically, and an axisymmetric numerical simulation model of the counterflowing jet on the supersonic vehicle nose-tip is established. The obtained results show that the wall Stanton number and surface pressure change periodically with the pulsed jet, and the variations of the parameters show a strong hysteresis phenomenon. The hysteresis phenomenon becomes less significant as the period increases. At the same time, a better drag and heat flux reduction is obtained under larger period pulsed jet conditions. With the increase of the period of the pulsed jet, there is a significant decline in the maximum peak values of the wall Stanton number and surface pressure. Compared with the steady jet, the pulsed jet is more effective in heat flux reduction, but the drag reduction of the pulsed jet is less effective than the steady jet.

Numerical investigation of drag and heat flux reduction mechanism of the pulsed counterflowing jet on a blunt body in supersonic flows

To design a kind of aerospace vehicle, the drag and heat flux reduction are the most important factors. In the current study, the counterflowing jet, one of the effective drag and heat flux reduction concepts, is investigated numerically by the two-dimensional axisymmetric Reynolds-averaged Navier-Stokes equations coupled with the SST k-ω turbulence model. An axisymmetric numerical simulation mode of the counterflowing jet on the supersonic vehicle nose-tip is established, and the numerical method employed is validated by the experimental schlieren images and experimental data in the open literature. A pulsed counterflowing jet scheme is proposed, and it uses a sinusoidal function to control the total and static pressures of the counterflowing jet. The obtained results show that the long penetration mode does not exist in the whole turnaround, even in a relatively small range of the jet total and static pressures, and this is different from the phenomenon obtained under the steady condition in the open literature. At the same time, it is observed that the variation of the physical parameters, such as the Stanton number induced by the pulsed jet, has an obvious periodicity and hysteresis phenomenon.

Parametric study on the drag and heat flux reduction mechanism of forward-facing cavity on a blunt body in supersonic flows

Drag and heat flux reduction is very important for the design of the hypersonic vehicle, and many novel strategies have been proposed recently. As one of the valid drag and heat flux reduction schemes, the forward-facing cavity has attracted an increasing attention for the scholars. In the current study, the influence of the cavity configuration on the drag and heat flux reduction mechanism of a blunt body has been investigated numerically by the two-dimensional axisymmetric Reynolds-averaged Navier–Stokes (RANS) equations coupled with the SST k–ω turbulence model, and the effects of the depth of the cavity and the angle of its trailing edge have been taken into consideration. At the same time, the numerical approaches employed in this paper have been validated against the available experimental data in the open literature, as well as the grid independency analysis. The obtained results shows that the cavity configuration has only a slight impact on the drag reduction of the blunt body in the supersonic flow with the freestream Mach number being 3.98, and the maximum drag reduction coefficient is within 1.0%. The forward-facing cavity with L/D=4.0 and θ=45° is the most beneficial configuration for the heat flux reduction of the blunt body in the range considered in the current study, and it should be validated by the wind tunnel test in the near future.

Experimental study of flow around axisymmetric bodies in supersonic flow in case of a local injection into the boundary layer

Experimental study of flow around axisymmetric bodies in supersonic flow in case of a local injection into the boundary layer

Dynamical separation of rigid bodies in supersonic flow

A computational investigation of the unsteady separation behavior of rigid bodies in Mach-4 flow is carried out. Two rigid bodies, a sphere and a cube, initially stationary, centroid axially aligned, are released and thereafter fly freely according to the aerodynamic forces experienced. During the separation process, the smaller cube can experience different types of movement and our principal interest here is the non-dimensional transverse velocity of it. The separation behavior is investigated for interactions between a sphere and a cube with different mass ratio and a constant initial distance between them. The qualitative separation behavior and the final transverse velocity of the small body are found to vary strongly with the mass ratio but less sensitive to the initial distance between the two bodies. At a critical mass ratio for a given distance, the smaller body transit from entrainment within the flow region bounded by the larger body’s shock to expulsion and the accumulated transverse velocity of the small body is close to maximum. This phenomenon is the so-called ‘shock-wave surfing’ phenomenon noted by Laurence & Deiterding for two spheres at hypersonic Mach numbers. Then we investigate the separation behavior of a sphere interaction with a rotary cube and with a non-rotary cube for a given mass ratio and different distance between them. The rotary is found to increase the likelihood of ‘surfing’. Only at a certain initial distance for a given mass ratio the rotary effect of cube can be neglectable.

Injection into Supersonic Boundary Layers

A method for injection of gas into the boundary layer on a slender body in supersonic flow while minimizing perturbation to the mean flow is examined. Injection of gas is equivalent to a sudden increase in the displacement thickness of the boundary layer, which produces an oblique shock that propagates into the inviscid region of the flow. It is found that modification of the geometry of the body can compensate for the increased displacement thickness created by injection and minimize the production of oblique waves. However, the resulting near-wall injection layer is observed to be unstable and a turbulent boundary layer develops downstream of the injection region. The instability of the flow is examined experimentally using high-speed schlieren visualization and numerically using linear stability analysis of velocity profiles from a compressible Navier–Stokes computation. At the present postshock Mach number of about 3.8, both first- and second-mode instabilities are active, though computations predict that the first mode is primarily responsible for transition downstream of the injector.

Asymmetrical Lateral Jet Interaction on a Slender Body in Supersonic Flow

The lateral jet interaction on a slender body with rudders in supersonic flow had been investigated by numerical simulation, when the lateral jet is not in the longitudinal symmetry plane. It was called Asymmetrical lateral jet interaction in this paper. The flow features of jet interaction flowfield on the surface of the body or in the space far from the surface at different angles of attack and total pressure of jet was analyzed. As a result, the lateral jet interaction disturbed the pressure distributions of the slender body, and it was divided into near-field interaction near jet and far-field interaction aft-body on the basis of distance to jet. With the variety of the angle of attack and total pressure of jet, the pressure distributions at the aft-body change tempestuously, thereby the normal and lateral load will be from positive to negative, or reverse. The results also showed that the far-field interaction played a major role in the lateral jet interaction on a slender body in supersonic flow. The far-field interaction was caused by the changing of the outflow direction and intensity. Besides, the force/moment amplification factors presented highly nonlinear with the variety of angle of attack and total pressure of jet.

Numerical Simulation of Lateral Jet Interaction a Slender Body in Supersonic Flow

A numerical investigation has been conducted to research the interaction flowfield of lateral jet not in the longitudinal symmetry plane on a slender body with rudders in supersonic flow. The surface and space flow features of jet interaction flowfield with different angles of attack was analyzed. The paper also compared with and without jet interaction flowfield characteristics. As a result, the jet interaction destroys pressure distributions of the slender body, and causes normal and lateral loads. With angle of attack, the pressure distributions of the after body and rudders surfaces are change tempestuously. The results also show that the far-field interference played a major role in the lateral jet interaction. Besides, the force/moment amplification factors present highly nonlinear with angle of attack.

Dynamical separation of spherical bodies in supersonic flow

AbstractAn experimental and computational investigation of the unsteady separation behaviour of two spheres in Mach-4 flow is carried out. The spherical bodies, initially contiguous, are released with negligible relative velocity and thereafter fly freely according to the aerodynamic forces experienced. In experiments performed in a supersonic Ludwieg tube, nylon spheres are initially suspended in the test section by weak threads which are detached by the arrival of the flow. The subsequent sphere motions and unsteady flow structures are recorded using high-speed (13 kHz) focused shadowgraphy. The qualitative separation behaviour and the final lateral velocity of the smaller sphere are found to vary strongly with both the radius ratio and the initial alignment angle of the two spheres. More disparate radii and initial configurations in which the smaller sphere centre lies downstream of the larger sphere centre each increases the tendency for the smaller sphere to be entrained within the flow region bounded by the bow shock of the larger body, rather than expelled from this region. At a critical angle for a given radius ratio (or a critical radius ratio for a given angle), transition from entrainment to expulsion occurs; at this critical value, the final lateral velocity is close to maximum due to the same ‘surfing’ effect noted by Laurence & Deiterding (J. Fluid Mech., vol. 676, 2011, pp. 396–431) at hypersonic Mach numbers. A visualization-based tracking algorithm is used to provide quantitative comparisons between the experiments and high-resolution inviscid numerical simulations, with generally favourable agreement.

Flow control via instabilities, vortices and steady structures under the action of external microwave energy release

The details of flow dynamics during the interaction of a microwave filament (regarded as heated rarefied channel) with an aerodynamic body in supersonic flow are considered. Flow control via the effect on the frontal drag force is discussed. The mechanisms of the drag force reduction for a symmetrically located filament and temporary drag force enhancement for an asymmetrically located filament are established. These mechanisms are attributable to the vortex structures forming via the instabilities in front of the body and inside the shock layer. Three kinds of flow instabilities inside the shock layer are analyzed numerically. These are the Richtmeyer–Meshkov instability, the shear layer instability of Kelvin–Helmholtz type and the instability of a flat-parallel tangential discontinuity. The last instability is shown to be accompanied by generation of steady flow structures. A comparative analysis of the resultant vortices and structures is conducted. Limited length and infinite length filaments are considered. The flowfields are investigated for freestream Mach numbers equal to 1.89 and 3, and a wide range of filament characteristics.

Passive Control of High-Speed Separated Flows Using Splitter Plates

An experimental investigation was conducted to study the effects of passive splitter plates placed in the recirculation region behind a blunt-based axisymmetric body in supersonic flow. The goals of this research were to obtain a better understanding of the physical phenomena that govern these massively separated high-speed flows and to determine the flow-control authority of this passive device. Triangular splitter plates dividing the near wake into 1/2, 1/3, and 1/4 cylindrical regions were designed to exploit specific stability characteristics of this flow, to alter the base pressure, and ultimately to affect base drag. Mean static pressure measurements acquired from the base and splitter plate surfaces were the primary metric to assess the influence of these plates. Schlieren imaging, surface flow visualization, and pressure-sensitive paint measurements were also employed to document the near-wake flowfield, surface flow structure, and surface pressure, respectively. The insertion of these splitter plates only slightly affected the base pressure and near-wake flowfield, which suggests that the recirculation region may not be the most sensitive area to apply this flow control methodology.

Comparison of Lift and Drag Forces for Some Conical Bodies in Supersonic Flow Using Perturbation Techniques

Numerical methods are not always convergent especially in higher velocities when shock waves are involved. A comparison analysis is performed to study the supersonic flow over conical bodies of three different cross sections circular, elliptic and squircle (square with rounded corners) shaped using Perturbation techniques to find flow variables analytically. In order to find lift and drag forces the pressure force on the body is found, the component along x is drag and the component along z is lift. Three equations are obtained for lift to drag ratio of each cross section. The graphs for L/D show that for a particular cross section an increase in angle of attack, increases L/D. Comparing L/D in the three mentioned cross sections depicted that L/D is the greatest in squircle then in ellipse and the least in circle. The results are efficient in design of flying objects.

Effect of mesh screens on the wave drag of a blunt body in supersonic flow

Results of an experimental study of the effect of flat mesh screens on the wave drag of a cylinder with flat face longitudinally streamlined with supersonic airflow at Mach number M = 4.85 are reported. Data on reducing the drag by meshes of various geometries and transparencies installed ahead of the cylinder face were obtained. Weighing and pneumometric measurements, and also PIV measurements of the vector velocity field, are reported. The flow pattern in the vicinity of the cylinder/screen system is visualized. It is shown possible to achieve a substantial (up to 45 %) reduction of the wave drag of the cylinder with a mesh screen. A physical interpretation to the wave-drag reduction phenomenon is given.

Computational and experimental investigation into aerodynamic interference between slender bodies in supersonic flow

Aerodynamic interference can occur between high-speed bodies when in close proximity. A complex flowfield develops where shock and expansion waves from a generator body impinge upon the adjacent receiver body and modify its aerodynamic characteristics. The aims of this paper are to validate a computational prediction method, to use the predicted solutions to interpret the measured results and to provide a deeper understanding of the associated flow physics. The interference aerodynamics for two slender bodies were investigated through a parametric wind tunnel study where the effect of axial stagger was investigated for different receiver body incidence angles. Measurements included forces and moments, surface pressures and shadowgraph visualisations. Supporting computational predictions provided a deeper understanding of the underlying aerodynamics and flow mechanisms. Good agreement was found between the measured and predicted interference loads and surface pressures for all configurations. The interference loads are strongly dependent upon the axial impingement location of the primary shockwave. These induced interference loads change polarity as the impingement location moves aft over the receiver. Distinct interference characteristics are observed when the receiver is placed at high positive incidence, where the impinging shock has a strong effect on the crossflow separation location. Overall, the observed interference effects are expected to modify the subsequent body trajectories and may increase the likelihood of a collision.

Pulsating stochastic flows accompanying microwave filament/supersonic shock layer interaction

The details of pulsating stochastic flows accompanying the interaction of a microwave filament (regarded as a heated rarefied channel) and an aerodynamic body in supersonic flow are examined numerically using the Euler equations. Symmetrical and asymmetrical filament locations relative to the aerodynamic body are considered. The flowfields are characterized by large scale pulsations and small scale stochastic fluctuations. The mechanisms of the formation of these flow structures are discussed. Two qualitatively different kinds of flowfields are observed depending on the magnitude of the filament radius, with domination of the pulsations of flow parameters or stochastic phenomena. Flow instabilities inherent to the problems under interest are described. The problems are considered in both plane and cylindrical configurations for a wide class of filament characteristics and freestream Mach numbers equal to 1.89 and 3.