Showing papers on "Supersonic speed published in 1971"
TL;DR: In this paper, the transonic small disturbance theory is used to solve for the flow past thin airfoils including cases with imbedded shock waves, and a boundary value problem is formulated for the case of a subsonic freestream Mach number.
Abstract: Transonic small disturbance theory is used to solve for the flow past thin airfoils including cases with imbedded shock waves. The small disturbance equations and similarity rules are presented, and a boundary value problem is formulated for the case of a subsonic freestream Mach number. The governing transonic potential equation is a mixed (elliptic-hyperbolic) differential equation which is solved numerically using a newly developed mixed finite difference system. Separate difference formulas are used in the elliptic and hyperbolic regions to account properly for the local domain of dependence of the differential equation. An analytical solution derived for the far field is used as a boundary condition for the numerical solution. The difference equations are solved with a line relaxation algorithm. Shock waves, if any, and supersonic zones appear naturally during the iterative process. Results are presented for nonlifting circular arc airfoils and a shock free Nieuwland airfoil. Agreement with experiment for the circular arc airfoils, and exact theory for the Nieuwland airfoil is excellent.
651 citations
TL;DR: Turbulent skin friction and heat transfer prediction on flat plates and wind tunnel walls at supersonic and hypersonic Mach numbers, using Van Driest theory, was performed by.
Abstract: Turbulent skin friction and heat transfer prediction on flat plates and wind tunnel walls at supersonic and hypersonic Mach numbers, using Van Driest theory
284 citations
TL;DR: There have been many attempts to reduce or eliminate the sonic boom for supersonic aircrafts such attempts fall into two categories: aerodynamic minimums and exotic configurations In the first category, changes in entropy and the Bernoulli constant are neglected, and equivalent body shapes required to minimize the overpressure, the shock pressure rise, and the impulse are deduced as discussed by the authors.
Abstract: There have been many attempts to reduce or eliminate the sonic boom For supersonic aircrafts such attempts fall into two categories: (1) aerodynamic minimums and (2) exotic configurations In the first category, changes in entropy and the Bernoulli constant are neglected, and equivalent body shapes required to minimize the overpressure, the shock pressure rise, and the impulse are deduced These results include the beneficial effects of atmospheric stratification In the second category, the effective length of the aircraft is increased by modifying the Bernoulli constant a significant fraction of the flow past the aircraft A figure of merit is introduced which makes it possible to judge the effectiveness of such schemes Finally, the sonic boom reductions that can be achieved by hypersonic flight at high altitudes are summarized
163 citations
TL;DR: In this paper, a theory on the generation mechanism of directional acoustic radiation from a supersonic jet is proposed based on the concept of instability of the shear layer at the boundary of the jet close to the nozzle.
Abstract: A theory on the generation mechanism of directional acoustic radiation from a supersonic jet is proposed. The theory is based on the concept of instability of the shear layer at the boundary of the jet close to the nozzle. Theoretical prediction of the directional wave pattern is found to agree with shadowgraphic observation.
139 citations
TL;DR: Viscous flow in supersonic de Laval nozzle, measuring gas density and rotational temperatures by electron beam techniques as discussed by the authors, was used to measure gas density in the de Lval nozzle.
Abstract: Viscous flow in supersonic de Laval nozzle, measuring gas density and rotational temperatures by electron beam techniques
134 citations
28 Mar 1971
TL;DR: In this article, a time-dependent formulation of the equations of motion is used to predict steady transonic flow through two-dimensional gas turbine cascades using a time dependent formulation.
Abstract: Steady transonic flow through two-dimensional gas turbine cascades is efficiently predicted using a time-dependent formulation of the equations of motion An integral representation of the equations has been used in which subsonic and supersonic regions of the flow field receive identical treatment Mild shock structures are permitted to develop naturally without prior knowledge of their exact strength or position Although the solutions yield a complete definition of the flow field, the primary aim is to produce airfoil surface pressure distributions for the design of aerodynamically efficient turbine blade contours In order to demonstrate the accuracy of this method, computed airfoil pressure distributions have been compared to experimental resultsCopyright © 1971 by ASME
124 citations
01 Mar 1971
TL;DR: In this article, the effects of jet to free-stream dynamic pressure ratio effects on penetration and mixing of hydrogen injected normal to supersonic airstreams were investigated. But the authors focused on the effect of the pressure ratio on the mixture of hydrogen and fuel.
Abstract: Jet to free-stream dynamic pressure ratio effects on penetration and mixing of hydrogen injected normal to supersonic airstreams
101 citations
TL;DR: In this article, the authors describe an interpretation of jet-noise theory and scale-model experiments to highlight physical properties of jet noise sources at very high speed. And they postulate a model of the noise generating motions as the instability products of a jet flow of low equivalent Reynolds number.
Abstract: The paper describes an interpretation of jet-noise theory and scale-model experiments to highlight physical properties of jet-noise sources at very high speed. The study is prompted by current efforts to suppress the noise of supersonic transport aircraft.The principal noise sources are shown to be very large-scale wave-like undulations of the jet flow that travel downstream at supersonic speed for a distance of several jet diameters. These motions are relatively well ordered and are probably more akin to recognizable instabilities of a laminar flow than the confused small-scale turbulence. Because of this we postulate a model of the noise generating motions as the instability products of a jet flow of low equivalent Reynolds number. This Reynolds number is based on an eddy viscosity and can be further reduced by artificially increasing the small-scale turbulence level. This step would tend to stabilize the flow and inhibit the formation of large-scale noise producing eddies.
93 citations
TL;DR: In this article, the authors reviewed the physical mechanisms involved in each of these processes, including the generating of unsteady lift by turbulence, and compared the sound power estimates, where possible, with experiment results.
Abstract: Experiments and theory relating to fan noise sources are reviewed with emphasis on axial flow machines At supersonic rotor speeds, the steady shock pattern attached to a rotor is an efficient radiator of sound In most practical cases of subsonic rotor operation, however, direct radiation from the rotor‐locked pressure field is negligible compared with the indirect radiation, or scattering, caused by circumferential distortions in the steady flow field surrounding the rotor Random timewise modulation of the distortion changes the scattered spectrum from discrete to continuous, with a gradual progression from narrow‐band tones to broad‐band noise as the modulation bandwidth is increased Similar scattering occurs when a non‐uniform unsteady flow impinges on stator vanes, but here the radiated frequency is that of the impinging flow Finally, for blades operating in flows free from circumferential distortions, self‐generated turbulence becomes an important source of noise The paper describes the physical mechanisms involved in each of these processes, including the generating of unsteady lift by turbulence Order‐of‐magnitude sound power estimates are compared, where possible, with experiment
91 citations
01 Sep 1971
TL;DR: Mixing of hydrogen downstream from multiple injectors normal to supersonic jet flow for SU-personic combustion on ramjet engines was studied in this paper, where it was shown that the mixture of hydrogen and fuel can improve the performance of the ramjet engine.
Abstract: Mixing of hydrogen downstream from multiple injectors normal to supersonic jet flow, for supersonic combustion on ramjet engines
80 citations
01 Mar 1971
TL;DR: In this paper, a comprehensive set of measurements was made in a ballistic range which permits the sphere drag coefficient to be derived with an uncertainty of approximately +2 or -2 percent in the flight regime 0.1 < M < 6.0 and 20 < Re < 100,000 for Tw/T approx = 1.0.
Abstract: : A comprehensive set of measurements was made in a ballistic range which permits the sphere drag coefficient to be derived with an uncertainty of approximately +2 or -2 percent in the flight regime 0.1 < M < 6.0 and 20 < Re < 100,000 for Tw/T approx = 1.0. Sufficient information is also presented to predict the effect of wall temperature on sphere drag coefficient when Tw/T is not = 1.0 for 2 < M < 6. This investigation represents the most comprehensive experimental program to date to define sphere drag in the velocity-altitude regime applicable to the falling sphere technique for defining upper air density.
TL;DR: In this paper, the prediction techniques for the calculation of sonic booms produced by rather complex conventional supersonic aircraft designs performing level nonaccelerated flight in a quiet atmosphere are reviewed.
Abstract: Within the past two decades, the combined contributions of scientists and engineers in this country and abroad have resulted in development of systematic and reliable methods for the prediction of sonic‐boom phenomena. The prediction techniques reviewed in the present paper permit the calculation of sonic booms produced by rather complex conventional supersonic aircraft designs performing level nonaccelerated flight in a quiet atmosphere. It has been found that the calculated characteristics for a quiet atmosphere are representative of nominal conditions in a statistical sense for a real atmosphere. Basic concepts of supersonic flow analysis, for representation of an airplane as a linear distribution of disturbances and for determination of the resultant pressure field complete with shocks, are outlined. Numerical techniques for implementation of the theory are discussed briefly, and examples of the correlation of theory with experimental data from wind tunnel and flight tests are presented. Special attention is given to presentation of a simplified method for rapid “first‐cut” estimation of farfield bow‐shock overpressure. Finally, some problems encountered in attempts at applying the prediction techniques for the nearfield at high supersonic Mach numbers are recognized, and the need for further refinement of present techniques or the development of new systems is discussed.
Patent•
30 Aug 1971
TL;DR: In this paper, a combustible mixture of air and minute fuel droplets is produced for supply to the cylinders of an internal combustion engine, which is formed by accurately controlling both the atomization of fuel and the mass flow rate of air over substantially the entire operating range of the engine.
Abstract: A combustible mixture of air and minute fuel droplets is produced for supply to the cylinders of an internal combustion engine. This mixture is formed by accurately controlling both the atomization of fuel and the mass flow rate of air over substantially the entire operating range of the engine. These controls are accomplished by introducing liquid fuel into a stream of intake air and uniformly distributing the fuel in the air followed by passing the air and fuel mixture through a constricted zone to increase the velocity of the mixture to sonic. The sonic velocity air at the constricted zone divides the fuel into minute droplets that are uniformly entrained throughout the air stream. The area of the constricted zone and the quantity of fuel introduced are adjustably varied in correlation with operating demands imposed upon the engine. Downstream from the constricted sonic zone, the air and fuel mixture is accelerated to supersonic velocity in a supersonic zone without imparting substantial turbulent flow thereto. Thereafter the mixture is decelerated to subsonic velocity in a subsonic zone to produce a shock zone where the fuel droplets entrained in the air are believed to be further subdivided and uniformly distributed throughout the combustible mixture before the mixture is supplied to the engine cylinders. The supersonic and subsonic velocities occur in a gradually increasing cross-sectional area corresponding to that of a conical section having an apex angle in the range of about 6* to 18*. Operation of the engine with such a combustible mixture results in substantially reduced levels of undesirable exhaust emissions, and also permits operation of high compression ratio engines on relatively low octane fuel with good power and fuel economy characteristics. Additionally, misfire does not occur even when the engine is operated on relatively lean air-fuel ratios.
TL;DR: In this paper, experimental and analytical results are presented with the objective of denning the mechanism of liquid sheet and j et al. breakup when subj ected to a supersonic gas stream.
Abstract: Experimental and analytical results are presented with the objective of denning the mechanism of liquid sheet and j et breakup when subj ected to a supersonic gas stream. Liquid sheets are studied with photomicrographs and high-speed movies of the activity of a liquid layer maintained upon a porous plate test model in a parallel Macli 2.2 freestream. Tests with several different liquids show wave motion, with droplet and ligament shedding across the liquid surface. Numerical results from a liquid surface stability analysis are used to explain these observations. Liquid jets are studied with spark shadowgraphs, high-speed movies and photomicrographs of the normal injection of various liquids into a Mach 2.1 freestream. The results show that the breakup mechanism is characterized by gross jet fracture, as opposed to surface disintegration. 'the degree of breakup at a given streamwise location and jet spread after injection are found to be related to injection diameter and dynamic pressure, and certain liquid properties.
TL;DR: In this paper, a two-stage transonic research compressor has been investigated experimentally over a range of tip relative Mach numbers up to 1.56 and the results show that the phenomenon is due to the propagation at supersonic relative tip speeds of the steady rotating pressure field associated with the first-stage rotor blades.
Abstract: The buzz-saw noise made by a two-stage transonic research compressor has been investigated experimentally over a range of tip relative Mach numbers up to 1.56. The results show that the phenomenon is due to the propagation at supersonic relative tip speeds of the steady rotating pressure field associated with the first-stage rotor blades. The flow entering the tip section of the rotor has been analyzed theoretically and the circumferential pressure fluctuations computed, with good agreement with near-field measurements. The analysis leads to a clearer understanding of the dependence of the noise on inlet Mach number and three-dimensional effects and indicates the types of rotor irregularity which will most influence the harmonic content.
01 Jan 1971
TL;DR: Combustion physics and ignition of hydrogen in supersonic stream of vitiated air or inert gases using stepped-wall injection procedure was discussed in this article, where the authors proposed a step-wise injection procedure.
Abstract: Combustion physics and ignition of hydrogen in supersonic stream of vitiated air or inert gases using stepped-wall injection procedure
Patent•
14 Jun 1971TL;DR: In this paper, the penetration of a gaseous jet injected through a bounding wall into a sonic or supersonic cross flow is controlled by modification of the approach flow boundary layer.
Abstract: The penetration of a sonic or supersonic gaseous jet injected through a bounding wall into a sonic or supersonic cross flow is controlled by modification of the approach flow boundary layer. Penetration is increased when the separation pressure is reduced by disturbing the approach flow boundary layer. Both transpiration of small amounts of gas into the boundary layer, and positioning a trip or blockage element upstream of the injection station, will produce increased penetration.
TL;DR: In this article, an interaction theory for supersonic separated andreattaching turbulent boundary layers is presented and compared with recent experiments for flow past a compression ramp, where the effects of ramp angle, Mach number, Reynolds number, and upstream pressure gradient are considered for situations where the critical point is located upstream of the trailing edge.
Abstract: Results of an interaction theory for supersonic separated andreattaching turbulent boundary layers are presented and compared with recent experiments for flow past a compression ramp. Effects of ramp angle, Mach number, Reynolds number, and upstream pressure gradient are considered for situations where the critical point is located upstream of the trailing edge. When the critical point falls downstream of the trailing edge the whole region of separated flow is influenced by ramp length. In these "short ramp" flows the peak ramp pressure attains a maximum at a critical ramp angle and then decreases with increasing angle. It is shown that this effect is responsible for the spanwise pressure distributions measured by Whitehead and Keyes for flow over a delta wing with a trailing edge flap. Results are also presented for a turbulent boundary layer-shock wave interaction.
TL;DR: In this article, the authors studied the field radiated by an acoustic monopole in the presence of an infinite membrane, or plate, with emphasis on the case when fluid loading effects are small and when a free wave in the surface has supersonic phase speed relative to the fluid.
Abstract: The field radiated by an acoustic monopole in the presence of an infinite membrane, or plate, is studied, with emphasis on the case when fluid loading effects are small and when a free wave in the surface has supersonic phase speed relative to the fluid. Coupling between fluid and surface is then specified by a Mach angle θM and by a fluid loading parameter e, with e [Lt ] 1. Asymptotic expressions for the field are derived which are uniform in the observation angle θ, measured from the surface. Previous descriptions have suggested the formation of a strong two-dimensional beaming effect along the surface of the Mach cone θ = θM. Here it is shown that this effect is a spurious consequence of nonuniform asymptotics. A beam is indeed formed, and persists without attenuation or distortion to large distances k0R ∼ e−2. However, the beam amplitude is small compared with that of the three-dimensional reflected field, while at distances k0R [Gt ] e−2 only the reflected wave survives. Some interesting features of the reflexion coefficient and of the field near to the membrane are also discussed. In particular, it is shown that the pressure field generated by a subsonic surface wave is also confined to a conical zone, the transition across the generators of the cone being described by Fresnel functions of a familiar kind.
30 Nov 1971
TL;DR: In this article, a comparative study of numerical procedures for computing solid wall boundary points in supersonic inviscid flow calculatons is presented, along with complications for three-dimensional and time-dependent flows.
Abstract: Results are given of a comparative study of numerical procedures for computing solid wall boundary points in supersonic inviscid flow calculatons. Twenty five different calculation procedures were tested on two sample problems: a simple expansion wave and a simple compression (two-dimensional steady flow). A simple calculation procedure was developed. The merits and shortcomings of the various procedures are discussed, along with complications for three-dimensional and time-dependent flows.
TL;DR: Kernel function for nonplanar oscillating surfaces in supersonic flow, using finite element method for interfering configurations as mentioned in this paper, is a kernel function based on the kernel function for the non-planar ODE.
Abstract: Kernel function for nonplanar oscillating surfaces in supersonic flow, using finite element method for interfering configurations
TL;DR: The application of laser anemometry to the study of turbulent supersonic flow is discussed in this paper, where it is shown that the direct frequency method of measurement of the Doppler shift in frequency undergone by light scattered from flow borne particles using a single frequency laser and a Fabry-Perot interferometer has significant advantages over optical heterodyning.
Abstract: The application of laser anemometry to the study of turbulent supersonic flow is discussed. An analysis is presented showing that the direct frequency method of measurement of the Doppler shift in frequency undergone by light scattered from flow borne particles using a single frequency laser and a Fabry-Perot interferometer has significant advantages over optical heterodyning. It is shown that a confocal rather than a plane Fabry-Perot used in conjunction with an argon laser is the most suitable instrumentation for this application. Preliminary results are presented of measurements made on a supersonic wind tunnel and a free jet.
TL;DR: In this paper, the effect of the boundary layer's thickness on the dynamics of viscous hypersonic flow has been studied in detail in the first volume of the Annual Review of Fluid Mechanics ( 1969).
Abstract: The flow of gas at hypersonic speed near a solid surface leads to the forma tion of a boundary layer whose thickness significantly exceeds (at the same Reynolds number) the thickness of the boundary layer formed at moderate supersonic speeds. The reason for this is the high temperature level and the consequent low density and high coefficient of viscosity in the hypersonic boundary layer. As a result, the effect of viscosity at high supersonic speeds is not confined to the interior of the boundary layer, and leads to substantial changes in the entire flow field. In the first place this is associated with the displacement effect of the boundary layer, which changes the "effective" shape of the body. Furthermore, thickening of the boundary layer can pro duce changes in the character of the flow in the boundary layer itself, as a result of the effect of the vorticity of the outer stream, the increased role of the transverse curvature of the surface, etc. All these effects are usually studied on the basis of the theory of inter action of the boundary layer with the outer stream, that is, on the basis of simultaneous consideration of the flow field in the boundary layer and the outer inviscid stream. In cases when the boundary-layer thickness is of an order of magnitude significantly smaller than the thickness of the body, the situation in the first approximation does not differ from the classical one, that is, the outer stream may, in the first approximation, be regarded as independent of the boundary layer. In this case of so-called weak interaction, the problem of studying the influence of the boundary layer upon the outer flow field and secondary effects in the boundary layer itself reduces to the investigation of higher approximations in boundary-layer theory. However if the body is so slender that the boundary layer has comparable or greater thickness, the effects of interaction may determine all functions of the flow field in their leading terms. The study of such cases constitutes the theory of moderate or strong interaction of the boundary layer with the outer stream. This last development has a central place in the present survey, because the theory of higher approximations for a boundary layer is treated in detail in the article by Van Dyke in the first volume of Annual Review of Fluid Mechanics ( 1969). We devote attention primarily to investigations carried out within the last decade, since the earlier period of development of the theory of viscous hypersonic flow is described in detail in the book of Hayes & Probstein (1959a).
TL;DR: Plate excitation by supersonic turbulent and shock boundary layers, measuring wall pressure fluctuation and panel displacement as mentioned in this paper, was used to measure wall pressure fluctuations and panel displacements.
TL;DR: In this paper, a small curvature radius/throat radius ratio supersonic nozzles mass flow rate coefficients at high Reynolds numbers, appraising isentropic flow prediction methods are presented.
Abstract: Small curvature radius/throat radius ratio supersonic nozzles mass flow rate coefficients at high Reynolds numbers, appraising isentropic flow prediction methods
01 Apr 1971
TL;DR: Finite difference calculation based on eddy diffusivity and mixing length flow theory to characterize supersonic turbulent boundary layer with tangential slot injection was performed in this article, which is based on the mixing length theory.
Abstract: Finite difference calculation based on eddy diffusivity and mixing length flow theory to characterize supersonic turbulent boundary layer with tangential slot injection