Showing papers on "Supersonic speed published in 1983"

The Impact of Compressible Liquids

Abstract: Consideration is given to liquid impact in the supersonic regime in order to characterize pressure loading and other mechanisms which could damage a solid target such as a jet in flight. The liquid ...

Constant temperature hot-wire anemometer practice in supersonic flows

Abstract: The performance of a constant-temperature normal hotwire in a supersonic flow is critically examined. It is shown that this instrument is inherently unsuitable for measuring turbulent temperature correlations because of the highly non-linear response to temperature fluctuations, particularly at low overheat ratios. The instrument is therefore limited to measurements of mean and fluctuating mass-flow rates. Suitable calibration procedures. as well as the limits on spatial and temporal resolution are discussed. and corrections for mean stagnation temperature changes are suggested. The instrument was used to measure the mass-flow fluctuations in a zero pressure gradient Mach 2.9 turbulent boundary layer. A comparison with the available data suggests good agreement.

Dynamics of Air Combat

Abstract: New short- and medium-range air-to-air weapons have been analyzed by means of computerized and manned air combat simulation. As a result of their peculiar capabilities, air combat maneuver characteristics are expected to change significantly. The all-aspect capability of new short-range weapons leads to a dominance of head-on engagements and thus to an increase of importance of instantaneous maneuver capability over the classical sustained performance. Typical flight conditions are analyzed in terms of turn rates, rates of climb and rates of longitudinal acceleration and in terms of the resulting power and energy management. The guidance and performance capabilities of new medium-range weapons lead to a maneuvering-type combat in the supersonic speed regime. Typical flight conditions and power/energy management characteristics of medium range air combat engagements are analyzed similar to short-range combat and mutually compared. Finally, the impact on fighter design requirements is discussed. Nomenclature D = level flight drag E - total energy g = gravity h = altitude MR = medium range SR = short range t = time T = propulsive thrust V = speed of flight Vs = sink/climb speed W - aircraft weight AD = drag increment due to turning SEP = specific excess power

Compressible Helicoidal Surface Theory for Propeller Aerodynamics and Noise

Abstract: Acceleration potential techniques from three-dimensional thin wing theory have been generalized for propeller and prop-fan analysis. Helicoidal reference surfaces take the place of the planar surface in wing theories; otherwise the theories are equivalent. The acoustic branch of the theory, including nonlinear source terms, extends and unifies frequency domain noise theories dating back to Gutin. For aerodynamic applications, it is shown that prop-fans satisfy well-known criteria for use of linearized theory at transonic speeds by virtue of small aspect ratio and small thickness ratio. The results are in the form of integral equations for downwash as functions of thickness and steady or unsteady loading distributions. For the case of no rotation, the kernel functions reduce to well-known kernels of wing theory. The analysis, within the restrictions of linearization , treats rigorously any planform and any flight condition including the combination of subsonic roots and supersonic tips typical of prop-fans. The effects of thickness, camber, angle of attack, sweep, offset, blade interference, and tip relief are all treated without approximation.

Computation of supersonic viscous flows around pointed bodies at large incidence

Abstract: A recently reported parabolized Navier-Stokes method has been extended to compute turbulent supersonic flows around cones and an ogive-cylinder body at large incidence. The algebraic eddy-viscosity turbulence model contained in the code was modified to properly account for the large regions of cross-flow separation that occur in these flows. Extensive comparisons between computed results and experimentally measured flow fields are presented. The results show good agreement for viscous-layer profiles and details of the external leeward-side vortex structure at angles of attack up to three times the cone half angles. Details of the modified turbulence model are presented and discussed.

Third-harmonic generation in a pulsed supersonic jet of xenon.

Abstract: Third-harmonic generation to 1182 A is reported in a pulsed supersonic jet of xenon. Using a valve equipped with a 1-mm-diameter nozzle and for an incident power of 18 MW at 3547 A, I have obtained a peak power of 260 W in a 2.9-nsec pulse, corresponding to 4.7 x 10(11) photons per pulse and an average power of 7.5 microW at 1182 A. The measured conversion efficiency is comparable with that in a bulk-gas cell.

Thrust Augmenting Ejectors, Part I

Abstract: The solution of the equations representing the flow of a compressible fluid through an ejector has been shown to possess two distinctly different results after complete mixing. Part I of this study reported the analysis and described the performance of ejectors configured under the first solution where the flow after mixing is subsonic. The second solution to the ejector flow equations where the flow after mixing is supersonic provides a basis for selection of an optimal and a limiting ejector configuration for any given set of flight and injected gas characteristics. These special ejector configurations provide very high ideal thrust augmentations while translating from zero to supersonic velocities. Maps showing this ideal performance over large ranges of flight and injected gas characteristics are presented. Consideration is given to the influence of realistic, nonisentropic outlets as required for starting the supersonic flow (swallowing the starting shock wave) and for return of the supersonic mixed flow to ambient pressure. The data presented are limited to ejectors having a constant area mixing duct whose cross section is equal to 25 times that of the minimal area of the exhaust flow from the gas generator.

Aeroelastic characteristics of a cascade of mistuned blades in subsonic and supersonic flows

Abstract: An investigation of the effects of mistuning on flutter and forced response of a cascade in subsonic and supersonic flows is presented. The aerodynamic and structural coupling between the bending and torsional motions and the aerodynamic coupling between the blades are included. It is shown that frequency mistuning always has a beneficial effect on flutter. Additionally, the results indicate that frequency mistuning may have either a beneficial or an adverse effect on forced response, depending on the engine order of the excitation and Mach number.

Flow visualization methods for separated three-dimensional shock wave/turbulent boundary-layer interactions

Abstract: A collection of techniques is presented for the visualization of separated turbulent flows at high speeds. Some of these techniques—including a method of generating a localized vapor visualization—have not been available previously. Others, such as the conical shadowgraph and stereoscopic schlieren methods, have been used before in other contexts. Here, all the available techniques are applied to the study of three-dimensi onal supersonic flows generated by swept compression corners. The paper discusses the techniques and some of the fluid mechanical insights revealed by the visualizations, including the structure of the observed three-dimensional flow separations and associated shock wave systems.

Shock-associated noise in supersonic jets

Abstract: This paper examines the fundamental mechanism of broadband shock noise in an improperly expanded supersonic jet. The study includes circular convergent and convergent-divergent nozzles. The main source of shock noise is determined to be the transient interaction between the shock front and the convected vorticity within the jet plume. The discussion of the noise generation mechanism is based on detailed numerical analysis, theoretical modeling, refined measurements of the jet mean flow, shock-cell structure, turbulence, and noise. Results in this study provide a broad-based generalization for the Harper-Bourne and Fisher analysis and prediction method.

Thrust augmenting ejectors, II

Abstract: : A discussion of the development of the compact jet-diffuser ejectors utilized for hovering and low speed flight propulsion has been presented This is followed by a description of ideal ejector performance as derived from a compressible flow theory, over the range of flight speeds from zero to supersonic speed These analyses introduced the concepts of ejector configuration optimization and the validity of the so-called 'second solution' to the mixing problem, wherein the flow after complete mixing is supersonic The ideal performance of thrust augmenting ejectors designed under this 'second solution' has been shown to be far superior to those designed by conventional methods The ability of properly designed ejectors to utilize the thermal energy of injected gas for the production of useful energy has also been described Finally, the influence of major losses has been discussed, including means for avoiding excessive performance degradation by proper optimization of the geometry of the ejector in view of these losses

Supersonic flow over a rearward facing step with transverse nonreacting hydrogen injection

Abstract: This work involves an application of computational fluid dynamics to a problem associated with the flow in the combustor region of a supersonic combustion ramjet engine (Scramjet). In particular, a time-dependent, finite difference method is used to. solve the complete two-dimensional Reynolds averaged Navier-Stokes equations for the turbulent supersonic flow of air over a rearward-facing step, with transverse H2 injection downstream of the step. To delineate the purely fluid dynamic effects, the flow is treated as nonreacting; however, detailed binary diffusion of H2-air is included, along with a variable Lewis number. Results are obtained and compared for cases with and without H2 injection. The influence of the wall temperature boundary conditions (adiabatic vs constant temperature) is studied, and is shown to have little impact on the flow both near and far away from the wall. These numerical results are the first to be obtained for this flow geometry, expecially at,conditions germaine to a Scramjet. They demonstrate that such an application of computational fluid dynamics can be useful for the study of inlet-combustor interactions, and the flameholding potential of the rearward-facing step.

A nonintrusive laser interferometer method for measurement of skin friction

Abstract: A method is described for monitoring the changing thickness of a thin oil film subject to an aerodynamic shear stress using two focused laser beams. The measurement is then simply analyzed in terms of the surface skin friction of the flow. The analysis includes the effects of arbitrarily large pressure and skinfriction gradients, gravity, and time-varying oil temperature. It may also be applied to three-dimensional flows with unknown direction. Applications are presented for a variety of flows including two-dimensional flows, three-dimensional swirling flows, separated flows, supersonic high-Reynolds-number flows, and delta-wing vortical flows.

On the time required to reach fully developed flow in pulsed supersonic free jets

Abstract: A new and simple model is presented for estimating the minimum pulse duration (‘‘valve open time’’) required for a pulsed nozzle to produce a supersonic beam comparably ‘‘cold’’ to that obtained from a continuous source. The model is based on the notion that cooling will be complete if the leading edge of the beamlet reaches the terminal temperature prescribed by the steady state flow equations before the sound wave created at the back of the pulse by the nozzle’s closing catches up with the leading edge. The times predicted from this model for reasonable stagnation conditions are all ≲10 μs.

Store separation from cavities at supersonic flight speeds

Abstract: An experimental investigation has been conducted to determine the aerodynamic characteristics of a typical wing-control missile configuration during separation from a box-type cavity having depth to length ratios (D/L) ranging from 0.088 to 0.225. The cavity was located in a splitter plate that spanned the low Mach number test section of the Langley Unitary Plan Wind Tunnel. Aerodynamic characteristics are presented for Mach 2.36 and a free-stream unit Reynolds number of 2,000,000/ft. For the shallow cavity (D/L = 0.088), large interactions existed between the cavity and the flat plate flow field, which resulted in unfavorable separation characteristics for the missile model. For the deep cavity (D/L = 0.225), the flat plate flow field essentially bridged the cavity, resulting in minor interactions and favorable separation characteristics for the missile model.

Supersonic-nitrogen flow-field measurements with the resonant Doppler velocimeter

Abstract: Laser‐induced fluorescence of sodium atoms seeded into a supersonic nitrogen jet is used to determine the velocity, temperature, and pressure of the flow. The visible signal is sufficiently intense for spatially resolved flow visualization purposes.

Computation of nonequilibrium, supersonic three-dimensional inviscidflow over blunt-nosed bodies

Abstract: Subscripts B A computer code based on the method of characteristics is applied to the study of twoand three-dimensional chemical nonequilibrium flow over sharpand blunt-nosed bodies. Nonequilibrium flow over a wedge is used to show the approach to equilibrium flow and to demonstrate the nature of the reaction zone behind the bow shock wave. The structure and development of a blunt-body entropy layer in nonequilibrium flow is examined for a blunt cone at zero incidence. Three dimensional computations for the Space Shuttle body at 30 deg angle of attack are presented. A nondimensional scaling parameter, the Damkohler number (the ratio of flow time to chemical reaction time) is calculated and its significance discussed. .

Rotational cooling of aniline in axis-symmetric and planar pulsed supersonic expansions

Abstract: Laser-induced fluorescence (LIF) has been used to measure rotational temperatures, TR, of the aniline molecule in axis-symmetric and planar pulsed supersonic expansions of He, Ne, and Ar. The rotat...

Mach 0.6 to 3.0 Flows over Rectangular Cavities

Abstract: : Internal weapons carriage in high performance aircraft is often adversely affected by the severe aeroacoustic environment produced with the weapons bay doors open. To obtain a better understanding of this fluid dynamic problem, basic static and oscillatory pressure data were obtained for Mach 0.6 to 3.0 flows over shallow rectangular cavities in a generic flat plate model. Cavity length to depth ratios were varied from approximately 5 to 10. Static pressure data characteristic of both open and closed cavity flows were obtained. An improved Rossiter method is presented that satisfactorily predicts the possible frequency modes within the cavity. Highest fluctuating pressure occurs on the aft bulkhead, peaking near Mach 1.5 for the conditions tested. Aeroacoustic levels are substantially reduced by installing suppression fences (spoilers) at subsonic and low supersonic conditions. Acoustic levels generally drop rapidly above Mach 1.5. (Author)

Effect of tail-fin span on stability and control characteristics of a Canard-controlled missile at supersonic Mach numbers

Abstract: An experimental wind-tunnel investigation was conducted at Mach numbers from 1.60 to 3.50 to obtain the longitudinal and lateral-directional aerodynamic characteristics of a circular, cruciform, canard-controlled missile with variations in tail-fin span. In addition, comparisons were made with the experimental aerodynamic characteristics using three missile aeroprediction programs: MISSILE1, MISSILE2, and NSWCDM. The results of the investigation indicate that for the test Mach number range, canard roll control at low angles of attack is feasible on tail-fin configurations with tail-to-canard span ratios of less than or equal to 0.75. The conards are effective pitch and yaw control devices on each tail-fin span configuration tested. Programs MISSILE1 and MISSILE2 provide very good predictions of longitudinal aerodynamic characteristics and fair predictions of lateral-directional aerodynamic characteristics at low angles of attack, with MISSILE2 predictions generally in better agreement with test data. Program NSWCDM provides good longitudinal and lateral-directional aerodynamic predictions that improve with increases in tail-tin span.

Calculation of viscous supersonic flows over finned bodies

Abstract: The parabolized Navier-Stokes (PNS) equations are used to calculate the viscous, supersonic flow fields about a six-finned projectile and a generic four-finned missile at angles of attack. Since current computer speeds and storage preclude a fully three-dimensional calculation using the unsteady, Reynolds-averaged, Navier-Stokes equations, the applicability of the PNS equations to the above flow fields is of considerable interest. Two important aspects of the calculation are grid generation and the type of smoothing used to prevent nonphysical solutions. This paper includes a description of the grid-generation process. Results in the form of density contours and velocity vector plots are presented for the two configurations. The applicability of the PNS equations to the complicated flow fields considered is successfully demonstrated.

Three-Dimensional Aerodynamic Characteristics of Oscillating Supersonic and Transonic Annular Cascades

Abstract: L+ The Society shall not be responsible for statements or opinions advanced in papers or in G discussion at meetings of the Society or of its Divisions or Sections, or printed in its M publications. Discussion is printed only if the paper is published in an ASME Journal. ] ^C Released for general publication upon presentation. Full credit should be given to ASME, the Technical Division, and the author(s). Papers are available from ASME for nine months after the meeting. Printed in USA. 82-GT-126

Effects of the Kelvin-Helmholtz surface instability on supersonic jets

Abstract: An exact numerical calculation is provided for of linear growth and phase velocity of Kelvin-Helmholtz unstable wave modes on a supersonic jet of cylindrical cross section. An expression for the maximally unstable wavenumber of each wave mode is found. Provided a sharp velocity discontinuity exists all wave modes are unstable. A combination of rapid jet expansion and velocity shear across a jet can effectively stabilize all wave modes. The more likely case of slow jet expansion and of velocity shear at the jet surface allows wave modes with maximally unstable wavelength longer than or on the order of the jet radius to grow. The relative energy in different wave modes and effect on the jet is investigated. Energy input into a jet resulting from surface instability is discussed. Previously announced in STAR as N83-17379

Constant-temperature hot-wire anemometer practice in supersonic flows. I - The normal wire

Abstract: The performance of a constant-temperature inclined hot-wire in a supersonic flow is critically examined. It is shown that calibration techniques applicable to subsonic flow, such as the cosine cooling law cannot be used when the flow is supersonic. Calibration and measurement procedures appropriate to supersonic flow are suggested, together with the possible limits on their validity. Experimental results for different wires indicate that the sensitivities do not seem to depend on flow direction according to any simple correlation. When the sensitivity exhibits a strong dependence on flow direction, the wire should be discarded to avoid errors due to nonlinear effects.

Coherent Structures Producing Machwaves Inside and Outside of the Supersonic Jet

Abstract: Supersonic jets emit Machwaves which are rather regular ones. Previous investigations using visualizations and an optical microphone have revealed that these Machwaves are shock waves which are accompanying mixing layer structures travelling downstream at three preferred speeds. The experimental results could be approximated by very simple relations. Local measurements within the mixing layer are needed in order to find out the reason for these relations. Two particular doppler velocimeters have been used for doing such measurements. They have shown that a weak regular contribution to the essentielly random velocity fluctuations exists. All results obtained so far agree with a hypothesis which is based upon the idea that the regular contribution consists of a vortex pattern the movement and extent of which are governed by pressure waves.

Motor device using supersonic vibration

Abstract: PURPOSE:To form a motor which utilizing supersonic vibration by associating a plurality of electrostrictive elements in an elastic unit and moving a movable element which is contacted under pressure with the surface of the unit by the synthetic progressive wave lateral and longitudinal waves. CONSTITUTION:The nodes of a cylindrical vibrator 13 which is made of an elastic material in a casing 11 is supported by a supporting member 12, and a rotor 14 is contacted as a movable element at the inner peripheral surface under pressure on the taper 13'. The vibrator 13 axially elongates and contacts by providing electrostrictive elements 18, 19 inserted with electrode at the intermediate and applying high frequency voltage to them. The mass point A on the surface of an elastic unit 1 moves on an ellipse Q synthesized with lateral and lngitudinal vibrations (a) and (b) in the direction M, the movable element 2 which is contacted under pressure wit the unit 1 is moved in the direction N. This principle is utilized to rotate the rotor 14 and to transmit it to a shaft 15. Accordingly, a motor of small size and weight utilizing supersonic vibration can be obtained.

Wind tunnel investigation of the transonic aerodynamic characteristics of forward swept wings

Abstract: This paper discusses some of the results of a series of wind tunnel investigations conducted on forward and aft swept wings in order to compare the relative drag performance of both wings at a transonic maneuver condition and to determine the associated drag penalty of the forward swept wing for a high supersonic cruise condition. At the transonic maneuver design point, the results indicate a significant reduction in the profile drag of the forward swept wing relative to the aft swept wing. The forward swept wing exhibits extreme sensitivity to wing root height and incidence variations. A drag penalty was recorded at M— 2.0 for the forward swept cruise wing. The cruise wings have the same sweep and "box" geometries as the transonic maneuver wings. The difference in supersonic cruise drag is attributed to the difference in the leading-edge sweeps (ALE = +48.7 and -28 deg for the aft and forward swept wings, respectively). This drag penalty decreases at lower supersonic Mach numbers. The results of the test indicate that the aft swept wing aerodynamic design and analysis methods used in the study can be used on forward swept wings with only minor modifications.