Showing papers on "Supersonic speed published in 1981"

Laser production of supersonic metal cluster beams

Abstract: Cold beams of metal clusters are produced by combining a laser vaporization technique with pulsed supersonic nozzle technology. (AIP)

Optimal trajectories in atmospheric flight

Abstract: Aspects of optimization theory and switching theory are discussed, taking into account the necessary conditions for extrema, a solution subject to constraints, the calculus of variations, the Pontryagin maximum principle, the canonical transformation, Contensou's domain of maneuverability, optimal switching, a junction with singular arc, and linearized singular control. Equations of motion are considered along with aerodynamic and propulsive forces, the general properties of optimal trajectories, flight in a horizontal plane, optimal coasting flight, supersonic cruise, the supersonic turn, supersonic maneuvers in a vertical plane, energy state approximation, a modified Chapman's formulation for optimal reentry trajectories, optimal planar reentry trajectories, and an optimal glide of reentry vehicles. Orbital aerodynamic maneuvers are examined, giving attention to aerodynamic capture, a change in the apogee, a change in the eccentricity, a change in the perigee, an orbital maneuver, an aerodynamic maneuver, and a combined maneuver.

Optimal trajectories in atmospheric flight

Abstract: Aspects of optimization theory and switching theory are discussed, taking into account the necessary conditions for extrema, a solution subject to constraints, the calculus of variations, the Pontryagin maximum principle, the canonical transformation, Contensou's domain of maneuverability, optimal switching, a junction with singular arc, and linearized singular control. Equations of motion are considered along with aerodynamic and propulsive forces, the general properties of optimal trajectories, flight in a horizontal plane, optimal coasting flight, supersonic cruise, the supersonic turn, supersonic maneuvers in a vertical plane, energy state approximation, a modified Chapman's formulation for optimal reentry trajectories, optimal planar reentry trajectories, and an optimal glide of reentry vehicles. Orbital aerodynamic maneuvers are examined, giving attention to aerodynamic capture, a change in the apogee, a change in the eccentricity, a change in the perigee, an orbital maneuver, an aerodynamic maneuver, and a combined maneuver.

PAN AIR - A higher order panel method for predicting subsonic or supersonic linear potential flows about arbitrary configurations

Abstract: PAN AIR is a computer program for predicting subsonic or supersonic linear potential flow about arbitrary configurations. It uses linear source and quadratic doublet strength distributions. These higher-order distributions have been implemented in a manner that greatly reduces the numerical stability problems that have plagued earlier attempts to make surface paneling methods work successfully for supersonic flow. PAN AIR's problem-solving capability, numerical approach, modeling features, and program architecture are described. Numerical results are presented for a variety of geometries at supersonic Mach numbers.

Numerical simulations of detonations in hydrogen-air and methane-air mixtures

Abstract: Detailed numerical simulations of supersonic reactive flow and gas phase detonation problems are very expensive due to their computer time and memory requirements. The bulk of this cost is in integrating the ordinary differential equations describing chemical reactions. A global induction parameter model has thus been developed which describes the chemical induction time of a mixture and allows for release of energy over a finite time period. The specific gases for which it has been calibrated are stoichiometric mixtures of hydrogen and methane in air. The relatively inexpensive induction parameter model is then used in time-dependent one- and two-dimensional simulations of supersonic reactive flows.

A Theoretical and Experimental Investigation of the Constant Area, Supersonic-Supersonic Ejector

Abstract: An investigation of the constant area, supersonic-supersonic ejector has been conducted wherein one supersonic stream is pumped directly by another inside a confining duct. The theoretical analysis is based on simplified, one-dimensional models of the constant area mixing section and inviscid interaction region. The parametric dependence of the ejector pressure recovery performance on each of seven dimensionless variables is presented. A series of small-scale, axisymmetric ejector experiments indicates that the theory predicts maximum ejector compression ratios that are 15-22% higher than the measured values and that the ejector is susceptible to separation of the secondary stream at the point of confluence of the primary and secondary streams.

Pulsed molecular beams: A lower limit on pulse duration for fully developed supersonic expansions

Abstract: We derive an expression for Δtmin, the mimimum pulse duration (’’valve open time’’) required if a pulsed nozzle is to produce a supersonic beam comparably ’’cold’’ to that obtained from a continuous source.(AIP)

Rotational cooling in a supersonic expansion of ammonia

Abstract: Collisional selection rules are determined for ammonia in a cryopumped supersonic jet.(AIP)

Pulsating flows about axisymmetric concave bodies

Abstract: ^all, I. M., "Transonic Flow in Two-Dimensional and AxiallySymmetric Nozzles/' Quarterly Journal of Mechanics and Applied Mathematics, Vol. XV, Pt. 4, 1962, pp. 487-508. Kliegel, J. R. and Levine, J. N., "Transonic Flow in Small Throat Radius of Curvature Nozzles," AIAA Journal, Vol. 7, July 1969, pp. 1375-1378. 3 Levine, J. N. and Coats, D. E., "Transonic Flow in a ConvergingDiverging Nozzle," NASA CR111104, Sept. 1970. Dutton, J. C. and Addy, A. L., "A Theoretical and Experimental Investigation of Transonic Flow in the Throat Region of Annular Axisymmetric, Supersonic Nozzles," Dept. of Mechanical and Industrial Engineering, Univ. of Illinois at Urbana-Champaign, Rept. No. UILU-ENG-80-4001, Jan. 1980. Dutton, J. C. and Addy, A. L., "TRANNOZ: A Computer Program for Analysis of Transonic Throat Flow in Axisymmetric, Planar, and Annular Supersonic Nozzles," Dept. of Mechanical and Industrial Engineering, Univ. of Illinois at Urbana-Champaign, Rept. No. UILU-ENG-80-4005, April 1980. Cuffel, R. F., Back, L. H., and Massier, P. F., "Transonic Flowfield in a Supersonic Nozzle with Small Throat Radius of Curvature, "AIAA Journal, Vol. 7, July 1969, pp. 1364-1366.

CARS measurement of velocity in a supersonic jet

Abstract: The velocity in a supersonic jet flow has been measured using CW CARS and agrees to within 4 percent of the calculated value.

Computation of hypersonic viscous flow around three-dimensional bodies at high angles of attack

Abstract: A parabolized Navier-Stokes code capable of predicting steady viscous supersonic flows with cross-flow separation is applied to three-dimensional arbitrary geometries at high angles of attack. The numerical procedure, which is implicit, noniterative, and of second-order accuracy in the marching direction, has been used to compute complicated flow fields containing a relatively thick sonic layer and regions of strong viscous-inviscid interaction. A consistent and accurate procedure has also been developed to provide the necessary starting data through timewise integration of the equations of motion near the nose-tip region of the body. Numerical results obtained from the present method compare well with experiment for both the surface pressures and heat transfer.

Shock-Capturing Model for One- and Two-Phase Supersonic Exhaust Flow

Abstract: A shock-capturing model (SCIPPY) for analyzing steady supersonic flows in two spatial dimensions is discussed SCIPPY serves as a component part of the new JANNAF standard low-altitude rocket plume model as well as the NASA Langley Research Center model for aircraft afterbody flow Generalized oneor two-phase mixtures are considered with a nonequilibrium treatment of gas/particle interactions implemented Unique capabilities include the automated analysis of embedded subsonic regions behind Mach disks and the use of multiple-mapped domains for obtaining high grid resolution in strong wave regions Applications to exhaust plume flowfields are stressed herein

PAN AIR Applications to Weapons Carriage and Separation

Abstract: The PAN AIR technology has been used to analyze the complex flow phenomena associated with aircraft/weapons carriage and mutual interference during separation. Force, moment, and flowfield characteristics have been compared with experimental results for a fighter aircraft and a tangent ogive store. These comparisons were made for both the aircraft and store alone, as well as for the aircraft with the store in various separated conditions. The study has demonstrated the PAN AIR pilot code's unique capabilities to analyze complex aircraft and weapon configurations at both subsonic and supersonic speeds. c CD CL CP CM M ft v V vv x,y, z

Investigation of Supersonic Air Ejectors : Part 1. Performance in the Case of Zero-Secondary Flow

Abstract: The performance of a supersonic air ejector in the case of zero-secondary flow was studied by varying the Mach number of the primary nozzle and the throat area ratio of the mixing tube to the primary nozzle. As the result, it has been shown that an optimum throat area ratio exists for each Mach number of the primary nozzle in which case the vacuum performance of the ejector becomes maximum with a minimum stagnation pressure of the primary flow. The physical meanings of the optimum throat area ratio and other ejector characteristics have been clarified from the results of pressure measurements and optical observations. Furthermore, modifying a previous method in the case of a constant-area mixing tube, the ejector performance was calculated for a variable-area mixing tube in the case of a larger throat area ratio than the optimum one. Calculated values agree well with the experimental results.

Experiments on the nonlinear characteristics of noise propagation from low and moderate Reynolds number supersonic jets

Abstract: A series of experiments were conducted on high-speed model jets to identify and quantify the distortion of radiated noise by nonlinear propagation effects. The jets were operated in a low to moderate Reynolds number range, and the radiated noise was either broadband or discrete in frequency. Three condenser microphones were used to measure the waveforms propagated by the axisymmetric, cold model jets of Mach numbers 2.1 and 2.5. Relatively low Reynolds numbers were obtained by exhausting the jets into a low pressure anechoic test chamber. Nonlinear propagation distortion effects, such as wave steepening, harmonic generation and wave merging, were easily quantified. At a moderate Reynolds number, low frequency production and wave amalgamation, measured by a decrease in the zero crossings per unit time, were quantified in the propagation of sound away from the jet.

Flush inlet for supersonic aircraft

Abstract: A flush inlet and inlet air passage for supersonic aircraft including provisions for efficiently decelerating a supersonic airstream entering the inlet and converting such airstream to subsonic airflow within the inlet air passage prior to introduction into the aircraft's jet propulsion engine. More specifically, a two-dimensional inlet and convergent/divergent inlet air passage for supersonic jet aircraft wherein the inlet is flush with the aircraft's external surface, and the supersonic airflow entering the inlet is reduced to transonic or subsonic velocity by means of a series of weak shock waves as the airstream transits the convergent portion of the inlet passage and, thereafter, the subsonic or transonic flow is further decelerated as it transits the divergent portion of the inlet passage prior to introduction into the engine; such inlet including: (i) an expansion corner at the upstream leading edge of the inlet for turning and expanding the freestream airflow; (ii) provision for inflight optimization of the inlet cant angle at the expansion corner as a function of the actual Mach number; (iii) provision for inflight adjustment of the inlet passage boundary walls as a function of the speed and pressure of the inlet airflow; and (iv), means for removing excess low energy boundary layer air from the inlet passage surfaces to insure formation of a proper shock wave pattern to effect airflow deceleration. An exemplary supersonic flush inlet designed for operation at speeds of Mach 2.2, and below, has been illustrated; and, provision is made for increasing the pressure of the low energy boundary layer air extracted from the inlet passage to levels which readily permit of overboard discharge.

A 100 μsec, reliable, 10 Hz pulsed supersonic molecular beam source

Abstract: A 10-Hz repetition rate, 100-microsec duration, reliable pulsed supersonic molecular beam source is described. Mechanical and electrical design of the pulsed valve are given in detail. Characteristics of the supersonic expansion obtained using coherent anti-Stokes Raman spectroscopy in acetylene are presented. They include pulse shape, gas rotational and translational cooling as a function of distance from the nozzle, clustering effects, and shock heating at the leading edge of the pulse.

MC DRAG - A Computer Program for Estimating the Drag Coefficients of Projectiles

Abstract: : This report presents a FORTRAN program 'MC DRAG' for estimating a projectile's zero-yaw drag coefficient from the given values of certain size and shape parameters. The results are valid over a Mach number range of 0.5 to 5 and a projectile diameter range of 4 to 400 millimetres. A user's guide and a FORTRAN listing of MC DRAG is provided. The program is applied to three illustrative examples: (1) an experimental low-drag small arms bullet, the 5. 56mm BRL-1 design; (2) a 55mm scale model of the Minuteman re-entry stage vehicle; (3) the 155mm long-range artillery shell M549. The MC DRAG program estimates drag coefficient to within 3% error at supersonic speeds, 11% error at transonic speeds, and 6% error at subsonic speeds.

Improved Calculation of High Speed Inlet Flows. Part II: Results

Abstract: An improved numerical algorithm that solves the full mean compressible Navier-Stokes equations has been applied to the calculation of the flowfield in three separate configurations of a simulated high speed aircraft inlet. The inlet geometry consists of a converging supersonic diffuser, formed by two nonparallel plates, followed by a constant height "throat." For all cases, the freestream Mach number is 3.51, and the Reynolds number is 13.6 X10 based on the inlet length. The three configurations are characterized by different values of the angle of the converging supersonic diffuser and different boundary-layer bleed schedules. The computed results are compared with detailed experimental data for the ramp and cowl surface pressure distribution, and the boundary-layer pitot profiles at seven different streamwise locations. The agreement with the experimental results is generally good, although the experimental data display evidence of three dimensionality over a portion of the inlet flowfield.

Application of a laser interferometer skin-friction meter in complex flows

Abstract: A nonintrusive skin-friction meter has been found useful for a variety of complex wind-tunnel flows. This meter measures skin friction with a remotely located laser interferometer that monitors the thickness change of a thin oil film. Its accuracy has been proven in a low-speed flat-plate flow. The wind-tunnel flows described here include sub-sonic separated and reattached flow over a rearward-facing step, supersonic flow over a flat plate at high Reynolds numbers, and supersonic three - dimensional vortical flow over the lee of a delta wing at angle of attack. The data-reduction analysis was extended to apply to three-dimensional flows with unknown flow direction, large pressure and shear gradients, and large oil viscosity changes with time. The skin friction measurements were verified, where possible, with results from more conventional techniques and also from theoretical computations.

Calculation of vortex lift effect for cambered wings by the suction analogy

Abstract: An improved version of Woodward's chord plane aerodynamic panel method for subsonic and supersonic flow is developed for cambered wings exhibiting edge separated vortex flow, including those with leading edge vortex flaps. The exact relation between leading edge thrust and suction force in potential flow is derived. Instead of assuming the rotated suction force to be normal to wing surface at the leading edge, new orientation for the rotated suction force is determined through consideration of the momentum principle. The supersonic suction analogy method is improved by using an effective angle of attack defined through a semi-empirical method. Comparisons of predicted results with available data in subsonic and supersonic flow are presented.

Roughness effects on boundary-layer transition in a nozzle throat

Abstract: A boundary-layer transition study was carried out in the throat region of the DeLaval nozzle of a supersonic wind tunnel. The study was motivated equally by the need to find thresholds for laminar boundary-layer flow in the tunnel walls when roughness is present and by the desire to simulate transition on roughened blunt bodies in supersonic and hypersonic flow. Detailed inviscid and viscous flow measurements were done from the low subsonic to the supersonic regions of the nozzle throat. The roughness was caused by attaching distributed roughness overlays on the nozzle surface. Transition, detected by hot-film anemometers, was found to move upstream as the flow Reynolds number and/or the roughness height increased. Cast in the coordinates of some of the empirical blunt-body transition correlations currently in use, the present transition data agree with the available blunt-body data when the nondimensional roughness exceeds unity and support the concept of a constant roughness Reynolds number for transition in that regime. At the lower roughness heights, the results show that the transition Reynolds number departs from the aforementioned correlations and approaches a limit insensitive to roughness but characteristic of the experimental facility.

Shock-associated noise reduction from inverted-velocity-profile coannular jets

Abstract: Acoustic measurements show that the shock noise from the outer stream is virtually eliminated when the inner stream is operated at a Mach number just above unity, regardless of all the other jet operating conditions. At this optimum condition, the coannular jet provides the maximum noise reduction relative to the equivalent single jet. The shock noise reduction can be achieved at inverted-as well as normal-velocity-profile conditions, provided the coannular jet is operated with the inner stream just slightly supersonic. Analytical models for the shock structure and shock noise are developed indicate that a drastic change in the outer stream shock cell structure occurs when the inner stream increases its velocity from subsonic to supersonic. At this point, the almost periodic shock cell structure of the outer stream nearly completely disappears the noise radiated is minimum. Theoretically derive formulae for the peak frequencies and intensity scaling of shock associated noise are compared with the measured results, and good agreement is found for both subsonic and supersonic inner jet flows.

OBSERVATION OF OPTICAL RAMSEY FRINGES IN THE 10 µm SPECTRAL REGION USING A SUPERSONIC BEAM OF SF6

Abstract: We report a first observation of optical Ramsey fringes in the 10 ym spectral region using a supersonic seeded beam of 7% SF, in He, illuminated by a CO laser in spatially-separated field zones. We have used either three standing waves or four travelling waves and obtained highly contrasted fringes with a 23 kHz half-width corresponding to a 5 mm distance between zones. Laser excitation of the vibrational energy of molecules in a beam can be conveniently detected with a cryogenic bolometer [1] and a demonstration of this technique in the case of the V_ mode of SF, excited by CO or N„0 lasers has been recently given [2] . With this equipment the spatial analog of coherent transient effects such as the Rabi oscillations of the transition probability and the adiabatic rapid passage were shown to occur respectively with plane and curved wavefronts. In an attempt to investigate the potential use of this method for very high resolution spectroscopy and optical frequency standards we have made a preliminary experiment to detect the Ramsey fringes associated with saturation spectroscopy in an interaction geometry comprising three or four field zones [3-14]. For this experiment we used the P(4) F.. and E components of the . band of SF, which can be reached with a waveguide CO laser oscillating on the P(16) CO line at 10.55 Van. To control the frequency of this laser we locked it, with a tunable frequency offset, to a conventional reference laser locked to the 0(45) vj. SF, line. 1 b The beam from the waweguide laser was spatially filtered and magnified to have a waist of w = 6 mm. In the case of illumination by this single beam the resulting width (FWHM) of the observed line was a combination of transit broadening and residual first-order Doppler effect along the optical axis and amounted to 300 kHz.We used the Rabi oscillation to set the laser beam waist precisely on the molecular beam [2]. Four oscillations of the signal could be observed with a 40% contrast with successive minima obtained for a total power of M,4,9 and 16 mW. To obtain fringes ,part of the laser beam was intercepted before the interaction region by a screen which transmitted the light only through 1 mm wide slits. Two different geometries were used in these experiments. In the first one, three equidistant standing waves were generated by three equidistant slits of 5 mm separation together with a corner cube placed on the other side of the molecular beam to (*)Work supported in part by D.R.E.T. (+)Permanent address : Physics and Chemistry Department, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1981802 C8-16 JOURNAL DE PHYSIQUE r e t r o r e f l e c t t h e l i g h t back through t h e slits. I n t h e second geometry, only two of t h e previous s l i t s were illuminated. An o f f s e t between t h e center of t h e s l i t s and t h e cen te r of t h e corner cube generated two counter-propagating s e t s of t r a v e l l i n g waves with a 5 mm d i s tance between adjacent co-propagating waves of each s e t . The spacing between t h e two s e t s can be a r b i t r a r y and was a c t u a l l y l O m m i n t h i s experiment. Highly contrasted f r inges have been obtained i n both cases and a s an example t h e f i g u r e d i sp lays t h e s igna l corresponding t o t h e four t r a v e l l i n g waves case. Use of purely t r a v e l l i n g waves t o ob ta in o p t i c a l Ramsey f r i n g e s has been suggested by t h e ana lys i s of references [4-5,101 and we have here a f i r s t demonstration of t h i s p o s s i b i l i t y together with t h e Ca beam experiment of Helmcke e t a1.[14] . The broad pedestal has a width QJ1.4 MHz corresponding t o t h e t r a n s i t broadening width across a s i n g l e zone. The f r inges themselves have a 23 kHz width (HTm) cons i s ten t with a QJ930 m/sec peak ve loc i ty of t h e SF6 molecules 1151 .

The use of adaptive grids in conjunction with shock capturing methods

Abstract: The use of shock capturing finite-difference techniques in computing flow fields containing shocks results in a smeared or oscillatory solution in the vicinity of the shocks. This smearing or oscillatory behavior is due to the discretized form of the governing differential equations used to compute the solution. The discretization error can be reduced by a proper clustering of mesh points in the region of the shock and by using shock aligned grids. This paper uses a simple method that was developed earlier to cluster points near the shocks and serves to introduce a new method of generating a shock aligned mesh. Applications to the one-dimensional inviscid Burgers' equation, supersonic flow over a wedge with the associated straight oblique shock, one- and two-dimensional inviscid flows through an expanding duct and the problem of a straight oblique shock in a uniform supersonic freestream are presented. Significant reduction in the oscillatory behavior of the solution is demonstrated.