Showing papers in "AIAA Journal in 1966"
TL;DR: Quasi-steady aerodynamic and von Karman large deflection plate theory equations of nonlinear oscillations of fluttering plate for single mode subsonic and sonic or coupled mode supersonic oscillations are given in this article.
Abstract: Quasi-steady aerodynamic and von Karman large deflection plate theory equations of nonlinear oscillations of fluttering plate for single mode subsonic and sonic or coupled mode supersonic oscillations
478 citations
429 citations
TL;DR: In this article, the authors used the solution for potential flow subject to the boundary conditions of no flow through the head end and uniform speed normal to the burning surface, and the result for the Mach number in a cylindrical chamber is
Abstract: .!LTHOUGH for many purposes the one-dimensional apft proximation to the steady flow in a rocket chamber is adequate, there are occasions when more precise information is required. For example, analysis of the stability of pressure oscillations involves knowledge of the streamlines. It has been common practice to use the solution for potential flow subject to the boundary conditions of no flow through the head end and uniform speed normal to the burning surface. Since the Mach number generally is very small, one may assume the density to be constant; the result for the Mach number in a cylindrical chamber is
334 citations
331 citations
264 citations
212 citations
211 citations
TL;DR: Dynamic buckling of imperfection sensitive models, specifically cylindrical shells under axial compression, can be found in this paper, where the authors describe the buckling behavior of imperfections sensitive models.
Abstract: Dynamic buckling of imperfection sensitive models, specifically cylindrical shells under axial compression
203 citations
183 citations
TL;DR: Macroscopic viscoelastic properties of fiber reinforced materials analyzed on basis of composite cylinder assemblage model and correspondence principle were analyzed in this paper, based on the correspondence principle.
Abstract: Macroscopic viscoelastic properties of fiber reinforced materials analyzed on basis of composite cylinder assemblage model and correspondence principle
168 citations
TL;DR: In this article, the influence of edge conditions on the critical load of cylindrical shells was investigated for six additional combinations of boundary conditions, and it was shown that drastic reductions for cylinders with lateral support of the edges were obtained only if the edges are free in the tangential direction.
Abstract: : Recent investigations by Stein and by Fischer on the influence of edge conditions on the critical load of cylindrical shells are here extended to cover six additional combinations of boundary conditions. The results show that drastic reductions of the critical load for cylinders with lateral support of the edges are obtained only if the edges are free in the tangential direction. For other boundary conditions, this reduction is never more than about 20 percent. Consequently, the results of this investigation alone cannot explain the well-known discrepancy between theory and test data. However, the importance of the choice of boundary conditions for practical analysis is clearly demonstrated.
TL;DR: In this paper, the surface heterogeneity of a composite propellant is incorporated in a model of the propellant combustion process, explicitly including the oxidizer particle size distribution, and expressions for the mean, one-dimensional, propellant surface and flame temperatures are derived assuming planar regions of heat generation.
Abstract: The surface heterogeneity of a composite propellant is incorporated in a model of the propellant combustion process. This process is pictured as the sum of fuel pyrolysis, oxidizer decomposition, heterogeneous chemical reaction between the fuel and decomposed oxidizer in small fissures surrounding individual oxidizer particles, and gas phase combustion of all final decomposition products. Expressions for the burning rate and the rate of heat generation at the propellant surface and in the gas phase flame are formulated, explicitly including the oxidizer particle size distribution. Expressions for the mean, one-dimensional, propellant surface and flame temperatures are derived assuming planar regions of heat generation. A collected set of implicit, algebraic equations is solved numerically for the propellant burning rate, surface (and flame) temperatures for a variety of physical parameters. The burning rate is found to depend strongly on the oxidizer particle ignition delay at low pressures, and upon the position of the external flame at high pressures. The effect of the heterogeneous reaction on the burning rate is strongest at intermediate pressures. The results agree quite well with experimental data on the effect of pressure and oxidizer particle size on composite propellant burning rates, surface temperatures, and surface structure.
TL;DR: Compressive strength and instability failure mechanism in uniaxial boron fiber-metal matrix composite material was discussed in this paper, where the authors proposed a failure mechanism for the composite material.
Abstract: Compressive strength and instability failure mechanism in uniaxial boron fiber-metal matrix composite material
TL;DR: In this paper, the surface pressure distributions throughout the region of separation and reattachment were measured, and points of reattraction were determined, showing that the initial (steepest) parts of the re-attachment pressure rise tend to become superimposed when plotted against x/h.
Abstract: Supersonic flow over a downstream-facing step on the circumference of a large, ducted, axisymmetric body was used to study flow reattachment. Step heights h were 0.25, 1.00, and 1.68 in., compared to a body radius of 6 in. Freestream Mach numbers were in the range 2 to 4.5. Theturbulent boundary-layer thickness just ahead of the step varied from 0.14 to 0.19 in. (momentum thicknesses of about 0.01 in.).
Surface pressure distributions throughout the region of separation and reattachment were measured, and points of reattachment were determined. Comparison of the shapes of the pressure distributions for various step heights shows that the initial (steepest) parts of the reattachment pressure rise, up to the point of reattachment, tend to become superimposed when plotted against x/h. Downstream reattachment the curves branch out, exhibiting a dependence on geometry and probably on initial shear layer profile. In the region of the initial pressure rise (near the end of the "dead air" region) dynamic pressures are low; the pressure rise there apparently is balanced by turbulent shear stress.
TL;DR: In this paper, the cross-flow drag and normal force coefficients are determined experimentally as a function of the relative displacement of fluid in time-dependent two-dimensional flow, and the evolution with time of the body-wake characteristics are determined from high-speed motion pictures.
Abstract: The analogy between the impulsive flow over circular cylinders and flat plates and the separated flow about slender bodies moving at high angles of attack in the subsonic to moderately supersonic-velocity range is discussed. The cross-flow drag and normal force coefficients are determined experimentally as a function of the relative displacement of fluid in time-dependent two-dimensional flow. The evolution with time of the body-wake characteristics are determined from high-speed motion pictures. The results show that during the growth of symmetrical vortices, the laminar flow drag coefficients of the test bodies reach a value about 25% higher than their corresponding steady flow values. In the supercritical range, records for the drag show considerable disagreement, except that the drag coefficient lies between 0.25 and 0.40.
TL;DR: The effect of injecting a secondary gas stream through a rear ward-facing slot in a direction parallel to a wall into a supersonic air flow has been examined in a small Mach 3 wind tunnel.
Abstract: The effect of injecting a secondary gas stream through a rear ward-facing slot in a direction parallel to a wall into a supersonic air flow has been examined in a small Mach 3 wind tunnel. The experiments were carried out for three step heights, 0.121, 0.180, and 0.239 in. with slot openings of 0.064, 0.123, and 0.182 in., respectively. Air was used as the secondary fluid with these three different slot openings. The total temperature of the main flow was equal approximately to the room temperature, and the temperature of the wall at the point of injection varied between 418° and 655°R as determined by the temperature of the secondary air. The ratio M of the mass velocity in the secondary stream to that of the mainstream was in the range of 0 to 0.408. Helium also was injected through a slot opening of 0.063 in. for two different injection parameters M = 0.01 and 0.02 and a temperature of the wall at the point of injection ranging between 562.8° and 663.7°R. Schlieren photographs are presented and adiabatic wall temperature measurements are described.
TL;DR: The surface ignition of solid propellants has been represented by several analytical models, each involving obvious compromises with regard to the scope of applicability as discussed by the authors, and these models are distinguishable primarily in terms of site of the exothermic reaction governing ignition.
Abstract: : Surface ignition of solid propellants has been represented by several analytical models, each involving obvious compromises with regard to scope of applicability. These models are distinguishable primarily in terms of site of the exothermic reaction governing ignition. Early research with nitrocellulose led to development of a theory involving chemical heat generation in the condensed phase. Two subsequent theoretical models were developed to explain ignition of the solid fuel ingredient of a composite propellant in an oxidizing atmosphere, and these two models were then extended on a heuristic basis to encompass a composite propellant in an inert atmosphere in which the oxidizing gas was produced by decomposition of the solid oxidizer. These two models are distinguished by whether the oxidation occurs at the surface or in the gas film above the surface. This report reviews the solid, heterogeneous, and gas-phase ignition theories and reviews the nature and implications of the assumptions involved. It is concluded that, while possessing certain drastic simplifications in common, the various quantitative models differ so conspicuously in their assumptions regarding external initiating stimulus as to make quantitative comparisons or tests of validity impossible.
TL;DR: In this article, the Galerkin method and an analog computer were used to solve the nonlinear integrodifferential equation of motion for normal deflection of a shallow circular arch under uniform dynamic pressure loading.
Abstract: The general problem of large dynamic elastic deflections of a shallow circular arch under uniform dynamic-pressure loading is considered both analytically and experimentally. The basic nonlinear integrodifferential equation of motion for normal deflection is solved, for both simply supported and clamped boundary conditions, using the Galerkin method and an analog computer. Specifically, cases of initial-velocity (impulsive) loading, step loading, and rectangular-pulse loading are treated, both with and without various types of initial imperfections. Critical values for dynamic snap buckling are defined as those for which a very small increase in load produces a large increase in deflection of the **snap-through" type. The effect on these values of varying imperfection size and pulse length is studied in some detail.
TL;DR: In this article, the dependence of the ion current on the probe radius and on flow speed was investigated and correlated with the ratio of probe radius to Debye length and the ratio ratio of flow speed to the ion acoustic speed.
Abstract: Experiments were performed in a steady, low-density flow of argon plasma to determine the behavior of small cylindrical Langmuir probes in high-speed flows. In particular, the dependence of the ion current on the probe radius and on flow speed was investigated and correlated with the ratio of probe radius to Debye length and the ratio of flow speed to the ion acoustic speed. The probes were then employed to study the electron temperature and number density distributions in the stagnation region of a flat-nosed cylinder in supersonic flow. The Reynolds number Re^ based on model diameter and viscosity at stagnation temperature, was in the range 70 to 125, whereas the Langmuir probes were free molecular. The charged-particle number density distribution measurements provided a graphic demonstration of the merging of the bow shock and the boundary layer at Re^ ^ 100, and also furnished some evidence of the diffusive separation of the ions and atoms in the shock wave. Nozzle and free-jet flowfields were probed also. Nomenclature
TL;DR: In this article, it is shown that the usual linearization approach to sequential estimation is seriously inadequate if the measurement function nonlinearity is comparable to the measurement error, thus making future data processing nonoptimal.
Abstract: It is shown that the usual linearization approach to sequential estimation is seriously inadequate if the measurement function nonlinearity is comparable to the measurement error. The essential difficulty is not that the estimated state, after processing a data point, is seriously affected by nonlinearity, but rather that the calculated covariance matrix of estimation errors becomes inaccurate, thus making future data processing nonoptimal, A powerful iteration scheme is described and its limitations noted. The bias nature of measurement function nonlinearity is also explored. A refinement in forming the measurement residual is introduced which reduces the nonlinearity in the measurement residual to the lowest level that appears practical. The suggestion of adding artificial noise to measurement data when the nonlinearity problem is severe is introduced.
TL;DR: In this paper, Mars atmospheric composition and laminar convective heating and ablation were used to predict performance of heat protection systems during entry to predict the performance of a heat protection system during Mars entry.
Abstract: Mars atmospheric composition and laminar convective heating and ablation studied to predict performance of heat protection systems during entry
TL;DR: In this paper, the spherical-harmonic approximation developed in astrophysics and neutron-Iran sport theory is applied to the radiation-transport equation for a nonscattering, quasi-equilibrium, grey gas.
Abstract: The spherical-harmonic approximation developed in astrophysics and neutron-Iran sport theory is applied to the radiation-transport equation for a nonscattering, quasi-equilibrium, grey gas. To a first approximation, the exact multidimensional transport equation is replaced by four differential equations. The gasdynamic equations, together with the four approximate transport equations, constitute a determinate set of purely differential equations valid for the complete range of optical thickness. Boundary conditions consistent with such approximations are discussed. Within the framework of linearized theory, the governing equation and the boundary conditions on velocity and on the temperature jump at the wall are obtained in terms of a perturbation velocity potential. To illustrate the special features of two-dimensional flow with radiation, a solution is obtained for steady flow over a sinusoidal wall. The solution is valid throughout the ranges of temperature and optical thickness. It is found that two systems of waves are present, a modified classical wave and a radiationinduced wave. The occurrence of pressure drag at subsonic speeds and the smoothing of the transition from subsonic to supersonic speeds reflect the nonequilibrium character of the radiating-gas flow.
TL;DR: In this article, an extension and improvement of the momentum integral method for predicting turbulent mixing and decay of axially symmetric, compressible, free jets is discussed and compared with the results of a series of jet-mixing experiments carried out on helium, methane, nitrogen, carbon dioxide, and freon jets mixing in air.
Abstract: An extension and improvement of Warren's momentum integral method for predicting the turbulent mixing and decay of axially symmetric, compressible, free jets to the case of the mixing of dissimilar gases is discussed. Two ideal gases having different molecular weights and specific heats are treated with the assumption that the local turbulent mixing rate at each axial location depends upon a suitably chosen local reference Mach number. This method of analysis is then compared with the results of a series of jet-mixing experiments carried out on helium, methane, nitrogen, carbon dioxide, and freon jets mixing in air. Mach numbers ranging from 0.75 to 3.30 were investigated. The character and mixing rates of both properly and improperly expanded supersonic jets were studied. It is concluded from a comparison of these data with the theoretical method presented that a general relationship exists, at each axial position in the jet, between a local mixing rate parameter and the local Mach number. This general relationship is independent, within the accuracy of these experiments, of the physical properties or the thermodynamic state of the mixing gases.
TL;DR: In this paper, the boundary-layer momentum thickness, dis-position thickness, skin-friction coefficient, and related quantities as a function of the body surface coordinate were analyzed for axisymmetric flow fields with and without heat transfer.
Abstract: a = C f = Cp = g = h = H = Hi = Htr = The compressible turbulent boundary layer is expressed in terms of the momentum integral and moment-of-momentum integral equations for arbitrary pressure gradient. Upon simpli- fication of this equation set with a Mager-type transformation, the two coupled differential equations are solved simultaneously to provide boundary-layer momentum thickness, dis- placement thickness, skin-friction coefficient, and related quantities as a function of the body surface coordinate. The analysis includes surface heat-transfer effects. Results of the analysis are presented for adiabatic, non-adiabatic, two-dimensional, and axisymmetric flow- fields in a Mach number range between 2 and 8. Flows with favorable and adverse pressure gradients are also examined. The present analysis is compared with available experimental and theoretical results. The analysis is found to yield satisfactory results for flows with and without heat transfer. In addition, for flows in the pressure of large adverse pressure gradients in which the boundary layer is known to be well-behaved, spurious separation is not indi- cated; instead, rather good agreement with available experimental data is observed.
TL;DR: Cantilevered continuous pipe conveying fluid at constant velocity, showing that internal and external damping and Coriolis forces may have destabilizing effect as discussed by the authors. But this is not the case in the case of a continuous pipe.
Abstract: Cantilevered continuous pipe conveying fluid at constant velocity, showing that internal and external damping and Coriolis forces may have destabilizing effect
TL;DR: In this article, a shallow, simply supported sinusoidal arch subject to a sinusoidally distributed step pressure load is studied over a range of arch geometries and two distinct mechanisms of initiation of the snapping process are revealed.
Abstract: The snapping of a shallow, simply supported sinusoidal arch subject to a sinusoidally distributed step pressure load is studied over a range of arch geometries. Critical pressure loads are determined by numerical integration of the equations of motion and by an infinitesimal stability analysis. The results of the two methods are compared and the sources of disagreement discussed. The study reveals two distinct mechanisms of initiation of the snapping process. These mechanisms, which are referred to as "direct" snapping and "indirect" (or "parametrically induced") snapping, respectively, control the phenomenon for particular ranges of the arch geometry.
TL;DR: A critical summary of studies in the fluid mechanics of hypersonic wakes formed behind vehicles of different geometries can be found in this article, where the authors review both the history and the special problems of the field.
Abstract: : A critical summary of studies in the fluid mechanics of hypersonic wakes formed behind vehicles of different geometries. The memorandum reviews both the history and the special problems of the field, and gives special attention to such issues as the laminar regime, transition to turbulence, and turbulence.
TL;DR: Strength of structural composites of orthotropic materials with arbitrary thickness and orientation including lamination and anisotropy effects as mentioned in this paper, including laminations, is studied in the literature.
Abstract: Strength of structural composites of orthotropic materials with arbitrary thickness and orientation including lamination and anisotropy effects
IBM1
TL;DR: In this article, it was shown that the elasticity bounds on effective moduli can be transcribed into bounds on viscoelastic effective relaxation moduli at times zero and infinity, simply by replacement of phase elastic moduli in the bound expressions, by initial and ultimate values of the phase relaxation modulations.
Abstract: the basis of the Abel-Tauber theorems, that elasticity bounds on effective moduli can be transcribed into bounds on viscoelastic effective relaxation moduli at times zero and infinity, simply by replacement of phase elastic moduli in the bound expressions, by initial and ultimate values of the phase relaxation moduli. Consequently, the bounds on G
TL;DR: In this paper, a detailed analytical investigation of the expansion and separation of a hypersonic boundary layer at the shoulder of a blunt-based body is presented, and numerical results are obtained with a rotational characteristics calculation.
Abstract: A detailed analytical investigation of the expansion and separation of a hypersonic boundary layer at the shoulder of a blunt-based body is presented. The expansion of the body boundary layer is assumed to be inviscid, and numerical results are obtained with a rotational characteristics calculation. A streamline at constant (base) pressure provides the required boundary condition downstream of the shoulder. With the base pressure given by a simple model of the complete base flow, it is possible to calculate the entire vortical flow above this streamline in detail. It is found that both the constant pressure streamline and the nearby "dividing streamline" are highly curved, concave outward, causing the rear stagnation point to be located quite close to the base. The formation of the "separation shock wave" is shown, and its shape and inclination angle are discussed. At high Mach numbers, the expansionseparation process dominates the entire base flow, producing a nonparallel vortical region that extends into the far wake. Finally, an approximate solution of the viscous free shear layer is derived. The temperature distribution behind a wedge is calculated and compared to experimental data.