Showing papers on "Oblique shock published in 1986"
Book•
01 Feb 1986
TL;DR: In this article, Navier-Stokes et al. discuss the fundamental principles of Inviscid, Incompressible Flow over airfoils and their application in nonlinear Supersonic Flow.
Abstract: TABLE OF CONTENTS Preface to the Fifth Edition Part 1: Fundamental Principles 1. Aerodynamics: Some Introductory Thoughts 2. Aerodynamics: Some Fundamental Principles and Equations Part 2: Inviscid, Incompressible Flow 3. Fundamentals of Inviscid, Incompressible Flow 4. Incompressible Flow Over Airfoils 5. Incompressible Flow Over Finite Wings 6. Three-Dimensional Incompressible Flow Part 3: Inviscid, Compressible Flow 7. Compressible Flow: Some Preliminary Aspects 8. Normal Shock Waves and Related Topics 9. Oblique Shock and Expansion Waves 10. Compressible Flow Through Nozzles, Diffusers and Wind Tunnels 11. Subsonic Compressible Flow Over Airfoils: Linear Theory 12. Linearized Supersonic Flow 13. Introduction to Numerical Techniques for Nonlinear Supersonic Flow 14. Elements of Hypersonic Flow Part 4: Viscous Flow 15. Introduction to the Fundamental Principles and Equations of Viscous Flow 16. A Special Case: Couette Flow 17. Introduction to Boundary Layers 18. Laminar Boundary Layers 19. Turbulent Boundary Layers 20. Navier-Stokes Solutions: Some Examples Appendix A: Isentropic Flow Properties Appendix B: Normal Shock Properties Appendix C: Prandtl-Meyer Function and Mach Angle Appendix D: Standard Atmosphere Bibliography Index
3,113 citations
139 citations
TL;DR: In this paper, the existence of a nearly stationary fast shock was confirmed and the authors showed that the transition from the supermagnetosonic flow region upstream of the shock to the nearly static region downstream of it is more complicated than was previously thought.
Abstract: In a previous study by the author, an approximately stationary fast shock was tentatively identified in a numerical experiment designed to study line-tied magnetic reconnection. Here the evidence for the occurrence of a stationary fast shock is reexamined, and the previous identification is confirmed. In the numerical experiment, line-tied reconnection is modeled by a configuration which produces two supermagnetosonic outflow jets - one directed upward, away from the photosphere, and one directed downward, toward an arcade of closed magnetic loops tied to the photosphere. The fast shock occurs when the downward-directed jet encounters the obstacle formed by the closed loops. Although the existence of a stationary, or nearly stationary, fast shock is confirmed, the transition from the supermagnetosonic flow region upstream of the shock to the nearly static region downstream of the shock is more complicated than was previously thought. Immediately downstream of the shock, there exists a deflection sheath in which the submagnetosonic flow coming out of the shock is diverted around the region of static closed loops. The MHD jump conditions are used to investigate the characteristics of the fast shock and to show that a stationary shock cannot exist unless accompanied by a deflection sheath. Analysis of the shock's location and dimensions suggests that such fast shocks may contribute to particle acceleration and to thermal condensation in flares.
109 citations
TL;DR: In this paper, the Laplace transformation of the perturbation results in an equation which has a simple solution for weak shock waves, and for strong shocks the solution is given by a power series.
Abstract: The solution for the perturbation growth of a shock wave striking a density discontinuity at a material interface is developed. The Laplace transformation of the perturbation results in an equation which has a simple solution for weak shock waves. The solution for strong shock waves may be given by a power series. It is assumed that the equation of state is that of an ideal gas. The four independent parameters of the solution are the ratio of specific heat for each material, the density ratio at the interface, and the incoming shock strength. Properties of the solution which are investigated include the asymptotic behavior at large times of the perturbation velocity at the interface, the vorticity near the interface, and the rate of decay of the solution at large distances from the interface. The last is much weaker than the exponential decay in an incompressible fluid. The asymptotic solution near the interface, in addition to a constant term, consists of a number of slowly decaying discrete frequencies. The number is roughly proportional to the logarithm of the density ratio at the surface for strong shocks, and decreases with shock strength. For weak shocks the solution is compared with results for an incompressible fluid. Only interface perturbation velocities which tend to zero at large times lead to a limited deformation of the interface. It is found that these are possible only for density ratios less than about 1.5.
103 citations
TL;DR: In this article, it was shown that shock waves for the compressible Navier-Stokes equations are nonlinearly stable and that a perturbation of a shock wave tends to the shock wave, properly translated in phase, as time tends to infinity.
Abstract: It is shown that shock waves for the compressible Navier-Stokes equations are nonlinearly stable. A perturbation of a shock wave tends to the shock wave, properly translated in phase, as time tends to infinity. Through the consideration of conservation of mass, momentum and energy we obtain an a priori estimate of the amount of translation of the shock wave and the strength of the linear and nonlinear diffusion waves that arise due to the perturbation. Our techniques include the energy method for parabolic-hyperbolic systems, the decomposition of waves, and the energy-characteristic method for viscous conservation laws introduced earlier by the author.
97 citations
TL;DR: In this article, a three-dimensional solution-adaptive grid scheme was proposed for complex fluid flows using tension and torsion spring analogies, which was previously developed and successfully applied for two-dimensional flows.
Abstract: A three-dimensional solution-adaptive-grid scheme is described which is suitable for complex fluid flows. This method, using tension and torsion spring analogies, was previously developed and successfully applied for two-dimensional flows. In the present work, a collection of three-dimensional flow fields are used to demonstrate the feasibility and versatility of this concept to include an added dimension. Flow fields considered include: (1) supersonic flow past an aerodynamic afterbody with a propulsive jet at incidence to the free stream, (2) supersonic flow past a blunt fin mounted on a solid wall, and (3) supersonic flow over a bump. In addition to generating three-dimensional solution-adapted grids, the method can also be used effectively as an initial grid generator. The utility of the method lies in: (1) optimum distribution of discrete grid points, (2) improvement of accuracy, (3) improved computational efficiency, (4) minimization of data base sizes, and (5) simplified three-dimensional grid generation.
92 citations
TL;DR: In this article, an experimental investigation was conducted to study the interaction between a shock wave and a turbulent boundary layer, and the results of the measurements indicated that the boundary layer was significantly altered by the interaction.
Abstract: An experimental investigation was conducted to study the interaction between a shock wave and a turbulent boundary layer. Compression corner models mounted on a wind tunnel floor were used to generate the oblique shock wave in the Mach 2.94 flowfield. Ramp angles of 8, 12, 16, 20, and 24 deg were used to produce the full range of possible flowfields, including flow with no separation, flow with incipient separation, and flow with a significant amount of separation. The principal measurement technique used was laser Doppler velocimetry (LDV), which was used to make two-component coincident velocity measurements within the redeveloping boundary layer downstream of the interaction. The results of the LDV measurements indicated that the boundary layer was significantly altered by the interaction. The mean streamwise velocity profiles downstream of the separated compression corners were very wake-like in nature, and the boundary-layer profiles downstream of all the interactions showed an acceleration of the flow nearest the wall as the boundary layers began to return to equilibrium conditions. Significant increases in turbulence intensities and Reynolds stresses were caused by the interactions, and indications of the presence of large-scale turbulent structures were obtained in the redeveloping boundary layers.
74 citations
TL;DR: In this paper, a parametric experimental study is reported on the quasiconical shock/boundary-layer interactions produced by three families of shock generators: sharp fins, semicones, and swept compression corners.
Abstract: A parametric experimental study is reported on the quasiconical shock/boundary-layer interactions produced by three families of shock generators: sharp fins, semicones, and swept compression corners The experiments were carried out at Mach 295 and Re/m = 63 X10 using a flat-plate turbulent boundary layer Over 50 distinct shock generator configurations were considered The results consist of surface flow patterns, pressure distributions, and flowfield visualizations An analysis of these results reveals that the interaction characteristics depend primarily on the inviscid shock wave strength and shape Given similar values of these parameters, "conical freeinteraction" similarity results even for disparate shock generators The similarity conditions among fin, semicone, and swept corner interactions are further explored in terms of normal Mach number scaling and flow regime changes with geometry variation
57 citations
01 Jan 1986
TL;DR: In this article, the authors examined the experimental case of free turbulence subjected to a shock wave, and the evolution of the field of turbulence was characterized on the basis of scale and level measurements.
Abstract: In an unsteady flow, the conditions of dynamic compatibility on both sides of a discontinuity cause the shock wave velocity to appear as an additional unknown. The shock wave turbulence can therefore be examined from two points of view: first, as a fixed discontinuity, the turbulence amplification can be summarized using a few notions of rapid distortion theory; second, the shock wave disturbances and the consequences on the apparent fluctuation level can be considered as a problem of intermittence. These two aspects are combined and interrelated, but the relative importance of intermittency effects depends mainly on the ratio c’/Δc- which represents the incident turbulence level and the mean step through the shock. This study examines the experimental case of free turbulence subjected to a shock wave. The evolution of the field of turbulence is characterized on the basis of scale and level measurements, and the shock wave disturbances are described using appropriate signal processing techniques. The results are compared with those obtained in two different types of phenomenological analysis: amplification by rapid distortion and secondly an intermittence diagram associated with rippling of the shock wave.
44 citations
01 Jan 1986
TL;DR: In this article, the three-dimensional oblique shock wave-turbulent boundary layer interaction generated by a sharp fin attached to a flat plate was investigated experimentally and theoretically for Mach 3 and Reynolds number 9 x 10 to the 5th using two different models.
Abstract: The three-dimensional oblique shock wave-turbulent boundary layer interaction generated by a sharp fin attached to a flat plate is investigated experimentally and theoretically for Mach 3 and Reynolds number 9 x 10 to the 5th using two different models. Both models employ the three-dimensional compressible Navier-Stokes equations in mass-averaged variables; one model utilizes the algebraic turbulent eddy viscosity model of Baldwin and Lomax (1978), while the other model employs the two-equation turbulence model of Jones and Launder (1972) coupled with the wall function model of Viegas and Rubesin (1985). The computed surface pressure, surface streamlines, pitot pressure, and yaw angle profiles are found to be in good agreement with experimental data. The three-dimensional velocity fields computed by both models are in close agreement, although the eddy viscosity profiles differ significantly within the three-dimensional interaction. This result indicates that the overall structure of this three-dimensional sharp fin interaction is insensitive to the turbulence model.
37 citations
TL;DR: In this paper, the authors describe an incident shock wave in a self-similar Mach number static pressure reflection point; point where RR = wave angle X,x' = first and second triple-point trajectory angles.
Abstract: incident shock wave in shock tube kink in CMR reflected wave R first and second Mach stems in DMR self-similar Mach number (M) , = (u + v)/a Mach reflection (SMR, CMR, DMR, TDMR) incident shock wave (/) Mach number static pressure reflection point; point where RR =wave angle X,x' = first and second triple-point trajectory angles
01 Jan 1986
TL;DR: In this paper, the effects of shock motion upon turbulence/unsteady vorticity are discussed. But, the authors do not address the effect of shock focusing on turbulence.
Abstract: Research within the past five years (e.g., References 1 to 5) identified a multitude of mechanisms whereby shock interactions can affect turbulence. These mechanisms include: (1) direct vorticity amplification, (2) production of vorticity from incident sound and entropy modes, (3) bulk compression and (4) shock-induced streamline curvature as “extra rates of strain,” (5) instantaneous shock focusing, and (6) direct effects of shock motion/dynamics/instability. The present paper addresses three facets of this last issue, the effects of shock motion upon turbulence/“unsteady vorticity.”
TL;DR: In this article, the three-dimensional interactions of weak swept oblique shock and expansion waves and a turbulent boundary layer on a flat plate are investigated, and upstream influences in a single swept interaction are found to be consistent with a model of the flow involving shock/boundary-layer interaction characteristics.
Abstract: The three-dimensional interactions of weak swept oblique shock and expansion waves and a turbulent boundary layer on a flat plate are investigated. Upstream influences in a single swept interaction are found to be consistent with a model of the flow involving shock/boundary-layer interaction characteristics. The model implies that there is more rapid thickening of the boundary layer close to the shock generator and this is seen to be consistent with surface streamline patterns. It is also found that a superposition principle, which is inherent in the triple-deck model of shock/boundary-layer interactions proposed by Lighthill, can be used to predict the pressure field and surface streamlines for the case of intersecting shock interactions and for the intersection of a shock with a weak expansion.
TL;DR: In this paper, an explosive charge (TNT) detonated at various heights of burst above a perfect reflecting planar surface in air is considered and a two-dimensional shock wave reflection transition map in the (Ms, Ow) plane is presented.
Abstract: Consideration is given to an explosive charge (TNT) detonated at various heights of burst above a perfect reflecting planar surface in air. Variations of the incident shock Mach number Ms of the spherical blast wave front as it decays and the corresponding wedge angle Ow are plotted on a two-dimensional shock wave reflection transition map in the (Ms, Ow) plane. It is shown that all four types of shock wave reflection (regular, single Mach, complex Mach, and double Mach) can occur in a free-air explosion. However, if the height of burst is increased past a certain limit, only two types of shock wave reflection can occur (regular and single Mach).
31 Aug 1986
TL;DR: In this article, an extensive series of numerical calculations of oblique-shock-wave reflections in air and argon have been performed using a version of the second-order Eulerian Godunov scheme for inviscid compressible flow.
Abstract: An extensive series of numerical calculations of oblique-shock-wave reflections in air and argon have been performed using a version of the second-order Eulerian Godunov scheme for inviscid compressible flow. This scheme is among the best of the upwind schemes developed in recent years. The results have been compared with the best available interferometric data from the UTIAS 10 cm x 18 cm shock tube, for fifteen different cases. The objective of this portion of the study was to assess the accuracy of the computer code in computing two-dimensional shocked flow of an inviscid perfect gas. A significant portion of our analysis is devoted to the question of the extent of influence of viscous and vibrational nonequilibrium effects on the experimental flow fields. Further parametrized series of calculations were performed in an effort to study the feasibility of numerically constructing inviscid transition lines in the (M/sub s/, theta/sub w/)-plane. Good agreement with analytic predictions was found for low values of M/sub s/ and, as might be expected, there are substantial discrepancies for M/sub s/ = 8.75. The possibility of using such numerical results in the formulation of accurate transition criteria is discussed. Overall, the computer code has been found to representmore » a significant predictive capability. The future extension of the code to permit the detailed modelling of nonequilibrium and viscous effects is, however, an important objective. 32 refs., 236 figs.« less
TL;DR: In this article, a shock wave tube generates a plane shock wave which is divided into two partial waves by means of a splitting device, such as a cone Adjacent the cone are first and second reflectors The reflectors have different parabolic curvatures and different distances from the cone Their respective foci coincide at a common point, where a concrement is located.
Abstract: A shock wave tube generates a plane shock wave which is divided into two partial waves by means of a splitting device, such as a cone Adjacent the cone are first and second reflectors The reflectors have different parabolic curvatures and different distances from the cone Their respective foci coincide at a common point, where a concrement is located The partial waves require different transit times to reach the common focus point Time-staggered shock waves are obtained in the concrement with the use of a single shock wave tube
TL;DR: In this article, the effects of pressure anisotropy and backstreaming heat flux on the fast and slow shock jump conditions are studied parametrically and the minimum critical Mach number is shown to increase from unity as qx becomes increasingly greater than qx.
Abstract: The effects of pressure anisotropy and backstreaming heat flux on the fast and slow shock jump conditions are studied parametrically. The fast shock jump condition can be brought into agreement with earth bow shock observations by (1) qx q: for Alfv6n Mach number MA > 10 in the quasi-perpendicular shock region (0BN > 45 o) where q and q: are the magnitude of the backstreaming heat flux on the upstream and downstream sides, respectively and 0aN is the angle between the upstream magnetic field and the shock normal. The slow shock jump condition is insensitive to the heat flux. However, slow shocks cease to exist if Pll = upstream and P ll > P- downstream where P ll and p_ are the pressure parallel and perpendicular to the local magnetic field. The minimum critical Mach number imposed by the entropy principle is shown to increase from unity as qx becomes increasingly greater than
01 Jan 1986
TL;DR: The cometary bow wave of P/Giacobini-Zinner has been analyzed using the complete set of ICE field and particle observations to determine if it is a shock as discussed by the authors.
Abstract: The cometary bow wave of P/Giacobini-Zinner has been analyzed using the complete set of ICE field and particle observations to determine if it is a shock Changes in the magnetic field and plasma flow velocities from upstream to downstream have been analyzed to determine the direction of the normal and the propagation velocity of the bow wave The velocity has then been compared with the fast magnetosonic wave speed upstream to derive the Mach number and establish whether it is supersonic, ie, a shock, or subsonic, ie, a large amplitude wave The various measurements have also been compared with values derived from a Rankine-Hugoniot analysis The results indicate that, inbound, the bow wave is a shock with M = 15 Outbound, a subsonic Mach number is obtained, however, arguments are presented that the bow wave is also likely to be a shock at this location
TL;DR: In this article, a magnetosonic shock wave propagating obliquely to a magnetic field is studied by theory and simulation, with particular attention to the resonant ion acceleration (the vp×B acceleration) by the shock.
Abstract: A magnetosonic shock wave propagating obliquely to a magnetic field is studied by theory and simulation, with particular attention to the resonant ion acceleration (the vp×B acceleration) by the shock. Theoretical analysis based on a two‐fluid model shows that, in the laminar shock, the electric field strength in the direction normal to the wave is about (mi/me)1/2 times larger for the quasiperpendicular shock than that for the quasiparallel shock, which is a reflection of the fact that the width of the quasiperpendicular shock is much smaller than that of the quasiparallel shock. Time evolution of a totally self‐consistent magnetosonic shock wave is studied by using a 2 1/2 ‐dimensional fully relativistic, fully electromagnetic particle simulation with full ion and electron dynamics. Even the low Mach number shock wave can significantly accelerate some ions by the vp×B acceleration. The resonant ion acceleration occurs more strongly in the quasiperpendicular shock, because the magnitude of this accelerat...
TL;DR: In this article, a geostrophic wave is defined as a wave whose horizontal projection is a straight line perpendicular to the side walls, and the wave is constructed analytically using power series expansions and shock conditions equivalent to the Rankine-Hugoniot constraints.
Abstract: Organized depth discontinuities involving a balance between steepening and dissipation are usually referred to as shock waves. An analytical “educed gravity” model is used to examine a special kind of shock wave. The wave under study is a depth discontinuity associated with a transition between a supercritical and subcritical flow in a channel. Even though the wave itself is highly nonlinear, the adjacent upstream and downstream fields are exactly geostrophic in the cross-stream direction. For this reason we term the wave a geostrophic shock wave. We focus on a stationary shock wave whose horizontal projection is a straight line perpendicular to the side walls. Solutions for the entire field are constructed analytically using power series expansions and shock conditions equivalent to the so-called Rankine-Hugoniot constraints. It is found that, for particular upstream conditions, a geostrophic shock wave can be formed if the particle speed exceeds the surface gravity wave speed (i.e., the flow is...
TL;DR: In this article, a procedure for the calculation of a supersonic flow near axisymmetric blunt bodies with protruding spikes is developed, and the flow past a frustum of a cone with a protruding spherically blunt cylindrical spike is studied.
Abstract: A procedure for the calculation of a supersonic flow of ideal gas near axisymmetric blunt bodies with protruding spikes is developed. The flow past a frustum of a cone with a protruding spherically blunt cylindrical spike as a dependence on the ratio K of the spike length1 to the diameter D of the flat end of the body and the Mach number M of the oncoming flow is studied. Several steady flow regimes are obtained, including the formation of circulation zones and internal shock waves in the shock layer. It is shown that mounting a spike in front of the frustum of a cone can lead to a 40–50% reduction in its drag. A full investigation of the variation of the drag coefficient as a dependence on K is carried out for M = 3.
TL;DR: In this article, an analysis for predicting the performance of side-exhausting scarfed propulsive nozzles is presented, where the oblique shock wave that emanates from the junction of the nozzle and the nozzle extension is fitted discretely and tracked through the flowfield.
Abstract: An analysis for predicting the performance of side-exhausting scarfed propulsive nozzles is presented. Nozzles of this type consist of a conventional axisymmetric nozzle followed by a scarfed conical extension. They are employed in situations where the exhaust jet must exit through the side of a missile. The flowfield model assumes that the flow within the nozzle is axisymmetric, and that the overall nozzle pressure ratio is high enough to preclude shock waves or flow separation at the nozzle exit. The flowfield is calculated by the method of characteristics. The oblique shock wave that emanates from the junction of the nozzle and the nozzle extension is fitted discretely and tracked through the flowfield. The forces and moments acting on the scarfed nozzle and the missile are determined. The results of an extensive parametric study are presented. Comparisons with experimental measurements are presented to verify the analysis.
TL;DR: In this article, the authors investigated how the effects of thermal radiation and magnetic field strength influence the steepening and flattening of wave fronts and found that in an optically thick gas with negligible radiation pressure and energy, an increase in the radiative flux reduces the shock formation distance.
TL;DR: In this article, a time-dependent method is applied to the solution of the fully coupled gas/particle, quasi-one-dimensional flow within nozzles, and the results obtained show that the complexity of the sock pattern is dependent on loading ratio and particle diameter, and that the strength of the shock is strongly influenced by the presence of the particles.
Abstract: A time-dependent method is applied to the solution of the fully coupled gas/particle, quasi-one-dimensional flow within nozzles. This time-dependent method is noted to yield good resolution over the entire flow region, despite its inclusion of subsonic, transonic, and supersonic flow regimes, including shock phenomena. The results obtained show that the complexity of the sock pattern is dependent on loading ratio and particle diameter, and that the strength of the shock is strongly influenced by the presence of the particles. 13 references.
TL;DR: In this paper, the flow that results when a shock wave in a dusty gas is reflected from a rigid wall is studied theoretically, by applying an idealized equilibrium gas analysis, it is shown that there are three types of shock reflection.
Abstract: The flow that results when a shock wave in a dusty gas is reflected from a rigid wall is studied theoretically. By applying an idealized equilibrium gas analysis, it is shown that there are three types of shock reflection. The incident shock wave and the reflected shock wave are partly dispersed if the incident shock is strong the former is partly dispersed but the latter is fully dispersed if the incident shock is of intermediate strength and both of them are fully dispersed if the incident shock is weak. The equations of motion are also solved numerically with a modified random-choice method involving an operator splitting technique to study the time-dependent non-equilibrium flow. The results demonstrate the details of the formation of the reflected shock wave for the three types described.
TL;DR: In this article, the interaction between an oblique shock wave and a laminar boundary layer in a supercritical transonic flow is studied numerically for shock strengths sufficiently large that separation occurs.
TL;DR: In this paper, a baryon-quark phase transition was shown to affect the flow of nuclear matter in relativistic heavy ion collisions through an oblique shock wave.
TL;DR: In this article, the authors examined the relationship between the internal degrees of freedom (DOF) and the length of the flow in a pseudostationary flow with respect to the angle between the incident and the reflected shock waves.
Abstract: Many experiments in various gases have now been performed on regular and Mach reflection of oblique shock waves in pseudostationary flow. Experimental agreement with the analytical boundaries for such reflections with two- and three-shock theories is reasonable but not precise enough over the entire range of incident shock-wave Mach numbers ( M s ) and compression wedge angle ( θ W ) used in the experiments. In order to improve the agreement, the assumptions and criteria employed in the analysis were critically examined by the use of the experimental data for nitrogen (N 2 ), argon (Ar), carbon-dioxide (CO 2 ), air and sulphurhexa-fluoride (SF 6 ). The assumptions regarding the excitation of the internal degrees of freedom were evaluated based on a relation between the relaxation lengths and a characteristic length of the flow. The ranges in which the frozen-gas and vibrational-equilibrium-gas assumptions can be applied were verified by comparing the experimental and numerical values of δ, the angle between the incident and the reflected shock waves. The deviations of the experimental orientation of the Mach stem at the triple point from a line perpendicular to the wedge surface were considered. A new criterion for the transition from single-Mach to complex-Mach reflection improved the agreement with experiments in the ( M S , θ W )-transition-boundary map. The effects of the shock-induced boundary layer on the wedge surface on the reflected-wave angle and the persistence of regular reflection into the Mach reflection region (‘von Neumann paradox’) were evaluated.
20 Feb 1986
TL;DR: In this paper, an analytical model for the interaction between a moving shock and a thin thermal layer of semi-infinite extent is presented, where the fluid is assumed to be inviscid and ideal.
Abstract: : An analytical model is presented for the interaction between a moving shock and a thin thermal layer of semi-infinite extent. The fluid is assumed to be inviscid and ideal. The model is based on flow field characteristics deduced from the detailed numerical code calculations of Schneyer and Wilkins (1984). Flow field properties of interest include the peak surface (stagnation) pressure at the base of the incident shock, the forward extent of the shock-induced precursor, and the surface pressure at the latter location. Good agreement with Schneyer and Wilkins is obtained subject to appropriate choice of an arbitrary constant k introduced into the analytical model. Further validation of the model is needed. Keywords: Nuclear Blast; Shock Wave; Thermal Layer; Thermal Precursor.
01 Jan 1986
TL;DR: In this paper, the effect of elasticity and permeability of the porous material structure on the parameters of pressure pulse on the rigid wall was studied qualitatively, with the ideal model of propagation and the reflection of shock waves in a porous material taken as a homogeneous mixture.
Abstract: This paper reports on the results of experimental studies of the interaction of plane shock waves in air and a rigid wall coated with flat layers of expanded polymers (polyurethane and polystyrene). The experiments were carried out in a standard shock tube with a cross section of 0.1x0.1 m and a diaphragm. The initial pressure of air in the test section was 10 Pa. Helium or nitrogen was used as driving gas. The Mach number of incident shock wave was varied from 1.1 to 2.7. The pressure on the wall behind the tested material and behind the incident and reflected shock waves were measured with piezoelectric gages. The pressure profile on the wall was measured through layers of porous material of different thicknesses. The peak pressures measured on the wall behind polyurethane at various Mach numbers of incident wave are compared to the calculated values, with the ideal model of propagation and the reflection of shock waves in a porous material taken as a homogeneous mixture. The effect of elasticity and permeability of the porous material structure on the parameters of pressure pulse on the rigid wall is studied qualitatively. The results of the experiments with a wall made of two polyurethane layers of different density are