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Results for “Shock-induced compression”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1973

Shock remagnetization associated with meteorite impact at planetary surfaces

The stages of a cratering event are considered together with four distinct magnetization volumes, taking into account the jetted material, the ejecta, the impact melt, and shock-compressed material which remains in situ. Shock classifications are discussed along with mineralogical aspects of shock remagnetization, the behavior of iron sulfides, defect cubic spinels, ilmenite-hematite series, the Fe-Ti-O system, alloys phases, and silicates. Remagnetization mechanisms considered include a first order reversible crystallographic transition in bcc iron-nickel, a second order Curie point transition in fcc iron-nickel, shock-induced anisotropy, and shock melting of iron containing silicates. Experimental results are reported together with a hypothetical crater model.

Wasilewski, P. J.↗
NASA NTRS1973

Shock compression of a recrystallized anorthositic rock from Apollo 15

Hugoniot measurements on 15,418, a recrystallized and brecciated gabbroic anorthosite, yield a value of the Hugoniot elastic limit (HEL) varying from 45 to 70 kbar as the final shock pressure is varied from 70 to 280 kbar. Above the HEL and to 150 kbar, the pressure-density Hugoniot is closely described by a hydrostatic equation of state constructed from ultrasonic data for single-crystal plagioclase and pyroxene. Above 150 kbar, the Hugoniot states indicate that a series of one or more shock-induced phase changes are occurring in the plagioclase and pyroxene. From Hugoniot data for both the single-crystal minerals and the Frederick diabase, we infer that the shock-induced high-pressure phases in 15,418 probably consists of a 3.71 g/cu cm density, high-pressure structure for plagioclase and a 4.70 g/cu cm perovskite-type structure for pyroxene.

Ahrens, T. J.↗
NASA NTRS1975

Control of shock wave-boundary layer interactions by bleed in supersonic mixed compression inlets

An experimental investigation was conducted to determine the effect of bleed on a shock wave-boundary layer interaction in an axisymmetric mixed-compression supersonic inlet. The inlet was designed for a free-stream Mach number of 2.50 with 60-percent supersonic internal area contraction. The experiment was conducted in the NASA Lewis Research Center 10-Foot Supersonic Wind Tunnel. The effects of bleed amount and bleed geometry on the boundary layer after a shock wave-boundary layer interaction were studied. The effect of bleed on the transformed form factor is such that the full realizable reduction is obtained by bleeding of a mass flow equal to about one-half of the incident boundary layer mass flow. More bleeding does not yield further reduction. Bleeding upstream or downstream of the shock-induced pressure rise is preferable to bleeding across the shock-induced pressure rise.

Fukuda, M. K.↗
NASA NTRS1977

An experimental and computational investigation of the steady and unsteady transonic flow fields about an airfoil in a solid-wall test channel

An experimental and computational investigation of the steady and unsteady transonic flow field about a thick airfoil is described. An operational computer code for solving the two-dimensional, compressible Navier-Stokes equations for flow over airfoils was modified to include solid-wall, slipflow boundary conditions to properly assess the code and help guide the development of improved turbulence models. Steady and unsteady flow fields about an 18% thick circular arc airfoil at Mach numbers of 0.720, 0.754, and 0.783 and a chord Reynolds number of 11 x 10 to the 6th are predicted and compared with experiment. For the first time, computed results for unsteady turbulent flows with separation caused by a shock wave were obtained which qualitatively reproduce the time-dependent aspects of experiments. Features such as the intensity and reduced frequency of airfoil surface-pressure fluctuations, oscillatory regions of trailing-edge and shock-induced separation, and the Mach number range for unsteady flows were all qualitatively reproduced.

Levy, L. L., Jr.↗
NASA NTRS1978

Injection slot location for boundary-layer control in shock-induced separation

An experimental investigation of the effect of tangential air injection, when the injection slot is located inside of what would otherwise have been the dead air zone in a separated flow, in controlling shock-induced turbulent boundary layer separation is presented. The experiments were carried out at a free-stream Mach number of 2.5 in the separated flow induced by a compression corner with a 20 deg angle. The observations made were wall static pressures, pitot profiles, and schlieren visualizations of the flow. The results show that the present location for injection is more effective in suppressing boundary-layer separation than the more conventional one, where the slot is located upstream of where separation would occur in the absence of injection.

Viswanath, P. R.↗
NASA NTRS1982

Computations of transonic flow over an oscillating airfoil with shock-induced separation

A numerical study is presented on unsteady transonic flow over an airfoil in pitching oscillation at a moderately high incidence. The study was focused on the effects of unsteady shock-wave/boundary-layer interactions and subsequent flow separations. An implicit finite-difference scheme was used to solve the full time-dependent compressible Navier-Stokes equations in conservation-law form. The algorithm adopted for this study is the Beam-Warming spatially factored scheme. It is, however, constructed in a body-fitted curvilinear coordinate system for efficient unsteady flow computations. The computational results are compared with experimental data measured in the Ames 11- by 11-Foot Transonic Wind Tunnel.

Chyu, W. J.↗
NASA NTRS1983

On a finite-difference method for solving transient viscous flow problems

A method has been developed to solve the unsteady, compressible Navier-Stokes equation with the property of consistency and the ability of minimizing the equation stiffness. It relies on innovative extensions of the state-of-the-art finite-difference techniques and is composed of: (1) the upwind scheme for split-flux and the central scheme for conventional flux terms in the inviscid and viscous regions, respectively; (2) the characteristic treatment of both inviscid and viscous boundaries; (3) an ADI procedure compatible with interior and boundary points; and (4) a scalar matrix coefficient including viscous terms. The performance of this method is assessed with four sample problems; namely, a standing shock in the Laval duct, a shock reflected from the wall, the shock-induced boundary-layer separation, and a transient internal nozzle flow. The results from the present method, an existing hybrid block method, and a well-known two-step explicit method are compared and discussed. It is concluded that this method has an optimal trade-off between the solution accuracy and computational economy, and other desirable properties for analyzing transient viscous flow problems.

Li, C. P.↗
NASA NTRS1985

Structure of the wall pressure fluctuations in a shock-induced separated turbulent flow

This paper presents the results of an experimental study of the unsteady nature of a shock wave/turbulent boundary layer interaction. The interaction was generated using an unswept compression ramp. The incoming freestream Mach number was 2.9 and the flow was separated at the corner. An array of flush mounted miniature high frequency pressure transducers was used to make multi-channel measurements of the fluctuating wall pressure within the interaction. From the present results, an overall picture of the instantaneous structure of the unsteady shock system (as inferred from the wall pressure signals) can be constructed. The flow ahead of the corner can be considered as composed of two regions, namely the 'intermittent' region where there is essentially a single leading shock which exhibits significant streamwise 'flapping' and spanwise 'rippling', and the separated region where the flow experiences continuous compression.

Muck, K. C.↗
NASA NTRS1987

Numerical simulation of three-dimensional supersonic inlet flow fields

Supersonic inlet flows with mixed external-internal compressions of an axisymmetric inlet model were computed using a combined implicit-explicit (Beam-Warming-Steger/MacCormack) method for solving the three-dimensional unsteady, compressible Navier-Stokes equations in conservation form. Numerical calculations were made of various flows typically found in supersonic inlets such as shock-wave intersections, flow spillage around the cowl lip, shock-wave/boundary-layer interactions, control of shock-induced flow separation by means of boundary layer bleed, internal normal (terminal) shocks, and the effects of flow incidence. Computed results were compared with available wind tunnel data.

Kawamura, T.↗
NASA NTRS1988

Shock-induced melting and shear banding in single-crystal NaCl

Radiative color temperatures were measured in single-crystal sodium chloride under shock compression parallel to 100-line orientation over a pressure range from 20 to 35 GPa. Color temperatures from 2500 to 4500 K and emittances from 0.003 to 0.3 were determined by fitting observed spectra (450-850 nm) to the Planck greybody radiation law. These data support a heterogeneous shock deformation model of shocked halite in this pressure range. A 2500-K temperature rise, of unknown origin, is observed over the B1-B2 mixed phase region from 25 to 30 GPa. Assuming that shock deformation occurs via yielding in localized planar zones which become melt and the melting temperature at high pressure controls the temperature, it is inferred that the temperature of the B2 fusion curve from 30 to 35 GPa rises from 3200 to 3300 K. The B1-B2-liquid triple point is predicted to be at a temperature of 2250 K and 23.5 GPa.

Schmitt, Douglas R.↗
NASA NTRS1988

The effects of compressibility on dynamic stall

In this paper, typical computational predictions and experimental measurements of compressible flow past an airfoil at dynamic stall conditions are studied and compared to develop an insight into the effect of compressibility on dynamic stall. The dependency of the critical Mach number on airfoil leading edge curvature, camber, and angle of attack is investigated. Evidence is presented to show that a local region of supersonic flow occurs on an oscillating airfoil, even for a freestream Mach number as low as 0.2, if the boundary layer remains attached and the angle of attack is sufficiently high; that a shock terminates this local supersonic bubble; and that the vorticity that this shock generates grows rapidly and becomes very unstable as the angle of attack increases beyond the value at which the maximum local flow speed first exceeds the speed of sound. It is suggested that these shock-induced effects compete with the dynamic viscous effects occurring in the boundary layer in determining the onset of separation, which can lead to premature dynamic stall and can significantly reduce the maximum dynamic lift that can otherwise be obtained.

Fung, K.-Y.↗
NASA NTRS1989

Separation shock motion in fin, cylinder, and compression ramp - Induced turbulent interactions

In conjunction with new experimental results at Mach 5, an examination has been made of published data on unsteadiness of shock-induced turbulent boundary-layer separation. The data are all wall pressure fluctuation measurements made under the unsteady separation shock and are from interactions induced by compression ramps, blunt and sharp fins, and circular cylinders. There is little evidence of a link between the separation shock zero-crossing frequency and characteristic frequency of the incoming boundary layer. The low shock frequencies and low shock speeds, and the trends with changes in model geometric parameters and incoming boundary layer, suggest that turbulent or global fluctuations at the upstream boundary of the separated flow drive the shock motion.

Dolling, D. S.↗
NASA NTRS1989

Shock temperatures in silica glass - Implications for modes of shock-induced deformation, phase transformation, and melting with pressure

Observations of shock-induced radiative thermal emissions are used to determine the gray body temperatures and emittances of silica glass under shock compression between 10 and 30 GPa. The results suggest that fused quartz deforms heterogeneously in this shock pressure range. It is shown that the 10-16 GPa range coincides with the permanent densification region, while the 16-30 GPa range coincides with the inferred mixed phase region along the silica glass Hugoniot. Low emittances in the mixed phase region are thought to represent the melting temperature of the high-pressure phase, stishovite. Also, consideration is given to the effects of pressure on melting relations for the system SiO2-Mg2SiO4.

Schmitt, Douglas R.↗
NASA NTRS1989

A numerical analysis of the British Experimental Rotor Program blade

Two Computational Fluid Dynamic codes which solve the compressible full-potential and the Reynolds-Averaged Thin-Layer Navier-Stokes equations were used to analyze the nonrotating aerodynamic characteristics of the British Experimental Rotor Program (BERP) helicopter blade at three flow regimes: low angle of attack, high angle of attack and transonic. Excellent agreement was found between the numerical results and experiment. In the low angle of attack regime, the BERP had less induced drag than a comparable aspect ratio rectangular planform wing. At high angle of attack, the blade attained high-lift by maintaining attached flow at the outermost spanwise locations. In the transonic regime, the BERP design reduces the shock strength at the outer spanwise locations which affects wave drag and shock-induced separation. Overall, the BERP blade exhibited many favorable aerodynamic characteristics in comparison to conventional helicopter rotor blades.

Duque, Earl P. N.↗
NASA NTRS1990

Shock-induced temperatures of CaMgSi2O6

Results are presented from experiments on CaMgSi2O6 (diopside) single crystal, an end-member pyroxene relevant to studies of the composition of the earth's mantle. Also, experiments were conducted on diopside glass with a density 86 percent that of the diopside crystal. The shock-induced radiation from diopside is used to constrain the temperature of its shock-compressed (Hugoniot) states. The results are combined with other data to place constraints on the high-pressure phase relations in the CaMgSi2O6 system. These constraints are compared with existing models for the earth's mantle. The results imply that the temperature of the D-double prime region must be less than 3000 K.

Svendsen, Bob↗
NASA NTRS1992

Shock-induced transformations in the system NaAlSiO4-SiO2 - A new interpretation

New internally consistent interpretations of the phases represented by the high pressure phase shock wave data for an albite-rich rock, jadeite, and nepheline in the system NaAlSiO4-SiO2, are obtained using the results of static high pressure investigations, and the recent discovery of the hollandite phase in a shocked meteorite. We conclude that nepheline transforms directly to the calcium ferrite structure, whereas albite transforms possibly to the hollandite structure. Shock Hugoniots for the other plagioclase and alkali feldspars also indicate that these transform to hollandite structures. The pressure-volume data at high pressure could alternatively represent the compression of an amorphous phase. Moreover, the shock Hugoniot data are expected to reflect the properties of the melt above shock stresses of 60-80 GPa. The third order Birch-Murnaghan equation of state parameters are given for the calcium ferrite type NaAlSiO4 and for albite-rich, orthoclase-rich, and anorthite-rich hollandites.

Sekine, Toshimori↗
NASA NTRS1995

Collapse and fragmentation of molecular cloud cores. 2: Collapse induced by stellar shock waves

The standard scenario for low-mass star formation involves 'inside-out' collapse of a dense molecular cloud core following loss of magnetic field support through ambipolar diffusion. However, isotopic anomalies in presolar grains and meteoritical inclusions imply that the collapse of the presolar cloud may have been triggered by a stellar shock wave. This paper explores 'outside-in' collapse, that is, protostellar collapse initiated directly by the compression of quiescent dense cloud cores impacted by relatively slow stellar shock waves. A second-order accurate, gravitational hydrodynamics code has been used to study both the spherically symmetrical and three-dimensional evolution of initially centrally condensed, isothermal, self-gravitating, solar-mass cloud cores that are struck by stellar shock waves with velocities up to 25 km/s and postshock temperatures of 10 to 10,000 K. The models show that such mild shock waves do not completely shred and destroy the cloud, and that the dynamical ram pressure can compress the cloud to the verge of self-gravitational collapse. However, compression caused by a high postshock temperature is a considerably more effective means of inducing collapse. Shock-induced collapse produces high initial mass accretion rates (greater than 10(exp -4) solar mass/yr in a solar-mass cloud) that decline rapidly to much lower values, depending on the presence (approximately 10(exp -6) solar mass/yr) or absence (approximately 10(exp -8) to 10(exp -7) solar mass/yr) of an infinite reservoir of mass. Stellar mass accretion rates approximately 10(exp -7) solar mass/yr have been previously inferred from the luminosities of T Tauri stars; balanced mass accretion (stellar rate = envelope rate) at approximately 10(exp -7) solar mass/yr could then be possible if accretion occurs from a finite mass reservoir. Fluid tracers are used to determine what fraction of the stellar shock material is incorporated into the resulting protostellar object and disk; roughly half the impinging material is injected into the collapsing cloud core when there is a high postshock temperature. The models are consistent with a scenario where an AGB star wind triggered the collapse of the presolar cloud while injecting about 0.01 solar mass of matter derived from the AGB star envelope, as has been separately inferred on the basis of nucleosynthesis calculations.

Boss, Alan P.↗
NASA NTRS1994

Shock waves data for minerals

Shock compression of the materials of planetary interiors yields data which upon comparison with density-pressure and density-sound velocity profiles constrain internal composition and temperature. Other important applications of shock wave data and related properties are found in the impact mechanics of terrestrial planets and solid satellites. Shock wave equation of state, shock-induced dynamic yielding and phase transitions, and shock temperature are discussed. In regions where a substantial phase change in the material does not occur, the relationship between the particle velocity, U(sub p), and the shock velocity, U(sub s), is given by U(sub s) = C(sub 0) + S U(sub p), where C(sub 0) is the shock velocity at infinitesimally small particle velocity, or the ambient pressure bulk sound velocity. Numerical values for the shock wave equation of state for minerals and related materials of the solar system are provided.

Ahrens, Thomas J.↗