Search NASA⌕ Search

SEARCH · Search NASA

Results for “conical shocks”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

The behavior of a compressible turbulent boundary layer in a shock-wave-induced adverse pressure gradient

The results of an experimental investigation of the mean- and fluctuating-flow properties of a compressible turbulent boundary layer in a shock-wave-induced adverse pressure gradient are presented. The turbulent boundary layer developed on the wall of an axially symmetric nozzle and test section whose nominal free-stream Mach number and boundary-layer thickness Reynolds number were 4 and 100,000, respectively. The adverse pressure gradient was induced by an externally generated conical shock wave. Mean and time-averaged fluctuating-flow data, including the complete experimental Reynolds stress tensor and experimental turbulent mass- and heat-transfer rates are presented for the boundary layer and external flow, upstream, within and downstream of the pressure gradient. The mean-flow data include distributions of total temperature throughout the region of interest. The turbulent mixing properties of the flow were determined experimentally with a hot-wire anemometer. The calibration of the wires and the interpretation of the data are discussed. From the results of the investigation, it is concluded that the shock-wave - boundary-layer interaction significantly alters the turbulent mixing characteristics of the boundary layer.

Rose, W. C.↗
NASA NTRSDate not supplied

Numerical Simulations of an Axisymmetric Shock-Wave/Boundary-Layer Interaction

A series of Reynolds-averaged Navier-Stokes (RANS) simulations were performed of two Mach 2.5 axisymmetric shock-wave/boundary-layer interactions (SWBLIs) based off of the NASA Turbulent Computational Fluid Dynamics Validation Experiment (TCFDVE). The goals of the simulations were to (1) determine how well RANS can predict the flow physics of an axisymmetric SWBLI and (2) generate a new validation case for the NASA Turbulence Modeling Resource (TMR). The simulations were run with two different turbulence models and three different computational fluid dynamics (CFD) codes while looking at two different conical shock generator angles, one of which was shown to cause flow separation in the experiment. The results in this paper show that, as expected, the CFD simulations agreed well with each other and the experiment when SWBLI-induced separation was not present. When separation was present, differences in the predicted separation characteristics were noted. These included a stronger interaction and subsequently longer separation extent for the Menter Shear-Stress Transport k-ω (SST) turbulence model simulations compared to both the Spalart-Allmaras (SA) turbulence model simulations and the experiment.

Computational Fluid Dynamics↗
NASA NTRS1985

Computation of transonic vortex flows past delta wings Integral equation approach

The steady full-potential equation is written in the form of Poisson's equation, and the solution of the velocity field is expressed in terms of an integral equation. The solution consists of a surface integral of vorticity distribution on the wing and its free-vortex sheets and a volume integral of source distribution within a volume around the wing and its free-vortex sheets. The solution is obtained through successive iteration cycles. The source distribution is computed by using a mixed finite-difference scheme of the Murman-Cole type. The method is applied to delta wings. Numerical examples show that a conical shock is captured on the suction side of the wing. It is attached to the lower surface of the leading-edge vortex but does not necessarily reach to the wing surface.

Kandil, O. A.↗
NASA NTRS1986

Optical elements formed by compressed gases: Analysis and potential applications

Spherical, cylindrical, and conical shock waves are optically analogous to gas lenses. The geometrical optics of these shock configurations are analyzed as they pertain to flow visualization instruments, particularly the rainbow schlieren apparatus and single-pass interferometers. It is proposed that a lens or mirror formed by gas compressed between plastic sheets has potential as a fluid visualization test object; as the objective mirror in a very large space-based telescope, communication antenna, or energy collector; as the objective mirror in inexpensive commercial telescopes; and as a component in fluid visualization apparatuses.

Howes, W. L.↗
NASA NTRS1993

Design project: LONGBOW supersonic interceptor

A recent white paper entitled 'From the Sea' has spotlighted the need for Naval Aviation to provide overland support to joint operations. The base for this support, the Aircraft Carrier (CVN), will frequently be unable to operate within close range of the battleground because of littoral land-based air and subsurface threats. A high speed, long range, carrier capable aircraft would allow the CVN to provide timely support to distant battleground operations. Such an aircraft, operating as a Deck-Launched Interceptor (DLI), would also be an excellent counter to Next Generation Russian Naval Aviation (NGRNA) threats consisting of supersonic bombers, such as the Backfire, equipped with the next generation of high-speed, long-range missiles. Additionally, it would serve as an excellent high speed Reconnaissance airplane, capable of providing Battle Force commanders with timely, accurate pre-mission targeting information and post-mission Bomb Damage Assessment (BDA). Recent advances in computational hypersonic airflow modeling has produced a method of defining aircraft shapes that fit a conical shock flow model to maximize the efficiency of the vehicle. This 'Waverider' concept provides one means of achieving long ranges at high speeds. A Request for Proposal (RFP) was issued by Professor Conrad Newberry that contained design requirements for an aircraft to accomplish the above stated missions, utilizing Waverider technology.

Stoney, Robert↗
NASA NTRS1993

31 Cygni: The B star and the wind

I have followed photospheric and wind absorptions in International Ultraviolet Explorer (IUE) spectra over much of the orbit of this K4 Ib+B3-4 binary system, using interstellar lines to transform all the velocities to a scale with the interstellar medium at -10.1 km/s. Results are as follows: Interstellar Fe II lines give NL (Fe(+)) = 1-2 x 10(exp 14)/sq cm with a Doppler width of 7 km/s; depletions of heavy elements along the line of sight to this star are similar to those for other stars with low interstellar densities. Photospheric lines yield a new velocity amplitude for the B star, K(sub B) = 23.2 +/- 1.0 km/s, which gives the mass ratio M(sub K)/M(sub B) = 1.66 and masses M(sub B) = 7.1 solar mass and M(sub K) = 11.7 solar mass. Existing photometry gives R(sub K) = 197 solar radius, R(sub B) = 5.2 solar radius, and i = 87.19 deg. Breadths of photospheric lines imply the rotational velocity of the B star is V sin i = 70-80 km/s. Most of the wind features are formed in a shell much larger than the binary system for which the terminal velocity seems to be 73 +/- 2 km/s, but it may be as high as approximately 90 km/s. The Doppler width (approximately 13 km/s) of Fe II shell lines likely results from acceleration of the wind, although it could reflect orbital motion of the K supergiant. Shell lines of Mg II and Si II are roughly consistent with Fe II, although their strengths are phase dependent, while S II requires a somewhat thicker shell in S(+) than in Fe(+) with a greater spread in expansion velocity. Shell lines of O I and N I are abnormally weak, if detected at all, and this implies that hydrogen is ionized throughout much of the wind. Lines of highly ionized species (C IV, Si Iv, and N V) appear sporadically in the spectrum and have inverse P Cyg profiles implying collapse (probably of an accretion disk) onto the B star. They do not seem to be isolated at particular phases as might be expected for formation in a conical shock front around an accretion column. I argue that the wind is roughly isotopic and is accelerated slowly, in agreement with existing ideas about winds.

Eaton, Joel A.↗
NASA NTRS2001

Jet Stability and the Generation of Superluminal and Stationary Components

We present a numerical simulation of the response of an expanding relativistic jet to the ejection of a superluminal component. The simulation has been performed with a relativistic time-dependent hydrodynamical code from which simulated radio maps are computed by integrating the transfer equations for synchrotron radiation. The interaction of the superluminal component with the underlying jet results in the formation of multiple conical shocks behind the main perturbation. These trailing components can be easily distinguished because they appear to be released from the primary superluminal component instead of being ejected from the core. Their oblique nature should also result in distinct polarization properties. Those appearing closer to the core show small apparent motions and a very slow secular decrease in brightness and could be identified as stationary components. Those appearing farther downstream are weaker and can reach superluminal apparent motions. The existence of these trailing components indicates that not all observed components necessarily represent major perturbations at the jet inlet; rather, multiple emission components can be generated by a single disturbance in the jet. While the superluminal component associated with the primary perturbation exhibits a rather stable pattern speed, trailing components have velocities that increase with distance from the core but move at less than the jet speed. The trailing components exhibit motion and structure consistent with the triggering of pinch modes by the superluminal component. The increase in velocity of the trailing components is an indirect consequence of the acceleration of the expanding fluid, which is assumed to be relativistically hot; if observed, such accelerations would therefore favor an electron-positron (as opposed to proton rest mass) dominated jet.

Agudo, Ivan↗
NASA NTRS1987

Mach number effects on conical surface features of swept shock boundary-layer interactions

A joint experimental and computational study is made of the shock-wave turbulent boundary-layer interaction generated by sharp fins, with emphasis on Mach-number effects. The Mach number range is from 2 to 4 and the unit Reynolds number is from 50 to 80 million per meter. Fin angles are varied from 4 to 22 deg. Surface-flow patterns are obtained using a color surface-flow-visualization technique. The results show that the upstream-influence response in the conical far-field region is a function of the freestream Mach number and the shock strength. A new interpretation of the behavior of the upstream influence with changes of the inviscid shock angle is given. Agreement between the experimental and the computed upstream-influence lines becomes poorer for stronger interactions, with the computations underpredicting the upstream-influence line.

Lu, F. K.↗
NASA NTRS2026

Experimental Demonstration of a Supersonic Spike Ejector

Spike diffusers are presented as a means to improve supersonic ejector efficiency via reduction in shock losses. Design, fabrication, and testing of an articulated prototype is described. Experimental results are compared to empirical performance curves representing the loci of optimal one- and two-stage conventional ejectors driven by dry air and discharging to atmosphere. Operated at a compression ratio of ~10 with all inputs equal, the spike ejector is shown to have achieved up to 2.19X and 1.83X the secondary mass throughput of the one- and two-stage references, respectively. This suggests the potential of spike diffusers to reduce ejector operating costs by ~50%.

wind tunnel↗
NASA NTRS1972

Experimental study of wall boundary layer growth in the 10 deg half angle conical nozzle of a reflected shock tunnel

Calibration studies of shock-tunnel nozzle flow were made in both N2 and Ar for a reservoir temperature of 2000 deg K and reservoir pressures of 15, 85, and 130 atm. The results for both test gases showed that the boundary layer was turbulent and the growth nonlinear, with the thickness being greater in Ar than N2 at comparable reservoir conditions. The boundary-layer thickness decreased with increasing reservoir pressure, but only small differences occurred between the two largest reservoir pressures. Good correlations of the boundary layer and displacement thickness were obtained for both N2 and Ar in terms of Reynolds number based on a reference temperature.

Menees, G. P.↗
NASA NTRS2002

An Experimental Study of Nonlinear Standing Waves in Resonators with Numerical Comparison

Lawrenson et. al. [Journal of the Acoustic Society of America, Nov. 1998] described the generation of shock-free high-amplitude pressure waves in closed cavities using large equipment and resonators to produce the reported effects. An attempt is made to generate shock-free high-amplitude pressure waves using relatively small resonators. Ambient air is used as the working fluid. A small cylindrical resonator is tested resulting in the lack of a shocked waveform while a larger model of the same shape produces shock waves. A small conical resonator produces shock-free pressure waves at resonance, but the amplitude of these waves is small. A larger cone resonator model produces shock-free pressure waves of higher amplitude. A large horn-cone resonator also produces shock-free high amplitude pressure waves, A numerical model is used to compare the experimental results to theoretical results. The effects of structural resonances on the production of shock-free high-amplitude pressure waves are discussed, especially concerning difficulties encountered when these resonances were in the frequency ranges of interest. Identifying features of a structural resonance are presented.

Finkbeiner, Joshua R.↗
NASA NTRS1992

A study of hypersonic swept shock wave/turbulent boundary layer interactions using a conical Navier-Stokes code

A computational study has been performed of sharp fin-induced swept shock wave/turbulent boundary layer interactions at low hypersonic Mach numbers. The objective was to determine if results obtained using a conical Navier-Stokes code, particularly the peak heating and pressure, are adequate for engineering predictions. The advantage of the conical approach is that the problem becomes two-dimensional and requires much less computational effort than a fully three-dimensional calculation. In this code, the standard Baldwin-Lomax model is used for turbulent closure and its performance is studied in some detail. To assess the approach interactive flowfields generated by unswept sharp fins at two angles of attack at each of three hyprsonic freestream Mach numbers (5, 6, 11) have been calculated and the results compared with experimental wall pressure and heat transfer data. Although the conical Navier-Stokes/Baldwin-Lomax approach is reasonably successful at Mach numbers up to 5, the performance deteriorates as the Mach number is increased. Nevertheless, the approach could be a valuable tool in preliminary parametric design studies.

Rodi, Patrick E.↗
NASA NTRS1991

On the quasi-conical flowfield structure of the swept shock wave-turbulent boundary layer interaction

The swept oblique shock-wave/turbulent-boundary-layer interaction generated by a 20-deg sharp fin at Mach 4 and Reynolds number 21,000 is investigated via a series of computations using both conical and three-dimensional Reynolds-averaged Navier-Stokes equations with turbulence incorporated through the algebraic turbulent eddy viscosity model of Baldwin-Lomax. Results are compared with known experimental data, and it is concluded that the computed three-dimensional flowfield is quasi-conical (in agreement with the experimental data), the computed three-dimensional and conical surface pressure and surface flow direction are in good agreement with the experiment, and the three-dimensional and conical flows significantly underpredict the peak experimental skin friction. It is pointed out that most of the features of the conical flowfield model in the experiment are observed in the conical computation which also describes the complete conical streamline pattern not included in the model of the experiment.

Knight, Doyle D.↗
NASA NTRS1988

Reduction of crossflow shock-induced separation with a porous cavity at supersonic speeds

The effectiveness of wing surface porosity in reducing boundary-layer separation induced by a cross flow shock on a conical wing in a supersonic flow was investigated in tests conducted in the NASA Langley Research Center Unitary Plan Wind Tunnel, at a Reynolds number of 2 mln/ft at Mach numbers 1.62, 1.70, 1.86, and 2.00 and with the angle of attack varying between -2 and 10 deg. A porous cavity was installed in a 57 deg swept conical wing at a location where a cross flow shock had been observed in previous tests. The porosity was varied from 11 to 22 percent, the pore hole diameter was varied from 0.025 to 0.050 in., and the cavity depth varied from 0.067 to 0.255 in. It was found that a hole of 0.025 in. in diameter is more effective than a 0.050-in. hole. However, the effectiveness of the larger holes could be increased by reducing the cavity depth, causing a closed-cavity type flow condition.

Bauer, Steven X. S.↗