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Results for “Compressibility effect”

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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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Analytical characterization of AOTV perigee aerothermodynamic regime

In preliminary design studies of AOTV (Aeroassisted Orbital Transfer Vehicle) configurations, it is desirable to have a simple analytical method for characterizing the aerothermodynamic regime at skip trajectory perigee as a function of vehicle L/D and m/CDA (ballistic coefficient). The present study derives an approximate perigee solution from the generalized equations of motion. For a prescribed entry velocity vector, the solution determines a Zeta function (proportional to density divided by m/CDA) at perigee as a parametric function of the exit velocity vector and (constant) L/D. The perigee Zeta function then determines perigee density (or altitude) as a parametric function of m/CDA. The solution allows the following classic aerothermodynamic parameters to be determined at perigee as parametric functions of m/CDA, L/D, and the exit velocity vector: Reynolds Number (viscous effects), Mach Number (compressibility effects), Knudsen Number (rarefaction effects), sphere and disk bow shock standoff distance, Damkohler Number (relaxation effects), viscous correlation parameter (viscid-inviscid interactions), and Stanton Number (convective heat transfer). Results of the analysis are given for low L/D and mid L/D AOTV configurations on return from geosynchronous and L5 orbits. It is concluded the method successfully provides preliminary estimates of the aerothermodynamic parameters through the use of simple algebraic equations and plots.

Desautel, D.↗
NASA NTRS1990

On the dip angle of subducting plates

A new approximate analytic model is developed for the thermal structure of a subducting plate with a finite length. This model provides the capability of easily examining the thermal and mechanical structure of a subducting plate with different lengths and at different angles. Also, the torque balance of a descending plate can be examined, and effects such as the leading edge effect, the adiabatic compression effect, and the phase change effect can be incorporated. A comparison with observed data indicates that short slabs are likely under torque equilibrium at present, while long slabs are probably dominated by their gravitational torques such that their dip angles are transient, moving toward a steeper dip angle similar to that of the Mariana slab.

Hsui, Albert T.↗
NASA NTRS1991

Progress of simulations for reacting shear layers

An attempt was made to develop a high speed, chemically reactive shear layer test rig. The purpose of the experiment was to study the mixing of oxidizer and fuel streams in reacting shear layers for various density, velocity, and Mach number. The primary goal was to understand the effects of the compressibility upon mixing and combustion in a fundamental way. Therefore, a two-dimensional shear layer is highly desirable for its simplicity to quantify the compressibility effects. The RPLUS 2D code is used to calculate the flow fields of different sections of the test rig. The emphasis was on the supersonic nozzle design, the vitiation process for the hot air stream and the overall thermodynamic conditions of the test matrix. The k-epsilon turbulence model with wall function was successfully implemented in the RPLUS code. The k and epsilon equations are solved simultaneously and the LU scheme is used to make it compatible with the flow solver.

Yu, Sheng-Tao↗
NASA NTRS1998

Compressibility and Turbulence Effects Due to Airfoil Clocking in Axial Compressors

Axial compressors have inherently unsteady flow fields because of relative motion between rotor and stator airfoils. This relative motion leads to viscous and inviscid (potential) interactions between blade rows. As the number of stages increases in a turbomachine, the buildup of convected wakes can lead to progressively more complex wake/wake and wake/airfoil interactions. Variations in the relative circumferential positions of stators or rotors can change these interactions, leading to different unsteady forcing functions on airfoils and different compressor efficiencies. In addition, as the Mach number increases the interaction between blade rows is intensified due to potential effects. The current study uses an unsteady, two-dimensional Navier-Stokes approach to investigate the unsteady aerodynamics of stator clocking in a 1-1/2 stage compressor, typical of high-pressure compressors used in advanced commercial jet engines. The effects of turbulence are modeled with both algebraic and two-equation models. Results include surface pressures, efficiencies, boundary layer quantities and turbulence quantities. In addition, the growth of turbulence and the effects of compressibility on airfoil are discussed.

Dorney, Daniel J.↗
NASA NTRS1951

Blockage Corrections for Three-Dimensional-Flow Closed-Throat Wind Tunnels, with Consideration of the Effect of Compressibility

Theoretical blockage corrections are presented for a body of revolution and for a three-dimensional, unswept wing in a circular or rectangular wind tunnel. The theory takes account of the effects of the wake and of the compressibility of the fluid, and is based on the assumption that the dimensions of the model are small in comparison with those of the tunnel throat. Formulas are given for correcting a number of the quantities, such as dynamic pressure and Mach number, measured in wind tunnel tests. The report presents a summary and unification of the existing literature on the subject

Herriot, J. G.↗
NASA NTRS1950

Blockage corrections for three-dimensional-flow closed-throat wind tunnels, with consideration of the effect of compressibility

Theoretical blockage corrections are presented for a body of revolution and for a three-dimensional unswept wing in a circular or rectangular wind tunnel. The theory takes account of the effects of the wake and of the compressibility of the fluid, and is based on the assumption that the dimensions of the model are small in comparison with those of the tunnel throat. Formulas are given for correcting a number of the quantities, such as dynamic pressure and Mach number, measured in wing-tunnel tests. The report presents a summary and unification of the existing literature on the subject.

Herriot, John G↗
NASA NTRS1947

Blockage corrections for three-dimensional-flow closed-throat wind tunnels, with consideration of the effect of compressibility

Theoretical blockage corrections are presented for a body of revolution and for a three-dimensional unswept wing in a circular or rectangular wind tunnel. The theory takes account of the effects of the wake and of the compressibility of the fluid, and is based on the assumption that the dimensions of the model are small in comparison with those of the tunnel throat. Formulas are given for correcting a number of the quantities, such as dynamic pressure and Mach number, measured in wind-tunnel tests. The report presents a summary and unification of the existing literature on the subject.

Herriot, John G↗
NASA NTRS1945

The Effect of Compression Ratio on Knock Limits of High-Performance Fuels in a CFR Engine II : Blends of 2,2,3-Trimethylpentane with 28-R

The knock-limited performance of blends of 0,50; and 100 percent by volume of 2,2,3-trimethylpentane in 28-R fuel determined with a modified F-4 engine at three sets of conditions varying from severe to mild at each of three compression ratios (6.0, 8.0, and 10.0). A comparison of the knock-limited performance of 2,2,3-trimethylpentane with that of triptane (2,2,3-trimethylbutane) is included. The knock-Limited performance of 2,2,3-trimethylpontane was usually more sensitive to either compression ratio or inlet-air temperature than 28-R fuel, but the ratio of the knock-limited indicated mean effective pressure of a given blend containing 2,2,3-trimethypentane and 28-R to the indicated mean effective pressure of 28-R alone was not greatly affected by compression ratio if the engine operating conditions were mild. Although 2,2,3-trimethylpentane in general had a lower knock-limited performance than triptane, the characteristics of the two fuels were somewhat similar.

FUELS, ANTIKNOCK↗
NASA NTRS1944

Wall interference in a two-dimensional-flow wind tunnel, with consideration of the effect of compressibility

Theoretical tunnel-wall corrections are derived for an airfoil of finite thickness and camber in a two-dimensional-flow wind tunnel. The theory takes account of the effects of the wake of the airfoil and of the compressibility of the fluid, and is based upon the assumption that the chord of the airfoil is small in comparison with the height of the tunnel. Consideration is given to the phenomenon of choking at high speeds and its relation to the tunnel-wall corrections. The theoretical results are compared with the small amount of low-speed experimental data available and the agreement is seen to be satisfactory, even for relatively large values of the chord-height ratio.

Allen, H Julian↗
NASA NTRS1991

Effect of heat release on the stability of compressible reacting mixing layer

Reacting free shear layers are of fundamental importance in many industrial systems including gas turbine combustors and rockets. Efficient propulsion systems are essential for air breathing supersonic ramjets in the high Mach number range. A limiting factor in these engines is the time for fuel and oxidizer to mix in the combustion chamber; for fast mixing, the flow must be vigorously turbulent which requires the laminar flow to be unstable. Understanding the stability characteristics of compressible reacting free shear layers is, therefore, very important and may allow one to control the flow. Low speed shear layers are highly unstable but, as chemical reaction and compressibility effects tend to stabilize them, it is important to investigate the stability of high speed reacting mixing layers. The latter consists of two fluid streams containing fuel and oxidizer respectively, and the conclusions are expected to apply, with quantitative modifications, to other shear flows, e.g., jets. Since low speed reacting cases have been studied earlier, we concentrate on the effects of Mach number and heat release. We are primarily interested in solving the stability problem over a large range of Mach number and heat release. In order to understand the effect of the heat release on the stability of this flow, one must first study the characteristics of the non-reacting flow. Inviscid theory is a reliable guide for understanding stability of compressible shear flows at moderate and large Reynolds numbers and is the basis for this work.

Shin, Dong-Shin↗
NASA NTRS1945

Effects of Compressibility on the Maximum Lift Characteristics and Spanwise Load Distribution of a 12-Foot-Span Fighter-Type Wing of NACA 230-Series Airfoil Sections

Lift characteristics and pressure distribution for a NACA 230 wing were investigated for an angle of attack range of from -10 to +24 degrees and Mach range of from 0.2 to 0.7. Maximum lift coefficient increased up to a Mach number of 0.3, decreased rapidly to a Mach number of 0.55, and then decreased moderately. At high speeds, maximum lift coefficient was reached at from 10 to 12 degrees beyond the stalling angle. In high-speed stalls, resultant load underwent a moderate shift outward.

PRESSURE DISTRIBUTION - AIRFOILS-NACA 23016↗
NASA NTRS1944

Effect of Compressibility on Pressure Distribution over an Airfoil with a Slotted Frise Aileron

Pressure distribution measurements were made over an airfoil with slotted Frise aileron up to 0.76 Mach at various angles of attack and aileron defections. Section characteristics were determined from these pressure data. Results indicated loss of aileron rolling power for deflections ranging from -12 Degrees to -19 Degrees. High stick forces for non-differential deflections incurred at high speed, which were due to overbalancing tendency of up-moving aileron, may precipitate serious control difficulties. Detailed results are presented graphically.

WINGS-REPUBLIC P-47B-3 WIND TUNNEL TESTS(NACA-HIGH↗
NASA NTRS1991

Modeling of compressible turbulent shear flows

Despite all the recent developments in computer technologies and numerical algorithms, full numerical simulations of turbulent flows are feasible only at moderate Reynolds numbers and for flows with relatively simple geometries. The main goal of this research is to develop new second order moment closures for compressible turbulence. It has been shown that the models based on the extension of those developed originally for incompressible flows fail to adequately predict turbulent flows at high Mach numbers. In this attempt, the compressibility effects are explicitly considered. A successful development of these models that directly takes into account the compressibility effects may have a range of technological implications in the design of supersonic and hypersonic vehicles.

Liou, William W.↗