Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Cross-flow”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Jet decay rate effects on hover jet-induced loads

The paper explains the mechanisms for observed jet decay rate effects on jet-induced loads on a flat plate for cross-flow and hover configurations. Examples are presented for the influence of the decay rate on integrated loads on a flat plate induced by the jet issuing at a right angle from the plate into still air; knowledge of these jet-induced loadings is of particular importance for VTOL aircraft design because they produce an effective loss in the lift force available in hover. The apparent inconsistency between existing lift loss vs jet decay rate trends is explained in light of the different mechanism which determine the jet mixing and trajectory, i.e., entrainment, blockage, and the vortex pair associated with a jet in crossflow.

Kuhlman, J. M.↗
NASA NTRS1981

Three-dimensional turbulent boundary layer development and separation in V/STOL engine inlets at incidence with small-cross flow and curvature influences

The study concerns the influence of the three-dimensional cross flows on the compressible turbulent boundary layer development and flow separation prediction around V/STOL engine inlets at high incidence. The governing equations for the three-dimensional boundary layer flow with small-cross approximation are solved numerically on an intrinsic streamline coordinate system. Results are presented to illustrate the effects of small cross-flow, compressibility and streamline curvatures on the flow. Comparisons of the results with the wind tunnel data for scaled model and with data obtained from another existing compressible axisymmetric turbulent boundary layer scheme are included in the analysis.

Chou, D. C.↗
NASA NTRS1981

Computation of hypersonic viscous flow around three-dimensional bodies at high angles of attack

A parabolized Navier-Stokes code capable of predicting steady viscous supersonic flows with cross-flow separation is applied to three-dimensional arbitrary geometries at high angles of attack. The numerical procedure, which is implicit, noniterative, and of second-order accuracy in the marching direction, has been used to compute complicated flow fields containing a relatively thick sonic layer and regions of strong viscous-inviscid interaction. A consistent and accurate procedure has also been developed to provide the necessary starting data through timewise integration of the equations of motion near the nose-tip region of the body. Numerical results obtained from the present method compare well with experiment for both the surface pressures and heat transfer.

Rizk, Y. M.↗
NASA NTRS1981

Aerodynamic heating on the corrugated surface of a 10.2 deg half-angle blunted cone at Mach 6.7

A 10.2 deg half-angle blunted cone with corrugated surfaces was tested in the Langley 8-foot high-temperature structures tunnel to measure the aerodynamic heating of its surfaces. The tests were made in a turbulent boundary layer at angles of attack of 0 deg, 5 deg, and 10 deg. Heating of the windward side was in reasonable agreement with theoretical turbulent predictions for a smooth cone, while heating on the leeward side was between laminar and turbulent predictions as a result of local transitional flow or flow separation produced by high lee-side pressures. Localized heating measurements indicated a significant increase in heating at large cross-flow angles, with the maximum heating rates occurring where the flow reattaches on the upstream side of the corrugation crest and the minimum occurring on the downstream side where the flow is separated.

Weinstein, I.↗
NASA NTRS1982

Application of the laser Doppler velocimeter in aerodynamic flows

Applications of the laser doppler velocimeter (LDV) are discussed. Measurements were made of the flowfield around a tangent-ogive model in a low turbulent, incompressible flow at an incidence of 45 deg. The free-stream velocity was 80 ft per second. The flowfield velocities in several cross-flow planes were measured with a 2-D, two-color LDC operated in a backscatter mode. Measurements were concentrated in the secondary separation region. A typical survey is given. The survey was taken at a model location where the maximum side force occurs. The overall character of the leeward flowfield with the influence of the two body vorticles are shown. Measurements of the velocity and density flowfields in the shock-layer region of a reentry-vehicle indented nose configuration were carried out at Mach 5. The velocity flowfield was measured with a 2-color, 2-D, forward-scatter LDV system. Because of the need to minimize particle lag in the shock-layer region, polystyrene particles with a mean diameter of 0.312 microns were used for the scattering particles. The model diameter was 6 inches.

Yanta, W. J.↗
NASA NTRS1981

The three-dimensional boundary layer on a rotating helical blade

The laminar boundary layer on a twisted helical blade is considered. The blade geometry is the same as that proposed by Horlock and Wordsworth (1965). However, the blade is twisted about the leading edge in the manner described by Miyake and Fujita (1974). The flow may be considered to be the analog, in a rotating reference frame, of the flat-plate boundary layer in a stationary frame. It is shown that a coordinate system which is orthogonal in the blade surface may be developed. With the appropriate scaling of the dependent variables a solution for the boundary layer flow is readily obtained. The systems of ordinary differential equations for the stream function of the primary flow and the cross-flow are solved numerically.

Morris, P. J.↗
NASA NTRS1981

Multigrid simulation of asymptotic curved-duct flows using a semi-implicit numerical technique

Asymptotic flows inside curved ducts of rectangular as well as polar cross section are analyzed using the Navier-Stokes equations in terms of the axial velocity and vorticity and the cross-flow stream function. Numerical solutions of the three second-order coupled elliptic partial differential equations governing this flow are obtained efficiently using the coupled alternating-direction implicit (ADI) method as well as the multigrid strongly-implicit (SI) scheme. For the flow configuration studied, the ADI method is found to be more sensitive to the time steps used than is the SI scheme. Use of the multigrid-coupled-strongly-implicit (MG-SI) scheme makes it possible to efficiently obtain fine-grid solutions for configurations having strong secondary flow. It is shown that, for this asymptotic curved-duct flow, the similarity parameter of significance is the Dean's number K rather than the Reynolds number Re. Results are obtained for curved ducts with square cross sections for K up to 900, which here corresponds to Re = 9,000 for this internal flow configuration.

Ghia, K. N.↗
NASA NTRS1982

Implicit marching solution of compressible viscous subsonic flow in planar and axisymmetric ducts

A new streamwise marching procedure was developed and coded for compressible viscous subsonic flow in planar or axisymmetric ducts with or without centerbodies. The continuity, streamwise momentum, cross-flow momentum, and energy equations are written in generalized orthogonal curvilinear coordinates. To allow the use of a marching procedure, second derivatives in the streamwise momentum equation are written as the sum of a known two dimensional imposed pressure field and an unknown one dimensional viscous correction. For turbulent flow, the Reynolds stress and heat flux terms are modeled using two-layer eddy viscosity turbulence models.

Towne, C. E.↗
NASA NTRS1981

Application of a laser interferometer skin-friction meter in complex flows

The application of a nonintrusive laser-interferometer skin-friction meter, which measures skin friction with a remotely located laser interferometer that monitors the thickness change of a thin oil film, is extended both experimentally and theoretically to several complex wind-tunnel flows. These include two-dimensional seperated and reattached subsonic flows with large pressure and shear gradients, and two and three-dimensional supersonic flows at high Reynolds number, which include variable wall temperatures and cross-flows. In addition, it is found that the instrument can provide an accurate location of the mean reattachment length for separated flows. Results show that levels up to 120 N/sq m, or 40 times higher than previous tests, can be obtained, despite encountering some limits to the method for very high skin-friction levels. It is concluded that these results establish the utility of this instrument for measuring skin friction in a wide variety of flows of interest in aerodynamic testing.

Monson, D. J.↗
NASA NTRS1982

A basic code for the prediction of transient three-dimensional turbulent flowfields

A primitive pressure-velocity finite difference code has been developed to predict transient three-dimensional turbulent flow. The code is a simplified yet effective prediction procedure for use by persons with little experience in computational fluid dynamics, and into which user-oriented complexities can easily be added. The method is based on the transient two-dimensional Los Alamos SOLA prediction technique for laminar flows. Turbulence is simulated by means of a two-equation turbulence model; species diffusion and buoyancy are also included. Two applications of the code are presented to local destratification near the release structure of a reservoir and to the deflection of a jet entering normally into a uniform cross-flow. Predicted results exhibit good agreement with experimental data, showing that a useful characterization of fully three-dimensional flows is now available.

Busnaina, A. A.↗
NASA NTRS1983

Study of asymptotic incompressible flow in curved ducts using a multi-grid technique

Asymptotic flows inside curved ducts of rectangular as well as polar cross sections have been analyzed using the Navier-Stokes equations in terms of the axial velocity and vorticity and the cross-flow stream function. Numerical solutions of the three second-order coupled elliptic partial differential equations governing this flow have been obtained using the multi-grid-SI scheme, to determine fine-grid results for configurations with strong secondary flow.

Ghia, K. N.↗
NASA NTRS1982

Wake interference for a heated oscillating cylinder

Penney and Jefferson (1966) have studied heat transfer from an oscillating, horizontal wire. The present investigation has the objective to determine the governing parameters which indicate when interaction between an oscillating circular cylinder and its wake will reduce the apparent heat transfer coefficient in quasi-steady conditions, taking into account, if possible, also the determination of the approximate magnitude of the reduction. A definition is provided of a nondimensional vertical mass flux, representing the induced flow due to heating of the stagnant fluid. It is hypothesized that the flux is related to a natural convection parameter which describes the heating of the wake. For oscillation of a circular cylinder in air under the conditions studied, it is found that the application of a cross-flow correlation in a quasi-steady, transient analysis predicts heat transfer parameters in close agreement with experiment over a certain range, provided interaction with the heated wake is avoided.

Mceligot, D. M.↗
NASA NTRS1954

Aerodynamics of Slender Bodies at Mach Number of 3.12 and Reynolds Numbers from 2 x 10(exp 6) to 15 x 10(exp 6) V : Aerodynamic Load Distributions for a Series of Four Boattailed Bodies

Pressure distributions for a series of four boattailed bodies of revolution were obtained and compared with theory for a Mach number of 3.12, a Reynolds number range of 2 x 10 to 6th power to 14 x 10 to the 6th power, and angles of attack from zero to 9 degrees. Second-order theory adequately predicted the pressure distribution for regions free of the effects of cross-flow separation.

Moskowitz, Barry↗
NASA NTRS1944

Intercooler cooling-air weight flow and pressure drop for minimum drag loss

An analysis has been made of the drag losses in airplane flight of cross-flow plate and tubular intercoolers to determine the cooling-air weight flow and pressure drop that give a minimum drag loss for any given cooling effectiveness and, thus, a maximum power-plant net gain due to charge-air cooling. The drag losses considered in this analysis are those due to (1) the extra drag imposed on the airplane by the weight of the intercooler, its duct, and its supports and (2) the drag sustained by the cooling air in flowing through the intercooler and its duct. The investigation covers a range of conditions of altitude, airspeed, lift-drag ratio, supercharger-pressure ratio, and supercharger adiabatic efficiency. The optimum values of cooling air pressure drop and weight flow ratio are tabulated. Curves are presented to illustrate the results of the analysis.

Reuter, J George↗
NASA NTRS1995

Computation of three-dimensional mixed convective boundary layer flow

The paper presents the numerical solution of heat and mass transfer during cross-flow (orthogonal) mixed convection. In this class of flow, a buoyancy-driven transport in the vertical direction and a forced convective flow in the horizontal direction results in a three-dimensional boundary layer structure adjacent to the plate. The rates of heat and mass transfer are determined by a combined influence of the two transport processes. The equations for the conservation of mass, momentum, energy, and species concentration were solved along with appropriate boundary conditions to determine the distributions of velocity components, temperature, and concentration across the thickness of the boundary layer at different locations on the plate. Results were expressed in dimensionless form using Reynolds number, Richardson number for heat transfer, Richardson number for mass transfer, Prandtl number, and Schmidt number as parameters. It was found that the transport is dominated by buoyancy at smaller vertical locations and at larger distances away from the forced convection leading edge. Effects of forced convection appeared to be very strong at smaller horizontal distances from the leading edge. The cross stream forced convection enhanced the rate of heat and mass transfer by a very significant amount.

Gadepalli, Prashandt↗
NASA NTRS1939

Intercooler Design for Aircraft, Special Report

When an airplane is operating at high altitude, it is necessary to use a supercharger to maintain ground pressure at the carburetor inlet. This maintenance and high intake-manifold pressure tends to keep the power output of the engine at ground-level value. The air, being compressed by the supercharger, however, is heated by adiabatic compression and friction to a temperature that seriously affect the performance of the engine. It is thus necessary to use an intercooler to reduce the temperature of the air between the supercharger outlet and the carburetor inlet. The amount of cooling required of the intercooler depend on the efficiency of the supercharger installation. In this investigation, several types of intercoolers were compared and a design procedure that will give the best intercooler for a given set of conditions is indicated. The figure of merit used for the selection of the best design was the total power consumed by the intercooler. This value includes the power required to transport the weight of the intercooler as well as the power used to force the charge air and the cooling air through the intercooler. The cost, size and practicality of construction were not considered, inasmuch as it was thought that a survey of possibilities of improvement in design would be of interest, regardless of whether the improvement could be immediately realized. Three types of intercoolers are included in this survey: a counterflow intercooler with indirect cooling surface in the form of fins, a counterflow intercooler with direct cooling surfaces, and a cross-flow, tube-type intercooler.

Brevoort, M. J.↗
NASA NTRS1942

An Experimental Investigation of Flow Across Tube Banks

Flow across tube banks was investigated by surveys of total dynamic and static pressure by visualization of the flow through the use of titanium tetrachloride smoke, by thermocouple surveys of heated tubes, and by hot-wire surveys of both heated and unheated tubes. It was found that turbulence increased as the depth of the bank increased and that the broad wake behind each tube affected flow over the succeeding tubes.

AIR FLOW, TURBULENT-MEASUREMENT, HOT-WIRE↗