Stanton number for separated turbulent flow past relatively deep cavities
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Miles, J. B.↗
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An elliptic representation of coupled boundary layers and inviscid core for computation of separated internal flows
This report presents a viscous-inviscid calculation method for the prediction of turbulent incompressible flows in diffusers with small regions of stall. Integral turbulent boundary layer equations (BLE) are used to provide boundary conditions for a finite difference representation of the inviscid core. The BLE are applied at the floating displacement-thickness line, resulting in a simulataneous set of nonlinear block tridiagonal equations which are solved iteratively using a sucessive line-relaxation technique. Results of the method have been applied to calculate the performance of a variety of asymmetric stalled diffusers.
Ghose, S.↗
Highly separated transonic flows
Attention is given to the wind tunnel, to photographic visualization of the flow, and to measurements by pressure probes, hot wire anemometry and laser anemometry. The simultaneous use of different means of measurement provided a good description of the phenomenon, and indicated the existence of shocks and their stability, as well as the existence of the bubble, its dimensions, and in particular, the reattachment of its front. The results show that the bursting (or transition) of the bubble front is produced at an unstable position and creates a point of turbulent intensity which diffuses over the entire height of the flow.
Farcy, A.↗
Laser holographic interferometry for an unsteady airfoil in dynamic stall
Laser holographic interferometry was used to study a two-dimensional NACA 0012 airfoil undergoing dynamic stall. The airfoil, fabricated from graphite fiber and epoxy, was tested at Mach numbers of 0.3 to 0.6, at Reynolds numbers of 500,000-2,000,000, at reduced frequencies of 0.015 to 0.15, and at mean angles of attack of 0-10 deg with amplitudes of 10 deg. Density and pressure fields were obtained from dual-plate interferograms. Double-pulse interferograms, which seemed to show the wake boundaries better, were also taken. Comparisons of pressures with orifice pressures were good for the attached flow cases. For the separated flow cases, which had a vortex enbedded in the flow, the comparisons were poor. Vortices, wake structures, and the dynamic stall process can be seen by holographic interferometry.
Lee, G.↗
Evaporation and combustion of sprays
A description is provided of recent spray evaporation and combustion models, taking into account turbulent two- and three-dimensional spray processes found in furnaces, gas turbine combustors, and internal combustion engines. Within the class of spray models of interest, two major categories are distinguished, including locally homogeneous flow (LHF) models and separated flow (SF) models. SF models are of the greatest practical importance, but LHF models have distinct advantages in some cases. Attention is also given to recent progress on modeling interactions between drops and the flow in both dilute and dense sprays, involving sprays having low and high liquid volume fractions, respectively.
Faeth, G. M.↗
Flow in a differentially rotated cylindrical drop at moderate Reynolds number
Galerkin finite-element approximations are combined with computer-implemented perturbation methods for tracking families of solutions to calculate the steady axisymmetric flows in a differentially rotated cylindrical drop as a function of Reynolds number Re, drop aspect ratio and the rotation ratio between the two end disks. The flows for Reynolds numbers below 100 are primarily viscous and reasonably described by an asymptotic analysis. When the disks are exactly counter-rotated, multiple steady flows are calculated that bifurcate to higher values of Re from the expected solution with two identical secondary cells stacked symmetrically about the axial midplane. The new flows have two cells of different size and are stable beyond the critical value Re sub c. The slope of the locus of Re sub c for drops with aspect ratio up to 3 disagrees with the result for two disks of infinite radius computed assuming the similarity form of the velocity field. Changing the rotation ratio for exact counter-rotation ruptures the junction of the multiple flow fields into two separated flow families.
Harriott, G. M.↗
In-flight total forces, moments and static aeroelastic characteristics of an oblique-wing research airplane
A low-speed flight investigation has provided total force and moment coefficients and aeroelastic effects for the AD-1 oblique-wing research airplane. The results were interpreted and compared with predictions that were based on wind tunnel data. An assessment has been made of the aeroelastic wing bending design criteria. Lateral-directional trim requirements caused by asymmetry were determined. At angles of attack near stall, flow visualization indicated viscous flow separation and spanwise vortex flow. These effects were also apparent in the force and moment data.
Curry, R. E.↗
Water facilities in retrospect and prospect: An illuminating tool for vehicle design
Water facilities play a fundamental role in the design of air, ground, and marine vehicles by providing a qualitative, and sometimes quantitative, description of complex flow phenomena. Water tunnels, channels, and tow tanks used as flow-diagnostic tools have experienced a renaissance in recent years in response to the increased complexity of designs suitable for advanced technology vehicles. These vehicles are frequently characterized by large regions of steady and unsteady three-dimensional flow separation and ensuing vortical flows. The visualization and interpretation of the complicated fluid motions about isolated vehicle components and complete configurations in a time and cost effective manner in hydrodynamic test facilities is a key element in the development of flow control concepts, and, hence, improved vehicle designs. A historical perspective of the role of water facilities in the vehicle design process is presented. The application of water facilities to specific aerodynamic and hydrodynamic flow problems is discussed, and the strengths and limitations of these important experimental tools are emphasized.
Erickson, G. E.↗
Viscous analyses for flow through subsonic and supersonic intakes
A parabolized Navier-Stokes code was used to analyze a number of diffusers typical of a modern inlet design. The effect of curvature of the diffuser centerline and transitioning cross sections was evaluated to determine the primary cause of the flow distortion in the duct. Results are presented for S-shaped intakes with circular and transitioning cross sections. Special emphasis is placed on verification of the analysis to accurately predict distorted flow fields resulting from pressure-driven secondary flows. The effect of vortex generators on reducing the distortion of intakes is presented. Comparisons of the experimental and analytical total pressure contours at the exit of the intake exhibit good agreement. In the case of supersonic inlets, computations of the inlet flow field reveal that large secondary flow regions may be generated just inside of the intake. These strong flows may lead to separated flow regions and cause pronounced distortions upstream of the compressor.
Povinelli, Louis A.↗
Viscous analyses for flow through subsonic and supersonic intakes
A parabolized Navier-Stokes code was used to analyze a number of diffusers typical of a modern inlet design. The effect of curvature of the diffuser centerline and transitioning cross sections was evaluated to determine the primary cause of the flow distortion in the duct. Results are presented for S-shaped intakes with circular and transitioning cross sections. Special emphasis is placed on verification of the analysis to accurately predict distorted flow fields resulting from pressure-driven secondary flows. The effect of vortex generators on reducing the distortion of intakes is presented. Comparisons of the experimental and analytical total pressure contours at the exit of the intake exhibit good agreement. In the case of supersonic inlets, computations of the inlet flow field reveal that large secondary flow regions may be generated just inside of the intake. These strong flows may lead to separated flow regions and cause pronounced distortions upstream of the compressor.
Povinelli, Louis A.↗
Experimental aerodynamic evaluation of the SSME two-duct, hot gas manifold
An investigation was performed on an improved Space Shuttle Main Engine (SSME) hot gas manifold (HGM) design using a full scale HGM model in cold-flow, air-blowdown tests. The new HGM design replaces the current three transfer ducts with two enlarged elliptical transfer ducts, faired duct inlets, and enlarged fuel bowl. Extensive experimental results have been obtained to verify previous results showing that the two-duct design improved the HGM internal flow path by eliminating separated flow regions, reducing high local velocities, and providing more uniform flow.
Kim, B. Y.↗
Upwind Navier-Stokes solutions for separated periodic flows
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Rumsey, Christopher L.↗
Transition from laminar to turbulent flow in separated shear layers
The location of boundary layer separation may be predicted by either semiempirical criteria or by various computer codes written for such calculations; attention is presently given to the streamwide length from separation to transition, denoted by Re(sL). It is demonstrated that the unit Reynolds number, a feature of the transition phenomenon implicit in the data of Schmidt et al. (1985) and overlooked in previous investigations, must be considered in future work.
Potter, J. Leith↗
Water facilities in retrospect and prospect: An illuminating tool for vehicle design
Water facilities play a fundamental role in the design of air, ground, and marine vehicles by providing a qualitative, and sometimes quantitative, description of complex flow phenomena. Water tunnels, channels, and tow tanks used as flow-diagnostic tools have experienced a renaissance in recent years in response to the increased complexity of designs suitable for advanced technology vehicles. These vehicles are frequently characterized by large regions of steady and unsteady 3-D flow separation and ensuing vortical flows. The visualization and interpretation of the complicated fluid motions about isolated vehicle components and complete configurations in a time and cost effective manner in hydrodynamic test facilities is a key element in the development of flow control concepts, and, hence, improved vehicle designs. A historical perspective of the role of water facilities in the vehicle design process is presented. The application of water facilities to specific aerodynamic and hydrodynamic flow problems is discussed, and the strengths and limitations of these important experimental tools are emphasized.
Erickson, Gary E.↗
Separation-bubble flow solution using Euler/Navier-Stokes zonal approach with downstream compatibility conditions
The two-dimensional flow over a blunt leading-edge plate is simulated on the basis of an Euler/Navier-Stokes zonal scheme. The scheme uses an implicit upwind finite-volume scheme, which is based on the van Leer flux-vector splitting. It is shown that the Euler/Navier-Stokes zonal scheme with downstream boundary-layer compatibility conditions is accurate and efficient.
Liu, C. H.↗
Navier-Stokes computations of separated vortical flows past prolate spheroid at incidence
The problem of steady incompressible viscous flow past prolate spheroids at incidence is formulated using the unsteady incompressible and compressible thin-layer Navier-Stokes equations. The two sets of Navier-Stokes equations are solved using a pseudotime stepping of the implicit flux-difference splitting scheme on a curvilinear grid, which is generated by a transfinite grid generator. The Baldwin and Lomax (1978) algebraic eddy-viscosity model is used to model the turbulent flow. The computational applications cover a 6:1 prolate spheroid at different angles of attack and Reynolds numbers. The results are compared with experimental data.
Wong, Tin-Chee↗
Spectral measurements and other features of separating turbulent flows
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Simpson, Roger L.↗
Calculations of separated vortex flows at low speed for low-aspect-ratio wings
An implicit finite-difference scheme has been developed for solving three-dimensional incompressible Navier-Stokes equations. Computations for complicated vortical flows past several sharp- and round-edged delta and double-delta wings at high angles of attack and sideslip are discussed. Computed results demonstrate the effectiveness of the present method and show good agreement with experimental data.
Liu, C. H.↗