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The University of Wyoming King Air aircraft was the primary instrument platform for turbulence measurements in the bottom half of the convective boundary layer during 15 July-13 August 1996. A total of 12 successful research flights were made, each of about 4.5-h duration. Crosswind (east-west) flight patterns were flown in Oklahoma and Kansas over three sites of different land use: forest, pasture, and crops. Measurements of mean values, turbulent deviations, and turbulent fluxes of temperature, moisture, and momentum were made to test theories of convective transport, the radix layer, and cumulus potential. Additional portions of each flight included slant soundings and near-surface horizontal flights in order to determine mixed layer (ML) scaling variables such as ML depth [z.sub.i], Deardorff velocity [w.sub.*], and buoyancy velocity [w.sub.B]. While the ML was shallower and the ground wetter than anticipated based on climatology, a high-quality dataset was obtained.

Five local K-closure formulations and a TKE closure were incorporated in a one-dimensional version of the Pielke's model, and a comparative evaluation of the closure schemes was made for strong and weak wind stable boundary layer (SBL). The Cabauw (Netherlands) and EPRI-Kincaid site (United States) observations were used for this purpose. The results indicate that for the strong wind case study, the profiles of turbulent diffusivities in terms of shape, depth of significant mixing, and the height above the surface where diffusion reaches a maximum are more or less the same for the various closure schemes. Only the magnitudes of mixing produced by various closure schemes are different. This difference produced by various closure formulations causes minor but noticeable changes in the mean wind field and thermodynamic structure of the model SBL. However, although the profiles of turbulent diffusivities become weak, variable, and poorly defined under weak wind conditions, the mean profiles become insensitive to the differences in the diffusion that arise due to various parameterization schemes. Apart from the TKE closure scheme, Estournel and Guedalia simple local closure scheme is able to produce the essential features of the SBL quite well.

A computational fluid-acoustic procedure is presented and applied for simulating induced and acoustic receptivity in unsteady boundary-layer flows. The process solves a finite compressibility form of the Navier-Stokes equations by applying a flux differenced, finite volume method. The numerical experiments include the simulation of acoustic receptivity due to surface inhomogeneity in which the acoustic phenomena are modeled utilizing physically appropriate wavelengths.

Experimental results are presented which describe the effects of bulk flow pulsations on film cooled boundary layer structure. The film is produced by a single row of simple angle film cooling holes and the pulsations are in the form of sinusoidal variations of static pressure and streamwise velocity. Such pulsations are important in turbine studies because: (i) static pressure pulsations result in significant periodic variations of film cooling flow rates, coverage, and trajectories, and (ii) static pressure pulsations occur near blade surfaces in operating engines from passing shock waves and potential flow interactions between moving blade rows. Distributions of ensemble-averaged and time-averaged Reynolds stress tensor components are presented for x/d of 4.5, 9.8, 16.4, and 24.1 along with distributions of streamwise mean velocity and streamwise mean vorticity, where x is streamwise distance from the downstream edge of the holes and d is hole diameter. Important changes from the imposed bulk flow pulsations are evident in all measured quantities, especially just downstream of the holes at x/d = 4.5. Here, maximum Reynolds shear stresses [Mathematical Expression Omitted] are reduced by the pulsations in regions containing the largest film concentrations. This is because the shear layer produced by the injectant oscillates its position as each pulsation is imposed. This causes the shear layer to become more diffused as it is spread over a larger spatial volume.

Cross-spectral and cross-correlation data from experiments and numerical simulations have shown the turbulent wall pressure convection velocity to vary with the streamwise sensor spatial separation. This variation is due to the spatial decay rates of turbulent structures in the inner and outer regions of the boundary layer. Its effect is shown to have a significant impact on the distribution of energy in the wavenumber-frequency spectrum [Phi]([k.sub.1], [Omega]). The standard Corcos model is known to overpredict the wavenumber-frequency spectrum at low wavenumbers. This is shown to result from its constant convection velocity assumption. The spectral levels at subconvective and lower wavenumbers are shown to be directly influenced by the spatial variation in convection velocity. Convection velocity measurements from past investigations that cover the range 285 [less than or equal to] [R.sub.[Theta]] [less than or equal to] 29,000 are compared, and an outer variable scaling is shown to effectively collapse the data.

A finite-difference scheme has been developed to solve the boundary-layer equations governing laminar flows around and inside a spherical fluid droplet moving steadily in another immiscible fluid. Using this scheme, results not available in the literature have been obtained for circulating droplets at intermediate and high interior-to-exterior viscosity ratios ([[Mu].sup.*]) and large values of the external flow Reynolds number (Re). Detailed results over the range 1.01 [less than or equal to] [[Mu].sup.*] [less than or equal to] (solid sphere) and 100 [less than or equal to] Re [less than or equal to] 10000 are presented for the velocity profiles outside and inside the droplet, the interface shear stress, the external flow separation angle, the droplet surface velocity and the drag coefficient.

Simple, analytical approximations to the solution of the one-dimensional Boussinesq equation are obtained using a weighted residual method. The approach can be applied to both the recharging and the dewatering of an unconfined, homogeneous aquifer from a fully penetrating trench. Estimates for recharge, discharge, and the elevation of the water table are given by explicit algebraic expressions. Comparison with numerical solutions illustrates the accuracy of these new formulas.

It is generally accepted that even relatively small longitudinal surface or streamline curvature has a significant effect on transport of momentum and heat in turbulent boundary layers. A review is made of experiments that elucidate the effects of curvature and turbulence models which attempt to account for these effects. While the main body of the review is concerned with two-dimensional boundary-layer flow, as is much of the available literature, attention is drawn to the much broader role of curvature in three-dimensional flows.

A gradient descent algorithm facilitates the automatic adjustment of the suction flow rates in a laminar flow control system, and computes the optimal suction distribution. The model reduces the suction power required to maintain laminar-turbulent transition at a particular point. Thus, the model reduces drag and increases energy efficiency of an aircraft. Optimization of the transition position has been achieved by considering the problem as being one-dimensional instead of being multidimensional.

Large eddy simulation of a marine boundary layer (BL) with strong wind shear and weak buoyancy flux, over a relatively large horizontal domain (25 x 18 km) and long time period (16 h), produces lineal eddy structures with along-axis variations. These 'rolls' are transient, their lifetime being roughly 8 h and their horizontal-to-vertical aspect ratio increases with time. At all heights above the surface layer, even above the BL, temporally coherent features propagate with a speed slightly slower than the vertically averaged BL velocity. The length scale of along-roll variation is about four and one-half times the corresponding cross-roll length scale. To examine the importance of the roll circulations, fluxes of momentum, heat, and water vapor are partitioned into roll and non-roll contributions, and additionally separated into contributions from the ascending and descending roll regions, to reveal differences in advective roll transport and in roll modulation of smaller-scale transfer. The roll influence is largest at mid-BL for momentum and moisture fluxes but largest near the BL top for heat flux. The implied K-theory mixing coefficients are quite different for each variable, even if the influence of the roll circulations is removed. Horizontal variations of surface flux are opposite in sign to flux variations within the BL bulk.

Experimental evidence and computational evidence suggest that the distribution of random segment lengths defined by the intersections of ray paths with the contorted and folded interface between two fluids mixed by turbulence follows a probability distribution with a Levy law tail. Assuming that the two fluids have different optical properties, one finds that the statistics of light scattered by the mixing interface reflect the probability distribution for the random distances between the intersection points of straight ray paths with the interface. Examples of light-scattering calculations for limiting cases, including the planetary albedo problem and imaging through a transparent mixing layer, are discussed.

The flowfield inside a bleed slot utilized to regulate an oblique shock-wave and turbulent boundary-layer interaction was examined. The slot was placed normal to the primary flow direction. Two operating situations were investigated: M = 1.98 with a shock generator deflection angle of 6 degrees and M = 2.46 with a shock deflection angle of 8 degrees. Findings revealed that despite a two-dimensional interaction for the zero-bleed-flow case, the slot does not eliminate mass uniformly in the spanwise direction.

We developed a procedure for using data for attenuation [Sigma] of the marine atmosphere at [Lambda] = 0.55 [[micro]meter] and Angstrom parameter [Alpha] in the visible range for the estimation of aerosol particle size spectrum. We evaluated the aerosol microstructure in the marine atmospheric boundary layer (MABL). To eliminate the effect of the upper troposphere and stratosphere, we assumed that the optical characteristics of the microstructure are average for the typical marine atmosphere. The sought-for MABL microstructure is parameterized by the sum of two fractions, each having a log-normal distribution (the fine and large components). The problem amounts to determining six unknown parameters from two characteristics. In accordance with experimental data as well as with theoretical aerosol models, the total particle concentration n and the fraction of the large component [c.sub.2] are assumed to be constant for the central regions of the world ocean. In this way, the problem can be reduced to the determination of the acceptable value area of the remaining four parameters. For all models situated in this area, values of [Sigma] and [Alpha] fall within some intervals [Delta][Sigma] and [Delta][Alpha], specific for each aerosol type. Since the problem is ambiguous, the number of models comprising an acceptable ensemble is great. So this number is equal to 5972 in the example that illustrates our procedure. It is noteworthy, however, that all the models entering the ensembles have a similar microstructure within the active radius interval of 0.02-3 [[micro]meter], which is the main interval that governs the transmittance in the 0.3-1 [[micro]meter] spectral range. The average curve that can be plotted for the entire ensemble can be used as a solution to the problem, which is the main result of this study. We are also concerned with how aerosol transmittance measurements in one of the infrared channels could be used to diminish the ambiguity of the problem. The answer depends on the specific aerosol structure. In most cases, additional IR data in one channel barely decreases the ambiguity of the problem. However, such data might be useful for some other distributions. We consider the effect of six IR channels in our example.

The available data describing the incompressible zero-pressure-gradient boundary layer are reviewed in association with a range of studies which are either new or, to date, not very generally available. The new data cover a Reynolds number range 2.5 < [Re.sub.[Delta]2] x [10.sup.-3] < 58 and include measurements of all three turbulence perturbations and the Reynolds shear stress. They are assessed in relation to data in the range 0.4 < [Re.sub.[Delta]2] x [10.sup.-3] < 211 using established scaling laws. In common with other investigators we find that while scaling the mean flow leads to a high degree of apparent similarity, scaling of the turbulence quantities is in general not so satisfactory.

A full Reynolds stress equation (RSE) turbulence model accurately simulates an asymmetric double fin's three-dimensional shock wave/turbulent-boundary-layer interaction and resolves the counter-rotating vortex pair. The computed surface pressure tallies well with the experiment whereas the computer heat transfer coefficient achieves 20% improvement over the results from the k-epsilon model. The calculations involve the use of Reynolds-averaged Navier-Stokes equations, Roe's scheme, and an implicit approximate factorization method.

Fully developed compound shear and buoyancy driven mixing layers are predicted using a k-[Epsilon] turbulence model. Such mixing layers present an exchange of equilibrium in mixing flows. The k-[Epsilon] buoyancy constant [C.sub.[Epsilon]3] = 0.91, defined in this study for buoyancy unstable mixing layers, is based on an approximate self-similar analysis and an accurate numerical solution. One-dimensional transient and two-dimensional steady calculations are presented for buoyancy driven mixing in a uniform flow field. Two-dimensional steady calculations are presented for compound shear and buoyancy driven mixing. The computed results for buoyancy alone and compound shear and buoyancy mixing compare well with measured data. Adding shear to an unstable buoyancy mixing layer does not increase the mixing growth rate compared with that from buoyancy alone. The nonmechanistic k-[Epsilon] model which balances energy generation and dissipation using constants from canonical shear and buoyancy studies predicts the suppression of the compound mixing width. Experimental observations suggest that a reduction in growth rate results from unequal stream velocities that skew and stretch the normally vertical buoyancy plumes producing a reduced mixing envelope width.

Current information concerning three-dimensional turbulent boundary layers is discussed. Several topics are presented including (i) a detailed description of eleven experiments published since 1990. In nine cases cross flows are controlled by pressure gradients imposed from the freestream, but in two cases the cross flows are wall-shear-driven. The other topics include (ii) an examination of state of the art in measurement techniques; (iii) a look at some issues and ideas in turbulence modeling; and (iv) an introduction to new work on the visualization and description of quasi-coherent structures (high/low-speed streaks and turbulent vortices) in three-dimensional turbulent boundary layers.

Uniform suction and injection impact on laminar natural convection boundary layer flow stability is examined. The problem considers the flow for a vertical porous plate set at a constant temperature. Numerical solutions are derived for nonsimilar boundary layer equations using an efficient finite difference method and an iterative method. The results indicate suction and injection parameter impact on the flow process.

Experiments on simulating the atmospheric convective boundary layer (CBL), capped by a temperature inversion and affected by surface shear, were carried out in the thermally stratified wind tunnel of the Institute of Hydrology and Water Resources, University of Karlsruhe. The tunnel is of the closed-circuit type, with a test section 10 m long, 1.5 m wide, and 1.5 m high. The return section of the tunnel is subdivided into 10 layers, each driven by its own fan and heating system. By this means, velocity and temperature profiles can be preshaped at the inlet of the test section, which allows for the reproduction of developed CBL over comparatively short fetches. The bottom heating is controlled to produce the constant heat flux through the floor of the test section. The flow velocity components in the tunnel are measured with a laser Doppler system; for temperature measurements, the resistance-wire technique is employed. A quasi-stationary, horizontally evolving CBL was reproduced in the tunnel, with convective Richardson numbers [Ri.sub.[Delta]T] and [Ri.sub.N] up to 10 and 20, respectively, and the shear/buoyancy dynamic ratio [u.sub.*]/[w.sub.*] in the range of 0.2-0.5. Within the employed modeling approach, means and other statistics of the flow were calculated by temporal averaging. Deardorff mixed-layer scaling was used as a framework for processing and interpreting the experimental results. The comparison of the wind tunnel data with results of atmospheric, water tank, and numerical studies of the CBL shows the crucial dependence of the turbulence statistics in the upper part of the layer on the parameters of entrainment, as well as the modification of the CBL turbulence regime by the surface shear.

Spectral analysis of high-resolution turbulence data from the South Australian Cessna research aircraft is performed in an investigation of the multiscale nature of vertical transport processes in the atmospheric boundary layer (ABL) during TOGA COARE. The flights were conducted in the vicinity of large cloud cluster systems in the intertropical convergence zone, but away from the most intense mesoscale (100s of km) convective systems within the clusters. A number of very long (up to 430 km) and low (20-70 m) continuous data runs, composing an excellent dataset for studying the spectral composition of near-surface fluxes, are complemented by eight 'stack' patterns providing important information regarding vertical variations. The ABL in these regions is found to be highly horizontally heterogeneous, due to the intrusion of cool air masses associated with precipitating cumulus and cumulonimbus clouds, and the action of lines of convection on a range of scales. Not only does this lead to large variations in the surface turbulent flux field, but it can also generate significant direct fluxes in a submesoscale (20-50 km) range at low altitudes, which are not expected to be controlled by ABL parameters. That is, enhanced motions resulting from the action of precipitating cumulus clouds in the presence of wind shear can lead to strong entrainment of air into the subcloud layer, and, in addition, gravity waves generated above the ABL can also influence subcloud motion. Analysis of the form and consistency of the cospectra suggests that, despite the absence of a clear 'gap' in the power spectra of the major variables, it is nevertheless possible to achieve a reasonable partitioning between 'ABL turbulence' and the larger-scale processes via a simple spectral separation with a crossover wavelength at around 2 km. This useful characteristic appears to reflect an ability of the ABL turbulence to maintain a high degree of coherency in spite of the changing conditions imposed by the mesoscale disturbances.

Onset and coverage of small cumulus clouds depend on the relative abundance of surface-layer air parcels possessing favorable buoyancy and moisture - two variables that are coupled through the surface energy budget. This abundance is described using a joint frequency distribution (JFD) as a function of virtual potential temperature [[Theta].sub.v] and height of the lifting condensation level [z.sub.LCL]. It is shown analytically that the shape and spread of this JFD depends on the ranges of Bowen ratios and solar forcings (albedoes, cloud shading, etc.) that exist within a domain of heterogeneous land use. To sample the character of such JFDs in the real atmosphere, a case study is presented using turbulence data gathered by aircraft flying in the surface layer of southwest France. This case study includes 4 days of clear skies during the Hydrologic Atmospheric Pilot Experiment (HAPEX) of 1986. The full flight track during HAPEX overflew a wide range of land use including evergreen forest, corn, vineyards, pastures, and irrigated fields over varied topography. The JFDs from these full tracks are found to be quite complex, being frequently multimodal with a convoluted perimeter. However, when a full track is broken into segments, each over a subdomain of quasi-homogeneous land use, the resulting segment JFDs are mono-modal with simpler topology. Such a characterization of JFDs provides guidance toward eventual subgrid cumulus parameterization in large-scale forecast models, with associated impacts in aviation forecasting, pollutant venting and chemical reactions, vertical dispersion and turbulence modulation, and radiation balance in climate-change models.

A new method suggested by P.G. Huang, P. Bradshaw and T.J. Coakley to estimate the skin friction and velocity profiles of compressible turbulent boundary layers fails to accurately estimate the impact of Reynolds number on the mean flow distribution in the boundary layer at low Reynolds numbers. The difference between the predicted velocity profile and the experimental data increases with the increase in Reynolds number.

Flow visualization using liquid-crystal technique on three swept cylinders determines the boundary-layer transition occurring due to attachment-line contamination and/or crossflow instability at hypersonic speeds. Transition on the attachment line occurs at freestream Reynolds numbers of 0.15-0.33 X 10 to the sixth power and 0.9-1.2 X 10 to the sixth power, for sweep angles of 45 and 60 degrees respectively. The attachment-line transition around the critical roughness heights depends on spanwise Mach number. The effect of Mach number on transition Reynolds number is discussed.

The optimal transition position in which minimum power is consumed to overcome drag depends upon the mean flow speed and disturbance conditions characterized by the amplification factor. Boundary-flow suction reduces the wake drag in a commercial aircraft and decreases the total power consumed. The study derives various components of the power balance equation namely, wake drag, momentum loss, thrust, and pump power.

Equations governing compressible boundary-layer laminar flow of a two-phase particulate suspension are developed based on a continuum representation of both phases. These equations include such effects as particle-phase viscous stresses, variable position-dependent particle slip coefficient, and general power-law viscosity-temperature and thermal conductivity-temperature relations. The dimensionless form of the equations are applied to the problem of flow over a semi-infinite flat surface. An appropriate transformation is employed to allow proper comparison with previously published results for special cases of this problem. The full coupled system of equations is solved numerically via an implicit finite-difference method. Graphical results for the density, and temperature profiles as well as the displacement thicknesses, skin-friction coefficients, and the wall heat transfer coefficient for both the fluid and particle phases are presented and discussed in detail. In addition, a parametric study is performed to illustrate the influence of the particle to fluid viscosity ratio and the viscosity-temperature power exponent on the flow properties.

Aircraft measurements of vertical air motions are used in a process of conditional sampling to select updraft and downdraft cores during a period of strong lake-effect convection. Corresponding measurements of temperature and moisture are used to calculate the buoyancies of the cores and to evaluate the dependence of the calculated buoyancy on the horizontal extent of core environment used in the calculations. Results suggest that calculated buoyancies are relatively insensitive to the definition of core environment.

On many planets there is a continuous heat supply to the surface and a continuous emission of infrared radiation to space by the atmosphere. Since the heat source is located at higher pressure than the heat sink, the system is capable of doing mechanical work. Atmospheric convection is a natural heat engine that might operate in this system. Based on the heat engine framework, a simple theory is presented for atmospheric convection that predicts the buoyancy, the vertical velocity, and the fractional area covered by either dry or moist convection in a state of statistical equilibrium. During one cycle of the convective heat engine, heat is taken from the surface layer (the hot source) and a portion of it is rejected to the free troposphere (the cold sink) from where it is radiated to space. The balance is transformed into mechanical work. The mechanical work is expended in the maintenance of the convective motions against mechanical dissipation. Ultimately, the energy dissipated by mechanical friction is transformed into heat. Then, a fraction of the dissipated energy is radiated to space while the remaining portion is recycled by the convecting air parcels. Increases in the fraction of energy dissipated at warmer temperatures, at the expense of decreases in the fraction of energy dissipated at colder temperatures, lead to increases in the apparent efficiency of the convective heat engine. The volume integral of the work produced by the convective heat engine gives a measure of the statistical equilibrium amount of convective available potential energy (CAPE) that must be present in the planet's atmosphere so that the convective motions can be maintained against viscous dissipation. This integral is a fundamental global number qualifying the state of the planet in statistical equilibrium conditions. For the earth's present climate, the heat engine framework predicts a CAPE value of the order of 1000 J [kg.sup.-1] for the tropical atmosphere. This value is in agreement with observations. It also follows from our results that the total amount of CAPE present in a convecting atmosphere should increase with increases in the global surface temperature (or the atmosphere's opacity to infrared radiation).

It is well established that at low Rossby and Froude numbers modes possessing potential vorticity behave differently from gravity-inertial wave modes. Wave energy cascades relatively more efficiently downscale to the dissipation, resulting in a geostrophic adjustment. For this reason, it has been suggested that wave energy be subjected to relatively stronger dissipation via 'divergence damping.' This study reports separate measurements of the effective eddy damping acting on wave and rotational modes in simulations of nonhydrostatic Boussinesq flow. The method employs an arbitrary cutoff wavenumber, [k.sub.c], within the simulation's range of resolved scales, in order to calculate explicitly the effect of the smaller-scale motion on wavenumbers below [k.sub.c]. It is found that the rotational-mode eddy viscosity resembles that found in studies of 2D turbulence, with a significant negative range, while it is positive at all wavenumbers for the wave modes.

An analysis of the boundary-layer growth of air flowing on a horizontal flat plate enclosed in a de/anti-icing fluid film indicates that the air/fluid interface effect is geometrical in nature. An experiment shows that the first wave originates at nearly 8 m/s. The model of stability provides a suitable consistency between experiment and theory for the waveform at air/fluid interface. The shear stress caused by airflow is unable to generate suitable waves.

Turbulence measurements for both momentum and heat transfer are taken in a low-velocity, turbulent boundary layer growing naturally over a concave wall. The experiments are conducted with negligible streamwise acceleration and a nominal free-stream turbulence intensity of [approximately]8 percent. Comparisons are made with data taken in an earlier study in the same test facility but with a 0.6 percent free-stream turbulence intensity. Results show that elevated free-stream turbulence intensity enhances turbulence transport quantities like [Mathematical Expression Omitted] and [Mathematical Expression Omitted] in most of the boundary layer. In contrast to the low-turbulence cases, high levels of transport of momentum are measured outside the boundary layer. Stable, Gortlerlike vortices, present in the flow under low-turbulence conditions, do not form when the free-stream turbulence intensity is elevated. Turbulent Prandtl numbers, [Pr.sub.t], within the log region of the boundary layer over the concave wall increase with streamwise distance to values as high as 1.2. Profiles of [Pr.sub.t] suggest that the increase in momentum transport with increased free-stream turbulence intensity precedes the increase in heat transport. Distributions of near-wall mixing length for momentum remain unchanged on the concave wall when free-stream turbulence intensity is elevated. Both for this level of free-stream turbulence and for the lower level, mixing length distributions increase linearly with distance from the wall, following the standard slope. However, when free-stream turbulence intensity is elevated, this linear region extends farther into the boundary layer, indicating the emerging importance of larger eddies in the wake of the boundary layer with the high-turbulence free stream. Because these eddies are damped by the wall, the influence of the wall grows with eddy size.

The authors present a study of flow fields through the use of transonic turbine cascade flows. Topics include boundary layers, mathematical models, and shock structures

The initial laminar thermal boundary-layer fiow past an impulsively started translating and spinning rotational symmetric body of uniform temperature is investigated. Velocity components and temperature are expanded in series in powers of time. Leading and first-order functions are obtained analytically, second and third-order functions are determined numerically. Application of the general results to a sphere shows that the surface heat flux is reduced in the neighborhood of the point of separation and enhanced by the reversed flow inside the separated region.

While many studies have investigated the influence of flow structure in a turbulent boundary layer on the wall pressure signature, the conclusions of these studies have often been 'limited due to their reliance on a single observation. These single observations include investigations using one signal processing method over a range of locations, or a variety of signal processing techniques at a single location in the boundary layer. Hence, the conclusions often include conjecture on the impact of the flow structure at other physical locations, as well as predictions on the observable effect of flow structure should the turbulence be examined with a different signal processing perspective. In the current study, experimental data of simultaneous wall pressure and velocity fluctuations across the boundary layer have been obtained in a low-noise flow facility. These data have been examined using a variety of signal processing techniques, including probability distributions and spectral analysis. The distinct features of the Reynolds stress within the boundary layer and the observed irrotational motion at the outer edge of the boundary layer were evident in the results from each signal processing method. The influence of these two flow patterns on the wall pressure spectrum was identified and support conjectures made on the correlation between turbulence source locations and frequency bands in the wall pressure spectrum. The investigation demonstrates the necessity and utility of multiple perspectives over a range of spatial locations to study turbulence.

A new criterion for the separation of incompressible, two-dimensional, laminar and turbulent boundary layers with steady mean flow is introduced. Applicable only to cases involving smooth surfaces and the absence of heat and mass transfer, it is based on the idea that the specific momentum defect, otherwise known as the ratio of the boundary-layer momentum defect to the freestream momentum, is at a maximum at detachment 'when considered a function of the shape parameter.'

The three-dimensional separation of turbulent flow was studied. Specifically, the flow past a large-scale axisymmetric model in a subsonic wind tunnel was investigated via surface flow visualizations, surface pressure measurements, pressure probes and laser Doppler velocimetry. It was observed that during separating, the boundary layer evolved from a shear flow into a vortex. In addition, the difference in direction between the velocity gradient vector and the shear stress vector rose as the skewness of the boundary layer increased.

The structure of a two-dimensional, adiabatic, supersonic, free shear layer separating a flowfield consisting of Mach 1.8 air tangentially injected into a Mach 4 flow was investigated. To gain a deeper understanding of the physics of compressible turbulence, several methods were used to measure the turbulent flow structure angle, length scales, mass flux spectra and Mach number turbulence intensity.

Two new classes of self-similar solutions pertaining to steady, laminar boundary layers in nonadiabatic, two-dimensional, hypersonic flows of a perfect gas are examined to gain insight into the aerodynamics of high-speed engine inlets. The first involves an exponential pressure rise while the second entails a curved ramp-type pressure increase, both of which the boundary layer 'does not necessarily separate.'

The boundary-layer transition on a swept-wing leading-edge model at the NASA Langley Supersonic Low-Disturbance Tunnel was investigated at Mach 5. Specifically, measurements were taken of surface pressure and wall temperature distributions on pressure and thin-skin thermocouple models along with flow visualizations. The results, which were compared with numerical solutions to the thin-layer Navier-Stokes equation and N-factors derived via the envelope e(sup N) method, suggest that travelling crossflow disturbances are the likeliest cause of such transitions.

Research work on the impact of three-dimensional mean flow on the near-wall structure of turbulent boundary layers is assessed. These include studies of flows approaching a wedge, flows over a rotating disk and the development of embedded vortices in wedge flow boundary layers. All were characterized by a reduction in Reynolds shear stress and the presence of quasistream vortices as well as low- and high-speed streaks in the near-wall region.

The aerodynamic problem of inviscid/viscous interactions between sharp fin-induced shock waves and a turbulent boundary layer was studied. Specifically, the mean surface pressure and heat transfer rate distributions were measured for different fin angles of attack at Mach 5. The results proved that the mean surface pressure distributions have a conical symmetry but disproved the view that the mean surface heat transfer distributions are conical.

The performance of Thompson's, Tam and Webb's and Giles' mathematical formulations of boundary conditions for unsteady flows in computational aeroacoustics were evaluated. Specifically, the three boundary conditions, which were derived from the axisymmetric linearized Euler equations, were applied to the problem of an acoustic field of a monopole in a uniform flow in the axial direction.