WorldCat Identities

Wygnanski, Israel

Overview
Works: 14 works in 20 publications in 1 language and 23 library holdings
Roles: Author
Classifications: TL570,
Publication Timeline
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Most widely held works by Israel Wygnanski
Theoretical and experimental investigation of blowing applied to an aerofoil with a sharp leading edge. by Israel Wygnanski( )

2 editions published in 1962 in English and held by 3 WorldCat member libraries worldwide

"Experiments have been made on a thin, two-dimensional aerofoil with sharp leading edge and with a jet blowing through a mid-chord slot on the upper surface for boundary-layer and circulation control.The measurements were made at low Mach number and included the effect of altering the angle of blowing for it was anticipated that this would help control the leading edge separation bubble.It was found that variation of the blowing angle caused very little change in lift coefficient but produced an appreciable change in moment coefficient. With the jet discharging at an angle and subsequently reattaching to the surface a separation bubble of low pressure was formed downstream of the slot which reduced the nose-up pitching moment about the guarter-chord point. The reattachment distances for this bubble have been successfully predicted by an extension of the Bourque-Newman theory for reattaching jets. The lift and moment coefficients before the stall were compared with Spence's jet flap theory which has been extended within the context of thin aerofoil theory, to include the effect of jet entrainment. It is predicted that the entrainment tends to increase the lift by increasing the effective camber of the aerofoil and the detailed agreement between this theory and experiment is good." --
Some effects of jet entrainment on the external fluid surrounding the jet, with particular reference to the flow about aerofoils. by Israel Wygnanski( )

2 editions published in 1964 in English and held by 3 WorldCat member libraries worldwide

"The flow induced by entrainment into a jet outside the boundaries of the jet and the forces arising from it, with particular reference to aerofoils, are discussed in this thesis. For the purpose of analysis the jet is replaced by a continuous sink of strength equivalent to the inflow into the jet. When a jet flows over a surface of an aerofoil the effective camber of the aerofoil is increased due to the downwash velocity associated with jet entrainment. This increases the lift attained by the aerofoil as well as the nose down pitching moment. [...]" --
General description and calibration of the McGill 3 ft. x 2 ft. low speed wind tunnel by Israel Wygnanski( Book )

1 edition published in 1961 in English and held by 2 WorldCat member libraries worldwide

On The Turbulent 'Spot' in a Boundary Layer Undergoing Transition( Book )

1 edition published in 1975 in English and held by 1 WorldCat member library worldwide

Artifically initiated turbulent spots in a Blasius boundary layer were investigated experimentallly using hot wire anemometers. Electrical discharges initiated the spots which grew in all directions as they were swept downstream by the mean flow. Conditional sampling methods enabled the ensembling of data and yielded an average shape of the spot and the mean flow field in its vicinity. All quantities measured seem to be independent of the type of disturbance which generated downstream
The Control of Separation from Curved Surfaces and Blunt Trailing Edges( Book )

1 edition published in 2002 in English and held by 1 WorldCat member library worldwide

The project that was initiated in the fall of 1999 encompasses three exploratory studies: (1) A pulsed wall jet over a curved surface in the absence of an external stream (2) Pulsation emanating from a circular cylinder in streaming flow. (3) The application of active flow control to an airfoil having a divergent trailing edge. The report will cover all three experiments although most progress (beyond the exploratory stage) was made on understanding the wall jet flowing over a convex surface. Some of the experimental work on this project was initiated prior to the last funding period but data analysis took more time some of the results have been discussed in interim progress reports. The other investigations are still ongoing at a lower pace
The Effect of Curvature on the Evolution of a Boundary Layer Subjected to a Strong Adverse Pressure Gradient( Book )

1 edition published in 2001 in English and held by 1 WorldCat member library worldwide

Negligible wall shear stress provides the criterion that minimizes the distance over which boundary layer can decelerate without separating from the surface. Over the past few years, we have been carefully investigating the boundary layer that is continuously maintained on the verge of separation, without actually being allowed to separate 1. The experimental facility that was used consists of a contraction, a constant area throat, and a two-dimensional variable geometry expansion inserted into the 2' by 3' test section of a low speed wind tunnel (figure 1). The expansion is corrected of Lexan supported by electric actuators mounted on gimbals and capable of distorting the surface under computer control. The surface geometry can vary over a wide range of pressure gradients and streamline curvature. The transition between the throat and the test surface is accomplished by means of a circular cylinder to which the lexan surface is attached, thereby establishing the initial slope of the test surface. The side-wall boundary layers were removed by using suction and the measurements were made on the boundary layer developing on the curved surface
Pressure Transducer and Computer System Providing Instantaneous Information over a Surface and Time-Dependent Predictive Ability( Book )

2 editions published in 2002 in English and held by 1 WorldCat member library worldwide

A PSI 8400 pressure transducer system providing mean pressures almost instantaneously out of 48 ports and capable of responding to low frequency oscillations was purchased and absorbed by the laboratory in support of the various separation control investigations. An array of 64 Endevco surface mounted transducers capable of dynamic measurements of pressure oscillations were also bought together with National Instruments signal conditioner units. These were already used in monitoring pressure oscillations in a cavity that were generated by actuators used on wings of the XV-15 and V-22 models for the purpose of download alleviation. Four powerful PC computers and a server were purchased for data acquisition and storage, as well as for LES computations supporting the experiments being carried out in the Aerodynamic Laboratories at the University of Arizona
Dynamically Altered Compliant Surface and Measuring Equipment for use in the Control of Separation by Oscillatory Means( Book )

2 editions published in 1998 in English and held by 1 WorldCat member library worldwide

We have selected a vendor (DANTEC) and purchased a three dimensional LDA. The selection process took over 6 months to complete with three companies competing (DANTEC, AEROMETRICS & TSI). The instrument has been installed and was immediately used on two DoD sponsored projects: (1) On a boundary layer that is continuously maintained on the verge of separation (the Stratford ramp), a project that is sponsored by ONR. (2) On studying the separation of a wall jet that flows over a circular cylinder. In both experiments regions of local, time dependent reverse flow were detected and the typical hot wire was incapable to provide accurate results. I am enclosing a copy of an article that was very recently accepted for publication by the Journal of Fluid Mechanics after we have checked the reliability of the data with the new equipment that was purchased on this grant (see specifically figures 3-5)
Film Cooling by a Pulsating Wall Jet( Book )

2 editions published between 1997 and 2000 in English and held by 1 WorldCat member library worldwide

This report summarizes the results of an experimental, numerical, and theoretical project that was initiated in 1994 with funding under AFOSR Contract Number F49620-94-1-0131. The objective of the work was to perform a fundamental exploration of the heat transfer and fluid mechanics in a wall jet with emphasis on applying passive techniques to control or manipulate the rates of heat transfer. After constructing the apparatus, developing the instrumentation, and developing the computer codes for the numerical simulation and the models for the theoretical investigations, we proceeded to study the effects of heating and cooling on the steady laminar wall jet. We examined the evolution of small-amplitude perturbations which were externally introduced into the flow. The amplitudes of the disturbances were significantly increased in the second stage of the investigation and their effect on the flow and temperature field was analyzed. The primary finding suggests that Reynolds analogy is not as universally applicable as we were lead to believe primarily when the mean velocity profile and the mean temperature profile are different or when the flow is periodic
Active Flow Control on Hurley's Free-Streamline Airfoil and Delta( Book )

2 editions published in 1999 in English and held by 1 WorldCat member library worldwide

This was a joint effort by The University of Arizona (UA) and Arizona State University (ASU). The work was directed toward the application of active flow control to a free-streamline airfoil whose structural vibrations were integrated into the control strategy. The Phase I accomplishments reported here demonstrate that efficient tree-shear-layer control is possible and the low drag of the free-streamline airfoil is a reality
Transition in a Boundary Layer and in a Pipe Flow( Book )

1 edition published in 1977 in English and held by 1 WorldCat member library worldwide

An experimental investigation was carried out in shear flows undergoing transition to turbulence and in fully developed turbulent flows. The aim of the experiment is to understand and control transition, as well as to determine the effects of transition on fully turbulent flows. In the boundary layer case this effect was clearly established at moderate Reynolds numbers. (Author)
The Structure of Turbulent Velocity Fields( Book )

1 edition published in 1985 in English and held by 1 WorldCat member library worldwide

A systematic study of two-dimensional, turbulent, small-deficit wakes investigated the structure and universality of their self-preserving states. Various wake generators, including circular cylinders, a symmetrical airfoil, a flat plate, and an assortment of screens of varying solidity, were studied for a wide range of downstream distances. The drag coefficient of most generators, and therefore the momentum thickness, was tailored to be identical, permitting comparison at identical Reynolds numbers and aspect ratios. The flat plate and airfoil and had a small, trailing-edge flap which could be externally driven to introduce forced sinuous oscillations into the wake. Results indicate that the normalized characteristics velocity and length scales depend on the initial conditions, while the shape of the normalized mean velocity profile is independent of initial conditions or nature of the generator. The normalized distributions of the longitudinal turbulence intensity, however, are dependent on the initial conditions. Linear inviscid stability theory, in which the divergence of the mean flow was taken into account, predicts quite well the amplification and transverse distributions of amplitudes and phases of externally imposed sinuous waves on a fully developed turbulent wake generated by a flat plate. There is a strong indication that the large structures observed in the unforced wake are related to the two-dimensional instability modes and therefore can be modelled by linear stability theory. Interaction of the two possible modes of instability may be responsible for the vortex street-type pattern observed visually in the small-deficit, turbulent wake
The Forced Turbulent Wall Jet Effects of Pressure Gradient and Curvature( )

1 edition published in 1996 in English and held by 0 WorldCat member libraries worldwide

The studies completed in the period of the proposal were in three parts: (1) Both hot wire and PIV data have been obtained on the Coanda cylinder. Strong influences of curvature and of the pressure gradient on the mean and the turbulence quantities were found. New structures were observed around the cylinder in the forced case. A theoretical model was established for the mean flow, which will be an important tool in the further stability studies. (2) Two types of weak wall jet have been observed. Length and velocity scales were found and applied in successful normalization of the mean velocity profiles. Furthermore, three instability modes, coupled to each other, were investigated through forcing. (3) A novel technique for identification of coherent motions was developed which can eliminate the influence of phase jitter and discover much more coherent energy than the conventional phase locked ensemble averaging technique, based on which a reasonable coherent energy budget was established for the first time. This technique will be applied to explore the role of coherent motion in the control of separation
Investigation of the Physics of Screech in Supersonic Jets and Turbulent Boundary Layers at High Reynolds Number and Control of Separation Through Oscillatory Blowing( )

1 edition published in 1996 in English and held by 0 WorldCat member libraries worldwide

Using a flapped NACA 0015 airfoil, measurements of static pressure and lift, with and without oscillatory forcing from the leading edge and flap, demonstrated effective separation control and lift enhancement over the range 0.1<M<0.4. Measurements showed that the lift increment was sensitive to the dimensionless forcing frequency. Additionally, a suction pressure coefficient of nearly -5.0 was produced on a previously stalled airfoil at M=0.4, indicating a region of supercritical flow on the airfoil, and suggesting that oscillatory blowing is a viable separation-control technique under compressible flow conditions. Using both the NDF test-section floor boundary layer and a suspended axisymmetric body, a range of momentum thickness Reynolds numbers of 7000<Re<50000 was investigated with a hot-wire anemometer. Streamwise mean and rms velocity and spectra in these boundary layers showed good agreement with established scaling observations. An increasing separation of scales and the appearance of a second low-frequency spectral peak were observed indicating a clear discrimination between inner and outer scales at high Reynolds number. Although some dependence on both axial and momentum thickness Reynolds number was observed, there appeared to be a linear relationship between friction velocity and free-stream velocity over this wide range of Reynolds numbers
 
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English (20)