Vorticity and acoustics measurements in impinging jet flows. Part 1: Vorticity measurements. Part 2: Acoustics measurements
Explore the source record for details and available documents.
Foss, J. F.↗
Engineering topics
Foss, J. F.
Publications and source records attributed to Foss, J. F..
Developments in the large angle oblique jet impingement flow investigation
Single-wire (hot-wire) measurements are presented of the mean velocity and turbulence quantities near the impact plate for a 45-degree impingement flow responsible for acoustic noise production. These results are summarized along with the conclusions which shaped the subsequent direction of the study of large angle oblique jet impingement flow. The development of a unique signal processing circuit for finding the instantaneous transverse vorticity from an array of four hot-wires is discussed.
Foss, J. F.↗
Preliminary results from an experimental investigation of the initial condition effects on a turbulent shear layer
A flow facility to create a plane shear layer from a laminar and a turbulent boundary layer was established. The spread rate parameter for these two conditions was accurately determined. A four percent (maximum), nonturbulent disturbance level exists in the laminar boundary layer.
Foss, J. F.↗
The use of digital techniques to examine the intermittent region of a turbulent jet
Voltage signals, sampled at a high rate in the intermittent region of a round jet, are analyzed to provide instantaneous velocity vector information and measures of the vorticity and dissipation scales. A clustering routine to assess the feasibility of using the voltage readings to define the vortical, nonvortical state of the flow is also utilized. The results indicate that the clustering routine is partially successful; more sophisticated discrimination techniques will be required for a complete specification.
Foss, J. F.↗
The effect of exit conditions on the development of an axisymmetric turbulent free jet
The mean flow in the near field of a submerged axisymmetric jet emitting from a plane wall is presented. An experimental configuration to provide a nearly uniform mean velocity profile with a core of homogeneous turbulence of variable intensity and scale was developed. Eight cases with intensity values of 0.004 less than or equal to U prime less than or equal to 0.035 and integral scales up to l sub x/R = 0.28 were investigated using conditional sampling techniques. It was found that the jet exhibits an increasing momentum flux in the near field. Contrary to expectation and the accepted assumption of ambient static pressure in a turbulent jet, results seem to be conclusive and borne out by comparison with published data. Both integral measures, mass and momentum flux ratios, are insensitive to exit turbulence variations, but, the detailed structure (including centerline velocity) variations with exit conditions are systematic and explainable.
Kleis, S. J.↗
Research on free and impinging jets for the development of STOL aircraft
The effect of the exit plane conditions on the initial region of an axisymmetric jet was systematically investigated. An essentially top-hat mean velocity profile and a homogeneous turbulence structure were maintained at the exit plane for eight distinct scale and intensity conditions. Mass and momentum flux values are independent of the exit turbulence structure for the range investigated; however, a significant (approximately 25%) increase in the latter implies a pronounced static pressure decrement inside the jet. Details of the velocity profile and turbulence structure are influenced by the exit plane conditions. The three radial-axial components of the Reynolds stress tensor have been conditionally sampled and are analyzed to show the initial condition effects.
Foss, J. F.↗
Measurements in a large angle oblique jet impingement flow
Velocity and surface pressure measurements, in the flow field of an obliquely impinging jet, and their interpretation as regards the governing mechanics and the aerodynamic noise generation characteristics of such a flow are reported. A computer controlled probe positioning mechanism allowed the measurement of the velocity magnitude and direction in the plane parallel to the plate. The mean velocity and Reynolds stress components were recorded. Measures of the terms in the momentum equation reveal the character of the pressure gradients in the neighborhood of the stagnation point. The effects of the stagnation streamline location on the vorticity field and the vortex sound considerations are discussed in relationship to the aerodynamic noise generation effects of this flow.
Foss, J. F.↗
The initiation, development, and decay of the secondary flow in a bounded jet
The secondary flow in a low aspect ratio incompressible turbulent bounded jet is described in terms of a near, middle, and far field in which the secondary motion is initiated, developed, and decayed, respectively. The initiation of the secondary flow is explained by the distortion of the planar vortex loops which bound the jet at the exit plane. In the region away from the bounding plates, the vortex loop distortion is similar to that found in rectangular free jets; however, the bounding plates cause an additional production of streamwise vorticity near the plates which has no counterpart in the free jet flow. Downstream of the jet core region, a large-scale secondary flow developes from this vorticity. Farther downstream the secondary flow decays; the resultant flow may be characterized as a combination of a plane jet and boundary layer flows. This explanation is supported by the vorticity and velocity data of this investigation.
Holdeman, J. D.↗
Preliminary results for a large angle oblique jet impingement and flow and for the effect of initial conditions on the near field of an axisymmetric jet
The structure of an axisymmetric jet in the near field is discussed for jet noise and for jet impingment schemes for STOL aircraft. It is inferred from previous studies, and the inference is supported by analysis, that the scale and intensity of the turbulence structure at the jet exit plane are the important boundary conditions which effect the development of the flow in the near field. The techniques to study these effects while maintaining a uniform mean flow and the results which document the range of the initial conditions are presented. The large angle, oblique jet impingment condition is of interest in terms of the jet/flap interaction. Detailed turbulence data can be obtained with the specially constructed facility. The development of the flow and instrumentation system and initial data from the new facility are presented.
Foss, J. F.↗
A study of the round jet/plane wall flow field
Impingement angles, between the axisymmetric jet axis and the plane wall, from zero to 15 degrees have been examined for nozzle heights of 0.75, 1.0, 1.5 and 2.0 diameters and for: (1) a fully developed pipe flow, and (2) a relatively uniform exit velocity condition. Velocity measurements have been used to define isotach contours and to determine mass, momentum and energy flux values for the near field (within five diameters) of the jet. Surface pressure measurements have been used to define surface pressure forces and jet centerline trajectories. The geometric and flow conditions examined and the interpretation of the results have been motivated by the externally blown flap STOL aircraft application.
Foss, J. F.↗