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Author: I. S. Gartshore
Publisher:
ISBN:
Category :
Languages : en
Pages : 33
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A method for calculating the growth of a turbulent wall jet in streaming flow was developed. The flow is assumed to be two-dimensional, incompressible and over a plane, smooth wall. Downstream variations of pressure are permitted and separation in an adverse pressure gradient may be predicted. The method incorporates procedures for matching the flow to that at the blowing slot, although it is postulated that the upstream boundary layer there is thin enough that the wall jet develops without an unmixed wake (i.e. there is not a minimum in the mean-velocity profile). The method incorporates four integral momentum equations taken from the wall to various points in the flow. The calculation of the outer shearing stress, although empirical, is based on the large-eddy equilibrium hypothesis and therefore has some foundation. The remaining empiricism in the method is based on measurements in self-preserving wall jets. The method was used to predict the jet-momentum coefficient required to suppress separation over a trailing-edge flap attached to a thin aerofoil. Plausible curves have been obtained using assumed values of upstream boundary layer at the slot. (Author).
Author: I. S. Gartshore
Publisher:
ISBN:
Category :
Languages : en
Pages : 33
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Book Description
A method for calculating the growth of a turbulent wall jet in streaming flow was developed. The flow is assumed to be two-dimensional, incompressible and over a plane, smooth wall. Downstream variations of pressure are permitted and separation in an adverse pressure gradient may be predicted. The method incorporates procedures for matching the flow to that at the blowing slot, although it is postulated that the upstream boundary layer there is thin enough that the wall jet develops without an unmixed wake (i.e. there is not a minimum in the mean-velocity profile). The method incorporates four integral momentum equations taken from the wall to various points in the flow. The calculation of the outer shearing stress, although empirical, is based on the large-eddy equilibrium hypothesis and therefore has some foundation. The remaining empiricism in the method is based on measurements in self-preserving wall jets. The method was used to predict the jet-momentum coefficient required to suppress separation over a trailing-edge flap attached to a thin aerofoil. Plausible curves have been obtained using assumed values of upstream boundary layer at the slot. (Author).
Author: Jean Piquet
Publisher: Springer Science & Business Media
ISBN: 3662035596
Category : Technology & Engineering
Languages : en
Pages : 767
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Book Description
obtained are still severely limited to low Reynolds numbers (about only one decade better than direct numerical simulations), and the interpretation of such calculations for complex, curved geometries is still unclear. It is evident that a lot of work (and a very significant increase in available computing power) is required before such methods can be adopted in daily's engineering practice. I hope to l"Cport on all these topics in a near future. The book is divided into six chapters, each· chapter in subchapters, sections and subsections. The first part is introduced by Chapter 1 which summarizes the equations of fluid mechanies, it is developed in C~apters 2 to 4 devoted to the construction of turbulence models. What has been called "engineering methods" is considered in Chapter 2 where the Reynolds averaged equations al"C established and the closure problem studied (§1-3). A first detailed study of homogeneous turbulent flows follows (§4). It includes a review of available experimental data and their modeling. The eddy viscosity concept is analyzed in §5 with the l"Csulting ~alar-transport equation models such as the famous K-e model. Reynolds stl"Css models (Chapter 4) require a preliminary consideration of two-point turbulence concepts which are developed in Chapter 3 devoted to homogeneous turbulence. We review the two-point moments of velocity fields and their spectral transforms (§ 1), their general dynamics (§2) with the particular case of homogeneous, isotropie turbulence (§3) whel"C the so-called Kolmogorov's assumptions are discussed at length.
Author: A. G. T. Cross
Publisher:
ISBN:
Category :
Languages : en
Pages : 88
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Author: Wallace Alexander McGahan
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 106
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Author: James Franklin Campbell
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 40
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Author: Douglas Howard Neale
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 534
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Book Description
An experimental study of various wall jet flows was conducted. The major areas of investigation were: The wall jet injected into still air; The wall jet under a constant-pressure main-stream flow; The wall jet subjected to an adverse pressure gradient imposed by a retarded main-stream flow with a substantially thickened initial boundary layer; The wall jet subjected to an adverse pressure gradient imposed by a retarded main-stream flow with a thickened and distorted initial boundary layer. Detailed velocity profile and local skin friction measurements were made at numerous streamwise distances from the jet slot. For the case in which no main-stream flow was present, the studies were carried out for a wide range of slot Reynolds numbers. For the wall jets with main-stream flow, selected ratios of free-stream velocity to jet velocity at the jet slot were investigated. The growth of characteristic thickness and decay of jet peak velocity is presented for all wall jet studies. Also, velocity and temperature profile similarity is described. Skin friction laws are shown for the constant-pressure wall jets and a single 'law of the wall' valid for all wall jet studies is set forth. Finally, the skin friction and velocity profile measurements are presented in tabular form. (Author).
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 45
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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.
Author: John R. Weske
Publisher:
ISBN:
Category :
Languages : en
Pages : 24
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The characteristics of 3-dimensional wall jets are strongly influenced by secondary motion particularly in the region close to the nozzle. There is evidence suggesting that jets from narrow and tall nozzles will spread a wall jet more broadly over a wall than low and broad nozzles. Three-dimensional wall jets with pressure gradients, in the region close to the nozzle are subject to the same effects of secondary motions as are wall jets without pressure gradients, while in their later course they may acquire the characteristics of turbulent flow in ducts. Theoretical investigation of the action of Reynolds stresses serves to clarify the nature of secondary motions and to show the reason for contrasting characteristics of secondary flow in jets and in ducts as well as the fading out of secondary motion with increasing jet diffusion. (Author).
Author: N. Rajaratnam
Publisher: Elsevier
ISBN: 0080869963
Category : Science
Languages : en
Pages : 315
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Book Description
Turbulent Jets
Author: D. E. Guitton
Publisher: 1970 [c1974]
ISBN:
Category : Jets
Languages : en
Pages : 826
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Book Description
