Reynolds Stress Distribution Around a Large-Scale Coherent Vortex in a Turbulent Boundary Layer

1995 ◽  
pp. 346-350 ◽  
Author(s):  
H. Makita ◽  
K. Sassa
Keyword(s):  
Boundary Layer ◽  
Stress Distribution ◽  
Turbulent Boundary Layer ◽  
Reynolds Stress ◽  
Large Scale ◽  
Coherent Vortex

A coherent structure model of the turbulent boundary layer and its ability to predict Reynolds number dependence

1991 ◽  
Vol 336 (1641) ◽  
pp. 103-129 ◽  
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Reynolds Stress ◽  
Coherent Structure ◽  
Large Scale ◽  
Outer Region ◽  
Structure Model ◽  
Hairpin Vortices ◽  
Reynolds Number Dependence

The coherent motions identified in passively marked turbulent boundary-layer experiments are reviewed. Data obtained in our laboratory using simultaneous hot-wire anemometry and flow visualization are analysed to provide measures of the percent contribution of the coherent motions to the total Reynolds stress. A coherent structure model is then developed. In the outer region the model incorporates the large-scale motions, the typical eddies and their interactions. In the wall region the model is characterized by the long streaks, their associated hairpin vortices, and the pockets with their associated pocket and hairpin vortices. The motions in both regions have unique phase relations which play an important role in their evolution and the resulting intensity of their interactions. In addition, the inner-outer region interactions are seen to be strong because typical eddies, microscale motions which can directly initiate the bursting process near a wall, are convected towards the wall by the response of the high speed outer region fluid to the presence of the large-scale motions. This interaction establishes a phasing between the inner and outer regions. The length and velocity scales of the typical eddy are used to remove the Reynolds number dependence of the stream wise fluctuations and the Reynolds stress in the fully turbulent portion of turbulent boundary layers over a wide range of Reynolds numbers

On the wave structure of the wall region of a turbulent boundary layer

1975 ◽  
Vol 70 (2) ◽  
pp. 229-250 ◽  
Author(s):  
Fritz H. Bark
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Reynolds Stress ◽  
Large Scale ◽  
Joint Probability Distribution ◽  
Wall Region ◽  
Time And Space ◽  
Mean Velocity ◽  
Model Calculations ◽  
Random System

Following the ideas suggested by Landahl (1967, 1975), some model calculations of the fluctuating velocity field in the wall region of a turbulent boundary layer have been carried out. It was assumed that the turbulent stresses are generated intermittently on small scales in time and space owing to bursting-type motions. The Reynolds-stress distribution during bursting periods and the mean velocity profile were assumed to be known, and the linear large-scale response to a random system of bursts was computed using an idealized model for the joint probability distribution in time and space of the occurrence of bursts. Computed energy spectra of the streamwise velocity fluctuations display scales in the spanwise and streamwise directions and time which are in good agreement with measurements by Morrison, Bullock & Kronauer (1971). However, the wavenumber band-widths of the computed spectra are narrower than those of the measured ones. This discrepancy is probably due to the crudeness of the model employed for the Reynolds stress during bursting.

Large-scale motion in the intermittent region of a turbulent boundary layer

1970 ◽  
Vol 41 (2) ◽  
pp. 283-325 ◽  
Author(s):  
Leslie S. G. Kovasznay ◽  
Valdis Kibens ◽  
Ron F. Blackwelder
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Scale ◽  
Cross Correlation ◽  
Turbulent Regime ◽  
Conditional Sampling ◽  
Correlation Data ◽  
Measuring Techniques ◽  
Conditional Averaging ◽  
Scale Motion

The outer intermittent region of a fully developed turbulent boundary layer with zero pressure gradient was extensively explored in the hope of shedding some light on the shape and motion of the interface separating the turbulent and non-turbulent regions as well as on the nature of the related large-scale eddies within the turbulent regime. Novel measuring techniques were devised, such as conditional sampling and conditional averaging, and others were turned to new uses, such as reorganizing in map form the space-time auto- and cross-correlation data involving both the U and V velocity components as well as I, the intermittency function. On the basis of the new experimental results, a conceptual model for the development of the interface and for the entrainment of new fluid is proposed.

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