Evolution of a turbulent burst

1987 ◽  
Vol 53 (5) ◽  
pp. 1246-1252 ◽  
Author(s):  
G. I. Barenblatt ◽  
N. L. Galerkina ◽  
M. V. Luneva
Keyword(s):  
Turbulent Burst

Coherent Structure of the Turbulent Boundary Layer at Low and High Velocities

1982 ◽  
Author(s):  
V. Zakkay ◽  
V. Barra
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Phase Relationship ◽  
Lateral Spread ◽  
Flow Structures ◽  
Ordered Structure ◽  
Lateral Direction ◽  
Arrow Head ◽  
Simultaneous Measurements ◽  
Turbulent Burst

An attempt to obtain a description of the coherent, or quasi-ordered structure of the turbulent boundary layer in the lateral direction at low and high velocity is presented in this paper. Simultaneous measurements of velocity, wall pressure and wall shear fluctuations at U∞ = 10, 22.4 and 206 m/sec have been analyzed to obtain a description of the so-called “turbulent burst.” A conditional sampling scheme has been applied to the digitized fluctuations to identify the occurrence of bursts, and their spread thereof in the lateral direction. The results for the lateral spread of the “bursts” indicate that the events can be separated into two groups with opposite phase relationship across the lateral measurements and is thought to be an indication of “arrow-head” or “horseshoe” type shape. The angular spread of the “horseshoe” may be estimated and therefore the angle of each “leg” which makes the x axis may be determined. These results lead to the conclusions that the flow structures at high velocities tend to be very narrow and swept back at, or near the wall and are much wider and flatter away from the wall.

Turbulent burst around experimental spur dike

2011 ◽  
Vol 26 (4) ◽  
pp. 471-523 ◽  
Author(s):  
Jennifer DUAN ◽  
Li HE ◽  
Guangqian WANG ◽  
Xudong FU
Keyword(s):  
Spur Dike ◽  
Turbulent Burst

Model of the turbulent burst phenomenon - Predictions for eddy viscosity

AIAA Journal ◽  
1981 ◽  
Vol 19 (12) ◽  
pp. 1600-1602
Author(s):  
L. C. Thomas ◽  
M. B. Ibrahim
Keyword(s):  
Eddy Viscosity ◽  
Turbulent Burst

Analysis of Transitional and Fully Turbulent Plane Couette Flow

1983 ◽  
Vol 105 (3) ◽  
pp. 364-368 ◽  
Author(s):  
J. R. Missimer ◽  
L. C. Thomas
Keyword(s):  
Couette Flow ◽  
Flow Analysis ◽  
Wall Region ◽  
Turbulent Regime ◽  
Plane Couette Flow ◽  
Burst Frequency ◽  
Mean Velocity ◽  
The Mean ◽  
Turbulent Plane ◽  
Turbulent Burst

The two-dimensional, incompressible, fully-developed, turbulent plane Couette flow is a limiting case of circular Couette flow. As such, plane Couette flow analyses have been used in lubrication theory to analyze the lubrication flow in an unloaded journal bearings. A weakness of existing analyses, other than the turbulent burst analysis, is that they are not capable of characterizing the transitional turbulent regime. The objective of the proposed paper is to develop a model of the turbulent burst phenomenon for momentum in transitional turbulent and fully turbulent plane Couette flow. Model closure is obtained by specification of the mean turbulent burst frequency and, for moderate to high Reynolds numbers, by interfacing with classical eddy diffusivity models for the turbulent core. The analysis is shown to produce predictions for the mean velocity profile and friction factor that are in good agreement with published experimental data for transitional turbulent and fully turbulent flow. This approach to modeling the wall region involves a minimum level of empiricism and provides a fundamental basis for generalization. The use of the present analysis extends the applicability of plane Couette flow analysis in lubrication problems to the transitional turbulent regime.

scholarly journals On the possibility of wave-induced chaos in a sheared, stably stratified fluid layer

1994 ◽  
Vol 1 (4) ◽  
pp. 219-223 ◽  
Author(s):  
W. B. Zimmermann ◽  
M. G. Velarde
Keyword(s):  
Reynolds Number ◽  
Gravity Waves ◽  
Thermal Energy ◽  
Richardson Number ◽  
Fluid Layer ◽  
Fluid Velocity ◽  
Internal Gravity Waves ◽  
Temperature Wave ◽  
Perturbation Scheme ◽  
Turbulent Burst

Abstract. Shear flow in a stable stratification provides a waveguide for internal gravity waves. In the inviscid approximation, internal gravity waves are known to be unstable below a threshold in Richardson number. However, in a viscous fluid, at low enough Reynolds number, this threshold recedes to Ri = 0. Nevertheless, even the slightest viscosity strongly damps internal gravity waves when the Richardson number is small (shear forces dominate buoyant forces). In this paper we address the dynamics that approximately govern wave propagation when the Richardson number is small and the fluid is viscous. When Ri << 1, to a first approximation, the transport equations for thermal energy and momentum decouple. Thus, a large amplitude temperature wave then has little effect on the fluid velocity. Under such conditions in the atmosphere, a small amplitude "turbulent burst" is observed, transporting momentum rapidly and seemingly randomly. A regular perturbation scheme from a base state of a passing temperature wave and no velocity disturbance is developed here. Small thermal energy convection-momentum transport coupling is taken into account. The elements of forcing, wave dispersion, (turbulent) dissipation under strong shearing, and weak nonlinearity lead to this dynamical equation for the amplitude A of the turbulent burst in velocity: Aξ = λ1A + λ2Aξξ + λ3Aξξξ + λ4AAξ + b(ξ) where ξ is the coordinate of the rest frame of the passing temperature wave whose horizontal profile is b(ξ). The parameters λi are constants that depend on the Reynolds number. The above dynamical system is know to have limit cycle and chaotic attrators when forcing is sinusoidal and wave attenuation negligible.

Mean Velocity, Reynolds Shear Stress, and Fluctuations of Velocity and Pressure Due to Log Laws in a Turbulent Boundary Layer and Origin Offset by Prandtl Transposition Theorem

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Noor Afzal ◽  
Abu Seena
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Turbulent Boundary Layer ◽  
Skin Friction ◽  
Velocity Vector ◽  
Reynolds Shear Stress ◽  
Mean Velocity ◽  
Time Period ◽  
Log Law ◽  
Turbulent Burst

The maxima of Reynolds shear stress and turbulent burst mean period time are crucial points in the intermediate region (termed as mesolayer) for large Reynolds numbers. The three layers (inner, meso, and outer) in a turbulent boundary layer have been analyzed from open equations of turbulent motion, independent of any closure model like eddy viscosity or mixing length, etc. Little above (or below not considered here) the critical point, the matching of mesolayer predicts the log law velocity, peak of Reynolds shear stress domain, and turbulent burst time period. The instantaneous velocity vector after subtraction of mean velocity vector yields the velocity fluctuation vector, also governed by log law. The static pressure fluctuation p′ also predicts log laws in the inner, outer, and mesolayer. The relationship between u′/Ue with u/Ue from structure of turbulent boundary layer is presented in inner, meso, and outer layers. The turbulent bursting time period has been shown to scale with the mesolayer time scale; and Taylor micro time scale; both have been shown to be equivalent in the mesolayer. The shape factor in a turbulent boundary layer shows linear behavior with nondimensional mesolayer length scale. It is shown that the Prandtl transposition (PT) theorem connects the velocity of normal coordinate y with s offset to y + a, then the turbulent velocity profile vector and pressure fluctuation log laws are altered; but skin friction log law, based on outer velocity Ue, remains independent of a the offset of origin. But if skin friction log law is based on bulk average velocity Ub, then skin friction log law depends on a, the offset of origin. These predictions are supported by experimental and direct numerical simulation (DNS) data.

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