Velocity Distribution in Turbulent Flow

1970 ◽  
Vol 12 (6) ◽  
pp. 391-399 ◽  
Author(s):  
W. K. Allan
Keyword(s):  
Surface Roughness ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Flat Plate ◽  
Reynolds Numbers ◽  
Pressure Gradients ◽  
Roughness Effects ◽  
High Reynolds ◽  
Independent Effects ◽  
Good Agreement

A general equation for the velocity distribution in steady, incompressible, two-dimensional, turbulent flow is constructed by correction of the logarithmic velocity profile for the independent effects of pressure gradients and of surface roughness. Predicted characteristics of pipe flows, flat plate flows, and diffusing flows over smooth surfaces are found to be in good agreement with empirical data at high Reynolds numbers. Pipe flow data are used to evaluate surface roughness effects, and hence to describe flat plate flows and diffusing flows over rough surfaces.

Surface Roughness Effects on Circular Cylinders at High Reynolds Numbers

2002 ◽  
Author(s):  
M. Eaddy ◽  
W. H. Melbourne ◽  
J. Sheridan
Keyword(s):  
Surface Roughness ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Flow Induced Vibration ◽  
Roughness Effects ◽  
Vortex Induced Vibration ◽  
Smooth Cylinder ◽  
Lift Forces ◽  
High Reynolds ◽  
Effect Of Surface

The problem of flow-induced vibration has been studied extensively. However, much of this research has focused on the smooth cylinder to gain an understanding of the mechanisms that cause vortex-induced vibration. In this paper results of an investigation of the effect of surface roughness on the cross-wind forces are presented. Measurements of the sectional RMS fluctuating lift forces and the axial correlation of the pressures for Reynolds numbers from 1 × 105 to 1.4 × 106 are given. It was found that surface roughness significantly increased the axial correlation of the pressures to similar values found at high subcritical Reynolds numbers. There was little effect of the surface roughness on the sectional lift forces. The improved correlation of the vortex shedding means rough cylinders will be subject to larger cross-wind forces and an increased possibility of vortex-induced vibration compared to smooth cylinders.

Measurements of velocity distributions in the wake of a circular cylinder at low Reynolds numbers

1974 ◽  
Vol 65 (1) ◽  
pp. 97-112 ◽  
Author(s):  
Michio Nishioka ◽  
Hiroshi Sato
Keyword(s):  
Circular Cylinder ◽  
Velocity Distribution ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Velocity Measurements ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
High Reynolds ◽  
Good Agreement ◽  
Made In

Velocity measurements were made in the flow field behind a circular cylinder at Reynolds numbers from 10 to 80 and results compared with existing numerical solutions. Takami & Keller's solution for the velocity distribution in the wake shows good agreement at low Reynolds numbers and fair agreement at high Reynolds numbers. The drag coefficient of the cylinder and the size of the standing eddies behind the cylinder were also determined. They are compatible with existing experimental and numerical results. Details of the velocity distribution in the standing eddies are clarified.

Turbulent flow between counter-rotating concentric cylinders: a direct numerical simulation study

2008 ◽  
Vol 615 ◽  
pp. 371-399 ◽  
Author(s):  
S. DONG
Keyword(s):  
Turbulent Flow ◽  
Large Scale ◽  
Outer Cylinder ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Taylor Vortex ◽  
Small Scale ◽  
Mean Flow ◽  
Concentric Cylinders ◽  
High Reynolds

We report three-dimensional direct numerical simulations of the turbulent flow between counter-rotating concentric cylinders with a radius ratio 0.5. The inner- and outer-cylinder Reynolds numbers have the same magnitude, which ranges from 500 to 4000 in the simulations. We show that with the increase of Reynolds number, the prevailing structures in the flow are azimuthal vortices with scales much smaller than the cylinder gap. At high Reynolds numbers, while the instantaneous small-scale vortices permeate the entire domain, the large-scale Taylor vortex motions manifested by the time-averaged field do not penetrate a layer of fluid near the outer cylinder. Comparisons between the standard Taylor–Couette system (rotating inner cylinder, fixed outer cylinder) and the counter-rotating system demonstrate the profound effects of the Coriolis force on the mean flow and other statistical quantities. The dynamical and statistical features of the flow have been investigated in detail.

Velocity measurements close to the bed in a wave tank

1970 ◽  
Vol 42 (1) ◽  
pp. 111-123 ◽  
Author(s):  
J. F. A. Sleath
Keyword(s):  
Velocity Distribution ◽  
Vortex Formation ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
Velocity Measurements ◽  
Dominant Effect ◽  
Wave Tank ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Laminar Flow Conditions

Measurements of the velocity distribution close to the bed have been made under laminar flow conditions in a wave tank. The classical solution for the velocity distribution was found to be valid when the bed was smooth, but considerable deviations between theory and experiment were observed with beds of sand. It is suggested that these deviations were caused by vortex formation around the grains of sand. The similarity between the velocity profiles obtained in these tests and those reported by other writers under supposedly turbulent conditions suggests that even at high Reynolds numbers vortex formation may continue to be the dominant effect in oscillatory boundary layers of this sort.

On the Velocity Distribution of Turbulent Flow in Pipes and Channels of Constant Cross Section

1946 ◽  
Vol 13 (2) ◽  
pp. A85-A90
Author(s):  
Chi-Teh Wang
Keyword(s):  
Turbulent Flow ◽  
Velocity Distribution ◽  
Length Distribution ◽  
Critical Examination ◽  
Large Reynolds Number ◽  
Good Picture ◽  
Von Karman ◽  
Von Kármán ◽  
New Formula ◽  
Good Agreement

Abstract This paper follows the Prandtl conception of momentum transport and gives a critical examination of the so-called Prandtl-Nikuradse formula and the von Kármán formula for the velocity distribution of the turbulent flow in tubes or channels at large Reynolds number. It shows that both formulas would not give a good picture of the turbulent flow near the center of the conduit, and indeed they actually do not. A new formula for the velocity distribution is developed from a study of the mixing-length distribution across the section. This new formula checks quite well with the experiments and yields the same skin-friction formula as derived by von Kármán and Prandtl, which itself is in very good agreement with experiments.

Flow Control Over a Circular Cylinder Using Pulsed DBD Actuators

2012 ◽  
Author(s):  
William C. Schneck ◽  
Walter F. O’Brien
Keyword(s):  
Circular Cylinder ◽  
Flow Control ◽  
Gas Turbine ◽  
Electric Fields ◽  
Active Flow Control ◽  
Reynolds Numbers ◽  
Pressure Gradients ◽  
High Reynolds Numbers ◽  
Pulsed Dc ◽  
High Reynolds

Immersed bodies such as struts, vanes, and instrumentation probes in gas turbine flow systems will, except at the lowest of flow velocities, shed separated wakes. These wakes can have both upstream and downstream effects on the surrounding flow. In most applications, surrounding components are designed to be in the presence of a quasi-steady or at least non-variant flow field. The presence of unsteady wakes has both aerodynamic and structural consequences. Active flow control of wake generation can therefore be very valuable. One means to implement active flow control is by the use of plasma actuation. Plasma actuation is the use of strong electric fields to generate ionized gas that can be actuated and controlled using the electric fields. The controlling device can be based on AC, DC, or pulsed-DC actuation. The present research was conducted using pulsed-DC from a capacitive discharge power supply. The study demonstrates the applicability of, specifically, pulsed-DC plasma flow control of the flow on a circular cylinder at high Reynolds numbers. The circular cylinder was selected because its flow characteristics are related to gas turbine flowpath phenomena, and are well characterized. Further, the associated pressure gradients are some of the most severe encountered in fluid applications. The development of effective plasma actuators at high Reynolds numbers under the influence of severe pressure gradients is a necessary step toward developing useful actuators for gas turbine applications beyond laboratory use. The reported experiments were run at Reynolds numbers varying from 50,000 to 97,000, and utilizing various pulse frequencies. Further, the observed performance differences with varying electric field strengths are discussed for these Reynolds numbers. The results show that flow behaviors at high Reynolds numbers can be influenced by these types of actuators. The actuators were able to demonstrate a reduction in both wake width and momentum deficit.

Transient Heat Transfer for Turbulent Flow Over a Flat Plate of Appreciable Thermal Capacity and Containing Time-Dependent Heat Source

1967 ◽  
Vol 89 (4) ◽  
pp. 362-370 ◽  
Author(s):  
M. Soliman ◽  
H. A. Johnson
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Flat Plate ◽  
Reynolds Numbers ◽  
Thermal Capacity ◽  
High Flow ◽  
Time Dependent ◽  
Approximate Analysis ◽  
Heat Generation Rate ◽  
Theory And Experiments

An approximate analysis and experimental data are presented for the transient mean wall temperature of a flat plate of appreciable thermal capacity, heated by a step in the heat generation rate and cooled on both sides by a steady, incompressible turbulent flow with a Prandtl number of unity. Theory and experiments are in agreement over a range of Reynolds numbers 5 × 105 ≤ ReL ≤ 2 × 106. The experimental mean heat transfer coefficient is observed to go through a dip to a minimum before reaching the steady state. This dip is found to be due to the conjunction of a large wall thermal capacity and a sufficiently high flow velocity.

Effects of Roughness on Turbulent Flow in Microchannels and Minichannels

2008 ◽  
Author(s):  
Timothy P. Brackbill ◽  
Satish G. Kandlikar
Keyword(s):  
Experimental Study ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Roughness Parameter ◽  
Reynolds Numbers ◽  
Turbulent Regime ◽  
Roughness Effects ◽  
Relative Roughness ◽  
Roughness Elements ◽  
Moody Diagram

The effect of roughness ranging from smooth to 24% relative roughness on laminar flow has been examined in previous works by the authors. It was shown that using a constricted parameter, εFP, the laminar results were predicted well in the roughened channels ([1],[2],[3]). For the turbulent regime, Kandlikar et al. [1] proposed a modified Moody diagram by using the same set of constricted parameters, and using the modification of the Colebrook equation. A new roughness parameter εFP was shown to accurately portray the roughness effects encountered in laminar flow. In addition, a thorough look at defining surface roughness was given in Young et al. [4]. In this paper, the experimental study has been extended to cover the effects of different roughness features on pressure drop in turbulent flow and to verify the validity of the new parameter set in representing the resulting roughness effects. The range of relative roughness covered is from smooth to 10.38% relative roughness, with Reynolds numbers up to 15,000. It was found that using the same constricted parameters some unique characteristics were noted for turbulent flow over sawtooth roughness elements.

A Study on Turbulent Boundary Layers on a Smooth Flat Plate in an Open Channel

2001 ◽  
Vol 123 (2) ◽  
pp. 394-400 ◽  
Author(s):  
Ram Balachandar ◽  
D. Blakely ◽  
M. Tachie ◽  
G. Putz
Keyword(s):  
Flat Plate ◽  
Froude Number ◽  
Boundary Layers ◽  
Open Channel ◽  
Reynolds Numbers ◽  
Turbulent Boundary Layers ◽  
Wall Region ◽  
Mean Velocity ◽  
Number Range ◽  
High Reynolds

An experimental study was undertaken to investigate the characteristics of turbulent boundary layers developing on smooth flat plate in an open channel flow at moderately high Froude numbers (0.25<Fr<1.1) and low momentum thickness Reynolds numbers 800<Reθ<2900. The low range of Reynolds numbers and the high Froude number range make the study important, as most other studies of this type have been conducted at high Reynolds numbers and lower Froude numbers (∼0.1). Velocity measurements were carried out using a laser-Doppler anemometer equipped with a beam expansion device to enable measurements close to the wall region. The shear velocities were computed using the near-wall measurements in the viscous subregion. The variables of interest include the longitudinal mean velocity, the turbulence intensity, and the velocity skewness and flatness distributions across the boundary layer. The applicability of a constant Coles’ wake parameter (Π=0.55) to open channel flows has been discounted. The effect of the Froude number on the above parameters was also examined.

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