Turbulent Flow in the Entry Region of a Rough Pipe

1974 ◽  
Vol 96 (1) ◽  
pp. 62-68 ◽  
Author(s):  
Jeng-Song Wang ◽  
J. P. Tullis
Keyword(s):  
Boundary Layer ◽  
Mathematical Model ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Boundary Layer Thickness ◽  
Static Pressure ◽  
Pressure Coefficient ◽  
Reynolds Numbers

The general characteristics of mean turbulent flow in the entry region of a rough pipe are discussed. A mathematical model is presented for predicting the development of boundary layer thickness, core velocity, and pressure coefficient. Measurements were made of static pressure and velocity profiles in a 12-in. dia pipe at Reynolds numbers between 7 × 105 and 3.7 × 106. Water was used as the fluid. Data are included on the length required for the wall shear stress to become constant, for the boundary layer to reach the pipe centerline and for the velocity profile to become fully developed.

A Superposition Analysis of the Turbulent Boundary Layer in an Adverse Pressure Gradient

1951 ◽  
Vol 18 (1) ◽  
pp. 95-100
Author(s):  
Donald Ross ◽  
J. M. Robertson
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Velocity Profile ◽  
Pressure Gradient ◽  
Adverse Pressure Gradient ◽  
Pressure Recovery ◽  
Stress Coefficient ◽  
Wall Shear

Abstract As an interim solution to the problem of the turbulent boundary layer in an adverse pressure gradient, a super-position method of analysis has been developed. In this method, the velocity profile is considered to be the result of two effects: the wall shear stress and the pressure recovery. These are superimposed, yielding an expression for the velocity profiles which approximate measured distributions. The theory also leads to a more reasonable expression for the wall shear-stress coefficient.

Turbulent Flow Over a Facing Step at Several Reynolds Numbers

2011 ◽  
Author(s):  
Jose A. Jimenez-Bernal ◽  
Adan Juarez-Montalvo ◽  
Claudia del C. Gutierrez-Torres ◽  
Juan G. Barbosa Saldan˜a ◽  
Luis F. Rodriguez-Jimenez
Keyword(s):  
Shear Stress ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Reynolds Numbers ◽  
Spatial Average ◽  
Vortex Center ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Image Velocimetry ◽  
Average Velocity Profile

An experimental study was performed over forward facing step (FFS). It was located within a transparent rectangular acrylic channel (1.4 m in length, 0.1 m in width and 0.02 m in height). The step is 0.01 m in height and 0.1 m in width, and was located 0.7 m downstream (fully developed region); a spanwise aspect ratio, w/h = 10 was used. The experiments were carried out using particle image velocimetry (PIV), which is a non intrusive experimental technique. The experimental water flow conditions include three Reynolds numbers based on the step height, Reh = 1124, 1404 and 1685. These flow conditions correspond to turbulent flow. Measurements were carried out in two zones; zone A begins at x = 8 cm (measured from the step base), and zone B starts at x = 0, y = 0, the visualization region corresponds to an area of 22.76 mm × 16.89 mm. 100 instantaneous velocity fields were obtained for each Reh. A temporal and spatial average was performed to obtain a velocity profile in zone A; likewise, the corresponding turbulence intensity and shear stress distribution were evaluated. The average velocity profile was evaluated for each Reh. Regarding the vortex center location, it was observed that as Reh increases, the y-direction coordinate moves towards bottom of wall channel. For zone B, it was also observed a reduction of the shear stress as Reh increases.

scholarly journals Secondary Flow Development Downstream of a Blade Endwall Corner

1994 ◽  
Author(s):  
A. Karim Abdulla-Altaii ◽  
Rishi S. Raj
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flat Plate ◽  
Secondary Flow ◽  
Total Pressure ◽  
Static Pressure ◽  
Horseshoe Vortex ◽  
Chord Length ◽  
Trailing Edge

The flow downstream of the corner formed by a blade and a flat plate was investigated experimentally. A single dominant horseshoe vortex was identified which persisted more than one chord length downstream of the blade trailing edge. A smaller and weaker corner vortex was also identified. It dissipated and ceased to exist by a downstream axial location of approximately 0.2C (C= chord length). There was no evidence of stress induced vortices in the region of this investigation. The secondary flow system redistributes the mean flow momentum and distorts total pressure profiles and contours. In planes parallel to the flat plate, total pressure values were found to be higher than the undisturbed two-dimensional boundary layer at that height. Surface static pressure was found to be at its maximum at the blade trailing edge location and it decreased in both the downstream and transverse directions. There was no significant static pressure variation in the spanwise direction. Downstream of the blade trailing edge, under the domain of the horseshoe vortex, local wall shear stress increased to values exceeding the values found in the undisturbed boundary layer at that axial location. However, a 20% reduction in the net wall skin-friction (wall shear stress integrated over the flat plate surface) was observed.

Near-Wall Measurements in Turbulent Boundary Layers Using Laser Doppler Anemometry

2002 ◽  
Author(s):  
T. Gunnar Johansson ◽  
Luciano Castillo
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Laser Doppler Anemometry ◽  
Reynolds Numbers ◽  
Mean Velocity ◽  
The Mean ◽  
Wall Shear ◽  
Near Wall

Near wall measurements have been performed in a zero pressure gradient turbulent boundary layer at low to moderate local Reynolds numbers using Laser-Doppler Anemometry in order to investigate how accurately the wall shear stress can be determined. Also, scaling problems are particularly difficult at low Reynolds numbers since they involve simultaneous influences of both inner and outer scales and this is most clearly observed in the near-wall region. In order to fully describe the zero pressure gradient turbulent boundary layer at low to moderate local Reynolds numbers it is necessary to accurately measure a number of quantities. These include the mean velocity and Reynolds stresses, and their spatial derivatives all the way down to the wall (y+∼1). Integral parameters that need to be measured are the wall shear stress and boundary layer thickness, particularly the momentum thickness. Problems with the measurement of field properties get worse close to a wall, and they get worse for increasing local Reynolds number. Three different approaches to measure the wall shear stress were examined. It was found that small measurement errors in the mean velocity close to the wall significantly reduced the accuracy in determining the wall shear stress by measuring the velocity gradient at the wall. The constant stress layer was found to be affected by the advection terms. However, it was found that taking the small pressure gradient into account and improving on the spatial resolution in the outer part of the boundary layer made the momentum integral method reliable.

Wall Shear Stress Inference From Two and Three-Dimensional Turbulent Boundary Layer Velocity Profiles

1973 ◽  
Vol 95 (1) ◽  
pp. 61-67 ◽  
Author(s):  
F. J. Pierce ◽  
B. B. Zimmerman
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Velocity Profile ◽  
Three Dimensional ◽  
Law Of The Wall ◽  
Layer Velocity ◽  
Wall Shear ◽  
Near Wall

A method is developed to infer a local wall shear stress from a two-dimensional turbulent boundary layer velocity profile using all near-wall data with the Spalding single formula law of the wall. The method is used to broaden the Clauser chart scheme by providing for the inclusion of data in the laminar sublayer and transition region, as well as the data in the fully turbulent near-wall flow region. For a skewed velocity profile typical of pressure driven three-dimensional turbulent boundary layer flows, the method is extended to infer a wall shear stress for a three-dimensional turbulent boundary layer. Either wall shear stress or shear velocity values are calculated for two different sets of three-dimensional experimental data, with good agreement found between calculated and experimental results.

Experimental Investigation of Flow Resistance and Wall Shear Stress in the Interior Subchannel of a Triangular Array of Parallel Rods

1979 ◽  
Vol 101 (4) ◽  
pp. 429-434 ◽  
Author(s):  
M. Fakory ◽  
N. Todreas
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Friction Factor ◽  
Static Pressure ◽  
Reynolds Numbers ◽  
Triangular Array ◽  
Flow Area ◽  
Static Pressure Distribution ◽  
The Common ◽  
Wall Shear

A simulated model of a triangular array of rods with pitch to diameter ratio of 1.1 with air flow was used to study the hydraulic parameters of the liquid metal fast breeder reactor (LMFBR) fuel geometry. The wall shear stress distribution, static pressure distribution, turbulence intensity, and friction factor were measured in the central subchannel from Reynolds numbers of 4 × 103 to 36 × 103. Our results show that the maximum wall shear stress occurs at the largest flow area, the static pressure is not uniform around the rod periphery, there is no detectable presence of secondary flow from the wall shear stress measurements, and the friction factor derived from the measured wall shear stress is less than the common friction factor derived from pressure drop measurement.

scholarly journals Study on the disturbance effect of pulsating flow and heat transfer in self-excited oscillation shear layer

2021 ◽  
pp. 347-347
Author(s):  
Gaoquan Hu ◽  
Zhaohui Wang ◽  
Yiwei Fan ◽  
Hongmei Yuan ◽  
Quanjie Gao
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Pulsating Flow ◽  
Transfer Efficiency ◽  
Heat Transfer Efficiency ◽  
Wall Shear

The fluid movement motion has an important influence on the evolution of the pulsating flow in the hot runner. Using the Large Eddy Simulation numerical method, the instantaneous velocity, wall shear stress, boundary layer thickness and Nu number of hot runner section under different structural parameters at an inlet pressure of 5000 Pa were studied. The research results showed that the backflow vortex can be formed in the hot runner, and the fluid at the axis center of hot runner can form a pulsating flow under the squeezing action of the backflow vortex. The pulsating flow had a strong disturbance effect on the fluid around the axis center and accelerated the heat exchange between the fluid around the axis center and the wall. The disturbance effect of pulsating flow gradually strengthened with the flow of the main flow to the downstream. When d2/d1 was 1-1.8, the wall shear stress first increased and then decreased, and the wall heat transfer efficiency first increased and then decreased. The maximum wall shear stress was 36.4Pa. When L/D was 0.45-0.65, the boundary layer thickness first decreased and then increased, and the heat transfer efficiency first increased and then decreased. The minimum boundary layer thickness was 0.392mm and the maximum Nu number was 138. When d2/d1=1.4 and L/D=0.55, the maximum comprehensive evaluation factor reached 1.241, and the heat transfer efficiency was increased by 24.1%.

A Second Turbulent Regime When a Fully Developed Axial Turbulent Flow Enters a Rotating Pipe

2016 ◽  
Author(s):  
Ferdinand-J. Cloos ◽  
Anna-L. Zimmermann ◽  
Peter F. Pelz
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Circumferential Velocity ◽  
Turbulent Regime ◽  
Self Similarity ◽  
Flow Number

When a fluid enters a rotating circular pipe a swirl boundary layer with thickness of δ̃s appears at the wall and interacts with the axial momentum boundary layer with thickness of δ̃. We investigate a turbulent flow applying Laser-Doppler-Anemometry to measure the circumferential velocity profile at the inlet of the rotating pipe. The measured swirl boundary layer thickness follows a power law taking Reynolds number and flow number into account. A combination of high Reynolds number, high flow number and axial position causes a transition of the swirl boundary layer development in the turbulent regime. At this combination, the swirl boundary layer thickness as well as the turbulence intensity increase and the latter yields a self-similarity. The circumferential velocity profile changes to a new presented self-similarity as well. We define the transition inlet length, where the transition appears and a stability map for the two regimes is given for the case of a fully developed axial turbulent flow enters the rotating pipe.

Effect of Tube Diameter on Wall Shear Stress Measurements Using Preston Tubes

2000 ◽  
Author(s):  
Sutardi ◽  
C. Y. Ching
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Reynolds Numbers ◽  
Tube Diameter ◽  
Momentum Thickness ◽  
Maximum Difference ◽  
Calibration Equation ◽  
Wall Shear ◽  
Outside Diameter

Abstract The effect of tube diameter (d) on wall shear stress (τw) measurements using Preston tubes has been investigated in a zero pressure gradient turbulent boundary layer. Five different outside diameter tubes of 1.46, 1.82, 3.23, 4.76 and 5.54 mm, corresponding to (d/δ) of 0.022, 0.027, 0.048, 0.071 and 0.082 were used to measure τw at Reynolds numbers based on momentum thickness (Rθ) of 2800 to 4100. The calibration curves of Patel (1965) and Bechert (1995) are both dependent on the tube diameter. The maximum difference in the τw measurements from the different tubes using Patel’s calibration is about 8%, while Bechert’s calibration gives a maximum difference of approximately 18%. Based on the present measurements, a new Preston tube calibration equation that is less sensitive to the tube diameter is proposed.

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