Flow Pattern and Frictional Losses in Pulsating Pipe Flow : Part 7 Wall Shear Stress in a Turbulent Flow

This study describes turbulent flow in a semifilled pipe with a focus on its secondary currents. To the authors’ knowledge, we provide the first highly resolved data-set for semifilled-pipe flow using direct numerical simulation. The flow parameters range from $Re_\tau =115$ , just maintaining turbulence, to moderate turbulent flow at $Re_\tau =460$ . Some of the main flow characteristics are in line with previously published results from experiments, such as the velocity-dip phenomenon, the main secondary flow and the qualitative distribution of the Reynolds stresses in the core of the flow. We observe some flow phenomena which have not yet been reported in the literature so far for this type of flow. Among those is the inner secondary cell in the mixed corner between the free surface and the pipe's wall, which plays a major role in the distribution of the wall shear stress along the perimeter. We observe that the position and extension of the inner vortex scale with the wall shear stress and those of the outer vortex scale with outer variables. For the first time, we present and discuss distributions of the complete Reynolds stress tensor and its anisotropy which gives rise to the generation of mean streamwise vorticity in a small region in the mixed corners of the pipe. Mean secondary kinetic energy, however, is generated at the free surface around the stagnation point between the inner and outer vortices. This generation mechanism is in line with a vortex dynamics mechanism proposed in the literature.

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Preston-Static Tubes for the Measurement of Wall Shear Stress

Journal of Fluids Engineering ◽

10.1115/1.2910326 ◽

1994 ◽

Vol 116 (3) ◽

pp. 645-649 ◽

Cited By ~ 5

Author(s):

Josef Daniel Ackerman ◽

Louis Wong ◽

C. Ross Ethier ◽

D. Grant Allen ◽

Jan K. Spelt

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Convenient Method ◽

Pipe Flow ◽

Total Pressure ◽

Static Pressure ◽

Shear Stresses ◽

Streamline Curvature ◽

Syringe Needle ◽

Wall Shear

We present a Preston tube device that combines both total and static pressure readings for the measurement of wall shear stress. As such, the device facilitates the measurement of wall shear stress under conditions where there is streamline curvature and/or over surfaces on which it is difficult to either manufacture an array of static-pressure taps or to position a single tap. Our “Preston-static” device is easily and conveniently constructed from commercially available regular and side-bored syringe needles. The pressure difference between the total pressure measured in the regular syringe needle and the static pressure measured in the side-bored one is used to determine the wall shear stress. Wall shear stresses measured in pipe flow were consistent with independently determined values and values obtained using a conventional Preston tube. These results indicate that Preston-static tubes provide a reliable and convenient method of measuring wall shear stress.

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Wall-Shear Stress Assessment in Zero-Pressure Gradient Turbulent Flow using MPS

Springer Proceedings Physics - Advances in Turbulence XI ◽

10.1007/978-3-540-72604-3_29 ◽

2008 ◽

pp. 97-99

Author(s):

S. Groβe ◽

W. Schröder

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Turbulent Flow ◽

Pressure Gradient ◽

Stress Assessment ◽

Wall Shear

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Roughness Influence on Turbulent Flow Through Annular Seals

Journal of Tribology ◽

10.1115/1.2927219 ◽

1994 ◽

Vol 116 (2) ◽

pp. 321-328 ◽

Cited By ~ 14

Author(s):

Victor Lucas ◽

Sterian Danaila ◽

Olivier Bonneau ◽

Jean Freˆne

Keyword(s):

Surface Roughness ◽

Shear Stress ◽

Wall Shear Stress ◽

Turbulent Flow ◽

Dynamic Characteristics ◽

Reynolds Equation ◽

Mixing Length ◽

Local Shear ◽

Wall Shear ◽

Local Shear Stress

This paper deals with an analysis of turbulent flow in annular seals with rough surfaces. In this approach, our objectives are to develop a model of turbulence including surface roughness and to quantify the influence of surface roughness on turbulent flow. In this paper, in order to simplify the analysis, the inertial effects are neglected. These effects will be taken into account in a subsequent work. Consequently, this study is based on the solution of Reynolds equation. Turbulent flow is solved using Prandtl’s turbulent model with Van Driest’s mixing length expression. In Van Driest’s model, the mixing length depends on wall shear stress. However there are many numerical problems in evaluating this wall shear stress. Therefore, the goal of this work has been to use the local shear stress in the Van Driest’s model. This derived from the work of Elrod and Ng concerning Reichardt’s mixing length. The mixing length expression is then modified to introduce roughness effects. Then, the momentum equations are solved to evaluate the circumferential and axial velocity distributions as well as the turbulent viscosity μ1 (Boussinesq’s hypothesis) within the film. The coefficients of turbulence kx and kz, occurring in the generalized Reynolds’ equation, are then calculated as functions of the flow parameters. Reynolds’ equation is solved by using a finite centered difference method. Dynamic characteristics are calculated by exciting the system numerically, with displacement and velocity perturbations. The model of Van Driest using local shear stress and function of roughness has been compared (for smooth seals) to the Elrod and Ng theory. Some numerical results of the static and dynamic characteristics of a rough seal (with the same roughness on the rotor as on the stator) are presented. These results show the influence of roughness on the dynamic behavior of the shaft.

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