Measurements of Wall Shear Stress in Axial Flow in a Square Lattice Rectangular Rod Bundle

1986 ◽  
Vol 108 (2) ◽  
pp. 166-172 ◽  
Author(s):  
M. Abdelghany ◽  
R. Eichhorn
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Axial Flow ◽  
Side Wall ◽  
Diameter Ratio ◽  
Square Lattice ◽  
Local Shear ◽  
Wall Shear ◽  
Hot Film ◽  
Local Shear Stress

Hot film probe measurements of the distribution of the wall shear stress were made for axial flow along a rectangular 3 × 6 array of rods with a pitch to diameter ratio, P/D = 4/3, and a wall to diameter ratio, W/D = 2/3. Measurements were performed on rods at several locations and on two duct side walls at a position 62 hydraulic diameters from the entrance. Local shear stress maxima occur near the largest subchannel flow areas with the lowest maximum local shear stress on rods nearest the sidewalls. Maximum to the minimum shear stress ratio on an individual rod is largest for the corner rod. Side wall maximum local shear stress occurs in the first wall subchannel. Overall friction factors calculated from the wall shear stress measurements agree with those calculated from pressure drop data.

Roughness Influence on Turbulent Flow Through Annular Seals

1994 ◽  
Vol 116 (2) ◽  
pp. 321-328 ◽  
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.

Measurement of wall shear stress in physiological pulsatile flows by flush-mounted hot film anemometry

1988 ◽  
Vol 16 (2) ◽  
pp. 235-238
Author(s):  
Subhashis Nandy ◽  
Alex Yefim Bekker ◽  
Gregory Allen Winchell ◽  
John Francis O'Riordan
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulsatile Flows ◽  
Wall Shear ◽  
Hot Film ◽  
Hot Film Anemometry

215 Development of micro-fabricated hot-film sensor by MEMS and study on its validation of the wall shear stress fluctuation measurement

2014 ◽  
Vol 2014.63 (0) ◽  
pp. _215-1_-_215-2_
Author(s):  
Takuya SAWADA ◽  
Osamu TERASHIMA ◽  
Yasuhiko SAKAI ◽  
Kouji Nagata ◽  
Mitsuhiro SHIKIDA ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Film Sensor ◽  
Stress Fluctuation ◽  
Wall Shear ◽  
Hot Film ◽  
Fluctuation Measurement ◽  
Hot Film Sensor

Two-component hot-film probe for measurements of wall shear stress

1993 ◽  
Vol 15 (6) ◽  
pp. 380-384 ◽  
Author(s):  
B. M. Sumer ◽  
M. M. Arnskov ◽  
N. Christiansen ◽  
F. E. Jørgensen
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Two Component ◽  
Wall Shear ◽  
Hot Film

Direct simulation of turbulent swept flow over a wire in a channel

2010 ◽  
Vol 651 ◽  
pp. 165-209 ◽  
Author(s):  
R. RANJAN ◽  
C. PANTANO ◽  
P. FISCHER
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Axial Flow ◽  
Separated Flow ◽  
Mean Flow ◽  
Sweep Angle ◽  
Wire Axis ◽  
The Mean ◽  
The Wire ◽  
Wall Shear

Turbulent swept flow over a cylindrical wire placed on a wall of a channel is investigated using direct numerical simulations. This geometry is a model of the flow through the wire-wrapped fuel pins, the heat exchanger, typical of many nuclear reactor designs. Mean flow along and across the wire axis is imposed, leading to the formation of separated flow regions. The Reynolds number based on the bulk velocity along the wire axis direction and the channel half height is 5400 and four cases are simulated with different flowrates across the wire. This configuration is topologically similar to backward-facing steps or slots with swept flow, except that the dominant flow is along the obstacle axis in the present study and the crossflow is smaller than the axial flow, i.e. the sweep angle is large. Mean velocities, turbulence statistics, wall shear stress and instantaneous flow structures are investigated. Particular attention is devoted to the statistics of the shear stress on the walls of the channel and the wire in the recirculation zone. The flow around the mean reattachment region, at the termination of the recirculating bubble, does not exhibit the typical decay of the mean shear stress observed in classical backward-facing step flows owing to the presence of a strong axial flow. The evolution of the mean wall shear stress angle after reattachment indicates that the flow recovers towards equilibrium at a rather slow rate, which decreases with sweep angle. Finally, the database is analysed to estimate resolution requirements, in particular around the recirculation zones, for large-eddy simulations. This has implications in more complete geometrical models of a wire-wrapped assembly, involving hundreds of fuel pins, where only turbulence modelling can be afforded computationally.

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