Turbulent Flow in an Annulus

1967 ◽  
Vol 89 (1) ◽  
pp. 25-31 ◽  
Author(s):  
S. Levy
Keyword(s):  
Turbulent Flow ◽  
Tube Wall ◽  
Eddy Diffusivity ◽  
Test Results ◽  
Core Tube ◽  
The Core ◽  
Roughened Surface ◽  
Shear Mixing ◽  
Fully Developed Turbulent Flow ◽  
Good Agreement

Equations describing fully developed turbulent flow in an annulus are derived. They are based upon Reichardt’s expression for the eddy diffusivity of momentum, and they assume that the velocity profiles starting from the core tube wall and the outer tube wall have the same velocity and eddy diffusivity at the plane of zero shear. The predicted location of the plane of zero shear, mixing length, eddy diffusivity, velocity distribution, and friction factor are compared to available data and are found to give good agreement with the test results. Potential extension of the proposed method to more complex geometries is illustrated by considering the case of flow in an annulus with one artificially roughened surface.

On the Use of the Preston Tube in Concentric Annuli

1967 ◽  
Vol 71 (673) ◽  
pp. 47-49 ◽  
Author(s):  
Alan Quarmby
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Skin Friction ◽  
Radius Ratio ◽  
Experimental Results ◽  
Core Tube ◽  
Reasonable Range ◽  
Fully Developed Turbulent Flow ◽  
Good Agreement

Experimental results are presented of the measurement of skin friction in fully developed turbulent flow in concentric annuli using Preston tubes situated on the inner and outer annular surfaces. Both Preston's calibration and Patel's calibration were used to evaluate the results. It was found that the latter gave excellent results. Several radius ratios were investigated with a reasonable range of the annulus Reynolds number. The good agreement was not affected by radius ratio or smallness of core tube within the range of these parameters investigated here.

Prediction of Cavitation Inception Within Regions of Flow Separation

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Experimental Data ◽  
Turbulent Flow ◽  
Flow Separation ◽  
Computational Method ◽  
Average Flow ◽  
Cavitation Inception ◽  
The Core ◽  
Good Agreement

Cavitation within regions of flow separation appears in drifting vortices. A two-part computational method is employed for prediction of cavitation inception number there. The first part is an analysis of the average flow in separation regions without consideration of an impact of vortices. The second part is an analysis of equilibrium of the bubble within the core of a vortex located in the turbulent flow of known average characteristics. Computed cavitation inception numbers for axisymmetric flows are in the good agreement with the known experimental data.

scholarly journals Numerical Study of Turbulent Secondary Flows in Curved Ducts

1990 ◽  
Vol 112 (2) ◽  
pp. 205-211 ◽  
Author(s):  
N. Hur ◽  
S. Thangam ◽  
C. G. Speziale
Keyword(s):  
Experimental Data ◽  
Turbulent Flow ◽  
Secondary Flow ◽  
Cross Section ◽  
Numerical Study ◽  
Secondary Flows ◽  
Fully Developed Turbulent Flow ◽  
Volume Method ◽  
Curved Ducts ◽  
Good Agreement

The pressure driven, fully developed turbulent flow of an incompressible viscous fluid in curved ducts of square cross-section is studied numerically by making use of a finite volume method. A nonlinear K -1 model is used to represent the turbulence. The results for both straight and curved ducts are presented. For the case of fully developed turbulent flow in straight ducts, the secondary flow is characterized by an eight-vortex structure for which the computed flowfield is shown to be in good agreement with available experimental data. The introduction of moderate curvature is shown to cause a substantial increase in the strength of the secondary flow and to change the secondary flow pattern to either a double-vortex or a four-vortex configuration.

Axisymmetric turbulent mass transfer in a circular tube

1969 ◽  
Vol 38 (3) ◽  
pp. 433-455 ◽  
Author(s):  
Alan Quarmby ◽  
R. K. Anand
Keyword(s):  
Mass Transfer ◽  
Velocity Profile ◽  
Circular Tube ◽  
Eddy Diffusivity ◽  
Reynolds Numbers ◽  
Eddy Diffusivities ◽  
Direct Measurements ◽  
Fluid Properties ◽  
Fully Developed Turbulent Flow ◽  
Good Agreement

Solutions of the diffusion equation are obtained for mass transfer in a fully developed turbulent flow in a plain circular tube in two axisymmetric situations. The cases studied are a point source positioned at the centre of the tube and a ring source in the tube wall in which there is a uniform mass flux along a short length of the tube. The purpose of the work is to establish the correctness of the descriptions of the velocity profile and radial eddy diffusivities of mass and momentum in order to provide a firm base from which consideration of the non-axisymmetric situation could proceed.The turbulent velocity profile is deduced from a two-part model based on a sublayer profile and the Von Kármán similarity hypothesis. The radial eddy diffusivity of momentum is described by an expression due to Reichardt and Van Driest and from this the radial eddy diffusivity of mass as a function of radius is obtained by use of a ratio which takes account of fluid properties and the value of the radial eddy diffusivity.The analysis is substantiated by experiments carried out with nitrous oxide, Schmidt number = 0·77, for Reynolds numbers from 20,000 to 130,000. The concentration profiles measured at several axial positions downstream from the source are in good agreement with the analytical solutions in both cases. Direct measurements of the eddy diffusivity of mass and momentum were obtained as added confirmation and also gave good agreement with the theory.

Computation of Annular, Turbulent Flow With Rotating Core Tube

1976 ◽  
Vol 98 (4) ◽  
pp. 753-758 ◽  
Author(s):  
B. I. Sharma ◽  
B. E. Launder ◽  
C. J. Scott
Keyword(s):  
Experimental Data ◽  
Turbulent Flow ◽  
Transport Model ◽  
Rotational Velocity ◽  
Numerical Procedure ◽  
Mean Flow ◽  
Core Tube ◽  
The Core ◽  
Numerical Predictions ◽  
Bulk Flow Rate

Numerical predictions are presented of fully-developed turbulent flow through a concentric annulus in which the core tube rotates about its axis. Comparisons are drawn with the extensive experimental data of Kuzay and Scott [1] which span Reynolds numbers from 1.7 to 104 to 6.5 × 104 and with rotational speeds of the core tube varying from zero to nearly 2.8 times the bulk axial velocity. Predictions have been obtained by means of an adapted version of the Patankar-Spalding [5], numerical procedure employing, as turbulent transport model, the version of the mixing length hypothesis applied by Koosinlin, Sharma and Launder [2] to flows on spinning cones and cylinders. Agreement with experiment is generally close at the higher relative swirl rates but the predictions of the swirling velocity profile deteriorate as the bulk flow rate is increased. The discrepancy seems to be due to the experimental data requiring a greater development length as the magnitude of the rotational velocity is reduced relative to that of the mean flow. Demonstrative developing-flow predictions are provided which exhibit closer agreement with the experimental data.

scholarly journals Spine Examination during COVID-19 Pandemic via Video Consultation

2021 ◽  
Author(s):  
Tom Jansen ◽  
Martin Gathen ◽  
Amadeo Touet ◽  
Hans Goost ◽  
Dieter Christian Wirtz ◽  
...  
Keyword(s):  
Pain Intensity ◽  
Range Of Motion ◽  
Test Results ◽  
Risk Of Infection ◽  
Face To Face ◽  
Reliable Tool ◽  
Provocation Tests ◽  
Active Range Of Motion ◽  
Video Consultation ◽  
Good Agreement

Abstract Introduction During the current COVID-19 pandemic video consultations are increasingly common in order to minimize the risk of infection for staff and patients. The aim of this study was to evaluate the feasibility of a spine examination via video. Methods A total of 43 patients were recruited. Each participant underwent a video-based (VB) and a conventional face-to-face (FTF) spine examination. Pain intensity, active range of motion, inspection, a neurophysiologic basic exam and provocations tests were evaluated using video-based and face-to-face methods. Results The intra-rater reliability (IRR) was measured between both examinations. Good to very good IRR values were obtained in inspection (Kappa between 0,752 und 0,944), active range of motion and basic neurophysiological examination (Kappa between 0,659 und 0,969). Only moderate matches were found in specific provocation tests (Kappa between 0,407 und 0,938). A video-based spine examination is a reliable tool for measuring pain intensity, active range of motion and a basic neurophysiologic exam. Conclusion A basic spine examination during a video consultation is possible. A good agreement of the test results between video-based and face-to-face examination could be found.

Design of combined brake system for light weight scooters

2021 ◽  
pp. 095440702110240
Author(s):  
Yuan-Ting Lin ◽  
Chyuan-Yow Tseng ◽  
Jao-Hwa Kuang ◽  
Yeong-Maw Hwang
Keyword(s):  
Ride Comfort ◽  
Brake System ◽  
Force Distribution ◽  
Test Results ◽  
Systematic Method ◽  
Braking Performance ◽  
Evaluation Indexes ◽  
Low Costs ◽  
Braking Force ◽  
Good Agreement

The combined brake system (CBS) is a mechanism that links the front and rear brakes for scooters. For two-wheeled scooters, a CBS with appropriate braking force distribution can reduce the risk of crashing accidents due to insufficient driving proficiency. The design of the braking force distribution for a CBS is challenging to the designer because it has to fulfill many requirements such as braking performance, ride comfort, reliability, and low costs. This paper proposes a systematic method to optimize the parameters of CBS. The evaluation indexes for the design are first discussed. The steps to determine the critical parameter to meet the indexes and a method to predict braking performance are developed. Finally, driving tests are carried out to verify the effectiveness of the proposed method. Experimental results showed that the deceleration of the tested scooter equipped with the designed CBS achieves an average mean fully developed deceleration (MFDD) of 5.246 m/s2, higher than the homologation requirement. Furthermore, the proposed method’s prediction of braking performance is in good agreement with the test results, with errors <1%.

scholarly journals Fully developed turbulent flow in a square duct with a rough wall.

1987 ◽  
Vol 53 (492) ◽  
pp. 2370-2376 ◽  
Author(s):  
Hideomi FUJITA ◽  
Hajime YOKOSAWA ◽  
Masafumi HIROTA ◽  
Satoru NISHIGAKI
Keyword(s):  
Turbulent Flow ◽  
Rough Wall ◽  
Square Duct ◽  
Fully Developed Turbulent Flow
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