scholarly journals Velocity Profile and Turbulence Structure Measurement Corrections for Sediment Transport-Induced Water-Worked Bed

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 86 ◽  
Author(s):  
Jaan H. Pu
Keyword(s):  
Experimental Data ◽  
Sediment Transport ◽  
Velocity Profile ◽  
Reynolds Stress ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Turbulence Structure ◽  
Measured Velocity ◽  
Rough Bed ◽  
Velocity Turbulence

When using point measurement for environmental or sediment laden flows, there is well-recognised risk for not having aligned measurements that causes misinterpretation of the measured velocity data. In reality, these kinds of mismeasurement mainly happen due to the misinterpretation of bed orientation caused by the complexity of its determination in natural flows, especially in bedload laden or rough bed flows. This study proposes a novel bed realignment method to improve the measured data benchmarking by three-dimensional (3D) bed profile orientation and implemented it into different sets of experimental data. More specifically, the effects of realignment on velocity profile and streamwise turbulence structure measurements were investigated. The proposed technique was tested against experimental data collected over a water-worked and an experimentally arranged well-packed beds. Different from the well-packed rough bed, the water-worked bed has been generated after long sediment transport and settling and hence can be used to verify the proposed bed-alignment technique thoroughly. During the flow analysis, the corrected velocity, turbulence intensity and Reynolds stress profiles were compared to the theoretical logarithmic law, exponential law and linear gravity (universal Reynolds stress distribution) profiles, respectively. It has been observed that the proposed method has improved the agreement of the measured velocity and turbulence structure data with their actual theoretical profiles, particularly in the near-bed region (where the ratio of the flow measurement vertical distance to the total water depth, z/h, is limited to ≤0.4).

An Axial Compressor End-Wall Boundary Layer Calculation Method

1979 ◽  
Vol 101 (2) ◽  
pp. 233-245 ◽  
Author(s):  
J. De Ruyck ◽  
C. Hirsch ◽  
P. Kool
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Velocity Profile ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Wall Region ◽  
Wall Boundary Layer ◽  
Wall Boundary ◽  
End Wall

An axial compressor end-wall boundary layer theory which requires the introduction of three-dimensional velocity profile models is described. The method is based on pitch-averaged boundary layer equations and contains blade force-defect terms for which a new expression in function of transverse momentum thickness is introduced. In presence of tip clearance a component of the defect force proportional to the clearance over blade height ratio is also introduced. In this way two constants enter the model. It is also shown that all three-dimensional velocity profile models present inherent limitations with regard to the range of boundary layer momentum thicknesses they are able to represent. Therefore a new heuristic velocity profile model is introduced, giving higher flexibility. The end-wall boundary layer calculation allows a correction of the efficiency due to end-wall losses as well as calculation of blockage. The two constants entering the model are calibrated and compared with experimental data allowing a good prediction of overall efficiency including clearance effects and aspect ratio. Besides, the method allows a prediction of radial distribution of velocities and flow angles including the end-wall region and examples are shown compared to experimental data.

Computation of Three-Dimensional Compressible Flow From a Rectangular Nozzle With Delta Tabs

1999 ◽  
Vol 121 (2) ◽  
pp. 235-242 ◽  
Author(s):  
D. R. Reddy ◽  
C. J. Steffen ◽  
K. B. M. Q. Zaman
Keyword(s):  
Experimental Data ◽  
Nozzle Exit ◽  
Flow Analysis ◽  
Supersonic Jet ◽  
Three Dimensional ◽  
Streamwise Velocity ◽  
Navier Stokes ◽  
Rectangular Nozzle ◽  
Flow Configurations ◽  
Subsonic Jet

A three-dimensional viscous flow analysis is performed using a time-marching Reynolds-averaged Navier-Stokes code for a 3:1 rectangular nozzle with two delta tabs located at the nozzle exit plane to enhance mixing. Two flow configurations, a subsonic jet case and a supersonic jet case using the same tab configuration, which were previously studied experimentally, are computed and compared with the experimental data. The experimental data include streamwise velocity and vorticity distributions for the subsonic case, and Mach number distributions for the supersonic case, at various axial locations downstream of the nozzle exit. The computational results show very good agreement with the experimental data. In addition, the effect of compressibility on vorticity dynamics is examined by comparing the vorticity contours of the subsonic jet case with those of the supersonic jet case which were not measured in the experiment.

Simultaneous flow visualization and Reynolds-stress measurement in a turbulent boundary layer

1986 ◽  
Vol 163 ◽  
pp. 459-478 ◽  
Author(s):  
A. M. Talmon ◽  
J. M. G. Kunen ◽  
G. Ooms
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flow Visualization ◽  
Reynolds Stress ◽  
Stress Measurement ◽  
Three Dimensional ◽  
Time Dependent ◽  
Flow Structures ◽  
Wall Region ◽  
Measured Velocity

Flow visualization and Reynolds-stress measurement were combined in an investigation of a turbulent boundary layer in a water channel. Hydrogen bubbles were used to visualize the flow; a laser-Doppler anemometer capable of measuring two velocity components was applied to measure the instantaneous value of the Reynolds stress. Owing to the three-dimensional, time-dependent character of the flow it was rather difficult to identify flow structures from measured velocity signals, especially at larger distances from the wall. Despite this difficulty a method based on the instantaneous value of the Reynolds stress could be developed for detecting bursts in the wall region of the boundary layer. By this method the three-dimensional, time-dependent character of the flow is taken into account by attributing to the same burst ejections occurring successively with very short time intervals. This identification procedure is based on a comparison on a one-to-one basis between visualized flow structures and measured values of the Reynolds stress. The detected bursts were found to make a considerable contribution to the momentum transport in the boundary layer.

Numerical Study of Nonreacting Gas Turbine Combustor Swirl Flow Using Reynolds Stress Model

2003 ◽  
Vol 125 (3) ◽  
pp. 804-811 ◽  
Author(s):  
S. L. Yang ◽  
Y. K. Siow ◽  
B. D. Peschke ◽  
R. R. Tacina
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Reynolds Stress Model ◽  
Swirl Flow ◽  
High Degree

This paper presents recent research on the use of a Reynolds stress turbulence model (RSTM) for three-dimensional flowfield simulation inside gas turbine combustors. It intends to show the motivations for using the RSTM in engine flow simulation, to present a further validation of the RSTM implementation in the KIVA code using the available experimental data, and to provide comparisons between RSTM and k-ε turbulence model results for chemically nonreacting swirling flows. The results show that, for high-degree swirl flow, the RSTM can provide predictions in favorable agreement with the experimental data, and that the RSTM predicts recirculations and high velocity gradients better than does the k-ε turbulence model. The results also indicate that the choice of swirler has a significant influence on the structure of the combustor flowfield.

Computation of 3-D Compressible Flow From a Rectangular Nozzle With Delta Tabs

1997 ◽  
Author(s):  
Dhanireddy R. Reddy ◽  
Christopher J. Steffen ◽  
Khairul B. M. Q. Zaman
Keyword(s):  
Experimental Data ◽  
Nozzle Exit ◽  
Flow Analysis ◽  
Supersonic Jet ◽  
Three Dimensional ◽  
Streamwise Velocity ◽  
Navier Stokes ◽  
Rectangular Nozzle ◽  
Flow Configurations ◽  
Subsonic Jet

A three-dimensional viscous flow analysis is performed using a time-marching Reynolds-averaged Navier-Stokes code for a 3:1 rectangular nozzle with two delta tabs located at the nozzle exit plane to enhance mixing. Two flow configurations, a subsonic jet case and a supersonic jet case using the same tab configuration which were previously studied experimentally, are computed and compared with the experimental data. The experimental data include streamwise velocity and vorticity distributions for the subsonic case, and Mach number distributions for the supersonic case, at various axial locations downstream of the nozzle exit. The computational results show very good agreement with the experimental data. In addition, the effect of compressibility on vorticity dynamics are examined by comparing the vorticity contours of the subsonic jet case with those of the supersonic jet case which were not measured in the experiment.

scholarly journals Analytical Formula for the Mean Velocity Profile in a Pipe Derived on the Basis of a Spatial Polynomial Vorticity Distribution

Water ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1372
Author(s):  
Jaroslav Štigler
Keyword(s):  
Experimental Data ◽  
Velocity Profile ◽  
Flow Analysis ◽  
Analytical Formula ◽  
Empirical Formulas ◽  
Mean Velocity ◽  
Vorticity Distribution ◽  
Wide Range ◽  
The Mean ◽  
Free Parameters

The derivation of the mean velocity profile for a given vorticity distribution over the pipe cross-section is presented in this paper1. The velocity profile and the vorticity distribution are axisymmetric, which means that the radius is the only variable. The importance of the vortex field for the flow analysis is discussed in the paper. The polynomial function with four free parameters is chosen for the vorticity distribution. Free parameters of this function are determined using boundary conditions. There are also two free exponents in the polynomial. These exponents are determined based on the comparison of this analytical formula with experimental data. Experimental data are taken from the Princeton superpipe data which consist of 26 velocity profiles for a wide range of Reynolds numbers (Re). This analytical formula for the mean velocity profile is more precise than the previous one and it is possible to use it for the wide range of Reynolds number <31,577; 35,259,000>. This formula is easy to use, to integrate, or to derivate. The empirical formulas for the profile parameters as a function of Re are also included in this paper. All information for the mean velocity profile prediction in the mentioned Re range are in the paper. It means that it is necessary to know the average velocity v(av), the pipe radius R, and Re to be able to predict the turbulent mean velocity profile in a pipe.

Three-dimensional asymmetric maximum weight lifting prediction considering dynamic joint strength

2021 ◽  
pp. 095441192098703
Author(s):  
Rahid Zaman ◽  
Yujiang Xiang ◽  
Jazmin Cruz ◽  
James Yang
Keyword(s):  
Experimental Data ◽  
Degrees Of Freedom ◽  
Inverse Dynamics ◽  
Three Dimensional ◽  
Optimization Method ◽  
Weight Lifting ◽  
Joint Torque ◽  
Maximum Weight ◽  
Angular Velocities ◽  
Asymmetric Lifting

In this study, the three-dimensional (3D) asymmetric maximum weight lifting is predicted using an inverse-dynamics-based optimization method considering dynamic joint torque limits. The dynamic joint torque limits are functions of joint angles and angular velocities, and imposed on the hip, knee, ankle, wrist, elbow, shoulder, and lumbar spine joints. The 3D model has 40 degrees of freedom (DOFs) including 34 physical revolute joints and 6 global joints. A multi-objective optimization (MOO) problem is solved by simultaneously maximizing box weight and minimizing the sum of joint torque squares. A total of 12 male subjects were recruited to conduct maximum weight box lifting using squat-lifting strategy. Finally, the predicted lifting motion, ground reaction forces, and maximum lifting weight are validated with the experimental data. The prediction results agree well with the experimental data and the model’s predictive capability is demonstrated. This is the first study that uses MOO to predict maximum lifting weight and 3D asymmetric lifting motion while considering dynamic joint torque limits. The proposed method has the potential to prevent individuals’ risk of injury for lifting.

scholarly journals Steady flow separation patterns in a 45 degree junction

2000 ◽  
Vol 411 ◽  
pp. 1-38 ◽  
Author(s):  
C. ROSS ETHIER ◽  
SUJATA PRAKASH ◽  
DAVID A. STEINMAN ◽  
RICHARD L. LEASK ◽  
GREGORY G. COUCH ◽  
...  
Keyword(s):  
Flow Separation ◽  
Stokes Equations ◽  
Bypass Graft ◽  
Three Dimensional ◽  
Symmetry Plane ◽  
Axial Flow ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Measured Velocity ◽  
Curved Tube

Numerical and experimental techniques were used to study the physics of flow separation for steady internal flow in a 45° junction geometry, such as that observed between two pipes or between the downstream end of a bypass graft and an artery. The three-dimensional Navier–Stokes equations were solved using a validated finite element code, and complementary experiments were performed using the photochromic dye tracer technique. Inlet Reynolds numbers in the range 250 to 1650 were considered. An adaptive mesh refinement approach was adopted to ensure grid-independent solutions. Good agreement was observed between the numerical results and the experimentally measured velocity fields; however, the wall shear stress agreement was less satisfactory. Just distal to the ‘toe’ of the junction, axial flow separation was observed for all Reynolds numbers greater than 250. Further downstream (approximately 1.3 diameters from the toe), the axial flow again separated for Re [ges ] 450. The location and structure of axial flow separation in this geometry is controlled by secondary flows, which at sufficiently high Re create free stagnation points on the model symmetry plane. In fact, separation in this flow is best explained by a secondary flow boundary layer collision model, analogous to that proposed for flow in the entry region of a curved tube. Novel features of this flow include axial flow separation at modest Re (as compared to flow in a curved tube, where separation occurs only at much higher Re), and the existence and interaction of two distinct three-dimensional separation zones.

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