Evaluation of fish-injury mechanisms during exposure to turbulent shear flow

2005 ◽  
Vol 62 (7) ◽  
pp. 1513-1522 ◽  
Author(s):  
Zhiqun Deng ◽  
Gregory R Guensch ◽  
Craig A McKinstry ◽  
Robert P Mueller ◽  
Dennis D Dauble ◽  
...  
Keyword(s):  
High Speed ◽  
Motion Tracking ◽  
Oncorhynchus Tshawytscha ◽  
Three Dimensional ◽  
Turbulent Shear ◽  
Control Group ◽  
Similar Data ◽  
Turbulent Shear Flow ◽  
Eye Injuries ◽  
Injury Mechanisms

Understanding the factors that injure or kill turbine-passed fish is important to the operation and design of the turbines. Motion-tracking analysis was performed on high-speed, high-resolution digital videos of juvenile salmonids exposed to a laboratory-generated shear environment to isolate injury mechanisms. Hatchery-reared fall chinook salmon (Oncorhynchus tshawytscha, 93–128 mm in length) were introduced into a submerged, 6.35-cm-diameter water jet at velocities ranging from 12.2 to 19.8 m·s–1, with a reference control group released at 3 m·s–1. Injuries typical of turbine-passed fish were observed and recorded. Three-dimensional trajectories were generated for four locations on each fish released. Time series of velocity, acceleration, force, jerk, and bending angle were computed from the three-dimensional trajectories. The onset of minor, major, and fatal injuries occurred at nozzle velocities of 12.2, 13.7, and 16.8 m·s–1, respectively. Opercle injuries occurred at 12.2 m·s–1 nozzle velocity, while eye injuries, bruising, and loss of equilibrium were common at velocities of 16.8 m·s–1 and above. Of the computed dynamic parameters, acceleration showed the strongest predictive power for eye and opercle injuries and overall injury level, and it may provide the best potential link between laboratory studies of fish injury, field studies designed to collect similar data in situ, and numerical modeling.

Three-Dimensional Buoyant Wall Jets Released Into a Coflowing Turbulent Boundary Layer

1990 ◽  
Vol 112 (2) ◽  
pp. 356-362 ◽  
Author(s):  
J. R. Sinclair ◽  
P. R. Slawson ◽  
G. A. Davidson
Keyword(s):  
Three Dimensional ◽  
Ground Level ◽  
Turbulent Shear ◽  
Wall Jet ◽  
Turbulent Shear Flow ◽  
Streamwise Vorticity ◽  
Buoyant Jet ◽  
Buoyant Jets ◽  
Jet Trajectory ◽  
Model Predictions

Experiments have been conducted in a water flume to simulate finite-length line sources of heat that issue horizontally at ground level into a coflowing turbulent shear flow. The downstream development of each buoyant jet is documented by detailed mean temperature measurements, which are analyzed to determine the jet trajectory, spread rates, and distance to the point of liftoff from the surface. In addition, a three-dimensional, parabolic, numerical model based on the fundamental conservation equations is developed. Model predictions of several buoyant jets compare reasonably with the experimental data and suggest that the strength of the streamwise vorticity plays an important role in governing liftoff of a buoyant wall jet from the surface.

Spatial and statistical analysis of coherent vortical structures within a stress-driven free-surface turbulent shear flow

2020 ◽  
Author(s):  
Po-Chen Chen ◽  
Wu-ting Tsai
Keyword(s):  
Free Surface ◽  
High Speed ◽  
Surface Friction ◽  
Turbulent Shear ◽  
Wind Condition ◽  
Turbulent Shear Flow ◽  
Streamwise Vortices ◽  
Vortical Structures ◽  
Horseshoe Vortices ◽  
Low Speed Streaks

<p>The water surface under high wind condition is characterized by elongated high-speed streaks and randomly emerged low-speed streaks, which are attributed to underneath coherent vortical motions. These vortical structures within aqueous turbulent boundary layer plays a critical role in turbulent exchange, their characteristics and statistics are therefore of interest in this study. Direct numerical simulation of an aqueous turbulent flow bounded by a stress-driven flat free surface was performed. Simulation results of cases with high wind condition (surface friction velocity = 1.22 cm/s) as well as weak wind condition (surface friction velocity = 0.71 cm/s) are analyzed. To identify the underlying vortical structures, an indicator of swirling strength derived from local velocity-gradient tensor is adopted. A formal classification scheme, based on the topological geometry of the vortex core, is then applied to classify the identified structures. Surface layers with the two wind conditions reveal similar results in statistics and spatial distribution of vortical structures. Two types of characteristic vortices which induce the surface streaks are extracted, including quasi-streamwise vortex and reversed horseshoe vortex (head pointing upstream), most inclining at about 10 to 20 degrees. Quasi-streamwise vortices are the dominant structure, and both high- and low-speed streaks are fringed with such vortices; they adjoin the surface streaks as counter-rotating arrays in either staggered or side-by-side spatial arrangement. The length of quasi-streamwise vortices, however, are significantly shorter than the corresponding surface streaks, only 10% of the extracted quasi-streamwise vortices are longer than 150 wall units. Reversed horseshoe vortices, associated with downwelling motions and surface convergence, are located beneath the high-speed streaks. In contrast to the turbulent boundary layer next to a flat wall, typical forward horseshoe vortices (head pointing downstream) associated with upwelling motions are barely found within the free-surface turbulent shear flow.</p><p>This work was supported by the Taiwan Ministry of Science and Technology (MOST 107-2611-M-002 -014 -MY3).</p>

Kinematic Differences Between Those With and Without Medial Knee Displacement During a Single-leg Squat

2014 ◽  
Vol 30 (6) ◽  
pp. 707-712 ◽  
Author(s):  
Timothy C. Mauntel ◽  
Barnett S. Frank ◽  
Rebecca L. Begalle ◽  
J. Troy Blackburn ◽  
Darin A. Padua
Keyword(s):  
Motion Tracking ◽  
Tracking System ◽  
Three Dimensional ◽  
Control Group ◽  
Knee Valgus ◽  
Medial Knee ◽  
Lower Extremity Injuries ◽  
Valgus Angle ◽  
Peak Knee ◽  
Single Leg Squat

A greater knee valgus angle is a risk factor for lower extremity injuries. Visually observed medial knee displacement is used as a proxy for knee valgus motion during movement assessments in an attempt to identify individuals at heightened risk for injury. The validity of medial knee displacement as an indicator of valgus motion has yet to be determined during a single-leg squat. This study compared three-dimensional knee and hip angles between participants who displayed medial knee displacement (MKD group) during a single-leg squat and those who did not (control group). Participants completed five single-leg squats. An electromagnetic motion tracking system was used to quantify peak knee and hip joint angles during the descent phase of each squat. MANOVA identified a difference between the MKD and control group kinematics. ANOVA post hoc testing revealed greater knee valgus angle in the MKD (12.86 ± 5.76) compared with the control (6.08 ± 5.23) group. There were no other differences between groups. Medial knee displacement is indicative of knee valgus motion; however, it is not indicative of greater knee or hip rotation, or hip adduction. These data indicate that clinicians can accurately identify individuals with greater knee valgus angle through visually observed medial knee displacement.

scholarly journals Variations on Kolmogorov flow: turbulent energy dissipation and mean flow profiles

2011 ◽  
Vol 670 ◽  
pp. 204-213 ◽  
Author(s):  
B. ROLLIN ◽  
Y. DUBIEF ◽  
C. R. DOERING
Keyword(s):  
Reynolds Number ◽  
Stokes Flow ◽  
Three Dimensional ◽  
Turbulent Energy ◽  
Dissipation Factor ◽  
Turbulent Shear ◽  
Flow Profile ◽  
Turbulent Shear Flow ◽  
Mean Flow ◽  
Flow Profiles

The relation between the form of a body force driving a turbulent shear flow and the dissipation factor β = ϵℓ/U3 is investigated by means of rigorous upper bound analysis and direct numerical simulation. We consider unidirectional steady forcing functions in a three-dimensional periodic domain and observe that a rigorous infinite Reynolds number bound on β displays the same qualitative behaviour as the computationally measured dissipation factor at finite Reynolds number as the force profile is varied. We also compare the measured mean flow profiles with the Stokes flow profile for the same forcing. The mean and Stokes flow profiles are strikingly similar at the Reynolds numbers obtained in the numerical simulations, lending quantitative credence to the notion of a turbulent eddy viscosity.

scholarly journals Biomechanical characteristics of scapula and glenohumeral movements during pitching motion in injury-prone college baseball pitchers

2021 ◽  
Author(s):  
Koji Miyashita ◽  
Sentaro Koshida ◽  
Taro Koyama ◽  
Kenicihro Ota ◽  
Yusuke Tani ◽  
...  
Keyword(s):  
Sports Medicine ◽  
High Speed ◽  
Glenohumeral Joint ◽  
External Rotation ◽  
Three Dimensional ◽  
Control Group ◽  
Shoulder Injuries ◽  
Pitching Motion ◽  
College Baseball ◽  
Baseball Pitchers

Coordination of glenohumeral and scapular movements plays an important role in the injury prevention of baseball pitchers. However, there is no objective data establishing the direct relationship between pitching injuries and associated glenohumeral and scapular movements. Therefore, the objectives of the present study were to demonstrate biomechanical differences in scapular and glenohumeral movements during pitching between injury-prone pitchers and healthy college baseball pitchers. Thirty collegiate baseball pitchers were classified into two groups according to their injury status: injury-prone group (N=15, 20.7±1.4 years, 180.1±6.5 cm, 78.9±5.4 kg) and control group (N=15, 20.9±1.1 years, 177.1±6.6 cm, 72.3±6.7 kg). We obtained the pitching motion data using the three-dimensional motion analysis technique with four high-speed cameras. The horizontal abduction angles of the glenohumeral joint during cocking and acceleration phases were significantly greater in injury-prone pitchers [19.0° (95% CI: 14.4–23.6) at foot contact, −4.0° (95% CI: −7.7 to −0.2) at maximum external rotation (MER), and −0.3° (95% CI: −4.8 to −4.2) at ball release] than in healthy controls [11.7 °(95%CI:7.1 to 16.3) at foot contact, −10.0°(95%CI: −13.7 to −6.3) at MER, and −6.9°(95%CI: −11.4 to −2.4)]( p <0.01). In addition, the external rotation angle (ER) of the scapula at MER was significantly greater in the injury-prone group [−0.1° (95% CI: −5.0 to 4.8)] than in the control group [−12.3° (95% CI: −17.2 to −7.4)] (p<0.01), but there was no difference in the scapular ER during foot contact between the two groups. These results suggests that injury-prone pitchers have less internal rotation of the scapula and more horizontal abduction of the glenohumeral joint during cocking and acceleration phases. Therefore, sports medicine practitioners may need to pay more attention to coordination of scapular and glenohumeral movements during the cocking and acceleration phases of pitching for prevention of shoulder injuries.

scholarly journals Algebraic Growth and Streak Formation in Shear Flows

1990 ◽  
Vol 43 (5S) ◽  
pp. S218-S218
Author(s):  
Marten T. Landahl
Keyword(s):  
Shear Flow ◽  
Velocity Component ◽  
High Speed ◽  
Shear Flows ◽  
Three Dimensional ◽  
Shear Layers ◽  
Turbulent Shear ◽  
Algebraic Instability ◽  
Horizontal Pressure ◽  
The Difference

By examination of the long-term behavior of an initial three-dimensional and localized disturbance in an inflection-free shear flow a detailed study of the algebraic instability mechanism of an inviscid shear flow (Landahl, 1980) is carried out. It is shown that the vertical velocity component will tend to zero at least as fast as 1/t whereas, as a result of a nonzero liftup of the fluid elements, the streamwise disturbence velocity component will tend to a limiting finite value in a convected frame of reference. For an initial disturbence having a nonzero net vertical momentum along a streamline, the streamwise dimension of the disturbed region is found to grow indefinitely at a rate set by the difference between the maximum and minimum velocities in the parallel flow. The total kinetic energy of the disturbence therefore grows linearly in time through the formation of continuously elongating high-speed or low-speed regions. In these, internal shear layers are formed that intensify through the mechanism of spanwise stretching of the mean vorticity. The effect of a small viscosity is felt primarily in the shear layers so as to make them diffuse and eventually cause the disturbence to decay on a viscous time scale. For the streaky structures near a wall the horizontal pressure gradients are found to be small, making possible a simple approximate treatment of nonlinearty. Such an analysis suggests the possibility of the appearance of a rapid outflow event (“bursting”) from the wall that may occur at a finite time inversely proportional to the amplitude of the initial disturbance. On basis of the analysis presented it is proposed that algebraic growth is the primary mechanism for the formation of streaks in laminar and turbulent shear flows.

Computational Study of Flow and Mixing Characteristics of Turbulent Opposed Jets

2013 ◽  
Author(s):  
Tarek Abdel-Salam ◽  
Srikanth B. Pidugu
Keyword(s):  
Numerical Simulations ◽  
Computational Study ◽  
Combustion Process ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Equation Model ◽  
Turbulent Shear ◽  
Jet Flows ◽  
Turbulent Shear Flow ◽  
Mixing Characteristics

The turbulent mixing of jet flows is one of the important problems of turbulent shear flow due to its application in combustion process involving fuel-oxidizer combinations such as hydrogen-air and methane-air. Fluid dynamics of opposed jets is not completely clarified as there are questions unanswered about flow stability and structure. In the present work, three-dimensional numerical simulations were conducted to study flow and mixing characteristics of turbulent opposed-jets. The numerical simulations were carried out with a finite volume CFD code. Turbulence is treated with the two equation model, the k-ε model. Nozzle diameter (d) and nozzle separation (W) are kept constant and equals to 32mm. Also, different jet velocities (Uj) have been examined corresponding to Reynolds numbers of 4500 to 12,000. Both confined and unconfined cases were simulated.

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