Vortex force decomposition in the tip region of impulsively-started flat plates

2014 ◽  
Vol 756 ◽  
pp. 758-770 ◽  
Author(s):  
Jochen Kriegseis ◽  
David E. Rival
Keyword(s):  
Particle Tracking Velocimetry ◽  
Three Dimensional ◽  
Velocity Fields ◽  
The Body ◽  
Flat Plates ◽  
Impulsive Motion ◽  
Vortical Structures ◽  
Low Aspect Ratio ◽  
Force Moment ◽  
Force Decomposition

AbstractAn investigation into the influence of seemingly analogous kinematics (plunge versus tow) for rapidly accelerating, low-aspect-ratio plates has been performed. The instantaneous forces and velocity fields were obtained simultaneously using a six-component force/moment sensor together with a three-dimensional particle tracking velocimetry (3D-PTV) system. Despite identical effective shear-layer velocities and effective angles of attack, the force histories are found to vary between the two aforementioned cases (plunge versus tow) once the impulsive motion is complete, as originally reported on by Kriegseis et al. (J. Fluid Mech., vol. 736, 2013, pp. 91–106). In order to uncover the cause for this curious discrepancy between the two analogous cases a vortex force decomposition is implemented. It is shown that the interplay between growth and orientation of the vortical structures significantly affects vortical hydrodynamic impulse and vortex force, and thus the net lift on the body.

Force and power of flapping plates in a fluid

2012 ◽  
Vol 712 ◽  
pp. 598-613 ◽  
Author(s):  
Gao-Jin Li ◽  
Xi-Yun Lu
Keyword(s):  
Dynamic Analysis ◽  
Numerical Solutions ◽  
Vortical Structure ◽  
Three Dimensional ◽  
The Body ◽  
Vortical Structures ◽  
Ring Model ◽  
Essential Properties ◽  
Physical Insight ◽  
Insight Into

AbstractThe force and power of flapping plates are studied by vortex dynamic analysis. Based on the dynamic analysis of the numerical results of viscous flow past three-dimensional flapping plates, it is found that the force and power are strongly dominated by the vortical structures close to the body. Further, the dynamics of the flapping plate is investigated in terms of viscous vortex-ring model. It is revealed that the model can reasonably reflect the essential properties of the ring-like vortical structure in the wake, and the energy of the plate transferred to the flow for the formation of each vortical structure possesses a certain relation. Moreover, simplified formulae for the thrust and efficiency are proposed and verified to be reliable by the numerical solutions and experimental measurements of animal locomotion. The results obtained in this study provide physical insight into the understanding of the dynamic mechanisms relevant to flapping locomotion.

The Role of the Hand During Freestyle Swimming

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Raymond C. Z. Cohen ◽  
Paul W. Cleary ◽  
Bruce R. Mason ◽  
David L. Pease
Keyword(s):  
Fluid Model ◽  
Three Dimensional ◽  
The Body ◽  
Cfd Modeling ◽  
Vortical Structures ◽  
Video Footage ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Computational Fluid Dynamics Cfd ◽  
Lift And Drag

The connections between swimming technique and the fluid dynamical interactions they generate are important for assisting performance improvement. Computational fluid dynamics (CFD) modeling provides a controlled and unobtrusive way for understanding the fundamentals of swimming. A coupled biomechanical–smoothed particle hydrodynamics (SPH) fluid model is used to analyze the thrust and drag generation of a freestyle swimmer. The swimmer model was generated using a three-dimensional laser body scan of the athlete and digitization of multi-angle video footage. Two large distinct peaks in net streamwise thrust are found during the stroke, which coincide with the underwater arm strokes. The hand motions generate vortical structures that travel along the body toward the kicking legs and the hands are shown to produce thrust using both lift and drag. These findings advance understanding of the freestyle stroke and may be used to improve athlete technique.

scholarly journals Role of the tip vortex in the force generation of low-aspect-ratio normal flat plates

2007 ◽  
Vol 581 ◽  
pp. 453-468 ◽  
Author(s):  
MATTHEW J. RINGUETTE ◽  
MICHELE MILANO ◽  
MORTEZA GHARIB
Keyword(s):  
Aspect Ratio ◽  
Vortex Formation ◽  
Three Dimensional ◽  
Unsteady Motion ◽  
Tip Vortex ◽  
Flat Plates ◽  
Low Aspect Ratio ◽  
Start Up ◽  
Image Velocimetry

We investigate experimentally the force generated by the unsteady vortex formation of low-aspect-ratio normal flat plates with one end free. The objective of this study is to determine the role of the free end, or tip, vortex. Understanding this simple case provides insight into flapping-wing propulsion, which involves the unsteady motion of low-aspect-ratio appendages. As a simple model of a propulsive half-stroke, we consider a rectangular normal flat plate undergoing a translating start-up motion in a towing tank. Digital particle image velocimetry is used to measure multiple perpendicular sections of the flow velocity and vorticity, in order to correlate vortex circulation with the measured plate force. The three-dimensional wake structure is captured using flow visualization. We show that the tip vortex produces a significant maximum in the plate force. Suppressing its formation results in a force minimum. Comparing plates of aspect ratio six and two, the flow is similar in terms of absolute distance from the tip, but evolves faster for aspect ratio two. The plate drag coefficient increases with decreasing aspect ratio.

scholarly journals Numerical Simulation of a Three-Dimensional Fish-like Body Swimming with Finlets

2012 ◽  
Vol 11 (4) ◽  
pp. 1323-1333 ◽  
Author(s):  
Shizhao Wang ◽  
Xing Zhang ◽  
Guowei He
Keyword(s):  
Three Dimensional ◽  
The Body ◽  
Hydrodynamic Performance ◽  
Rectangular Plates ◽  
Caudal Peduncle ◽  
Local Flow ◽  
Vortical Structures ◽  
Numerical Result ◽  
Simulation Based ◽  
3D Fish

AbstractThe swimming of a 3D fish-like body with finlets is numerically investigated at Re = 1000 (the Reynolds number is based on the uniform upstream flow and the length of the fish-like body). The finlets are simply modeled as thin rigid rectangular plates that undulate with the body. The wake structures and the flow around the caudal peduncle are studied. The finlets redirect the local flow across the caudal peduncle but the vortical structures in the wake are almost not affected by the finlets. Improvement of hydrodynamic performance has not been found in the simulation based on this simple model. The present numerical result is in agreement with that of the work of Nauen and Lauder [J. Exp. Biol., 204 (2001), pp. 2251-2263] and partially supports the hypothesis of Webb [Bull. Fish. Res. Bd. Can., 190 (1975), pp. 1-159].

Some Aspects of Three-Dimensional Cavity Flow

1957 ◽  
Vol 61 (557) ◽  
pp. 345-352
Author(s):  
A. J. Taylor-Russell
Keyword(s):  
Static Pressure ◽  
Three Dimensional ◽  
Cavity Flow ◽  
Wake Flow ◽  
Flat Plates ◽  
Mean Velocity ◽  
Wake Flows ◽  
Low Aspect Ratio ◽  
Recirculatory Flow ◽  
Made In

SummarySome experiments concerned with the wake flows of a number of flat plates of low aspect ratio (Fail, Owen and Eyre) have suggested that for large angles of inclination to the undisturbed stream the wake includes a region of recirculation. The present observations include a detailed study of this region, with particular reference to the wake produced by an equilateral triangular plate, and an attempt is made to explain why the recirculatory flow is found only at angles of incidence greater than 35°. The data includes some wind tunnel measurements of force coefficients, static pressure and mean velocity, and observations of the wake flow made in a smoke tunnel and in a water tunnel.

Scanning electron microscopy of freeze-fractured prescapular lymph node of caprine

1984 ◽  
Vol 42 ◽  
pp. 244-245
Author(s):  
O. Faroon ◽  
F. Al-Bagdadi ◽  
T. G. Snider ◽  
C. Titkemeyer
Keyword(s):  
Lymph Node ◽  
Lymph Nodes ◽  
Lymphatic System ◽  
Three Dimensional ◽  
Meat Products ◽  
The Body ◽  
Morphological Data ◽  
The World ◽  
Cellular Constituent ◽  
Scanning Electron

The lymphatic system is very important in the immunological activities of the body. Clinicians confirm the diagnosis of infectious diseases by palpating the involved cutaneous lymph node for changes in size, heat, and consistency. Clinical pathologists diagnose systemic diseases through biopsies of superficial lymph nodes. In many parts of the world the goat is considered as an important source of milk and meat products.The lymphatic system has been studied extensively. These studies lack precise information on the natural morphology of the lymph nodes and their vascular and cellular constituent. This is due to using improper technique for such studies. A few studies used the SEM, conducted by cutting the lymph node with a blade. The morphological data collected by this method are artificial and do not reflect the normal three dimensional surface of the examined area of the lymph node. SEM has been used to study the lymph vessels and lymph nodes of different animals. No information on the cutaneous lymph nodes of the goat has ever been collected using the scanning electron microscope.

Clinical Utility of an Exoskeleton Robot Using 3-Dimensional Scanner Modeling in Burn Patient: A Case Report

2021 ◽  
Author(s):  
So Young Joo ◽  
Seung Yeol Lee ◽  
Yoon Soo Cho ◽  
Sangho Yi ◽  
Cheong Hoon Seo
Keyword(s):  
Burn Injury ◽  
Hand Function ◽  
Three Dimensional ◽  
The Body ◽  
3D Technology ◽  
Early Management ◽  
3 Dimensional ◽  
Exoskeleton Robot ◽  
Physical Abilities ◽  
Upper Limb Dysfunction

Abstract Hands are the part of the body that are most commonly involved in burns, and the main complications are finger joint contractures and nerve injuries. Hypertrophic scarring cannot be avoided despite early management of acute hand burn injuries, and some patients may need application of an exoskeleton robot to restore hand function. To do this, it is essential to individualize the customization of the robot for each patient. Three-dimensional (3D) technology, which is widely used in the field of implants, anatomical models, and tissue fabrication, makes this goal achievable. Therefore, this report is a study on the usefulness of an exoskeleton robot using 3D technology for patients who lost bilateral hand function due to burn injury. Our subject was a 45-year-old man with upper limb dysfunction of 560 days after a flame and chemical burn injury, with resultant impairment of manual physical abilities. After wearing an exoskeleton robot made using 3D printing technology, he could handle objects effectively and satisfactorily. This innovative approach provided considerable advantages in terms of customization of size and reduction in manufacturing time and costs, thereby showing great potential for use in patients with hand dysfunction after burn injury.

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