Comparative Analysis of Thrust Production for Distinct Arm-Pull Styles in Competitive Swimming

A computational fluid dynamics (CFD) based analysis of the propulsive forces generated by two distinct styles of arm-pulls in front-crawl as well as backstroke is presented in this Technical Brief. Realistic models of the arm pulling through water are created by combining underwater video footage and laser-scans of an arm with computer animation. The contributions of drag and lift forces on the arm to thrust are computed from CFD, and it is found that lift forces provide a dominant contribution to thrust for all the arm-pull styles examined. However, contrary to accepted notions in swimming, pronounced sculling (lateral motion) not only does not increase the contribution of lift forces on the hand to overall thrust, it decreases the contribution of drag forces to thrust. Consequently, pronounced sculling seems to reduce the effectiveness of the arm-pull.

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Prediction of drag and lift forces of a high-speed vessel at full scale by CFD-based GEOSIM method

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/14750902211070743 ◽

2022 ◽

pp. 147509022110707

Author(s):

Ugur Can ◽

Sakir Bal

Keyword(s):

High Speed ◽

Full Scale ◽

Navier Stokes ◽

Drag Forces ◽

Fluid Body ◽

Unsteady Rans ◽

Lift Forces ◽

Drag And Lift ◽

Lift And Drag ◽

Model Family

In this study, it was aimed to obtain an accurate extrapolation method to compute lift and drag forces of high-speed vessels at full-scale by using CFD (Computational Fluid Dynamics) based GEOSIM (GEOmetrically SIMilar) method which is valid for both fully planing and semi-planing regimes. Athena R/V 5365 bare hull form with a skeg which is a semi-displacement type of high-speed vessel was selected with a model family for hydrodynamic analyses under captive and free to sinkage/trim conditions. Total drag and lift forces have been computed for a generated GEOSIM family of this form at three different model scales and full-scale for Fr = 0.8 by an unsteady RANS (Reynolds Averaged Navier–Stokes) solver. k–ε turbulence model was used to simulate the turbulent flow around the hulls, and both DFBI (Dynamic Fluid Body Interaction) and overset mesh technique were carried out to model the heave and pitch motions under free to sinkage/trim condition. The computational results of the model family were used to get “drag-lift ratio curve” for Athena hull at a fixed Fr number and so the corresponding results at full scale were predicted by extrapolating those of model scales in the form of a non-dimensional ratios of drag-lift forces. Then the extrapolated full-scale results calculated by modified GEOSIM method were compared with those of full-scale CFD and obtained by Froude extrapolation technique. The modified GEOSIM method has been found to be successful to compute the main forces (lift and drag) acting on high-speed vessels as a single coefficient at full scale. The method also works accurately both under fully and semi-planing conditions.

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Analysis of drag and lift forces for a sedan car using a rear lip spoiler

Revista de Ingeniería Mecánica ◽

10.35429/jme.2020.13.4.23.31 ◽

2020 ◽

pp. 23-31

Author(s):

Juan Gregorio Hortelano-Capetillo ◽

J. Merced Martínez-Vázquez ◽

José Luis Zúñiga-Cerroblanco ◽

Gabriel Rodriguez-Ortiz

Keyword(s):

Flow Simulation ◽

Simulation Software ◽

Drag And Lift Coefficients ◽

Drag Forces ◽

Lift Forces ◽

Drag And Lift

In this research, aerodynamic tests were carried out using Solidworks Flow Simulation software on a Sedan-type car, implementing different sizes of lip-type spoilers at the rear to obtain the results of the drag and lift coefficients produced by movement. of the air regardless of the design at the rear of the car and analyze if there was improvement in aerodynamics. Analyzing the results, it is obtained that the aerodynamics of the car is improved when a lip-type spoiler is fitted, the lift forces were reduced, whereas the drag forces remained constant for all the different designs.

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Computational Fluid Dynamics Study of Swimmer's Hand Velocity, Orientation, and Shape: Contributions to Hydrodynamics

BioMed Research International ◽

10.1155/2013/140487 ◽

2013 ◽

Vol 2013 ◽

pp. 1-14 ◽

Cited By ~ 9

Author(s):

Milda Bilinauskaite ◽

Vishveshwar Rajendra Mantha ◽

Abel Ilah Rouboa ◽

Pranas Ziliukas ◽

Antonio Jose Silva

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Fluid Flow ◽

Steady State ◽

Drag Force ◽

3D Models ◽

Hydrodynamic Characteristics ◽

Front Crawl ◽

Drag Forces ◽

Computational Fluid Dynamics Cfd

The aim of this paper is to determine the hydrodynamic characteristics of swimmer’s scanned hand models for various combinations of both the angle of attack and the sweepback angle and shape and velocity of swimmer's hand, simulating separate underwater arm stroke phases of freestyle (front crawl) swimming. Four realistic 3D models of swimmer's hand corresponding to different combinations of separated/closed fingers positions were used to simulate different underwater front crawl phases. The fluid flow was simulated using FLUENT (ANSYS, PA, USA). Drag force and drag coefficient were calculated using (computational fluid dynamics) CFD in steady state. Results showed that the drag force and coefficient varied at the different flow velocities on all shapes of the hand and variation was observed for different hand positions corresponding to different stroke phases. The models of the hand with thumb adducted and abducted generated the highest drag forces and drag coefficients. The current study suggests that the realistic variation of both the orientation angles influenced higher values of drag, lift, and resultant coefficients and forces. To augment resultant force, which affects swimmer's propulsion, the swimmer should concentrate in effectively optimising achievable hand areas during crucial propulsive phases.

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Investigation of Drag and Lift Forces over the Profile of Car with Rearspoiler using CFD

International Journal of Advances in Scientific Research ◽

10.7439/ijasr.v1i8.2510 ◽

2015 ◽

Vol 1 (8) ◽

pp. 331

Author(s):

Naveen Kumar Velagapudi ◽

Lalit Narayan K. ◽

L. N. V. Narasimha Rao ◽

Sri Ram Y.

Keyword(s):

Drag Force ◽

High Speed ◽

Aerodynamic Drag ◽

Fuel Utilization ◽

Ansys Fluent ◽

Total Drag ◽

Rear Spoiler ◽

Computational Fluid Dynamics Cfd ◽

Lift Forces ◽

Drag And Lift

Now a days demand of a high speed car is increasing in which vehicle stability is of major concern. Forces like drag& lift,weight,side forces and thrust acts on a vehicle when moving on road which significantly effect the fuel consumption The drag force is produced by relative motion between air and vehicle and about 60% of total drag is produced at the rear end. Reduction of drag force at the rear end improves the fuel utilization. This work aims to reduce the drag force which improves fuel utilization and protects environment as well. In the stage of work a sedan car with different types of spoilers are used to reduce the aerodynamic drag force. The design of sedan car has been done on CATIA-2010 and the same is used for analysis in ANSYS-(fluent). The analysis is done for finding out drag and lift forces at different velocities, and spoilers. This study proposes an effective numerical model based on the computational fluid dynamics (CFD) approach to obtain the flow structure around a passenger car with a rear spoiler

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Correlation Between Vibration Excitation Forces and the Dynamic Characteristics of Two-Phase Flow in a Rotated Triangular Tube Bundle

Volume 9: 6th FSI, AE and FIV and N Symposium ◽

10.1115/pvp2006-icpvt-11-93797 ◽

2006 ◽

Cited By ~ 4

Author(s):

C. Zhang ◽

M. J. Pettigrew ◽

N. W. Mureithi

Keyword(s):

Void Fraction ◽

Cross Flow ◽

Main Flow ◽

Phase Flow ◽

Two Phase ◽

Drag Forces ◽

Vibration Excitation ◽

Tube Bundles ◽

Lift Forces ◽

Drag And Lift

Two-phase cross flow exists in many shell-and-tube heat exchangers. Flow-induced vibration excitation forces can cause tube motion that will result in long-term fretting-wear or fatigue. Detailed flow and vibration excitation force measurements in tube bundles subjected to two-phase cross flow are required to understand the underlying vibration excitation mechanisms. Some of this work has already been done. The distributions of both void fraction and bubble velocity in rotated-triangular tube bundles were obtained. Somewhat unexpected but significant quasi-periodic forces in both the drag and lift directions were measured. The present work aims at understanding the nature of such unexpected drag and lift quasi-periodic forces. An experimental program was undertaken with a rotated-triangular array of cylinders subjected to air/water flow to simulate two-phase mixtures. Fiber-optic probes were developed to measure local void fraction. Both the dynamic lift and drag forces were measured with a strain gage instrumented cylinder. The investigation showed that the quasi-periodic drag and lift forces are generated by different mechanisms that have not been observed so far. The quasi-periodic drag forces appear related to the momentum flux fluctuations in the main flow path between the cylinders. The quasi-periodic lift forces, on the other hand, are mostly correlated to oscillations in the wake of the cylinders. The relationships between the lift or drag forces and the dynamic characteristics of two-phase flow are established through fluid mechanics momentum equations. The quasi-periodic lift forces are related to local void fraction measurements in the unsteady wake area between upstream and downstream cylinders. The quasi-periodic drag forces correlate well with similar measurements in the main flow stream between cylinders.

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Influence of the Draft Condition on Vortex-Induced Motions of a Semi-Submersible Platform With Four Square Columns

Volume 1: Offshore Technology; Offshore Geotechnics ◽

10.1115/omae2016-54764 ◽

2016 ◽

Cited By ~ 1

Author(s):

Mingyue Liu ◽

Longfei Xiao ◽

Haining Lu ◽

Jun Li ◽

Xiaochuan Yu

Keyword(s):

Column Height ◽

Transverse Motion ◽

Experimental Investigations ◽

Drag Forces ◽

Draft Model ◽

Restoring Forces ◽

Lift Forces ◽

Four Square ◽

Drag And Lift ◽

Motion Amplitude

The vortex-induced motions (VIM) phenomenon of semi-submersibles has drawn increasing attention with the development (mainly increase of column size) of new semi-submersibles. Due to the elongated submerged columns and the enlarged projected area to current, deep-draft semi-submersible platforms are susceptible to higher in-line drag forces and transverse vortex-induced lift forces, resulting in considerable horizontal motions in a current environment. In order to check the influence of draft conditions on VIM of the semi-submersible platform with four square columns, experimental investigations with five draft ratios varying from 0.87 to 1.90 were carried out in a towing tank. The 6-degree-of-freedom (6-DOF) motions of the model were recorded by the motion acquisition system, in synchronisation with restoring forces provided by four load cells, one for each horizontal mooring spring. This paper discusses the dynamic behavior of a semi-submersible platform in five different draft conditions, including coupled motions at the water surface plane, drag and lift forces, and spectral analysis. It is shown that the largest transverse amplitudes are around 75% of the column width in the range of 6.0 ≤ Ur ≤ 8.0 for the deep-draft semi-submersible (H/L = 1.90). With 50% of the immerged column height of the deep-draft model, a 30% decrease in the transverse motion amplitude can be seen. Furthermore, the effects of the draft condition on yaw responses and current loads are also addressed.

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Correlation Between Vibration Excitation Forces and the Dynamic Characteristics of Two-Phase Cross Flow in a Rotated-Triangular Tube Bundle

Journal of Pressure Vessel Technology ◽

10.1115/1.2826381 ◽

2008 ◽

Vol 130 (1) ◽

Cited By ~ 5

Author(s):

C. Zhang ◽

M. J. Pettigrew ◽

N. W. Mureithi

Keyword(s):

Void Fraction ◽

Cross Flow ◽

Main Flow ◽

Experimental Program ◽

Two Phase ◽

Drag Forces ◽

Vibration Excitation ◽

Tube Bundles ◽

Lift Forces ◽

Drag And Lift

Two-phase cross flow exists in many shell-and-tube heat exchangers. Flow-induced vibration excitation forces can cause tube motion that will result in long-term fretting wear or fatigue. Detailed flow and vibration excitation force measurements in tube bundles subjected to two-phase cross flow are required to understand the underlying vibration excitation mechanisms. Some of this work has already been done. The distributions of both void fraction and bubble velocity in rotated-triangular tube bundles were obtained. Somewhat unexpected but significant quasiperiodic forces in both the drag and lift directions were measured. The present work aims at understanding the nature of such unexpected drag and lift quasiperiodic forces. An experimental program was undertaken with a rotated-triangular array of cylinders subjected to air/water flow to simulate two-phase mixtures. Fiber-optic probes were developed to measure local void fraction. Both the dynamic lift and drag forces were measured with a strain gage instrumented cylinder. The investigation showed that the quasiperiodic drag and lift forces are generated by different mechanisms that have not been previously observed. The quasiperiodic drag forces appear related to the momentum flux fluctuations in the main flow path between the cylinders. The quasiperiodic lift forces, on the other hand, are mostly correlated to oscillations in the wake of the cylinders. The quasiperiodic lift forces are related to local void fraction measurements in the unsteady wake area between upstream and downstream cylinders. The quasiperiodic drag forces correlate well with similar measurements in the main flow stream between cylinders.

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