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AERODYNAMIC STUDY OF MODERN SEPAK TAKRAW BALL: FLOW VISUALIZ

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keroro gunzo

on 14 January 2015

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Transcript of AERODYNAMIC STUDY OF MODERN SEPAK TAKRAW BALL: FLOW VISUALIZ

AERODYNAMIC STUDY OF MODERN SEPAK TAKRAW BALL: FLOW VISUALIZATION TEST APPROACH
INTRODUCTION
Ball Description:
The modern takraw ball is made by interwoven plastic strip hoop intertwine into a spherical shape
Traditional ball made of rattan
These interwoven hoops form 12 pentagon holes and 30 intersections for modern ball
LITERATURE REVIEW
factors affecting aerodynamic
geometry(Barber, Haake & Carre)
velocity(Haake, Goodwill & Carre)
orientation( Seo & Shibata)
METHODOLOGY
OBJECTIVE
to investigate the flow field produce by sepak takraw ball in term of aerodynamic perspective using smoke visualization method
to simulate the flow visualization of sepak takraw ball using computational fluid dynamic platform
to compare and analyse results of both experiment and CFD in term of flow visualization
DISCUSSION
at speed 3m/s, the sepak takraw ball is in subcritical state which is before 'drag crisis'
wake behind the sepak takraw ball became more chaotic since the holes opening of the sepak takraw ball contribute directly towards the region behind the ball
the separation point of the sepak takraw ball became almost symmetrical thus contribute to more lower lift
the higher drag also cause due to pressure inside the ball since the flow stream freely inside the sepak takraw ball create pressure difference inside the sepak takraw ball as well as outside surface of the ball
FLOW CHART ACTIVITIES
Background :
sepak means "kick" in Bahasa Melayu while takraw which means "ball" or "woven ball" in Thailand language.(Sanitate et al., 1998)
Two teams consist of three player each using only all limbs except hand to control ballexhange ball within 3 contacts
SCOPE & CONSTRAINT
CONCLUSION
FUTURE WORK
Test Ball:
Salim model SS1
Weight only 0.18 kg
diameter approximately 0.135m
the steel beam was determine preliminary measure to fit the wind tunnel test section
Experimental Procedure
test section size of opening 40 cm x 40 cm
wind speed approximately 3 m/s
using smoke visulization method
Different orientation
Including rotating condition
only static position
at wind speed of 3 m/s (higher than this the flow is unable become too chaotic thus more unclear)
CFD
using Ansys CFX software
CAD geometry part
same boundary condition as experiment
Results Comparison
Wind tunnel
CFD method
Import in CFD platform- Ansys CFX
Prepare mounting for the ball
setup smoke mechanism
Run experiment using open type wind tunnel
Video record using DSLR camera during the experiment
Video analysis
Model CAD
Different wind speed
Different visualization method ie. tuft grid method
using open type wind tunnel
only flow visualization results for experiment
Thank you
Reference
Sanitate, Rebecca, Harney, John, Schiro, Michael, Wollbrinck, Douglas, Carrigg, Michael, & Buell, Cathy. (1998). Takraw: A Global Sport. Strategies, 11(4), 29-33.
Barber S, Haake SJ and Carré M. Using CFD to understand the effects of seam geometry on soccer ball aerodynamics. The Engineering of Sport 6. 2006: 127-32.
Haake S, Goodwill S and Carre M. A new measure of roughness for defining the aerodynamic performance of sports balls. Proceedings of the Institution of Mechanical Engineers, part C: Journal of mechanical engineering science. 2007; 221: 789-806.
Seo K, Shibata M. Aerodynamic characteristics of a sepak takraw ball on its face orientation. The Impact of technology on Sport III 2009: 372-82.
create box surrounding sepak takraw model
mesh generation
setup boundary condition
run simulation
analyse results
there is no drag crisis during wind speed at 3 m/s
CFD simulation is reliable for flow visualization of sepak takraw ball
unique geometry shape of sepak takraw ball especially the surface roughness of the ball significantly influence the aerodynamic of the sepak takraw ball
PROBLEM STATEMENT
LITERATURE REVIEW
aerodynamic properties
lift-the force on balls which are directed perpendicular to the ball's trajectory
drag-force in the opposite direction of the ball's flight path(Kensrud & Smith)
method of analysis aerodynamic:
quantitative ie drag coefficient
qualitative ie flow visualization
there are several flow visualization method
hot smoke wire mechanism
spark tracing method
tuft grid method
boundary layer theory
consist of two laminar and turbulent
starts of laminar then turn turbulent as Reynolds number increases
can induce 'drag crisis' where drag suddenly drop during transition laminar to turbulent
there are no information on sepak takraw flow field
how the flow affected the aerodynamic sepak takraw
Figure 2 : point separation for both experiment and CFD method
Drag coefficient : 0.48684
Lift coefficient : -0.0130915
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