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Need. In 2050 15% of the Earths carbon dioxide emissions will be from aircrafts (U.S. Global Change Research, 2001) $61billion has already been spent in aviation for fuel alone (Segelstein, 2008)

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  1. Need • In 2050 15% of the Earths carbon dioxide emissions will be from aircrafts (U.S. Global Change Research, 2001) • $61billion has already been spent in aviation for fuel alone (Segelstein, 2008) • If the drag coefficient of a car was reduced by .1 the U.S. oil consumption would decrease by 7.5%. This would save 10 billion gallons of fuel per year. (Fillipone, 1999) http://www.aviation-history.com/theory/lam-flo Figure 1- This picture shows the possible dimpling of an airplane propeller. Although just a prototype should dimples be proved to reduce drag, they could greatly decrease fuel consumption. Knowledge Base • Boundary Layer • At low speeds laminar boundary layer is desirable • Normally the turbulent boundary layer results in higher drag but the advantage is that airflow is increased and there is more forward momentum. • As a result the ball resists the adverse pressure gradient much longer before it separates decreasing drag. Flow Around Smooth Sphere Flow Around Dimpled Sphere boojum.as.arizona.edu Figure 5 Figure 3 Figure 4 www.callawaygolf.com/Global/en-GB/Innovation/GolfBallTechnology/ HEXAerodynamics.html Figures 3, 4, and 5, all show various spheres and their resulting wakes as they travel through the air. Literature Review Smooth vs. Steep Dimples (Kato, 2005) Smooth Dimples • Libi, 2005- Golf Ball Suspension System • Kato, 2005- Steep versus dimpled sphere • Bearman and Harvey (1976)- graph representing the drag coefficients of hexx ball, conventional ball, and smooth sphere Steep Dimples Golf Ball Suspension System (GBSS) (Libii, 2005) Figure 6 http://pdf.aiaa.org/preview/CDReadyMAAC03_774/PV2003_3662.pdf Figure 6 compares the smooth dimples to steep dimples. Results showed that the flow around the sphere with the smooth dimples created less drag. Figure 7 Drag Coefficients for Conventionally Dimpled, Hexx, and Dimpleless Sphere Bearman and Harvey (1976) http://www.eng.monash.edu.au/uicee/worldtransactions/WordTransAbstractsVol5No3/23_NjockLibii15.pdf Drag Force=Mass*Graviy*Tan( Figure 7 shows the GBSS inside a wind tunnel. As the wind starts to flow the ball creates an angle with the protractor. In the experiment a dimpled sphere was compared to a smooth sphere. The results showed that the dimpled sphere had a lower drag force. Figure 8 Figure 8- The x-axis shows the initial velocity (m/s) while the y-axis shows the drag coefficient. The results of the experiment showed that at higher speeds the hexx ball has a lower drag coefficient compared to a smooth sphere, and conventionally dimpled sphere. Purpose The purpose of this experiment is to use golf ball dimpling as a model to improve aerodynamic efficiency. This may be applied to trucks, or airplane propellers and in turn decrease fuel consumption. Hypotheses Field Test • Null Hypothesis H(o)- The golf balls will all travel the same distance and have the same accuracy. • Alternate Hypothesis H(a)- The golf balls with the greatest number of dimples will travel the furthest • Alternate Hypothesis H(a)1- The dimpleless golf ball will be the most accurate. Lab Test • Null Hypothesis H(o)- The golf balls will all have the same drag force. • Alternate Hypothesis H(a)- The drag force will decrease as the numbers of dimples increase. • Alternative Hypothesis H(a)- The dimple characteristics of hexx, smooth, steep, and dimpleless will yield progressively greater drag forces.

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