Need

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 http://www.dimpletape.com/article.htm 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 Laminar vs. Turbulent Flow Flow Around Smooth Sphere Flow Around Dimpled Sphere Figure 3 www.callawaygolf.com/Global/en-GB/Innovation/GolfBallTechnology/ HEXAerodynamics.html Figure 4 Figure 5 boojum.as.arizona.edu http://www.aviation-history.com/theory/lam-flo Figure 2- This picture shows the two types of flow around an object; laminar and turbulent. Laminar or streamline flow is when a fluid flows in parallel layers. The opposite of this flow is turbulent flow, which is when a fluid undergoes irregular fluctuations or mixing. Figures 3,4,and 5 all show the flow around different spheres. In figure 3 the wake around the smooth sphere is considerably larger compared to the dimpled or hexxgolf ball sphere. This larger wake increases drag. Figure 4 shows the flow around a dimpled sphere and the wake behind that ball is thinner meaning less drag. Finally in figure 5 the airflow around the hexxgolf ball is shown and exhibits an even smaller airflow, decreasing drag to an even greater extent. Literature Review Smooth vs. Steep Dimples (Kato, 2005) Smooth Dimples • Ogg, 2004- Development of the hexx ball • 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.