Introduction
Everyone can agree that skiers are faster down the mountain than snowboarders, but how much faster? This article will look at the drag difference between the two styles. The skier has a big advantage facing forward in that it can decrease its frontal projected area (area projected onto a plane) by bending at the knees and waist while the snowboarder’s area remains constant whether the knees and waist are bent or not. In this model, the skier has a frontal area of about 3.0 ft2 while the snowboarder is 3.78 ft2.
Results
A CFD analysis was set up to compare the drag between the two different positions up to 60 MPH. Figure 1 below shows the high-pressure areas of each person. The snowboarder has a more high-pressure area than the skier. This creates the majority of the drag force (the other component is skin friction).
Figure 2: Static Pressure (Gauge)
Figure 4 shows the drag over a range of airspeeds. At all wind speeds, the snowboarder has about 2x the total drag of the skier. A cause of the snowboarder’s higher drag is due to the inability to reduce his frontal area. However, the main cause for higher drag is that the snowboarder also has a vertical/flat surface (high drag coefficient) that is not very aerodynamic compared to the skier (see Figure 3). There is not much that can be done to help the snowboarder become more aerodynamic.
Figure 3: Side View Showing Aerodynamic Shape
Figure 4: Drag vs Speed
Other than just comparing the total drag force, another way to compare the two shapes is by drag coefficients. This is essentially a drag efficiency that normalizes the drag forces and compares the pressure force so that the frontal area can be ignored. The snowboarder has a drag coefficient of 0.85 while the skier is 0.59 (an increase of about 45%). So even with a similar frontal area, the snowboarder would still have more drag than the skier (due to the inability to create an aerodynamic shape).
Figure 5: Two Snowboarders at Aspen, CO (the one in black may or may not be me)
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