V Drag Soccer
Kylee Evancho
Pick your team and get ready for some mini soccer action. Tap/click and drag behind the player to set their speed and their direction. Each turn, you have three chances to score a goal. But don't think too long about your shot, or you'll get a penalty. How many goals can you score in 119 seconds of play?
As an object moves through the air, the air resists the motion ofthe object. This resistance is called aerodynamic drag. Drag is present on all objects moving through the air fromairlinerstobaseballs.Drag is the component of theaerodynamic forcethat is aligned and opposite to the flight direction.On this page we will discuss some of the details of the drag on a soccer ball.
The details of how a moving soccer ball creates drag are fairly complex.If we move with an object through the air, the object appears to stand still and theair moves past the object at the speed of the object.Next to the surface of the object, the molecules of the air stick tothe surface, as discussed in the properties of air slide. This thinlayer of molecules pulls on the surrounding flow of air.The relative strength of the inertial (momentum)andviscous forces in the flow determines how the flow moves around theobject and the value of the drag of the object. The ratioof the inertial force to the viscous force is called the Reynolds number.The equation for the Reynolds number is:
Unfortunately, the state of the boundary layer is not the onlyfactor that determines the drag on an object. Size ,shape ,andatmospheric conditionsalso affect the value of the drag. To predict the value of drag, aerodynamicistsuse thedrag equation:
where D is the drag, A is the cross-sectional area, andcd is thedrag coefficienta number that represents all of the complex factors affecting drag.Drag coefficients for a specific object aredetermined experimentally using a model in awind tunnel.
For flow past a ball, determining the drag coefficient gets a little moreconfusing. The drag on a ball is being generated by the boundary layerseparating from the back of the ball. As the flow separates, it creates a viscous wake behind the ball. A large, wide wake generates a large amount of drag;a thin wake produces less drag. The thickness of the wake, and thedrag on the ball,depends on the conditions in the boundary layer which, as we have seen, dependson the Reynolds number. For the graph on the right of the figure, we show some experimental data for a smoothball (solid line). The drag coefficient has a high value at low Re values, then drops down toa lower value from which it continues to increase with increasing Re.The interpretation of the curve is that, at lower Re values, the boundary layer is laminarand the wake is thick. As Re increases, the boundary layer transitions to turbulent, which initiallyproduces a thinner wake, but with increasing speed and Re, the wake thickens and the drag increases.
For a soccer ball, the diameter is .75 feet, sea level static air density is 2.37 x 10^-3 slug/ft^3, viscosity coefficient is 3.61 x 10^-7 slug / ft sec and, if the ballis kicked at 40 mph, the value of the Reynolds number is approximately:
But we know that a soccer ball is not a smooth ball. The stitches on the ball produce surface roughness that disturbs the boundary layer, causing the boundary layer totransition at a lower value of the Reynolds number than for a smooth ball. We show a second line on thegraph that is more representative of a rough surfaced soccer ball (dashed lines).From this graph, the value of the drag coefficient for a soccer ball is approximately:
This is the value of drag coefficient that is used as the default in theSoccerNASA simulation program. Within the program you can re-set the value to another value to see the effects of drag on thetrajectory of the kick.
The new book is all about the history of drag, so I had to really think about that in terms of costume change and what represented drag, going back to ancient Greece. I went as far back as I could find.
We conducted a simple 2D flight simulation to compare the effects of the drag coefficients of the Jabulani and the Tango 12 on their flight distance and flight trajectory (Goff and Carr 2009). The occurrence of irregular and unsteady Asai and Kamemoto 2011 flying with no spin or a low-speed spin (Asai and Kamemoto 2011). However, because this study focused on the relationship between the constant resistance of the ball and its flight trajectory, knuckle effects were ignored in the trajectory simulation. In the trajectory simulation we estimated the drag coefficient with respect to the Reynolds number using a cubic curve to calculate the two-dimensional coordinates of the ball. Therefore, we omitted the lift and side forces acting on the ball. We considered the effect of buoyancy on the flight trajectory to be negligible compared to the effect of drag; therefore, we omitted the buoyancy from our calculations. By using the relationship between the Reynolds number and the drag coefficient, which were measured in the wind tunnel experiment, we calculated the initial ball velocities of the two-dimensional flight trajectory to be 17 and 28 m/s, respectively; the ball was launched at an angle of 25 in both cases. We also computed the two-dimensional flight trajectories of the Jabulani (initial speed: 17 and 28 m/s) and the Tango 12 (initial speed: 17.4 and 28.7 m/s) under the condition of ball impacts having the same impulse (17 m/s: 7.45 kg/s; 28 m/s: 12.26 kg/s); in doing so, we considered the difference in mass of the Jabulani (0.438 kg) and the Tango 12 (0.428 kg).
In the flight trajectory simulation, the Tango 12 flew 2.0 m farther than the Jabulani when the initial velocity was 17 m/s, but it flew 3.0 m lesser when the initial velocity was 28 m/s. Similarly, in simulations with ball impacts having the same impulse (7.45 and 12.26 kg/s), the lighter Tango 12 flew farther. In the medium-speed region, where the coefficient of resistance of the Tango 12 was small, the difference in flying distances was as large as 2.9 m. However, in the high-speed region, where the coefficient of resistance of the Tango 12 was large, the difference in flying distances was reduced to 1.4 m.
These results suggest that the Tango 12, one of the newest soccer balls, has less air resistance in the medium-speed region than the Jabulani and can easily acquire large initial velocity in this region. In other words, this ball can easily gather speed in the frequently used medium-speed range, and therefore, it should be relatively suitable for a passing-based game of soccer.
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The Park Drag Soccer Club began at IWU in 1998. University staff and international students began to play pickup games before eventually opening membership to ISU staff and international students. As it grew in numbers, the Park Drag Soccer Club remained a place for anyone far away from home who loved to play soccer. The group has met at various locations over the years to play, including the detention basin in Normal off Linden Street and Park Drag Lane, thus the club name.
Each contribution in the IWU exhibit will bring a new perspective for the community and will connect each attendee to different cultures. Enlarged postage stamps represent each member from over 30 countries. Additionally, interviews will include the experiences a player has had being a part of the team.
First off, this is a fucking hilarious video. Dude is just getting ragdolled out there while faking an injury. Good. It's the worst thing about soccer by far. I love the sport, but we can't have this be going viral. It's a bad look for us who scream that flopping and faking injuries happen in every sport. Can't have a dude getting dragged around and defend it. I want to say I admire the dedication to the bit, but all it does is open up everyone saying soccer players are soft, can't watch the sport, etc. Can't have it! Won't have it!
Back to the video, I love the goalie from the opposing team going for the legs. Gotta prove a point and he treats the 'injured' like a little kid. Good. We should be publicly embarrassing anyone who fakes an injury - whether it's a court storm, on the soccer field or anything else. They deserve to be publicly mocked. What makes it even worse? I've blogged about Botafago before:
Can't claim corruption in Brazil (no duh) and then have your guys do this. You gotta go the opposite way. Embrace being the enforcers and getting fucked over. Start throwing shoulders around and go cleats up from time to time on a slide tackle. Or if you're going to go this way, you gotta go even harder. All 11 guys on the field fake an injury at the same time and start having the bench drag them around. One guy is pathetic, all 11 proves a point. Gotta hold your face like this guy too. Really lean into the bit of faking injuries.
But yeah, this is everything wrong with the sport. I don't care about games being 2-1 or anything like that. I don't even care about the clock not stopping and counting up instead of down. This is more egregious than goals going away because of VAR and seeing a fingernail offsides.
Rick Gardner is a lifelong resident of Bloomington, ISU alum, and retiree. He was introduced to soccer during his freshman year of high school in the fall of 1971. He coached boys soccer in the PCSL and CIYSL in the 1990s. He has been playing pickup soccer in Bloomington-Normal for close to 20 years. He organizes the games for the Park Drag United pickup soccer group and is the de facto activities director for the group.
Rabah Seffal retired from Caterpillar after a 24-year career as an engineer. Born in Algeria, he is a resident of Bloomington since 1998. His two daughters attended Bloomington High School where the youngest played soccer. He played soccer in Algeria and in New Orleans where he went to college. He joined the Park Drag United soccer group more than 14 years ago and will continue to kick the ball, laugh, and dance after scoring a goal.
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