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CFD Simulation of Soccer Ball Knuckling
In baseball, a knuckle ball is often used where the pitcher doesn’t impart any spin on the ball and the Gods of Aerodynamics will take care of the rest. So what is knuckling exactly? When a soccer ball is kicked, the air flowing over the ball ‘hugs’ the ball tightly forming what is called a ‘boundary layer’ over the ball. The roughness of the ball and the depth of the seams will then affect this boundary layer which determines the motion of the ball. When a ball is kicked with little or no spin, the air flowing over the ball is ‘tripped’ by the seams and separates from the ball, forming a region of wake behind it. The unsteadiness of the wake behind the ball is what pushes it into an unsteady flight path. The ball may oscillate from left to right or up and down when kicked and the trajectory of such a kick is hard to predict for the kickers and goalkeepers alike. During knuckling, the unsteady wake behind the ball will oscillate in direction leading to lift and side forces on the ball moving from one direction to the other. Recently, researchers have shown that the Brazuca knuckles less at 50 mph, the average speed with which free kicks are taken and hence is better than the Jabulani.
My involvement in the World Cup is a little more personal since my first project at CD-adapco involved the aerodynamics of soccer balls. The 2010 World Cup ball, the Adidas Jabulani, had its fair share of criticism due to its shallower seams and 8-panel design leading to erratic flight paths. The ball was difficult to control for the players and rumors have it that some goalkeepers still have recurring nightmares of the ball. In 2010, CD-adapco teamed up with Wilson Sporting Goods to study the aerodynamic behavior of soccer balls and the impact of the newer panel designs.
Wake behind Adidas Brazuca ball at 50 mph - Side View
Wake behind Adidas Brazuca ball at 50 mph - Side View
The image shows a typical model where the 2D sector losses have been mapped on to a full revolution 3D body
Advanced Simulation for Electric Machine Design
Electric machines are ubiquitous across our everyday life - from automotive to domestic appliances, aerospace to industrial usage - these machines are the workhorse of industry and modern amenities. New regulatory efficiency requirements, fluctuating costs of permanent magnets, and the ever present goal of higher performance from a smaller package, increases pressure on both the design and optimization of electric machines across all applications. This webcast explores the many techniques used to predict electric machine performance, including analytic models, lumped parameter models based on...
I am not a soccer fan, but all the men in my life are fanatics and thus World Cup fever has taken over the Goodwin household. You might be surprised at what happens when an uninterested CFD engineer is forced to watch soccer...
Dancing Dice with Overset, DFBI and Contact Coupling
CFD simulation of dice roll in STAR-CCM+ v9.04 using Overset, DFBI and Contact Coupling.
During the opening session of the STAR Global Conference earlier this year, Didier Halbronn, CD-adapco Vice President of European Sales, spoke about our ongoing commitment in the field of multi-disciplinary design exploration (MDX). In this blog I want to highlight a couple of new features in v9.04 of STAR-CCM+ that approach this in different ways.
In an effort to make STAR-CCM+ even faster on a broader range of problem types STAR-CCM+ v9.04 (which is released next week) will offer Concurrent Per-Part Meshing (which is a bit of a mouth full, so we'll call it CCPM instead). Now, I'm sure you're asking yourself, ‘What’s the difference between CPPM and regular parallel meshing?’

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