Sports fluid mechanics should pay attention to Date:2014-08-08 11:16
Body dynamic effect. For example, if the "lift" of the freestyle palm is in the forward direction, the "lift" of the rotating sphere is lateral, and the "lift" of the car's tail is even downward. This is because the racing wheels need to maintain enough contact with the track during high-speed movement to continuously provide the driving force. The resistance of the air flow to the plate and the swing of the lift generated by the swing of the swirling ball generated by the turbulent swirling ball generate vortices and impulses. The reaction force of the fluid. Using the lift theory (Bernoulli's Law) Although it is possible to understand the causes of the majority of human or sports machinery's motive power in fluids, there are some phenomena that are difficult to directly explain using Bernoulli's law. For example, the propulsive force of free kicks, butterfly strokes, and backstrokes. There is also a swift swimming in which the athlete wears an ankle like a dolphin's tail to play the game. When he swims in, he does not move his hands. He uses his waist to push the leg and then drives the heel to swing up and down. It swims faster than the freestyle. In the process of swinging up and down the ankle, similar to the tail fins of fishes and dolphins, the deformation is more obvious. According to the hydrodynamic analysis of aquatic organisms, efficient methods of swinging forces generated during propulsion, such as marine mammal whales, dolphins and the fastest fish tuna, swordfish, etc., are all in flight with birds. The aerodynamics on the wings are similar. Through research in hydrodynamic tanks, it has been found that vortices are generated when swinging. This is similar to limping and the lower limb movements of freestyle, butterfly, and backstroke. Take Qiyong for example. When the ankle is in the highest position, hit the water downwards, creating a counterclockwise vortex, giving the back of the water a backward impulse, so the water gives the body a forward reaction; when the ankle is in the lowest position, hit the water upwards. A clockwise vortex is generated, giving the water above the bowl a backward momentum, so the water gives the body a forward reaction force, which is the propulsive force when swimming. On the other hand, when the fluid flows through an object, under certain conditions, there will be a resistance to periodic changes in the Karman vortices. In the above analysis, the direction and arrangement of the vortexes of the tail vortexes are opposite to those of the Karman vortex, so the Karman vortices For resistance, it is dynamic when swimming. Here, we can view the role of vorticity dialectically: On the one hand, because the propulsive force is proportional to the strength of the vorticity, it is necessary to ensure a certain vortex strength to ensure that the generated thrust is sufficient to overcome the resistance; on the other hand, due to mechanical energy Losses are proportional to the square of the vorticity, so excessive vortices should be avoided to reduce energy losses. In summary, according to the analysis of fluid flow properties and resistance and propulsive forces, the following points should be noted in the application of fluid mechanics: the resistance of flow should include inertial resistance. This is due not only to the fact that the movement of the human body and the sports equipment in the fluid is almost a variable speed movement, but also because the magnitude of the inertial resistance is also considerable. The way to reduce the inertial resistance is to maintain the continuity of the action and minimize the change in speed.
Body dynamic effect. For example, if the "lift" of the freestyle palm is in the forward direction, the "lift" of the rotating sphere is lateral, and the "lift" of the car's tail is even downward. This is because the racing wheels need to maintain enough contact with the track during high-speed movement to continuously provide the driving force. The resistance of the air flow to the plate and the swing of the lift generated by the swing of the swirling ball generated by the turbulent swirling ball generate vortices and impulses. The reaction force of the fluid. Using the lift theory (Bernoulli's Law) Although it is possible to understand the causes of the majority of human or sports machinery's motive power in fluids, there are some phenomena that are difficult to directly explain using Bernoulli's law. For example, the propulsive force of free kicks, butterfly strokes, and backstrokes. There is also a swift swimming in which the athlete wears an ankle like a dolphin's tail to play the game. When he swims in, he does not move his hands. He uses his waist to push the leg and then drives the heel to swing up and down. It swims faster than the freestyle. In the process of swinging up and down the ankle, similar to the tail fins of fishes and dolphins, the deformation is more obvious. According to the hydrodynamic analysis of aquatic organisms, efficient methods of swinging forces generated during propulsion, such as marine mammal whales, dolphins and the fastest fish tuna, swordfish, etc., are all in flight with birds. The aerodynamics on the wings are similar. Through research in hydrodynamic tanks, it has been found that vortices are generated when swinging. This is similar to limping and the lower limb movements of freestyle, butterfly, and backstroke. Take Qiyong for example. When the ankle is in the highest position, hit the water downwards, creating a counterclockwise vortex, giving the back of the water a backward impulse, so the water gives the body a forward reaction; when the ankle is in the lowest position, hit the water upwards. A clockwise vortex is generated, giving the water above the bowl a backward momentum, so the water gives the body a forward reaction force, which is the propulsive force when swimming. On the other hand, when the fluid flows through an object, under certain conditions, there will be a resistance to periodic changes in the Karman vortices. In the above analysis, the direction and arrangement of the vortexes of the tail vortexes are opposite to those of the Karman vortex, so the Karman vortices For resistance, it is dynamic when swimming. Here, we can view the role of vorticity dialectically: On the one hand, because the propulsive force is proportional to the strength of the vorticity, it is necessary to ensure a certain vortex strength to ensure that the generated thrust is sufficient to overcome the resistance; on the other hand, due to mechanical energy Losses are proportional to the square of the vorticity, so excessive vortices should be avoided to reduce energy losses. In summary, according to the analysis of fluid flow properties and resistance and propulsive forces, the following points should be noted in the application of fluid mechanics: the resistance of flow should include inertial resistance. This is due not only to the fact that the movement of the human body and the sports equipment in the fluid is almost a variable speed movement, but also because the magnitude of the inertial resistance is also considerable. The way to reduce the inertial resistance is to maintain the continuity of the action and minimize the change in speed.
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