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Laminar and Turbulent Flow. Laminar Flow – flow characterised by smooth parallel layers of the fluid Turbulent Flow – flow characterised by mixing of adjacent layers of fluid. . Physical Education and Health. Human Movement BIOMECHANICS PROJECTILE MOTION THROUGH AIR AND WATER.
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Laminar and Turbulent Flow • Laminar Flow – flow characterised by smooth parallel layers of the fluid • Turbulent Flow – flow characterised by mixing of adjacent layers of fluid.
Physical Education and Health Human Movement BIOMECHANICS PROJECTILE MOTION THROUGH AIR AND WATER
Wind tunnel testing http://www.youtube.com/watch?v=WTKwA9hrV_Y
Buoyancy • Buoyancy – is a force that acts vertically upwards on a body that is immersed in water. • The buoyancy force is equal to the weight of the fluid that is being displaced. • Affected by density of fluid (salt v freshwater)
An objects ability to float is linked to its buoyancy and weight. When the are equal the object will float.
Drag Force • Drag Force – is generated when a fluid flows around a stationary object or when an object moves through fluid. As a result the object slows down. • Air resistance – drag force as a result of air flow around an object • Hydrodynamic drag – drag force as a result of water flow around an object
Bernoulli’s principle – as the velocity of a fluid flow increases, the pressure will decrease
Boundary Layer – the region of air directly around the object. • The smoother the surface the less energy lost as one layer of fluid flows over the other. The roughness of the surface increases the energy loss and increases the drag. Eg: skins, shaving down.
Lift Force • Lift force – a force acting on an object in a fluid in a direction perpendicular to the flow of a fluid. • Factors affecting lift force a similar to drag force • Velocity of the fluid • Density of the fluid • Size, shape and position Lift can occur due to – • Foil shape • Angle of object in relation to flow • The Magnus affect • Unevenness of a surface on one side of the ball
Foil Shape – simply a shape that can generate lift when in air or water. Fluid flowing over a curved shape flows faster then a flat surface causing a difference in pressure (Bernoulli’s Law) Formula 1 car v Planes • Angle of Attack – the angle between the long axis of the object or body and the direction of air or water flow. A positive angle is needed to create lift force. If too small or too large the regions of different pressure are not created a lift not generated.