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    The Visit

    On the 28th January 2010, the AS Physics class visited Queen Mary’s University of London, specifically the school of engineering and material science. Whilst there, we participated in a programme called ‘The Greening of Road transport’ as well as being lectured on the benefits of studying aero-nautical engineering and told of the rich history of the university’s involvement in the field (the first aeronautical engineering department in the UK was opened at Queen Mary’s in 1908.) We were also informed of exciting new developments in technology that allow computational aerodynamics to be studied in order to predict the flow around an object such as a shuttle.

    Experiments

    We viewed three different experiments being carried out all related to the physics principle of the force drag and its effects. When solids and fluids move relative to each other, the fluid’s layer that is beside the solid exerts a frictional force upon it (successive fluid layers also exert forces between each other.) These frictional forces cause viscous drag. Stokes Law states that the viscous drag (F) of a small sphere in relatively low speeds, in laminar flow is: F=6πηrv where r is the sphere radius, v the velocity of it and ηthe viscosity of the fluid.

    The effect of surface roughness on drag

    Four different balls (a golf ball, a ping-pong ball, one large dimpled ball and one large smooth ball) were placed in front of a wind tunnel, (air flows thus is a fluid) the wind was then blown at 2 different speeds for each ball, the drag force they experienced was measured and recorded.

    In all cases, when the speed of the air was increased, the drag increased too.

    (TABLE WITH RESULTS HERE)

    Moreover, the golf and large dimpled ball had a lesser drag due to the dimples on their surface, these cause the boundary layer on the upstream side of the ball to change from laminar to turbulent. The turbulent boundary layer remains affixed to balls’ surface for a longer period of time than a laminar boundary and so creates a narrower, lower pressure thus there is less drag.



    Any help would be very much appreciated! XxxX
 
 
 
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