Hydrodynamics. Fluid kinematics_Worksheet 1

Worksheet 1

Formative assessment

Application of Laminar and turbulent flow

1.      How is blood flow measured in a vessel?  

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2.      How can you predict whether a certain vessel will be bright or dark on an MR image?  

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3.      Question 3 related to football.  What is magnus effect in football? What causes a soccer ball to curve when kicked?

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4.      Explain working principle of boomerangs.

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5.      Home experiment. If you blow the bigger cone through the pipe, the smaller cone will be attract to the bigger one. Why?

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Mark scheme

1.      Vortex flow refers to localized swirling or stagnant blood flow that has separated from the central streamlines within a vessel. Such vortices, also called flow eddies, frequently occur at vascular bifurcations and distal to areas of stenosis.  Unlike turbulent regions, areas of vortex flow are composed of slowly moving currents and streamlines that are not random but are often countercurrent to the main flow direction.  Both turbulent flow and vortex flow create problems for MR angiography.

2.     

3.      The reason that spin on a football makes it curl is known as the Magnus effect. This causes a rotating ball to form a whirlpool about itself, with one side's air moving with the ball and the other side's air moving against the ball.

4.       The returning trajectory of a boomerang involves the aerodynamic lift of its airfoil shape plus the gyroscopic precession associated with its rapid spin. The precession redirects the airfoil so that it "flys" around the returning path. The three diagrams above address the nature of the boomerang's flight.

5.