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As the radius decreases, the slope increases and so does the azimuthal velocity of the fluid, reaching its peak at around 5cm. This radius approximately corresponds to the location of the edge of the can before it was removed. We would expect the pressure gradient at this radius to be largest, which implies fluid at this radius should also have the largest velocity (see equation yequation 3.2). At small radii, the azimuthal velocity decreases again as the frontal boundary flattens and the pressure gradient decreases.
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