Flow rate, Poiseuille’s equation, and velocity

[September24]

According to Poiseuille’s equation, increasing the radius of an object (and thus increasing area) increases the flow rate of a fluid. I also believe that if velocity increases, Flow rate ALSO increases according to the continuity equation (Av1=Av2). However, according to the same equation, larger area= slower speed. I thought that increasing radius or area would increase flow and speed? This has always confused me.

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[apopz]

you need to understand that flow and velocity of fluids are two separate things. The reason this equation works, is because the amount of fluid that passes through the system is the same in both locations (the wider and smaller areas of the pipe). In order for the same amount of fluid to pass through a smaller area, the velocity must be higher. In the section of the pipe where the area is greater, the velocity of the fluid does not have to be as great to move the same amount of fluid through it.