Consider molasses flow in a pipe from point 1 to point 2 in which the pressure drops by ?p when the diameter is reduced from radius r1 to radius r2. The pressure drop is a function of the dynamic viscosity, the fluid density, and the velocity in the smaller pipe.
(a) Use the radius r1, the velocity V2, and the viscosity ? as a repeating variable and determine a suitable set of dimensionless parameters.
(b) Why would it be incorrect to use the velocity in the larger pipe V1 as an additional variable?
(c) An engineer would like to make a physical model of the molasses flow but use water instead of molasses. How much would the velocity and the radius of the pipe have to change to keep the flow dynamically similar
(i.e., to keep the value of the pi groups equal? Assume the pressure drop is to remain the same in both cases.)