At a sudden contraction in a pipe the diameter changes from d1 to d2. the pressure drop, δp, which develops across the contraction is a function of d1 and d2, as well as the velocity, v, in the larger pipe, and the fluid density, and viscosity, use d1, v, and as repeating variables to determine a suitable set of dimensionless parameters. why would it be incorrect to include the velocity in the smaller pipe as an additional variable?