FLUID FLOW IN PIPES

U$3\mathrm{.}1$ The differential U$-$manometer filled with water having $20C$ measures the pressure drop in a pipe through which oil with a density of $819kg*m^{-3}$ flows. The oil also fills the tubing connecting Umanometer with measuring spots and is in direct contact with the water in the manometer. The left and right tubes of the U$-$manometer are $0\mathrm{.}7m$ long and have an inner diameter of $6mm$ and $8mm,$ respectively. The height of the water is $0\mathrm{.}30m$ in both manometer arms when the pressures are equal. What is the maximum pressure difference that can be measured if the smaller diameter pipe is connected to the point of higher pressure? How does this maximal pressure difference change if we connect a larger diameter pipe to this point?

Result: When the smaller tube is connected, the maximal pressure difference is $0\mathrm{.}82$kPa. In the other case, the pressure difference is $1\mathrm{.}2$kPa.