$5.$ Liquid$-$Liquid Flow: For a liquid$-$liquid system in a $1$ cm diameter pipe, where the dispersed phase occupies $25\%$ of the cross$-$sectional area and moves at a velocity $30\%$ higher than the continuous phase, calculate the drift velocity.

$6.$ Gas$-$Liquid Flow in Mini Channels: A mini channel experiences a gas$-$liquid flow where the gas flow rate is $0\mathrm{.}01$ kg$/$s and the liquid flow rate is $0\mathrm{.}05$ kg$/$s$.$ Given that the channel width is $3$ mm$,$ estimate the void fraction.

$7.$ Three Phase Flow Introduction: In a three$-$phase system $($gas$,$ solid, liquid$)$ with volumetric flow rates of $0\mathrm{.}02$ m$/$s$,0\mathrm{.}005$ m$/$s$,$ and $0\mathrm{.}015$ m$/$s respectively, calculate the volume fraction of each phase in a $50$ mm diameter pipe.

$8.$ Gas$-$Solid Liquid Contactors: For an agitated vessel containing a gas$-$solid$-$liquid mixture, where the gas volume fraction is $0\mathrm{.}1,$ solid volume fraction is $0\mathrm{.}2,$ and the liquid is the continuous phase, estimate the average bubble diameter assuming a spherical bubble shape.