$4\mathrm{.}6\mathrm{.}29$ Water flows through the pipe contraction shown in Fig. P$4\mathrm{.}6\mathrm{.}29.$ For the given $0\mathrm{.}2-$m difference in the manometer level, determine the flowrate as a function of the diameter of the small pipe, $D.$

FIGURE P$4\mathrm{.}6\mathrm{.}29$