A microfluidic constriction is checked by equal volumetric flow. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Narrower channel carries faster flow

The upstream area is 2 square metres and the speed is 3 m/s.

Aup=2 m2,vup=3 m/sA_{\text{up}}=2\ \text{m}^{2},\quad v_{\text{up}}=3\ \text{m}/\text{s}
Continuity budgetFlow before and after the channel change is checked.areaspeedareaspeed

Flow is area times speed on both sides

Both products give 6 cubic metres per second. The claim is continuity only, not pressure drop or viscosity.

Aupvup=Adownvdown=6 m3/sA_{\text{up}}v_{\text{up}}=A_{\text{down}}v_{\text{down}}=6\ \text{m}^{3}/\text{s}
Continuity budgetFlow before and after the channel change is checked.areaspeedareaspeed