# BME 590 - Homework 1

Due: Aug 24, 2017

1. In words, describe what the Reynolds number means (no equations allowed).

2. What is the Reynolds number for water flowing in a microchannel with an average velocity of 1 mm/s? Assume a characteristic microchannel length of 100 $$\mu$$m. List any other assumptions that you make.

3. Within the context of microscale fluid flow, explain what Purcell means by “Time, in fact, makes no difference…”

4. If you want to mix two solutions in a microchannel, is it better to stir or use diffusion? Why? Use numbers to justify your answer.