Fluid flow occurs throughout biomedical engineering ranging from air flow in the lungs to diffusion of nutrients through membranes and involves both in vivo and in vitro measurements. Flows involve fluid media in the form of gas, liquid, or multiphase flows of liquids and gas together or in combination with solid matter. They can involve relatively benign flows like that of saline through an intravenous tube to a biochemically active flow of a nonNewtonian fluid such as blood. Many biomedical or bioengineering processes require the quantification of some flow field that may be directly or indirectly related to the process. Such quantification can involve the measurement of volume or mass flow, the static and dynamic pressures, the local velocity of the fluid, the motion (speed and direction) of particles such as cells, the flow-related shear, or the diffusion of a chemical species.