Final answer:
The Poiseuille flow rate describes the laminar flow rate in circular pipes, proportional to the pressure difference and to the fourth power of the tube's radius, and inversely proportional to the tube length and fluid viscosity.
Step-by-step explanation:
The Poiseuille flow rate describes the flow rate in circular pipes. Specifically, it is an equation that applies to the laminar flow of an incompressible fluid with a certain viscosity through a tube of a given length and radius.
Flow rate (Q) is dependent upon and directly proportional to the pressure difference (P₂ - P₁) along the tube and inversely proportional to both the length of the tube and the fluid's viscosity. Importantly, the flow rate is significantly affected by the radius of the tube, with an increase in flow rate to the fourth power of the radius.
This relationship is captured in Poiseuille's law, which is critical in various applications such as medical intravenous (IV) systems and various engineering fluid dynamics scenarios.