In the linear form q = k a (p1 - p2) / (μ L), which term represents viscosity?

• A. μ (viscosity)
• B. k (permeability)
• C. L (length)
• D. a (cross-sectional area)

Answer: (A)

Flow through a porous path under a pressure difference follows a linear relation known as Darcy's law. In the equation q = k a (p1 - p2) / (μ L), the viscosity is represented by μ, which sits in the denominator. Higher viscosity makes the fluid more resistant to flow, reducing q for the same pressure drop, while lower viscosity allows more flow. The other symbols correspond to permeability, cross-sectional area, and the flow path length, respectively. Therefore, the term that represents viscosity is μ.