Which of the following is NOT an assumption of Darcy's Law?

• A. Turbulent flow
• B. Laminar flow
• C. Incompressible flow
• D. Steady state

Answer: (C)

Darcy's Law describes a linear relation between seepage velocity and the pressure gradient for flow through a porous medium under conditions where viscous forces dominate and inertial effects are negligible. That means the flow is laminar, the fluid density is effectively constant (incompressible), and the process is steady so storage effects don’t complicate the relationship. If the flow becomes turbulent, inertial effects rise and the simple linear relationship no longer holds, so Darcy's Law in its basic form isn’t valid in that regime. Since laminar flow, incompressible flow, and steady state align with its standard assumptions, the condition that does not fit is turbulent flow.