Meaning
Mathematical expression for fluid velocity at a solid boundary where the slip speed depends on the shear stress raised to a specific power. The power-law slip model replaces the traditional no-slip assumption for complex fluids like polymer melts or suspensions. It accounts for the loss of adhesion between the fluid and the wall surface during high pressure extrusion.
Boundary Condition
Slip velocity is calculated by multiplying a slip coefficient by the wall shear stress. In the power-law slip model, this relationship is non-linear and reflects the molecular interactions at the interface. The value of the slip exponent determines whether the slip increases or decreases relative to the applied force.
Physical Property
Material traits are captured by the consistency and the sensitivity of the fluid to deformation. A higher index in the power-law slip model implies a greater deviation from linear behavior. These parameters are derived from capillary rheometry data or specialized surface experiments.
Surface Friction
Reduced resistance at the wall leads to a flatter velocity profile across the pipe diameter. The power-law slip model predicts a decrease in pressure drop when compared to standard flow equations. This effect is essential for reducing energy consumption in heavy duty pumping systems.
Without accounting for this slip, a production line might suffer from unexpected pressure surges or surface defects like sharkskin. The model establishes the limits of throughput before the onset of flow instability.
