Vascular resistance is a fluid layer in which at a distance δ, viscosity η is a function of δ written as η(δ), and these surrounding layers do not meet at the vessel centre in real blood flow. Instead, there is the plugged flow which is hyperviscous because holding high concentration of RBCs. Thurston assembled this layer to the flow resistance to describe blood flow by means of a viscosity η(δ) and thickness δ from the wall layer. The blood resistance law appears as R adapted to blood flow profile : where Blood resistance varies depending on blood viscosity and its plugged flow
Incompressible flow to ensure incompressible "flow". When we speak of the partial derivative of the density with respect to time, we refer to this rate of change within a control volume of "fixed position". By letting the partial time derivative of the density be non-zero, we are not restricting ourselves to incompressible "fluids", because the density can change as observed from a fixed position as fluid flows through the control volume. This approach maintains generality, and not requiring that the partial time derivative of the density vanish illustrates that compressible fluids can still undergo incompressible flow. What interests us is the change