The amount of friction depends on the fluid viscosity and the velocity gradient (that is, the relative velocity between fluid layers). The velocity gradients are set up by the no-slip condition at the ...

Some fluid near the wall actually reverses direction ... So when a turbulent boundary layer enters a region of adverse pressure gradient, it can persist for a longer distance without separating ...

As the dialysis fluid has no urea in it, there is a large concentration gradient - meaning that urea moves across the partially permeable membrane, from the blood to the dialysis fluid ...