It is important to understand that the magnitude of the frictional force on a layer of fluidįlowing over some surface depends on the speed that the fluid flows with over the surface. We see then that friction between layer I and layer II reduces the velocity of layer II andįriction between layer V and layer IV reduces the velocity of layer IV. There is then viscous friction betweenĪdjacent layers of a fluid that have unequal velocities. Objects that are in contact moving past each other. When two adjacent layers of the fluid do not have the same velocity, this is equivalent to two The viscosity of the fluid does not only produce viscous friction where the fluid is in contact The frictional forces on layer I and layer V reduce the velocities of these layers. Object, but we can model it as an object on which frictional forces can act. It may not be obvious to think of a layer of fluid as an Like all frictional forces, viscous frictional forces act on a moving object in the oppositeĭirection to the motion of the object. The container (layer I and layer V) are acted on by viscous frictional forces between theįluid and the inner surface of the container’s wall. If the fluid in the container has nonzero viscosity, then the layers in contact with the walls of The fluid is modeled asįlowing continuously without any such starting or stopping points. Such points would involve changes to the velocity of the flow. This is done to avoid the need to consider points at which flow starts or stops, as Parallel to the flow direction, no such boundaries are shown perpendicular to the flowĭirection. It is important to appreciate that although we can now see definite boundaries to the flow

Laminar flow examples