Hi I am trying to understand what forces are at work to slow a liquid flowing in a circular pipe As an example the above torus pipe fully filled with an incompressible low viscosity liquid. This is rotated until the fluid achieves solid body rotation and then the pipe is suddenly stopped but the low viscosity allows the fluid to continue under its own inertia I understand that a rotational flow pattern will be formed by the solid body rotation and the additional force of the solid container will prevent the formation of a free vortices ? is this correct ? While I understand that viscosity works to slow the flow , are there other forces due to the circular flow geometry that work against the momentum of the fluid ? Vorticity - degrades kinetic energy trapped in Circulation to heat ? Can it diffuse the flow momentum any other way ? Can either Axial Pressure Variation or - Body Forces The additional force applied by the solid container degrade the flow (some version of Minor Losses in a pipe) effect how fast the momentum is dissipated ? Additionally would the answer be different if the pipe wasn't fully filled with an incompressible liquid ? Is there anything else I need to consider to how quickly the momentum would stop ? Any readings that someone could recommend ?