# Viscous Drag on a spinning shaft

Tags: drag, shaft, spinning, viscous
 P: 9 I am designing a test rig for my company to test seals. What i have is a shaft spinning in a fluid column that is pressurized to 30 bar. The shaft is spun by a motor and i am currently trying to figure out what motor i should select. The fluid is a C4 SAE 30 Oil, quite viscous actually. My intuition tells there will be hydrodynamic friction due to the shafts rotation and hydrostatic forces due to 30 bar pressure creating more friction. Can you guys tell me how to figure this out? In brief the question is - - 80 mm shaft spinning at 3000 RPM inside a 100mm cylindrical fluid column - The fluid is SAE 30 Oil - The oil is pressurized to 30 bar What is the frictional torque on the shaft ? What is the Power and Torque required by my prime mover (P = Tw anyway ;) ) Thanks in advance. Any help will be appreciated a lot bros :)
 Sci Advisor HW Helper Thanks PF Gold P: 5,216 What's the viscosity of the oil? Does it vary with shear rate? What's the length of the shaft? You may also need to consider whether viscous heating is going to be a factor. You can get an upper bound to the torque by neglecting the viscous heating. Is that acceptable? Chet
P: 9
 Quote by Chestermiller What's the viscosity of the oil? Does it vary with shear rate? What's the length of the shaft? You may also need to consider whether viscous heating is going to be a factor. You can get an upper bound to the torque by neglecting the viscous heating. Is that acceptable? Chet