In: Other
We have a narrow slit that is oriented vertically. The thickness of the slit is 2B. The width, W, and the length, L, of the slit are both much larger than the thickness. A fluid is being forced through the top of the slit and runs out of the bottom. Determine the shear stress and velocity distribution through the slit. Sketch the shape of the velocity profile based on the velocity distribution you obtained. Determine the maximum velocity of the fluid within the slit and where within the slit it occurs. Find the analog of the Hagen-Poiseuille equation for this system.
velocity profile for narrow slit at x and y direction are zero |
From continuity equation |
Momentum balance |
momentum in (z=0) = |
momentum out ( z=L) = |
Momentum in through viscous fluid flow (x=x) = |
Momentum out through viscous fluid ( x=x+Δx) = |
Force due to Pressure (z=0) = |
Force due to Pressure ( z=L) = |
Force due to Gravity = |
From the basic momentum balance equation |
From the Newton’s law of viscosity |
Integrate the equation |
Apply the boundary conditions |
At x=0 |
At x=B |
velocity profile in narrow slit |
Now calculate the mass flow rate of the fluid |
Mass flow rate = density x Volumetric flow rate |
Average velocity = (Volumetric flow rate) / (Area) |
the analog of the Hagen-Poiseuille equation for this system. |