I am trying to plot u-velocity at a point (the center of cavity) as a function of time. I can not find the way to do it in Fluent. Can someone help?

I am also interested in temporal convergence study of the cavity problem

From what I've done, it seems you need to create a boundary zone with a point. Under Boundary conditions you always get to see "zone". Once you have creatde a "point" zone, should be able to view it under boundary condition. To create a "point" zone, on the pull down menu, simply go to SURFACE\POINT. Then under SOLVE, you can either use MONITOR or ANIMATE options to display you velocity change.