When channel flow encounters a "bump" the flow tends to accelerate, as you noted. The degree of acceleration depends on the geometry of the bump. A phenomenon closely related to this is a transonic airfoil. In vehicles that travel at high subsonic speeds, the flow over the wing accelerates to supersonic speeds and a normal shock is formed on the wing. Try doing some research on transonic airfoils; you may have better luck there. I can tell you that there are plenty of articles out there on both transonic flow over bumps and transonic airfoils. Try doing a literature search (text books are a good start, but probably won't have detailed information). The more simple articles will likely be old (I would guess 1960's to 1970's).
In terms of the physics, the phenomenon is relatively simple. When the flow encounters the bump, it accelerates, and depending on the freestream Mach number, the flow may become supersonic at a Mach number slightly higher than unity. Bumps, depending on their geometry, accelerate the flow only slightly, so the Mach number of the incoming flow must be relatively high to lead to supersonic flow. Since transonic flow is relatively unstable, a shock wave forms readily, and it forms at the most stable place: the top of the bump. This makes sense, since the boundary layer is likely to separate at this location (and since the flow will decelerate after the bump as well), thus making it a "preferred" and relatively stable location for the shock wave.
Haf
