Bowed rotor

[msbbarratt]

The bow is the result of thermal convection within the case - warmer air rises to the top. If one were to "tickle" the starter for a few seconds, some xx minutes after shutdown, it would stir up the air and randomize the rotor positions, thus causing the bowing to be somewhat reversed.

You wouldn't even have to move much air. All that would be required is that all the shafts are kept turning, even very slowly, to allow heat dissipation to be uniform around the shafts. That way there'd be no bowing at all.

You often see engines windmilling whilst the aircraft is on the stand. That's probably not quite going to achieve the desired result; the auxiliaries must stop the one of the shafts turning, leaving it to soak in the heat.

[tdracer]

I'm guessing a small motor on the engine gearbox would be capable of turning the HP shaft, problem is it would have to turn the fuel pump, oil pumps, hydraulic pump(s) etc. This small motor is suddenly getting bigger.

I don't recall the size of the proposed rotisserie motor on the GE9X, but's quite small (yes, gearbox mounted, with a BIG gear reduction). It's only intended to turn the shaft at something less than 1 rpm so it doesn't take much torque.
More critical is the one way clutch - otherwise that little motor would be going a zillion rpm at redline N2..

[fruitloop]

IAE V2500 also suffers from "bowed rotor effects" Mainly the A1 variant..