Experimental identification of whirl flutter characteristics in a small-scale rotor rig

This paper presents the development of a small-scale unpowered experimental test rig with a bladed rotor along with its dynamic model. The novel attributes of this work are: (1) the use of a compact portable vertical wind tunnel and with the pendulum-like accelerometer-instrumented rotor rig, (2) assessment of the in-operation vibrations and whirling dynamics for future use in the large scale experiments, and (3) analysis of the rig-specific rotor dynamics phenomena. This work experimentally and numerically studies the proposed rotor rig with the main emphasis on its modal characteristics. Owing to its design characteristics, it is shown analytically and experimentally, that the rig features four dominant lateral backward and forward whirling vibration modes in relatively wide frequency range during its windmilling operation. Consequently, it is determined that the rotor rig represents a useful simplified low order system suitable for studies of a range or dynamic phenomena such as transient resonance crossing, whirl flutter and geometric nonlinearity effects.