Modelling bristle behaviour in rotating brush duct cleaning

The bristle of a rotating cleaning brush for air ducts was modelled using large deformaion elastic theory. The point collocation method with a trial solution consisting of undertermined parameters was employed to discretize the resulting non-linear problem. The main interest was in determining the value of the bristle tip contact normal force N, the bristle tip contact angle B and the torque T needed to rotate a brush. The results obtained using the simple model were compared with the results obtained from a laboratory test.
The simulated and experimental results show that the magnitude of the normal force and the contact angel increase as a function of the rotation speed n. The results show further that air drag increases the torque and somewhat decreases the contact force between a bristle tip and the duct surface. Howerver, with the normal properties of a brush, air drag only slightly affects the deflections of the bristles at practical rotating speeds.
To facilitate possible brush design work the problem was also studied employing a dimensionless formulation. The parameters that affect the magnitude of the normal force and the contact angle are five dimensionless numbers.