Unexpected vibrations on a cylindrical filter made of nonwoven fabrics were clarified
experimentally. Two types of filter with length L¼1.8 m and 3.7 m, both 45 cm in
diameter and 1.08 mm in thickness, were used. This is a new type of aeroelastic
vibration phenomenon because the filter is a closed cylindrical vessel. In addition, the
flow velocity of inner air was very slow and inner air flowed out slowly from the filter
surface. The velocity distribution of air flow from a fan duct as well as the frequency and
amplitude of the filter vibration were measured for two types of filter. By setting up a
roll core panel at the outlet of the fan duct, we could rectify the outflow and suppressed
the vibration of the shorter filter with L¼1.8 m. However, this method was not
adequate for the longer filter with L¼3.7 m, and we could suppress the vibration by
shielding the inner surface of the filter at the top region.