The dynamic characteristics of the gas flow field in a reverse cyclone were investigated experimentally in this study by measuring instantaneous tangential velocity with hot wire anemometry (HWA). The instantaneous tangential velocity was found to continuously fluctuate by both low and high frequencies with time. Further analyses of measured data regarding time and frequency domains by standard deviation and spectral analysis revealed that the fluctuation intensities were stronger in the center region than that near the wall, and stronger still near the dust outlet. One dominant frequency (f(1)) prevailed in entire space of the cyclone and remained almost unchanged, while the power spectral density (PSD) of f(1) decreased significantly with increased radial position. To this effect, the low-frequency velocity fluctuation exhibited transfer behavior and attenuation characteristics. Besides, another dominant frequency (f(2)) generated by the hopper (the hopper led to a new fluctuation) and emerged just in the local region of the dust outlet. Analyses suggested that both dominant frequencies originated from the sway of the gas swirling flow, f(1) was from the cyclone, and f(2) from the hopper. The dominant frequencies also increased as Re increased, and in the cyclone with a hopper, the region affected by f(2) grew in size as Re increased. (C) 2020 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.