Investigation on the cyclostationary force of propeller induced by spatially non-uniform turbulent inflow

The unsteady thrust generated by a propeller ingested spatially non-uniform turbulent inflow is characterized as a cyclostationary stochastic process. This phenomenon has the potential to cause additional wear and noise in the propeller-shafting system. In this study, the cyclostationary propeller forces are investigated through both theoretical and experimental approaches. Theoretically, the non-stationarity of cyclostationary forces are characterized using double-frequency spectrum analysis. The modulated correlation function method to calculate these cyclostationary forces is proposed. Our calculations indicate that the double-frequency spectral energy of cyclostationary propeller forces is concentrated along the diagonal spectrum lines. Experimentally, the unsteady forces of a DTMB 4382 propeller operating in a five-period grid-generated flow field are measured. Comparison with our theoretical calculations reveals that the modulated correlation function method accurately predicts the "humps", with a bandwidth deviation of less than 8% and an amplitude deviation of less than 5.2 dB at the first blade passing frequency.