Despite their high manufacturing cost and structural deficiencies especially in tip regions,highly skewed propellers are preferred in the marine industry,where underwater noise is a significant design criterion.Howeve...Despite their high manufacturing cost and structural deficiencies especially in tip regions,highly skewed propellers are preferred in the marine industry,where underwater noise is a significant design criterion.However,hydrodynamic performances should also be considered before a decision to use these propellers is made.This study investigates the trade-off between hydrodynamic and hydroacoustic performances by comparing conventional and highly skewed Seiun Maru marine propellers for a noncavitating case.Many papers in the literature focus solely on hydroacoustic calculations for the open-water case.However,propulsive characteristics are significantly different when propeller-hull interactions take place.Changes in propulsion performance also reflect on the hydroacoustic performances of the propeller.In this study,propeller-hull interactions were considered to calculate the noise spectra.Rather than solving the full case,which is computationally demanding,an indirect approach was adopted;axial velocities from the nominal ship wake were introduced as the inlet condition of the numerical approach.A hybrid method based on the acoustic analogy was used in coupling computational fluid dynamics techniques with acoustic propagation methods,implementing the Ffowcs Williams-Hawkings(FW-H)equation.The hydrodynamic performances of both propellers were presented as a preliminary study.Propeller-hull interactions were included in calculations after observing good accordance between our results,experiments,and quasi-continuous method for the open-water case.With the use of the time-dependent flow field data of the propeller behind a nonuniform ship wake as an input,simulation results were used to solve the FW-H equation to extract acoustic pressure and sound pressure levels for several hydrophones located in the near field.Noise spectra results confirm that the highest values of the sound pressure levels are in the low-frequency range and the first harmonics calculated by the present method are in good accordance with the theoretical values.Results also show that a highly skewed propeller generates less noise even in noncavitating cases despite a small reduction in hydrodynamic efficiency.展开更多
Addressing the ongoing challenge of enhancing propulsion efficiency in rim-driven thrusters(RDTs),a novel energy-saving appendage was designed to mitigate energy dissipation and improve efficiency.Computational fluid ...Addressing the ongoing challenge of enhancing propulsion efficiency in rim-driven thrusters(RDTs),a novel energy-saving appendage was designed to mitigate energy dissipation and improve efficiency.Computational fluid dynamics was utilized to examine the disparities in openwater performance between RDTs with and without this appendage.The Reynolds-Averaged Navier–Stokes equations were solved using the Moving Reference Frame approach within the established STAR-CCM+software.The accuracy of these methodologies was confirmed through a comparison of numerical simulations with experimental data.A meticulous analysis evaluated the alterations in propulsion efficiency of RDTs pre-and post-appendage integration across various advance coefficients.Additionally,a comprehensive assessment of thrust and torque coefficient distributions facilitated a comprehensive understanding of the appendage’s energy-saving potential.Results demonstrated that the new appendage diminishes the diffusive wake behind the rotor disk,fostering a more uniform flow distribution.A notable reduction in the lowpressure zone on the rotor blade’s thrust side was observed,accompanied by an elevation in the high-pressure area.This generated a distinct pressure disparity between the blade’s thrust and suction sides,mitigating the low-pressure region at the blade tip and reducing the likelihood of cavitation.The manuscript further elucidates the rationale behind these alterations,providing detailed insights into flow field dynamics.展开更多
基金The third author acknowledges the financial support from the Scientific and Technological Research Council of Turkey(TUBITAK),Project ID:218 M372.
文摘Despite their high manufacturing cost and structural deficiencies especially in tip regions,highly skewed propellers are preferred in the marine industry,where underwater noise is a significant design criterion.However,hydrodynamic performances should also be considered before a decision to use these propellers is made.This study investigates the trade-off between hydrodynamic and hydroacoustic performances by comparing conventional and highly skewed Seiun Maru marine propellers for a noncavitating case.Many papers in the literature focus solely on hydroacoustic calculations for the open-water case.However,propulsive characteristics are significantly different when propeller-hull interactions take place.Changes in propulsion performance also reflect on the hydroacoustic performances of the propeller.In this study,propeller-hull interactions were considered to calculate the noise spectra.Rather than solving the full case,which is computationally demanding,an indirect approach was adopted;axial velocities from the nominal ship wake were introduced as the inlet condition of the numerical approach.A hybrid method based on the acoustic analogy was used in coupling computational fluid dynamics techniques with acoustic propagation methods,implementing the Ffowcs Williams-Hawkings(FW-H)equation.The hydrodynamic performances of both propellers were presented as a preliminary study.Propeller-hull interactions were included in calculations after observing good accordance between our results,experiments,and quasi-continuous method for the open-water case.With the use of the time-dependent flow field data of the propeller behind a nonuniform ship wake as an input,simulation results were used to solve the FW-H equation to extract acoustic pressure and sound pressure levels for several hydrophones located in the near field.Noise spectra results confirm that the highest values of the sound pressure levels are in the low-frequency range and the first harmonics calculated by the present method are in good accordance with the theoretical values.Results also show that a highly skewed propeller generates less noise even in noncavitating cases despite a small reduction in hydrodynamic efficiency.
文摘Addressing the ongoing challenge of enhancing propulsion efficiency in rim-driven thrusters(RDTs),a novel energy-saving appendage was designed to mitigate energy dissipation and improve efficiency.Computational fluid dynamics was utilized to examine the disparities in openwater performance between RDTs with and without this appendage.The Reynolds-Averaged Navier–Stokes equations were solved using the Moving Reference Frame approach within the established STAR-CCM+software.The accuracy of these methodologies was confirmed through a comparison of numerical simulations with experimental data.A meticulous analysis evaluated the alterations in propulsion efficiency of RDTs pre-and post-appendage integration across various advance coefficients.Additionally,a comprehensive assessment of thrust and torque coefficient distributions facilitated a comprehensive understanding of the appendage’s energy-saving potential.Results demonstrated that the new appendage diminishes the diffusive wake behind the rotor disk,fostering a more uniform flow distribution.A notable reduction in the lowpressure zone on the rotor blade’s thrust side was observed,accompanied by an elevation in the high-pressure area.This generated a distinct pressure disparity between the blade’s thrust and suction sides,mitigating the low-pressure region at the blade tip and reducing the likelihood of cavitation.The manuscript further elucidates the rationale behind these alterations,providing detailed insights into flow field dynamics.
