The Proceedings Fifth International Conference on Numerical Ship Hydrodynamics (1990) / Chapter Skim
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Propeller Inflow Corrections for Improved Unsteady Force and Cavitation Calculations
Propeller Inflow Corrections for Improved Unsteady Force and Cavitation Calculations
Pages 701-714
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From page 701... ...
The calculations showed only small changes in the magnitude of the velocity components and blade pressures when compared to typical counterrotating propeller design results. Approximate agreement was found between the absolute magnitude of both the harmonic coefficients and the total unsteady forces obtained using the calculated axial velocity and the measured wake.
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From page 702... ...
and blade pressures associated with a counterrotating propeller set. Measured Velocity Field In the design of wake-adapted propellers, it is important that the inflow velocity distribution at the propeller stacking lines be properly specified.
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From page 703... ...
Summary of Counterrotating Propeller Design Inputs and Calculated Results Using Circumferential Mean Inflow Data RF R.]
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From page 704... ...
between the blade section and the fluid is determined from the tangential velocity due to propeller rotation (Slr) , the axial inflow velocity with propellers not present (v0, the axial and tangential components of the self-induced (we, w~)
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From page 705... ...
Propeller Calculations As stated before, one problem inherent in the calculation of unsteady forces involves the use of wake data obtained without a propeller present. While the propeller design method of Nelson calculates changes in the circumferential mean inflow velocity field due to the presence of a propulsor the uncorrected, spatially varying inflow has been used to determine the unsteady forces acting on the propeller blades.
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From page 706... ...
4. Velocity components and geometric parameters for the forward and after propellers calculated using circumferential mean inflow data v~s , forward; ~ -, after.
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From page 707... ...
Unsteady Forces The axial velocity component of the measured wake and the calculated axial inflow velocity were used in both Fourier analysis and unsteady forces calculations. The data was supplemented with the geometric parameters found in tables 1 and 2.
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From page 708... ...
Next, data will be presented to illustrate the unsteady forces obtained by varying the propulsor inflow. Figures 8 and 9 present the radial distribution of harmonic coefficient magnitude and unsteady forces for the calculated axial velocity fields obtained by specifying (a)
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From page 709... ...
with radial position (r/RF) for the forward propeller.
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From page 710... ...
magnitude of both the harmonic coefficients and unsteady forces obtained using the axial component of the inflow velocity and the measured wake data. However, the unsteady force distributions associated with the calculated axial velocity, which includes propeller effects, showed an increase in magnitude at the inner radii with minimal change in its general shape.
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From page 711... ...
10. Circumferential variation of the cavitation index a, for the forward propeller at various x locations.
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From page 712... ...
/~ p V2, calculated using circumferential mean data for the forward and after propellers at various x locations.
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From page 713... ...
and G Lammers, "Measurements of the Time Dependent Velocity Field Surrounding a Model Propeller in Uniform Water Flow,.
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