Book contents
- Frontmatter
- Contents
- Preface
- Notation
- Abbreviations
- 1 Brief review of basic hydrodynamic theory
- 2 Properties of distributions of singularities
- 3 Kinematic boundary conditions
- 4 Steady flows about thin, symmetrical sections in two dimensions
- 5 Pressure distributions and lift on flat and cambered sections at small angles of attack
- 6 Design of hydrofoil sections
- 7 Real fluid effects and comparisons of theoretically and experimentally determined characteristics
- 8 Cavitation
- 9 Actuator disc theory
- 10 Wing theory
- 11 Lifting-line representation of propellers
- 12 Propeller design via computer and practical considerations
- 13 Hull-wake characteristics
- 14 Pressure fields generated by blade loading and thickness in uniform flows; comparisons with measurements
- 15 Pressure fields generated by blade loadings in hull wakes
- 16 Vibratory forces on simple surfaces
- 17 Unsteady forces on two-dimensional sections and hydrofoils of finite span in gusts
- 18 Lifting-surface theory
- 19 Correlations of theories with measurements
- 20 Outline of theory of intermittently cavitating propellers
- 21 Forces on simple bodies generated by intermittent cavitation
- 22 Pressures on hulls of arbitrary shape generated by blade loading, thickness and intermittent cavitation
- 23 Propulsor configurations for increased efficiency
- Appendices
- Mathematical compendium
- References
- Authors cited
- Sources of figures
- Index
19 - Correlations of theories with measurements
Published online by Cambridge University Press: 07 May 2010
- Frontmatter
- Contents
- Preface
- Notation
- Abbreviations
- 1 Brief review of basic hydrodynamic theory
- 2 Properties of distributions of singularities
- 3 Kinematic boundary conditions
- 4 Steady flows about thin, symmetrical sections in two dimensions
- 5 Pressure distributions and lift on flat and cambered sections at small angles of attack
- 6 Design of hydrofoil sections
- 7 Real fluid effects and comparisons of theoretically and experimentally determined characteristics
- 8 Cavitation
- 9 Actuator disc theory
- 10 Wing theory
- 11 Lifting-line representation of propellers
- 12 Propeller design via computer and practical considerations
- 13 Hull-wake characteristics
- 14 Pressure fields generated by blade loading and thickness in uniform flows; comparisons with measurements
- 15 Pressure fields generated by blade loadings in hull wakes
- 16 Vibratory forces on simple surfaces
- 17 Unsteady forces on two-dimensional sections and hydrofoils of finite span in gusts
- 18 Lifting-surface theory
- 19 Correlations of theories with measurements
- 20 Outline of theory of intermittently cavitating propellers
- 21 Forces on simple bodies generated by intermittent cavitation
- 22 Pressures on hulls of arbitrary shape generated by blade loading, thickness and intermittent cavitation
- 23 Propulsor configurations for increased efficiency
- Appendices
- Mathematical compendium
- References
- Authors cited
- Sources of figures
- Index
Summary
The number of comparisons that have been made of calculated and measured blade-frequency thrust, torque and other force and moment components are very few because of the paucity of data. In this chapter comparisons of theoretical predictions with experimental data will be given. Results obtained by various theories will also be compared. The chapter concludes with presentation of a simple procedure, based upon the KT-J curve of the steady case, for a quick estimate of the varying thrust at blade frequency.
The measurement of blade-frequency forces on model propellers requires great care in the design of the dynamometer which must have both high sensitivity and high natural frequencies well above the model blade frequency. After a number of failures a successful blade-frequency propeller dynamometer capable of measuring six components (three forces, three moments) was evolved at David Taylor Research Center (DTRC) about 1960.
Measurements were made with a triplet of three-bladed propellers of different blade-area ratio designed to produce the same mean thrust. This set was tested in the DTRC 24-inch water tunnel alternately abaft threeand four-cycle wake screens which produced large harmonic amplitudes of the order of 0.25-U in order to obtain strong output-to-“noise” levels! The three-cycle screens give rise to blade-frequency thrust and torque whereas the four-cycle wake produces transverse and vertical forces and moments about the y- and z-axes which in general come from the fourth and second harmonic orders of blade loading on a three-bladed propeller, as was demonstrated on p. 367.
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- Hydrodynamics of Ship Propellers , pp. 374 - 386Publisher: Cambridge University PressPrint publication year: 1993