The Proceedings Fifth International Conference on Numerical Ship Hydrodynamics (1990) / Chapter Skim
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Computation of Viscous Flow around a Propeller-Shaft Configuration with Infinite-Pitch Rectagular Blades
Computation of Viscous Flow around a Propeller-Shaft Configuration with Infinite-Pitch Rectagular Blades
Pages 553-570
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From page 553... ...
An overview of the computational method is given, and some example results for both laminar and turbulent flow are presented and discussed with regard to the flow physics, for the idealized geometry of a propeller-shaft configuration with infinite-pitch rectangular blades. It is shown that the flow exhibits many of the distinctive features of interest, including the development and evolution of the shaft and blade boundary layers and wakes, and tip, passage, and hub vortices.
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From page 554... ...
It is apparent from the foregoing that present methods for calculating marine-propeller flow fields are inadequate for analyzing the detailed flow structures such as the development and evolution of the unsteady blade boundary layers and wakes, blade-toblade flow, hub and tip vortices, and overall propeller wake. Furthermore, even the most advanced computational fluid dynamics methods from related applications are either inapplicable or require major modifications to handle marine propellers.
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From page 555... ...
This is expected to facilitate future extensions for entire configurations. In order to extend this approach for the present purpose, a number of major modifications were required, including the following: use of a noninertial coordinate system, which rotates with the propeller, and solution of the corresponding equations; implementation of boundary conditions, including periodic boundary conditions for the blade-to-blade region; adaptation of an ADI scheme at each crossplane; and a complete restructuring of the program for propeller geometries, including calculations for both laminar and turbulent flow.
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From page 556... ...
are linearized in each local rectangular numerical element 65 = An = 6` = 1 , by evaluating the coefficients and source functions at the interior node P and transformed again into a normalized form by a simple coordinate stretching. An analytic solution is derived by decomposing the normalized equation into oneand two-dimensional partial-differential equations.
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From page 557... ...
The boundary conditions on each of the aforementioned boundaries are as follows: on the inlet plane Si, the initial conditions for ~ are specified from simple flat-plate solutions, initial conditions for p and p' are not required; on the shaft Ss and blade surfaces Sbs and Sb , for laminar flow, the solution is carriedP out up to the actual surface where the no-slip condition is applied, for turbulent flow, a two-point wallfunction approach is used; on the exit plane Se, axial diffusion is negligible so that the exit conditions used are ~ ¢/~: = 0, a zerogradient condition is used for p; on the periodic symmetry planes S and S , an explicit periodicity condition is imPpPosed, i.e., ¢(5,n,()
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From page 558... ...
These are followed by a brief presentation of the results for turbulent flow to highlight the differences. This order and emphasis of discussion is selected since the former represent solutions to the exact governing equations, whereas the latter are dependent on the choice of turbulence model.
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From page 559... ...
The pressure variations for the blade plane are similar, but clearly show the effects of the blade leading and trailing edges as well as a small displacement effect of the blade boundary layer. The wall-shear velocity magnitude U variations (figure 6a)
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From page 560... ...
At the near-inlet station, the solution is similar to that for the nonrotating condition, except for the W velocity component which shows a linear increase due to the use of noninertial coordinates. At the leading edge, the solution shows the initiation of the blade boundary layer, in this case, with significant differences between the suction and pressure sides of the blade due to the influences of the aforementioned abrupt changes in the pressure gradients.
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From page 561... ...
Comparison With Results from a LiftingSurface Propeller-Performance Program Unfortunately, no experimental information is available for the present geometry. Therefore, to aid in evaluating the present work, comparisons have been made with some relevant experimental and computational studies, including the following topics: juncture flow which is related to the present flow in the blade-hub juncture region for the nonrotating condition; tip flow which is related to the present flow in the tip region for the rotating condition; turbomachinery flow which is related to the present blade boundarylayer and wake development and blade-to-blade flow; and propeller flow which is, of course, the topic and goal of the present study.
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From page 562... ...
and Chang, M., (1984) , "A Differential Prediction Method for ThreeDimensional Laminar and Turbulent Boundary Layers of Rotating Propeller Blades, " Proc.
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physical domain - 1 (a) circumferential-average flow ~//J ~ so Exit Plans 1~ ~ _ ~ .
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From page 564... ...
~er~_ R~ AnF ROTATING 1'410- SPAN Figure 5. Shaf t and blade surfaces and wake pressure: laminar flow.
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From page 565... ...
W ·05 .15 .2 -.25 - 15 - 05 C ·05 15 .25 ·5 D (b) rotating: suet ion s ide Figure S. Velocity and pressure profiles: laminar flow.
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From page 566... ...
Crossplane-velocity vectors: laminar flow, rotating.
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From page 567... ...
Close-up view of the tip vortex: laminar flow.
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From page 568... ...
Turbulent kinetic energy profiles.
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From page 569... ...
in order to have the grid conform to the threedimensional curved boundaries of the skewed and twisted blades and the nacelle. The results are very encouraging: however, it is anticipated that in order to completely resolve all the details of the flow field, especially for marine propellers, multi-block grids will be necessary, including H-, C, and O-types.
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