Fact sheet

AKPA - Propulsor design and analysis software

AKPA

AKPA is a suite of numerical tools for the design and analysis of marine propulsors developed by MARINTEK in cooperation with State Marine Technical University (SMTU) of St. Petersburg, Russia.

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the aKPa software includes the three main components:

– PPD – preliminary propeller design program;

– AKPD – propeller blade design program based on non-linear lifting surface theory;

– AKPA – propeller analysis program that uses a velocity based source Boundary element Method (BeM), or “panel method”.

In addition, the aKPa software contains the application aKPa Workbench that facilitates many tasks frequently met in pro-peller design process. aKPa Workbench is also an integrating platform for some of the aKPa components.

The figure below shows different types of propulsors that can be studied by using the program aKPa.

Propeller design and analysis: from user-friendly input through interactive geometry control and calculation to blade manufacture and CFD

Design tools

the design tools of PPD and aKPD allow for full-featured propeller blade design to answer different problem setups and meet various design constraints.

By employing the program PPD one can perform optimization of propeller diameter or RPM at the conditions of required thrust or power using existing systematic propeller series, calculate performance diagram, make the first proposal of blade geometry, and check blade strength characteristics according to several classification rules.

the aKPD program performs hydrodynamic design calcula-tion of propeller that results in definition of blade pitch and camber distributions at given distributions of chord length, thickness, skew and rake (which can be derived from PPD cal-culations or assigned independently by the user) and desired loading distribution along the radius (optimum or user de-fined). The design calculation can be done in given circumfer-entially averaged wake field, including all three wake velocity components. the non-linear lifting surface algorithm allows for the radial flow velocity to be taken into account, which is found to be important when designing blades with high skew and rake, and for propellers operating on conical hubs.

convenient program GUI and visual tools (such as, for exam-

Examples of marine propulsors modeled in the program AKPA.

Open and Ducted FPP and CPP without and with Rudder.

Podded and Multi-component Propulsors.

GUI of the program PPD – a starting point in propeller design process.

contact: Vladimir.Krasilnikov@marintek.sintef.noDept. of ship technology

MARINTEK - Norwegian Marine technology Research Institute P.O.Box 4125 Valentinlyst, NO-7450 trondheim, Norway Tel: +47 73 59 55 00 • Fax: +47 73 59 57 76 • Website: www.marintek.no Jan. 2012

Fact sheet

ple, Propeller Viewer) allow for easy control over propeller geometry, its repeated modification and export to the next stage – propeller analysis by aKPa.

Analysis tools

the main purpose of the analysis program aKPa is to perform calculation of propulsor of given geometry in open water, or in user defined inflow field (e.g., oblique flow or three-dimensional hull wake). this is done by employing a BeM in

velocity based source formulation, with higher order (B-spline) representation of surface geometry. the BeM solution offers a more accurate treatment of all geometrical features of propul-sor than lifting surface theory. special algorithm of Modi-fied Trailing Edge accounts for the viscosity effect on blade section lift and drag in the potential flow formulation of BeM. the results of systematic viscous flow analyses by RaNs are used in this algorithm, which allows for significant extension of the range of applicability of the present method, in terms of propeller loading and off-design pitch setting (for cPP). Re-cently the analysis algorithm was added with the new features to allow for the simulation of propeller in “effective” wake field, which is evaluated from nominal wake defined by the user.

the main outputs of the analysis program are as follows:

• Integral characteristics of propulsor components (e.g. thrust, torque and efficiency of propeller, duct thrust, forces acting on the pod, etc.), and total characteristics of the unit;

• Forces and moments acting on each propeller blade;

• Pressure distributions;

• Velocity fields induced by propulsor components in sur-rounding flow;

• Cavitation domains on propulsor components.

Visualization of wake fields, pressure distributions and pictures of cavitation using visual tools of aKPa facilitates greatly the iterative improvement of geometry that leads to successful propulsor design to meet the requirements of efficiency, unsteady loads, cavitation and noise level.

the designed propeller geometry is presented in the form of a drawing and as a 3D surface model ready to produce caD files for propeller manufacturing and advanced CFD simula-tions in viscous flow.

at present, the aKPa software is not available commercially, and it is used exclusively by the members of the consortium Norwegian Propeller Forum.

Final outputs from the design/analysis procedures – blade geometry in the form of drawing and 3D surface model for manufacturing and CFD simulations.

Analysis of pressure distribution and cavitation pattern on propeller operating in wake field of a large containership using AKPA boundary element method.

Visualization of a ducted propeller with rudder in the Propeller Viewer – a link between design and analysis tools of AKPA.