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Numerical Hydrodynamics

CFD (Computational Fluid Dynamics)

The tools for mathematical computer-aided simulation available in CEHIPAR are adapted for the optimization of the hulls and propellers, prior to the model tests.

When modifying hull lines, we calculate the flow around the hull for different speeds. The calculations include free-surface potential, boundary layer and full viscous flow (which is applied only for the flow around the stern of the ship).

The propeller design and analysis software is based on circulation theory, determining steady and unsteady forces, sheet cavitation and pressure fluctuations acting on the stern.

Specifications

Ship Hulls

The Flowtech International (Sweden) SHIPFLOW and the MARIN (Netherlands) RAPID commercial codes, and various auxiliary CEHIPAR programs used as interface to the CAD/CAM software.

SHIPFLOW is a panel method for linear and non-linear potential flow, boundary layer and k-e turbulent flow model computations. The k-e turbulent flow model is applied on the stern region of the ship. There is a possibility to calculate lifting surfaces, to include the effects of the propeller and /or shallow water etc.

RAPID is a non-linear potential flow code, including lifting surfaces.

The main results that can be obtained using the ship-hull programs are:

  • Pressure and velocity fields on the hull and the water surface.
  • Wave distribution based on potential flow solution.
  • Wave profiles generated by the ship based on potential flow solution.
  • Limiting stream-lines.
  • Friction coefficient distribution.
  • Boundary layer thickness.
  • Lifting forces based on potential flow solution.
Imagen del cálculo de la distribución de presiones sobre el casco Imagen del cálculo del sistema de olas generadas por el buque

Propellers

The unsteady lifting surface method (VLM modality) is used to analyze the propeller hydrodynamic behavior. Alternatively, we can use a panel code for this purpose. The codes both calculate forces and sheet and tip-vortex cavitation, slipstream deformation and/or inclined shaft taken into consideration. They incorporate viscous corrections.

By comparison against model test results, partial validation of the codes enabled the results to be adjusted empirically to obtain sufficient precision for the steady thrust and torque in the majority of cases. The codes are used in the preliminary phase of ship design and in the propeller design and/or analysis to enhance the initial project.

The main results that can be obtained using the propeller programs are:

  • Characteristic curves and efficiency of the propeller in open water conditions.
  • Thrust, power and efficiency of the propeller behind the ship hull for a given regime.
  • Six components of the vibratory forces and moments on every blade and the shaft.
  • Sheet cavitation development for chosen angular positions of a blade.
  • Volume velocity harmonics of the cavities.
  • Pressure distribution over the blades.
  • Pressure fluctuations, due to the propeller, acting on the stern of the ship.
  • Effective wake distribution.
Panelización de la popa para los programas de CFD de propulsores Salidas de CFD de propulsores

Results

The results of the calculations are represented in tables and graphics.

  • Análisis Exprés-sin traducir- 1
  • More than 80 years of CEHIPAR 1
  • Site of Technology and Innovation of the Ministry of Defence. 1
  • CEHIPAR publications Jueves, 22 de Septiembre de 2005

    CEHIPAR publications are available in this web in “Publications” section or using the “Application form for Publications” in the “Comercial” section.