Numerical Modeling of Multi-Surface Planing Hull Hydrodynamics Using Source-Based Boundary Element Method
Bari, Ghazi Saiful
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A source-based boundary element method (BEM) built on the potential flow theory is developed to study hydrodynamic characteristics of multi-surface planing hulls. Initially, both 2D and 3D numerical models are implemented and validated. Upon validation, the numerical model is applied for three specific hull types to predict their hydrodynamic properties. Firstly, the hydrodynamic performance of a stepped hull with variable deadrise angles is investigated. Secondly, the hydrodynamic inference effect on a symmetric catamaran hull is studied. And lastly, the hydrodynamic parameters are analyzed for the asymmetric catamaran setup. The validation results are presented for the lift coefficient, center of pressure, water surface elevation around the hull, and pressure coefficient. Numerical results are compared with those found in the technical literature. Parametric calculations are carried out for a stepped hull with variable deadrise angles in two-speed regimes and the results are shown for hydrodynamic characteristics of the hull. For the catamaran design, the hydrodynamic interaction between hulls planing parallel to each other is known to become significant when the spacing between hulls is sufficiently small. To investigate this interference effect, calculations are carried out for symmetric hulls in variable speed regimes at different spacings, hull aspect ratio, and deadrise angles. Again, for asymmetric planing hulls, the numerical results are validated with available experimental data and empirical correlations. Parametric calculation results are presented for the lift coefficient and the center of pressure for variable hull geometry, spacings, and speed regimes. It was observed that the wetted surfaces of both fore hull and aft body of the stepped hull have a direct impact on hydrodynamic forces. The downstream shape of the air-ventilated cavity changes drastically for variable aft body compared to the variable fore hull. For the catamaran hull, the interaction effect on the lift is stronger for longer hulls and larger deadrise angles at both moderate and high Froude numbers. The smaller spacings between two demi-hulls yield higher impact on different hydrodynamic parameters. Similarly, for asymmetric catamaran configuration, the lift coefficient is found to increase at smaller hull spacings. However, it decreases at higher Froude numbers and higher deadrise angles.