Hydrodynamic behaviour of gliding hydrofoil crafts
A new type of high-speed craft, called a Gliding-Hydrofoil Craft (GHC), has recently been developed in Jiangsu University of Science and Technology, China. This craft is similar to a planing hull but with a hydrofoil in the front part of its body. The fixed hydrofoil improves the seakeeping properties and stability of the craft compared with a conventional planing hull. In addition, the GHC has a more simple structure and higher stability when compared to a hydrofoil craft. Unlike conventional planing hulls and hydrofoil crafts, the study of hydrodynamics of GHC has been overlooked. The present work aims to advance our understanding on hydrodynamics of GHC, both model tests and numerical investigations are presented. To study its hydrodynamic characteristics, model tests are carried out in a towing tank, and the total resistance, trim angle and wetted area of the craft in the cases with different Froude numbers are measured. For the purpose of comparison, model tests have also been carried out for the hull without the hydrofoil. This thesis presents analysis on the experimental data and discusses the effects of the submerged depth and initial attack angle of the hydrofoil on the hydrodynamic features of the GHC. On this basis, the FLUENT software is then adopted to numerically investigate the hydrodynamics of the GHC. The accuracy of the FLUENT addressing this problem is validated by comparing the numerical solutions with the experimental data. The validation cases include 2D hydrofoil in current, Wigley hull with steady forward speed. Good agreement between numerical results and experimental data was obtained. Considering the significance of the turbulence involved in the problem, especially near the hydrofoil, a numerical investigation aiming to find a suitable turbulence model has been carried out. After being validated, 3D numerical simulations on both the planing craft and the GHC in steady flow are considered. The resistance coefficient, pressure coefficient and wave pattern with different Froude number are investigated. Some results are compared with experiment data obtained in the model tests. The wave pattern, velocity field and pressure distribution near the hulls are discussed in detail as well as the influence of the hydrofoil. Finally, the hydrodynamic performance of GHC in unsteady flow is investigated. Three cases were considered: ship berthing, leaving the harbour and turning navigation direction; which are very commonly seen unsteady examples in reality. The preliminary results presented in this thesis have confirmed the significant effects due to the unsteady procedure and imply the need of carrying out unsteady simulations in the future.
TA Engineering (General). Civil engineering (General)
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