Planing hull steady hydrodynamics.

The goal of the research performed in this thesis is to develop a tool based on rational mechanics that will provide insight into the flow physics that govern the steady planing of a vessel, and to provide the planing vessel designer with an engineering tool for predicting planing hull lift and drag. The hydrodynamics associated with planing hulls remains a challenging theoretical problem due primarily to the existence of a spray jet at the hull-free surface intersection. Large pressure gradients are experienced in this region due to large flow accelerations associated with the presence of the jet. The large flow accelerations are primarily restricted to the transverse plane. This transverse nature of the flow suggests that the large gradients can be captured approximately in a two dimensional model. Vorus (1996) has developed a free surface impact theory to be used with slender body theory (SBT) to predict steady planing hydrodynamics. The model developed in this thesis is generated by first formulating the three dimensional (3D) boundary value problem, and then adding and subtracting the slender body theory (SBT) formulation. The difference between 3D and SBT represents the three dimensional correction to the slender body solution. The Vorus (1996) model is extended to allow for incorporation of these additional terms. Since the large gradients are captured in the impact model which is used with SBT, the resulting correction terms are generally well behaved functions that allow for numerical iteration to the convergent solution of the three dimensional problem. Purely computational techniques, such as panel methods, have trouble capturing planing hydrodynamics due to the extremely challenging non-linear physics associated with the spray jet and the fact that the hull wetted surface is not known in advance. This problem becomes further complicated when non-prismatic hull geometry is introduced. The three dimensional iterative approach presented in this work allows for resolution of the spray jet details and determination of the wetted surface for general hull shapes within the context of the solution procedure. A comparative study is carried out illustrating the influence that varying hull geometry has on lift and drag. Numerical results from both the 3D and SBT models are compared with experimental force and pressure data.PhDApplied SciencesOcean engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/130352/2/9722083.pd