Twenty-First Symposium on Naval Hydrodynamics (1997) / Chapter Skim
Currently Skimming:
On the Modeling of the Flow Past a Free-Surface-Piercing Flat Plate
On the Modeling of the Flow Past a Free-Surface-Piercing Flat Plate
Pages 470-477
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 470... ...
Abstract Some numerical simulations and experiments for the analysis of the free surface flow past a flat plate in drift motion have been carried out. Two mathematical models were used in the simulation: the first one is a linear inviscid model with a vortex layer shed from the trailing edge and from the tip of the plate; the second one is described by the NavierStokes equations with the algebraic Baldwin-Lomax turbulence model.
|
From page 471... ...
2.1 Inviscid Model In this model viscous effects are supposed to be confined close to the rigid boundary, where the fluid viscosity determines the generation of vorticity The vorticity evolution and shedding are described by means of the inviscid fluid mechanics, that is viscous effects are completely neglected and rotational zones are modelled as vorticity layers, emerging from known separation lines (the lower tip and the trailing edge)
|
From page 472... ...
In the numerical solution, these equations are discretized by means of a standard finite volume technique on a curvilinear grid, that moves to fit the actual free surface shape. All the derivative are expressed by centered differentiation, and the variables at cell interfaces are evaluated by simple averaging from the neighbouring points.
|
From page 473... ...
Moreover, the velocity vector at the free surface is extrapolated from the first inner point. This simplified boundary condition are a common practice when computing free surface viscous flows, because in general the grid near the water-air interface is too coarse to resolve the boundary layer.
|
From page 474... ...
tions and experimental data when computing freesurface flows beyond certain values of the Froude number and angle of attack. Fig.8 and 9 show the hydrodynamic coefficients as functions of the Fioude number, with 4.5 and 9 degrees of incidence and aspect ratio equal to 0.5.
|
From page 475... ...
The role of the actual wave displacement was in fact analysed with the Navier-Stokes model, retaining the usual form of the free surface boundary conditions, but preventing the motion of the boundary, and therefore enforcing them on the undisturbed water plane z = 0 As shown in fig. 15, the effect on the hydrodynamic coefficients is very small, also in the supercritical regime.
|
From page 476... ...
Therefore, a possible reason of such a behaviour must be sought in the nonlinear terms in the free surface boundary conditions, neglected in our inviscid computations. Another possible cause could be related to the Kutta condition imposed at the trailing edge.
|
From page 477... ...
van den Brug J.B., Beukelman W., Prins G.J., "Hydrodynamic forces on a surface piercing flat plate", Rep. 325, Shipbuilding laboratory, Delft Univ.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.