Twenty-First Symposium on Naval Hydrodynamics (1997) / Chapter Skim
Currently Skimming:
Water Entry of Arbitrary Two-Dimensional Sections with and Without Flow Separation
Water Entry of Arbitrary Two-Dimensional Sections with and Without Flow Separation
Pages 408-423
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 408... ...
This will also give The dynamic free-surface condition is zero velocity poguidance on how to treat the three-dimensional flow prop- tential on horizontal lines that go through the intersection erly during water entry. Two different two-dimensional points between the free surface and body surface.
|
From page 409... ...
distry of a body with flow separation on the right side and no separation on the left side. tribution on the body surface during water entry of a symmetric wedge with constant velocity V
|
From page 410... ...
The free surface SF inside lye = bits, and the body surface SO, are divided into a number of straight line segments in the numerical evaluation of this integral equation. One straight line element is used to represent AB and CD.
|
From page 411... ...
For instance the angle at the intersection between the water and the body surface is about 1.8° during water entry with constant velocity of a wedge with deadrise an gle 30°(see figure 2~. The length of the total jet is almost the same as the length of the wetted body surface when the wetted surface is defined as the distance from the keel to the spray root of the jet.
|
From page 412... ...
developed an asymptotic solution for water entry of two-dimensional bodies with small local deadrise angles. The flow was studied in two fluid domains.
|
From page 413... ...
In the numerical computation, to is set equal to 0.15tpou~' where tpoUt is the time instance when one needs the pressure distribution and slamming forces as output. This procedure has been tested against the Wagner solution for a water entry of a circle at an early stage and water entry of a wedge with small deadrise angles.
|
From page 414... ...
Numerically predicted total slamming force and maximum pressures on a wedge with different deadrise angles are presented in figure 10. There are good agreement between the simplified and Be similarity solution.
|
From page 415... ...
, simplified solution; ~~~, similarity solution. p,, is atmospheric pressure, ~ is deadrise angle, p is mass density of the fluid, z is vertical coordinate, t is time variable and Vt is the instantaneous draft relative to calm water.
|
From page 416... ...
Figure 11 shows satisfactory agreement between the two different methods. Figure 10: The vertical slamming force F3 and maximum pressure Pma- on symmetric wedges during water entry with constant vertical drop velocity V
|
From page 417... ...
An example with water entry of a wedge with deadrise angle 30° and with knuckles is presented in figure 14. The vertical velocity is constant The pressure distribution and free surface elevation for different time instances after the spray roots separate from the knuckles are presented.
|
From page 418... ...
The measured vertical drop velocity of the body during water entry is presented in gwaauvge figurel5b. The same velocity has been used in the numeritape Cal simulations.
|
From page 419... ...
V is constant drop velocity, Pa is atmospheric pressure, p is mass density, of the fluid and B is breadth of the wedge. y is horizontal coordinate on the body surface.
|
From page 420... ...
and the time rate of change of the wetted area in a von Kannan type of solution will be clearly lower than in our predictions, the time history of the force will also be quite different before flow separation. At a late stage of the water entry, it is of interest to compare He numerical results of vertical force with theoretical drag coefficients for steady symmetric cavity flow past a wedge.
|
From page 421... ...
The effect of flow separation is incorporated by corresponds to that the keel touches the water surface, z is a Kutta condition. The numerical method is validated by vertical coordinate on the body surface, Ok iS vertical cocomparing with new experimental results from drop tests ordinate of the keel and ED iS the draft of the body.
|
From page 422... ...
, Pa is atmospheric pressure, p is mass density of the fluid, t is time variable, t=0 corresponds to that the keel touches the water surface, surface, z is verdcal coordinate on the body surface, Ok iS vertical coordinate of the keel and ED is the draft of the body. o, experimental results; , fillly nonlinear solution.
|
From page 423... ...
1995. Wagner, H.," Uber stoss- und Gleitvergange an der OberZhao, R., Faltinsen, O.M., " Water entry of twodimensional bodies," J.Fluid Mech., Vol.246, pp.593-6 12, 1993.
|
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.