Forces Forces

In MOSES, forces on the system are separated into nineteen named categories:

The accuracy of the computation of forces on a plate or panel depends on the shape of the panel. In particular, the results for more "compact" panels is superior to those which are "long and skinny". As a guide to the "badness" of panels, a badness measure is reported for the &SUMMARIES of panels and plates. Now, often this measure is taken as the "aspect ratio" of the panel; i.e.

     R = W/H

Where W is the width, H is the height and W > H. This is all fine and good for rectangular plates, but when these enter the water the submerged portion is rarely a rectangle.

To generalize this notion, in MOSES, we define badness as

     B = P / [ 2 sqrt(pi*A) ]  - 1.

Here P is the perimeter and A is the area. Notice that for a circle, B is zero and that for rectangular plates it increases with the increase of aspect ratio.

When added mass is computed for a panel or plate, the results from DNV-RP-C205 are used. In particular, the force computations presented there for added mass forces are tabulated as a function of B and interpolated based on the current values of B for the submerged portion of the plate.