Navigation:  Hydrostatics & Stability > Introduction

Orca3D performs hydrostatics and intact stability calculations on any combination of one or more Rhino surfaces and meshes. The flotation condition to be analyzed can be specified in two basic manners:

 

 

With both approaches, there is the option of analyzing stability over a range of heel angles, and a complete report of the hydrostatics and stability data is produced.

 

The process of computing hydrostatics and stability can be summarized as follows:

1. Define any Points of Interest (points on the model whose height above the waterline are tracked as the model heels, trims, and sinks)

2. Select the surface(s) and/or mesh(es) to be included

3. Define the flotation condition(s) to be analyzed

4. Review the report

If you are computing hydrostatics in the context of designing a hull, where you need to see results frequently and rapidly, but always with the same flotation condition (at the design waterline, for example), Orca3D provides a special case of the hydrostatics command, called "Design Hydrostatics." In this case, the Design Condition is defined once (i.e. the surface(s) to be included, and the flotation plane or the weight/CG), and then the analysis can be run with a single button click, without having to define the surface(s) and flotation condition each time.

 

Note: It is assumed that the model's centerplane is at the plane where the transverse coordinate = 0 (for example, the Y=0 plane). Incorrect results will be reported otherwise.

 

Note: Orca3D computes most of the hydrostatics parameters from the surface mesh, not in the traditional manner of integrating stations (stations are used for the sectional area curve, and the prismatic and maximum section coefficients). In general, this leads to more accurate results, and avoids the possibility of missing or mistreating features in the hull surface, such as the end of a hull skeg. The accuracy of the calculations, therefore, depends on the smoothness of the surface mesh (this is true in Rhino for other things; for example the curvature maps depend on the smoothness of the analysis mesh). To adjust the smoothness of the Orca3D mesh, use the OrcaProperties command, or the icon (), and set the values in the Orca Mesh Parameters section. Also, please visit the Mesh Density Accuracies section of the Verification and Testing chapter, to see how various mesh settings affect the accuracy of the results.