This data category is used to scale and/or change the geometric or mass characteristics of a single body or system of bodies. When scaling or changing body characteristics the results are output to the hydrodynamic data-base, and hence over-write the original data-base file. This data category may also be used to define a new hydrodynamic reference point. This gives the user the fluid forces, etc about a point other than the center of gravity. This data category may be omitted and NONE entered for the data category keyword.

Scaling by Length or Mass

The user may scale various hydrodynamic and response parameters either directly by using a length scale factor, or indirectly by using a mass scale factor. The scaling factors are as follows:

Length Scale Factor = Length_new / Length_old

The user inputs the Length Scale Factor directly in this data category.

Mass Scale Factor = (Mass_new/ Mass_old)^(1/3)

The user inputs the new Mass directly in this data category.

The parameters that are scaled are as follows:

Changes to Mass Distribution and/or Center of Mass

The following changes may be made to a body's mass characteristics:

The new coordinates of the center of gravity must relate to the originally defined position of the body.

The above changes in mass characteristics require a new solution for the body's responses. Also note that a change in center of gravity in the lateral direction, will cause an originally equilibrated freely floating body to move away from the original equilibrium position.

New Hydrodynamic Reference Point

If the user requires the hydrodynamic coefficients, fluid forces and body response about a new reference point then this point may be input in this data category. Note that again the new reference point must relate to the originally defined position of the body.