## General data |

The general data form is used to specify data that apply to the whole model.

Displays the type of the current model: **standard**, variation model or restart analysis. This property of the model is fixed when the model is created (e.g. via the file menu) and cannot be directly modified subsequently.

This displays the parent OrcaFlex model from which the current variation model or restart analysis was created from. This property cannot be directly modified and is only visible for variation and restart models.

For a restart analysis, this is the simulation time in the parent model from which this model restarts.

If a value of ~ is specified, then this model restarts from the end of parent analysis. Otherwise this is a mid-simulation restart.

Note: | If a mid-simulation restart is specified, then the parent model must record restart state at the time specified here. |

Pressing this button activates the corresponding action on the model menu.

A free form multi-line text field that can be used to store notes about the model. OrcaFlex does not use this text.

The **units system** may be chosen to be **SI**, **US** or **user**. Units are defined for length, mass, force, time and temperature, and the value of gravitational acceleration $g$ is also given.

Selecting the **SI** or **US** system will fix the units of length, mass, force, time and temperature and the value of $g$. SI gives length in metres, mass in tonnes, force in kN, time in seconds and temperature in Celsius; US gives length in feet, mass in kips, force in kips, time in seconds and temperature in Fahrenheit.

If neither the SI nor the US systems meets your requirements, then the **user**-defined option gives complete flexibility: you may select individually from the length, mass, force, time and temperature units on offer and also specify a value for $g$.

If the units are changed, then OrcaFlex converts all the existing data in the model from the old units into the new ones.

In this documentation, we generally avoid using specific units. Instead, the dimensions of data items are denoted by $L$ (length), $M$ (mass), $F$ (force), and $T$ (time). For example, density has dimensions $M/L^3$, so tonnes/m^{3} in SI units or kips/ft^{3} in US units.

Notes: | For any given set of length, force and time units, there is a corresponding inertial mass unit, which is the mass that would be accelerated at 1 unit of acceleration when one unit of force was applied. For example in the US units system the unit of acceleration is 1 ft/s^{2} and the unit of force is 1 kip force, so the inertial mass unit is 1 kiloslug (= 1000 slugs = approximately 32000 pounds mass), since a 1 kip force applied to a 1000 slug mass would give an acceleration of 1 ft/s^{2}. |

US units, and many of the possible user-defined units systems, are non-inertial systems: they use mass units that are not the inertial mass unit for their length, force and time units. You should be aware that this help document assumes, as do most text books, that any terms involving mass units (so mass, moment of inertia, density etc.) are expressed in the inertial mass unit, not the non-inertial mass unit used by the unit system. OrcaFlex automatically allows for this when you use US units or any user defined system which is non-inertial. |