Tank Modes and Types

GHS models the various ways in which tanks can behave by assigning to each tank a Type through the use of the TYPE command. The LOAD CONTENTS commands are used to set the volume of fluid within the tank and the density of the fluid, respectively.

The most common and simplest tank type is INTACT.

An Intact tank contains a certain volume of liquid and the surface of the liquid is maintained such that it lies in a plane parallel with the external waterplane.
Other tank types may have variable volumes, but there is always a Nominal volume associated with each tank. For an Intact tank, the actual volume is the same as the Nominal volume. Nominal volumes are always set by the LOAD command and remain as set until changed by another LOAD command.
Since some tank Types involve complex behavior, it is useful to refer to the Mode in which a tank is operating. Following is a list of the tank Modes and Types.
Tank Modes
Constant-Volume Mode
Volume: Equal to the Nominal volume
Surface: Parallel to the external waterplane
Weight: Adds to the ship's total weight
Free surface: Adds to the total FSM
Frozen Mode
Volume: Equal to the Nominal volume
Surface: Fixed at a prescribed orientation
Weight: Adds to the ship's total weight
Free surface: None
Spilling/Filling Mode
Volume: Varies
Surface: Passes through Tank's Ref. Point & Parallel to external WPL.
Weight: Adds to the ship's total weight
Free surface: Adds to total FSM
Flooded Mode
Volume: Varies
Surface: Coincident with external waterplane
Weight: Subtracts from ship's buoyancy
Definition: Balanced
Internal and external pressures are equal at tank's Reference Point.
External pressure is determined by Reference Point depth.
Internal pressure is determined by the gas at top plus column height.
Level within the tank is not allowed to go below Reference Point.
Balanced Mode Sealed
(Pressure of gas at top is inversely proportional to void volume.)
Volume: Varies; Nominal volume is where pressure = 1 atmosphere
Surface: Parallel to external waterplane
Weight: Adds to ship's total weight
Free surface: Adds to total FSM
Balanced Mode Vented
(Pressure of gas at top is constant at one atmosphere)
Volume: Varies
Weight: Subtracts from ship's buoyancy
Tank Types
Intact Type
Unconditional: Constant-Volume Mode
Frozen Type
Uncond


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