This is a model of a tank with environment pressure at inlet, hydrostatic pressure at the bottom, and an outlet orifice. The pressure at the bottom depends on the fluid height:



where

p		:	Pressure at the tank bottom
		:	Fluid density
g		:	Standard acceleration of gravity on Earth
h		:	Height of the fluid

The orifice is modeled with a ControlledOrifice, which behaves approximately according to the following equation:



where

		:	Mass flow rate through the opening
		:	Discharge coefficient
A		:	Orifice opening area
		:	Pressure drop over the orifice
		:	Fluid density

Implementation

A laminar restriction models the accumulator opening. The conductance of the restriction is put to zero when system pressure is lower than the preload pressure.

Limitations

The height of the fluid is not limited. This model does not prevent negative height that could occur if a pump connected to the outlet empties the tank. In that situation, the pump would actually run dry and might even break.

Reference

K. Gieck and R. Gieck, Engineering Formulas, 7th ed., Germering, Germany: Gieck Publishing, 1997 p. N1 and N7.

medium	Value: Oil() Type: Medium Description: Medium in the component
A_bottom	Value: 1 Type: Area (m²) Description: Bottom area of tank
A_outlet	Value: 0.001 Type: Area (m²) Description: Area of outlet orifice
pEnv	Value: 100000.0 Type: Pressure (Pa) Description: Environment pressure
Cd	Value: 0.62 Type: Real Description: Coefficient of discharge for the opening
hMaxAnimation	Value: 1 Type: Height (m) Description: Max height for animation