restvolum

Restvolum is a term occasionally used in engineering and physical modelling to designate the baseline, static volume of a bounded system when it is at rest. It represents the portion of a system’s internal space that would be occupied by a fluid or material under equilibrium conditions, with no ongoing flow, pressure transients, or motion. Restvolum is distinguished from dynamic volumes, which account for transient storage due to inflows, outflows, wave propagation, or compressibility effects, and from effective volumes that include pump- or valve-induced storage.

The precise definition of restvolum varies with the modelling framework, and it is not a universally standardized quantity. In a closed, rigid container with an incompressible fluid, restvolum coincides with the container’s internal fluid capacity. In systems with gas–liquid interfaces or porous media, restvolum may refer to the portion of the space that remains filled at rest under specified boundary conditions, often under standard or reference conditions. The concept is typically used to separate baseline storage from dynamic effects in simulations.

Calculation and estimation of restvolum generally rely on static analysis of geometry and boundary conditions. It can be determined from the sum of geometrically defined compartments that are permanently occupied at rest or by subtracting movable or transiently accessible storage from the total capacity. In practice, restvolum serves as a stable initial condition or reference point for transient analyses of hydraulics, fluid networks, or thermal systems.

See also: static volume, equilibrium volume, residual volume.