Threepressure

Threepressure is a term used in some engineering and physics contexts to describe the relationship among three pressure measures within a system. It is not widely standardized and appears in multiple, sometimes unrelated, formulations.

In fluid dynamics, threepressure commonly denotes the decomposition of the total pressure into static pressure (P_s) and dynamic pressure (P_d = 1/2 rho v^2), with the total or stagnation pressure given by P_t = P_s + P_d. This interpretation is used to analyze compressible and incompressible flows, aerodynamics, and instrumentation readings, and it aligns with the Bernoulli principle under appropriate assumptions.

Other usages treat threepressure as a conceptual framework for tri-domain coupling, where three interacting pressure fields P1, P2, P3 describe a system with gas, liquid, and solid phases or different material domains. In such models, exchange terms govern how pressure information transfers between domains.

Criticism: because 'threepressure' is not a standardized term, definitions vary between fields, and care must be taken to specify which pressures are included and under which assumptions.

See also: static pressure, dynamic pressure, total pressure, Bernoulli's principle, multi-phase flow, tri-axial testing.