2026-10-24
Explicit constrained derivations and second-order analysis of Q-functions for flash specifications
Publication
Publication
Fluid Phase Equilibria , Volume 614 p. 114899:1- 114899:12
The present work develops an explicit constrained-optimization treatment of the Q-functions in Helmholtz-energy variables for the PSN, PHN, PTN, and SVN specifications. The actual independent-variable space is stated for each specification, the Lagrange multipliers are obtained directly from stationarity in those variables, and the resulting Q-functions are shown to recover the prescribed constraints and phase-equilibrium conditions. A second-order analysis then distinguishes the full Hessian of the unconstrained Q-function from the reduced Hessian relevant to the original constrained thermodynamic problem. We show that, on the admissible tangent space, the quadratic form of the Q-function Hessian coincides with that of the KKT Lagrangian.
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| , , , , , , | |
| doi.org/10.1016/j.fluid.2026.114899 | |
| Fluid Phase Equilibria | |
| creativecommons.org/licenses/by/4.0/ | |
| Organisation | Centrum Wiskunde & Informatica, Amsterdam (CWI), The Netherlands |
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Kumar, P. (2026). Explicit constrained derivations and second-order analysis of Q-functions for flash specifications. Fluid Phase Equilibria, 614, 114899:1–114899:12.https://doi.org/10.1016/j.fluid.2026.114899 |
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