Olga dynamic multiphase flow simulator

The latest Symmetry™ fluid engine release brings major stability and accuracy improvements for Olga compositional tracking and Symmetry flashes. Key highlights include:

• Masked floating-point exceptions and corrected phase identification for gas–aqueous systems.
• Enhanced pressure-enthalpy (P-H)-flash handling with consistent schemes for pressure-temperature (P–T) and PH flashes, ensuring stable density derivatives.
• Fixes for internal flashes in inert and simplified three-phase cases when fluids are pure water or aqueous compounds.
• Improved vapor-liquid equilibrium (VLE) predictions for CO₂–natural gas mixtures and better P-H-flash solutions for low-boiling-point fluids.

The KBC Multiflash library has been upgraded from 7.5 to 7.6, delivering improved accuracy and robustness for compositional tracking simulations. Highlights include:

• Enhanced advanced cubic EOS model with updated binary interaction parameters (BIPs) and component properties for better accuracy.
• More robust extrapolation near the critical point for continuous property predictions (notably heat capacity and enthalpy).
• Faster model initialization and updated EOS-CG (Combustion Gas) to the latest 2021 publication.
• Improved handling outside validity ranges with a fallback cubic EOS method, while high-accuracy aqueous EOS remains active for tracking..

The latest PVTSim Nova 7.2 release introduces key enhancements for Olga simulator integration:

• Compositional tracking with PH Flash is now supported.
• New option in the Olga tab file interface lets users control liquid–liquid splits. When two non-aqueous liquid phases occur (e.g. two hydrocarbons or a hydrocarbon and CO₂-rich phase), you can choose to merge them into one liquid or treat the lighter phase as gas in the tab file.
• Ability to generate Olga PH tab files in both PVTSim Nova and PVTSim Nova CCS.

The new directional leak feature improves depressurization simulations for stratified flow regimes, where gas sits above liquid in the pipeline. Unlike the default model (which assumes a well-mixed fluid), this functionality calculates leaked gas and liquid fractions based on:

• Leak angle (position around the pipe circumference)
• Leak diameter
• Liquid level

Olga simulator now supports a new FLUIDMODEL key for centrifugal pumps and compressors, with two options:

• IDEAL (default in Olga 2025.2 and earlier): assumes ideal gas and incompressible liquid.
• EQUILIBRIUM: uses the specified equation of state for more accurate calculations of pump head/torque and compressor compression ratio, without idealized assumptions.

A dedicated CO₂ flow model is now available when the solver option is set to Olga new solver (CCS) and the flow model is set to Olga. It is designed for CO₂-dominated gas–liquid two-phase flow and ensures accurate simulation for these conditions. Compared to the Olga friction factor model, the pressure drop error is reduced by 51%, the hold-up error is decreased by approximately 31%, and the accuracy of flow regime prediction is increased by 34%.