InputEnums

The InputEnums package defines a set of enumeration classes used to specify valid options for physical models in OpenSTREAM. These enums help ensure consistency and clarity when selecting model configurations, making the simulation setup more robust and less error-prone.

Typical examples include choosing between void fraction models, interfacial transfer options, or flow regime assumptions, each represented by a clearly defined enum.

class InputEnums.LOCRELVEL

LOCRELVEL Enumeration of local relative velocity models

This class defines the available Inputs.Model.LOCRELVEL models for calculating the local relative velocity between liquid and vapor phases, used by the two-fluid solver.

Models:

AREAMEAN — Difference between area-averaged phase velocities (Walter [2024])
SCALED — Scaled difference using user-defined Inputs.Model.RELVELCST (Walter [2024])
DRIFT — Uses drift velocity as the local relative velocity (Walter [2024])
SIMPLE — Simplified assumptions for bubbly and annular flow regime (Walter [2024])

class InputEnums.NEARWALLRELAX

NEARWALLRELAX Enumeration of near-wall energy transfer time relaxation models

This class defines the available Inputs.Model.NEARWALLRELAX models for calculating the near-wall energy transfer time relaxation, used in mixture solver.

Models:

QUALITY — Simple model relating relaxation time to equilibrium quality using user-defined Inputs.Model.NEARWALLRELAXX and Inputs.Model.NEARWALLRELAXT
VOID — Physical model based on local phase volumetric fraction using user-defined Inputs.Model.NEARWALLRELAXCOEF
FILM — Model applicable to annular two-phase flow

class InputEnums.INTNU

INTNU Enumeration of interfacial Nusselt number models

This class defines the available Inputs.Model.INTNU models for calculating the interfacial Nusselt number, used by the two-fluid solver.

Models:

CONSTANT — Assumes a constant Nusselt number using user-defined Inputs.Model.INTNUVCST and Inputs.Model.INTNULCST for the dispersed gas and liquid phases, respectively
RANZMARSHALL — Ranz-Marshall correlation-based model (Ranz and Marshall [1952]) using user-defined Inputs.Model.RANZMARSHALLVCST and Inputs.Model.RANZMARSHALLLCST for the dispersed gas and liquid phases, respectively
RELAXATION — Time relaxation-based model (Walter [2024])

class InputEnums.NEARWALLH

NEARWALLH Enumeration of near-wall equilibrium enthalpy models

This class defines the available Inputs.Model.NEARWALLH models for setting the near-wall enthalpy to mixture enthalpy ratio, used by the mixture solvers.

Models:

RATIO — Constant near-wall enthalpy to mixture enthalpy ratio using user-defined Inputs.Model.NEARWALLHRATIO
FILM — Mass flux-dependent input for annular two-phase flow

class InputEnums.MOMENTBASE

MOMENTBASE Enumeration of base film momentum conservation models

This class defines the available Inputs.Model.MOMENTBASE models for solving the base film momentum conservation equation, used to compute the base film velocity in the four-field solver.

Models:

ALGEBRAIC — Simple algebraic model (Adamsson and Le Corre [2014], Equations 21 or 23)
EQUILIBRIUM — Equilibrium model
EQUILIBRIUMS — Simplified equilibrium model based on force balance (\(F_{\mathrm{wall}} + F_{\mathrm{vapor}} = 0\))
FULL — Full non-equilibrium model (Le Corre [2022])
FULLNOP — Full non-equilibrium model excluding pressure terms (gravity and buoyancy)

class InputEnums.THINFILMFRIC

THINFILMFRIC Enumeration of thin film friction models

This class defines the available Inputs.Model.THINFILMFRIC models for calculating wall friction under thin film conditions, used by the three-field and four-field solvers.

Models:

LAMINAR — Laminar flow model (\(16/\mathrm{Re}_{film}\))
TURBULENT — Turbulent flow model

class InputEnums.WAVEBASEINT

WAVEBASEINT Enumeration of wave to base film interfacial momentum transfer models

This class defines the available Inputs.Model.WAVEBASEINT models for calculating the interfacial momentum transfer between wave and base film regions, used by the four-field solver.

Models:

VAPORSHEAR — Vapor shear across wave area (consistent with Le Corre [2022], Eq. 46).
VAPORSHEARDROPMASS — Also includes drop deposition momentum transfer, ensuring consistency between wave and base film velocities for thin films.

class InputEnums.OAF

OAF Enumeration of onset of annular flow models

This class defines the available Inputs.Model.OAF models for predicting the onset of annular flow, used by the three-field and four-field solvers.

Models:

WALLIS — Full Wallis correlation (Wallis [1969], Equation 11.1019)
WALLIS_SIMP — Simplified Wallis correlation (Sanmiguel Gimeno et al. [2015], Equation 6), used for compatibility with codes employing this approach

class InputEnums.OAFENTRAINED

OAFENTRAINED Enumeration of entrained drop models at onset of annular flow

This class defines the available Inputs.Model.OAFENTRAINED models for splitting the droplet and film mass flow rates at the onset of annular flow, used by the three-field and four-field solvers.

Models:

RATIO — Ratio of droplet to liquid mass flow rates using user-defined Inputs.Model.OAFDROPRATIO
EQUILIBRIUM — Equilibrium assumption model (\(M_{\mathrm{ent}} = M_{\mathrm{dep}}\)) (Adamsson and Le Corre [2011], Equations 15 and 16)

class InputEnums.DEPOSITION

DEPOSITION Enumeration of droplet deposition models

This class defines the available Inputs.Model.DEPOSITION models for calculating the droplet deposition mass flux, used by the three-field and four-field solvers.

NOTE: Entrainment and deposition correlations are coupled. It is recommended to use the same model for both entrainment and deposition mass flux to ensure consistency.

Models:

NONE — No deposition applied
GOVAN — Hewitt and Govan correlation (Hewitt and Govan [1990])
OKAWA — Okawa et al. correlation (Okawa et al. [2003])

class InputEnums.THERMALRELAX

THERMALRELAX Enumeration of HRM time relaxation models

This class defines the available Inputs.Model.THERMALRELAX models for calculating relaxation times in the HRM model, used when Inputs.Model.THERMALNONEQ is set to HRM.

Models:

QUALITY — Simple model relating relaxation time to equilibrium quality using user-defined Inputs.Model.TRELAXX, Inputs.Model.TRELAXTCOND and Inputs.Model.TRELAXTEVAP
VOID — Physical model based on phase volumetric fraction using user-defined Inputs.Model.TRELAXCONDCOEF and Inputs.Model.TRELAXEVAPCOEF

class InputEnums.SPMTM

SPMTM Enumeration of single-phase wall momentum transfer models

This class defines the available Inputs.Model.SPMTM models for calculating the single-phase wall momentum transfer (liquid or gas), used by the mixture solver.

Models:

BLASIUS — Blasius wall momentum transfer model (\(f = C(1) Re^{C(2)} + C(3)\)) using user-defined Inputs.Model.FRICTION coefficients

class InputEnums.INTAREA

INTAREA Enumeration of volumetric interfacial area calculation models

This class defines the available Inputs.Model.INTAREA models for calculating the volumetric interfacial area, used by the two-fluid solver.

Models:

DISPGAS2DISPLIQ — Transition from spherical bubbles to spherical droplets (Walter [2024])

class InputEnums.EQSTROUHAL

EQSTROUHAL Enumeration of wave equilibrium Strouhal number models

This class defines the available Inputs.Model.EQSTROUHAL models for calculating the wave equilibrium Strouhal number, used by the four-field solver.

Models:

RISO — Based on RISO dataset (Le Corre [2022])
SAWAI — Based on SAWAI dataset (Le Corre [2022])
MFVAL — MFVAL model (under development)
CUSTOM — Custom model using user-defined Inputs.Model.EQSTROUHALCOEF
CSTFRQ — Custom constant frequency using user-defined Inputs.Model.CSTWAVEFREQ

class InputEnums.MFBT

MFBT Enumeration of Minimum Film Boiling Transition (MFBT) models

This class defines the available Inputs.Model.MFBT models for evaluating the Minimum Film Boiling Transition, used by the mixture field.

Models:

NONE — No MFBT transition applied
CONSTANT — Constant deviation from the saturation temperature using user-defined Inputs.Model.DTMFB

class InputEnums.TPFM

TPFM Enumeration of two-phase wall friction multiplier models

This class defines the available Inputs.Model.TPFM models for calculating the two-phase wall friction multiplier used by the mixture solver.

Models:

HOMOGENEOUS — Assumes no slip between phases; both phases move at the same velocity
SLIP — Accounts for velocity differences (slip) between liquid and vapor phases using user-defined Inputs.Model.SLIP
EPRI — Empirical model developed by the Electric Power Research Institute (EPRI) (Reddy and others [1982])

class InputEnums.MOMENTFILM

MOMENTFILM Enumeration of film momentum conservation models

This class defines the available Inputs.Model.MOMENTFILM models for solving the momentum conservation equation for the liquid film, used to compute film velocity in the three-field solver.

Models:

ALGEBRAIC — Simple algebraic model
EQUILIBRIUM — Equilibrium model
EQUILIBRIUMS — Simplified equilibrium model based on force balance (\(F_{\mathrm{wall}} + F_{\mathrm{vapor}} = 0\))
FULL — Full non-equilibrium momentum model (Le Corre et al. [2025])

class InputEnums.ENTRAINMENT

ENTRAINMENT Enumeration of droplet entrainment models

This class defines the available Inputs.Model.ENTRAINMENT models for calculating the droplet entrainment mass flux, used by the three-field and four-field solvers.

NOTE: Entrainment and deposition correlations are coupled. It is recommended to use the same model for both entrainment and deposition mass flux to ensure consistency.

Models:

NONE — No entrainment
GOVAN — Hewitt and Govan correlation (Hewitt and Govan [1990])
OKAWA2003 — Okawa et al. correlation (Okawa et al. [2003])
OKAWA2004 — Okawa et al. correlation (Okawa et al. [2004])
OKAWA2004MOD — Modified Okawa (2004) model from (Adamsson and Le Corre [2011])
OKAWAGEN — Generic Okawa-based model using user-defined Inputs.Model.OKAWACOEFS

class InputEnums.MOMENTGAS

MOMENTGAS Enumeration of gas momentum conservation models

This class defines the available Inputs.Model.MOMENTGAS models for solving the momentum conservation equation for the gas phase, used to compute gas velocity in the two-fluid solver.

Models:

MIXTURE — Uses the same gas velocity as in the mixture model
SLIP — Slip ratio model (gas/liquid velocity) using% user-defined Inputs.Model.SLIP
FULL — Full non-equilibrium momentum model (Le Corre et al. [2025], Walter [2024])

class InputEnums.VOID

VOID Enumeration of void fraction models

This class defines the available Inputs.Model.VOID models to calculate the void fraction in the mixture solver.

Models:

HOMOGENEOUS — Assumes vapor and liquid phases move at the same velocity.
SLIP — Assumes a slip ratio between vapor and liquid phases using user-defined Inputs.Model.SLIP.
BESTION — Drift-flux model developed by Bestion (Bestion [1990]).
EPRI — Drift-flux model developed by the Electric Power Research Institute (EPRI) (Lellouche and Zolotar [1982]).

class InputEnums.OAFFILMSPLIT

OAFFILMSPLIT Enumeration of film mass flow ratio models at onset of annular flow

This class defines the available Inputs.Model.OAFFILMSPLIT models for splitting the base film and wave mass flow rates at the onset of annular flow, used by the four-field solver.

Models:

RATIO — Ratio of base film to film mass flow rates using user-defined Inputs.Model.OAFBASERATIO
EQUILIBRIUM — Equilibrium model (film thickness = equilibrium film thickness) (Le Corre [2022])

class InputEnums.MOMENTDROP

MOMENTDROP Enumeration of droplet momentum conservation models

This class defines the available Inputs.Model.MOMENTDROP models for solving the droplet momentum conservation equation, used to compute droplet velocity in the three-field and four-field solvers.

Models:

ALGEBRAIC — Simple algebraic model consistent with mixture solver
SLIP — Slip ratio model (droplet/gas velocity)
EQUILIBRIUM — Equilibrium model
EQUILIBRIUMS — Simplified equilibrium model based on force balance (\(F_{\mathrm{drag}} + F_{\mathrm{gravity}} + F_{\mathrm{buoyancy}} = 0\))
FULL — Full non-equilibrium momentum model (Le Corre et al. [2025])

class InputEnums.INTLENGTH

INTLENGTH Enumeration of interfacial length scale models

This class defines the available Inputs.Model.INTLENGTH models for calculating the interfacial length scale, used by the two-fluid solver.

Models:

CONSTANT — Assumes a constant interfacial length scale using user-defined Inputs.Model.INTLENGTHVCST and Inputs.Model.INTLENGTHLCST for the dispersed gas and liquid phases, respectively

class InputEnums.WAVEFREQUENCY

WAVEFREQUENCY Enumeration of wave number density transport models

This class defines the available Inputs.Model.WAVEFREQUENCY models for solving the wave number density (or wave frequency) transport equation, used in the four-field solver.

Models:

EQUILIBRIUM — Assumes instantaneous equilibrium between wave generation and dissipation.
RELAXATION — Full transport model including time relaxation effects set by user-defined RELAXTW (Le Corre [2022])

class InputEnums.INTTRANSH

INTTRANSH Enumeration of interfacial enthalpy transfer models

This class defines the available Inputs.Model.INTTRANSH models for calculating the phase enthalpy associated with interfacial mass transfer, used by the mixture and two-fluid solvers.

Models:

BULK — Uses bulk phase enthalpy
SATURATED — Uses saturated phase enthalpy

class InputEnums.VAPORFRIC

VAPORFRIC Enumeration of vapor to film interfacial friction models

This class defines the available Inputs.Model.VAPORFRIC models for calculating the vapor-to-film interfacial friction coefficient used by the three-field and four-field solvers.

Models:

CONSTANT — Uses a fixed, friction coefficient using user-defined Inputs.Model.VAPORFRICCST
WALLIS — Wallis model based on void fraction (Wallis [1969]).
WALLISTHICK — Wallis model based on film thickness (Adamsson and Le Corre [2011], Equation 35).
SOLVER_DEPENDENT — Friction model determined by the solver configuration.

class InputEnums.BTHTM

BTHTM Enumeration of post-boiling transition wall heat transfer models

This class defines the available Inputs.Model.BTHTM models for calculating the post-boiling transition wall heat transfer, used by the mixture solver.

Models:

VAPOR — Wall heat transfer to the vapor phase only, based on single-phase heat transfer model selected in Inputs.Model.SPHTM

class InputEnums.TPKM

TPKM Enumeration of two-phase local loss multiplier models

This class defines the available Inputs.Model.TPKM models for calculating the two-phase local loss multiplier used by the mixture model

Models:

HOMOGENEOUS — Assumes no slip between phases; both phases move at the same velocity.
SLIP — Accounts for velocity differences (slip) between liquid and vapor phases using user-defined Inputs.Model.SLIP.
ROMIE — Romie model; behaves like the homogeneous model when a homogeneous void fraction model is applied.

class InputEnums.DEPENHANCEMENT

DEPENHANCEMENT Enumeration of droplet deposition enhancement models

This class defines the available Inputs.Model.DEPENHANCEMENT models for calculating local droplet deposition enhancement, used by the three-field and four-field solvers.

Models:

NONE — No enhancement applied
WINDECKER — Model adapted from Windecker [1999], as documented in Le Corre [2024], using user defined Inputs.Model.KTUNING

class InputEnums.THERMALNONEQ

THERMALNONEQ Enumeration of thermal non-equilibrium models

This class defines the available Inputs.Model.THERMALNONEQ models for calculating phase thermal non-equilibrium effects, used by the mixture solver.

Models:

EQUILIBRIUM — Assumes thermal equilibrium (\(X = \max(0, X_{EQ})\))
SAHAZUBER — Saha-Zuber subcooled boiling model (Saha and Zuber [1973])
EPRI — EPRI subcooled boiling model (Lellouche and Zolotar [1982])
HRM — Homogeneous Relaxation Model for subcooled boiling and post-CHF conditions (HRM)

class InputEnums.FLUIDPROPERTIES

FLUIDPROPERTIES Enumeration of fluid property calculation assumptions

This class defines the available Inputs.Model.PROPERTIES assumptions to calculate fluid properties, applicable to all solvers.

Models:

SATURATED — Properties based on saturated conditions at system pressure
PSYSTEM — Properties based on system pressure and local phase enthalpy

class InputEnums.MOMENTWAVE

MOMENTWAVE Enumeration of film momentum conservation models

This class defines the available Inputs.Model.MOMENTWAVE models for solving the momentum conservation equation for the wave field, used to compute wave velocity in the four-field solver.

Models:

ALGEBRAIC — Simple algebraic model (Adamsson and Le Corre [2014], Equations 21 or 23)
EQUILIBRIUM — Equilibrium model
FULL — Full non-equilibrium momentum model (Le Corre [2022])

class InputEnums.MOMENTLIQUID

MOMENTLIQUID Enumeration of liquid momentum conservation models

This class defines the available Inputs.Model.MOMENTLIQUID models for solving the momentum conservation equation for the liquid phase, used to compute liquid velocity in the two-fluid solver.

Models:

MIXTURE — Uses the same velocity as in the mixture model
SLIP — Slip ratio model (gas/liquid velocity) using user-defined Inputs.Model.SLIP
FULL — Full non-equilibrium momentum model (Le Corre et al. [2025], Walter [2024])

class InputEnums.BASEEQTHICK

BASEEQTHICK Enumeration of base film equilibrium thickness models

This class defines the available Inputs.Model.BASEEQTHICK models for calculating the equilibrium base film thickness, used by the four-field solver.

Models:

RISO — Based on RISO dataset (Le Corre [2022])
COEFS — Generalized RISO model using user-defined Inputs.Model.BASEEQTHICKCOEF
YPLUS — Based on dimensionless wall distance (y+) using user-defined Inputs.Model.BASEYPLUS
MFVAL — MFVAL model (under development)

class InputEnums.BTMTM

BTMTM Enumeration of post-boiling transition wall momentum transfer models

This class defines the available Inputs.Model.BTMTM models for calculating the post-boiling transition wall momentum transfer, used by the mixture solver.

Models:

TPFM — Wall momentum transfer based on two-phase friction multiplier, using multiplier selected in Inputs.Model.TPFM
VAPOR — Wall momentum transfer based on vapor phase only, using single-phase momentum transfer model selected in Inputs.Model.SPMTM

class InputEnums.CBT

CBT Enumeration of Critical Boiling Transition (CBT) models

This class defines the available Inputs.Model.CBT models for evaluating the Critical Boiling Transition, used by the mixture field.

Models:

NONE — No CBT transition applied
BIASI — Biasi correlation model (Biasi et al. [1966])
BEZRUKOV — Bezrukov correlation model (Bezrukov et al. [1976])
ELEVATION — CBT determined from specified elevation using user-defined CBTELEVATION

class InputEnums.TPHTM

TPHTM Enumeration of two-phase wall heat transfer models

This class defines the available Inputs.Model.TPHTM models for calculating the two-phase wall heat transfer, used by the mixture solver.

Models:

THOM — Thom wall heat transfer model (Rohsenow et al. [1998])

class InputEnums.BUBBLEDRAG

BUBBLEDRAG Enumeration of bubble drag coefficient models

This class defines the available Inputs.Model.BUBBLEDRAG models for calculating the bubble drag coefficient, used by the two-fluid solver.

Models:

CONSTANT — Constant drag coefficient using user-defined Inputs.Model.BUBBLEDRAGCOEF
STOKES — Stokes flow regime model (\(\frac{24}{Re_{p}}\))
VISCOUS — Viscous regime model (Walter [2024])
DISTORTED — Model for distorted bubbles (non-spherical) (Walter [2024])

class InputEnums.SPHTM

SPHTM Enumeration of single-phase wall heat transfer models

This class defines the available Inputs.Model.SPHTM models for calculating the single-phase wall heat transfer (liquid or gas), used by the mixture solver.

Models:

DITTUSBOELTER — Dittus-Boelter wall heat transfer model for heating (\(\mathrm{Nu} = 0.023 \cdot \mathrm{Re}^{0.8} \cdot \mathrm{Pr}^{0.4}\)) (Dittus and Boelter [930], McAdams [1942])
DITTUSBOELTERGEN — Generalized Dittus-Boelter wall heat transfer model using user-defined Inputs.Model.DITTUSBOELTERCOEF

class InputEnums.DROPDRAG

DROPDRAG Enumeration of droplet drop drag coefficient models

This class defines the available Inputs.Model.DROPDRAG models for calculating the droplet drag coefficient, used by the two-fluid solver.

Models:

CONSTANT — Constant drag coefficient using user-defined Inputs.Model.DROPDRAGCOEF
STOKES — Stokes flow regime model (\(\frac{24}{Re_{p}}\))
VISCOUS — Viscous regime model (Walter [2024])
DISTORTED — Model for distorted (non-spherical) droplets (Walter [2024])