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cs_time_scheme_t Struct Reference

Time scheme descriptor. More...

#include <cs_parameters.h>

Collaboration diagram for cs_time_scheme_t:

Data Fields

int time_order
int istmpf
int isno2t
int isto2t
double thetsn
double thetst
double thetvi
double thetcp
int iccvfg

Detailed Description

Time scheme descriptor.

Members of the time scheme structure are publicly accessible, to allow for concise syntax, as they are expected to be used in many places.

Field Documentation

◆ iccvfg

int iccvfg

indicates whether the dynamic field should be frozen or not:

  • 1: true
  • 0: false (default)
    In such a case, the values of velocity, pressure and the variables related to the potential turbulence model ( $k$, $R_{ij}$, $\varepsilon$, $\varphi$, $\bar{f}$, $\omega$, turbulent viscosity) are kept constant over time and only the equations for the scalars are solved.
    Also, if iccvfg = 1, the physical properties modified in cs_user_physical_properties will keep being updated. Beware of non-consistencies if these properties would normally affect the dynamic field (modification of density for instance).
    Useful if and only if nscal $>$ 0 and the calculation is a restart.

◆ isno2t

int isno2t

Specifies the time scheme for the source terms of the momentum equation, apart from convection and diffusion (for instance: head loss, transposed gradient, ...).

  • 0: "standard" first-order: the terms which are linear functions of the solved variable are implicit and the others are explicit.
  • 1: second-order: the terms of the form $S_i\phi$ which are linear functions of the solved variable $\phi$ are expressed as second-order terms by interpolation (according to the formula $(S_i\phi)^{n+\theta}=S_i^n[(1-\theta)\phi^n+\theta\phi^{n+1}]$, $\theta$ being given by the value of theta associated with the variable $\phi$); the other terms $S_e$ are expressed as second-order terms by extrapolation (according to the formula $(S_e)^{n+\theta}=[(1+\theta)S_e^n-\theta S_e^{n-1}]$, $\theta$ being given by the value of thetsn = 0.5).
  • 2: the linear terms $S_i\phi$ are treated in the same way as when isno2t = 1; the other terms $S_e$ are extrapolated according to the same formula as when isno2t = 1, but with $\theta$= thetsn = 1. By default, isno2t is initialized to 1 (second-order) when the selected time scheme is second-order (ischtp = 2), otherwise to 0.

◆ istmpf

int istmpf

Time order of the mass flux scheme The chosen value for istmpf will automatically determine the value given to the variable thetfl.

  • 2: theta scheme with theta > 0 (theta=0.5 means 2nd order) the mass flow used in the momentum equations is extrapolated at n+ thetfl (= n+1/2) from the values at the two former time steps (Adams Bashforth); the mass flow used in the equations for turbulence and scalars is interpolated at time n+ thetfl (= n+1/2) from the values at the former time step and at the newly calculated $n+1$ time step.
  • 0: theta scheme with theta = 0 (explicit): the mass flow calculated at the previous time step is used in the convective terms of all the equations (momentum, turbulence and scalars)
  • 1: implicit scheme (default) : the mass flow calculated at the previous time step is used in the convective terms of the momentum equation, and the updated mass flow is used in the equations of turbulence and scalars. By default, istmpf=2 is used in the case of a second-order time scheme (if ischtp=2) and istmpf = 1 otherwise.

◆ isto2t

int isto2t

Specifies the time scheme for the source terms of the turbulence equations i.e. related to $k$, $R_{ij}$, $\varepsilon$, $\omega$, $\varphi$, $\overline{f}$), apart from convection and diffusion.

  • 0: standard first-order: the terms which are linear functions of the solved variable are implicit and the others are explicit.
  • 1: second-order: the terms of the form $S_i\phi$ which are linear functions of the solved variable $\phi$ are expressed as second-order terms by interpolation (according to the formula $(S_i\phi)^{n+\theta}=S_i^n[(1-\theta)\phi^n+\theta\phi^{n+1}]$, $\theta$ being given by the value of theta associated with the variable $\phi$); the other terms $S_e$ are expressed as second-order terms by extrapolation (according to the formula $(S_e)^{n+\theta}=[(1+\theta)S_e^n-\theta S_e^{n-1}]$, $\theta$ being given by the value of thetst = 0.5)
  • 2: the linear terms $S_i\phi$ are treated in the same isto2t = 1; the other terms $S_e$ are way as when extrapolated according to the same formula as when isto2t = 1, but with $\theta$= thetst = 1.
    Due to certain specific couplings between the turbulence equations, isto2t is allowed the value 1 or 2 only for the $R_{ij}$ models (model = 30 or 31); hence, it is always initialised to 0.

◆ thetcp

double thetcp

$ \theta $-scheme for the extrapolation of the physical property $\phi$ "specific heat" when the extrapolation has been activated (see time_extrapolated field key int), according to the formula $\phi^{n+\theta}=(1+\theta)\phi^n-\theta \phi^{n-1}$.
The value of $\theta$ = thetcp is deduced from the value chosen for the specific heat. Generally, only the value 0.5 is used.

  • 0 : explicit
  • 1/2: extrapolated in n+1/2
  • 1 : extrapolated in n+1

◆ thetsn

double thetsn

$ \theta_S $-scheme for the source terms $S_e$ in the Navier-Stokes equations when the source term extrapolation has been activated (see isno2t), following the formula $(S_e)^{n+\theta}=(1+\theta)S_e^n-\theta S_e^{n-1}$.
The value $theta$ = thetsn is deduced from the value chosen for isno2t. Generally only the value 0.5 is used.

  • 0 : second viscosity explicit
  • 1/2: second viscosity extrapolated in n+1/2
  • 1 : second viscosity extrapolated in n+1

◆ thetst

double thetst

$ \theta $-scheme for the extrapolation of the nonlinear explicit source terms $S_e$ of the turbulence equations when the source term extrapolation has been activated (see isto2t), following the formula $(S_e)^{n+\theta}=(1+\theta)S_e^n-\theta S_e^{n-1}$.
The value of $theta$ is deduced from the value chosen for isto2t. Generally, only the value 0.5 is used.

  • 0 : explicit
  • 1/2: extrapolated in n+1/2
  • 1 : extrapolated in n+1

◆ thetvi

double thetvi

$ \theta $-scheme for the extrapolation of the physical property $\phi$ "total viscosity" when the extrapolation has been activated (see time_extrapolated key word), according to the formula $\phi^{n+\theta}=(1+\theta)\phi^n-\theta \phi^{n-1}$.
The value of $\theta$ = thetvi is deduced from the value chosen for time_extrapolated key word for the viscosity. Generally, only the value 0.5 is used.

  • 0 : explicit
  • 1/2: extrapolated in n+1/2
  • 1 : extrapolated in n+1

◆ time_order

int time_order

Global time order of time stepping

  • 2: 2nd order
  • 1: 1st order (default)
The documentation for this struct was generated from the following files: