9.3 Session file configuration

In the following we describe the session file configuration. Specifically we consider the sections under the tag <CONDITIONS> in the session (.xml) file.

Parameters

Under this section it is possible to set the parameters of the simulation.

• TimeStep is the time-step we want to use;
• FinTime is the final physical time at which we want our simulation to stop;
• NumSteps is the equivalent of FinTime but instead of specifying the physical final time we specify the number of time-steps;
• IO_CheckSteps sets the number of steps between successive checkpoint files;
• IO_InfoSteps sets the number of steps between successive info stats are printed to screen;
• Gamma ratio of the specific heats. Default value = 1.4;
• pInf farfield pressure (i.e. p_∞). Default value = 101325 Pa;
• rhoInf farfield density (i.e. ρ_∞). Default value = 1.225 Kg∕m³;
• TInf farfield temperature (i.e. T_∞). Default value = 288.15 K;
• Twall temperature at the wall when isothermal boundary conditions are employed (i.e. T_w). Default value = 300.15K;
• uint farfield X-component of the velocity (i.e. u_∞). Default value = 0.1 m∕s;
• vInf farfield Y -component of the velocity (i.e. v_∞). Default value = 0.0 m∕s;
• wInf farfield Z-component of the velocity (i.e. w_∞). Default value = 0.0 m∕s;
• mu dynamic viscosity (i.e. μ_∞). Default value = 1.78e-05 Pas;
• Pr Prandtl number. Default value = 0.72;
• thermalConductivity thermal conductivity (i.e. κ_∞). This can be set as an alternative to Pr, in which case the Prandtl number is calculated from κ_∞ (it is only possible to set one of them). By default, this is obtained from the Prandtl number;

Solver info

Under this section it is possible to set the solver information.

• EQType is the tag which specify the equations we want solve:
  • NavierStokesCFE (Compressible Navier-Stokes equations);
  • EulerCFE (Compressible Euler equations).
  • IsentropicVortex (Isentropic vortex test case).
  • RinglebFlow (Ringleb flow test case).
• Projection is the type of projection we want to use:
  • DisContinuous.
    Note that the Continuous projection is not supported in the Compressible Flow Solver.
• AdvectionType is the advection operator we want to use.
  • WeakDG (classical DG in weak form);
  • FRDG (Flux-Reconstruction recovering nodal DG scheme);
  • FRSD (Flux-Reconstruction recovering a spectral difference (SD) scheme);
  • FRHU (Flux-Reconstruction recovering Huynh (G2) scheme);
  • FRcmin (Flux-Reconstruction with c = c_min);
  • FRcinf (Flux-Reconstruction with c = ∞).

  Note that only WeakDG is fully supported, the other operators work only with quadrilateral elements (2D or 2.5D).

• DiffusionType is the diffusion operator we want to use for the Navier-Stokes equations:
  • LDGNS (LDG with primitive variables. The penalty term is inversely proportional to the element size, proportional to the local viscosity for the momentum equations and to the thermal conductivity for the energy equation, and proportional to an optional parameter LDGNSc11 which is by default set to one; proportionality to polynomial order can be manually imposed by setting the parameter LDGNSc11 equal to p²);
  • LFRDGNS (Flux-Reconstruction recovering nodal DG scheme);
  • LFRSDNS (Flux-Reconstruction recovering a spectral difference (SD) scheme);
  • LFRHUNS (Flux-Reconstruction recovering Huynh (G2) scheme);
  • LFRcminNS (Flux-Reconstruction with c = c_min);
  • LFRcinfNS (Flux-Reconstruction with c = ∞).

  Note that only LDGNS is fully supported, the other operators work only with quadrilateral elements (2D or 2.5D).

• TimeIntegrationMethod is the time-integration scheme we want to use. Note that only an explicit discretisation is supported:
  • ForwardEuler;
  • RungeKutta2_SSP;
  • RungeKutta3_SSP;
  • ClassicalRungeKutta4.
• UpwindType is the numerical interface flux (i.e. Riemann solver) we want to use for the advection operator:
  • AUSM0;
  • AUSM1;
  • AUSM2;
  • AUSM3;
  • Average;
  • ExactToro;
  • HLL;
  • HLLC;
  • LaxFriedrichs;
  • Roe.
• ViscosityType is the viscosity type we want to use:
  • Constant (Constant viscosity);
  • Variable (Variable viscosity through the Sutherland’s law.);
• EquationOfState allows selecting an equation of state for accounting for non-ideal gas behaviour:
  • IdealGas (default option);
  • VanDerWaals (requires additional parameters Tcrit and Pcrit);
  • RedlichKwong (requires additional parameters Tcrit and Pcrit);
  • PengRobinson (requires additional parameters Tcrit, Pcrit and AcentricFactor);

Boundary conditions

In this section we can specify the boundary conditions for our problem. First we need to define the variables under the section VARIABLES. For a 1D problem we have:

For a 2D problem we have

For a 3D problem we have:

After having defined the variables depending on the dimensions of the problem we want to solve it is necessary to specify the boundary regions on which we want to define the boundary conditions:

Finally we can specify the boundary conditions on the regions specified under BOUNDARYREGIONS. In the following some examples for a 2D problem:

• Slip wall boundary conditions:
  1<BOUNDARYCONDITIONS> 
  2  <REGION REF="0"> 
  3    <D VAR="rho"  USERDEFINEDTYPE="Wall" VALUE="0" /> 
  4    <D VAR="rhou" USERDEFINEDTYPE="Wall" VALUE="0" /> 
  5    <D VAR="rhov" USERDEFINEDTYPE="Wall" VALUE="0" /> 
  6    <D VAR="E"    USERDEFINEDTYPE="Wall" VALUE="0" /> 
  7  </REGION> 
  8</BOUNDARYCONDITIONS>
• No-slip wall boundary conditions:
  1<BOUNDARYCONDITIONS> 
  2  <REGION REF="0"> 
  3    <D VAR="rho"  USERDEFINEDTYPE="WallViscous" VALUE="0" /> 
  4    <D VAR="rhou" USERDEFINEDTYPE="WallViscous" VALUE="0" /> 
  5    <D VAR="rhov" USERDEFINEDTYPE="WallViscous" VALUE="0" /> 
  6    <D VAR="E"    USERDEFINEDTYPE="WallViscous" VALUE="0" /> 
  7  </REGION> 
  8</BOUNDARYCONDITIONS>
• Adiabatic wall boundary conditions:
  1<BOUNDARYCONDITIONS> 
  2  <REGION REF="0"> 
  3    <D VAR="rho"  USERDEFINEDTYPE="WallAdiabatic" VALUE="0" /> 
  4    <D VAR="rhou" USERDEFINEDTYPE="WallAdiabatic" VALUE="0" /> 
  5    <D VAR="rhov" USERDEFINEDTYPE="WallAdiabatic" VALUE="0" /> 
  6    <D VAR="E"    USERDEFINEDTYPE="WallAdiabatic" VALUE="0" /> 
  7  </REGION> 
  8</BOUNDARYCONDITIONS>
• Farfield boundary conditions (including inviscid characteristic boundary conditions):
  1<BOUNDARYCONDITIONS> 
  2  <REGION REF="0"> 
  3    <D VAR="rho"  VALUE="rhoInf" /> 
  4    <D VAR="rhou" VALUE="rhoInf*uInf" /> 
  5    <D VAR="rhov" VALUE="rhoInf*vInf" /> 
  6    <D VAR="E" 
  7    VALUE="pInf/(Gamma-1)+0.5*rhoInf*(uInf*uInf+vInf*vInf+wInf*wInf)"/> 
  8  </REGION> 
  9</BOUNDARYCONDITIONS>
• Pressure outflow boundary conditions:
  1<BOUNDARYCONDITIONS> 
  2  <REGION REF="0"> 
  3    <D VAR="rho"  USERDEFINEDTYPE="PressureOutflow" VALUE="0" /> 
  4    <D VAR="rhou" USERDEFINEDTYPE="PressureOutflow" VALUE="0" /> 
  5    <D VAR="rhov" USERDEFINEDTYPE="PressureOutflow" VALUE="0" /> 
  6    <D VAR="E"    USERDEFINEDTYPE="PressureOutflow" VALUE="pOut" /> 
  7  </REGION> 
  8</BOUNDARYCONDITIONS>

  where pOut is the target static pressure at the boundary.

Initial conditions and exact solution

Under the two following sections it is possible to define the initial conditions and the exact solution (if existent).