TCNEQ Version

Background

The following information relates to the use of the thermochemical nonequilibrium (TCNEQ) version of PHASTA written in terms of entropy variables. The reader is referred to the following for additional information.

• F. Chalot, T.J.R. Hughes, and F. Shakib, "Symmetrization of Conservation Laws with Entropy for High-Temperature Hypersonic Computations," Computing Systems in Engineering, 1(2-4):495–521, 1990.

• J. Pointer, "Influence of Interpolation Variables and Discontinuity Capturing Operators on Inviscid Hypersonic Flow Simulations Using a Stabilized Continuous Galerkin Solver," Ph.D. dissertation, University of Colorado, Boulder, CO, 2022.

Pre-Processing

In this section, details of the meshing and model attributes are provided. For simulation cases where the gas is modeled as a single species, the scalar quantities for boundary and initial conditions are not required. Currently, capability exists to simulate a gas with number of species (nsp) ≤ 5. When 2 ≤ nsp ≤ 5, the scalar quantities are used to govern the composition of the gas.

Meshing

Within the Simmodeler utility, the mesh can either be created or loaded from an existing .cas file. Below are steps for loading a mesh from a .cas file:

1. Launch Simmodeler (for this example, SimModeler7.0-190604 is used)
2. File > Import Discrete Data > (select .cas file to import) > (keep defaults and click OK) > (select YES to keep volume mesh)
3. Save .sms and .smd files
4. Attributes can now be assigned to the model as normal

Boundary Conditions

Below are the recognized boundary conditions that can be applied for the current version:

• comp1/comp2/comp3 - Specification of one/two/three components of velocity, [m/s]
• temperature - Specification of translational-rotational temperature, [K]. By default, vibrational temperature is held in equilibrium with this value and nonequilibrium is controlled through simulation inputs.
• surfID - When value is set to 702, the boundary is treated as a slip wall. If using this option, include a boundary layer mesh along the surface to ensure the wall normal direction is accurately computed.
• scalar_1 - Mole fraction of species 2 of the gas
• scalar_2 - Mole fraction of species 3 of the gas
• scalar_3 - Mole fraction of species 4 of the gas
• scalar_4 - Mole fraction of species 5 of the gas
• pressure - Specification of static pressure over a surface, [Pa]
  • Used to compute mole fraction of species 1 of the gas with Dalton's Law of partial pressures and subtracting the summation of the other mole fractions from a value of 1
• heat flux - set to zero for adiabatic wall boundary condition

Initial Conditions

Below are the required initial conditions for the current version:

• initial velocity - Components and magnitude of flow velocity, [m/s]
  • If a supersonic outlet condition is used, set such that flow is initialized Mach > 1
• initial temperature - Value used to set translational-rotational temperature, [K]
• initial scalar_1 - Initial value of species 2 mole fraction
• initial scalar_2 - Initial value of species 3 mole fraction
• initial scalar_3 - Initial value of species 4 mole fraction
• initial scalar_4 - Initial value of species 5 mole fraction
• initial pressure - Static pressure of the gas, [Pa]
  • For multi-species flows, this value is used in combination with the initial scalar values to compute the mole fraction of species 1

Simulation Inputs

Example of solver.inp file:

# ibksiz flmpl flmpr itwmod wmodts dmodts fwr taucfct
# PHASTA Version 1.5 Input File
#
#  Basic format is
#
#    Key Phrase  :  Acceptable Value (integer, double, logical, or phrase
#                                     list of integers, list of doubles )
#
#
# ****************** Notes ********************************
# 1. Bulk viscosity set to 0 in common.f (bmu)
# 2. Right now, nsp cannot be anything other than 5
# 3. idiff must be zero for now
# 4. iqtot does nothing for now since source terms are not being handled
#    (commented out call to e3source in e3.f)
# 5.




#SOLUTION CONTROL 
#{                
     Equation of State: Compressible
Number of Timesteps: 1  
Time Step Size: 3.2339656949004e-08  # cfl = 1 is dt = 7.8702386e-8

     Limit Density: 0 0.01 0.1
     Limit u1: 0 0. 2.8e3
     Limit u2: 0 0 0
     Limit u3: 0 0 0
     Limit Temperature: 0 230 3500     !also limits vibrational temperature
#}


#OUTPUT CONTROL
#{
     Number of Timesteps between Restarts: 250   #replaces nout/ntout
     Print Error Indicators: True
     Error Indicator Threshold: 0.01
     Number of Error Smoothing Iterations: 0  #ierrsmooth
     Load and set 3D IC: False
     Position Tolerance on IC Load: 1e-7     # sets the tolerance for matching points
#}


#MATERIAL CONTROL
#{
     Viscosity: 1.95508431704028e-5      #<<<<< this is required to run (value used if nsp.eq.99)
     Thermal Conductivity: 26.6843390135759e-3
     Viscous Control: None    #Viscous   #None

#}




#REACTING FLOW
#{
     Number of species: 1               # nsp
#.......currently only allowing 1<=nsp<=5. 
#.........and make sure scalars passed from simmodeler are in correct slots
#
     Species IDs: 1             # specIDs, length of array must equal
                                        #    nsp (IDs numbered in order:
                                        #            N2,O2,NO,N,O
                                        #   ID:99 for Air molecule
     Ref Entropy Conditions: 1e3 230 230 0   #[P0,T0,T0vib,S0]
     Ref Entropy Species: 1 2           # uses IDs above (NOT ACTIVE YET)
     Ref Entropy Mole Frac: 1 0 0 0 0
     Allow reactions: False             # ichem = 1 if True
     Chemical heat release: False       # iqtot = 1 if True
     Limit on reaction step: 0.00001    # rlim (limits change in species cs per step)
Tolerance to global time: 1.0  #0.01     # ttol
     Temperature threshold: 500         # Tth (below which, reactions ignored)
     Reaction solver MIN steps: 5       # nstepmin
     Reaction solver MAX steps: 100     # nstepmax
     Two Temperature coefficient: 0.5   # qta (Tvib**qta*T**(1-qta))
     Exclude vib energy: True           # ivib0 = 1 if True
     Exclude vib source: True          # ivibS0 = 1 if True
     Tvib BC Ratio: 1.0			# at any BC with T set, Tvib = tvibBC * T
     Vibrational Temperature IC: -1    # set negative value to force Tvib = T
#}



#LINEAR SOLVER
#
     Solver Type: GMRES sparse      <<< default, but why does it have to be set?
     Number of GMRES Sweeps per Solve: 1      # replaces nGMRES
     Minimum Number of Iterations per Nonlinear Iteration: 10  # minIters
     Number of Krylov Vectors per GMRES Sweep: 100	# replaces Kspace    
     Tolerance on Momentum Equations: 0.01        # epstol(1), affects etol for Hessenberg problem

#}

#DISCRETIZATION CONTROL
#{
     Weak Form: SUPG 		# alternate is Galerkin only for compressible
     Time Integration Rule: First Order      # 1st Order sets rinf(1) -1
#     Time Integration Rule: Second Order    # Second Order sets rinf next
#     Time Integration Rho Infinity: 0.5     # rinf(1) Only used for 2nd order
#     Tau Matrix: Diagonal-Franca-Entropy               #itau=4
     Tau Matrix: Matrix-Ent-Adv
#     Tau Matrix: Diagonal-Shakib-Entropy
     Include Viscous Correction in Stabilization: False    # if p=1 idiff=1
                                                           # if p=2 idiff=2  
     Tau Time Constant: 1.0
     Tau C Scale Factor: 1.0                    # taucfct  best value depends
     Number of Elements Per Block: 64       #ibksiz

#}


#DISCONTINUITY CAPTURING
#{
     Discontinuity Capturing: DC-quadratic    # Current Options: DC-mallet, DC-minimum, DC-quadratic, DC-yzbeta
     Multiplier for DC factor: 1     # scales DC variable in e3DC
     Discontinuity Capturing Scheme: 1  #0: discontinuous, 1: continuous (L2 projection)
     Include Source Term in DC: 0            # 1: sets idcSRC to 1
     Write DCqpt: 0
#----Parameters for YZBeta DC operator ----
     Beta Value: 1                       # 1: smoother , 2: sharper, 12: compromise between 1 and 2
     YZB Farfield Conditions: 1e5 2119 10 10 300 # [Pressure, X-Vel, Y-Vel, Z-Vel, Temperature] 
     YZB Farfield Mole Frac: 1 0 0 0 0   # mole fractions at reference condition
                                         # [xN2,xO2,xNO,xN,xO] 
                                         # must sum to 1, must be length 5 
     Include Umod Term: 1                # 0: no, 1: yes
     Mach Adjustment Bm Value: 1         # 0: off,1: smoother shock, 2: sharper shock
     Mach Adjustment Bj Value: 6         # 0: off,1: smoother shock, 2: sharper shock
     Include Time Term in Z: 1           # 0: no, 1: yes
#------------------------------------------
		 

#}





#STEP SEQUENCE 
#{
       Step Construction  : 0 1 0 1
#}