User Parameters

The simulation parameters are written step by step by the user. In this section a brief explanation of the main parameters is provided. The Physical Parameters are defined in src/Commons/ParametersDef/Params.jl, where the default values are also provided.

TimeParameters

using SegregatedVMSSolver
using PartitionedArrays,MPI
using SegregatedVMSSolver.ParametersDef
t0 = 0.0
dt = 0.1
tF = 10.0

timep = TimeParameters(t0,dt,tF)

The user can also specify a time_window::Tuple{Float64,Float64} where to compute the average flow-field. The user can specify a t_endramp, the boundary-velocity is then increased from 0.0 up to the target value following a linear law from t0 up to t_endramp, it increases stability.

TimeParameters(t0=t0,dt=dt,tF=tF, t_endramp=2.0, time_window=(5.0,10.0))

PhysicalParameters

Re = 1000
c= 1.0
u_in = [1.0,0.0]
physicalp = PhysicalParameters(Re=Re,c=c,u_in=u_in)

The viscosity ν is computed automatically in this way

physicalp.ν

In case of 3D simulation, the initial velocity should be a 3-elements vector.

u_in = [1.0,0.0,0.0]

SolverParameters

solverp = SolverParameters()

In this example we are using the default parameters. It is possible to supply more detailed options, as reported in the file src/Commons/SolverOptions.jl.

options = petsc_options(vel_ksp="gmres", vel_pc="gamg")
solverp = SolverParameters(petsc_options=options)

The user can specify M the maximum number of internal interations for each time-step and the interval to consider after updating the matrices matrix_freq_update.

solverp = SolverParameters(M=1, matrix_freq_update=10)

MeshParameters

For Cartesian cases (Lid-Driven and Taylor-Green)

D = 2
rank_partition = (2,2)
meshp= MeshParameters(rank_partition,D; N=50,L=0.5)

The mesh information are supplied. D is the dimension of the problem - 2 or 3. In the example a sqare carthesian mesh is created, with 50 divisions on each side, extending from (-0.5,-0.5) up to (0.5,0.5). The rank_partition is a Tuplespecifing how to split the domainin the different directions. In this case 4 processors are necessary.

airfoil_mesh_file = joinpath(@__DIR__,"..", "..", "models", "DU89_2D_A1_M.msh")
meshp= MeshParameters(rank_partition,D,airfoil_mesh_file)

In this example the mesh is created from a .msh file created using Gmsh.

ExportParameters

exportp = ExportParameters()

It is using the default values.

The user can choose to export the initial conditions and/or the mesh. It is useful in preliminary stage of simulation design.

exportp = ExportParameters(printinitial=true,printmodel=true)

The package allows to export the value of velocity, pressure or friction from specific targets on the domain. Example

exportp = ExportParameters(printinitial=true,printmodel=true,name_tags=["airfoil"], fieldexport=[["uh"]])

InitialParameters

intialp = InitialParameters()

The user can specify and initial velocity in the whole domain:

intialp = InitialParameters(u0=[0.5,0.1])

The package allows to re-start a simulation from a previous stored result. It can read a .csv file with the headers: Points_0 Points_1 Points_2 uh_0 uh_1 uh_2 ph. The ph is optional. For each node coordinates x y z the velocity in the 3 directions is specified. Check in folder restarts for examples of files. It is also possible to use a 2D solution to start a 3D simulation.

airfoil_restart_file = joinpath(@__DIR__,"..", "..", "restarts", "BL_DU89_2D_A1_M.csv")
intialp = InitialParameters(airfoil_restart_file)

The initial file can also be created using the advanced boundary layer initialization.