microstructureFoam

Overview

Installation

The current version of the code utilises the OpenFoam10 libraries. The code has been developed and tested using an Ubuntu installation, but should work on any operating system capable of installing OpenFoam. To install the microstructureFoam solver, first follow the instructions on this page: OpenFoam 10 Install to install the OpenFoam 10 libraries.

Then navigate to a working folder in a shell terminal, clone the git code repository, and build.

$ git clone https://github.com/micmog/laserbeamFoam.git laserbeamFoam
$ cd solver
$ wclean
$ wmake

The installation can be tested using the tutorial cases described below.

Tutorial cases

To run any of the tutorials in serial mode:

delete any old simulation files, e.g:
$ rm -r 0* 1* 2* 3* 4* 5* 6* 7* 8* 9*
Then:
$ cp -r initial 0
$ blockMesh
$ setFields
$ TesselateFoam (Optional)
$ microstructureFoam

For parallel deployment, using MPI, following the setFields command:

$ decomposePar
$ mpirun -np 6 microstructureFoam -parallel >log &

for deployment on 6 cores.

Description of case files

nucleationDict

Parameter Name	Value Type	Parameter Description	Unit
Tu_mean	dimensionedScalar	Activation undercooling distribution: mean	K
Tu_stdev	dimensionedScalar	Activation undercooling distribution: standard deviation	K
n_max	dimensionedScalar	Activation undercooling distribution: site density	[sites/m3]
maxItersNucSet	scalar	Maximum iterations allowed when setting nucleation sites	-
nucDistFactor	scalar	Number of interface distances between nucleation sites	-
stopToCheckNucSites	bool	Stop simulation to view the nucleation sites that were set	true/false

LaserProperties

Parameter Name	Value Type	Parameter Description	Unit
V_incident	vector	Initial incidence vector for laser source	-
HS_a	scalar	Laser beam radius	m
HS_bg	scalar	Laser Offset in x axis	m
HS_velocity	scalar	Travel velocity of laser heat source in z direction	m/s
HS_lg	scalar	Laser Offset in z axis	m
HS_Q	scalar	Laser Power	W
wavelength	scalar	Wavelength of incident laser	m
e_num_density	scalar	electron number density of substrate	m^{-3}
elec_resistivity	scalar	Electrical resistivity of substrate

g

Parameter Name	Value Type	Parameter Description	Unit
dimensions	OpenFOAM dimensions	Dimension set used to construct dimensionedVector	m/s
value	vector	Direction and value of gravitational acceleration	m/s2

momentumTransport

Parameter Name	Value Type	Parameter Description	Unit
simulationType	Word	laminar??	-

phaseProperties

Parameter Name	Value Type	Parameter Description	Unit
phases	List[Word]	Names of phases, a separate physicalProperties.[PHASE] dict will be read for each [PHASE]	-
sigma	scalar
dsigmadT	scalar
p0	scalar
Tvap	scalar
Mm	scalar
LatentHeatVap	scalar

PhaseFieldProperties

Parameter Name	Value Type	Parameter Description	Unit
grainNumThreshold	scalar
Aniso_strength	scalar
gamma_pf	scalar
sigma_P	scalar
sigma_G	scalar
lp	scalar
lg	scalar
deltaf_p	scalar
deltaf_p	scalar
D0	scalar
Qg	scalar
sigma_G	scalar
sigma_G	scalar
N_Seeds	int
Xmin	scalar
Xmax	scalar
Ymin	scalar
Ymax	scalar
Zmin	scalar
Zmax	scalar
sigma_G	scalar
sigma_G	scalar
write_ni_all	bool	Set to true by default, to turn off the writing of INACTIVE n.i field, include write_ni_all false;	true/false
write_ni_active	bool	Set to true by default, to turn off the writing of ALL n.i fields, include write_ni_active false; as well as write_ni_all false;	true/false

physicalProperties.[PHASE]

Parameter Name	Value Type	Parameter Description	Unit
viscosityModel	Word
nu	scalar	Dynamic viscosity	Pa.s
rho	scalar	Density	kg/m3
cp	scalar	Specific heat capacity (constant pressure)	J/(kg.K)
cpsolid	scalar	Specific heat capacity...??	J/(kg.K)
kappa	scalar
kappasolid	scalar
Tsolidus	scalar	Solidus temperature	K
Tliquidus	scalar	Liquidus temperature	K
LatentHeat	scalar	Latent heat of solidfification	J/kg
beta	scalar	Bouyancy??

Powder-Bed Fusion Example

.... text to go here ....

Directional-Solidification Example

.... text to go here ....

Algorithm

Initially the solver loads the mesh, reads in fields and boundary conditions, selects the turbulence model (if specified). The main solver loop is then initiated. First, the time step is dynamically modified to ensure numerical stability. Next, the two-phase fluid mixture properties and turbulence quantities are updated. The discretized phase-fraction equation is then solved for a user-defined number of subtime steps (typically 3) using the multidimensional universal limiter with explicit solution solver MULES. This solver is included in the OpenFOAM library, and performs conservative solution of hyperbolic convective transport equations with defined bounds (0 and 1 for α1). Once the updated phase field is obtained, the program enters the pressure–velocity loop, in which p and u are corrected in an alternating fashion. In this loop T is also solved for, such that he buoyancy predictions are correct for the U and p fields. The process of correcting the pressure and velocity fields in sequence is known as pressure implicit with splitting of operators (PISO). In the OpenFOAM environment, PISO is repeated for multiple iterations at each time step. This process is referred to as merged PISO- semi-implicit method for pressure-linked equations (SIMPLE), or the pressure-velocity loop (PIMPLE) process, where SIMPLE is an iterative pressure–velocity solution algorithm. PIMPLE continues for a user specified number of iterations. The main solver loop iterates until program termination. A summary of the simulation algorithm is presented below:

• laserbeamFoam Simulation Algorithm Summary:
  • Initialize simulation data and mesh
  • WHILE t<t_end DO
  • 1. Update delta_t for stability
  • 2. VOF equation sub-cycle
  • 3. Update interface location for heat source application
  • 4. Update fluid properties
  • 5. Ray-Tracing for Heat Source application at the surface
  • 6. PISO Loop
    • 1. Form u equation
    • 2. Energy Transport Loop
      • 1. Solve T equation
      • 2. Update fluid fraction field
      • 3. Re-evaluate source terms due to latent heat
    • 3. PISO
      • 1. Obtain and correct face fluxes
      • 2. Solve p-Poisson equation
      • 3. Correct u
  • 7. Nucleate New Order Parameters if undercooling is achieved
  • 8. Solve Phase-Field Equations
  • 9. Write Fields

There are no constraints on how the computational domain is discretised.

License

OpenFoam, and by extension the laserbeamFoam application, is licensed free and open source only under the GNU General Public Licence version 3. One reason for OpenFOAM’s popularity is that its users are granted the freedom to modify and redistribute the software and have a right of continued free use, within the terms of the GPL.

Acknowledgements

Citing This Work

References