Input File Reference

All simulation parameters are defined in fortran_new/inputfile/input_param.txt. The file uses Fortran namelist format.

File Structure

The input file has two sections:

1. Geometry block (free-format, line-by-line)
2. Namelist blocks (&name ... / format)

Geometry Parameters

The geometry is defined by zones in each direction. Each zone has a length, number of control volumes, and power-law exponent for grid stretching.

nzx                          ! number of x-zones (max 7)
xzone(1), xzone(2), ...     ! length of each zone (m)
ncvx(1), ncvx(2), ...       ! number of CVs in each zone
powrx(1), powrx(2), ...     ! power-law exponents (1=uniform, >1=cluster at end, <0=cluster at start)

Same pattern repeated for y (nzy) and z (nzz).

Example (current setup):

Direction	Zones	Lengths	CVs	Exponents	Total
x	1	4.0 mm	400	1 (uniform)	400 cells
y	1	4.0 mm	400	1 (uniform)	400 cells
z	2	0.5 mm + 0.2 mm	10 + 40	-1.5, 1	50 cells

The z-direction uses two zones: a substrate zone (0.5 mm, coarse, clustered toward top) and a powder/build zone (0.2 mm, fine, uniform). Total domain: 4 mm x 4 mm x 0.7 mm.

Grid Stretching

Power-law exponent controls cell clustering:

• powr = 1: uniform spacing
• powr > 1: cells cluster toward the end of the zone
• powr < 0: cells cluster toward the start of the zone (e.g., -1.5 clusters z-cells toward the substrate-powder interface)

Namelist Blocks

&process_parameters — Surface Laser Source

Parameter	Unit	Description
alaspow	W	Surface laser power (set to 0 when using volumetric source)
alaseta	-	Surface laser absorption efficiency
alasrb	m	Laser beam radius (1/e^2)
alasfact	-	Gaussian factor (typically 2 for 1/e^2 definition)

&volumetric_parameters — Volumetric Heat Source

Parameter	Unit	Description
alaspowvol	W	Volumetric laser power
alasetavol	-	Volumetric absorption efficiency
sourcerad	m	Source radius (Gaussian 1/e^2)
sourcedepth	m	Source penetration depth

Note

Either surface (alaspow) or volumetric (alaspowvol) source is used. Set the unused one to 0. The volumetric source distributes heat as:

\[q(x,y,z) = \frac{P \cdot \eta \cdot f}{\pi r_s^2 \cdot d_s} \exp\left(-\frac{f}{r_s^2}\left[(x-x_b)^2 + (y-y_b)^2\right]\right)\]

&material_properties — Primary Material (C=1)

Parameter	Unit	Description	Example
dens	kg/m^3	Solid density	8440
denl	kg/m^3	Liquid density	7640
viscos	Pa*s	Dynamic viscosity (liquid)	0.007
tsolid	K	Solidus temperature	1563
tliquid	K	Liquidus temperature	1623
tboiling	K	Boiling/vaporization temperature	2650
hlatnt	J/kg	Latent heat of fusion	290000
acpa	J/(kg*K^2)	Solid specific heat coefficient (quadratic term)	0.2441
acpb	J/(kg*K)	Solid specific heat coefficient (linear term)	338.59
acpl	J/(kg*K)	Liquid specific heat (constant)	709.25
thconsa	W/(m*K^2)	Solid thermal conductivity coefficient (linear term)	0.0155
thconsb	W/(m*K)	Solid thermal conductivity coefficient (constant term)	5.0435
thconl	W/(m*K)	Liquid thermal conductivity (constant)	30.078
beta	1/K	Thermal expansion coefficient (for buoyancy)	5e-5
emiss	-	Surface emissivity (for radiative loss)	0.3
dgdtp	N/(m*K)	dg/dT — thermal Marangoni coefficient	-3.8e-4

Specific Heat Model

Solid specific heat is temperature-dependent: \(c_p(T) = a \cdot T + b\) where acpa = \(a\), acpb = \(b\). The enthalpy-temperature curve is:

• Solid (\(T \leq T_s\)): \(H = \frac{a}{2}T^2 + bT\)
• Mushy (\(T_s < T < T_l\)): linear interpolation between \(H_s\) and \(H_l\)
• Liquid (\(T \geq T_l\)): \(H = H_l + c_{p,l}(T - T_l)\)

&powder_properties — Powder Layer

Parameter	Unit	Description	Example
layerheight	m	Powder layer thickness	0.04e-3
pden	kg/m^3	Powder density (accounts for porosity)	4330
pcpa	J/(kg*K^2)	Powder specific heat (quadratic)	0.2508
pcpb	J/(kg*K)	Powder specific heat (linear)	357.7
pthcona	W/(m*K^2)	Powder conductivity (linear)	0
pthconb	W/(m*K)	Powder conductivity (constant)	0.995

Powder properties apply to cells in the top layerheight of the domain that have not yet been melted (solidfield <= 0.5).

&numerical_relax — Solver Parameters

Parameter	Unit	Description	Example
maxit	-	Max iterations per time step	60
delt	s	Time step size	2e-5
timax	s	Total simulation time	0.09
urfu	-	Under-relaxation factor for u-velocity	0.7
urfv	-	Under-relaxation factor for v-velocity	0.7
urfw	-	Under-relaxation factor for w-velocity	0.7
urfp	-	Under-relaxation factor for pressure	0.7
urfh	-	Under-relaxation factor for enthalpy	0.7

&boundary_conditions — Thermal Boundaries

Parameter	Unit	Description	Example
htci	W/(m^2*K)	Convection coefficient on x-faces (west/east)	5
htcj	W/(m^2*K)	Convection coefficient on y-faces (north/south)	5
htck1	W/(m^2*K)	Convection coefficient on bottom face	5
htckn	W/(m^2*K)	Convection coefficient on top face	5
tempWest	K	Far-field temperature at west boundary	293
tempEast	K	Far-field temperature at east boundary	293
tempNorth	K	Far-field temperature at north boundary	293
tempBottom	K	Far-field temperature at bottom boundary	293
tempPreheat	K	Initial/preheat temperature	293
tempAmb	K	Ambient temperature (for radiation)	293

The top surface uses combined convection + radiation: $\(q_{loss} = h(T - T_{amb}) + \epsilon \sigma (T^4 - T_{amb}^4)\)$

&local_solver — Adaptive Solver

Parameter	Unit	Description	Example
localnum	-	Number of local steps between global steps	4
local_half_x	m	Half-width of local region in x	1.0e-3
local_half_y	m	Half-width of local region in y	2.0e-4
local_depth_z	m	Depth of local region in z	2.0e-4

The local solver only updates enthalpy in a small region around the melt pool for localnum consecutive steps, then solves the full domain. This provides significant speedup (typically 3-5x) with minimal accuracy loss.

&output_control — Output Settings

Parameter	Unit	Description	Example
outputintervel	steps	VTK output frequency (every N time steps)	50
case_name	-	Case identifier (sets output directory name)	'testcase'
toolpath_file	-	Path to toolpath file (.crs)	'./ToolFiles/B26.crs'
species_flag	-	Enable species transport (0=off, 1=on)	0