default.params

# # default.params
# Default parameter set for drop impact simulations.
# Format: key=value (one per line, # for comments).
# This file provides a typical water-air drop impact configuration.

# ============================================================
# Case Identification
# ============================================================
# Case number for folder naming (4-digit: 1000-9999)
# Output will be created in simulationCases/<CaseNo>/
CaseNo=1000

# ============================================================
# Physical Parameters (Dimensionless Numbers)
# ============================================================
# Weber number: We = ρU²R/σ (inertia vs surface tension)
We=10.0

# Ohnesorge number (drop): Oh = μ/√(ρσR) (viscous vs surface tension)
Ohd=1.0e-2

# Ohnesorge number (surrounding gas)
Ohs=1.0e-5

# Density ratio: ρ_gas/ρ_drop (air-water ≈ 1e-3)
rho_ratio=1.0e-3

# Computed Reynolds number: Re = √We/Oh ≈ 100

# ============================================================
# Geometry Configuration
# ============================================================
# Domain size in drop radii (must be >> drop radius to avoid boundary effects)
Ldomain=8.0

# Initial drop center position (radial coordinate, in drop radii)
# Should be > 0 to avoid axis, and > drop_radius to avoid overlap with surface
drop_x=1.05

# Initial drop center position (axial coordinate, height above surface)
# Set to drop_radius for drop just touching surface at t=0
drop_y=0.0

# Drop radius (normalized, typically 1.0)
drop_radius=1.0

# Initial impact velocity (negative = downward toward surface)
# Magnitude of 1.0 corresponds to unit Weber number scaling
impact_velocity=-1.0

# ============================================================
# Numerical Parameters (Mesh Adaptation)
# ============================================================
# Maximum refinement level (2^MAXlevel cells at finest resolution)
# Level 10 → 1024 cells, Level 11 → 2048 cells, etc.
# Higher = more accurate but slower
MAXlevel=14

# Minimum refinement level (coarsest allowed)
# Typically 4-5 for axisymmetric simulations
MINlevel=6

# Initial grid level (before adaptation)
# Start coarse, adaptation will refine where needed
init_grid_level=6

# VOF field error tolerance
# Controls interface resolution (smaller = finer mesh at interface)
fErr=1.0e-3

# Curvature error tolerance
# Important for surface tension accuracy
KErr=1.0e-4

# Velocity error tolerance
# Controls resolution of flow features
VelErr=1.0e-2

# ============================================================
# Time Control
# ============================================================
# Maximum simulation time in CONVECTIVE TIME UNITS
# Actual simulation: tmax_sim = tmax * sqrt(We)
#
# Physical basis: Convective timescale τ_c = R/U ~ sqrt(We) in normalized units
# Example: tmax=1, We=10 → simulation runs until t ≈ 3.16
#
tmax=1e0

# Snapshot interval for dump files
# Balance between temporal resolution and storage
tsnap=0.01

# ============================================================
# Output Configuration
# ============================================================
# Output directory name
# Will be created if it doesn't exist
output_dir=results

# Statistics logging interval (iterations)
# Write log entry every N timesteps (1 = every step)
log_interval=1

# ============================================================
# Advanced: Outflow Boundary Control
# ============================================================
# Unrefine mesh if x > outflow_x_max (in drop radii)
# Prevents wasted resolution far from drop
outflow_x_max=4.0

# Unrefine mesh if y > outflow_y_max (in drop radii)
# Far-field boundary where solution should be simple
outflow_y_max=8.0