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Periodic Immersed Boundary Wrapping for Circular and Spherical Geometries #1117

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8906810
periodic ib wrapping for spheres
conraddelgado Jan 28, 2026
837b18b
periodic ib wrap for circle geometry + tests
conraddelgado Jan 28, 2026
3441ef4
Merge branch 'MFlowCode:master' into master
conraddelgado Jan 28, 2026
6338eea
formatting
conraddelgado Jan 28, 2026
1aa4b08
Merge branch 'master' of github.com:conraddelgado/periodic_ibs
conraddelgado Jan 28, 2026
8571caf
regenerate test data, gpu update
conraddelgado Jan 30, 2026
85903b3
formatting
conraddelgado Jan 30, 2026
067a337
r2 on GPU
conraddelgado Jan 30, 2026
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141 changes: 141 additions & 0 deletions examples/2D_ibm_circle_periodic/case.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,141 @@
import json
import math
import numpy as np

gam_a = 1.4

# sphere diameter
D = 0.1

# circle density
rho_c = 200

# domain length
L = 10 * D

# mach number
M = 1.2

# reynolds number
Re = 400.0

# pressure
P = 101325

# density
rho = 1.0

# fluid velocity
v1 = M * np.sqrt(gam_a * P / rho)

# dynamic viscosity
mu = rho * v1 * D / Re

dt = 1.0e-06
Nt = 5000
t_save = 20

# to fully resolve requires 40-60 cells across sphere diameter
Nx = 511
Ny = Nx
Comment on lines +38 to +40
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@coderabbitai coderabbitai bot Jan 30, 2026

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⚠️ Potential issue | 🟡 Minor

Minor doc fix: “sphere” → “circle.”

This is a 2D circle case, so the resolution comment should reference a circle.

✏️ Suggested edit 
-# to fully resolve requires 40-60 cells across sphere diameter
+# to fully resolve requires 40-60 cells across circle diameter
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
# to fully resolve requires 40-60 cells across sphere diameter
Nx = 511
Ny = Nx
# to fully resolve requires 40-60 cells across circle diameter
Nx = 511
Ny = Nx
🤖 Prompt for AI Agents 
In `@examples/2D_ibm_circle_periodic/case.py` around lines 38 - 40, The inline
comment above the grid size (near Nx and Ny variables) incorrectly refers to a
"sphere"; update that comment to say "circle" since this is a 2D case (e.g.,
change the comment string "# to fully resolve requires 40-60 cells across sphere
diameter" to use "circle" instead). Ensure the wording remains accurate and
brief and that it sits immediately above or next to the Nx/Ny declarations
(symbols: Nx, Ny).

Nz = 0

# immersed boundary dictionary
ib_dict = {}
ib_dict.update(
{
f"patch_ib({1})%geometry": 2,
f"patch_ib({1})%x_centroid": 0.5 * L,
f"patch_ib({1})%y_centroid": 0.5 * L,
f"patch_ib({1})%radius": D / 2,
f"patch_ib({1})%slip": "F",
f"patch_ib({1})%moving_ibm": 0,
f"patch_ib({1})%mass": rho_c * np.pi * (D / 2.0) ** 2,
}
)

# Configuring case dictionary
case_dict = {
# Logistics
"run_time_info": "T",
# Computational Domain Parameters
# x direction
"x_domain%beg": -5.0 * D,
"x_domain%end": 5.0 * D,
# y direction
"y_domain%beg": -5.0 * D,
"y_domain%end": 5.0 * D,
"cyl_coord": "F",
"m": Nx,
"n": Ny,
"p": Nz,
"dt": dt,
"t_step_start": 0,
"t_step_stop": Nt,
"t_step_save": t_save,
# Simulation Algorithm Parameters
# Only one patch is necessary for one fluid
"num_patches": 1,
# Use the 5 equation model
"model_eqns": 2,
# 6 equations model does not need the K \div(u) term
"alt_soundspeed": "F",
# One fluids: air
"num_fluids": 1,
# time step
"mpp_lim": "F",
# Correct errors when computing speed of sound
"mixture_err": "T",
# Use TVD RK3 for time marching
"time_stepper": 3,
# Reconstruct the primitive variables to minimize spurious
# Use WENO5
"weno_order": 5,
"weno_eps": 1.0e-14,
"weno_Re_flux": "T",
"weno_avg": "T",
"avg_state": 2,
"mapped_weno": "T",
"null_weights": "F",
"mp_weno": "T",
"riemann_solver": 2,
"wave_speeds": 1,
# periodic bc
"bc_x%beg": -1,
"bc_x%end": -1,
"bc_y%beg": -1,
"bc_y%end": -1,
# Set IB to True and add 1 patch for every sphere
"ib": "T",
"num_ibs": 1,
"viscous": "T",
# Formatted Database Files Structure Parameters
"format": 1,
"precision": 2,
"prim_vars_wrt": "T",
"E_wrt": "T",
"parallel_io": "T",
# Patch: square filled with air
"patch_icpp(1)%geometry": 3,
# Uniform properties, centroid is at the center of the domain
"patch_icpp(1)%x_centroid": 0.0,
"patch_icpp(1)%y_centroid": 0.0,
"patch_icpp(1)%length_x": 10 * D,
"patch_icpp(1)%length_y": 10 * D,
# Specify the patch primitive variables
"patch_icpp(1)%vel(1)": v1,
"patch_icpp(1)%vel(2)": 0.0,
"patch_icpp(1)%pres": P,
"patch_icpp(1)%alpha_rho(1)": rho,
"patch_icpp(1)%alpha(1)": 1.0e00,
# Fluids Physical Parameters
"fluid_pp(1)%gamma": 1.0e00 / (gam_a - 1.0e00), # 2.50(Not 1.40)
"fluid_pp(1)%pi_inf": 0,
"fluid_pp(1)%Re(1)": 1.0 / mu,
# ibs wrap around domain
"periodic_ibs": "T",
}

case_dict.update(ib_dict)

print(json.dumps(case_dict))
150 changes: 150 additions & 0 deletions examples/3D_ibm_sphere_periodic/case.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,150 @@
import json
import math
import numpy as np

gam_a = 1.4

# sphere diameter
D = 0.1

# sphere density
rho_s = 200

# domain length
L = 10 * D

# mach number
M = 1.2

# reynolds number
Re = 400.0

# pressure
P = 101325

# density
rho = 1.0

# fluid velocity
v1 = M * np.sqrt(gam_a * P / rho)

# dynamic viscosity
mu = rho * v1 * D / Re

dt = 2.0e-06
Nt = 2000
t_save = Nt // 250

# to fully resolve requires 40-60 cells across sphere diameter
Nx = 127
Ny = Nx
Nz = Ny
Comment on lines +38 to +41
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⚠️ Potential issue | 🟡 Minor

Align the resolution comment with the chosen grid.

With L=1 and Nx=127, the sphere diameter spans ~13 cells, not 40–60. Consider updating the comment to avoid confusion.

💡 Suggested comment tweak 
-# to fully resolve requires 40-60 cells across sphere diameter
+# NOTE: fully resolving needs 40–60 cells across diameter; this example uses ~13 for faster runs
🤖 Prompt for AI Agents 
In `@examples/3D_ibm_sphere_periodic/case.py` around lines 38 - 41, The comment
about required resolution is inconsistent with the grid settings: with L = 1 and
Nx = 127 (Ny = Nz = Nx), the sphere diameter covers roughly 13 cells, not 40–60;
update the comment above the Nx/Ny/Nz definitions (referencing Nx, Ny, Nz and L)
to either state the actual cells-per-diameter for this grid (~13) or note that
40–60 cells would require increasing Nx accordingly, so the comment accurately
reflects the chosen resolution.


# immersed boundary dictionary
ib_dict = {}
ib_dict.update(
{
f"patch_ib({1})%geometry": 8,
f"patch_ib({1})%x_centroid": 0.5 * L,
f"patch_ib({1})%y_centroid": 0.5 * L,
f"patch_ib({1})%z_centroid": 0.5 * L,
f"patch_ib({1})%radius": D / 2,
f"patch_ib({1})%slip": "F",
f"patch_ib({1})%moving_ibm": 0,
f"patch_ib({1})%mass": rho_s * 4.0 / 3.0 * np.pi * (D / 2.0) ** 3,
}
)

# Configuring case dictionary
case_dict = {
# Logistics
"run_time_info": "T",
# Computational Domain Parameters
# x direction
"x_domain%beg": -5.0 * D,
"x_domain%end": 5.0 * D,
# y direction
"y_domain%beg": -5.0 * D,
"y_domain%end": 5.0 * D,
# z direction
"z_domain%beg": -5.0 * D,
"z_domain%end": 5.0 * D,
"cyl_coord": "F",
"m": Nx,
"n": Ny,
"p": Nz,
"dt": dt,
"t_step_start": 0,
"t_step_stop": Nt,
"t_step_save": t_save,
# Simulation Algorithm Parameters
# Only one patch is necessary for one fluid
"num_patches": 1,
# Use the 5 equation model
"model_eqns": 2,
# 6 equations model does not need the K \div(u) term
"alt_soundspeed": "F",
# One fluids: air
"num_fluids": 1,
# time step
"mpp_lim": "F",
# Correct errors when computing speed of sound
"mixture_err": "T",
# Use TVD RK3 for time marching
"time_stepper": 3,
# Reconstruct the primitive variables to minimize spurious
# Use WENO5
"weno_order": 5,
"weno_eps": 1.0e-14,
"weno_Re_flux": "T",
"weno_avg": "T",
"avg_state": 2,
"mapped_weno": "T",
"null_weights": "F",
"mp_weno": "T",
"riemann_solver": 2,
"wave_speeds": 1,
# periodic bc
"bc_x%beg": -1,
"bc_x%end": -1,
"bc_y%beg": -1,
"bc_y%end": -1,
"bc_z%beg": -1,
"bc_z%end": -1,
# Set IB to True and add 1 patch for every sphere
"ib": "T",
"num_ibs": 1,
"viscous": "T",
# Formatted Database Files Structure Parameters
"format": 1,
"precision": 2,
"prim_vars_wrt": "T",
"E_wrt": "T",
"parallel_io": "T",
# Patch: cube filled with air
"patch_icpp(1)%geometry": 9,
# Uniform properties, centroid is at the center of the domain
"patch_icpp(1)%x_centroid": 0.0,
"patch_icpp(1)%y_centroid": 0.0,
"patch_icpp(1)%z_centroid": 0.0,
"patch_icpp(1)%length_x": 10 * D,
"patch_icpp(1)%length_y": 10 * D,
"patch_icpp(1)%length_z": 10 * D,
# Specify the patch primitive variables
"patch_icpp(1)%vel(1)": v1,
"patch_icpp(1)%vel(2)": 0.0e00,
"patch_icpp(1)%vel(3)": 0.0e00,
"patch_icpp(1)%pres": P,
"patch_icpp(1)%alpha_rho(1)": rho,
"patch_icpp(1)%alpha(1)": 1.0e00,
# Fluids Physical Parameters
"fluid_pp(1)%gamma": 1.0e00 / (gam_a - 1.0e00), # 2.50(Not 1.40)
"fluid_pp(1)%pi_inf": 0,
"fluid_pp(1)%Re(1)": 1.0 / mu,
# ibs wrap around domain
"periodic_ibs": "T",
}

case_dict.update(ib_dict)

print(json.dumps(case_dict))
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