File size: 9,989 Bytes
99510bd | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 | """Compare steady heat flow through two STEP-meshed standoffs."""
import argparse
import hashlib
import json
import math
import subprocess
import sys
from pathlib import Path
ROOT = Path(__file__).resolve().parent
def measure(step: Path, setup: dict) -> dict:
import cadquery as cq
import gmsh
from OCP.BRepGProp import BRepGProp
from OCP.GProp import GProp_GProps
shape = cq.importers.importStep(str(step)).val()
if shape.ShapeType() != "Solid" or not shape.isValid() or len(shape.Solids()) != 1:
raise ValueError(f"Expected one valid solid: {step}")
props = GProp_GProps()
BRepGProp.VolumeProperties_s(shape.wrapped, props)
if props.Mass() <= 0:
raise ValueError("Standoff volume must be positive")
pad0 = cq.Solid.makeBox(10, 20, 10, cq.Vector(0, -10, -5))
pad1 = cq.Solid.makeBox(10, 20, 10, cq.Vector(90, -10, -5))
slabs = [cq.Solid.makeBox(10, 30, 10, cq.Vector(x, -15, -5))
for x in (0, 90)]
envelope = cq.Solid.makeBox(100, 30, 10, cq.Vector(0, -15, -5))
pads = (pad0, pad1)
pad_overlap = sum(pad.intersect(shape).Volume() for pad in pads)
slab_overlap = sum(slab.intersect(shape).Volume() for slab in slabs)
result = {
"step_sha256": hashlib.sha256(step.read_bytes()).hexdigest(),
"volume_mm3": props.Mass(),
"mass_kg": props.Mass() * setup["material_density_kg_m3"] * 1e-9,
"end_pad_missing_mm3": max(0.0, sum(p.Volume() for p in pads) - pad_overlap),
"end_pad_excess_mm3": max(0.0, slab_overlap - pad_overlap),
"envelope_excess_mm3": max(0.0, shape.Volume() -
shape.intersect(envelope).Volume()),
"meshes": {},
}
gmsh.initialize()
try:
gmsh.option.setNumber("General.Terminal", 0)
gmsh.model.add("thermal_standoff")
gmsh.model.occ.importShapes(str(step))
gmsh.model.occ.synchronize()
if len(gmsh.model.getEntities(3)) != 1:
raise ValueError("STEP import must produce one volume")
for size in setup["mesh_sizes_mm"]:
gmsh.model.mesh.clear()
gmsh.option.setNumber("Mesh.CharacteristicLengthMin", size)
gmsh.option.setNumber("Mesh.CharacteristicLengthMax", size)
gmsh.option.setNumber("Mesh.Algorithm3D", 1)
gmsh.model.mesh.generate(3)
tags, coordinates, _ = gmsh.model.mesh.getNodes()
nodes = {str(int(tag)): [coordinates[3 * i + axis] / 1000
for axis in range(3)]
for i, tag in enumerate(tags)}
types, _, element_nodes = gmsh.model.mesh.getElements(3)
tets = []
for kind, connectivity in zip(types, element_nodes):
if kind != 4:
raise ValueError(f"Expected first-order tetrahedra, got {kind}")
tets.extend([[int(value) for value in connectivity[i:i + 4]]
for i in range(0, len(connectivity), 4)])
if not nodes or not tets:
raise ValueError("Gmsh produced an empty mesh")
result["meshes"][str(size)] = {"nodes": nodes, "tets": tets}
finally:
gmsh.finalize()
return result
def dynamics(meshes: dict, setup: dict) -> dict:
import pychrono as ch
import pychrono.fea as fea
import numpy as np
results = {}
for size, data in meshes.items():
system = ch.ChSystemSMC()
system.SetGravitationalAcceleration(ch.ChVector3d(0, 0, 0))
system.SetSolver(ch.ChSolverSparseLU())
mesh = fea.ChMesh()
material = fea.ChContinuumThermal()
material.SetThermalConductivity(
setup["thermal_conductivity_W_m_K"])
material.SetSpecificHeatCapacity(setup["specific_heat_J_kg_K"])
material.SetDensity(setup["material_density_kg_m3"])
hot_ids = [key for key, point in data["nodes"].items()
if abs(point[0]) < 1e-8]
cold_ids = [key for key, point in data["nodes"].items()
if abs(point[0] - 0.1) < 1e-8]
if len(hot_ids) < 4 or len(cold_ids) < 4:
raise ValueError("Mesh is missing a thermal boundary face")
nodes = {}
for key, point in data["nodes"].items():
node = fea.ChNodeFEAxyzP(ch.ChVector3d(*point))
node.SetFieldVal(setup["cold_face_temperature_K"])
if key in hot_ids:
node.SetFieldVal(setup["hot_face_temperature_K"])
node.SetFixed(True)
if key in cold_ids:
node.SetFieldVal(setup["cold_face_temperature_K"])
node.SetFixed(True)
mesh.AddNode(node)
nodes[int(key)] = node
for a, b, c, d in data["tets"]:
element = fea.ChElementTetraCorot_4_P()
element.SetNodes(nodes[a], nodes[b], nodes[c], nodes[d])
element.SetMaterial(material)
mesh.AddElement(element)
system.Add(mesh)
system.DoStaticLinear()
energy_rate_over_temperature = 0.0
for tetrahedron in data["tets"]:
positions = np.array([data["nodes"][str(key)]
for key in tetrahedron])
temperatures = np.array([nodes[key].GetFieldVal()
for key in tetrahedron])
edges = positions[1:] - positions[0]
gradient = np.linalg.solve(edges,
temperatures[1:] - temperatures[0])
volume = abs(np.linalg.det(edges)) / 6
energy_rate_over_temperature += (
setup["thermal_conductivity_W_m_K"] *
float(np.dot(gradient, gradient)) * volume)
delta_t = (setup["hot_face_temperature_K"] -
setup["cold_face_temperature_K"])
heat_flow = energy_rate_over_temperature / delta_t
temperatures = [node.GetFieldVal() for node in nodes.values()]
if not math.isfinite(heat_flow) or heat_flow <= 0:
raise ValueError("Invalid steady heat flow")
results[size] = {
"steady_heat_flow_W": heat_flow,
"minimum_temperature_K": min(temperatures),
"maximum_temperature_K": max(temperatures),
"node_count": len(nodes),
"tetrahedron_count": len(data["tets"]),
"hot_node_count": len(hot_ids),
"cold_node_count": len(cold_ids),
}
return results
def invoke(python: str, phase: str, payload: dict) -> dict:
run = subprocess.run([python, str(Path(__file__).resolve()), "--phase", phase],
input=json.dumps(payload), text=True, capture_output=True)
if run.returncode:
raise RuntimeError(f"{phase} failed:\n{run.stderr[-1600:]}")
return json.loads(run.stdout)
def main() -> None:
parser = argparse.ArgumentParser()
parser.add_argument("--cad-python", default=sys.executable)
parser.add_argument("--physics-python", default=sys.executable)
parser.add_argument("--phase", choices=("measure", "dynamics"))
args = parser.parse_args()
if args.phase:
payload = json.load(sys.stdin)
result = (measure(Path(payload["step"]), payload["setup"])
if args.phase == "measure"
else dynamics(payload["meshes"], payload["setup"]))
print(json.dumps(result))
return
setup = json.loads((ROOT / "setup.json").read_text())
results = {}
for name in ("before", "after"):
properties = invoke(args.cad_python, "measure", {
"step": str(ROOT / f"{name}.step"), "setup": setup,
})
meshes = properties.pop("meshes")
results[name] = {
"step_properties": properties,
"simulation_result": invoke(args.physics_python, "dynamics", {
"meshes": meshes, "setup": setup,
}),
}
before = results["before"]
after = results["after"]
bp, ap = before["step_properties"], after["step_properties"]
bs, gs = before["simulation_result"], after["simulation_result"]
sizes = [str(size) for size in setup["mesh_sizes_mm"]]
baseline = [bs[size]["steady_heat_flow_W"] for size in sizes]
candidate = [gs[size]["steady_heat_flow_W"] for size in sizes]
reductions = [1 - a / b for a, b in zip(candidate, baseline)]
checks = {
"baseline_conducts_heat": min(baseline) >=
setup["minimum_baseline_heat_flow_W"],
"heat_flow_reduced_both_meshes": min(reductions) >=
setup["required_relative_heat_flow_reduction"],
"mesh_response_stable": all(
abs(values[1] / values[0] - 1) <=
setup["maximum_relative_mesh_heat_flow_change"]
for values in (baseline, candidate)),
"temperature_bounds": all(
gs[size]["minimum_temperature_K"] >=
setup["cold_face_temperature_K"] - 1e-6 and
gs[size]["maximum_temperature_K"] <=
setup["hot_face_temperature_K"] + 1e-6
for size in sizes),
"mass_fixed": abs(ap["mass_kg"] / bp["mass_kg"] - 1) <=
setup["maximum_relative_mass_change"],
"end_pads_fixed": ap["end_pad_missing_mm3"] <=
setup["maximum_end_pad_missing_mm3"] and
ap["end_pad_excess_mm3"] <= setup["maximum_end_pad_excess_mm3"],
"envelope_fixed": ap["envelope_excess_mm3"] <=
setup["maximum_envelope_excess_mm3"],
}
after["comparison_to_before"] = {
"relative_heat_flow_reductions": reductions,
"checks": checks, "passed": all(checks.values()),
}
for name, result in results.items():
(ROOT / f"{name}.results.json").write_text(json.dumps(result, indent=2) + "\n")
print(f"Steady heat flow: {baseline} -> {candidate} W")
print(f"Task passed: {all(checks.values())}")
if not all(checks.values()):
raise SystemExit(1)
if __name__ == "__main__":
main()
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