"""Compare peak source temperature in two STEP-meshed heat spreaders.""" 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("Heat spreader volume must be positive") pad0 = cq.Solid.makeBox(10, 40, 10, cq.Vector(0, -20, -5)) pad1 = cq.Solid.makeBox(10, 40, 10, cq.Vector(90, -20, -5)) slabs = [cq.Solid.makeBox(10, 50, 10, cq.Vector(x, -25, -5)) for x in (0, 90)] envelope = cq.Solid.makeBox(100, 50, 10, cq.Vector(0, -25, -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("heat_spreader") 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 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"]) sink_ids = [key for key, point in data["nodes"].items() if abs(point[0]) < 1e-8] source_ids = [key for key, point in data["nodes"].items() if abs(point[0] - 0.1) < 1e-8 and abs(point[1]) <= 0.00501 and abs(point[2]) <= 0.00501] if len(sink_ids) < 4 or len(source_ids) < 4: raise ValueError("Mesh is missing a sink or source patch") nodes = {} for key, point in data["nodes"].items(): node = fea.ChNodeFEAxyzP(ch.ChVector3d(*point)) node.SetFieldVal(setup["sink_temperature_K"]) if key in sink_ids: node.SetFixed(True) if key in source_ids: node.SetLoad(setup["source_power_W"] / len(source_ids)) 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() temperatures = [node.GetFieldVal() for node in nodes.values()] peak_source = max(nodes[int(key)].GetFieldVal() for key in source_ids) peak_rise = peak_source - setup["sink_temperature_K"] if not math.isfinite(peak_rise) or peak_rise <= 0: raise ValueError("Invalid source temperature") results[size] = { "peak_source_temperature_K": peak_source, "peak_source_rise_K": peak_rise, "minimum_temperature_K": min(temperatures), "maximum_temperature_K": max(temperatures), "node_count": len(nodes), "tetrahedron_count": len(data["tets"]), "sink_node_count": len(sink_ids), "source_node_count": len(source_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]["peak_source_rise_K"] for size in sizes] candidate = [gs[size]["peak_source_rise_K"] for size in sizes] reductions = [1 - a / b for a, b in zip(candidate, baseline)] checks = { "baseline_hotspot": min(baseline) >= setup["minimum_baseline_peak_rise_K"], "peak_rise_reduced_both_meshes": min(reductions) >= setup["required_relative_peak_rise_reduction"], "peak_temperature_limited": all( gs[size]["peak_source_temperature_K"] <= setup["maximum_peak_temperature_K"] for size in sizes), "mesh_response_stable": all( abs(values[1] / values[0] - 1) <= setup["maximum_relative_mesh_peak_rise_change"] for values in (baseline, candidate)), "temperature_bounds": all( gs[size]["minimum_temperature_K"] >= setup["sink_temperature_K"] - 1e-6 and gs[size]["maximum_temperature_K"] <= gs[size]["peak_source_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_peak_rise_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"Peak source rise: {baseline} -> {candidate} K") print(f"Task passed: {all(checks.values())}") if not all(checks.values()): raise SystemExit(1) if __name__ == "__main__": main()