上传PythonModels文件

PythonModels/systems/__init__.py

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+"""System assembly modules."""
+

PythonModels/systems/testmodel.py

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+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Any
+
+from PythonModels.components.cylinder import Cylinder
+from PythonModels.components.orifice import Orifice
+from PythonModels.components.pipe import Pipe
+from PythonModels.components.tank import Tank
+from PythonModels.components.tee import Tee
+from PythonModels.core.medium import IdealGasMedium
+from PythonModels.core.network import SimulationNetwork
+from PythonModels.core.solver import SolveIVPConfig, integrate_ode
+from PythonModels.systems.testmodel_closure import (
+    BranchClosureComponents,
+    InitializationDiagnostics,
+    TestModelClosure,
+    TestModelClosureComponents,
+    TestModelSnapshot,
+)
+
+
+@dataclass(frozen=True)
+class CylinderConfig:
+    volume: float = 0.01
+    p0: float = 35e6
+    T0: float = 300.0
+
+
+@dataclass(frozen=True)
+class OrificeConfig:
+    K: float = 1e-5
+
+
+@dataclass(frozen=True)
+class TankConfig:
+    volume: float = 0.1
+    p0: float = 1e5
+    T0: float = 300.0
+
+
+@dataclass(frozen=True)
+class PipeConfig:
+    length: float = 5.0
+    diameter: float = 0.02
+    lambda_darcy: float = 0.02
+    p0: float = 1e5
+    T0: float = 300.0
+
+
+@dataclass(frozen=True)
+class BranchConfig:
+    orifice: OrificeConfig = field(default_factory=OrificeConfig)
+    pipe: PipeConfig = field(default_factory=PipeConfig)
+
+
+@dataclass(frozen=True)
+class TestModelConfig:
+    cylinder: CylinderConfig = field(default_factory=CylinderConfig)
+    upper_branch: BranchConfig = field(default_factory=BranchConfig)
+    lower_branch: BranchConfig = field(default_factory=BranchConfig)
+    tank: TankConfig = field(default_factory=TankConfig)
+
+
+class TestModelSystem:
+    """Runnable first-pass Python system for the current Testmodel topology.
+
+    This version keeps the component split from the Modelica model while keeping
+    the downstream tee-tank pressure coupling in the ODE framework. The original
+    Modelica system is a tighter DAE because both pipe outlets discharge into an
+    ideal lossless junction directly connected to the tank. Here the branch
+    outlet flows are solved from a pressure-consistent energy balance so the
+    outlet is no longer driven by an arbitrary conductance parameter.
+    """
+
+    def __init__(
+        self,
+        medium: IdealGasMedium | None = None,
+        config: TestModelConfig | None = None,
+    ) -> None:
+        self.medium = medium or IdealGasMedium()
+        self.config = config or TestModelConfig()
+
+        self.mycylinder = Cylinder(
+            name="mycylinder",
+            medium=self.medium,
+            V=self.config.cylinder.volume,
+            p0=self.config.cylinder.p0,
+            T0=self.config.cylinder.T0,
+        )
+        self.mytee = Tee(name="mytee")
+        self.myorifice = Orifice(name="myorifice", K=self.config.upper_branch.orifice.K)
+        self.mypipe = Pipe(
+            name="mypipe",
+            medium=self.medium,
+            L=self.config.upper_branch.pipe.length,
+            D=self.config.upper_branch.pipe.diameter,
+            lambda_darcy=self.config.upper_branch.pipe.lambda_darcy,
+            p0=self.config.upper_branch.pipe.p0,
+            T0=self.config.upper_branch.pipe.T0,
+        )
+        self.myorifice1 = Orifice(name="myorifice1", K=self.config.lower_branch.orifice.K)
+        self.mypipe1 = Pipe(
+            name="mypipe1",
+            medium=self.medium,
+            L=self.config.lower_branch.pipe.length,
+            D=self.config.lower_branch.pipe.diameter,
+            lambda_darcy=self.config.lower_branch.pipe.lambda_darcy,
+            p0=self.config.lower_branch.pipe.p0,
+            T0=self.config.lower_branch.pipe.T0,
+        )
+        self.mytee1 = Tee(name="mytee1")
+        self.mytank = Tank(
+            name="mytank",
+            medium=self.medium,
+            V=self.config.tank.volume,
+            p0=self.config.tank.p0,
+            T0=self.config.tank.T0,
+        )
+
+        self.network = SimulationNetwork(name="Testmodel")
+        for component in (
+            self.mycylinder,
+            self.mytee,
+            self.myorifice,
+            self.mypipe,
+            self.myorifice1,
+            self.mypipe1,
+            self.mytee1,
+            self.mytank,
+        ):
+            self.network.add_component(component)
+
+        self.network.connect("mycylinder", "port_b", "mytee", "port_in")
+        self.network.connect("mytee", "port_out1", "myorifice", "port_a")
+        self.network.connect("myorifice", "port_b", "mypipe", "port_a")
+        self.network.connect("mypipe", "port_b", "mytee1", "port_out2")
+        self.network.connect("mytee", "port_out2", "myorifice1", "port_a")
+        self.network.connect("myorifice1", "port_b", "mypipe1", "port_a")
+        self.network.connect("mypipe1", "port_b", "mytee1", "port_out1")
+        self.network.connect("mytee1", "port_in", "mytank", "port_a")
+
+        self.closure = TestModelClosure(
+            medium=self.medium,
+            components=TestModelClosureComponents(
+                cylinder=self.mycylinder,
+                upstream_tee=self.mytee,
+                upper_branch=BranchClosureComponents(
+                    name="upper_branch",
+                    orifice=self.myorifice,
+                    pipe=self.mypipe,
+                ),
+                lower_branch=BranchClosureComponents(
+                    name="lower_branch",
+                    orifice=self.myorifice1,
+                    pipe=self.mypipe1,
+                ),
+                downstream_tee=self.mytee1,
+                tank=self.mytank,
+            ),
+            initial_state_vector=self.initial_state_vector,
+            apply_state_vector=self.apply_state_vector,
+        )
+
+    def initial_state_vector(self) -> list[float]:
+        return self.network.initial_state_vector()
+
+    def apply_state_vector(self, values: list[float]) -> None:
+        self.network.apply_state_vector(values)
+
+    def consistent_initial_state_vector(self) -> list[float]:
+        return self.closure.consistent_initial_state_vector()
+
+    @property
+    def last_solve_diagnostics(self):
+        return self.closure.last_solve_diagnostics
+
+    def initialize_consistent_state(
+        self,
+        max_iterations: int = 12,
+        state_tolerance: float = 1e-9,
+        flow_tolerance: float = 1e-9,
+        enthalpy_tolerance: float = 1e-6,
+        pressure_tolerance: float = 1e-6,
+        strict_internal_solvers: bool = False,
+    ) -> InitializationDiagnostics:
+        return self.closure.initialize_consistent_state(
+            max_iterations=max_iterations,
+            state_tolerance=state_tolerance,
+            flow_tolerance=flow_tolerance,
+            enthalpy_tolerance=enthalpy_tolerance,
+            pressure_tolerance=pressure_tolerance,
+            strict_internal_solvers=strict_internal_solvers,
+        )
+
+    def project_downstream_pressure_constraints(self, *, strict: bool = False) -> None:
+        self.closure.project_downstream_pressure_constraints(strict=strict)
+
+    def snapshot(
+        self,
+        state_vector: list[float] | None = None,
+        *,
+        strict: bool = False,
+    ) -> TestModelSnapshot:
+        return self.closure.snapshot(state_vector, strict=strict)
+
+    def rhs(self, _t: float, state_vector: list[float]) -> list[float]:
+        return self.closure.rhs(state_vector)
+
+    @staticmethod
+    def _legacy_branch_series_key_map() -> tuple[tuple[str, str, str], tuple[str, str, str]]:
+        return (
+            ("upper_branch", "branch_upper.in", "branch_upper.out"),
+            ("lower_branch", "branch_lower.in", "branch_lower.out"),
+        )
+
+    @classmethod
+    def _legacy_branch_series_keys_by_name(cls) -> dict[str, tuple[str, str]]:
+        return {
+            branch_name: (inlet_key, outlet_key)
+            for branch_name, inlet_key, outlet_key in cls._legacy_branch_series_key_map()
+        }
+
+    @staticmethod
+    def _generic_branch_series_keys(branch_name: str) -> tuple[str, str, str]:
+        return (
+            f"branch.{branch_name}.p",
+            f"branch.{branch_name}.in",
+            f"branch.{branch_name}.out",
+        )
+
+    @staticmethod
+    def _legacy_branch_pressure_keys_by_name() -> dict[str, str]:
+        return {
+            "upper_branch": "mypipe.p",
+            "lower_branch": "mypipe1.p",
+        }
+
+    @classmethod
+    def _append_legacy_branch_series_aliases(
+        cls,
+        series: dict[str, list[float]],
+    ) -> dict[str, list[float]]:
+        legacy_branch_series_keys = cls._legacy_branch_series_keys_by_name()
+        legacy_branch_pressure_keys = cls._legacy_branch_pressure_keys_by_name()
+        for branch_name, (legacy_inlet_key, legacy_outlet_key) in legacy_branch_series_keys.items():
+            pressure_key, generic_inlet_key, generic_outlet_key = cls._generic_branch_series_keys(
+                branch_name
+            )
+            series[legacy_branch_pressure_keys[branch_name]] = list(series[pressure_key])
+            series[legacy_inlet_key] = list(series[generic_inlet_key])
+            series[legacy_outlet_key] = list(series[generic_outlet_key])
+        return series
+
+    def simulate(
+        self,
+        config: SolveIVPConfig | None = None,
+        t_eval: list[float] | None = None,
+    ) -> Any:
+        return integrate_ode(
+            rhs=self.rhs,
+            initial_state=self.consistent_initial_state_vector(),
+            config=config or SolveIVPConfig(),
+            t_eval=t_eval,
+        )
+
+    def evaluate_solution(self, solution: Any) -> dict[str, list[float]]:
+        series = {
+            "time": [],
+            "mycylinder.p": [],
+            "mycylinder.T": [],
+            "mytank.p": [],
+            "mytank.T": [],
+        }
+        for branch_name, _, _ in self._legacy_branch_series_key_map():
+            pressure_key, inlet_key, outlet_key = self._generic_branch_series_keys(branch_name)
+            series[pressure_key] = []
+            series[inlet_key] = []
+            series[outlet_key] = []
+
+        for index, time_value in enumerate(solution.t):
+            state_vector = [row[index] for row in solution.y]
+            snapshot = self.snapshot(state_vector)
+            series["time"].append(float(time_value))
+            series["mycylinder.p"].append(snapshot.cylinder.p)
+            series["mycylinder.T"].append(snapshot.cylinder.T)
+            series["mytank.p"].append(snapshot.tank.p)
+            series["mytank.T"].append(snapshot.tank.T)
+            for branch in snapshot.branches:
+                pressure_key, generic_inlet_key, generic_outlet_key = self._generic_branch_series_keys(
+                    branch.name
+                )
+                series[pressure_key].append(branch.pipe.p)
+                series[generic_inlet_key].append(branch.inlet_flow)
+                series[generic_outlet_key].append(branch.outlet_flow)
+
+        return self._append_legacy_branch_series_aliases(series)
+
+
+def build_testmodel() -> SimulationNetwork:
+    """Compatibility helper for callers that only need the topology."""
+
+    return TestModelSystem().network

PythonModels/systems/testmodel_closure.py

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+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Callable
+
+from PythonModels.components.cylinder import Cylinder
+from PythonModels.components.orifice import Orifice
+from PythonModels.components.pipe import Pipe
+from PythonModels.components.tank import Tank
+from PythonModels.components.tee import Tee
+from PythonModels.core.medium import IdealGasMedium, ThermodynamicProperties
+from PythonModels.core.state import VolumeState
+
+
+@dataclass(frozen=True)
+class BranchInletFlowDiagnostics:
+    converged: bool
+    iterations: int
+    residual: float
+    m_flow: float
+    inlet_pressure: float
+
+
+@dataclass(frozen=True)
+class DownstreamPressureDiagnostics:
+    converged: bool
+    iterations: int
+    residual: float
+    pressure: float
+    target_total_internal_energy: float
+
+
+@dataclass(frozen=True)
+class TestModelSolveDiagnostics:
+    upper_branch_inlet: BranchInletFlowDiagnostics
+    lower_branch_inlet: BranchInletFlowDiagnostics
+    downstream_pressure_projection: DownstreamPressureDiagnostics | None
+
+
+@dataclass(frozen=True)
+class BranchClosureComponents:
+    name: str
+    orifice: Orifice
+    pipe: Pipe
+
+
+@dataclass(frozen=True)
+class BranchClosureState:
+    name: str
+    pipe: ThermodynamicProperties
+    inlet_flow: float
+    outlet_flow: float
+    inlet_h: float
+    inlet_flow_diagnostics: BranchInletFlowDiagnostics
+
+
+@dataclass(frozen=True)
+class BranchSnapshot:
+    name: str
+    pipe: ThermodynamicProperties
+    inlet_flow: float
+    outlet_flow: float
+    inlet_h: float
+    inlet_flow_diagnostics: BranchInletFlowDiagnostics
+
+
+@dataclass(frozen=True)
+class TestModelSnapshot:
+    cylinder: ThermodynamicProperties
+    tank: ThermodynamicProperties
+    tee_upstream_h: float
+    tee_downstream_h: float
+    branches: tuple[BranchSnapshot, ...] = field(default_factory=tuple)
+    solve_diagnostics: TestModelSolveDiagnostics | None = None
+
+    @property
+    def pipe_upper(self) -> ThermodynamicProperties:
+        return self.branches[0].pipe
+
+    @property
+    def pipe_lower(self) -> ThermodynamicProperties:
+        return self.branches[1].pipe
+
+    @property
+    def branch_inlet_flows(self) -> tuple[float, ...]:
+        return tuple(branch.inlet_flow for branch in self.branches)
+
+    @property
+    def branch_outlet_flows(self) -> tuple[float, ...]:
+        return tuple(branch.outlet_flow for branch in self.branches)
+
+
+@dataclass(frozen=True)
+class InitializationDiagnostics:
+    converged: bool
+    iterations: int
+    max_state_delta: float
+    max_flow_delta: float
+    max_enthalpy_delta: float
+    downstream_pressure_spread: float
+    state_vector: tuple[float, ...]
+
+
+@dataclass(frozen=True)
+class TestModelClosureComponents:
+    cylinder: Cylinder
+    upstream_tee: Tee
+    upper_branch: BranchClosureComponents
+    lower_branch: BranchClosureComponents
+    downstream_tee: Tee
+    tank: Tank
+
+    def branches(self) -> tuple[BranchClosureComponents, BranchClosureComponents]:
+        return (self.upper_branch, self.lower_branch)
+
+
+class TestModelClosure:
+    """Owns Testmodel-specific closure, projection and port-writeback logic."""
+
+    def __init__(
+        self,
+        *,
+        medium: IdealGasMedium,
+        components: TestModelClosureComponents,
+        initial_state_vector: Callable[[], list[float]],
+        apply_state_vector: Callable[[list[float]], None],
+    ) -> None:
+        self.medium = medium
+        self.components = components
+        self._initial_state_vector = initial_state_vector
+        self._apply_state_vector = apply_state_vector
+        self.last_solve_diagnostics: TestModelSolveDiagnostics | None = None
+        self.last_downstream_pressure_diagnostics: DownstreamPressureDiagnostics | None = None
+
+    @staticmethod
+    def _downstream_pressure_spread(snapshot: TestModelSnapshot) -> float:
+        downstream_pressures = tuple(branch.pipe.p for branch in snapshot.branches) + (
+            snapshot.tank.p,
+        )
+        return max(downstream_pressures) - min(downstream_pressures)
+
+    @staticmethod
+    def _initialization_flow_delta(
+        previous_snapshot: TestModelSnapshot | None,
+        current_snapshot: TestModelSnapshot,
+    ) -> float:
+        if previous_snapshot is None:
+            return max(abs(branch.outlet_flow) for branch in current_snapshot.branches)
+        return max(
+            abs(curr - prev)
+            for curr, prev in zip(
+                current_snapshot.branch_outlet_flows,
+                previous_snapshot.branch_outlet_flows,
+            )
+        )
+
+    @staticmethod
+    def _initialization_enthalpy_delta(
+        previous_snapshot: TestModelSnapshot | None,
+        current_snapshot: TestModelSnapshot,
+    ) -> float:
+        if previous_snapshot is None:
+            return abs(current_snapshot.tee_downstream_h - current_snapshot.tank.h)
+        return max(
+            abs(current_snapshot.tee_upstream_h - previous_snapshot.tee_upstream_h),
+            abs(current_snapshot.tee_downstream_h - previous_snapshot.tee_downstream_h),
+        )
+
+    def consistent_initial_state_vector(self) -> list[float]:
+        return list(self.initialize_consistent_state().state_vector)
+
+    def initialize_consistent_state(
+        self,
+        max_iterations: int = 12,
+        state_tolerance: float = 1e-9,
+        flow_tolerance: float = 1e-9,
+        enthalpy_tolerance: float = 1e-6,
+        pressure_tolerance: float = 1e-6,
+        strict_internal_solvers: bool = False,
+    ) -> InitializationDiagnostics:
+        raw_state = self._initial_state_vector()
+        previous_snapshot: TestModelSnapshot | None = None
+        diagnostics: InitializationDiagnostics | None = None
+
+        for iteration in range(1, max_iterations + 1):
+            state_before_projection = self._initial_state_vector()
+            self.snapshot(state_before_projection, strict=strict_internal_solvers)
+
+            self.project_downstream_pressure_constraints(strict=strict_internal_solvers)
+
+            state_after_projection = self._initial_state_vector()
+            snapshot_after_projection = self.snapshot(
+                state_after_projection,
+                strict=strict_internal_solvers,
+            )
+
+            max_state_delta = max(
+                abs(after - before)
+                for before, after in zip(state_before_projection, state_after_projection)
+            )
+            max_flow_delta = self._initialization_flow_delta(
+                previous_snapshot,
+                snapshot_after_projection,
+            )
+            max_enthalpy_delta = self._initialization_enthalpy_delta(
+                previous_snapshot,
+                snapshot_after_projection,
+            )
+            downstream_pressure_spread = self._downstream_pressure_spread(
+                snapshot_after_projection,
+            )
+
+            diagnostics = InitializationDiagnostics(
+                converged=(
+                    max_state_delta <= state_tolerance
+                    and max_flow_delta <= flow_tolerance
+                    and max_enthalpy_delta <= enthalpy_tolerance
+                    and downstream_pressure_spread <= pressure_tolerance
+                ),
+                iterations=iteration,
+                max_state_delta=max_state_delta,
+                max_flow_delta=max_flow_delta,
+                max_enthalpy_delta=max_enthalpy_delta,
+                downstream_pressure_spread=downstream_pressure_spread,
+                state_vector=tuple(state_after_projection),
+            )
+            previous_snapshot = snapshot_after_projection
+
+            if diagnostics.converged:
+                self._apply_state_vector(raw_state)
+                return diagnostics
+
+        assert diagnostics is not None
+        self._apply_state_vector(raw_state)
+        return diagnostics
+
+    def _solve_branch_inlet_flow(
+        self,
+        orifice: Orifice,
+        pipe: Pipe,
+        p_upstream: float,
+        pipe_props: ThermodynamicProperties,
+        *,
+        strict: bool = False,
+    ) -> tuple[float, BranchInletFlowDiagnostics]:
+        m_flow = orifice.mass_flow(p_upstream, pipe_props.p)
+        rho = max(pipe_props.rho, 1e-9)
+        p_inlet = pipe.inlet_pressure(m_flow, rho, pipe_props.p)
+        residual = abs(orifice.mass_flow(p_upstream, p_inlet) - m_flow)
+        converged = False
+        iterations = 0
+        for iteration in range(1, 9):
+            p_inlet = pipe.inlet_pressure(m_flow, rho, pipe_props.p)
+            next_m_flow = orifice.mass_flow(p_upstream, p_inlet)
+            residual = abs(next_m_flow - m_flow)
+            iterations = iteration
+            if residual <= 1e-9 * max(1.0, abs(next_m_flow)):
+                m_flow = next_m_flow
+                converged = True
+                break
+            m_flow = next_m_flow
+        diagnostics = BranchInletFlowDiagnostics(
+            converged=converged,
+            iterations=iterations,
+            residual=residual,
+            m_flow=m_flow,
+            inlet_pressure=p_inlet,
+        )
+        if strict and not diagnostics.converged:
+            raise RuntimeError(
+                f"Branch inlet flow solve did not converge for {pipe.name}: residual={residual:.6e}"
+            )
+        return m_flow, diagnostics
+
+    def _solve_downstream_branch_flows(
+        self,
+        cylinder: ThermodynamicProperties,
+        tank: ThermodynamicProperties,
+        branch_states: tuple[BranchClosureState, BranchClosureState],
+    ) -> tuple[float, float]:
+        return self._solve_downstream_branch_flows_from_state(
+            inlet_h_upper=branch_states[0].inlet_h,
+            inlet_h_lower=branch_states[1].inlet_h,
+            pipe_upper_h=max(branch_states[0].pipe.h, 1e-9),
+            pipe_lower_h=max(branch_states[1].pipe.h, 1e-9),
+            tank_h=max(tank.h, 1e-9),
+            q_in_upper=branch_states[0].inlet_flow,
+            q_in_lower=branch_states[1].inlet_flow,
+        )
+
+    def _project_volume_energy_to_pressure(
+        self,
+        component: Pipe | Tank,
+        target_pressure: float,
+    ) -> None:
+        target_temperature = target_pressure * component.V / (
+            max(component.state.m, 1e-12) * self.medium.R_gas
+        )
+        target_internal_energy = (
+            component.state.m * self.medium.specific_internal_energy(target_temperature)
+        )
+        component.state = VolumeState(m=component.state.m, U=target_internal_energy)
+
+    def _downstream_total_internal_energy_for_pressure(
+        self,
+        target_pressure: float,
+        downstream_components: tuple[Pipe | Tank, ...],
+    ) -> float:
+        total_internal_energy = 0.0
+        for component in downstream_components:
+            target_temperature = target_pressure * component.V / (
+                max(component.state.m, 1e-12) * self.medium.R_gas
+            )
+            total_internal_energy += (
+                component.state.m * self.medium.specific_internal_energy(target_temperature)
+            )
+        return total_internal_energy
+
+    def _solve_downstream_common_pressure(
+        self,
+        downstream_components: tuple[Pipe | Tank, ...],
+        target_total_internal_energy: float,
+        *,
+        strict: bool = False,
+    ) -> tuple[float, DownstreamPressureDiagnostics]:
+        lower_pressure = 1.0
+        upper_pressure = max(component.properties().p for component in downstream_components)
+        upper_pressure = max(upper_pressure, 1e5)
+
+        def residual(pressure: float) -> float:
+            return (
+                self._downstream_total_internal_energy_for_pressure(
+                    pressure,
+                    downstream_components,
+                )
+                - target_total_internal_energy
+            )
+
+        upper_residual = residual(upper_pressure)
+        iteration_count = 0
+
+        while upper_residual < 0.0:
+            upper_pressure *= 2.0
+            upper_residual = residual(upper_pressure)
+
+        final_pressure = 0.5 * (lower_pressure + upper_pressure)
+        final_residual = residual(final_pressure)
+        converged = False
+        for iteration in range(1, 81):
+            middle_pressure = 0.5 * (lower_pressure + upper_pressure)
+            middle_residual = residual(middle_pressure)
+            iteration_count = iteration
+            final_pressure = middle_pressure
+            final_residual = middle_residual
+            if abs(middle_residual) <= 1e-12 * max(1.0, target_total_internal_energy):
+                converged = True
+                break
+            if middle_residual > 0.0:
+                upper_pressure = middle_pressure
+            else:
+                lower_pressure = middle_pressure
+
+        diagnostics = DownstreamPressureDiagnostics(
+            converged=converged,
+            iterations=iteration_count,
+            residual=final_residual,
+            pressure=final_pressure,
+            target_total_internal_energy=target_total_internal_energy,
+        )
+        if strict and not diagnostics.converged:
+            raise RuntimeError(
+                "Downstream common-pressure solve did not converge: "
+                f"residual={final_residual:.6e}"
+            )
+        return final_pressure, diagnostics
+
+    def project_downstream_pressure_constraints(self, *, strict: bool = False) -> None:
+        downstream_components = (
+            self.components.upper_branch.pipe,
+            self.components.lower_branch.pipe,
+            self.components.tank,
+        )
+        total_internal_energy = sum(component.state.U for component in downstream_components)
+        common_pressure, diagnostics = self._solve_downstream_common_pressure(
+            downstream_components,
+            total_internal_energy,
+            strict=strict,
+        )
+        self.last_downstream_pressure_diagnostics = diagnostics
+
+        for component in downstream_components:
+            self._project_volume_energy_to_pressure(component, common_pressure)
+
+    def _downstream_connection_enthalpy(
+        self,
+        q_out_upper: float,
+        q_out_lower: float,
+        pipe_upper_h: float,
+        pipe_lower_h: float,
+        tank_h: float,
+    ) -> float:
+        return self.components.downstream_tee.inlet_stream_enthalpy(
+            q_out_lower,
+            pipe_lower_h,
+            q_out_upper,
+            pipe_upper_h,
+            fallback_h=tank_h,
+        )
+
+    def _solve_downstream_branch_flows_from_state(
+        self,
+        *,
+        inlet_h_upper: float,
+        inlet_h_lower: float,
+        pipe_upper_h: float,
+        pipe_lower_h: float,
+        tank_h: float,
+        q_in_upper: float,
+        q_in_lower: float,
+    ) -> tuple[float, float]:
+        return self.components.downstream_tee.solve_branch_outlet_flows_from_energy_balance(
+            ratio_branch1=self.components.upper_branch.pipe.V / self.components.tank.V,
+            ratio_branch2=self.components.lower_branch.pipe.V / self.components.tank.V,
+            inlet_h_branch1=inlet_h_upper,
+            inlet_h_branch2=inlet_h_lower,
+            branch1_h=pipe_upper_h,
+            branch2_h=pipe_lower_h,
+            inlet_h=tank_h,
+            q_in_branch1=q_in_upper,
+            q_in_branch2=q_in_lower,
+        )
+
+    def _evaluate_branch_states(
+        self,
+        cylinder: ThermodynamicProperties,
+    ) -> tuple[BranchClosureState, BranchClosureState]:
+        states: list[BranchClosureState] = []
+        for branch in self.components.branches():
+            pipe_properties = branch.pipe.properties()
+            inlet_flow, inlet_flow_diagnostics = self._solve_branch_inlet_flow(
+                branch.orifice,
+                branch.pipe,
+                cylinder.p,
+                pipe_properties,
+            )
+            inlet_h = branch.pipe.port_a_inlet_enthalpy(
+                port_a_m_flow=inlet_flow,
+                connected_h=cylinder.h,
+                internal_h=pipe_properties.h,
+            )
+            states.append(
+                BranchClosureState(
+                    name=branch.name,
+                    pipe=pipe_properties,
+                    inlet_flow=inlet_flow,
+                    outlet_flow=0.0,
+                    inlet_h=inlet_h,
+                    inlet_flow_diagnostics=inlet_flow_diagnostics,
+                )
+            )
+        return (states[0], states[1])
+
+    @staticmethod
+    def _with_branch_outlet_flows(
+        branch_states: tuple[BranchClosureState, BranchClosureState],
+        outlet_flows: tuple[float, float],
+    ) -> tuple[BranchClosureState, BranchClosureState]:
+        return (
+            BranchClosureState(
+                name=branch_states[0].name,
+                pipe=branch_states[0].pipe,
+                inlet_flow=branch_states[0].inlet_flow,
+                outlet_flow=outlet_flows[0],
+                inlet_h=branch_states[0].inlet_h,
+                inlet_flow_diagnostics=branch_states[0].inlet_flow_diagnostics,
+            ),
+            BranchClosureState(
+                name=branch_states[1].name,
+                pipe=branch_states[1].pipe,
+                inlet_flow=branch_states[1].inlet_flow,
+                outlet_flow=outlet_flows[1],
+                inlet_h=branch_states[1].inlet_h,
+                inlet_flow_diagnostics=branch_states[1].inlet_flow_diagnostics,
+            ),
+        )
+
+    @staticmethod
+    def _branch_snapshots(
+        branch_states: tuple[BranchClosureState, BranchClosureState],
+    ) -> tuple[BranchSnapshot, BranchSnapshot]:
+        return (
+            BranchSnapshot(
+                name=branch_states[0].name,
+                pipe=branch_states[0].pipe,
+                inlet_flow=branch_states[0].inlet_flow,
+                outlet_flow=branch_states[0].outlet_flow,
+                inlet_h=branch_states[0].inlet_h,
+                inlet_flow_diagnostics=branch_states[0].inlet_flow_diagnostics,
+            ),
+            BranchSnapshot(
+                name=branch_states[1].name,
+                pipe=branch_states[1].pipe,
+                inlet_flow=branch_states[1].inlet_flow,
+                outlet_flow=branch_states[1].outlet_flow,
+                inlet_h=branch_states[1].inlet_h,
+                inlet_flow_diagnostics=branch_states[1].inlet_flow_diagnostics,
+            ),
+        )
+
+    def snapshot(
+        self,
+        state_vector: list[float] | None = None,
+        *,
+        strict: bool = False,
+    ) -> TestModelSnapshot:
+        if state_vector is not None:
+            self._apply_state_vector(list(state_vector))
+
+        cylinder = self.components.cylinder.properties()
+        tank = self.components.tank.properties()
+        branch_states = self._evaluate_branch_states(cylinder)
+        if strict:
+            for branch_state in branch_states:
+                if not branch_state.inlet_flow_diagnostics.converged:
+                    raise RuntimeError(
+                        "Branch inlet flow solve did not converge for "
+                        f"{branch_state.name}: residual="
+                        f"{branch_state.inlet_flow_diagnostics.residual:.6e}"
+                    )
+        outlet_flows = self._solve_downstream_branch_flows(cylinder, tank, branch_states)
+        branch_states = self._with_branch_outlet_flows(branch_states, outlet_flows)
+
+        tee_upstream_h = self.components.upstream_tee.inlet_stream_enthalpy(
+            -branch_states[0].inlet_flow,
+            branch_states[0].pipe.h,
+            -branch_states[1].inlet_flow,
+            branch_states[1].pipe.h,
+            fallback_h=cylinder.h,
+        )
+        tee_downstream_h = self._downstream_connection_enthalpy(
+            branch_states[0].outlet_flow,
+            branch_states[1].outlet_flow,
+            branch_states[0].pipe.h,
+            branch_states[1].pipe.h,
+            tank.h,
+        )
+
+        self._write_port_states(
+            cylinder,
+            tank,
+            branch_states,
+            tee_upstream_h,
+            tee_downstream_h,
+        )
+
+        solve_diagnostics = TestModelSolveDiagnostics(
+            upper_branch_inlet=branch_states[0].inlet_flow_diagnostics,
+            lower_branch_inlet=branch_states[1].inlet_flow_diagnostics,
+            downstream_pressure_projection=self.last_downstream_pressure_diagnostics,
+        )
+        self.last_solve_diagnostics = solve_diagnostics
+        branch_snapshots = self._branch_snapshots(branch_states)
+
+        return TestModelSnapshot(
+            cylinder=cylinder,
+            tank=tank,
+            tee_upstream_h=tee_upstream_h,
+            tee_downstream_h=tee_downstream_h,
+            branches=branch_snapshots,
+            solve_diagnostics=solve_diagnostics,
+        )
+
+    def _write_port_states(
+        self,
+        cylinder: ThermodynamicProperties,
+        tank: ThermodynamicProperties,
+        branch_states: tuple[BranchClosureState, BranchClosureState],
+        tee_upstream_h: float,
+        tee_downstream_h: float,
+    ) -> None:
+        cylinder_m_flow = -sum(branch_state.inlet_flow for branch_state in branch_states)
+        tank_m_flow = sum(branch_state.outlet_flow for branch_state in branch_states)
+
+        self.components.cylinder.port_b.m_flow = cylinder_m_flow
+
+        self.components.upstream_tee.port_in.p = cylinder.p
+        self.components.upstream_tee.port_out1.p = cylinder.p
+        self.components.upstream_tee.port_out2.p = cylinder.p
+        self.components.upstream_tee.port_in.m_flow = cylinder_m_flow
+        self.components.upstream_tee.port_in.h_outflow = tee_upstream_h
+        self.components.upstream_tee.port_out1.h_outflow = cylinder.h
+        self.components.upstream_tee.port_out2.h_outflow = cylinder.h
+        self.components.upstream_tee.port_out1.m_flow = -branch_states[0].inlet_flow
+        self.components.upstream_tee.port_out2.m_flow = -branch_states[1].inlet_flow
+
+        for branch_components, branch_state in zip(self.components.branches(), branch_states):
+            branch_components.orifice.port_a.p = cylinder.p
+            branch_components.orifice.port_b.p = branch_components.pipe.inlet_pressure(
+                branch_state.inlet_flow,
+                max(branch_state.pipe.rho, 1e-9),
+                branch_state.pipe.p,
+            )
+            branch_components.orifice.port_a.m_flow = branch_state.inlet_flow
+            branch_components.orifice.port_b.m_flow = -branch_state.inlet_flow
+            branch_components.orifice.port_a.h_outflow = cylinder.h
+            branch_components.orifice.port_b.h_outflow = branch_state.pipe.h
+
+            branch_components.pipe.port_a.p = branch_components.orifice.port_b.p
+            branch_components.pipe.port_a.m_flow = branch_state.inlet_flow
+            branch_components.pipe.port_b.m_flow = -branch_state.outlet_flow
+            branch_components.pipe.port_b.p = branch_state.pipe.p
+
+        self.components.downstream_tee.port_in.p = tank.p
+        self.components.downstream_tee.port_out1.p = tank.p
+        self.components.downstream_tee.port_out2.p = tank.p
+        self.components.downstream_tee.port_in.m_flow = -tank_m_flow
+        self.components.downstream_tee.port_out1.m_flow = branch_states[1].outlet_flow
+        self.components.downstream_tee.port_out2.m_flow = branch_states[0].outlet_flow
+        self.components.downstream_tee.port_in.h_outflow = tee_downstream_h
+        self.components.downstream_tee.port_out1.h_outflow = tank.h
+        self.components.downstream_tee.port_out2.h_outflow = tank.h
+
+        self.components.tank.port_a.m_flow = tank_m_flow
+
+    def _branch_derivative_states(
+        self,
+        snapshot: TestModelSnapshot,
+    ) -> tuple[VolumeState, VolumeState]:
+        derivative_states: list[VolumeState] = []
+        for branch_components, branch_snapshot in zip(self.components.branches(), snapshot.branches):
+            derivative_states.append(
+                branch_components.pipe.derivatives_from_connections(
+                    port_a_m_flow=branch_snapshot.inlet_flow,
+                    connected_h_a=snapshot.cylinder.h,
+                    port_b_m_flow=-branch_snapshot.outlet_flow,
+                    connected_h_b=snapshot.tank.h,
+                    internal_h=branch_snapshot.pipe.h,
+                )
+            )
+        return (derivative_states[0], derivative_states[1])
+
+    def rhs(self, state_vector: list[float]) -> list[float]:
+        snapshot = self.snapshot(state_vector)
+
+        cylinder_m_flow = -sum(branch.inlet_flow for branch in snapshot.branches)
+        tank_m_flow = sum(branch.outlet_flow for branch in snapshot.branches)
+        d_cylinder = self.components.cylinder.derivatives_from_connection(
+            connected_h=snapshot.tee_upstream_h,
+            port_m_flow=cylinder_m_flow,
+            internal_h=snapshot.cylinder.h,
+        )
+        branch_derivatives = self._branch_derivative_states(snapshot)
+        d_tank = self.components.tank.derivatives_from_connection(
+            connected_h=snapshot.tee_downstream_h,
+            port_m_flow=tank_m_flow,
+            internal_h=snapshot.tank.h,
+        )
+
+        return [
+            d_cylinder.m,
+            d_cylinder.U,
+            branch_derivatives[0].m,
+            branch_derivatives[0].U,
+            branch_derivatives[1].m,
+            branch_derivatives[1].U,
+            d_tank.m,
+            d_tank.U,
+        ]