上传PythonModels文件

PythonModels/core/medium.py

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+from __future__ import annotations
+
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class ThermodynamicProperties:
+    p: float
+    T: float
+    rho: float
+    u: float
+    h: float
+
+
+@dataclass(frozen=True)
+class IdealGasMedium:
+    """Temperature-dependent ideal-gas air approximation.
+
+    This is still not a strict clone of `Modelica.Media.Air.SimpleAir`.
+    The small linear `cp(T)` term is kept configurable for calibration, but the
+    current default is calibrated against the committed Testmodel baseline and
+    therefore falls back to the constant-heat-capacity limit.
+    """
+
+    name: str = "SimpleAirApprox"
+    R_gas: float = 287.0
+    cp_ref: float = 1005.0
+    T_ref: float = 300.0
+    cp_slope: float = 0.0
+
+    @property
+    def cv(self) -> float:
+        return self.cv_at_temperature(self.T_ref)
+
+    @property
+    def gamma(self) -> float:
+        return self.cp_at_temperature(self.T_ref) / self.cv
+
+    def cp_at_temperature(self, T: float) -> float:
+        return self.cp_ref + self.cp_slope * (T - self.T_ref)
+
+    def cv_at_temperature(self, T: float) -> float:
+        return self.cp_at_temperature(T) - self.R_gas
+
+    def density(self, p: float, T: float) -> float:
+        return p / (self.R_gas * T)
+
+    def specific_internal_energy(self, T: float) -> float:
+        delta_T = T - self.T_ref
+        return (
+            self.cv * self.T_ref
+            + self.cv * delta_T
+            + 0.5 * self.cp_slope * delta_T * delta_T
+        )
+
+    def specific_enthalpy(self, T: float) -> float:
+        delta_T = T - self.T_ref
+        return (
+            self.cp_ref * self.T_ref
+            + self.cp_ref * delta_T
+            + 0.5 * self.cp_slope * delta_T * delta_T
+        )
+
+    def temperature_from_internal_energy(self, u: float) -> float:
+        reference_internal_energy = self.cv * self.T_ref
+        delta_u = u - reference_internal_energy
+
+        if abs(self.cp_slope) <= 1e-15:
+            return self.T_ref + delta_u / self.cv
+
+        a = 0.5 * self.cp_slope
+        b = self.cv
+        c = -delta_u
+        discriminant = max(b * b - 4.0 * a * c, 0.0)
+        positive_root = (-b + discriminant**0.5) / (2.0 * a)
+        negative_root = (-b - discriminant**0.5) / (2.0 * a)
+        delta_T = positive_root if abs(positive_root) <= abs(negative_root) else negative_root
+        return self.T_ref + delta_T
+
+    def temperature_from_mass_internal_energy(self, m: float, U: float) -> float:
+        if m <= 0.0:
+            raise ValueError("Mass must stay positive when recovering temperature.")
+        return self.temperature_from_internal_energy(U / m)
+
+    def pressure(self, m: float, T: float, V: float) -> float:
+        if V <= 0.0:
+            raise ValueError("Volume must stay positive.")
+        return m * self.R_gas * T / V
+
+    def properties_from_mU(self, m: float, U: float, V: float) -> ThermodynamicProperties:
+        T = self.temperature_from_mass_internal_energy(m, U)
+        p = self.pressure(m, T, V)
+        rho = m / V
+        u = U / m
+        h = self.specific_enthalpy(T)
+        return ThermodynamicProperties(p=p, T=T, rho=rho, u=u, h=h)