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Update 3-temperatures solver scheme for transient_temperature method #173

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Update 3-temperatures solver scheme for transient_temperature method #173

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eea9c89
Changed solv3 transient temperature method to match the last evolutio…
Jul 23, 2026
2a65f27
typo corrections and formatting
ecieren Jul 23, 2026
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38 changes: 33 additions & 5 deletions src/thermohl/solver/slv3t.py
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Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ def _infer_target_from_cable_type(
class Solver3T(Solver_):
def __init__(
self,
dic: Optional[dict[str, Any]] = None,
dic: Optional[Dict[str, Any]] = None,
joule: Type[PowerTerm] = PowerTerm,
solar: Type[PowerTerm] = PowerTerm,
convective: Type[PowerTerm] = PowerTerm,
Expand Down Expand Up @@ -256,6 +256,24 @@ def balance_3t(
- self.precipitation_cooling.value(surface_temperature)
)

def tau(
self,
surface_temperature: floatArray,
core_temperature: floatArray,
time_step: float = 1.0e-05,
) -> floatArrayLike:
"""Estimation of a time-constant by linearization of the EDO."""
return (
-(self.args.linear_mass * self.args.heat_capacity)
/ (
self.balance_3t(surface_temperature + time_step, core_temperature)
- self.balance_3t(surface_temperature - time_step, core_temperature)
+ self.balance_3t(surface_temperature, core_temperature + time_step)
- self.balance_3t(surface_temperature, core_temperature - time_step)
)
* (2 * time_step)
)

def morgan_3t(
self,
surface_temperature: floatArray,
Expand Down Expand Up @@ -493,20 +511,30 @@ def transient_temperature(
surface_temperature[0, :], core_temperature[0, :]
)

# state variables for the continuity-preserving integration scheme
# the solve operation is actually performed on this variables, which have the dimension
# of a temperature but no physical meaning of interest, hence the generic names
tx = core_temperature[0, :] - surface_temperature[0, :]
ty = c2 * surface_temperature[0, :] + (1 - c2) * core_temperature[0, :]

# main time loop
for i in range(1, len(offset)):
for k in time_changing_parameters.keys():
self.args[k] = time_changing_parameters[k][i, :]
self.update()
time_step = offset[i] - offset[i - 1]
bal = self.balance_3t(
surface_temperature[i - 1, :], core_temperature[i - 1, :]
)
tau = self.tau(surface_temperature[i - 1, :], core_temperature[i - 1, :])
average_temperature[i, :] = (
average_temperature[i - 1, :] + (offset[i] - offset[i - 1]) * bal * imc
average_temperature[i - 1, :] + time_step * bal * imc
)
mrg = c1 * (self.joule_heating.value(average_temperature[i, :]) - bal)
core_temperature[i, :] = average_temperature[i, :] + c2 * mrg
surface_temperature[i, :] = core_temperature[i, :] - mrg
morgan = c1 * (self.joule_heating.value(average_temperature[i, :]) - bal)
tx = tx + time_step * (-tx + morgan) / (tau * 0.3)
ty = ty + time_step * (-ty + average_temperature[i - 1, :]) / (tau * 0.02)
core_temperature[i, :] = c2 * tx + ty
surface_temperature[i, :] = ty - (1 - c2) * tx

result = self._transient_temperature_results(
offset,
Expand Down
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