Thermal Solution Parameters dialog box — Thermal

Steady State Convergence Control
Convergence Criteria	Specifies how the convergence criteria for the steady state thermal solve is defined.AutomaticSets default values for the maximum temperature change of any element between two consecutive iterations. The default values depend on the analysis type.SpecifySets the maximum temperature change to the value you specify in the Maximum Temperature Change box. When the temperature change of all elements between two consecutive iterations is below the specified value, the steady state solution is converged.
Heat Imbalance	Appears when Convergence Criteria is set to Specify.Adds the heat imbalance convergence criterion to the maximum temperature change criterion.
Heat Imbalance Option	Appears when Heat Imbalance is selected.Specifies how the heat imbalance convergence criterion is calculated. The heat imbalance is the difference between the heat applied to the model and the heat flow into the sinks. When this heat imbalance reaches a value below the specified limit, the steady state solution is converged.Global FractionSets the fraction of the heat imbalance that is the limit for the heat imbalance criterion, to the value that you specify in the Global Fraction box.AbsoluteSets the value for the heat imbalance that is the limit for the heat imbalance criterion, to the value that you specify in the Absolute box.
Iteration Limit	Sets the value for the maximum number of iterations the thermal solver performs without converging.
Transient Convergence Control
Maximum Temperature Change	Sets the value for the maximum temperature change of any element between two consecutive iterations at each time step. When the temperature change of all elements between two consecutive iterations is below the specified value, the transient solution goes to the next time step.
Iteration Limit	Sets the value for the maximum number of iterations the thermal solver performs for a given time step without converging.
Transient Time Integration Control
Available only in the Multiphysics environment.
Integration Method	Specifies how the solution is advanced in time.Implicit solution method is the implicit difference scheme.Semi–Implicit solution method is the Crank-Nicholson method.Explicit solution method is a fully explicit integration scheme.Exponential Explicit solution method is an explicit scheme where the element temperature profile over an integration time step is assumed to be an exponential decay.Fully Implicit solution method is the fully implicit difference scheme where the thermal solver treats all non-linear terms implicitly.See Card 2b — Analyzer Control Card in the Simcenter 3D Thermal Solver Reference Manual for more information.
Thermal Solver
Relaxation Factor	Sets the relaxation factor that controls the stability of the thermal solver when calculating new temperatures at each iteration based on element heat imbalance.
Convergence Trace	Outputs the model convergence parameters for the thermal solver at every iteration, to the solver log file.
Duct Flow Solver
Pressure Convergence Criterion	Sets the value for the pressure convergence of the duct flow network equations.
Iteration Limit	Sets the value for the maximum number of duct flow iterations the thermal solver performs for a given time step, without converging.
Relaxation Factor	Sets the relaxation factor that controls the stability of the duct flow network equations.
Convergence Trace	Outputs the model convergence parameters for the duct flow network at every iteration, to the solver log file.
Element Properties
Element Discretization	Specifies the method for discretization of beam, shell, and solid elements when calculating element conductances.Element Center MethodCreates conductances between element centers.Element CG MethodCreates conductances between boundary elements and between the element CG and its boundary elements. The software creates boundary elements on 3D solid element surfaces, 2D planar element edges, and 1D element ends.Finite Element MethodActivates the finite element formulation. For other element discretization methods, the thermal solver uses the finite volume formulation.Note: The thermal solver using the finite element method does not support phase change, multilayer shells, protective layers, immersed ducts, and parallel processing.
Shell Accuracy	Appears when Element Discretization is set to Element CG Method.Specifies how the conductance matrix is calculated for quadrilateral elements.First OrderCalculates the conductance matrix directly.Second OrderDivides each quadrilateral element into four triangles before calculating the conductance matrix.
Solid Element Capacitance Distribution	Appears when Element Discretization is set to Element CG Method.Specifies the redistribution of capacitances and heat loads for shell and solid elements.At CGsLumps the capacitance and elemental heat load at the center of gravity (CG) not at the boundary elements, and creates conductances from the CG to boundary elements.At Boundary ElementsRedistributes capacitances and heat loads from the CG to the boundary elements, and eliminates the conductances from the CG to the boundary elements.
Element Convention for Temperature Constraint	Appears when Element Discretization is set to Element CG Method.Specifies how the temperature is fixed for elements for which a Temperature constraint is defined.Constrain Temperature at CG onlyFixes the temperature at the center of gravity of each element of the Temperature constraint.Constrain Temperature at CG and Boundary ElementsFixes the temperature at the center of gravity and at boundary elements of each element of the Temperature constraint.
Duct Thermal Discretization	Specifies how heat is transported in a duct flow network.Advection and No ConductionTransports heat by advection only, and models each element with a constant temperature profile.Advection and ConductionTransports heat by advection and conduction, and models each element with a constant temperature profile.Exponential AdvectionTransports heat by advection and conduction, and models each element with an exponential temperature profile along the element length.
Conjugate Gradient Solver
Convergence Norm	Specifies the type of norm that is used to calculate the convergence residuals for temperatures during the linear solve.MAXUses the maximum norm convergence criterion,
Convergence Criterion	Sets the value for the convergence of the conjugate gradient solver.
Iteration Limit	Sets the value for the maximum number of iterations for one loop of the conjugate gradient solver.
Preconditioner Matrix Fill Value	Sets the value for the maximum number of additional terms in each row of the preconditioning matrix. If the conjugate gradient solver reaches its iteration limit without converging, the software does the following:Automatically increases the fill value by the value that you specify in the Preconditioner Matrix Fill Value box.Recreates the preconditioning matrix.Repeats the solution process until convergence is achieved.
Thermal Coupling
Elements Part of a Thermal Coupling Do Not Convect to Environment	Excludes the thermal coupling elements from the convection to environment, when you define a thermal coupling and a convection to environment boundary condition on the same selection.

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Thermal Solution Parameters dialog box — Thermal, Simcenter 3D 2021.1 Series

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