15.2 Functions of the implementation

Table 15.1 lists the main functions of the explicit and implicit compressible flow solver. The discretization of the advection term mainly uses the AdvectVolumeFlux and AdvectTraceFlux to calculate the fluxes on the quadrature points of inside the element and on the element boundaries. Then, IProductWRTDerivBase and AddTraceIntegral are adopted to perform the integrations. Similarly, in the diffusion discretization, DiffuseVolumeFlux and DiffuseTraceFlux are implemented for calculating the fluxes, while IProductWRTDerivBase and AddTraceIntegral are for the integrations. For the diffusion term, spatial derivatives are needed and calculated using DiffuseCalcDerivative. For the interior penalty method an extra symmetric term may be needed and calculated by AddDiffusionSymmFluxToCoeff. The above functions forms the spatial operator of DoOdeRhs and the explicit solver in relatively complete coupled with a explicit time integration scheme. For the implicit solver, extra functions are needed. The DoImplicitSolve solves the nonlinear system, in which the NonlinSysEvaluatorCoeff1D evaluates the nonlinear system residual, MatrixMultiplyMatrixFreeCoeff calculates the Jacobian matrix vector inner product and PreconCoeff perform the preconditioning. Provided a specific implicit time integration scheme, the DoImplicitSolve helps solve the nonlinear system for implicit stages and the implicit solver is complete.

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Table 15.1 Table of variable and function mapping used in the compressible flow solver to their mathematical operations

Variable/Function name	Physical meaning
AdvectVolumeFlux	Advection Euler flux: Fi
AdvectTraceFlux	Advection (Riemann) numerical flux at trace: i
IProductWRTDerivBase	∑ j=1dBT DjT Λ operator to a vector
AddTraceIntegral	T Λ to a vector
MultiplyByElmImvMass	Multiply the inverse of mass matrix to a vector
DiffuseCalcDerivative	Calculate the derivatives of a vector
DiffuseVolumeFlux	Analytical Diffusion flux: G i
DiffuseTraceFlux	Calculate the diffusion numerical flux
AddDiffusionSymmFluxToCoeff	Add the integral of symmetric flux (special for IP)
DoOdeRhs	Calculate Lδ
DoImplicitSolve	Solve the nonlinear system in implicit time integrations
NonlinSysEvaluatorCoeff1D	Calculate N(uδ(i))
MatrixMultiplyMatrixFreeCoeff	Calculate ∂N∕∂u ⋅q
PreconCoeff	Perform preconditioning

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