Problem Setup

Types for defining boundary conditions and problem configuration.

Boundary Condition Types

Sentinel.BCType Type

BCType

Enumeration of boundary condition types.

• BC_NONE = 0: no boundary condition (free DOF)

• BC_DIRICHLET = 1: prescribed displacement/pressure value

• BC_NEUMANN = 2: prescribed flux/traction (used for poroelastic pressure flow)

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Sentinel.SingleCondition Type

SingleCondition

Boundary condition at a single DOF. Corresponds to the Fortran singlecondition type.

Fields

• bctype: type of boundary condition (BCType enum)

• node: associated mesh node index (1-based)

• value: complex prescribed value (displacement or pressure)

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Sentinel.BoundaryConditions Type

BoundaryConditions

Complete set of boundary conditions for the FEM problem. Corresponds to the Fortran bndrycond type.

Fields

• dof: total number of DOFs

• numbcsets: number of boundary condition sets (= number of displacement sets)

• numdirchlt: number of Dirichlet (type-1) boundary conditions

• bc: (dof, numbcsets) array of SingleCondition

• bcind: (dof, numbcsets) logical indicator — true if a BC is applied here

Notes

For a 3D mesh with nn nodes:

• Displacement DOFs: index 3*i-2, 3*i-1, 3*i for node i

• Poroelastic pressure DOFs: index 3*nn + i for node i

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Boundary Condition Operations

Sentinel.init_bcs! Function

init_bcs!(bcs::BoundaryConditions, dof::Int, numbcsets::Int)

Allocate boundary condition arrays for the given DOF count and number of sets.

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Sentinel.clear_bcs! Function

clear_bcs!(bcs::BoundaryConditions)

Reset all boundary condition indicators to false (free DOFs).

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Problem Definition

Sentinel.Problem Type

Problem

Complete specification of a Sentinel forward/inverse MRE problem.

Fields

• model: material model integer (1–7)

• numfreq: number of frequencies

• freq: frequency array [Hz], length numfreq

• avgfreq: average frequency [Hz] used for reconstruction normalization

• numdispsets: number of displacement sets (typically = numfreq × num_excitations)

• problemtype: 0 = forward only, >0 = inverse

• forwardtype: 0 = simulation (properties from material type table), 1 = inverse evaluation (properties from property files)

• maxglobiter: maximum global outer iterations

• maxzoneiter: maximum zone-level iterations

• maxlineiter: maximum line-search iterations

• minepsglob, minepszone, minepsline: convergence tolerances

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