WindkesselBC.h

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// SPDX-FileCopyrightText: Copyright (c) Stanford University, The Regents of the
// University of California, and others. SPDX-License-Identifier: BSD-3-Clause
/**
 * @file WindkesselBC.h
 * @brief model::WindkesselBC source file
 */
#ifndef SVZERODSOLVER_MODEL_WINDKESSELBC_HPP_
#define SVZERODSOLVER_MODEL_WINDKESSELBC_HPP_
 
#include "Block.h"
#include "SparseSystem.h"
 
/**
 * @brief Windkessel RCR boundary condition.
 *
 * Models the mechanical behavior of a Windkessel boundary condition.
 *
 * \f[
 * \begin{circuitikz} \draw
 * node[left] {$Q_{in}$} [-latex] (0,0) -- (0.8,0);
 * \draw (1,0) node[anchor=south]{$P_{in}$}
 * to [R, l=$R_p$, *-] (3,0)
 * node[anchor=south]{$P_{c}$}
 * to [R, l=$R_d$, *-*] (5,0)
 * node[anchor=south]{$P_{ref}$}
 * (3,0) to [C, l=$C$, *-] (3,-1.5)
 * node[ground]{};
 * \end{circuitikz}
 * \f]
 *
 * ### Governing equations
 *
 * \f[
 * R_{d} Q_{in}-P_{c}+P_{r e f}-R_{d} C \frac{d P_{c}}{d t}=0
 * \f]
 *
 * \f[
 * P_{in}-P_{c}-R_{p} Q_{in}=0
 * \f]
 *
 * ### Local contributions
 *
 * \f[
 * \mathbf{y}^{e}=\left[\begin{array}{lll}P^{e} & Q^{e} &
 * P_{c}^{e}\end{array}\right]^{T} \f]
 *
 * \f[
 * \mathbf{E}^{e}=\left[\begin{array}{ccc}
 * 0 & 0 & -R_{d} C \\
 * 0 & 0 & 0
 * \end{array}\right]
 * \f]
 *
 * \f[
 * \mathbf{F}^{e}=\left[\begin{array}{ccc}
 * 0 & R_{d} & -1 \\
 * 1 & -R_{p} & -1
 * \end{array}\right]
 * \f]
 *
 * \f[
 * \mathbf{c}^{e}=\left[\begin{array}{c}
 * P_{r e f} \\
 * 0
 * \end{array}\right]
 * \f]
 *
 * See \cite vignon04.
 *
 * ### Parameters
 *
 * Parameter sequence for constructing this block
 *
 * * `0` Proximal resistance
 * * `1` Capacitance
 * * `2` Distal resistance
 * * `3` Distal pressure
 *
 * ### Usage in json configuration file
 *
 *     "boundary_conditions": [
 *         {
 *             "bc_name": "OUT",
 *             "bc_type": "RCR",
 *             "bc_values": {
 *                 "C": 0.0001,
 *                 "Pd": 0.0,
 *                 "Rd": 1000.0,
 *                 "Rp": 1000.0
 *             }
 *         }
 *     ]
 *
 * ### Internal variables
 *
 * Names of internal variables in this block's output:
 *
 * * `pressure_c`: Pressure at the capacitor
 *
 */
class WindkesselBC : public Block {
 public:
  /**
   * @brief Construct a new WindkesselBC object
   *
   * @param id Global ID of the block
   * @param model The model to which the block belongs
   */
  WindkesselBC(int id, Model* model)
      : Block(id, model, BlockType::windkessel_bc,
              BlockClass::boundary_condition,
              {{"Rp", InputParameter()},
               {"C", InputParameter()},
               {"Rd", InputParameter()},
               {"Pd", InputParameter(true)}}) {}
 
  /**
   * @brief Set up the degrees of freedom (DOF) of the block
   *
   * Set \ref global_var_ids and \ref global_eqn_ids of the element based on the
   * number of equations and the number of internal variables of the
   * element.
   *
   * @param dofhandler Degree-of-freedom handler to register variables and
   * equations at
   */
  void setup_dofs(DOFHandler& dofhandler);
 
  /**
   * @brief Update the constant contributions of the element in a sparse
   system
   *
   * @param system System to update contributions at
   * @param parameters Parameters of the model
   */
  void update_constant(SparseSystem& system, std::vector<double>& parameters);
 
  /**
   * @brief Update the time-dependent contributions of the element in a sparse
   * system
   *
   * @param system System to update contributions at
   * @param parameters Parameters of the model
   */
  void update_time(SparseSystem& system, std::vector<double>& parameters);
 
  /**
   * @brief Number of triplets of element
   *
   * Number of triplets that the element contributes to the global system
   * (relevant for sparse memory reservation)
   */
  TripletsContributions num_triplets{5, 1, 0};
};
 
#endif  // SVZERODSOLVER_MODEL_WINDKESSELBC_HPP_