pairForce.h

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/*
 * -------------------------------------------
 * Copyright (c) 2021 - 2026 Prashant K. Jha
 * -------------------------------------------
 * PeriDEM https://github.com/prashjha/PeriDEM
 *
 * Distributed under the Boost Software License, Version 1.0. (See accompanying
 * file LICENSE)
 */
 
#ifndef CONTACT_PAIRFORCE_H
#define CONTACT_PAIRFORCE_H
 
#include "util/point.h"
#include <cstddef>
#include <cstdint>
#include <mutex>
#include <unordered_map>
 
namespace inp {
struct ContactPairDeck;
}
 
namespace contact {
 
struct Pair {
  const inp::ContactPairDeck &deck;
  util::Point yi, yj, vi, vj;
  std::size_t i = 0;
  std::size_t j = 0;
  std::size_t pt_i = 0;
  std::size_t pt_j = 0;
  double voli = 0.;
  double volj = 0.;
  double rhoi = 0.;
  double rhoj = 0.;
  double dt = 0.;
  bool wall_i = false;
  bool wall_j = false;
};
 
double correctedContactVolume(double volj, double Rji, double Rc, double h);
 
class PairForce {
public:
  virtual ~PairForce() = default;
 
  virtual void beginStep() {}
  virtual void endStep() {}
 
  virtual util::Point springForce(const Pair &p);
 
  virtual util::Point nodeDampingForce(const Pair &p);
 
  virtual util::Point force(const Pair &p);
};
 
class StickSlipPairForce : public PairForce {
public:
  void beginStep() override;
  void endStep() override;
  util::Point springForce(const Pair &p) override;
 
private:
  struct Hist {
    util::Point delta_t;
    std::size_t stamp = 0;
  };
  static std::uint64_t key(std::size_t i, std::size_t j) {
    return (static_cast<std::uint64_t>(i) << 32) ^
           static_cast<std::uint64_t>(j);
  }
  std::unordered_map<std::uint64_t, Hist> d_hist;
  std::size_t d_stamp = 0;
  std::mutex d_mutex;
};
 
} // namespace contact
 
#endif // CONTACT_PAIRFORCE_H