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More rheo pressure EOS, allow variable cs

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This commit is contained in:
jtclemm
2024-11-01 17:04:32 -06:00
parent f483a90d8a
commit c1ac0cea1d
7 changed files with 103 additions and 19 deletions
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25
doc/src/fix_rheo_pressure.rst
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@ -19,8 +19,10 @@ Syntax
.. parsed-literal::
*linear* args = none
*taitwater* args = none
*tait/water* args = none
*tait/general* args = exponent :math:`gamma` (unitless) and background pressure :math:`P[b]` (pressure)
*cubic* args = cubic prefactor :math:`A_3` (pressure/density\^2)
*ideal/gas* args = heat capacity ratio :math:`gamma` (unitless)
Examples
""""""""
@ -65,12 +67,31 @@ is a cubic equation of state which has an extra argument :math:`A_3`,
P = c ((\rho - \rho_0) + A_3 (\rho - \rho_0)^3) .
Style *taitwater* is Tait's equation of state:
Style *tait/water* is Tait's equation of state:
.. math::
P = \frac{c^2 \rho_0}{7} \biggl[\left(\frac{\rho}{\rho_0}\right)^{7} - 1\biggr].
Style *tait/general* generalizes this equation of state
.. math::
P = \frac{c^2 \rho_0}{\gamma} \biggl[\left(\frac{\rho}{\rho_0}\right)^{\gamma} - 1\biggr] + P[b].
where :math:`\gamma` is an exponent and :math:`P[b]` is a constant background pressure.
Style *ideal/gas* is the ideal gas equation of state
.. math::
P = (\gamma - 1) \rho e
where :math:`\gamma` is the heat capacity ratio and :math:`e` is the internal energy of
a particle per unit mass. This style is only compatible with atom style rheo/thermal.
Note that when using this style, the speed of sound is no longer constant such that the
value of :math:`c` specified in :doc:`fix rheo <fix_rheo>` is not used.
Restart, fix_modify, output, run start/stop, minimize info
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

9
src/RHEO/compute_rheo_interface.cpp
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@ -97,6 +97,9 @@ void ComputeRHEOInterface::init()
auto fixes = modify->get_fix_by_style("rheo/pressure");
fix_pressure = dynamic_cast<FixRHEOPressure *>(fixes[0]);
if (!fix_pressure->invertable_pressure)
error->all(FLERR, "RHEO interface reconstruction incompatible with pressure equation of state");
neighbor->add_request(this, NeighConst::REQ_DEFAULT);
}
@ -178,7 +181,7 @@ void ComputeRHEOInterface::compute_peratom()
dot = 0;
for (a = 0; a < 3; a++) dot += (-fp_store[j][a] + fp_store[i][a]) * dx[a];
rho[i] += w * (fix_pressure->calc_pressure(rho[j], jtype) - rho[j] * dot);
rho[i] += w * (fix_pressure->calc_pressure(rho[j], j) - rho[j] * dot);
normwf[i] += w;
}
}
@ -192,7 +195,7 @@ void ComputeRHEOInterface::compute_peratom()
dot = 0;
for (a = 0; a < 3; a++) dot += (-fp_store[i][a] + fp_store[j][a]) * dx[a];
rho[j] += w * (fix_pressure->calc_pressure(rho[i], itype) + rho[i] * dot);
rho[j] += w * (fix_pressure->calc_pressure(rho[i], i) + rho[i] * dot);
normwf[j] += w;
}
}
@ -210,7 +213,7 @@ void ComputeRHEOInterface::compute_peratom()
if (status[i] & PHASECHECK) {
if (normwf[i] != 0.0) {
// Stores rho for solid particles 1+Pw in Adami Adams 2012
rho[i] = MAX(EPSILON, fix_pressure->calc_rho(rho[i] / normwf[i], type[i]));
rho[i] = MAX(EPSILON, fix_pressure->calc_rho(rho[i] / normwf[i], i));
} else {
rho[i] = rho0[itype];
}

4
src/RHEO/compute_rheo_property_atom.cpp
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@ -440,7 +440,7 @@ void ComputeRHEOPropertyAtom::pack_pressure(int n)
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit)
buf[n] = fix_pressure->calc_pressure(rho[i], type[i]);
buf[n] = fix_pressure->calc_pressure(rho[i], i);
else
buf[n] = 0.0;
n += nvalues;
@ -490,7 +490,7 @@ void ComputeRHEOPropertyAtom::pack_total_stress(int n)
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
if (index == index_transpose)
p = fix_pressure->calc_pressure(rho[i], type[i]);
p = fix_pressure->calc_pressure(rho[i], i);
else
p = 0.0;
buf[n] = viscosity[i] * (gradv[i][index] + gradv[i][index_transpose]) + p;

52
src/RHEO/fix_rheo_pressure.cpp
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@ -31,7 +31,7 @@
using namespace LAMMPS_NS;
using namespace FixConst;
enum { NONE, LINEAR, CUBIC, TAITWATER, TAITGENERAL };
enum { NONE, LINEAR, CUBIC, TAITWATER, TAITGENERAL , IDEAL };
static constexpr double SEVENTH = 1.0 / 7.0;
@ -39,12 +39,14 @@ static constexpr double SEVENTH = 1.0 / 7.0;
FixRHEOPressure::FixRHEOPressure(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg), c_cubic(nullptr), csq(nullptr), csqinv(nullptr), rho0(nullptr),
rho0inv(nullptr), tpower(nullptr), pbackground(nullptr), pressure_style(nullptr),
fix_rheo(nullptr)
rho0inv(nullptr), tpower(nullptr), pbackground(nullptr), gamma(nullptr),
pressure_style(nullptr), fix_rheo(nullptr)
{
if (narg < 4) error->all(FLERR, "Illegal fix command");
comm_forward = 1;
variable_csq = 0;
invertable_pressure = 1;
// Currently can only have one instance of fix rheo/pressure
if (igroup != 0) error->all(FLERR, "fix rheo/pressure command requires group all");
@ -55,6 +57,8 @@ FixRHEOPressure::FixRHEOPressure(LAMMPS *lmp, int narg, char **arg) :
memory->create(c_cubic, n + 1, "rheo:c_cubic");
memory->create(tpower, n + 1, "rheo:tpower");
memory->create(pbackground, n + 1, "rheo:pbackground");
memory->create(gamma, n + 1, "rheo:gamma");
for (i = 1; i <= n; i++) pressure_style[i] = NONE;
int iarg = 3;
@ -68,7 +72,7 @@ FixRHEOPressure::FixRHEOPressure(LAMMPS *lmp, int narg, char **arg) :
} else if (strcmp(arg[iarg + 1], "tait/water") == 0) {
for (i = nlo; i <= nhi; i++) pressure_style[i] = TAITWATER;
} else if (strcmp(arg[iarg + 1], "tait/general") == 0) {
if (iarg + 3 >= narg) utils::missing_cmd_args(FLERR, "fix rheo/pressure tait", error);
if (iarg + 3 >= narg) utils::missing_cmd_args(FLERR, "fix rheo/pressure tait/general", error);
double tpower_one = utils::numeric(FLERR, arg[iarg + 2], false, lmp);
double pbackground_one = utils::numeric(FLERR, arg[iarg + 3], false, lmp);
@ -89,6 +93,22 @@ FixRHEOPressure::FixRHEOPressure(LAMMPS *lmp, int narg, char **arg) :
pressure_style[i] = CUBIC;
c_cubic[i] = c_cubic_one;
}
invertable_pressure = 0;
} else if (strcmp(arg[iarg + 1], "ideal/gas") == 0) {
if (iarg + 2 >= narg) utils::missing_cmd_args(FLERR, "fix rheo/pressure ideal/gas", error);
double c_gamma_one = utils::numeric(FLERR, arg[iarg + 2], false, lmp);
iarg += 1;
for (i = nlo; i <= nhi; i++) {
pressure_style[i] = IDEAL;
gamma[i] = c_gamma_one;
}
variable_csq = 1;
if (atom->esph_flag != 1)
error->all(FLERR, "fix rheo/pressure ideal gas equation of state requires atom property esph");
} else {
error->all(FLERR, "Illegal fix command, {}", arg[iarg]);
}
@ -110,6 +130,7 @@ FixRHEOPressure::~FixRHEOPressure()
memory->destroy(c_cubic);
memory->destroy(tpower);
memory->destroy(pbackground);
memory->destroy(gamma);
}
/* ---------------------------------------------------------------------- */
@ -197,10 +218,11 @@ void FixRHEOPressure::unpack_forward_comm(int n, int first, double *buf)
/* ---------------------------------------------------------------------- */
double FixRHEOPressure::calc_pressure(double rho, int type)
double FixRHEOPressure::calc_pressure(double rho, int i)
{
double p = 0.0;
double dr, rr3, rho_ratio;
int type = atom->type[i];
if (pressure_style[type] == LINEAR) {
p = csq[type] * (rho - rho0[type]);
@ -215,15 +237,18 @@ double FixRHEOPressure::calc_pressure(double rho, int type)
rho_ratio = rho * rho0inv[type];
p = csq[type] * rho0[type] * (pow(rho_ratio, tpower[type]) - 1.0) / tpower[type];
p += pbackground[type];
} else if (pressure_style[type] == IDEAL) {
p = (gamma[type] - 1.0) * rho * atom->esph[i] / atom->mass[type];
}
return p;
}
/* ---------------------------------------------------------------------- */
double FixRHEOPressure::calc_rho(double p, int type)
double FixRHEOPressure::calc_rho(double p, int i)
{
double rho = 0.0;
int type = atom->type[i];
if (pressure_style[type] == LINEAR) {
rho = csqinv[type] * p + rho0[type];
@ -239,6 +264,21 @@ double FixRHEOPressure::calc_rho(double p, int type)
rho = pow(tpower[type] * p + csq[type] * rho0[type], 1.0 / tpower[type]);
rho *= pow(rho0[type], 1.0 - 1.0 / tpower[type]);
rho *= pow(csq[type], -1.0 / tpower[type]);
} else if (pressure_style[type] == IDEAL) {
rho = p * atom->mass[type] / ((gamma[type] - 1.0) * atom->esph[i]);
}
return rho;
}
/* ---------------------------------------------------------------------- */
double FixRHEOPressure::calc_csq(double p, int i)
{
int type = atom->type[i];
double csq2 = csq[type];
if (pressure_style[type] == IDEAL) {
csq2 = (gamma[type] - 1.0) * atom->esph[i] / atom->mass[type];
}
return csq2;
}

5
src/RHEO/fix_rheo_pressure.h
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@ -36,9 +36,12 @@ class FixRHEOPressure : public Fix {
void unpack_forward_comm(int, int, double *) override;
double calc_pressure(double, int);
double calc_rho(double, int);
double calc_csq(double, int);
int variable_csq;
int invertable_pressure;
private:
double *c_cubic, *csq, *csqinv, *rho0, *rho0inv, *tpower, *pbackground;
double *c_cubic, *csq, *csqinv, *rho0, *rho0inv, *tpower, *pbackground, *gamma;
int *pressure_style;
class FixRHEO *fix_rheo;

24
src/RHEO/pair_rheo.cpp
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@ -80,8 +80,8 @@ void PairRHEO::compute(int eflag, int vflag)
int pair_force_flag, pair_rho_flag, pair_avisc_flag;
int fluidi, fluidj;
double xtmp, ytmp, ztmp, wp, Ti, Tj, dT, csq_ave, cs_ave;
double rhoi, rhoj, rho0i, rho0j, voli, volj, Pi, Pj, etai, etaj, kappai, kappaj, eta_ave,
kappa_ave, dT_prefactor;
double rhoi, rhoj, rho0i, rho0j, voli, volj, Pi, Pj, etai, etaj, kappai, kappaj, csqi, csqj;
double eta_ave, kappa_ave, dT_prefactor;
double mu, q, fp_prefactor, drho_damp, fmag, psi_ij, Fij;
double *dWij, *dWji;
double dx[3], du[3], dv[3], fv[3], dfp[3], fsolid[3], ft[3], vi[3], vj[3];
@ -185,7 +185,13 @@ void PairRHEO::compute(int eflag, int vflag)
kappaj = conductivity[j];
}
if (!variable_csq) {
cs_ave = 0.5 * (cs[itype] + cs[jtype]);
} else {
csqi = fix_pressure->calc_csq(rhoi, i);
csqj = fix_pressure->calc_csq(rhoj, j);
cs_ave = 0.5 * (sqrt(csqi) + sqrt(csqj));
}
csq_ave = cs_ave * cs_ave;
pair_rho_flag = 0;
@ -221,7 +227,7 @@ void PairRHEO::compute(int eflag, int vflag)
if (fluidi && (!fluidj)) {
compute_interface->correct_v(vj, vi, j, i);
rhoj = compute_interface->correct_rho(j);
Pj = fix_pressure->calc_pressure(rhoj, jtype);
Pj = fix_pressure->calc_pressure(rhoj, j);
if ((chi[j] > 0.9) && (r < (cutk * 0.5)))
fmag = (chi[j] - 0.9) * (cutk * 0.5 - r) * rho0j * csq_ave * cutk * rinv;
@ -229,7 +235,7 @@ void PairRHEO::compute(int eflag, int vflag)
} else if ((!fluidi) && fluidj) {
compute_interface->correct_v(vi, vj, i, j);
rhoi = compute_interface->correct_rho(i);
Pi = fix_pressure->calc_pressure(rhoi, itype);
Pi = fix_pressure->calc_pressure(rhoi, i);
if (chi[i] > 0.9 && r < (cutk * 0.5))
fmag = (chi[i] - 0.9) * (cutk * 0.5 - r) * rho0i * csq_ave * cutk * rinv;
@ -238,6 +244,14 @@ void PairRHEO::compute(int eflag, int vflag)
rhoi = rho0i;
rhoj = rho0j;
}
// recalculate speed of sound, if necessary
if (variable_csq && ((!fluidi) || (!fluidj))) {
csqi = fix_pressure->calc_csq(rhoi, i);
csqj = fix_pressure->calc_csq(rhoj, j);
cs_ave = 0.5 * (sqrt(csqi) + sqrt(csqj));
csq_ave = cs_ave * cs_ave;
}
}
// Repel if close to inner solid particle
@ -480,6 +494,8 @@ void PairRHEO::setup()
csq = fix_rheo->csq;
rho0 = fix_rheo->rho0;
variable_csq = fix_pressure->variable_csq;
if (cutk != fix_rheo->cut)
error->all(FLERR, "Pair rheo cutoff {} does not agree with fix rheo cutoff {}", cutk,
fix_rheo->cut);

1
src/RHEO/pair_rheo.h
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@ -45,6 +45,7 @@ class PairRHEO : public Pair {
int rho_damp_flag;
int thermal_flag;
int interface_flag;
int variable_csq;
int harmonic_means_flag;