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BGK: configure h0, k #328

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Apr 3, 2024
Merged

BGK: configure h0, k #328

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cfb2733
bgk_params: load h0, k from file
Jan 16, 2024
bd5609b
sample_bgk_params: +h0, k
Jan 16, 2024
e40b9f0
bgk, bgk_params: mv get_beta
Jan 30, 2024
9470f88
bgk_params: don't hardcode beta
Jan 30, 2024
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21 changes: 4 additions & 17 deletions src/psc_bgk.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -208,28 +208,15 @@ inline double getIonDensity(double rho)
return std::exp(-potential / g.T_i);
}

// ======================================================================
// get_beta
// Return the conversion factor from paper units to psc units.

double get_beta()
{
// PSC is normalized as c=1, but the paper has electron thermal velocity
// v_e=1. Beta is v_e/c = sqrt(Te_paper) / sqrt(Te_psc)
const double PAPER_ELECTRON_TEMPERATURE = 1.;
const double pscElectronTemperature = parsedData->get_interpolated(COL_TE, 0);
return std::sqrt(pscElectronTemperature / PAPER_ELECTRON_TEMPERATURE);
}

// ======================================================================
// v_phi_cdf
// Cumulative distribution function for azimuthal electron velocity

double v_phi_cdf(double v_phi, double rho)
{
// convert units from psc to paper
v_phi /= get_beta();
rho /= get_beta();
v_phi /= get_beta(*parsedData);
rho /= get_beta(*parsedData);

double B = g.Hx;
double sqrt2 = std::sqrt(2);
Expand Down Expand Up @@ -259,8 +246,8 @@ struct pdist
z{z},
rho{rho},
v_phi_dist{[=](double v_phi) { return v_phi_cdf(v_phi, rho); }},
v_rho_dist{0, get_beta()},
v_x_dist{0, get_beta()}
v_rho_dist{0, get_beta(*parsedData)},
v_x_dist{0, get_beta(*parsedData)}
{}

Double3 operator()()
Expand Down
25 changes: 20 additions & 5 deletions src/psc_bgk_util/bgk_params.hxx
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,20 @@
#include "params_parser.hxx"
#include "input_parser.hxx"

// ======================================================================
// get_beta
// Return the conversion factor from paper units to psc units.

double get_beta(ParsedData& data)
{
// PSC is normalized as c=1, but the paper has electron thermal velocity
// v_e=1. Beta is v_e/c = sqrt(Te_paper) / sqrt(Te_psc)
const double PAPER_ELECTRON_TEMPERATURE = 1.;
const int COL_TE = 3;
const double pscElectronTemperature = data.get_interpolated(COL_TE, 0);
return std::sqrt(pscElectronTemperature / PAPER_ELECTRON_TEMPERATURE);
}

// ======================================================================
// getCalculatedBoxSize

Expand All @@ -17,7 +31,7 @@
// The negative Gaussian has a mean given by the RHS of the equation. It drifts
// up, approaching a line with slope B/2. The negative Gaussian is the source
// of the spike.
double getSpikeSize(double B, double k)
double getSpikeSize(double B, double k, double beta)
{
double max_v = 4.5;
// solve cubic with linear coefficient = 0
Expand All @@ -30,7 +44,6 @@ double getSpikeSize(double B, double k)
double q = p * p * p + t;
double s = sqrt(t * (2. * q - t));

double beta = .001; // FIXME don't hardcode this (see psc_bgk.cxx get_beta())
double r = (std::cbrt(q + s) + std::cbrt(q - s) + p) * beta;
return r;
}
Expand All @@ -52,7 +65,7 @@ double getHoleSize(ParsedData& data)
// Calculates a box size big enough to resolve the spike and the hole.
double getCalculatedBoxSize(double B, double k, ParsedData& data)
{
double spike_size = getSpikeSize(B, k);
double spike_size = getSpikeSize(B, k, get_beta(data));
double hole_size = getHoleSize(data);
LOG_INFO("spike radius: %f\thole radius: %f\n", spike_size, hole_size);
return 2 * std::max(spike_size, hole_size);
Expand All @@ -76,8 +89,8 @@ struct PscBgkParams
int n_patches; // number of patches
int nicell; // number of particles per gripdoint when density=1

double k = .1; // a parameter for BGK solutions
double h0 = .9; // a parameter for BGK solutions
double k; // a parameter for BGK solutions
double h0; // a parameter for BGK solutions

int fields_every; // interval for pfd output
int moments_every; // interval for pfd_moments output
Expand Down Expand Up @@ -133,6 +146,8 @@ struct PscBgkParams
T_e_coef = parsedParams.getOrDefault<double>("T_e_coef", 1);

maxwellian = parsedParams.getOrDefault<bool>("maxwellian", false);
k = parsedParams.getOrDefault<double>("k", .1);
h0 = parsedParams.getOrDefault<double>("h0", .9);

n_grid_3 = parsedParams.getOrDefault<int>("n_grid_3", 1);
box_size_3 = parsedParams.getAndWarnOrDefault<double>("box_size_3", -1);
Expand Down
2 changes: 2 additions & 0 deletions src/psc_bgk_util/sample_bgk_params.txt
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Expand Up @@ -22,6 +22,8 @@ T_i 0 normally 0, or 1e-6 for boltzmann
# Run-specific parameters
path_to_data /CHANGE/ME
H_x 1
h0 .9
k .1

n_grid 16
n_grid_3 1 number of gridpoints on x axis; 1 for 2D, 2+ for 3D
Expand Down
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