test_function.c

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// Copyright (c) 2024 The YAC Authors
//
// SPDX-License-Identifier: BSD-3-Clause
 
#ifndef TEST_FUNCTION
#define TEST_FUNCTION
#include <math.h>
#include "test_function.h"
#include "geometry.h"
 
double yac_test_func(double lon, double lat) {
 
  double tmp = sin(lon * 2.0);
  return tmp * cos(lat * 3.0);
}
 
double yac_test_func_deg(double lon, double lat) {
 
  return yac_test_func(lon * YAC_RAD, lat * YAC_RAD);
}
 
double yac_test_ana_fcos(double lon, double lat) {
 
  double dp_length = 1.2 * M_PI;
  double coef = 2.0;
  double coefmult = 1.0;
  return coefmult * (coef - cos(M_PI * acos(cos(lon)*cos(lat) )/dp_length));
}
 
double yac_test_ana_fcossin(double lon, double lat) {
 
  double dp_length = 1.0 * M_PI;
  double coef = 21.0;
  double coefmult = 3.846 * 20.0;
  return coefmult * (coef - cos(M_PI*(acos(cos(lon)*cos(lat))/dp_length)) *
                            sin(M_PI*(asin(sin(lon)*sin(lat))/dp_length)));
}
 
double yac_test_one(double lon, double lat) {
  return 1.0;
}
 
double yac_test_gulfstream(double lon, double lat) {
 
  // Analytical Gulf Stream
  double gf_coef = 1.0; // Coefficient for Gulf Stream term (0.0 = no Gulf Stream)
  double gf_ori_lon = -80.0 * YAC_RAD; // Origin of the Gulf Stream
  double gf_ori_lat =  25.0 * YAC_RAD; // Origin of the Gulf Stream
  double gf_end_lon =  -1.8 * YAC_RAD; // End point of the Gulf Stream
  double gf_end_lat =  50.0 * YAC_RAD; // End point of the Gulf Stream
  double gf_dmp_lon = -25.5 * YAC_RAD; // Point of the Gulf Stream decrease
  double gf_dmp_lat =  55.5 * YAC_RAD; // Point of the Gulf Stream decrease
 
  double dr0 = sqrt(pow(gf_end_lon - gf_ori_lon, 2.0) +
                    pow(gf_end_lat - gf_ori_lat, 2.0));
  double dr1 = sqrt(pow(gf_dmp_lon - gf_ori_lon, 2.0) +
                    pow(gf_dmp_lat - gf_ori_lat, 2.0));
 
  if (lon > M_PI) lon -= 2.0 * M_PI;
  if (lon < -M_PI) lon += 2.0 * M_PI;
 
  double dx = lon - gf_ori_lon;
  double dy = lat - gf_ori_lat;
  double dr = sqrt(dx * dx + dy * dy);
  double dth = atan2(dy, dx);
  double dc = 1.3 * gf_coef;
  if (dr > dr0) dc = 0.0;
  if (dr > dr1) dc = dc * cos(M_PI*0.5*(dr-dr1)/(dr0-dr1));
  return yac_test_ana_fcos(lon, lat) +
         (MAX(1000.0 * sin(0.4 * (0.5*dr+dth) +
          0.007*cos(50.0*dth) + 0.37*M_PI),999.0) - 999.0) * dc;
}
 
double yac_test_harmonic(double lon, double lat) {
  return 2.0 + pow(sin(2.0 * lat), 16.0)  * cos(16.0 * lon);
}
 
double yac_test_vortex(double lon, double lat) {
  double dLon0 = 5.5;
  double dLat0 = 0.2;
  double dR0   = 3.0;
  double dD    = 5.0;
  double dT    = 6.0;
 
  double dSinC = sin(dLat0);
  double dCosC = cos(dLat0);
 
  // Find the rotated longitude and latitude of a point on a sphere
  //     with pole at (dLon0, dLat0).
  double dCosT = cos(lat);
  double dSinT = sin(lat);
 
  double dTrm = dCosT * cos(lon - dLon0);
  double dX   = dSinC * dTrm - dCosC * dSinT;
  double dY   = dCosT * sin(lon - dLon0);
  double dZ   = dSinC * dSinT + dCosC * dTrm;
 
  double dlon = atan2(dY, dX);
  if(dlon < 0.0) dlon = dlon + 2.0 * M_PI;
  double dlat = asin(dZ);
 
  double dRho = dR0 * cos(dlat);
  double dVt = 3.0 * sqrt(3.0)/2.0/cosh(dRho)/cosh(dRho)*tanh(dRho);
  double dOmega = (dRho == 0.0)?0.0:dVt/dRho;
 
  return 2.0 * (1.0 + tanh(dRho / dD * sin(dlon - dOmega * dT)));
}
 
#endif // TEST_FUNCTION