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lammps/src/USER-SMD/smd_kernels.h
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smd_kernels.h
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/* -*- c++ -*- ----------------------------------------------------------
*
* *** Smooth Mach Dynamics ***
*
* This file is part of the USER-SMD package for LAMMPS.
* Copyright (2014) Georg C. Ganzenmueller, georg.ganzenmueller@emi.fhg.de
* Fraunhofer Ernst-Mach Institute for High-Speed Dynamics, EMI,
* Eckerstrasse 4, D-79104 Freiburg i.Br, Germany.
*
* ----------------------------------------------------------------------- */
#ifndef SMD_KERNEL_FUNCTIONS_H_
#define SMD_KERNEL_FUNCTIONS_H_
namespace SMD_Kernels {
static inline double Kernel_Wendland_Quintic_NotNormalized(const double r, const double h) {
if (r < h) {
double q = 2.0 * r / h;
return pow(1.0 - 0.5 * q, 4) * (2.0 * q + 1.0);
} else {
return 0.0;
}
}
static inline double Kernel_Cubic_Spline(const double r, const double h) {
double q = 2.0 * r / h;
if (q > 2.0) {
return 0.0;
} else if ((q <= 2.0) && (q > 1.0)) {
return pow(2.0 - q, 3.0) / 6.0;
} else if ((q >= 0.0) && (q <= 1.0)) {
return 2. / 3. - q * q + 0.5 * q * q * q;
} else {
return 0.0;
}
}
static inline double Kernel_Barbara(const double r, const double h) {
double arg = (1.570796327 * (r + h)) / h;
double hsq = h * h;
//wf = (1.680351548 * (cos(arg) + 1.)) / hsq;
return -2.639490040 * sin(arg) / (hsq * h);
}
static inline void spiky_kernel_and_derivative(const double h, const double r, const int dimension, double &wf, double &wfd) {
/*
* Spiky kernel
*/
if (r > h) {
printf("r=%f > h=%f in Spiky kernel\n", r, h);
wf = wfd = 0.0;
return;
}
double hr = h - r; // [m]
if (dimension == 2) {
double n = 0.3141592654e0 * h * h * h * h * h; // [m^5]
wfd = -3.0e0 * hr * hr / n; // [m*m/m^5] = [1/m^3] ==> correct for dW/dr in 2D
wf = -0.333333333333e0 * hr * wfd; // [m/m^3] ==> [1/m^2] correct for W in 2D
} else {
wfd = -14.0323944878e0 * hr * hr / (h * h * h * h * h * h); // [1/m^4] ==> correct for dW/dr in 3D
wf = -0.333333333333e0 * hr * wfd; // [m/m^4] ==> [1/m^3] correct for W in 3D
}
// alternative formulation
// double hr = h - r;
//
// /*
// * Spiky kernel
// */
//
// if (domain->dimension == 2) {
// double h5 = h * h * h * h * h;
// wf = 3.183098861e0 * hr * hr * hr / h5;
// wfd = -9.549296583 * hr * hr / h5;
//
// } else {
// double h6 = h * h * h * h * h * h;
// wf = 4.774648292 * hr * hr * hr / h6;
// wfd = -14.32394487 * hr * hr / h6;
// }
// }
}
static inline void barbara_kernel_and_derivative(const double h, const double r, const int dimension, double &wf, double &wfd) {
/*
* Barbara kernel
*/
double arg = (1.570796327 * (r + h)) / h;
double hsq = h * h;
if (r > h) {
printf("r = %f > h = %f in barbara kernel function\n", r, h);
exit(1);
//wf = wfd = 0.0;
//return;
}
if (dimension == 2) {
wf = (1.680351548 * (cos(arg) + 1.)) / hsq;
wfd = -2.639490040 * sin(arg) / (hsq * h);
} else {
wf = 2.051578323 * (cos(arg) + 1.) / (hsq * h);
wfd = -3.222611694 * sin(arg) / (hsq * hsq);
}
}
/*
* compute a normalized smoothing kernel only
*/
static inline void Poly6Kernel(const double hsq, const double h, const double rsq, const int dimension, double &wf) {
double tmp = hsq - rsq;
if (dimension == 2) {
wf = tmp * tmp * tmp / (0.7853981635e0 * hsq * hsq * hsq * hsq);
} else {
wf = tmp * tmp * tmp / (0.6382918409e0 * hsq * hsq * hsq * hsq * h);
}
}
/*
* M4 Prime Kernel
*/
static inline void M4PrimeKernel(const double s, double &wf) {
if (s < 1.0) {
//wf = 1.0 - 2.5 * s * s + (3./2.) * s * s * s;
wf = 1.0 - s * s *(2.5 -1.5 *s);
} else if (s < 2.0) {
//wf = 0.5 * (1.0 - s) * ((2.0 - s) * (2.0 - s));
wf = 2.0 + (-4.0 + (2.5 - 0.5 * s)*s)*s;
} else {
wf = 0.0;
}
}
}
#endif /* SMD_KERNEL_FUNCTIONS_H_ */
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