#include <potential.>h
#include <potential_float.h> /* optional */
typedef struct {
string name;
string pars;
string file;
struct a_potential *next;
} a_potential;
void inipotential (npar, par, name)
int *npar; /* number of parameters (I) */double par[]; /* list of
parameters (I/O) */char *name; /* optional (file) name for data (I)
*/
void potential_double (ndim, pos, acc, pot, time)
const int *ndim; /* number of dimensions (I) */const double pos[];
/* position (I) */double acc[], *pot; /* forces and potential (O) */const
double *time; /* time (I) */
void potential_float (ndim, pos, acc,
pot, time)
const int *ndim; /* number of dimensions (I) */const float pos[];
/* position (I) */float acc[], *pot; /* forces and potential (O) */const
float *time; /* time (I) */
integer function inipotential (npar,
par, name)
integer npardouble precision par(*)character name*(*)
integer function potential_double
(ndim, pos, acc, pot, time)
integer ndim double precision pos(*)double precision acc(*) double
precision potdouble precision time
integer function potential_float (ndim,
pos, acc, pot, time)
integer ndim real pos(*)real acc(*) real potreal time
potential(5NEMO) is a ’filestructure’ which defines a potential (and force/density or velocity field) through a standardized interface routine, as described in potential(3NEMO) .
A potential(5NEMO) datafile must have two (or three) externally accessible routines inipotential and potential_double and/or potential_flot, (old name:potential) with a parameter sequence as described above. The parameters are all called by reference to allow interfaces with some common but more primitive languages. Notably FORTRAN is now supported in the BSD calling convention of parameters (see potentialf.c). The first parameter, par[0] in C, and par(1) in fortran, is reserved for the pattern speed. User written potentials must take this into account. And return the pattern speed (or it’s default) in that location. If another parameter describes the pattern speed (e.g. the lagrangian radius, as in athan92), inipotential must compute the pattern speed and return it in the first parameter.
harmonic wx,wy,wz 1,1,1 plummer m,a 1,1 log mc,rc,q 1,1,1 bar83 fm,fx,ca 1.334697416,8.485281374,0.2 hackforce tol,eps,rsize,fcells 1,0.025,4,0.75 ccd Iscale,Xcen,Ycen,Dx,Dy 1,0,0,1,1A full listing, including their mathematical expression can be found in the NEMO manual, see also $NEMO/text/manuals/potential.inc,, and of course in $NEMO/src/orbit/potential/data.
Most likely loadobj(3NEMO) will break under such circumstances.
Second: no I/O should be done. In practise this also means that this third parameter, potfile, of inipotential cannot be used, as is mostly serves as a filename. The reason is that we didn’t want the programs to have to link in huge fortran I/O libraries, including various portability problems.
There is one exception: potlist(1NEMO) is allowed to load potential(5NEMO) files with FORTRAN WRITE statements. After you have made sure the function works as you think, these statements must be Commented out and can then be reloaded by most other potential/orbit programs.
flowcode uses a potential which returns the (currently 2-dimensional) velocities at the requested input position. These are returned in the acc slot. The pot has no meaning, though is used to represent densities in programs like mkflowdisk(1NEMO) .
vpotcode uses a potential which expects the velocity to be input in the acc slot, but the returned arguments (acc and pot) have the same meaning. This is to emulate (non-coriolis) forces which depend on velocity.
mkflowdisk initializes a 2D disk based on the flow velocities.
L**2
Phi + ------
2 * R**2
but unlike motion in rotating potential this requires the authors of potentials
to modify their code in something like the following: (pos[0] is R, pos[1]
is z, pos[2] is not used) double tmp = sqr(ang_mom/pos[0]);
*pot += 0.5*tmp;
acc[0] += tmp / pos[0];
Because these potentials are implemented as simple functions, there can only be one in use. Unlike the ones in falcON.
~/src/orbit/potential potential.c, potential.h potentialf.c ~/text/manuals potential.inc (latex description)
13-Jul-87 V1.0: Original created PJT 8-Apr-88 V2.0: added parameter ’name’ for hackforce PJT 13-Mar-89 V2.1: added ’name_len’ in case fortran interface PJT 9-feb-90 V3.0: added time parameter to potential() PJT 24-may-92 V4.0: documented the new potential struct PJT 11-oct-93 V5.0: formalized get_pattern PJT 16-apr-96 documented ’flowcode’ and ’vpotcode’ deviations PJT 19-sep-01 documented _float/_double PJT 19-nov-03 more flow documentation, added mkflowdisk PJT 19-jul-04 promote acceleration(5) PJT