Fluent 中最根本的类型要属 struct obj，来看看它的源码先。
struct obj
{
union {
struct {fixnum ncell; struct obj *vcell;} symbol;
struct {struct obj *car; struct obj *cdr;} cons;
struct {struct obj *env; struct obj *code;} closure;
struct {fixnum ncell; struct obj *(*f)();} subr;
struct {unsigned char data;} character;
struct {fixnum data;} fixednum;
struct {flonum data;} floatnum;
struct {fixnum ncell; fixnum length;} string;
struct {fixnum ncell; fixnum length;} vector;
struct {fixnum ncell; short valid;} continuation;
struct {fixnum ncell; struct obj *next;} free;
struct {fixnum ncell;} port;
struct {fixnum id; char *data;} foreign;
} as;
Sshortint gc_mark;
Sshortint type;
};
它由三部分组成：联合体 as，GC 标记和类型编号。
其中 as 的变化很多，可以用来表示需要的各种类型数据。
下面是一些数据类型的编号：
#define tc_nil 0
#define tc_true 1
#define tc_false 31
#define tc_cons 2
#define tc_symbol 3
#define tc_flonum 4
#define tc_fixnum 5
#define tc_char 6
#define tc_string 7
#define tc_vector 8
#define tc_continuation 9
#define tc_nm_vector 10
#define tc_free 11
#define tc_port 12
#define tc_lambda 13
#define tc_closure 14
#define tc_quote 15
#define tc_define 16
#define tc_setq 17
#define tc_begin 18
#define tc_if 19
#define tc_and 20
#define tc_or 21
#define tc_tenv 22
#define tc_access 23
#define tc_apply 24
#define tc_subr_0 25
#define tc_subr_1 26
#define tc_subr_2 27
#define tc_subr_3 28
#define tc_subr_4 29
#define tc_fsubr 30
#define tc_lsubr 32
#define tc_foreign 33
要说 Fluent 的数据结构，主要看其如何存储网格和模型信息。
这里先看看 Domain 相关的数据结构。
typedef struct domain_struct
{
/* Note: order of cell and face threads below must be
* maintained for thread_loop macros; modify TL_* masks
* when modifying. (Should perhaps rewrite as array
* of threads.)
*/
struct thread_struct *c; /* cell thread list */
struct thread_struct *nosolve_c; /* no solver cell thread list */
struct thread_struct *nosolve_ext_c; /* no solver exterior cell thread */
struct thread_struct *f; /* face thread list */
struct thread_struct *nosolve_f; /* no solver face thread list */
#if RP_NETWORK
struct thread_struct *nwc; /* network cell */
struct thread_struct *nwf; /* network face */
#endif
#if RP_HANG
struct objp_struct *bridge_fl; /* hanging node bridge faces */
#endif
#if RP_NODE
struct objp_struct *ext_vl;
struct objp_struct *ext_fl;
struct objp_struct *corner_vl;
# if RP_HANG && RP_EDGE
struct objp_struct *corner_el;
# endif
struct dom_neighbor_struct *neighbors; /* phasing out */
#if NEW_PARALLEL_NEIGHBOR
struct domain_neighbor_struct *neighbor;
#endif /* NEW_PARALLEL_NEIGHBOR */
#endif
struct domain_struct *_coarse;/* coarser domain (FAS MG) */
struct domain_struct *_fine; /* finer domain (FAS MG) */
int mg_level; /* grid level; 0 is finest level */
real dtmin; /* global minimum timestep */
#if RP_HOST
int cell_count, face_count;
#endif
int node_count;
int nosolve_face_count, nosolve_cell_count;
#if RP_EDGE
int edge_count;
#endif
#if RP_HANG
int bridge_face_count;
#endif
#if RP_NODE
int neighbor_count;
int corner_node_count;
# if RP_HANG && RP_EDGE
int corner_edge_count;
# endif /* RP_HANG && RP_EDGE */
#endif /* RP_NODE */
struct timer_struct flow_timer, case_timer, data_timer;
#if !RP_HOST
cxboolean active;
#else
cxboolean *active;
#endif /* RP_HOST */
struct storage_marker_struct sm[SM_MAX];
struct sliding_interface *sliding_interfaces;
#if RP_DYNAMIC_MESH
struct dynamic_thread_struct *dynamic_threads;
#endif
int id; /* id number (unique id for each domain) */
int index; /* index with respect to place within list of sub-domains
* of parent - i.e. phase index.
* domains that are not sub-domain (e.g. top-level mixture
* or single fluid) have index = NULL_INDEX */
int level; /* level (e.g. how far above root) */
int n_domains; /* number of sub domains branching from this domain */
/* pointers to sub-domains; max size +1 used to permit less
complicated logic in the third expression of the for loops
used in the sub domain loop macros */
struct domain_struct *sub_domains[MAX_SUB_DOMAINS+1];
struct domain_struct *interaction; /* phase interactions domain */
struct domain_struct *superdomain; /* pointer back to superdomain */
struct domain_global_flags globals; /* global flags */
char name[MATERIAL_NAME_LENGTH];
char material_name[MATERIAL_NAME_LENGTH];
cxboolean model[DOMAIN_MODEL_MAX];
Species_Model species_model;
Property property[PROP_MAX];
Property *complex_property[COMPLEX_PROP_MAX];
/* residuals */
real *res[MAX_EQNS];
#if RP_NODE
real *gres[MAX_EQNS];
#endif
real rtrms[MAX_EQNS];
real rtrms_final[MAX_EQNS];
#if RP_NODE
real grtrms[MAX_EQNS];
real grtrms_final[MAX_EQNS];
#endif
real *res_scale[MAX_EQNS];
real rscale[MAX_EQNS];
#if RP_NODE
real *gres_scale[MAX_EQNS];
real grscale[MAX_EQNS];
#endif
char equation_labels[MAX_EQNS][32];
void *CellFunc; /* Pointer to CELL_FUNCTION array */
int NCellFunc; /* total number of cell function */
} Domain;