https://github.com/florentrenaud/nbody6tt
Tip revision: 8a4716382ead3ece116c48a4ae5c65f8c9534437 authored by Florent on 29 January 2015, 12:19:28 UTC
Nbody6 - 29 January 2015 (added GPU2/Build/.gitkeep)
Nbody6 - 29 January 2015 (added GPU2/Build/.gitkeep)
Tip revision: 8a47163
fbulge.f
SUBROUTINE FBULGE(XI,XIDOT,FM,FD)
*
*
* Gamma/eta potential for the bulge.
* ----------------------------------
*
IMPLICIT REAL*8 (A-H,O-Z)
COMMON/GALAXY/ GMG,RG(3),VG(3),FG(3),FGD(3),TG,
& OMEGA,DISK,A,B,V02,RL2,GMB,AR,GAM,ZDUM(7)
REAL*8 XI(3),XIDOT(3),FM(3),FD(3)
*
*
* Obtain force and first derivative for gamma/eta model (Dehnen 1993).
*
* phi(r) = -GM/[a(2-g)] * [ 1 - (1+a/r)**(g-2) ] (g # 2)
* phi(r) = -GM/a*ln(1 + a/r) (g = 2)
*
RR = SQRT(XI(1)**2 + XI(2)**2 + XI(3)**2)
RRD = (XI(1)*XIDOT(1) + XI(2)*XIDOT(2) + XI(3)*XIDOT(3))/(RR*RR)
RRD = RRD*(AR*GAM + 3.0*RR)/(RR + AR)
H3 = (GMB/RR**3)*(1.0 + AR/RR)**(GAM-3.0)
*
DO 10 K = 1,3
FM(K) = -H3*XI(K)
FD(K) = -H3*(XIDOT(K) - RRD*XI(K))
10 CONTINUE
*
RETURN
*
END