function dg=gplus(x,y,z,x1,x2,y1,y2,z1,z2,p)

G=6.67e-11

t222=myfun(x,y,z,x2,y2,z2)

t122=myfun(x,y,z,x1,y2,z2)

t212=myfun(x,y,z,x2,y1,z2)

t221=myfun(x,y,z,x2,y2,z1)

t211=myfun(x,y,z,x2,y1,z1)

t121=myfun(x,y,z,x1,y2,z1)

t112=myfun(x,y,z,x1,y1,z2)

t111=myfun(x,y,z,x1,y1,z1)

dg=-G*p*1e6*(t222-t122-t212-t221+t211+t121+t112-t111) 转化为g.u.



function y=myfun(x,y,z,xi,eta,zeta)

R=sqrt((xi-x).^2+(eta-y).^2+(zeta-z).^2)

temp1=(xi-x).*log((eta-y)+R)

temp2=(eta-y).*log((xi-x)+R)

temp3=(zeta-z).*atan((zeta-z).*R/((xi-x).*(eta-y))) 书中所给公式

temp3=-(zeta-z).*atan((xi-x).*(eta-y)./(zeta-z)./R) 上式变换

y=temp1+temp2+temp3 -function dg = gplus (x, y, z, x1, x2, y1, y2, z1, z2, p) G = 6.67e-11　t222 = myfun (x, y, z, x2, y2, z2)　t122 = myfun (x, y, z, x1, y2, z2)　t212 = myfun (x, y, z, x2, y1, z2)　t221 = myfun (x, y, z, x2, y2, z1)　t211 = myfun (x, y, z, x2, y1, z1)　t121 = myfun (x, y, z, x1, y2, z1)　t112 = myfun (x, y, z, x1, y1, z2)　 t111 = myfun (x, y, z, x1, y1, z1)　dg =-G* p* 1e6* (t222-t122-t212-t221+t211+t121+t112-t111)　 converted the Gu function y = myfun, (x y, z, xi, eta, zeta) R = sqrt ((xi-x). ^ 2+ (eta-y). ^ 2+ (zeta-z). ^ 2)　temp1 = (xi-x).* log ((eta-y)+R)　temp2 = (eta-y).* log ((xi-x)+R)　 temp3 = (zeta-z).* atan ((zeta-z).* R/( (xi-x).* (eta-y)))　 book given formula Temp3 =- (Zeta-z)* ATAN ((Xi-X)* (ETA-y)/(Zeta- Z)/R)　the above formula transform Y = temp1+temp2+temp3