74 lines
1.6 KiB
C
74 lines
1.6 KiB
C
/***************************************************************************/
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/*
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Coded by : Peter Berczik
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Version number : 1.0
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Last redaction : 2011.II.20. 13:00
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*/
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void calc_force_n_BH(double m1, double xx1[], double vv1[],
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double m2, double xx2[], double vv2[],
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double eps_BH,
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double *pot_n1, double a_n1[], double adot_n1[],
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double *pot_n2, double a_n2[], double adot_n2[])
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{
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/*
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INPUT
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m1 - mass of the 1 BH
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xx1[0,1,2] - coordinate of the 1 BH
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vv1[0,1,2] - velocity of the 1 BH
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m2 - mass of the 2 BH
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xx2[0,1,2] - coordinate of the 2 BH
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vv2[0,1,2] - velocity of the 2 BH
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eps_BH - force softening, can be even exactly 0.0 !
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OUTPUT
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pot_n1 for the 1 BH
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a_n1 [0,1,2] for the 1 BH
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adot_n1 [0,1,2] for the 1 BH
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pot_n2 for the 2 BH
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a_n2 [0,1,2] for the 2 BH
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adot_n2 [0,1,2] for the 2 BH
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*/
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int k;
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double r, r2, r3, r4, RP, x[3], v[3];
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for(k=0;k<3;k++)
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{
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x[k] = xx1[k] - xx2[k];
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v[k] = vv1[k] - vv2[k];
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}
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r2 = SQR(x[0]) + SQR(x[1]) + SQR(x[2]) + SQR(eps_BH);
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r = sqrt(r2);
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r3 = r2*r;
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r4 = r2*r2;
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RP = 3.0*(x[0]*v[0]+x[1]*v[1]+x[2]*v[2])/r;
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// Newton pot + acc & jerks
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*pot_n1 = -m2/r;
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*pot_n2 = -m1/r;
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for(k=0;k<3;k++)
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{
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a_n1[k] = -m2*x[k]/r3;
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a_n2[k] = m1*x[k]/r3;
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adot_n1[k] = -m2*(v[k]/r3 - RP*x[k]/r4);
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adot_n2[k] = m1*(v[k]/r3 - RP*x[k]/r4);
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}
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}
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/***************************************************************************/
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