Mathematical models of imbibition under different boundary conditions were built with piston-like displacement assumption. Effect of gravity and capillary pressure on imbibition under OEO (single boundary) and TEO-OW (mixed boundary) boundary conditions are studied. It shows that oil is produced only by counter-current imbibition under OEO boundary conditions. Gravity inhibits imbibition as the open face is at the lower end face of core and gravity promotes imbibition as the open face is at the upper end face of core. Oil is produced by combination of co-and counter-current imbibition under TEO-OW boundary condition. Gravity inhibits counter-current imbibition and promotes co-current imbibition under TEO-OW boundary condition. Gravity is dominant driving force as the inverse Bond number is smaller and capillary pressure is dominant driving force as inverse Bond number is greater. In addition, effect of gravity and capillary pressure on imbibition under OEO and TEO-OW boundary conditions are studied. It shows that oil production by gravity under OEO boundary condition is greater than that under TEO-OW boundary condition with same inverse Bond number. The rate of oil production under OEO boundary condition is faster than that under TEO-OW boundary condition as inverse Bond number is smaller and opposite phenomena is observed as inverse Bond number is greater.
A direct Monte-Carlo simulation method was developed to calculate neutron yield and spectrum in (α, n) reaction. It is based on continuous collision method, using stopping power computed by the program SRIM to simulate the moderation of α-particle and the ACE format of the nuclear data library JENDL/AN-2005 to calculate the neutron yield and spectrum in (α, n) reaction. Moreover, a (α, n)-simulator was developed based on the program NPTS. (α, n) neutron yields of light nuclides obtained in our simulations are consistent with experiments. In terms of (α, n) neutron spectrum, our results are in good agreement with experiments in the cases of B, F and O targets, while deviations are present in the cases of C, Al and Si.