  We investigate the energy of the gravitational wave from a binary black hole
merger by the coalescence of two Kerr black holes with an orbital angular
momentum. The coalescence is constructed to be consistent with particle
absorption in the limit in which the primary black hole is sufficiently large
compared with the secondary black hole. In this limit, we analytically obtain
an effective gravitational spin--orbit interaction dependent on the alignments
of the angular momenta. Then, binary systems with various parameters including
equal masses are numerically analyzed. According to the numerical analysis, the
energy of the gravitational wave still depends on the effective interactions,
as expected from the analytical form. In particular, we ensure that the final
black hole obtains a large portion of its spin angular momentum from the
orbital angular momentum of the initial binary black hole. To estimate the
angular momentum released by the gravitational wave in the actual binary black
hole, we apply our results to observations at the Laser Interferometer
Gravitational-Wave Observatory: GW150914, GW151226, GW170104, GW170608, and
GW170814.
