Gasdynamics and starbursts in major mergers of comparable-mass disk galaxies are studied using numerical simulations. The simulations show that gas inflows and starburst activity are common in all merger encounters, with the strength of inflows depending on the structure of the galaxies. Galaxies with dense central bulges experience stronger inflows in the final stages of merging, while bulgeless galaxies have weaker and earlier inflows. Orbital geometry has a modest effect on the onset of collisionally-induced activity. The inflows are primarily driven by gravitational torques from the host galaxy, with dense bulges stabilizing galaxies against bar modes and inflow until merging. Co-planar encounters produce the strongest inflows and starburst activity, while inclined mergers have less intense activity. The starbursts in bulge-containing galaxies represent a two-order-of-magnitude increase in star formation rate compared to isolated galaxies. These results match observed ultraluminous infrared galaxies, suggesting that internal structure, rather than orbital geometry, is key to producing such galaxies. The simulations also show that gas and stellar morphology, as well as star-forming properties, in these systems closely resemble those of observed ultraluminous infrared galaxies. The study highlights the importance of gas dynamics and star formation in shaping both active and ordinary galaxies. The simulations use a hybrid N-body/hydrodynamics code, TREESPH, to model galaxy mergers, incorporating star formation and gas depletion. The results show that the internal structure of the merging galaxies, particularly the presence of central bulges, significantly influences the dynamics and starburst activity. The simulations also demonstrate that the merger process can lead to the formation of elliptical galaxies and that the gas dynamics and star formation processes are crucial for understanding galaxy evolution. The study concludes that the internal structure of the galaxies, rather than orbital geometry, is the key factor in producing ultraluminous infrared galaxies.Gasdynamics and starbursts in major mergers of comparable-mass disk galaxies are studied using numerical simulations. The simulations show that gas inflows and starburst activity are common in all merger encounters, with the strength of inflows depending on the structure of the galaxies. Galaxies with dense central bulges experience stronger inflows in the final stages of merging, while bulgeless galaxies have weaker and earlier inflows. Orbital geometry has a modest effect on the onset of collisionally-induced activity. The inflows are primarily driven by gravitational torques from the host galaxy, with dense bulges stabilizing galaxies against bar modes and inflow until merging. Co-planar encounters produce the strongest inflows and starburst activity, while inclined mergers have less intense activity. The starbursts in bulge-containing galaxies represent a two-order-of-magnitude increase in star formation rate compared to isolated galaxies. These results match observed ultraluminous infrared galaxies, suggesting that internal structure, rather than orbital geometry, is key to producing such galaxies. The simulations also show that gas and stellar morphology, as well as star-forming properties, in these systems closely resemble those of observed ultraluminous infrared galaxies. The study highlights the importance of gas dynamics and star formation in shaping both active and ordinary galaxies. The simulations use a hybrid N-body/hydrodynamics code, TREESPH, to model galaxy mergers, incorporating star formation and gas depletion. The results show that the internal structure of the merging galaxies, particularly the presence of central bulges, significantly influences the dynamics and starburst activity. The simulations also demonstrate that the merger process can lead to the formation of elliptical galaxies and that the gas dynamics and star formation processes are crucial for understanding galaxy evolution. The study concludes that the internal structure of the galaxies, rather than orbital geometry, is the key factor in producing ultraluminous infrared galaxies.