The research indicates that a numerical three-dimensional CFD analysis of a variable displacement vane pump has been utilized to investigate the impact of vane detachment from the pressure ring on pressure ripple. This involves re-meshing the fluid volume over the vane tip at every time step based on the forces acting on each vane's top and bottom. The numerical model, built with Simerics MP+, incorporates turbulence and cavitation models. The model was validated by comparing numerical data with experimental data. It was found that vane detachment happens during transition zones, generating unwanted pressure spikes due to a nonoptimized valve plate design. Predicting vane detachment is important for designing quieter and more durable pumps, as vane collisions on the stator ring can cause noise and premature wear. Even if volumetric efficiency is only slightly affected, pressure ripple is significantly influenced by vane detachment. In studying structural parameters and cavitation performance of sliding vane pumps, CFD simulations revealed that the maximum local gas volume fraction in a pump with one suction and discharge cavity was 1.54%, much lower than other pumps, reducing the negative effect of cavitation. Increasing sliding vanes decreased the cavitation area, and at 1500 r/min, local gas volume fractions varied with sliding vane numbers. An odd number of sliding vanes showed smaller local gas volume fractions than even numbers, and higher vane numbers led to higher cavitation area gas content. Reducing vane numbers and choosing odd numbers can improve cavitation performance. Regarding integrated electric-hydraulic pumps, a novel design combining an external-rotor brushless motor with a balanced vane pump addresses low reliability in harsh deep-sea environments. This design reveals that output flow linearly increases with input voltage and decreases non-linearly with increasing outlet pressure. Experimental results verified the design's characteristics.