Unstructured grid has been the main solution to solve fluid engineering problems in computational fluid dynamics (CFD). However, due to the randomness of data storage structure, the disorder of mesh topology and the irregularity of mesh shape, it brings great challenges to the development of high-precision numerical methods. In order to overcome the limitations of conventional unstructured methods, we have proposed VPM and THINC/QQ schemes for accurate and robust numerical simulation. Some high-fidelity interface two-phase flow models are also developed for compressible and incompressible flows. The results show that compared with the conventional method, the new model at least has the following advantages: 1) it greatly reduces the solution dependence on the shape and quality of the grid element; 2) it significantly improves the convergence behavior of numerical results with grid numbers and time steps; 3) it effectively suppresses the spurious velocity and numerical noises around the interface, so as to comprehensively enhance the accuracy and reliability of the computational results. This talk will also report some progresses for their applications to numerical simulation of complex flows in the field of ocean engineering.