Faltinsen is known for his work in hydrodynamics of high-speed vessels and liquid sloshing dynamics. He has written three textbooks on the subjects.[3][4][5] The books are translated to Chinese. The book on sea loads are also translated to Korean. Faltinsen has developed theoretical and numerical methods for explaining how ships, high speed vehicles, and offshore structures behave in waves. The so-called STF - Salvesen-Tuck-Faltinsen method to estimate wave induced movements and loads on ships presented in 1970 is still used as an engineering tool to day.[6] He has, together with Alexander Timokha, developed methods for analyzing how sloshing loads on to ships and they have analytically studied how large sloshing loads infer with constructions.[7] He has also, together with e.g. Zhao, made extensive studies of slamming loads [8]