Objectives  This paper researches the influence of hydrodynamic interaction between two parallel vehicles advancing in close proximity on maneuvering.

  Methods  Based on an unsteady RANS approach, the hydrodynamic interaction between two parallel ship models advancing in calm water in close proximity is analyzed via numerical 3D simulations. The effects of transverse and longitudinal distances on hydrodynamic forces acting on the hull under distinct forward velocities are investigated. Meanwhile, the changes and contributions of various disturbance components in the hydrodynamic interactions of two parallel ships are discussed.

  Results  The results indicate that the lateral force reaches its peak when the longitudinal distance between the ships' centers is zero, with each ship drawing the other close. The effect of lateral interaction sees a downward trend with the lateral distance increases, with the maximum decrease of lateral force reaching 50%in the studied range. The longitudinal distance has a great effect on yaw moment, resulting in changes in value and direction. It is easier for two ships to collide when they are near or have just pulled away. The influence of wave-making on the hydrodynamic interaction between two hulls can be ignored at low speeds, while at high speeds it should be taken into account.

  Conclusions  The numerical results of this paper provide the basis for constructing a mathematical model of the interaction between two ships.