On analytical models of vertical water entry of a symmetric body with separation and cavity initiation

• The Logvinovich model of separation from chines is extended.
• A corrected Logvinovich model of separation from chines is proposed.
• The concept of Fictitious Body Continuation is investigated.
• Smooth body separation and separation with deceleration are investigated.
• Comparisons with analytical, numerical and experimental results are presented.

Two-dimensional water entry with separation is investigated through different analytical models. This study focuses on the transient force acting on the body when the jet root detaches from the body surface and a cavity starts to develop behind the body. Logvinovich (1972) suggested a separation model in order to estimate the transient force acting on a finite wedge entering water. This model is revisited, developed further and assessed through comparison with more recent works on flow separation. The concept of Fictitious Body Continuation combined with the Modified Logvinovich Model is also investigated to estimate the transient drag during the initial stage of cavity formation. This model accounts for the variation in speed of the body during the separation stage. Several case studies are presented in order to show the relevance of this model. These include separation from chines and separation from smooth bodies.