Biomimetic analysis of escape gliding patterns: the role of ventral fin posture in flying fish-inspired robots

Flying fish evade predatory threats through cross-medium gliding manoeuvres, in which the ventral fins play a pivotal regulatory role. Although previous studies have examined the influence of ventral fin configuration on gliding stability, the dynamic characteristics of escape trajectories and the regulatory effects of ventral fin posture on gliding attitude remain poorly understood. Here, we employ a biomimetic approach to elucidate the gliding patterns exhibited by flying fish during escape manoeuvres. We systematically investigate how ventral fin posture regulates gliding attitude and identify an optimal ventral fin mounting configuration. Combining full-factor experimental testing with computational fluid dynamics (CFD) simulations, we propose that flying fish adopt distinct gliding trajectories to evade predators in different media, with dynamic ventral fin adjustments acting as a key regulatory mechanism. Furthermore, by extending the parameter space beyond that accessible through biological observation, this study provides new theoretical guidance for the aerodynamic design and optimisation of multi-fin biomimetic robots.