The hubless rim-driven thruster (RDT) has become increasingly interesting for ship propulsion. Gap flow has been proven as the main feature of RDT that cannot be simply neglected. In this study, based on a classical hubless RDT, the effects of the gap geometry are studied by adjusting its axial passage length, and inlet and outlet oblique angles. The hydrodynamic characteristics of the RDT were simulated with OpenFOAM based on the k – ω shear stress transport turbulence model. Due to the pressure increase after the main flow passes through the rotating blades, the flow inside gap is driven upstream, which is opposite to the main flow direction. It is found that the hydrodynamic efficiency is increased as the gap axial passage length is shortened, which is realized by increasing the oblique angle with the fixed inlet and outlet positions. Moving the inlet and outlet to further downstream and upstream positions has negligible effects on the hydrodynamic efficiency and leads to recirculating flow within the gap near its inlet. These findings shed light on the design of the gap geometry to improve the RDT hydrodynamic performance.

无轮毂轮缘驱动推进器 (RDT) 对船舶推进越来越感兴趣。间隙流已被证明是 RDT 的主要特征，不能简单地忽略。在这项研究中，基于经典的无轮毂 RDT，通过调整其轴向通道长度和入口和出口倾斜角来研究间隙几何形状的影响。基于k – ω的 OpenFOAM 模拟了 RDT 的流体动力学特性剪切应力传输湍流模型。由于主流通过旋转叶片后的压力增加，间隙内的流动被驱使上游，与主流方向相反。发现随着间隙轴向通道长度的缩短，流体动力效率增加，这是通过增加与固定入口和出口位置的倾斜角来实现的。将入口和出口移动到更远的下游和上游位置对流体动力效率的影响可以忽略不计，并导致其入口附近的间隙内的再循环流动。这些发现阐明了间隙几何结构的设计，以提高 RDT 流体动力学性能。