Underwater transportation is an essential approach for scientific exploration, maritime construction and military operations. Determining the hydrodynamic coefficients for a complex underwater transportation system comprising multiple vehicles is challenging. Here, the suitability of a quick and less costly semi-empirical approach to obtain the hydrodynamic coefficients for a complex transportation system comprising two Unmanned Underwater Vehicles (UUVs) is investigated, where the interaction effects between UUVs are assumed to be negligible. The drag results were verified by Computational Fluid Dynamics (CFD) analysis at the steady state. The semi-empirical results agree with CFD in heave and sway; however, they were overpredicted in surge due to ignoring the wake effects. Furthermore, experiments were performed for the validation of the time-domain motion simulations with semi-empirical and CFD results. The simulations which were performed with the CFD drags were close to the experiments. The semi-empirical approach could be relied on once a correction parameter is included to account for the interactive effect between multiple UUVs. Overall, this work makes a contribution by deriving a semi-empirical approach for the dynamic and controlling system of dual UUVs, with CFD and experiments applied to ascertain its accuracy and potential improvement.

中文翻译：

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两艘无人水下航行器运输系统的流体动力学建模：半经验，数值和实验分析

水下运输是科学探索，海事建设和军事行动的必不可少的方法。确定包括多辆车辆的复杂水下运输系统的水动力系数是具有挑战性的。在此，研究了一种快速且成本较低的半经验方法对于包含两个无人水下航行器（UUV）的复杂运输系统的流体力学系数的适用性，其中假定UUV之间的相互作用影响可以忽略不计。在稳态下，通过计算流体动力学（CFD）分析验证了阻力结果。半实证结果与CFD的波动和摇摆结果相吻合。然而，由于忽略了尾流效应，它们在浪涌中被高估了。此外，进行了实验，以验证具有半经验和CFD结果的时域运动仿真。用CFD阻力进行的模拟接近实验。一旦包括校正参数，就可以依靠半经验方法来解决多个UUV之间的交互作用。总体而言，这项工作通过推导双重UUV的动态和控制系统的半经验方法，CFD和实验来确定其准确性和潜在的改进做出了贡献。一旦包括校正参数，就可以依靠半经验方法来解决多个UUV之间的交互作用。总体而言，这项工作通过推导双重UUV的动态和控制系统的半经验方法，CFD和实验来确定其准确性和潜在的改进做出了贡献。一旦包括校正参数，就可以依靠半经验方法来解决多个UUV之间的交互作用。总体而言，这项工作通过推导双重UUV的动态和控制系统的半经验方法，CFD和实验来确定其准确性和潜在的改进做出了贡献。