Hydrodynamics of high-speed robots driven by the combustion-enabled transient driving method

Abstract

Underwater vehicles play important roles in underwater observation, ocean resource exploration, and sample collection. Soft robots are a unique type of underwater vehicles due to their good environmental adaptability and motion flexibility, although they are weak in terms of actuation and response ability. The transient driving method (TDM) was developed to resolve these shortcomings. However, the interaction between the robots’ swift motions and flow fields has not yet been fully studied. In this study, a computational fluid dynamic model is developed to simulate the fluid fields disturbed by transient high-speed motions generated by the robots. Focusing on the dependence of robot dynamics on thrust force and eccentricity, typical structures of both flow and turbulence fields around the robots are obtained to quantitatively analyze robot kinematic performance, velocity distribution, vortex systems, surface pressure, and turbulence. The results demonstrate the high-speed regions at the robots’ heads and tails and the vortex systems due to sudden expansion, indicating a negative relationship between the maximum fluid velocity and eccentricity. The reported results provide useful information for studying the environmental interaction abilities of robots during operating acceleration and steering tasks. 目 的 水下航行器在水下观测、 海洋资源勘探和样本采集中发挥着重要作用. 软机器人是一种独特的水下机器人, 具有良好的环境适应性和运动灵活性, 但它们的驱动和响应能力较弱. 同时, 机器人的快速运动与流场之间的相互作用尚未得到充分研究. 为解决这些问题, 本文旨在开发一种计算流体动力学模型, 以模拟由机器人产生的瞬态高速运动所干扰的流场. 创新点 1. 通过流固耦合与动网格技术开发了瞬变速机器人水下运动的数模模型. 2. 基于偏心率和化学放能反应驱动过程, 建立二者与机器人水下运动表现、 压力场、 速度场和湍流结构的关系. 方 法 1. 关注机器人动力学对推力和偏心率的依赖性, 并开发基于流固耦合方法与动网格技术的计算流体力学模型. 2. 获得机器人周围湍流场的典型结构, 并定量分析速度分布、 涡流结构、 压力和湍流特性. 结 论 1. 机器人头部和尾部都会因突然加速而出现高流速区域, 且在推力较高的一侧拐角处出现湍涡; 机器人尾部产生的高 k (湍流动能) 区域随运动向内发展. 2. 本研究揭示了最大流速与偏心率之间的关系. 3. 机器人表面上的最大压力与推力呈正相关, 与偏心率呈负相关; 偏心率使机器人旋转, 会增强流场的扰动, 也会使头部区域的 k 和 ε (湍流耗散率) 降低.