The study investigates the maneuverability, and hydrodynamic performance of the underwater robot installs hydrofoils and ducted Propellers symmetrically in a uniform flow field. Numerical simulation is based on the multiple computational fluid dynamics (CFD) technique, such as overlapping grid, sliding mesh, and six-degrees-freedom model. The reliability of the CFD method is verified by the experimental result of the thrust of ducted Propellers. The numerical result indicates that the joint influence of ducted propellers and hydrofoils is significant for the control of the underwater robot.
The underwater robot is widely used in the complex ocean environment, which can explore marine resources and carry out the mission of investigating parameters of the hydrological environment. Ducted propellers, hydrofoils, and umbilical cable are major tools to control the underwater robot when the user adjusts its rotation speed and the length of the umbilical cable (Kim 2006; Marani and Choi and Yuh, 2009; Wu et.al, 2005) . Control equipment provides multiple motion degrees of the underwater robot with forces. In order to investigate the hydrodynamic response of the underwater robot, the underwater robot need to be comprehensively considered the influence of control equipment.
It is matter to study the hydrodynamic performance of the underwater robot with a control mechanism, which is studied by lots of scholars. In studying the influence of the underwater robot with propellers, Wu et al. (2010) discuss hydrodynamic characteristics of ducted propeller in turning motion, and consider the effect of underwater robot on the thrust coefficient. Barros and Dantas (2012) investigate the hydrodynamic forces and moment on a ducted propeller according to a numerical (CFD) simulation and analytical and semi-empirical, ASE approaches. Wu et al. (2015) simulate the hydrodynamic performance of ducted propellers attached in an underwater robot considering the influence of the main body of the underwater robot. Zhou and Zhao (2020) numerically discuss the influence of the deflection angle, rotation speed, and thrusters (ducted propellers) spacing on the ROV thrust performance. Song et al. (2020) combine the nonlinear controller with multi-vector propellers to evaluate the ROV dynamics and attitude's influence. In investigating the influence of underwater robot with umbilical cable, Fang et al. (2007) utilize Runge-Kutta numerical method to solve the motion of underwater robot and the configuration of the umbilical cable. Vu et al. (2017) present a new mathematical model to simulate the hydrodynamic behavior of an underwater robot with the umbilical cable effect. Wu et al. (2018) propose an integrated hydrodynamics and control model of tethered underwater robot considering the mutual hydrodynamic influence of different portions of the robot system and some factors of ocean environment. Wu and Chen (2019) propose a three-dimensional hydrodynamics and control model to simulate a tethered underwater robot system that adopts a proportional-integral-derivative (PID) control algorithm. In considering the effect of hydrofoils, Quan et al. (2017) analyze the pressure of the hydrofoil and the change of the lift-resistance at different attack angles, the best angle of attack without the main body of the underwater robot.
