Hydrodynamic forces and moments acting on a remotely operate vehicle with an asymmetric shape moving in a vertical plane

Abstract

a b s t r a c tHydrodynamic models and coefficients are important parameters for predicting the maneuverability of a remotely operated vehicle (ROV). In this study, we present an experimental analysis of the hydrodynamic behavior of a new ROV with an asymmetric shape, which has a high capacity for holding more instruments onboard than other ROVs. We performed a series of towing tests where this ROV moved in a vertical plane. We provide the fitting formulae for forces and moments, as well as the corresponding hydrodynamic coefficients, which can be used to simulate the motions and to predict the maneuverability of the ROV. We also discuss the effects of the ROV's asymmetric shape on its hydrodynamic coefficients.

Experimental study on inertial hydrodynamic behaviors of a complex remotely operated vehicle

“…In the other approach, the inertial parts are separated from the total measured results firstly, and then uses the Least Squared Method to only fit inertial coefficients. The direct use of the Least Squared Method (i.e., the 1 st approach) is similar in principle to what has been discussed in our previous paper (Xu et al [19]) for analyzing the drag forces and moments corresponding to motions with constant velocities. The main difference is that the equations for fitting used here are these including the accelerations as given in…”

“…(11)- (14), rather than those equations in terms of only constant velocities in [19]. The basic theory of the least square method is the same and so more details will not be given here.…”

“…Generally, the components of damping forces and moments can be expressed by the multivariate Taylor series in terms of the velocities [17]. However, the magnitudes of the oscillation velocities are small during oscillation tests and so it is reasonable to take the series to the first order and ignore the asymmetry of damping hydrodynamic forces and moments caused by the asymmetrical model shape, according to what is discussed in [19]. In other words, it is here assumed that all damping hydrodynamic forces and moments acting on the ROV model during oscillation tests are linear and can be written as…”

“…This ROV has better capacity for heavy duties, and has a complex open-framed hull with its front-rear and top-bottom asymmetry, which is quite different from those ROV discussed in the cited papers above. Xu et al [19] presented the experimental results for the drag forces and moments of this ROV subjected to constant velocities, which are measured by holding the models in water flowing with a constant speed or towing the section at a in [19]. …”

Hydrodynamic calculation and analysis of a complex-shaped underwater robot based on computational fluid dynamics and prototype test

“…The design of the robot's controller and the analysis of its maneuverability are based on a dynamic model. In this approach, a mathematical model of hydrodynamic force 5 treated as a disturbance factor is a main component of the dynamics to improve control precision. Hence, the analysis of the hydrodynamic characteristics is significant.…”