Chapter 4 An AUV project applied to studies on manoeuvrability of underwater vehicles Ettore A. de Barros 1 , J.L.D. Dantas 1 , Luciano O. Freire 1 and Rodrigo L. Stoeterau 1 4.1 Introduction Predicting the autonomous underwater vehicle (AUV) manoeuvring performance is important during the vehicle’s design phase. This has impact on the design of the auto- pilot, and guidance systems, for instance, and influences the vehicle autonomy as well. A number of authors have applied numerical tools to predict added masses, static forces and moments, and the wake field of submarines and other underwater vehicles. Recently, methods based on computational fluid dynamics (CFD) were used to predict the stability derivatives of an AUV. For example, in the works of References 1 and 2, the forces and moments acting upon the AUVs hulls, when they are inclined to the flow (i.e. have an angle of attack), are compared with those obtained in experimental tests in the towing tank. Together with the static coeffi- cients, Phillips et al. [3] predicted the dynamic stability derivatives of the Autosub AUV simulating a turning manoeuvre, and compared with the dynamic efforts obtained by towing tank tests with a planar motion mechanism (PMM) [4]. Tang et al. [5] used CFD methods in the prediction of hydrodynamics coefficients of AUVs with non-conventional shapes. The validation was done by comparison of the vehicle trajectory obtained by dynamic simulations and manoeuvres performed in the field. Singh et al. [6] and Lauder et al. [7] used unsteady CFD simulations in their investigation of the propulsion performance and control of flapping airfoils, mimicking the fins of fishes for the new generation of biomechanics AUVs [8]. Beyond the identification of hydrodynamic coefficients, the CFD tools are also used to optimize the shape of AUVs [8,9] or the performance of AUV propellers [10], and to examine the efforts upon AUV hull during the docking process [11] and in the cooperative missions [12]. Currently, the CFD approach to parameter estimation requires a considerable degree of expertise on grid generation and on the mechanization of the supporting 1 Polytechnic School of University of S~ ao Paulo, Brazil