Simone Mancini

Bio: Simone Mancini is an academic researcher from University of Naples Federico II. The author has contributed to research in topics: Hull & Seakeeping. The author has an hindex of 9, co-authored 26 publications receiving 320 citations. Previous affiliations of Simone Mancini include Polytechnic University of Milan.

An Extended Verification and Validation Study of CFD Simulations for Planing Hulls

Abstract: In the context of marine application of computational fluid dynamic (CFD), it is well known that the numerical simulations of planing craft are significantly less reliable than that of displacement ships. For this reason, it is important to perform a comprehensive approach to the verification and validation (V&V) methodology and procedures for simulating CFD planing craft. In the first part of this paper, an assessment of the accuracy and effectiveness of different simulation setups and techniques for planing craft is performed. In the second part, the results of the V&V study are reported for three different hull models at four Froude numbers (Fr). The Unsteady Reynolds-Averaged Navier-Stokes code results were validated using benchmark experimental data obtained for three hull models characterized by systematic variation of the length to beam ratio. Grid independence, iteration, and time-step convergence analysis for response variables (resistance coefficients, wetted surfaces, and dynamic trim angles) were conducted using the main error and uncertainty estimation methods available in the literature. The same procedures were followed for the profiles of the wave patterns. The results showed that there was improved reliability of the numerical simulation of the planing craft in terms of the errors and uncertainties, related to the predictions of resistance, running attitude, and wave pattern. The results of the V&V study highlighted the fact that modeling of the planing craft is a critical point to improve the reliability of the numerical simulation.

Flettner Rotor Concept for Marine Applications: A Systematic Study

Abstract: The concept of Flettner rotor, a rotating cylinder immersed in a fluid current, with a top-mounted disk, has been analyzed by means of unsteady Reynolds averaged Navier-Stokes simulations, with the aim of creating a suitable tool for the preliminary design of the Flettner rotor as a ship’s auxiliary propulsion system. The simulation has been executed to evaluate the performance sensitivity of the Flettner rotor with respect to systematic variations of several parameters, that is, the spin ratio, the rotor aspect ratio, the effect of the end plates, and their dimensions. The Flettner rotor device has been characterized in terms of lift and drag coefficients, and these data were compared with experimental trends available in literature. A verification study has been conducted in order to evaluate the accuracy of the simulation results and the main sources of numerical uncertainty. All the simulation results were used to achieve a surrogate model of lift and drag coefficients. This model is an effective mathematical tool for the preliminary design of Flettner rotor. Finally, an example of assessment of the Flettner rotor performance as an auxiliary propulsion device on a real tanker ship is reported.

A systematic study of the rough water performance of planing boats. Part II: Irregular waves

Abstract: Abstract : A series of constant-deadrise models, varying in length, was tested in smooth water and regular waves to define the effects of deadrise, trim, loading, speed, length-beam ratio, and wave proportions on the added resistance, on heave and pitch motions, and on impact accelerations at the bow and center of gravity. Each of these parameters was varied independently of the others so as to obtain a proper evaluation of the effects of changing a single quantity. The results, presented in the form of response characteristics, cover a wide range of operating conditions; and show, quantitatively, the importance of design parameters on the rough-water performance of planing hulls.

Verification and validation of URANS simulations of the turbulent cavitating flow around the hydrofoil

Abstract: In this paper, we investigate the verification and validation (V&V) procedures for the URANS simulations of the turbulent cavitating flow around a Clark-Y hydrofoil. The main focus is on the feasibility of various Richardson extrapolation-based uncertainty estimators in the cavitating flow simulation. The unsteady cavitating flow is simulated by a density corrected model (DCM) coupled with the Zwart cavitation model. The estimated uncertainty is used to evaluate the applicability of various uncertainty estimation methods for the cavitating flow simulation. It is shown that the preferred uncertainty estimators include the modified Factor of Safety (FS1), the Factor of Safety (FS) and the Grid Convergence Index (GCI). The distribution of the area without achieving the validation at the Vv level shows a strong relationship with the cavitation. Further analysis indicates that the predicted velocity distributions, the transient cavitation patterns and the effects of the vortex stretching are highly influenced by the mesh resolution.