1,721,110 research outputs found
On the application of the single-phase level set method to naval hydrodynamic flows
No full textThe application of the single-phase level set approach to the numerical simulations of three-dimensional free surface flows around complex geometries, at both non-breaking and breaking regimes is presented. In this approach only the liquid phase is simulated and the level set function is used as tracking device to locate the free surface position. The extrapolation of the solution in the dummy points in the gaseous phase is such that second-order accuracy is maintained also in the points adjacent to the free surface; the time evolution of the level set function and the re-initialization step have been merged so to get a function which is a distance function everywhere, and satisfies, at the same time, the kinematic condition on the free surface. The implementation of this technique into a general purpose Reynolds averaged Navier-Stokes (RANS) equations solver developed at INSEAN [Di Mascio A, Broglia R, Favini B. A Second Order Godunov-type Scheme for Naval Hydrodynamics. Kluwer Academic/Plenum Publishers; 2001, p. 253-61], is described in details; capabilities of the algorithm in dealing with non-breaking and breaking flows in the naval hydrodynamic context will be demonstrated by using a submerged hydrofoil and two different ship hulls in straight course as test cases. Comparisons with both experimental data and numerical surface fitting computations are presented; convergence properties of the algorithm, as well as validation and verification assessment will be also discussed. © 2006 Elsevier Ltd. All rights reserved
Multigrid acceleration of second order ENO scheme from low subsonic to high supersonic ....
No full textAnalysis of the flow around a manoeuvring VLCC
No full textThis work describes the numerical simulation of a turning circle manoeuvre performed by the MOERI KVLCC2 induced by the rotation of the rudder. To this purpose, the Navier-Stokes equations are integrated, the hydrodynamical forces acting on the hull are computed and the hull is moved at each time step according to the rigid body equations. Because of the scarceness of experimental results for this kind of simulations, the validation of the proposed method is postponed to the oral presentation when the data from the SIM- MAN 2008 Workshop (http://www.simman2008.dk/) will be available. Copyright © 2008 by ASME
Numerical simulation of the flow around an array of free-surface piercing cylinders in waves
No full textThe flow around four free-surface piercing cylinders in waves is simulated by an Euler solver. Three different angles of the incoming wave front are considered in order to investigate the variation of the resulting global and local loads on the four bodies. The discretization of the fluid domain has been made easy and efficient by the use of a chimera method for the generation of the computational mesh. The free-surface has been simulated by a single-phase level set approach
Numerical simulation of the flow around an array of free-surface piercing cylinders in waves
No full textThis work deals with the viscous flow around an array of cylinders impinged by an incoming wave. Different configurations are considered in order to evaluate me effects of both wave heading and wave height on the loads applied to the bodies and on the run-ups. The results are also compared to previous calculations obtained with the assumption of inviscid flow with the aim of evaluating the contribution of viscosity. Copyright © 2007 by ASME
Experimental and numerical investigations on fast catamarans interference effects
No full textExperimental and numerical analysis of the interference effect for a fast catamaran is carried out. This work presents the status of an ongoing NICOP project, the focus is on the effect of the separation distance between the demihull on the performances as well as on the interference. To this aim, experiments and numerical simulations are performed for five different separation lengths (and for the monohull configuration) and for a wide range of Froude number (from 0.2 to 0.8). © 2010 Publishing House for Journal of Hydrodynamics
Analysis of the interference effects for high-speed catamarans by model tests and numerical simulations
No full textThis paper presents the results of a large experimental and numerical campaign aimed to the analysis of the interference effect for a fast catamaran. Several separation distances are considered; data for resistance, sinkage and trim are collected by towing tank experiments for Froude number ranging from 0.2 to 0.8. Monohull tests are also carried out, the analysis of the interference and its dependency on the separation length being the main objective of the paper. Resistance coefficient curves reveal the presence of two humps, the second one strongly depending on the separation length; high interference is observed in correspondence of the second hump. It is found that the narrower is the configuration, the higher is the interference and the speed at which this maximum occurs. To gain a deeper insight into these behaviors, a complementary analysis, in terms of wave field, surface pressure and velocity field is carried out by an in-house unsteady RANS solver. Verification of numerical results is provided, together with validation, which is made by the comparison with both present and other experimental data. Agreement in terms of resistance coefficient is rather good, comparison error being always smaller than 2.2%. © 2011 Elsevier Ltd. All rights reserved
Numerical study of confined water effects on self-propelled submarine in steady manoeuvres
No full textThis paper deals with the analysis of confined water effects on the manoeuvring capabilities of a submarine. The analysis is carried out by using numerical simulations based on the Reynolds Averaged Navier Stokes equations of a submarine moving with constant speed on a straight path at zero and nonzero drift/pitch angles, in open water, close to the bottom, and close to the free-surface conditions. The features of the flow around the submarine are described in terms of velocity and pressure fields; the computed force and moment coefficients are presented and compared with experimental data collected at INSEAN. Copyright © by The International Society of Offshore and Polar Engineers
Numerical simulations of viscous flow around a a fully appended hull with enforced motion
No full textNumerical simulations of the flow past the KVLCC2 MOERI tanker with prescribed motion are carried out. The ship model is considered in fully appended configuration, i.e. the rudder and the propeller are included. The motions considered are the straight ahead and the pure sway manoeuvres. The analysis of the flow field is carried out by the numerical solution of the unsteady RANS equations; to this aim, the solver developed at INSEAN has been employed. In this work, free surface effects are neglected, whereas the presence of the propeller is taken into account by a suitable non-iterative model. Body motion is handled by means of an in-house dynamical overlapping grid approach. An analysis of the flow field, in terms of pressure distribution, axial velocity and vorticity field is carried out for the straight ahead manoeuvre both in the unpropelled and propelled conditions, as well as in the propelled pure sway manoeuvre. The effects of the operating propeller and the unsteady motion of the hull on the vortical structures are analyzed
- …
