This report refers to the work that has be done within the Job Order 08CT17 Phase-4: "Numerical simulation and optimization of lowercase (new geometry)". The work deals with the numerical study of a lowercase, including a parametric optimization. The work is divided into two phases: 1) numerical study of the basic geometry; 2) numerical study of a modified version and comparison with the basic geometry. Numerical analysis has been performed on a new lowercase geometry provided by FluidTechno Co., Ltd. The geometry has been provided in form of CAD-IGES file. The parametric optimization has been performed by changes suggested by the customer. As usual, the geometry has been elaborated by CNR-INM personnel in order to make it suitable for the generation of the computational mesh. In particular, some surfaces have been reworked to increase the level of accuracy and to guarantee a suitable level of smoothness. New geometry has been also generated by INM personnel. Simulations have been carried out at the same model scale as for the previous lowercases analyzed by numerical simulations and tested in the basin; the geometry provided has been considered at model scale (λ = 2.50); same model scale of the model studied in Phase 2 (Broglia and Dubbioso (2016c))) and in Phase 3 (Broglia and Dubbioso (2016b)). Propeller effects are not considered, whereas free surface effects are taken into considerations. Computations have been performed at one speed selected by the customer, namely: 7m/s. Results are reported in terms of total resistance and individual contributions from different part of the lowercase. Example of flow field analysis in terms of surface pressure, velocity fields and wave pattern. Data will be provided in electronic form, anyhow any other analysis can be performed based on the customer's requirements. Verification (i.e. the analysis of the convergence properties and the estimation of the numerical uncertainty) has been assessed following a widespread adopted procedure. Validation (i.e. the estimation of the comparison error) cannot be performed, being experimental test not available. Simulations have been carried out on wall resolved grids (i.e. no wall functions have been used), which count for about 14.0M of control volumes for both the original and modified geometries (for only half of the geometry). Overlapping grid approach have been used to accurately represent the geometry of the lowercase and to increase the resolution in regions where strong gradients are expected, as well as around the free-surface. Numerical computations have been carried out by means of the Ï?navis solver, which is a general purpose unsteady Reynolds averaged Navier-Stokes (uRaNS) solver developed at CNR-INM. For the sake of completeness, the theoretical model adopted at CNR-INM is briefly described in the following, a detailed discussion have been reported in the phase one report (Broglia and Dubbioso (2016a)).
CFD analysis of lowercase. Phase four: Simulation of lowercase, new geometry and optimization
Riccardo Broglia
2019
Abstract
This report refers to the work that has be done within the Job Order 08CT17 Phase-4: "Numerical simulation and optimization of lowercase (new geometry)". The work deals with the numerical study of a lowercase, including a parametric optimization. The work is divided into two phases: 1) numerical study of the basic geometry; 2) numerical study of a modified version and comparison with the basic geometry. Numerical analysis has been performed on a new lowercase geometry provided by FluidTechno Co., Ltd. The geometry has been provided in form of CAD-IGES file. The parametric optimization has been performed by changes suggested by the customer. As usual, the geometry has been elaborated by CNR-INM personnel in order to make it suitable for the generation of the computational mesh. In particular, some surfaces have been reworked to increase the level of accuracy and to guarantee a suitable level of smoothness. New geometry has been also generated by INM personnel. Simulations have been carried out at the same model scale as for the previous lowercases analyzed by numerical simulations and tested in the basin; the geometry provided has been considered at model scale (λ = 2.50); same model scale of the model studied in Phase 2 (Broglia and Dubbioso (2016c))) and in Phase 3 (Broglia and Dubbioso (2016b)). Propeller effects are not considered, whereas free surface effects are taken into considerations. Computations have been performed at one speed selected by the customer, namely: 7m/s. Results are reported in terms of total resistance and individual contributions from different part of the lowercase. Example of flow field analysis in terms of surface pressure, velocity fields and wave pattern. Data will be provided in electronic form, anyhow any other analysis can be performed based on the customer's requirements. Verification (i.e. the analysis of the convergence properties and the estimation of the numerical uncertainty) has been assessed following a widespread adopted procedure. Validation (i.e. the estimation of the comparison error) cannot be performed, being experimental test not available. Simulations have been carried out on wall resolved grids (i.e. no wall functions have been used), which count for about 14.0M of control volumes for both the original and modified geometries (for only half of the geometry). Overlapping grid approach have been used to accurately represent the geometry of the lowercase and to increase the resolution in regions where strong gradients are expected, as well as around the free-surface. Numerical computations have been carried out by means of the Ï?navis solver, which is a general purpose unsteady Reynolds averaged Navier-Stokes (uRaNS) solver developed at CNR-INM. For the sake of completeness, the theoretical model adopted at CNR-INM is briefly described in the following, a detailed discussion have been reported in the phase one report (Broglia and Dubbioso (2016a)).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
