Adrian Constantinescu

Comparaison de différentes approches pour la simulation numérique d'impacts hydrodynamiques

Le but de ce travail est de comparer différentes méthodes numériques appliquées à la simulation d’impacts hydrodynamiques. Trois modèles ont été considérés : (i) un modèle éléments finis basé sur la théorie de Wagner, (ii) un modèle éléments finis basé sur un formalisme Arbitraire Lagrange-Euler (ALE), (iii) un modèle volumes finis basé sur un formalisme eulérien multiphasique et la technique « Volume of Fluid ». Les capacités de ces différentes approches à résoudre des problèmes d’impact hydrodynamique sont étudiées au travers de comparaison avec des résultats de référence de la littérature et avec des resultants expérimentaux.

Wedge-Shaped Shell Structure Impacting a Water Surface

This paper presents a study of fluid structure interaction during the impact of a ship on a water surface. The analysis combines the assumption of small displacements for the ideal fluid and the solid with an asymptotic formulation for accurate pressure evaluation on the wet surface boundary. A fluid-heat analogy is used to obtain the regular displacement, velocity and pressure fields in the fluid domain with ABAQUS/Standard finite element code. PYTHON and FORTRAN languages are also employed to connect fluid and structure data. Two methods are developed. The first method employs a weak fluid-structure coupling. The average discrepancy between our numerical results and experiments was 22% for the peak pressures for conical shell structures. The wet surface velocity was well predicted. The second method (implicit fluid-structure coupling using a convergence criterion) is more accurate. Recent results with an improved, numerical hydrodynamic model based on CFD are also presented.Copyright

Finite Element Simulations and Experimental Investigations of Simple 2-D Geometries in Slamming

This paper presents a numerical and experimental study of fluid structure interaction during the impact of a solid body on a water surface. The main request is the modeling of the slamming forces acting on the ship structure in severe sea conditions. The numerical work uses the finite element modeling of a structure impact with free water surface. The first analysis use the commercial finite element code ABAQUS/Standard and combines the assumption of small displacements for the ideal fluid and the solid with an asymptotic formulation for accurate pressure evaluation on the boundary of the wet surface. For deformable strickers, two methods are developed. The first method employs a weak fluid-structure coupling. The second method, more accurate, uses an implicit fluid-structure coupling using a convergence criterion. The second analysis is represented by the simulations of slamming with ABAQUS/Explicit. The simulation uses a viscous, compressible fluid and a soft-exponential law to manage the contact between fluid and solid. The results in term of pressure and total effort applied to the rigid structure are in good agreement with first numerical results and especially with the FLUENT CFD. In order to validate the numerical methods, slamming experimental tests were carried out with a new hydraulic shock press at the ENSIETA laboratory.Copyright