If You are interested in problems related to the influence of a continuous medium (fluid, melt, air, gas) on the surface of structure (vessel wall, the surface of turbine blades, etc.), as well as related issues of strength, this stuff is for You!

MODELING PROBLEMS OF INTERACTION "FLUID-STRUCTURE" USING THE PACKAGES STAR-CD AND LS-DYNA

Currently, the development of advanced systems of engineering analysis, development of new numerical algorithms, increasing the power of computer technology facilitate the use of mathematical modeling of physical processes in different industries and science. Particularly relevant is decision of interdisciplinary problems (problems of multiphysics), where you need to joint modeling of nonstationary aero- and hydrodynamic processes and dynamics of constructions. Such tasks require the simultaneous simulation of various physical phenomena, taking into account their mutual influence, in particular Fluid Structure Interaction (FSI).

In this paper, an approach to modeling FSI problems is considered based on the bilateral cooperation between the strength package LS-DYNA and aerohydrodynamic package STAR-CD (Fig.1).

Fig. 1. Fluid Structure Interaction (FSI) problem

Under the proposed approach the deformation of structure is simulated with the help of software package LS-DYNA during the entire duration of the loading derived from STAR-CD. It is assumed that the displacement of nodes of finite element mesh are negligible, i.e. not lead to a change in the flow domain (finite volume mesh) in the STAR-CD.

Related calculations have been made possible thanks to the developed converter, which provides an output file loads from the STAR-CD with the results of the calculation and conversion of data into a format of LS-DYNA, for the formation of the boundary conditions.

The proposed approach provides a relatively simple mechanism for transfer of physical quantities from one grid to another and allows for different variants of the strength analysis with a constant set of aero- and hydrodynamic characteristics.

During execution of the work following tasks were solved consistently:

– steady-state problem with using a stationary mesh: calculation of loads on the walls of Г-tube (Fig.2b), resulting in steady viscous fluid flow (Fig.2a);

a)b)

Fig. 2. Pressure field in a section of a hydrodynamic flow (a); stress distribution (by Mises) in the tube (b)

– transient problem with using a stationary mesh: stress analysis on the walls of the Laval nozzle (Fig.3b) observed in a supersonic flow of compressed air during the formation of a shock wave (Fig.3a);

a)b)

Fig. 3. Supersonic outflow flux and the formation of a shock wave (a); stress distribution (by Mises) in the model of nozzle (b)

– transient problem with using a moving (rotating) mesh: calculation of strength characteristics of the rotary mixer (Fig.4b) based on the solution of unsteady hydrodynamic problem (Fig.4a).

a) b)

Fig. 4. Velocity field in a section of the flow inside the mixer (a); stress distribution (by Mises) in the rotor part of the mixer (b)