Annexe ASPECIFICATIONS OF FLUIDYN-MP (with modules NS, CHT, FSI & CAF).

1. SOFTWARE Fluidyn - CAE for Geometry, Problem Data Input & Results analysis.

Fluidyn – MP for 3D Multi-physics Simulation with following modules

1. CADGEN for structured and unstructured mesh generation & optimizer2. MP NS for 3D fluid dynamics analysis3. MP CHT for conjugate structure/ fluids heat transfer4. MP FSI for fluid structure interaction5. MP CAF for coupled fluid-acoustics analysis

2. Accepted HARDWAREThe software is available on following platforms:

o UNIX/Linux OS (32-bit and 64-bit) on SUN, DEC ALPHA, SGI, IBM, HP, and other workstations

o Windows (32-bit)/Linux OS (32-bit and 64-bit) on Intel/AMD PC’s

The software is available in both single-user (single-license) and multi-user (floating license) mode.

The code is also available in the parallelized version for use with multi-processor systems (Linux/UNIX).

3. Fluidyn CAE: Geometry, Problem Definition, Result Analysis

Fluidyn - CAE is an integrated CAD platform for 3D geometric modelling besides Pre & Post processing. It is primarily oriented for a design user though it is also used by CFD engineers.

Fluidyn-CAE serves as a platform for data and results exchange between a design engineer and a modelling engineer. Design engineer can use it for defining all the data required for an efficient modelling irrespective of the modelling aspects such as mesh, physical models (turbulence, equation of state etc..). Besides importing geometry from other CAD software, CAE can generate a CAD model or modify, clean & repair imported models.

In the same way results obtained from simulation in Fluidyn-MP or other such software can be visualized on the initial geometry.

3.1 Geometry Creation

Fluidyn- CAE can be used to create a wide variety of geometry (surfaces and volumes).

The code can also import files in IGES/DXF/STL format with in-built checks for topological validity, closed shell Consistent Orientation etc. High End features for modeling and repairing the objects are present to ensure that user can prepare a reasonable model with minimum effort.

It exports data in Fluidyn CAD’s file format (*.F3D). A macro recording is also done to avoid repetitions or to do necessary corrections. 3.2 Input Data pre-processing

Material properties, boundary & initial conditions, loads etc are assigned directly on geometry model without any mesh generation a priori. Thus any mesh modifications during study does not require redefinition of input data besides optimization of mesh and dimensions can be integrated in the simulation algorithm.

The geometry model can be broken up in surfaces or volumes to define input data and sewed together again. Properties and initial conditions are either defined as a pointer to a data base or full defined.

3.4 Result Analysis

A fully interactive postprocessor allows a design engineer to visualize his results without having the solver software.

4 Fluidyn MP - CADGEN (Mesh Generator)

The mesh generator, CADGEN, is integrated in Fluidyn-MP to allow dynamic mesh modifications during simulations.

Designed to mesh Complex Geometries. User-friendly. Creates multi-block structured mesh non conformal mesh or Creates unstructured (using frontal Delaunay Triangulation) mesh in 2D or 3D Capable of generating non-uniform mesh.

The Mesh Generator Allows

Refinement for shocks or turbulent boundary layer flows. Moving mesh for free surface flows or solid walls.

Features of Mesh Generator

Integrated in Fluidyn MP user interface. Supports Cartesian, cylindrical, spherical, toroidal and rotating co-ordinate

systems. Generates unstructured, non-orthogonal grids to fit the boundary. Supports multi-block meshes. Supports command line interface and script file for parametric generation of

geometry and mesh Can import mesh from IDEAS, GAMBIT formats Fast and user-friendly generation of mesh on primitive geometries

The software

Can create Hexahedral, tetrahedral, triangular prisms and other common polyhedral cells.

Has many tools for mesh improvement and refinement Supports many mesh quality parameters which may be visualised graphically. Supports multiple rotation zones between adjacent meshes. Displays grids generated in wire mesh and hidden conditions. Displays mesh in shaded format. Has zooming and orientation facilities to visualize the geometry and mesh.

5 FLUIDYN – MP NS CFD SOLVER

Fluidyn – MP NS is a general purpose Computational Fluid Dynamics software package to simulate fluid flow in and around complex geometrical configurations. It can simulate transient/steady incompressible/compressible flows on 3D unstructured meshes with heat transfer, radiation, turbulence, chemical reactions, multi-phases with free surfaces, droplets, etc.

a) Analyzes incompressible flows and compressible at subsonic, transonic and supersonic speeds (with the shock-capturing).

b) Analyzes steady and transient flows.c) Analyzes viscous or inviscid flows.d) Finite volume scheme based on unstructured/multi-block mesh.e) Supports the following mesh features:

- unstructured/multi-block mesh- hexahedral, tetrahedral, prismatic and other commonly used general

polyhedral mesh- non-conformal mesh blocks- moving/deforming meshes- sliding meshes for moving/rotating components

4.1 Core Hydrodynamic Solver

NS has three solvers:

Module DescriptionTVD Density-based fully coupled explicit/implicit time-marching method

for unstructured mesh.MB Pressure-based semi-implicit time-marching method for multi-block

meshNT Pressure-based fully-implicit segregated method for unstructured

mesh.

All solvers use finite volume methods based on Cartesian velocity components. While TVD and NT solvers use collocated method, MB uses cell-vertex scheme. The NT code, though written for 3D flows, automatically determines if the problem is 2D and if so, solves only the relevant velocity components.

The TVD code uses the coupled method to solve the governing equations. MB uses a semi-coupled strategy while NT uses a segregated method.

All the solvers support flow through porous media.

4.1.1 Convection Schemes

The convection schemes available in different solvers are as follows:

TVD MB NTVan Leer flux-vector splitting

Weighted partial donor cell scheme

Central difference

Roe flux-difference splitting Quasi-second order upwind scheme

Gamma differencing (2nd order)

AUSM Flux limiter (TVD-) schemes (3rd

order):- van Leer smooth Limiter- van Albada Limiter- MinMod Limiter- Super-Bee Limiter- Linear-kappa scheme- SMART scheme- UMIST Limiter- van Leer MUSCL Limiter- ISNaS Limiter

HLLCPreconditioned Riemann solvers for incompressible/low-speed flows

4.1.2 Time-Differencing Schemes

TVD MB NTMulti-stage Runge-Kutta explicit

Euler implicit (1st order) Euler implicit (1st order)

Jacobi implicit 3 time-level scheme (2nd order)

4.1.3 Pressure Computation

TVD MB NTWeiss-Smith preconditioning SIMPLE SIMPLEJacobi implicit SIMPLEC

PISO

Non-orthogonal terms are accounted while solving for pressure.

4.1.4 Linear Equation Solvers

The linear equation solvers used to solve the implicit difference equations are:

TVD MB NTPoint-Jacobi Conjugate Residual SIP (for structured mesh)

ICCG for symmetric matricesCGSTAB/BiCGSTABGMRES

4.1.5 Thermodynamic Models

The thermodynamic models offered are:

TVD MB NTIncompressible density variation with

temperaturedensity variation with temperature

density variation with temperature

Compressible

Perfect gas Perfect gas Perfect gasIdeal gas Ideal gas Ideal gasIdeal mixture Ideal mixture Ideal mixtureEquilibrium airJWL (high-explosives)polynomialMie-GruneisanTwo-phase expansion EOS for vapor-liquid equilibria

4.1.6 Boundary Conditions

All solvers support the following boundary conditions:

- Prescribed inflow- Prescribed outflow- Specified pressure- Impermeable wall and baffle surfaces- Cyclic (periodic) boundaries- Symmetry plane- Specified stagnation condition- Free stream- Transmit condition- Characteristic based Riemann conditions

4.1.7 Gravity Models

Following gravity models are available in all solvers:

- Full gravity Model- Buoyancy Model- Boussinesq Model

4.2 Additional Modeling Features

4.2.1 Turbulence

The following turbulence models are available in NS:

- Standard k- with compressibility corretcions- Re-normalization group (RNG) k-- Chen-Kim k-- Mixing length models, Baldwin-Lomax, Cebeci-Smith- Large eddy simulation using the Smagorinsky’s Sub-Grid Scale model

(SGS)- SST- V2F for jet impingement- PANS

Non-equilibrium law-of-wall condition is used at solid walls.

4.2.2 Non-Matching Mesh

The TVD and NT solvers can handle non-matching or non-conformal mesh interfaces. This is useful for sliding meshes, for fine grid embedding, and also for component-by-component meshing.

4.2.3 Moving Mesh

All the solvers can handle moving meshes. User has to code (in Fortran) the velocities of grid node movement.

4.2.4 Reactive Flows

The code can handle chemically reactive flows with reaction rates being computed from one of the following 4 models:

Arrhenius model Eddy-dissipation concept of Magnussen Minimum of the above two Combined Time Scale Model

4.2.5 Thermal Radiation

The NT module has the P1-aproximation model for modeling thermal radiation transport through participating media.

4.2.6 Free-Surface Flows

The MB and NT modules have the Volume of Fluid (VOF) for simulating interpenetrating two-phase flows. Continuum Surface Force (CSF) model is used for surface tension forces. Three additional schemes are offered for advecting VOF:

Inter-Gamma Differencing High Resolution Interface Capturing (HRIC) Compressive Interface Capturing Scheme for Arbitrary Meshes (CICSAM)

4.2.7 Dispersed Flow

The MB and NT modules have the Lagrangian particle tracking method for simulating dispersed flows. The salient features of this method are:

o Lagrangian particle tracking methodo Monte-Carlo sampling for particle injection/turbulent dispersiono Polydisperse particle distributions:

- 2 distribution- Rosin-Rammler- Upper Limit Log Normal (ULLN)

o Selection of models for particle momentum exchange with carrier phase

o Droplet evaporation with heatingo Turbulent dispersiono Droplet breakup/collision models

4.2.8 Multiphase Flows

The NT module has the Eulerian multiphase flow model for simulating multiple fluid-streams in different physical states coupled to each other. It uses a fully-coupled solution of multi-phase flow equations along with a single combined pressure field. The interfacial area transport equation is solved to compute local interface areas needed for evaluation of phase exchange terms. It also has automatic regime mapping and activation of phenomenological models for phase exchange terms.

4.3 User Coding

User coding is available for:

Thermodynamic equation of state Boundary conditions Initial conditions Viscosity, conductivity, and other fluid transport properties Momentum, enthalpy, turbulence, chemical and other source terms Turbulence model Convective scheme Diffusion scheme Chemical reaction rate Radiation properties Moving grid Solution of linear equations Time step for transient calculations Output and post-processing

For user programming, all the geometrical and solver data can be accessed through common blocks and subroutines.

Note: Fortran compiler required for user compilation.

5 Conjugate Heat Transfer module - MP CHT

Fluidyn-MP CHT can perform convection, conduction and radiation in a conjugate heat transfer problem involving a fluid and a solid. It can also model the deformation of the solid due to heating. The fluid region is meshed with 3D elements (finite volume formulation) and all the features of the Fluidyn – MP NS code are available in the fluid domain. The structural region of interest is meshed with 1D, 2D or 3D finite elements and this allows analysis of heat conduction in solids due to the heat transfer from or to the surrounding fluid for complex geometries.

Convection and radiation are treated with one of the Finite Volume schemes chosen according to the flow type: compressible, incompressible, reactive, etc. Dynamically changing convection boundary condition is considered implicitly at the Fluid-Structure interface for the structure.

Thermal radiation is modeled for transparent media. 3D view factors are automatically calculated while considering the shadow effect of all the intermediate obstacles.

5.1 Method of Modeling in Fluidyn-MP CHT

The architecture of the software and its mesh generator (Fluidyn-CAD/GEN) is organized in such a way that, they not only allow the creation of geometries and 3D grids but also to accept IGES files or input data files coming from other software.

An easy-to-use graphical user interface allows the user to choose the appropriate numerical scheme and mathematical algorithm among various available CFD solvers in the Fluidyn-MP NS. The code also allows the users to introduce their own equations of state or boundary conditions through externally compiled software modules. Thus a user-developed software in Finite Element or Finite Volume can also be coupled if necessary.

As every simulation exercise carries many assumptions, the user can verify their validity by following the calculation graphically while the simulation is in progress. As many as 30 windows can be opened on the monitor screen and various physical quantities can be followed simultaneously either as contours, trace plots or vectors.

The user can modify certain parameters of the solver as it is running; they include time step, relaxation factors, boundary conditions, result file writing controls, etc.

5.1.1 The Fluid Solver

The fluid solver is same as that described above under the name Fluidyn-MP NS.

5.1.2 The Thermal Solver

The Thermal Solver is a Finite Element code for thermal transient analysis. The following types of analysis are possible:

Explicit Transient Implicit Transient Steady state

The element library includes 2-noded beam, 3-noded shell element, 4-noded tetrahedral, 5-noded pyramid, 6-noded wedge, and 8-noded hexahedral elements. The material properties may be constant or temperature dependent, isotropic or orthotropic. For solution of problems of large size, out-of-core technique is employed to overcome memory constraint for matrix storage.

5.1.3 Boundary Conditions on the structure for Thermal Analysis (Steady or Unsteady)

The following thermal boundary conditions can be applied on the solids:

Specified Nodal Temperature Heat flux across boundary faces Element heat generation Nodal heat generation Convection across boundary faces Radiation across boundary faces or ambient Multipoint Temperature Constraint

5.2 Post-Processing

The results can be saved while the calculation is running either at regular, pre-specified intervals of simulation time or on-the-fly, whenever the user wishes. These results can be visualized graphically using the independent Graphical User Interface of Fluidyn-MP CHT even while the calculation is proceeding. The graphical results may also be presented as slide show with user comments. While working on transient phenomena, the software can also directly produce animation files. It is also possible to work on these result files further by applying mathematical functions.

6 Fluid-Structure Interaction (FSI) module MP FSI

High-speed interaction between two structures or a structure and fluid requires simultaneous modeling of large deformations of structures and shock propagation in fluids.

Finite Volume better manages modeling varying flow regime and boundary condition in fluids, because numerical distortion related to Shape Function used in finite element techniques do not exist. On the other hand modeling of structural deformations can be done best by Finite Elements because 3D complexities are difficult to model by Finite Volume e.g. thin plates, beams etc.

Fluidyn-MP FSI is a unique, state of the art software that involves simultaneous utilization of both Finite Volume and Finite Element Techniques in their areas of strength. First, Fluidyn-MP FSI fluid solver is invoked to march to the first fluid time step (by finite Volume). The stress solver drives the structure to a new configuration with new velocities using the thermal and mechanical loading of the fluid (by Finite Element). The fluid is then assumed to take up a new position that brings it in contact with the new structural position and to have a continuous normal component of the velocities. This is achieved by re-meshing the fluid domain to conform to the current configuration of the structure. The new distribution of fluid nodes leads to a new pressure field in the fluid. This process is repeated till the simulation time is reached.

6.1 Auto-adaptative Remeshing in Fluidyn-MP FSI

In the case of Fluid-Structure interaction, the structure undergoes deformation due to pressure/temperature from the fluid. Consequently, the Fluid boundary at the Fluid-Structure interface is displaced.

The objective of Auto-Adaptive re-meshing is to modify the fluid mesh so as to reduce the distortion and improve the mesh size and aspect ratio of the mesh, which has a direct bearing on the time step.

6.2 THE FLUID SOLVER

The Fluid Solver is same as that described under Fluidyn-MP NS heading.

6.3 THE STRESS SOLVER

The Stress Solver is a Finite Element code for nonlinear transient analysis of structures besides static and eigenanalysis. The following types of analysis are available:

1. Explicit Transient2. Implicit Transient3. Static Analysis4. Eigen-value and modal analysis

Under Explicit Transient analysis, both geometric and material non-linearity may be handled. Material non-linearity includes following features:

1. Elastic2. Perfectly Plastic3. Linearly Plastic 4. Piecewise-Linear Stress-Strain Relationship.

Convective coordinate approach is used for Beam and Shell Elements.Element types include 2-noded beam, spring and cable elements, 3-noded shell element, 4-noded tetrahedral, 6-noded wedge element and 8-noded hexahedron. Large deformation of membrane can be handled using membrane elements in explicit analysis. Implicit and static analysis use efficient solution techniques for solution of matrix (stored in skyline form) equations.

Eigenanalysis uses subspace iteration method for extracting eigenvalues and eigenvectors of the system. Modal analysis features include modal displacement and modal acceleration methods.

The boundary conditions (steady or time-dependent) include:

1. Nodal Force2. Nodal Displacement 3. Pressure 4. Body Force 5. Nodal Temperature6. Plug Rupture7. Crack propagation8. Multi-point displacement constraint9. Added mass10. Nodal Acceleration

6.4 Sloshing Analysis

The Sloshing module can be used to evaluate sloshing modes of a fluid in a rigid container. This module solves the Helmhotz equation for an inviscid fluid using finite elements. The different modes signify free surface shapes of the fluid.

7. Acoustic Analysis module Fluidyn – MP CAF

Fluidyn – MP CAF is used to calculate internal flows with eigenmode calculation of internal space. Fluid Speed and temperature can also influence eigenmodes.

This software can simultaneously model fluid and acoustic flows. It can also perform vibratory calculations of structures if required.

The software can also be used for the propagation of acoustic waves in a non-homogeneous medium.

The flow calculations are run under the same conditions as in the software Fluidyn–MP NS.

Fluidyn – MP CAF solves the Helmholtz equation (wave propagation) with the finite elements method. It helps in predicting noise levels due to Single / Multiple point or line types of noise sources.

7.1 Acoustics Models

The oscillation sources that can be treated in Fluidyn – MP CAF are listed below:

a) Flow Sources :

- unstable laminar flow such as the Coanda effect- large fluctuations in flow field (turbulent)- unstable boundary layer: mostly critical flows

b) Acoustic Sources :

- mass explosion such as bubble formation and explosion (density discontinued)- large increase in temperature such as in chemical reactions

Propagation of oscillations occurs through:

a) Flow:

- a large part of energy by flow velocity convection - a part of energy by diffusion (acoustics)

b) Acoustics: mainly by sound velocity diffusion

7.2 Numerical Features

Fluidyn – MP CAF solves the Helmholtz equation using the Finite Elements method. The 2D or 3D finite element model can be reduced by using a succession of acoustic barriers for far field simulation. In cases, where the wind velocity should be considered, the Helmholtz equation is accordingly modified and solved iteratively.

The same mesh can be used for both fluid and acoustic flows

7.3 Numerical Solver

As mentioned before, Fluidyn – MP CAF solves the Helmholtz equations using the Finite Elements method. The solver uses either the available RAM memory or the hard disk memory. In cases, where the flow speed is to be considered, the resulting dissymmetric equations are solved iteratively. A recent innovation includes the introduction of a series of sound barriers at the domain boundaries to solve far field problems without increasing the computational time.