FEATURES OF SOLVER –MP NS

fluidyn– MPÔ 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

1. Core Hydrodynamic Solver

 NS has three solvers:

  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.  

1.1 Convection Schemes

The convection schemes available in different solvers are as follows:

1.2 Time-Differencing Schemes

1.3 Pressure Computation

  Non-orthogonal terms are accounted while solving for pressure

1.4 Linear Equation Solvers

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

1.5 Thermodynamic Models

  The thermodynamic models offered are:

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

1.7 Gravity Models

  Following gravity models are available in all solvers:

-         Full gravity Model

-         Buoyancy Model

-         Boussinesq Model

2 Additional Modeling Features

2.1 Turbulence

The following turbulence models are available in NS:

-         Standard k-e with compressibility corretcions

-         Re-normalization group (RNG) k-e

-         Chen-Kim k-e

-         Mixing length models, Baldwin-Lomax, Cebeci-Smith

-         Large eddy simulation using the Smagorinsky’s Sub-Grid Scale model (SGS)

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

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.

2.3 Moving Mesh

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

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

2.5 Thermal Radiation

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

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)

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 method

o       Monte-Carlo sampling for particle injection/turbulent dispersion

o       Polydisperse particle distributions:

-         c2 distribution

-         Rosin-Rammler

-         Upper Limit Log Normal (ULLN)

o       Selection of models for particle momentum exchange with carrier phase

o       Droplet evaporation with heating

o       Turbulent dispersion

o       Droplet breakup/collision models

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.

2.9 Magneto Hydrodynamics (MHD)

  The NT module can solve MHD flows with constant or varying magnetic field. It has both the electric potential method and magnetic induction method. It can also simulate, jointly with the FE solver, a jump in electric potential/magnetic fields.

2.10 Porous Media

  All the modules can take into account the volume porosity. The NT module can model flows and pollutant dispersion described by Darcy law using direction dependent permeabilities. MP as a whole can model heat transfer in porous media using local thermal non-equilibrium model.  

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

·        Coefficient of drag in Lagrangian particle tracking

·        Dispersed phase injection

·        Dispersed phase particle size

·        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.)