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Introductory FLUENT Notes FLUENT v6.0 Jan 2002

Introduction to CFD Analysis

2-1

© Fluent Inc. 12/26/2001

Fluent User Services Center www.fluentusers.com

Introductory FLUENT Notes FLUENT v6.0 Jan 2002

What is CFD?
Computational Fluid Dynamics (CFD) is the science of predicting fluid flow, heat transfer, mass transfer, chemical reactions, and related phenomena by solving mathematical equations that represent physical laws, using a numerical process. Conservation of mass, momentum, energy, species, ...

The result of CFD analyses is relevant engineering data:
conceptual studies of new designs detailed product development troubleshooting redesign

CFD analysis complements testing and experimentation.
Reduces the total effort required in the laboratory.

2-2

© Fluent Inc. 12/26/2001

Fluent User Services Center www.fluentusers.com

Introductory FLUENT Notes FLUENT v6.0 Jan 2002

How does CFD work?
FLUENT solvers are based on the

finite volume method.
Domain is discretized into a control volume finite set of control volumes or cells. General conservation (transport) equation for mass, momentum, energy, etc., ∂ ∫ ρφdV + ∫ ρφV ⋅ dA = ∫ Γ∇φ ⋅ dA + V Sφ dV ∫ ∂t V A A unsteady convection diffusion generation

Fluid region of pipe flow discretized into finite set of control volumes (mesh).

are discretized into algebraic equations. All equations are solved to render flow field. 2-3

Eqn. continuity x-mom. y-mom. energy

φ
1 u v h

© Fluent Inc. 12/26/2001

Fluent User Services Center www.fluentusers.com

Introductory FLUENT Notes FLUENT v6.0 Jan 2002

CFD Modeling Overview
Solver Pre-Processing Solid Modeler Mesh Generator Equations solved on mesh Transport Equations mass
species mass fraction phasic volume fraction

Physical Models
Turbulence Combustion Radiation Multiphase Phase Change Moving Zones Moving Mesh

momentum energy

Solver Settings

Equation of State Supporting Physical Models

Post-Processing

Material Properties Boundary Conditions Initial Conditions

2-4

© Fluent Inc. 12/26/2001

Fluent User Services Center www.fluentusers.com

Introductory FLUENT Notes FLUENT v6.0 Jan 2002

CFD Analysis: Basic Steps
Problem Identification and Pre-Processing 1. Define your modeling goals. 2. Identify the domain you will model. 3. Design and create the grid. Solver Execution 4. Set up the numerical model. 5. Compute and monitor the solution. Post-Processing 6. Examine the results. 7. Consider revisions to the model.

2-5

© Fluent Inc. 12/26/2001

Fluent User Services Center www.fluentusers.com

Introductory FLUENT Notes FLUENT v6.0 Jan 2002

Define Your Modeling Goals
Problem Identification and Pre-Processing 1. Define your modeling goals. 2. Identify the domain you will model. 3. Design and create the grid.

What results are you looking for, and how will they be used? What are your modeling options?
What physical models will need to be included in your analysis? What simplifying assumptions do you have to make? What simplifying assumptions can you make? Do you require a unique modeling capability? User-defined functions (written in C) in FLUENT 6 User-defined subroutines (written in FORTRAN) in FLUENT 4.5

What degree of accuracy is required? How quickly do you need the results? 2-6 © Fluent Inc. 12/26/2001

Fluent User Services Center www.fluentusers.com

Introductory FLUENT Notes FLUENT v6.0 Jan 2002

Identify the Domain You Will Model
Problem Identification and Pre-Processing 1. Define your modeling goals. 2. Identify the domain you will model. 3. Design and create the grid

Gas Cyclone Riser

How will you isolate a piece of the complete physical system? Where will the computational domain begin and end? Do you have boundary condition information at these boundaries? Can the boundary condition types accommodate that information? Can you extend the domain to a point...
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