CFD Crash Course

Thursday, April 12, 2012

I got a clear short course on CFD. It’s from Professor Dmitri Kuzmin from Dortmund University of Technology.

His research interest is in  FEM for Computational Fluid Dynamics, including:

• Implicit high-resolution schemes
• Convection-dominated transport
• Navier-Stokes and Euler equations
• Multiphase flows (gas-liquid)
• Free and moving boundaries

There’s 11 series of lecture in pdf file

Lecture 1

consist  introduction to CFD, what is fluid flow, what is CFD, example of CFD application, Comparison on experiment and Simulation, Fluid Characteristics, How CFD make prediction, process in CFD Analysis, and a short explanation on every process.

Lecture 2

especially explaining about CFD Equation, Getting Started on CFD Notation, tensor, vector, gauss theorem divergence, lagrange, energy, momentum and mass conservation equation etc.

Lecture 3

continuing lecture 2 on equation, but now advanced to compressible and incompressible, and meshing choice. This is important to understand to choose the right and effective meshing to use in your simulation.

Lecture 4

Introduction to finite difference methods in solving equation. There’s calculation example to solve 1D, and 2D problems

Lecture 5

Explanation on Finite Volume Method and it’s variation. You must understand this methods difference when using FLUENT to choose appropriate methods for your simulation. Fluent use Finite Volume method.

Lecture 6

Explaining Finite Element Method

 

Lecture 7

Continuing lecture 6 on Finite element method covering galerkin till strategy to save sparse matrix (matrix with many zeros.)

 

Lecture 8

Strategy to solve unsteady equation with time-stepping, implicit and explicit (FLUENT use this too), predictor corrector etc.

 

Lecture 9

Numerical methods had properties which are, stability, consistency, convergence, conservation and boundedness. It’s all explained in this lecture.

 

Lecture 10

analysis of numerical dissipation and dispersion

 

Lecture 11

operator splitting technique.

What Is CFD – Part 2

What is The Step in Solving CFD

Basically, there’s 3 step in solving CFD.

1. Preprocessing

2. Solver

3. Post Processing

Preprocessing step includes:

• The geometry (physical bounds) of the problem is defined (Problem statement information about flow)
• Mathematical Model IBVP = PDE + IC + BC
• The volume occupied by the fluid is divided into discrete cells (the mesh). The mesh may be uniform or non uniform.
• The physical modeling is defined – for example, the equations of motions + enthalpy + radiation + species conservation
• Boundary conditions are defined. This involves specifying the fluid behaviour and properties at the boundaries of the problem. For transient problems, the initial conditions are also defined.

Solver step is doing simulation and the equations are solved iteratively as a steady-state or transient.

Finally a postprocessor is used for the analysis and visualization of the resulting solution. and Verification model validation / adjustment

Where CFD can be Applied?

Every Fluid flow problems can be solved using CFD, such as  phenomena in our daily life:
• meteorological phenomena (rain, wind, hurricanes, floods, fire
• environmental hazards (air pollution, transport of contaminan
• heating, ventilation and air conditioning of buildings, cars etc
• combustion in automobile engines and other propulsion system
• interaction of various objects with the surrounding air/water
• complex flows in furnaces, heat exchangers, chemical reactors
• processes in human body (blood flow, breathing, drinking . . .
• and so on and so forth

Can CFD replaced The Experimental Need?

CFD Can’t fully replaced experimental need, but CFD offer cheaper cost than experimental. Besides. CFD give insight flow pattern that are difficult, expensive or impossible to study using traditional (experimental) techniques. CFD still need experimental result because CFD developed from experimental Result.

 

Here’s the different between Experimental and Simulation

As a note, the results of a CFD simulation are never 100% reliable because
• the input data may involve too much guessing or imprecision
• the mathematical model of the problem at hand may be inadequate
• the accuracy of the results is limited by the available computing power

What Is CFD

Wednesday, April 11, 2012

Okay, you just taking your final project, getting your own supervisor. And your assignment is in Mixing Laboratory. after first consultation, you got assignment on simulation using CFD.

Wow, wow, wait… what’s CFD?. Is it so difficult?

That’s my first question when entering mixing lab?. Why should I take this assignment?. I’m bad in Transport Phenomena, and now must simulate fluid Dynamic?.

He he, if you do think like that, then you just like me ten years ago. But don’t worry, when you can think this clearly, you can solve this assignment no matter what.

So let’s talk about what we face. I will give you short explanation, but I hope it’s clear enough for you to understand:

What is CFD Stand for?

CFD stand for   Computational Fluid Dynamics

What is it?

simply say, you solve fluid mechanic equation using Numerical Methods. Usually it’s Navier Stokes equation if you ask

So, I must understand Navier stokes?

If you wanna be professor, yea, you must be able to solve Navier stokes equation by hand. But if you are BSc degree, I think you only need to know global or the philosophy behind this equation. You are not solving this equation manually, computer will do this task for you. All you need to do is setting boundaries

Is it Interesting? Something like solving this thing?

I can say, VERY INTERESTING. Maybe this picture will burst your spirit and realizing that your choice on this assignment is trully Right

A computer simulation of high velocity air flow around the Space Shuttle during re-entry.

A simulation of the Hyper-X scramjet vehicle in operation at Mach-7

Internal combustion engine modeled using ANSYS Fluent

ANSYS Fluent adjoint solver indicates the necessary shape changes to ensure maximum down force for a race car

To Part 2

Learn Computational Fluid Dynamics (CFD)

Friday, April 6, 2012

When I was doing my project on Computational Fluid Dynamics at 2002, I feel it's very difficult to find a website or sources telling about this subject. At that time, I email many professor all around the world to ask for help. One of them is V.V. Ranade, very well known professor in fluid dynamics. He answer very fast "ask your supervisor to help".

So I decide to make this blog as a resource on CFD. I'll put links on CFD Resources, books, forum and tutorial, all about CFD. I, especially familiar with FLUENT and GAMBIT, so my tutorial will cover this two programs.

If you good enough in CFD, you can share your knowledge here. I don't limit any articles, any other CFD Pogram such as CFX, Gridgen is welcome.