Fluent Installation

Tuesday, August 14, 2012

Some people feel difficult in install Fluent Program in their Computer, especially the function of each programs.

When you receive CD or DVD from Fluent, you must install 3 component to run Fluent completely, which is Gambit, Exceed and Fluent itself. Here’s the explanation of each program.

Installing Gambit

Gambit is drawing tool for Fluent. Here in Gambit, you can draw your object with a precise dimension, doing gridding and then specify Boundary Condition and Zone. That’s the 3 basic utilization of Gambit, and each step, you must specify well to simplify your next step in Fluent.

Gambit is easy, for expert of course. Yes, I can say this is easy, only for you that familiar with the interface. Actually you can use other drawing software such as AutoCAD, but in the process of import, sometimes didn’t match.

Install Gambit is easy, just follow the instruction.

Installing Exceed

Exceed is XWindows. You must install this program when you use Microsoft Windows for your operating system. If you omit this program, Gambit would not run. This is because Gambit actually written for UNIX.

To Install Exceed, follow the instruction

Installing Fluent

Fluent is processing and post-processing software. Your drawing usually in .msh extension, will be imported in Fluent and then, specify the problem, running simulation, and post-processing, including showing result in many forms.

Installing Fluent is simple, just follow the instruction.

Putting Key

Fluent record your LAN Card Serial Number to incorporated in your key. This to ensure that you can only install Fluent in 1 Computer. So, if there’s problem with your Fluent Key, check your LAN. You can ask another key if you send them good reason to do so.

Just put license key in .dat extension to /license folder.

First Step To Take Project In CFD

Saturday, August 4, 2012

A good question comes from reader of this blog, what is the first step for him to do to take project in CFD?.

He feels, like anyone else i guess, learning fundamental of CFD in Transport Phenomena is too much. Anyone wants practical ways to do this. So, based on my experience, here’s what you need to do

1. Specify your Project well

For example, you want to simulate mixing in a tank with gases. So, you will need drawing a tank, blade, baffle (maybe) and porous ring for gases to inject. Draw this on a paper. Put metric record beside your drawing. Specify completely, for example for baflle, you need to specify baffle thickness, number of baffle, baffle clearance etc. Here’s some record:

Tank : Diameter, Height, bottom shape (including it’s size if curved)

Baffle : number of baffle, clearance from bottom, clearance from tank wall, thickness etc

Blade : shape, inner and outer diameter, blade thickness, blade tip form, Rod diameter, rod position (center or off center).

Porous ring : ring shape, bottom clearance, diameter, hole number and diameter) etc.

Why you should need this measurement first?. Because you’ll need everything in drawing to be exactly as in real mixer.

2. Try to draw your equipment in exact, and if failed, simplify your drawing

It’s not only matter of drawing what you concern, but your drawing must be able to grid (slice into small pieces). There’s some limitation in gridding capability both on Gambit or using other software, in complex drawing, you must ‘DIRECT" the program how to grid. Well, The challenge is just begin.

Gridding session is painful step in my experience, if you don’t know the nature of program you use. Open again and again Modelling Guide (if you using Gambit), and try to locate where your shape cannot be grid. If you stuck in gridding, you better simplify your drawing.

For example, perforated ring, it’s difficult to draw small hole in a ring. You better specify an area over ring to gas to be injected.

3. Specify Boundary Condition

In specifying boundary condition, you must understand the nature of each boundary condition. For example wall, flow input, porous etc. Read well the guide or ask your supervisor

4. Try Import to Fluent

Importing to fluent sometimes failed. For example when your grid skewness cannot be accepted. Or your drawing overlapping if you use 2 drawing block and combined together in fluent. As guidelines, try to grid using hexagonal, it’s easier to import. So, after gridding, save your grid and try to import to fluent.

5. Run Simulation

In running your simulation, you must understand that not each of the method available in program, suitable for your case. Choose one, or choose the best. Read much paper about your simulation first and check their method, try to use them, before advance to your own method

6. Reporting

Simulation usually lasted for 3-7 days depend on the computer speed and your grid size. After simulation ended, you’ll need to report your simulation result. Sometimes you’ll need to virtually slice the tank and take data from specific location. It can be done if you read guideline well.

Next post, I’ll try to explain the step in real project..

Good Luck.

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.