After a week of fluid mechanics, little white has a basic understanding of fluid mechanics, but there are so many things that fluid mechanics can do, and how well a week might be learned, many concepts are ambiguous. In order to be able to apply the CFD after one months, small white and found the Huang.
"Sister, looked at the fluid mechanics of the week, now has a basic understanding of it, I would like to know what is the relationship between computational fluid dynamics and fluid dynamics?" "Little White asked."
"Small white, so, I recommend a book to you, you first go to the library to borrow their own first look at it, do not understand to ask me again." "Huang said.
So, Xiao Bai went to the library to borrow Huang recommended book "Computational Fluid Dynamics: learning from the practice."
Black cover, looking very high-end. Listen to Huang Introduction, this book is originally for the senior undergraduate, the theoretical part is not many, and the book is more emphasis on engineering applications, is very suitable for such as small white this kind of 0 basic personnel introduction.
Huang also told Xiao Bai to read the book when thinking about the problem, and remind the focus to understand the following questions:
- What is CFD?
- Where can I use CFD?
- How is CFD used in engineering?
- What are the commonly used CFD software?
Xiao Bai went to the stationery store to buy a notebook, write these questions in a notebook. After three days of study, Xiao Bai felt that these problems have been clear.
Xiao Bai's learning experience:
1 What is CFD
2 CFD Applications
3 How CFD applies to engineering
3.1 Pre-treatment
3.2 Computational Solutions
3.3 Calculation post-processing
4 CFD Software
4.1 General software and professional software
4.2 Business software and open source software
4.3 Pre-processing and post-processing software 1 What is CFD
- CFD is the abbreviation for Computational fluid dynamics (computional Fluid dynamic), which uses a computer to solve the problem of mass transfer, energy transfer, momentum transfer and chemical reaction in the process of fluid flow. CfD is a method or tool to solve the problem of fluid mechanics, the use of means is numerical calculation.
2 CFD Applications
- CFD can be applied whenever there is fluid flow. With the development of computer technology and computer computing ability, CFD and widely used in aerospace, shipbuilding, Automotive, food, energy, petrochemical, biomedical and other fields, but also continue to expand to other industries.
3 How CFD applies to engineering
In order to apply CFD to engineering, a lot of work needs to be done, in general, CFD engineering applications can be divided into three stages: pre-processing , Computational solution and post-processing .
3.1 Pre-treatment
The primary purpose of the pre-calculation process is to make the computer recognize the real world . The computer and the human brain are very different, it is not easy to make the computer to recognize the real world.
To give a simple example, there is water in the cup.
Human identification may be by visually sending optical images into the brain, and by remembering to recognize images as cups and water.
But it's going to be a bit of a hassle to get the computer to recognize it. How do we tell the computer, "there is a cup, there is half a cup of water in the cup" the fact?
The first thing to tell the computer is "there is a cup here." We need to tell the computer:
- The size of the cup. What is the shape of the cup? Cylindrical or round table shape? Dimension parameters such as radius and wall thickness need to be defined.
- The space property of the Cup. is the cup on the floor or on the table? We need to give it a positioning size.
Second, we need to tell the computer "there is water in the cup." The cup is, the computer can not know what water is what thing. But we can tell the computer:
- A variety of physical properties of the material in the cup. For example, water density, viscosity, specific heat and so on.
- How much water is in the cup. For example, tell the computer the height of the water or the volume.
By providing the above information, the computer can identify the physical reality of "glass filled with water".
The role of pre-processing is so, to tell the computer fluid flow occurs when the situation, fluid properties, fluid flow following the physical rules and so on. CFD Pre-processing contains some of the following:
- define a flow calculation domain : Establish a fluid flow region. Tell the computer where fluid flow occurs.
- Computational domain discretization : The flow calculation area is discretized into a grid cell.
- Specify the computational control equation : Tell the computer the physical rules to be followed by the fluid flow to be solved.
- define boundary flow conditions : a particular flow problem has a specific flow boundary condition.
- define the initial time flow condition : Tell the computer what state the domain is in at 0 hours.
- solve parameter definition : such as specifying serial or parallel computation, calculation process monitoring, discrete algorithm designation, etc.
- output parameter definition : Defines some calculation parameter output during the calculation.
3.2 Computational Solutions
- Computational Solutions are usually done automatically by the computer, and generally do not require manual intervention. After the pre-processing has been specified, the solver reads all the solve parameters for automatic solution calculation until the solution is complete.
3.3 Calculation post-processing
The computed data are presented in an intuitive way to facilitate interpretation and engineering applications. The way data is presented includes:
- data Table : The physical data on each grid node, usually the original variables such as pressure, velocity, and so on.
- Graph : reflect the law of physical quantity change
- Cloud Map: Reflecting the spatial distribution of physical quantities
- vector plots : reflecting vector space distributions
- Animation : Reacting to changes in physical quantities over time in animated form
4 CFD Software
CFD itself is a numerical method, which is often programmed as a computer program. At present, there are many CFD software can be used for engineering fluid calculation, according to the software function, can be divided into general software and professional software , according to the software source code is open, can be divided into commercial software and open source software According to the position of software in the process of CFD, it can be divided into pre-processing software , Solver software and post-processing software .
4.1 General software and professional software
- General purpose software : Designed for all CFD applications, the general fluid control equation is solved. Generic software has a common pre-processing object that can handle most engineering problems. However, it is precisely because of the need to ensure commonality, and sacrificed some of the performance. General CFD Software, more commonly used such as the ANSYS series of fluent and CFX, Cd-adapco company's star ccm+ and star CD, ESI's Fastran and ace+, Cham company Phoenics, Metacomp Company's cfd++, Altair Company's acusolve, etc.
- Professional software : CFD software designed for a particular industry. professional CFD software such as Pumplinx, NUMECA for pump valve compressors, Pyrosim and FDS for fire-fighting, flovent and Airpak for building HVAC calculations, Flotherm and Icepak for electronic cooling, etc. , professional software has the unmatched modeling and computational precision advantages of general-purpose software in specific industries.
4.2 Business software and open source software
- commercial software : Software source code is not public and needs to be paid for. The CfD software mentioned on the Internet is commercial software, which takes a lot of money to use.
- Open Source software : The software is exposed by sources, the user can compile their own or modify the source code to form their own computing software. At present, there are many CFD open source software, more famous such as OpenFoam, SU2 and so on are relatively good open-source CFD software.
4.3 Pre-processing and post-processing software
The above mentioned CFD software is basically the Solver software (do not exclude some software including pre-and post-processing), there are still some professional pre-and post-processing software on the market.
- pre-processing software : For the CFD pre-processing software, its main task is to do grid division. representative CFD pre-commercial software including Icem CfD, pointwise, Gridgen, Gridpro, etc., open source pre-processing software such as GMSH, Salome, etc.
- post-processing software: Post-processing software also has a lot of representative commercial post-processing software including Tecplot, ensight, such as open source, such as ParaView .
From for notes (Wiz)
"Small white CFD Tour" by CFD knowledge
