ANSYS CFX software is one of the most widely used and multi-purpose engineering software used in the master's degree, which is used for computational fluid dynamics (CFD) simulation at all levels and complexities. Many mechanical engineering students and graduates present scientific and research articles, master's theses and industrial projects using CFX ANSYS software.
Introduction of the knowledge of fluids
Knowing fluids and being aware of their behavior has a direct effect on the quality of human life. Many of the equipment used today are directly or indirectly related to fluid phenomena. The fluid flow of cars, planes and ships, blood circulation system, design of turbines, compressors and pumps, etc. are among the cases in which the knowledge of fluid mechanics plays an essential role.
In natural phenomena, equations and laws describing fluid behavior such as equations of continuity, momentum, conservation of energy, etc., in a coupled manner and without the use of computers, the calculations and analysis of those phenomena are very complex and sometimes non-existent. It becomes possible.
The use of numerical methods is a suitable solution to understand the complex behavior of fluids. In recent years, CFD computational fluid dynamics technique has been able to respond to many needs of industrial and academic communities in the field of fluid behavior modeling.
Introducing ANSYS CFX software
Among the various software in the field of CFD, ANSYS CFX software is one of the oldest and most powerful software, whose initial version was published in 1996. It is interesting to know that many parts of the Boeing 787 airplane have been simulated using Ansys software. After that, with the advancement of programming technology, this software was able to perform simulations on unorganized networks.
Ansys is actually a collection of application software in the field of analyzing phenomena, especially issues related to fluids and heat transfer. which can be used to model a mechanical or chemical phenomenon. It is also possible to solve the differential equations governing a phenomenon numerically.
In fact, this software is a tool that helps engineers to optimize the mechanical or electromechanical parts of a system.
CFX software, which is now part of the Ansys integrated software, can perform many complex simulations using the finite volume method and finite element interpolation, with high capability and ease of use.
If you have followed this article, then you must have worked with modeling software such as Catia or SOLIDWORKS. By using these software, you can create geometric shapes of different systems in different conditions. Ansys has the ability to take these generated geometries from these softwares and model the mentioned phenomenon by applying fluid physical conditions on them (fluid and solid physical properties and boundary conditions).
General about CFX software
1. CFX software requires a higher temporary memory than Fluent software due to the ability to store values in grid points and use the Couple solution method to perform modeling. Of course, the CFX software will have a more suitable convergence than the Fluent software due to the use of the quasi-transient coupling solution method. Also, CFX software has more and wider chaotic models.
2. CFX software, like other computational fluid dynamics software, has the ability to write macros. which can be used to apply various initial and boundary conditions in the software.
3. The possibility of extracting more graphic outputs and simulation videos with higher quality is another prominent feature of CFX software.
4. Ability to analyze multiphase problems, FSI fluid structure interaction, turbulent flow models, turbomachine, heat transfer, investigation of viscous and non-viscous flows, nanofluid analysis, etc. are some of the famous features of this software.
5. The speed, accuracy and efficiency of CFX software in simulating problems related to rotating equipment and turbomachines (pumps, compressors, fans, gas and hydraulic turbines) are more compared to other similar software such as Fluent.
6. However, it is less powerful than Fluent software in problems that do not require special physics knowledge, such as reaction domain and dynamic boundary problems.
7. Due to the commercial nature of Ansys, CFX and Fluent software, they are often used by industrial professionals. In some related news, news has been heard about the integration of CFX and Fluent software, which, of course, has not yet come true.
8. CFX software is divided into three stages: CFX-Pre, CFX-Solver and CFD-POST. which are used in order to call the grid and apply the settings and conditions of the solution, perform the solution process and extract the solution results (post-processing).
Steps to solve a problem with ANSYS CFX software
First step: create the solution domain
In general, in order to solve a problem in Ansys software, you must first generate and network the solution area. Then, in the next step, this area is transferred to the solver environment and the conditions of the phenomenon are applied to the solution domain. For example, imagine the goal is to model the movement of an airplane in the atmosphere. For this purpose, in the first step, the plane and the area around it must be produced.
Second step: Networking of the generated solution domain
In the next step, the designed area should be gridded in one of the ANSYS software. Gridding means dividing the entire area into many units or (Cell), which equations are solved numerically in these units. Note that the way of networking has a great influence on the time to reach the answer and also the quality of the final answer.
Third step: transfer the network to the solver and carry out the simulation
In this step, the gridded domain is transferred into the solver and the simulation is performed on it. The solver is the software that solves the physical equations for the generated domain. The most important solvers in Ansys are CFX and FLUENT.
CFX is mostly used to analyze systems based on turbomachines. In fact, this software can be used to optimize systems such as turbines, compressors, jet engines or pumps.
Finally, these steps are explained in the form of three examples. These examples include the analysis of unsteady flow inside the tank, the analysis of two-phase flow inside a bent pipe with a half-open valve, and finally the interaction of the structure on the FSI fluid.
Conclusion
In order to learn this software, you can benefit from the comprehensive and specialized training course of ANSYS CFX software online and in person at the engineering skills development center of Tehran University's Faculty of Mechanics. In this tutorial, firstly, how to generate solution domain and grid in CFX is explained, then how to apply boundary conditions, get output and check them is also taught.