It often happens that our geometry generated in Design Modeler requires modification. Our model may be incomplete or we need to replace some elements. In such circumstances, it is worth using the Import External Geometry function.
 |
| Example of Improted Shaft (green) to Design Modeler |
More and more often we have to perform combined analyzes, i.e. thermal (CFD) plus strength. Ansys offers for us one-way or two-way FSI analyzes (FSI - fluid structure interaction).
 |
| One way Fluid Structure Interaction in Ansys Workbench |
Many of the problems that are modeled in CFD today concern multi-layer objects. It often happens that these models have large sizes and thin layers. Due to this specificity, we have certain conduction properties in various directions of solid body. Drawing such models in the 1: 1 scale causes many problems, primarily related to the generation of a very large number of finite elements. Sometimes the computer hardware parameters do not allow us to perform such an analysis.
 |
| Cyl-orthotropic in Ansys Fluent |
A very interesting option in newer versions of Ansys Workbench is defining materials consisting of several components. It is especially useful because the program automatically updates the physical and thermal properties of the new defined mixture. It is possible to create, for example, porous materials consisting of a solid and a fluid.
It often happens that we want to do a coupled analysis consisting of two CFD and Structural modules. The purpose of FSI analyzes is to set the thermal conditions that came out from CFD simulation to the Structural analysis as boundary conditions. In the module for mechanical calculations itself, we cannot set a heterogeneous temperature profile, therefore it is necessary to perform two analyzes in these cases as FSI. A very common problem in this type of analysis is a bad transfer of thermal conditions to the Structural module. The distribution of values is not the same as what we came out with CFD. Therefore, in these cases, you can simplify the analysis by adding one more Transient Thermal module from which the transfer of temperature distributions is burdened with a much smaller error.
 |
| III stages for simplify FSI case |
Many times, during the implementation of numerical modeling, after completing the boundary and initial conditions and starting the solver we have to do with a sudden stop of the analysis and the appearance of an overflow message. This is the most common type of error that occurs when performing CFD analysis. In today's post, I would like to present two paths to minimize the appearance of this error.
 |
| Most often error in CFX |
Many times in numerical modeling we have a dilemma whether we have to take into account the radiation model, and if so, what exactly to choose.
 |
| Which model of radiation to pick in Fluent |
After many analyzes, we come to the conclusion that each elaboration of the results looks similar (sometimes identical). Then it's time to diversify our report with new indicators and charts. Ansys postprocessing offers many possibilities. First of all, we can display our output with different configurations of contours, velocity vectors or isosurfaces.
 |
| Path to generate measuring lines |
There is often a need to model the gas flow in specific systems with a temperature other than 25 C. Then we include the Energy model in the standard modeling procedure. The number of subsequent models taken into account in our analysis significantly extends the computation time. This is mainly due to the fact that the program has to solve additional equations (in our case, equations related to heat transfer). If our goal is not the temperature distribution in the analyzed domains, then we can simplify the analysis by omitting the Energy model.
 |
| How to define gas properties in Fluent |
 |
| Example of monitor in Fluent |
An important element of each CFD and structural simulation is the precise definition of the global coordinate system. An improperly located coordinate system can lead to many difficulties - primarily in analyzes where the movement of individual elements is defined.
 |
| Example of bad geometry position vs coordiante system |
Today I would like to show you how easy it is to control the analysis in Fluent. All the necessary items can be found in the solver under Run Calculation menu. This is where the coefficients can be modified on an ongoing basis so that our residual equations are at the required level.
 |
| Example of residual plot in Fluent |
An important step in modeling is to define the precision of calculations and the criterion of convergence.
 |
| How to define precision of solver in Fluent |
The figure above shows the definition of static analysis based on the Courant number
In many problems that we want to model, we can meet with the movement of one or more elements. This is one of the three methods available from Ansys Fluent. The others are MRF and SRF (multi refernece frame, single reference frame). Sliding mesh is a traffic definition method for transient analyzes. The other methods can be used both in static and transient. They will be described in more detail in the following entries. In this post we will try to show you how to use the sliding mesh method.
 |
| How to add motion on parts in Fluent |