Monday, August 2, 2021

Transient Thermal good way to make quick cfd/thermal calculations

 Some engineers unfamiliar with the most famous CFD programs such as Fluent, CFX or Open Foam may have problems solving technical issues related to heat transfer.


In such situations, it seems that the ideal solution will be to use the commercial Transient Thermal software (there is also the Static module).  It is a program with a very intuitive GUI.  It doesn't take great knowledge of fluid mechanics or heat transfer to solve basic thermodynamic problems.

In the Ansys package we have two modules for solving tasks related to statics and dynamic problems.  

The transient thermal (also static thermal) menu looks practically the same as the modules for calculating mechanical issues (static structural).  All problem definition is performed on the tree of all modeling phases.  First, we prepare the geometry in the CAD program.  The Ansys package includes a choice of two SpaceClaim or Design Modeler programs.  After we recognize that our model is ready for calculations, we enter the Setup module where we will perform all other activities.

The next step in modeling is to define the finite element mesh.  In the tree, in the Mesh option, we define the element type, size and type of mesh.  The next definitions are made by going down the tree.  So then we define the boundary and initial conditions.  It can be convection assigned to a given surface of the element, radiation or a heat flux of a certain value.  Transient Thermal offers us a fairly wide material base as well as ready-made boundary conditions.  It is possible to define parameters dependent on temperature and time.  Everything is done very easily by defining tables.

In the next step, we define the time of our analysis, we can also determine the size of the time step as well as the type of solver that will count our problem.  At the last stage of the tree, we define what kind of results we want to get.  We can plot temperature distributions on surfaces, entire solids or on sections of interest to us.  We can also define graphs for variable data from a single node or finite element.  All the output data can be easily exported to external programs and processed.

An interesting option of this type of thermal calculation program is the mixing of material models.  By combining two types of materials and specifying their proportions, Transient Thermal automatically calculates the thermal and physical properties of a given combination.  This can for example be used to define a layer of porous material by combining e.g. solid and air.


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