As I mentioned in the previous post, in the next one I will deal with a detailed description of the defined analyzes in CFD Ansys programs. First, I will provide a step-by-step tutorial on CHT analysis modeling in Fluent.
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| Meshing for Fluent CHT Analysis |
In the first step, we generate a mesh on our geometric model. Two basic steps should be performed: define the size of a single finite element and the type for all accepted domains (in our case, the gas domain and solid - kloc). For our model, the size of the finite element was 7 mm and we defined the triangular type for the entire geometry (blue frame). Thanks to the Body Sizing option, it is possible to define the size of the finite element for the selected 3D volume. With Face Sizing, you can define the finite element size for the contact between solid - gas domains. The Patch Conforming Method defines the type of finite element from which our mesh will be built and increases the uniformity of increasing / decreasing elements.
All boundary and initial conditions were presented in detail in the previous post. You can find all the information in the link below.
Boundary Conditions for Tutorial from previous POST
The next step is to select the type of analysis (in our case, transient) and to select the type of solver for flow calculations. We will use Pressure Based Solver due to the fact that our gas will not reach the speed higher than 0.3 Mach.
Of course, for CHT analyzes it is important to define gravity thanks to which we do not ignore the influence of important pressure phenomena and temperature differences.
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| Type on analysis anp flow solver in Fluent |
The next step is to select solvers depending on what phenomena we want to analyze during our CHT analysis. In our case, for the simplified simulation, we choose the Energy solver (heat transfer) and the turbulence solver. We choose the k-omega SST because of two aspects - we have gas flow from a nozzle inclined at an angle other than 90 degrees and because our gas stream meets an obstacle in the form of a kloc
In order to shorten the calculation time, we do not take into account any radiation models - we assume a negligible impact of this phenomenon on heat transfer in our domains..
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| Solvers for our defined CHT analysis |
The next step is to define the type of gas that will be the main heat carrier. In our case, we define air as a compressible gas due to the fact that we want to fully apply the phenomena of forced convection.
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| Type of defined gas in Fluent - compressible model |
For the defined Named Selection domains (the first picture in the post - blue frame) we define their type (gas / solid - the picture below - red frame). Then we define the boundary conditions of the model: Velocity Inlet and Pressure Outlet. All BC's parameters are listed below.
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| BC's defined in Fluent |
In Solution Methods, all parameters are left at the default position. The total analysis time in our case will be 48 seconds for a time step size of 1 second (Run Calculation). We will record every 6th step in postporcessing (Calculation Activities).
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| Solution Methods and Run Settings in Fluent |
In the next post, I will present a complete tutorial for the same CHT analysis but modeled in CFX.
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