Q
How can swirl be represented at an inlet which is very small compared to the overall domain, i.e. without meshing the inlet in detail?
A
There are three solutions to the problem you describe:
1. Explicitly mesh the swirler inlets in your model. This can be expensive computationally if the inlets are very small compared to the size of the room or if there are a large number of inlets. Care needs to be taken that the mesh is sufficiently fine to resolve any important variations in the flow.
2. Perform a detailed simulation of the inlet in isolation (i.e. in a surrounding box with pressure boundaries all around) from which the velocity profile on the pressure boundary could be exported. This could then be applied as a specified-velocity inlet boundary condition on the coarser mesh of the whole domain. Depending on the location chosen for the surface surrounding the detailed simulation there may be inflow (entrainment) into the inlet region. In this case the boundary condition should be of type Opening, to allow flow both to enter and leave the domain through the surface surrounding the inlet.
3. The third option is essentially the same as Option 2, except that rather than perform a detailed CFD simulation of the inlet to give the boundary conditions for the coarser mesh, experimental data may be used to specify the velocity profile.
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Q How can swirl be represented at an inlet which is very small compared to the overall domain, i.e. without meshing the inlet in detail? A There are three solutions to the problem you describe: 1. Explicitly mesh the swirler inlets in your model. This can be expensive computationally if the inlets are very small compared to the size of the room or if there are a large number of inlets. Care needs to be taken that the mesh is sufficiently fine to resolve any important variations in the flow. 2. Perform a detailed simulation of the inlet in isolation (i.e. in a surrounding box with pressure boundaries all around) from which the velocity profile on the pressure boundary could be exported. This could then be applied as a specified-velocity inlet boundary condition on the coarser mesh of the whole domain. Depending on the location chosen for the surface surrounding the detailed simulation there may be inflow (entrainment) into the inlet region. In this case the boundary condition should be of type Opening, to allow flow both to enter and leave the domain through the surface surrounding the inlet. 3. The third option is essentially the same as Option 2, except that rather than perform a detailed CFD simulation of the inlet to give the boundary conditions for the coarser mesh, experimental data may be used to specify the velocity profile. |
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