Uploaded December 2017 | Updated September 2026, 1 hour ago
Dear Engineers!
If you are a student in Mechanical or Aerospace Engineering, there will be a time where you learn about airfoils, CFD (fluid dynamics) and simulation. CFD is a very common tool to simulate flow over airfoils. That being said, there are important factors you must consider in order to obtain an accurate simulation (shown in ANSYS in this case). Here are five tips to help you get the most out of your simulation.
The first tip is to use a structured mesh. In comparison to typical meshes, a structured mesh is highly accurate in the sense that it can be fine tuned near areas of interest. For example, this could be a boundary layer region (i.e. a wall), or a nose cone, or any region where the flow experiences a change in momentum. In addition, structured meshes generate significantly faster than a typical unstructured mesh as each element can be pinpointed in space using Cartesian Coordinates.
The second tip is to use a larger flow domain to prevent backpressure from bouncing off the wall and creating a non-zero potential flow region at the airfoil.
The third tip is to use the Spalart-Allmaras Turbulence model. In general, it is recommended to use a turbulence model regardless of whether you are simulating rarefied high temperature flows (where density is low), or flows in gases where the viscosity can be neglected. Moreover, it is actually imperative that you use a turbulence model in very high speed rarefied flows as the viscous dissipation effects need to be accounted for. When it comes to airfoils, the Spalart-Allmaras turbuelence model can be employed as it does not require a highly accurate mesh to provide good results.
Next, an important procedure to verify your simulation is to check the Wall Y+ Value. This value is used to characterize flow near the turbulent boundary layer, and it tells you how the wall shear stress has been computed. The goal is to achieve a Y+ value either in the single digits (0-10) or a very high value (50+). The Y+ value is a dimensionless value which plays a direct role in the subsequent calculation of lift and drag coefficients for an airfoil.
In the case that your Y+ values are not satisfactory, this brings us to the final tip which is to use Mesh Adaptation. Most CFD programs can do this within a click of a button. Use the "Adapt Boundary" feature in ANSYS Fluent to achieve this. The mesh near the wall will be split into more regions, hence creating a denser grid near the wall. This in turn will provide better results for your Y+ value, and more accurate results for your overall simulation.
I hope you find this video helpful. I wish you all a Merry Christmas and a Happy New Year (from Canada). Let us reach 2000 subscribers by the end of 2018!
For more engineering tutorials, tips and tricks, subscribe to this channel here at: youtube.com/user/vinayak678
Best Wishes,
VDEngineering
My Instagram: instagram.com/vinayak_desh
My Website: vinayakd.com
Dear Engineers!
If you are a student in Mechanical or Aerospace Engineering, there will be a time where you learn about airfoils, CFD (fluid dynamics) and simulation. CFD is a very common tool to simulate flow over airfoils. That being said, there are important factors you must consider in order to obtain an accurate simulation (shown in ANSYS in this case). Here are five tips to help you get the most out of your simulation.
The first tip is to use a structured mesh. In comparison to typical meshes, a structured mesh is highly accurate in the sense that it can be fine tuned near areas of interest. For example, this could be a boundary layer region (i.e. a wall), or a nose cone, or any region where the flow experiences a change in momentum. In addition, structured meshes generate significantly faster than a typical unstructured mesh as each element can be pinpointed in space using Cartesian Coordinates.
The second tip is to use a larger flow domain to prevent backpressure from bouncing off the wall and creating a non-zero potential flow region at the airfoil.
The third tip is to use the Spalart-Allmaras Turbulence model. In general, it is recommended to use a turbulence model regardless of whether you are simulating rarefied high temperature flows (where density is low), or flows in gases where the viscosity can be neglected. Moreover, it is actually imperative that you use a turbulence model in very high speed rarefied flows as the viscous dissipation effects need to be accounted for. When it comes to airfoils, the Spalart-Allmaras turbuelence model can be employed as it does not require a highly accurate mesh to provide good results.
Next, an important procedure to verify your simulation is to check the Wall Y+ Value. This value is used to characterize flow near the turbulent boundary layer, and it tells you how the wall shear stress has been computed. The goal is to achieve a Y+ value either in the single digits (0-10) or a very high value (50+). The Y+ value is a dimensionless value which plays a direct role in the subsequent calculation of lift and drag coefficients for an airfoil.
In the case that your Y+ values are not satisfactory, this brings us to the final tip which is to use Mesh Adaptation. Most CFD programs can do this within a click of a button. Use the "Adapt Boundary" feature in ANSYS Fluent to achieve this. The mesh near the wall will be split into more regions, hence creating a denser grid near the wall. This in turn will provide better results for your Y+ value, and more accurate results for your overall simulation.
I hope you find this video helpful. I wish you all a Merry Christmas and a Happy New Year (from Canada). Let us reach 2000 subscribers by the end of 2018!
For more engineering tutorials, tips and tricks, subscribe to this channel here at: youtube.com/user/vinayak678
Best Wishes,
VDEngineering
My Instagram: instagram.com/vinayak_desh
My Website: vinayakd.com
