'Aerodynamic analysis of a Semi-Truck Trailer vehicle' simulation project by Ali_Arafat


I created a new simulation project called 'Aerodynamic analysis of a Semi-Truck Trailer vehicle':

This project simulates airfow around a Semi-Truck with container trailer.

More of my public projects can be found here.


Aerodynamic analysis of a Semi-Truck Trailer vehicle


The project simulates external aerodynamics of a Semi-truck trailer vehicle via steady state turbulent flow analysis with the K-Omega SST model for turbulence modeling.

The source geometry inculdes a Semi-truck model with trailer and was provided by GrabCAD user Joerg Schmit . The geometry was simplified for external flow analysis and is shown in the figure below . The vehicle has dimensions of about, lenght 16.6 m, width 3 m and height 4 m .

The domain is 18 m upstream, 35 m downstream and 15 m in positive X and Y directions.

semitruck model

To reduce the computational domain symmetry condition was taken along the flow direction. The domain was meshed using the ‘Snappy-Hex-Mesh’ on the SimScale platform. The resulting mesh consists of approximately 6 million cells and is shown in the figure below.

An inlet velocity of 28 m/s was taken with a pressure boundary condition at the outlet. The jobs were run on 16 compute cores and took around 4.6 hours. The simulation analysis the mean flow field around the vehicle. The results below (processed on ParaView) provide insight as to how the flow behaves around the vehicle body. The figures show high pressure distribution on the front face and a large flow recirculation region behind the trailer.

Shown below are the velocity contours.


Shown below are the velocity streamlines.


Shown below is the pressure distribution on the body


Hi Ali,

Nice work. Can you let me know the units of the Pressure plot you have shown above ?

Thank you.



Hi @sachet,

the units are:


You can also open Ali’s project and have a look at the post-processing. The units are always shown when activating the color bar.




Hi, @jousefm . Thanks for that. Actually when i looked at the post processing result evaluation section , it was blank. Can i know the pressure at the back of trailer plot in terms of pascal? Also in the above plot is it a relative pressure ? If it is then what is the reference pressure.

Thank you.



Hi @sachet,

could you provide me with a screenshot of this issue?

First of all units for the pressure in OpenFOAM depend on the solver. Incompressible solvers use m^2/s^2 (also known as kinematic pressure). Compressible solvers use Pa [kg/(m*s^2)] as far as I know.

So you could use the Calculator filter in the post-processing and multiply the pressure in m^2/s^2 with the density in order to get Pascal (this POST might be interesting for you).

Concerning your question about the pressure, you might have a look at this thread (Reference Pressure in Numerics)

I hope I could help you a bit and made no bad mistake :wink:

If you still have questions, feel free to ask anytime!

Happy SimScaling!



@jousefm Hi , Thanks for replying. It seems that i need to download Paraview for using the post processor. I wanted to compare the pressure on the back of the truck trailer in this simulation with my simulation results. Is it possible for you to show me screen shot of the back part of the truck-trailer with the values in m^2/s^2 because the screen shot you provided does not show the pressure at the back part which i am mainly interested in.

Thank you.



Hi @sachet,

no you do not have to download Paraview necessarily. You can also create plots like I did in the integrated Post-Processing tool on SimScale.

This thread might help you there: CFD Post-Processing Guide for SimScale

If you need anything, please let me know.