SimScale CAE Forum

Does anybody know why does the pressure coloring show as if it only was 0 Pa?

At first when I ran the simulation with the default settings it showed the different range of colors showing the pressure changing depending on the surface, but now that I’ve added the particles it’s all blue (0 Pa). What should I do?

https://www.simscale.com/projects/jguillamet/skiing_model_blender/

Hello.

Could you check if you have the initial (0) or the final iteration (1000) showing in the post-processor?

It sounds like you are currently inspecting the initial state of the system.

Cheers

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Well, I had it at 0, but is it normal to have such low pressures? I think mines doesn’t surpass 20 Pa.

Now that I think about it, I calculated the pressure at mountains or ski station and it’s about 80000 Pa (depending on the height) and didn’t include it in the simulation.

Hello, I’m no expert, but are you sure that it is 80000 pa, even a brick flying at 400 mph where the air is compressible has about 120000 pa of pressure at most. – https://www.simscale.com/workbench/?pid=2412005133984160976&rru=5dde1430-13ec-4a58-aaf3-4a38478bbfe9&ci=7640f2ee-367d-4da8-b24c-04bb8915e014&ct=SOLUTION_FIELD&mt=SIMULATION_RESULT

maybe try a standard mesh and you might want to check the residuals because some of the things like domains aren’t balanced out yet. you may also want to try to run the simulation a little more too. The cad geometry is giving a warning too this may be a problem too.
could you give me some more info on how you got 80000 pascals?

p = 101325 (1 - (2.25577^10-5)*h)^5.25588

With this formula I plugged in the height which I choose as 2000m

https://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html

Hmmm, I’m not sure my guess is that it is measuring the pressure relative to the air pressure so this will give you just the pressure of force acting on the ski guy. I this the simulation is measuring the pressure on the ski guy and not the constant pressure of the atmosphere,
do you think this is the case?

Yeah, I thought about the difference between applied pressure by the streamof air and atmospheric pressure. So 80000 Pa would be for atmospheric pressure.

So is it correct? That a stream of air at 6.11 m/s (22km/h aprox.) applies at maximum 20 Pa?

Well I used ths pressure to measure the air’s density

using the equation for dynamic pressure PD = 1/2 ρ v2* we can calculate using the air density 1.01178 kg/m^3 and 6.11 m/s to determine the dynamic pressure which would be 19 pascals which is very close to the 20 pascals you got, I do not have a complete understanding of dynamic pressure but I think the max q is close to the 20 pascals you got. This is close to the maximum pressure at this speed and air density. Does that help?

here is the NASA site ----

pressurehttps://www.grc.nasa.gov/www/k-12/airplane/dynpress.html

hope that help,
Frank Lucci

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Thank you so much now I know that it isn’t an error! Indeed, the dynamic pressure is in the drag formula too and it also includes the density.

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