Help with Khasmin

[CottrellGP]

Seriously Dan?

http://www.hibouscientificsoftware.com. ... stallation

I have done all that got it working but i keep getting an error message, Julien is helping me fix the problem.

[kosioBG]

Here is the dummy guide to Khamsin i promissed. Thanks to RicME85 for all the info.

1. Download Khamsin
2. Open Sketchup
3. Go to preferences and add the Khamsin rbz file
4. Reqest and add the license key
5. Go to Khamsin -> Configure
6. Download (built-in links) and install paraview, gnuplot, gmsh and curl in a folder and specify the location in the configure menu
7. Download openFOAM and do the same as in step 6.
8. Download this file and open it in sketchup
9. Relace the body with your model and do that:

+ Khamsin tool -> right-click -> Define -> Volume
+ left button press (i.e press but do not release) on the group in which your car is imported, this should display a local menu;
+ move the mouse to the entry "Volume 0" - it should get highlighted in red, and release the left button;
+ Do the same and select "Close"
+ right-click -> Define -> Boundary Conditions
+ double left click on the the group in which your car is imported, this should display the boundary condition panel;
+ Change the mesh size to "0.01"
+ Select "Close" by left button press over the group, etc.

10. Click Khamsin tool -> analysis -> go(local)
11. That's it

about the results- i don't know how to interpret them either

[astracrazy]

i just tried a test last night using the 100mpg 3deg yaw box, and all i got in the results was a big blue box. how do you make it so you can see inside?

I'm gonna try with the box above though tonight, might be easier as its preset

[RicME85]

I recommend everyone watches the video Julien did of the 250cc Kart as that shows you how to do EVERYTHING

I have just PM'ed astra with how to sort the results in Paraview, here is what I said.

You have done nothing wrong, you just need to do a few more things to display the data.
On the left of the screen is a box called 'Pipeline Browser' ... this is where we need to tweak a few things.

Ok, you should have something like 180.mph.foam in the Pipeline Browser if you have come direct from SU and Khamsin. You can bypass SU once you have the results and just load Paraview and open up the .foam file from the directory you gave Khamsin to put results in. I made my life a lot easier and gave Khamsin its own folder in My Documents so I could get to the result files quicker.

Right, with the the first .foam file open in the Browser, make sure that in the Properties box below it just internalMesh is ticked.
Next, look to the top of the screen, third toolbar down, fourth icon along is 'Slice' ... click it and then click 'Apply' in the properties box.
This gives you a cross-section you can move through the car, it helps with displaying data, you can tweak opacity in the properties box.

Next, back to the Pipeline Browser, make sure the little eye logo is selected for the .foam file then back to the same toolbar as before but click the eighth button along, a ball in between flow lines, this will give you flow over the car, again in the properties you can change a lot of settings so it shows different data and also add or remove flow lines.

With that done you now need to right click in the pipeline browser and open up another copy of the .foam file, this time in the properties make sure that only the ground is ticked.

Back to the pipeline browser and open up another copy of the .foam file and this time just tick your car.

Very long winded but I have found this lets you see a lot of data at the same time.

Having the ground and car separate allows you to have different settings to show pressure etc.

One final thing, I always change the data range, its the second toolbar down, third icon across, next to the first drop box. I use -5000 and 5000 as thats what was used in the test race, you can mess around with that and also the display colours, I found having different display colour ranges for the different parts handy (car, ground, slice etc)

[astracrazy]

thanks ric, ave to work through it tonight. where do you find the cd, cl and center of pressure information

[RicME85]

not sure on those specifics, havent done any serious data mining yet, just been getting things up and running

[astracrazy]

i run a test last night on a part and on the output analysis i got this for my forces

forces output:
forces(pressure, viscous)((34.7833 1386.02 -3085.12) (-0.0607569 2.13449 0.410286))
moment(pressure, viscous)((2025.83 -1361.71 -593.081) (-0.601642 0.0505515 -0.0655812))

anyone know what number relates to what? i.e lift and drag
and is it in N?

i've looked everywhere to try and find something that explains what is what but i can't find anything

EDIT: thanks to julien for his help. drag = 1386.02 + 2.13449 downforce= 3085.12 - 0.410286. both in Newtons

in the forces: the first set of number are the pressure induced forces in the x, y, z directions. The second set is the viscosity (laminar and turbulent) induced forces in the x, y, z directions.

The total drag/downforce is the sum of pressure and viscous induced forces...

[Ft5fTL]

Anyone else get this error while analysing?
http://prntscr.com/y86xq