SimScale CAE Forum

Lift and drag coefficient calculation in simscale


#1

Hi,

I am using simscale to simulate flow around a body. I have used simulation control-“force and moment calculation” to calculate lift and drag coefficient on the body. The result in the soler log is giving some cd, cl, cl(f), cl® value. Can anybody tell me what cl(f) and cl® stands for?

Also is there any other way of calculating lift and drag in simscale itself?

Currently, I am using paraview for postprocessing, but since the files are too large, it is taking too much time to load the files…and sometimes it is just closing off…any alternative advice for post-processing?

Thanks in advance


#2

Hi @yreddy!

  • Total moment coefficient: Cm
  • Total drag coefficient: Cd
  • Total lift coefficient: Cl
  • Total front lift coefficient: Cl(f)
  • Total rear lift coefficient: Cl( r )

I would have said to use Paraview for post-processing but as it always crashes I would suggest you either rely on the values given by the solver log or maybe our @PowerUsers_CFD have a good tip for you :slight_smile:

Edit: If you have access to EnSight that would also work. Some universities have licenses for this software.

Best,

Jousef


Drag Coefficient result?
#3

Hi @yreddy,

Unfortunately, none that I am aware of. Paraview is very RAM heavy but it should not crash unless you have something like 2 GBs of ram. Just load it and leave it. Large files take a long time to process, sometimes upwards to over 20 minutes to an hour. If its possible you definitely need to use a more powerful computer.

Cheers.

Regards,
Barry


#4

I found it quite easy to determine that the ‘f’ in cl(f) means front and the ‘r’ in cl(r) means rear.

These coefficients seem to have a purpose for 4 wheel vehicle or motorcycle design with reference somehow to the front and rear wheels.

What was not obvious to me was the method of determination for the values of these numbers, but I think it is quite simple.

cl = cl(f) + cl(r) * All cl’s use the same reference areas input into SimScales Result Control Item.

I have not figured out the 2nd equation that we need to be able to figure out these two unknowns.

I believe the 2nd equation will have something to do with reference length because, and here is where I am just guessing, for these to have specific meaning with regard to a vehicle with a two point front/rear ground contact, the reference length should be the wheelbase and must have something to do with calculating cl(f) and cl(r).

If you have a motorcycle with a side-car, and the sidecar’s wheel is between the front and rear wheels then you will have to resort to a more traditional force/moment results solution to obtain ratios for wheel loading.

I have not figured out where cl(f) and cl(r) have any meaning for aircraft use (unless it is on the ground :wink:).

Can anyone confirm that I have ‘figured’ out cl(f) and cl(r) correctly, and what the missing 2nd equation is?

Thanks,
Dale