Step-by-Step Tutorial: Homework of Session 3 section 2


#1

Simulation Control

For the simulation control we will specify the End time value [s], Number of computing cores and Maximum runtime [s] to 1500, 32 and 50 000 respectively.

Result Control Item 1

As the last step before starting our simulation run, we will create result control items in order to obtain graphical data of the results.

Go to Result Control and click +New next to Forces and Moments.

A new Force and Moment result control item will be created. Rename it to FWing (optional).

Change the Write interval (simulation time steps) to 5

Select solid_0_FWmainwing, solid_0_FWEPin, solid_0_FWEPout and solid_0_FWflap under Faces for force calculation.

Click Save to register your changes.

Result Control Item 2

Create a new Force and Moment result control item for the rear wing. Rename it to RWing (optional).

Change the Write interval (simulation time steps) to 5

Select solid_0_RWEP, solid_0_RWflapa, solid_0_RWflapb, solid_0_RWflapc and solid_0_RWflapd under Faces for force calculation.

Click Save to register your changes.

Result Control Item 3

Create a new Force and Moment result control item for the diffuser. Rename it to Diffuser (optional).

Change the Write interval (simulation time steps) to 5

Select solid_0_Diffuser under Faces for force calculation.

Click Save to register your changes.

Result Control Item 4

Create a new Force and Moment result control item named FWheel (optional).

Change the Write interval (simulation time steps) to 5

Select solid_0_Fronttire under Faces for force calculation.

Click Save to register your changes.

Result Control Item 5

Create a new Force and Moment result control item named RWheel (optional).

Change the Write interval (simulation time steps) to 5

Select solid_0_Reartire under Faces for force calculation

Click Save to register your changes.

Result Control Item 6

Create a new Force and Moment result control item named Body (optional).

Change the Write interval (simulation time steps) to 5

Select solid_0_body, solid_0_Frontsusp, solid_0_Rearsusp, solid_0_Barre, solid_0_Sidepood, solid_0_Frontur, solid_0_Radsupport, solid_0_Rearur and solid_0_Driver.

Click Save to register your changes.

Once all the above steps are defined, we will proceed to create our first simulation run.

Go to Simulation Runs and click on +New. A window will pop up, give a reasonable name to the run e.g. Run-conf-Yaw in this case (optional) and click Create in order to create a new run.

After the run is created, click Start to start the created run. The simulation run can take up to ~336 minutes (~5.5 hrs.)

Post-Processing

Once in Post-Processor, click on Solution fields under Run-Conf-Yaw in order to load the results in viewer. Due to full car model that we are using, it can take up to 20 minutes to load the results in to the viewer.

In order to reduce the time of loading the results we suggest for you to select only U and P under the Property panel and Cell Arrays.

For further instructions about how to post-process your results please follow the same steps detailed in the exercise from Session 2.


Step-by-Step Tutorial: Homework of Session 3
#2

#3

#5

Did you update the value for the Maximum Runtime in the guide? I try to run the simulation again with the 600000sec value. Will keep you updated if the simulation results in an early abortion.

UPDATE: The simulation runs longer than before, but the plot looks troublesome.

UPDATE 2: In hindsight, the plot looks similar to @gmorandini plot. So it seems to work fine.


#6

I am a bit afraid of the oscillations in omega, although the values are small. Could you please give me an explanation?

Best regards,
Dimitrios


#7

Residuals only decrease in a monotone way, or even go to a sort of “plateau” at low level, when the case is steady (with no changes in time). For this case, as other similar cases in which flow is highly detached and a strong shedding is present behind the body (any simulation of bluff bodies), the physical behaviour of the flow is non-steady (it changes with time).
That is why your residuals will oscillate, even when their values are decreasing or going down. I won’t consider it a bad signal before evaluating the flow field. And even more, it wouldn’t be weird to find your forces oscillating too; that’s why it was suggested on the webinar that you should take the average of your last stage of the simulation when extracting information about forces and moments.

Hope this helps :slight_smile:.

Alex


#8

Hi,
whenever i run simulation, i get this error “The machine ran out of memory. Please choose a larger machine for computation”
What does it mean by “machine” here?


#9

Hi @Kamran,

the machine in this case is the server. Increase the number of computing cores and it should work. If not let me know. I’ll run the simulation for you then.

Cheers!


#10

@jousefm @Akrem @AMartinezCava

Hi guys,

I ran the simulation under this specs.

It ran fine, not errors at all. However, I did the post - processing section accordingly to HW2 and I get this. I hide the slide filters in a way to show how does the flow comes from.

I was wondering if someone can tell what is the possible error. I will submit my project link for anything. There is a Saved State file in there.
https://www.simscale.com/workbench?publiclink=1a521825-f5f6-4eb2-aa83-6e3b78eb9a76


#11

Same problem here. I think it’s a problem with the centering, maybe Milad can give us a hand.


#12

@Milad_Mafi


#13

Yes please. that’ll be great. Thank you
Here’s my project link: https://www.simscale.com/workbench?publiclink=c0aecece-adaf-4e00-ac41-3358e14c4b47


#14

I changed the y of center point from 0.3 to -0.3 and changed the radius to 1.5 from 0.35 and it gave me this:


I think this is correct as this shows the streamlines when the car is in a yaw. If someone could confirm this?
@Akrem @mmafi1 @Milad_Mafi @jousefm


#15

i tried to ran the simulation this night and now i have 100% run with the notification “run finished” but the processing bar is yellow in stead of green and there is a notification “Maximum execution time exceeded”. can you help me??


#16

Hey,
after running the simulation with the parameters provided in the tutorial I get this message from the solver:
“The job execution was aborted, possibly due to a numerical instability. Review the log to identify reasons: unphysically large field values, extremely small time step size, etc. Modifying numerical settings and time step size could resolve the issue.”

The residuals look like this


#17

I have setup the meshing and simulation but am getting a message when I go to run the simulation that says that the simulation run will exceed the hours that I have left available, even though I have a community plan. What should I do?


#18

Moved conversation with @ammarj to private.


#19

I had the Simulation done this morning, but after a runtime of 900+ hours an error occured.

End Tim value was 6000
Maximum run time was 600000
cores: 32

Any idea what i should do?

Thanks in advance


#20

Hi,
I’m trying to do the post-processing, but it’s loading for ages (nothing near the 20 mins described above).
Even if i finish loading the first model (and doing the slices), after adding the second model the viewer just hangs and I cannot continue. I had my PC running through the night (~8h) and it’s still not responding. If i reload the page everything is gone.
How did you manage the Post-Processing? Did I miss something? I selected only U and P for the first loaded model.

Greetings


#21

i tried 3 simulations but the last 3 mornings it was always this result, can someone help me what is wrong here? deadline is coming closer…