topic Re: Understand which parameters can be extracted from Flow Analysis in Analysis

Understand which parameters can be extracted from Flow Analysis

lfiorio — Wed, 29 Aug 2018 11:12:51 GMT

Currently we are running some external CFD analysis on parts of our robot to get the lift and drag coefficient and the center of pressure [1].

The simulations are performed using ANSYS Fluent [2].

Considering that the CAD model of the robot is designed using PTC Creo, and considering that recently PTC has introduced a module for flow analysis [3], we would like to run such simulations directly in Creo.

The only problem is that so far we didn't find a document or a video explaining how to get the lift and drag coefficient and the center of pressure.

Here the questions:

- Do you know if it is possible to get the lift and drag coefficient and the center of pressure for external CFD?

- Do you have a link to a document that explains how to run such simulations?

- Which package (basic, plus or premium) should we buy?

Thank you.

[1]:https://www.youtube.com/watch?v=jNnQeKuF7PI

[2]:https://www.ansys.com/it-it/products/fluids/ansys-fluent

[3]:https://www.ptc.com/-/media/Files/PDFs/CAD/Creo-5/Datasheet-Creo_Flow_Analysis-en.pdf

Re: Understand which parameters can be extracted from Flow Analysis

skunks — Thu, 30 Aug 2018 09:35:44 GMT

Re: Understand which parameters can be extracted from Flow Analysis

cfdgeek — Fri, 07 Sep 2018 19:48:31 GMT

Hi,

Yes, you can select the surface and create a xyplot to monitor pressure or shear force on that surface.

To compute lift and drag coefficient, we can use expression to do that very easily. You can use expression to define equations and formula. We also support user defined variable for xyplot.

Example of cl, cd calculation

-----------------------------------------------

den=1.16
area=1
aoa=15*pi/180
vmag=200
cx=cos(aoa)
cy=sin(aoa)
nx=-cy
ny=cx

drag=(flow.px@patch.surfname + flow.tx@patch.surfname)*cx
+(flow.py@patch.surfname+flow.ty@patch.surfname)*cy

lift=(flow.px@patch.surfname + flow.tx@patch.surfname)*nx
+(flow.py@patch.surfname+flow.ty@patch.surfname)*ny

plot.cd = drag/(0.5*den*vmag^2*area)
#plot.cd: Drag Coefficient []

plot.cl = lift/(0.5*den*vmag^2*area)
#plot.cl: Lift Coefficient []

-----------------------------------------------------

here flow.px@surfname means pressure force x component from flow module at surfname patch

similarly, flow.tx means shear force x component.

For the center of pressure, we need to do an integration of x times pressure of x component on all external surfaces and it is straightforward to use expression to write it.

----------------------------------------------------------------------

cpx = integral(x*flow.pressure*normal.x, patch.surfname)/flow.px@surfname
plot.cpx = cpx
#plot.cpx: Center of Pressure x []

----------------------------------------------------------------------------

Please contact me if you got further questions!

ls@simerics.com

Thanks.

Re: Understand which parameters can be extracted from Flow Analysis

cfdgeek — Tue, 11 Sep 2018 13:00:11 GMT

For the package, if you only have external fluid dynamics problems. You only need the basic package, that includes flow, turbulence, heat transfer and all post processing tools. The setup is very straightforward. Most of external fluid problems, we can get the converged solution in couple minutes. We can also show the results in the real time during the calculation.

For the cl, cd and center of pressure calculation, you can select the surface and create a xyplot to monitor pressure or shear force on that surface.

To compute lift and drag coefficient, we can use expression to do that very easily. You can use expression to define equations and formula. We also support user defined variable for xyplot.

Example of cl, cd calculation

-----------------------------------------------

den=1.16
area=1
aoa=15*pi/180
vmag=200
cx=cos(aoa)
cy=sin(aoa)
nx=-cy
ny=cx

drag=(flow.px@patch.surfname + flow.tx@patch.surfname)*cx
+(flow.py@patch.surfname+flow.ty@patch.surfname)*cy

lift=(flow.px@patch.surfname + flow.tx@patch.surfname)*nx
+(flow.py@patch.surfname+flow.ty@patch.surfname)*ny

plot.cd = drag/(0.5*den*vmag^2*area)
#plot.cd: Drag Coefficient []

plot.cl = lift/(0.5*den*vmag^2*area)
#plot.cl: Lift Coefficient []

-----------------------------------------------------

here flow.px@surfname means pressure force x component from flow module at surfname patch

similarly, flow.tx means shear force x component.

For the center of pressure, we need to do an integration of x times pressure of x component on all external surfaces and it is straightforward to use expression to write it.

----------------------------------------------------------------------

cpx = integral(x*flow.pressure*normal.x, patch.surfname)/flow.px@surfname
plot.cpx = cpx
#plot.cpx: Center of Pressure x []

----------------------------------------------------------------------------

Please contact me if you got further questions!

Thanks.

Re: Understand which parameters can be extracted from Flow Analysis

bduncan — Mon, 10 Dec 2018 09:08:39 GMT

amazing

Re: Understand which parameters can be extracted from Flow Analysis

Ruben1 — Wed, 27 May 2020 06:58:53 GMT

Hello CFD Geek,

I really want to know the drag coefficiënt of a car I developed. (it's for school en for the shell ecomarathon) Could you help me? I have no clue what I need to do...

I put the body into flow analysis and everything works, I just don't understand what I need to do to get the drag coefficiënt...

Please help 🙂

Re: Understand which parameters can be extracted from Flow Analysis

cfdgeek — Thu, 28 May 2020 19:04:04 GMT

Hi Ruben1,

It is very simple to do that in Creo Flow. We have a tutorial for external flow to demonstrate that. I will send you the link soon. Thanks.

Re: Understand which parameters can be extracted from Flow Analysis

Ruben1 — Fri, 29 May 2020 08:07:39 GMT

Thanks! I could really use that tutorial!

I don't wanna be rude, but I need to hand in my paper in 3 weeks, would be nice if I can put the result in my paper...

Thanks again!

Ruben

Re: Understand which parameters can be extracted from Flow Analysis

cfdgeek — Fri, 29 May 2020 18:33:42 GMT

https://support.ptc.com/help/creo/creo_pma/r6.0/usascii/index.html#page/tutorials_pma%2FTruck_Overview.html%23

Re: Understand which parameters can be extracted from Flow Analysis

Ruben1 — Sat, 30 May 2020 09:41:48 GMT

1. In the Flow Analysis Tree, under Physics, select Common.

2. Click :

XYPlot. A new entity xyplot3 is added in the Flow Analysis Tree under Results > Derived Surfaces > XY Plots.

This plot doesn't show up for me tho...

Re: Understand which parameters can be extracted from Flow Analysis

Ruben1 — Mon, 01 Jun 2020 11:20:59 GMT

@cfdgeek Could you help 🤔 😑

I'm sorry to annoy you xp...

Re: Understand which parameters can be extracted from Flow Analysis

cfdgeek — Mon, 01 Jun 2020 15:50:34 GMT

Hi, if that does not show up, it means you are using some old version of creo parametric. What version are you using? Please make sure you are using the same version as in that tutorial. If you cannot upgrade creo parametric, that custom variable is saved in a file called xxx_integrals.dat in the folder of your creo model. You can find it out from that file after the simulation finished.

Re: Understand which parameters can be extracted from Flow Analysis

Ruben1 — Tue, 02 Jun 2020 07:44:39 GMT

I use Creo 5 .

I took a screenshot of what I have...

Re: Understand which parameters can be extracted from Flow Analysis

cfdgeek — Tue, 02 Jun 2020 10:02:29 GMT

The 2nd column is your cd, please refer the column data to its caption title

Re: Understand which parameters can be extracted from Flow Analysis

cfdgeek — Tue, 02 Jun 2020 10:06:58 GMT

Hi,

Do you mind mentioning which school team are you working for this project? We may help your team on that project for CFD and aerodynamics design questions. thanks.

Re: Understand which parameters can be extracted from Flow Analysis

Ruben1 — Wed, 03 Jun 2020 13:54:50 GMT

hello cfdgeek,

We are from 'Vives Kortrijk - Belgium.'

https://www.vives.be/nl/opleidingen/industri%C3%ABle-wetenschappen-en-technologie/bachelor-autotechnologie

"The 2nd column is your cd, please refer the column data to its caption title"

How do I need to do that exactly?

I uploaded the xxx_integrals.txt 🙂

Re: Understand which parameters can be extracted from Flow Analysis

cfdgeek — Thu, 04 Jun 2020 19:12:25 GMT

That is the drag coef you are look for.

Re: Understand which parameters can be extracted from Flow Analysis

cfdgeek — Thu, 04 Jun 2020 19:14:21 GMT

time	userdef.Coefficient_of_Drag

the 2nd column data

Re: Understand which parameters can be extracted from Flow Analysis

Ruben1 — Thu, 04 Jun 2020 20:23:00 GMT

yes, but there are so many different values in that 2nd column data. wich value is the right one?

Re: Understand which parameters can be extracted from Flow Analysis

Ruben1 — Mon, 08 Jun 2020 07:31:15 GMT