How to calculate the vehicle front/rear lift forces

zhang6425532 · May 17, 2013, 06:03

How to calculate the vehicle front/rear lift force? I know how to calculate the whole car lift force, but how to calculate the front/rear lift force separately?

Aeronautics El. K. · May 17, 2013, 07:30

Which software are you using?

zhang6425532 · May 17, 2013, 11:15

Quote:

Originally Posted by Aeronautics El. K.

Which software are you using?

Star-ccm+ and fluent both ok

ggulgulia · May 19, 2013, 09:19

Hey Zhang

I am not giving you a software custom method to calculate the vehicle lift. What I am about to mention in the foregoing discussion is a standard method for calculating the lift/drag forces at any region of the body

The region of interest has to be explicitly defined in the code. For lift coefficient calculation you need to have the area (Vector) of the region normal to the longitudinal direction of the vehicle, say A, and the density of the fluid flowing over the surface of the vehicle, say d, The force has to be calculated by the expression in the code you will be using (all of the softwares nowadays have an inbuilt expression to calculate the force on the surface of interest. This force, say F, is fund out by running the simulation. Then you can create a custom expression to get the force coefficient and running the same in iteration. The following formula has to be used for calculating the force coefficient:

C= F/(0.5*d*A)

For drag coefficient F is along the direction opposite to the fluid flow or along the direction of the area vector, and for lift coefficient F is along the direction aligned with the vertical of the local coordinate system

ggulgulia · May 19, 2013, 09:21

.. and yeah if you are using STAR CCM+ , you can get the example in one of the tutorials given in the help file of the package

PS sorry for the long reply posted previously.. it's just that I emphasize a lot in keeping the basics clear

kyle · May 19, 2013, 14:23

You can get the aerodynamic lift, drag and moment from your CFD software and then do some very simple static analysis to determine the aerodynamic load on each axle.

Aeronautics El. K. · May 19, 2013, 14:50

Quote:

Originally Posted by zhang6425532

Star-ccm+ and fluent both ok

I think that in Fluent you can choose the surface that you want and have it calculate the aerodynamic forces on these surfaces. I'm not so sure about that though.

Quote:

Originally Posted by ggulgulia

... and for lift coefficient F is along the direction aligned with the vertical of the local coordinate system

Lift is in the direction perpendicular to the flow direction.

May 17, 2013, 06:03	How to calculate the vehicle front/rear lift forces	#1
zhang6425532 New Member Fayong.zhang Join Date: Nov 2012 Posts: 2 Rep Power: 0	How to calculate the vehicle front/rear lift force? I know how to calculate the whole car lift force, but how to calculate the front/rear lift force separately?

May 17, 2013, 07:30		#2
Aeronautics El. K. Senior Member Lefteris Join Date: Oct 2011 Location: UK Posts: 341 Rep Power: 16	Which software are you using? __________________ Lefteris

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May 19, 2013, 09:19		#4
ggulgulia Senior Member Gajendra Gulgulia Join Date: Apr 2013 Location: Munich Posts: 144 Rep Power: 13	Hey Zhang I am not giving you a software custom method to calculate the vehicle lift. What I am about to mention in the foregoing discussion is a standard method for calculating the lift/drag forces at any region of the body The region of interest has to be explicitly defined in the code. For lift coefficient calculation you need to have the area (Vector) of the region normal to the longitudinal direction of the vehicle, say A, and the density of the fluid flowing over the surface of the vehicle, say d, The force has to be calculated by the expression in the code you will be using (all of the softwares nowadays have an inbuilt expression to calculate the force on the surface of interest. This force, say F, is fund out by running the simulation. Then you can create a custom expression to get the force coefficient and running the same in iteration. The following formula has to be used for calculating the force coefficient: C= F/(0.5*dA)* For drag coefficient F is along the direction opposite to the fluid flow or along the direction of the area vector, and for lift coefficient F is along the direction aligned with the vertical of the local coordinate system

May 19, 2013, 09:21		#5
ggulgulia Senior Member Gajendra Gulgulia Join Date: Apr 2013 Location: Munich Posts: 144 Rep Power: 13	.. and yeah if you are using STAR CCM+ , you can get the example in one of the tutorials given in the help file of the package PS sorry for the long reply posted previously.. it's just that I emphasize a lot in keeping the basics clear

May 19, 2013, 14:23		#6
kyle Senior Member Join Date: Mar 2009 Location: Austin, TX Posts: 160 Rep Power: 18	You can get the aerodynamic lift, drag and moment from your CFD software and then do some very simple static analysis to determine the aerodynamic load on each axle.