CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

How it works-Sports car diffuser

Register Blogs Members List Search Today's Posts Mark Forums Read

View Poll Results: What does an undertray diffuser on a sports car do
Creates Lift force 0 0%
Creates Downforce 3 100.00%
Voters: 3. You may not vote on this poll

LinkBack Thread Tools Search this Thread Display Modes
Old   May 19, 2016, 09:24
Smile How it works-Sports car diffuser
New Member
Join Date: Apr 2016
Posts: 1
Rep Power: 0
Incredible is on a distinguished road
What I know: Nozzle increases the fluid velocity and decreases the pressure. Diffuser (a divergent pipe) in a general sense decreases the fluid velocity and increases the pressure.

Now apply this to car undertray: Diffuser at the end of the undertray should decrease air velocity and increase air pressure. This increase in air pressure below the undertray should create LIFT.

Paradox: Diffuser at the end of car's undertray actually creates Downforce!!

Can anyone solve this paradox? Thanks in advance!
Incredible is offline   Reply With Quote

Old   May 19, 2016, 16:21
Senior Member
Join Date: Aug 2014
Posts: 947
Rep Power: 17
fluid23 is on a distinguished road
You are forgetting 2 things:

1) the effect of the undertray as a whole, the nozzle and throat sections will create more downforce than the 'lift' of the diffuser. the diffuser is only there to slow the air back down before it dumps back out the back which will reduce drag penalty of the system.

2) ground effect and the air moving over the top of the car will still result in a net downforce even in the diffuser, I believe.
fluid23 is offline   Reply With Quote


aerodynamics, downforce, sports car, undertray diffuser

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Boundary Conditions Thomas P. Abraham Main CFD Forum 20 July 7, 2013 06:05
Car park ventilation and impulse fans guillaume Main CFD Forum 12 June 27, 2011 12:16
How to generate the cylindric velocity components of a simple annular diffuser undeadking CFX 0 May 20, 2011 07:56
Flow on a car! John222 CFX 3 January 24, 2011 19:43
CFD for a Soap Box Derby car Dean Christakis Main CFD Forum 0 July 6, 1999 02:09

All times are GMT -4. The time now is 11:10.