BLAT?

[FW17]

The '81 Eagle continued the exploration of BLAT (Boundary-Layer-Adhesion Technology) approaches to generating downforce pioneered by chief designer John Ward (Gurney, Wayne Leary, Trevor Harris, Phil Remington and others made significant contributions as important members of the AAR design team), as an alternative to the skirted ground-effect systems that other IndyCar and Formula 1 designers of the period were following. BLAT, which featured a narrow tub with a uniquely wide rear deck rather than conventional sidepods, was better suited to the dimensions of the normally aspirated, aluminum block Chevrolet V8 engine that AAR developed and built as a less-expensive alternative the more-expensive Cosworth turbo V8s that were widely used in CART in the early '80s. The BLAT Eagle went through several iterations, but the '81 car brought its greatest success.

However, elements of Ward's 30-year-old concepts have made a comeback this year in the all-new DeltaWing, which All American Racers has built for Highcroft Racing's Le Mans effort this year.

What is BLAT? how is it different to ground effects of F1 cars?

[strad]

Click photo for video and Dan will explain..from the video Gurneys Eagles
12 somethin Mb

[Tommy Cookers]

Nice car !

IF it is a shorter chord, wider, design than others it should be more efficient in L:D terms (remember the 67-8 F1 wings)

Basic aerodynamics says that edge effects give seperated flow, wasteful but pretty vorticity. Throwing away energy.
Main span effect is attached flow (more efficient ie less inefficient)
So wider is better
Also less chord so less movement of DF/CofP with pitch/heave

Presumably the (then) standard stuff had more DF (coefficient), but a lot more drag (coeff) ?
Like F1, handy on tracks slower than Indianapolis

[strad]

so much for that.

[xpensive]

What is BLAT? how is it different to ground effects of F1 cars?

This is something I'd like to know as well, can anyone give a technical xplanation to this, a little more than Gordon Kirby?

http://www.motorsportmagazine.com/race/ ... to-banned/

[MadMatt]

This is how the Delta Wing car works basically.

What you do is to create a very strong vortex upstream of where you want the suction to be created under the car, as we know vortices is high velocity turbulent airflow which on the other hand is of very low pressure. The barge boards create the same thing effectively as having the small dent that you see up the "E" of the yellow Eagle writing on the front right tyre:



See this CFD representation of a Delta Wing car following another. The pink/purple region under it indicates of course very low pressure:



Initially tho it appears they did not have that small VG dent which is very surprising:



But you clearly see it here in action:



This will induce a large shift of the downforce towards the rear of the car. Good for traction, not good for steering, but well that's another subject! Note that these vortices created under the car (if controlled with success) can help to seal the underbody and diffuser.

(All pictures can be opened in a new window for higher resolution)

[xpensive]

Thank you very much MM, which the way I understand it means i's still Bernoulli based?

But why is this vortex hocus pocus not universally used?

[trinidefender]

Thank you very much MM, which the way I understand it means i's still Bernoulli based?

But why is this vortex hocus pocus not universally used?

It is used in F1 actually. The thing is that since almost all the teams use concepts like this, no car is massively faster than the other. They all use tightly controlled vortices for sealing the floor other things plus they may do something else I'm hypothesising might happen which I will probably start a new thread about when I do some more research on it. That is one of the reasons why F1 cars are still faster than other racing series cars even though F1 cars employ smaller wings and small by comparison diffusers.

A slight bit of confusion though. On the delta wing and the eagle car, are the vortices generated close to the floor by the bit of bodywork sticking out close to floor level and then flow up and over the bodywork?

[Blanchimont]

Is this http://www.oninnovation.com/videos/deta ... 0Is%20Blat the video strad provided in 2012?

"...and remember BLAT was a beer at one time...
...and everybody got a smile out of it..."

Does anybody know how BLAT tastes like?

[MadMatt]

This is how air behaves on a delta wing (!):



And from my explaination, you don't want these vortices to go over the body. What you want over the body is downforce, low velocity air (check the rear of the delta wing to see their massives gurneys right at the very end of the bodywork).

The vortices created by the dent (or "bit of bodywork sticking out close to floor level" as you call them trinidefender) will be directed under the car directly towards the diffuser where the expandable volume will gradually slow the air down to help recovering the pressure.

As I said, barge-boards are doing the same. In the early 2000s you could see cars with this sort of vortex generator for example:



A bit more here: http://www.f1technical.net/forum/viewto ... =6&t=15648

What is interesting with the delta wing (and BLAT) concept is that the following car suffers less from downforce loss than with wing-cars (check that CFD picture, the car on the right doesn't really lose downforce).

[trinidefender]

This is how air behaves on a delta wing (!):

http://cgns.sourceforge.net/CGNSFiles/Chris/delta.gif

And from my explaination, you don't want these vortices to go over the body. What you want over the body is downforce, low velocity air (check the rear of the delta wing to see their massives gurneys right at the very end of the bodywork).

The vortices created by the dent (or "bit of bodywork sticking out close to floor level" as you call them trinidefender) will be directed under the car directly towards the diffuser where the expandable volume will gradually slow the air down to help recovering the pressure.

As I said, barge-boards are doing the same. In the early 2000s you could see cars with this sort of vortex generator for example:

http://img.favcars.com/bmw/formula-1/ph ... 2001_1.jpg

A bit more here: http://www.f1technical.net/forum/viewto ... =6&t=15648

What is interesting with the delta wing (and BLAT) concept is that the following car suffers less from downforce loss than with wing-cars (check that CFD picture, the car on the right doesn't really lose downforce).

I understand how the wings on delta wing aircraft behave with the vortices going over them. That is why I was slightly confused as to how the delta wing car and BLAT car worked. For some reason I had it in my head that the vortices went over the car which to me made absolutely no sense at all to me. Now that you say the vortices go under the car, it makes much more sense.

As I said in my previous post, modern F1 cars use vortices for sealing the edge of the floor, crucial on cars running lots of rake like the red bull cars. These vortices are created by the inside edges of the front wing, by the barge boards, by the vertical turning vanes at the front of the sidepods and by the corners of the front of the widest part of the floor right next to the sidepod. Vortices are also used to seal the gap between the rear tyre and the diffuser.

One final thing that relates F1 cars to the Delta wing car and BLAT car that I feel fairly confident in saying is one more place that I think a vortex is used. Up until now I don't think I have heard anybody talk about it. If you look at the front of the T-tray there are vertical slots right at the front of T-tray on the sides. I have a suspicion that a vortex starts at these slots and runs down either side of the vertical separation holding the plank and into the diffuser. Basically the same concept as the delta wing car and BLAT car but applied to Formula 1.

[Sombrero]

There was another IndyCar using BLAT : Al Unser's Longhorn in 1982. Couldn't find a picture of the BLAT version... The racecar was later modified in a "B" spec using venturi sidepod.

[flyboy2160]

This looks conceptually similar to the current F1 underbody down force designs that are relying on the suction from the diffuser to drive the flow and vortices to seal off the bottom. Note the huge diffuser on that BLAT car. Modern F1 cars have a suction peak at the front of the tea tray that is analogous to that big pink low pressure area on the BLAT car, but much, much smaller due to the smaller area of the tea tray and the stepped floor.

[gavingav1]

another blat

[xpensive]

This is the 1981 Longorn LR02, which was a Williams FW07 with a Cosworth DFX, but there is something added to the sidepods, vortex generators for BLAT perhaps?