Under floor flow & diffusers

[chuckdanny]

This Flying bird under the nose of the merc seems powerfull, lets call it angry bird !

[dans79]

This Flying bird under the nose of the merc seems powerfull, lets call it angry bird !

The next question, is how does it improve the car?

[chuckdanny]

Well, first it's not new, the also called bat wing was there with the W05 while not at every grand prix.
They are many theories about the use of vortices. Some claim it seal the underfloor, it improves the speed carried through the bottom of the sidepod by the stream under the nose and maybe burst right in the coke bottle shape area behind the sidepod at the very top speed where maybe the flow is detaching creating drag.
Others claim that it is even calculated to mix whith other vortices like the y250 at the very back end, the exit of the diffuser where it improves the extraction of it.
Well maybe it is only to improve the bernie show with great visuals like in texas in 2013.

[Moose]

Well, first it's not new, the also called bat wing was there with the W05 while not at every grand prix.
They are many theories about the use of vortices. Some claim it seal the underfloor, it improves the speed carried through the bottom of the sidepod by the stream under the nose and maybe burst right in the coke bottle shape area behind the sidepod at the very top speed where maybe the flow is detaching creating drag.

For me, it "obviously" can't seal the under floor. It's rotating the wrong way to do that. This would actually draw air out from under the floor, not force it to stay under there.

[wesley123]

This Flying bird under the nose of the merc seems powerfull, lets call it angry bird !

The next question, is how does it improve the car?

I think it's vortices help at the outer edges of the floor to create a stronger seal. It's in a similar area to where the vortices shed by the front wing are going.

[Moose]

This Flying bird under the nose of the merc seems powerfull, lets call it angry bird !

The next question, is how does it improve the car?

I think it's vortices help at the outer edges of the floor to create a stronger seal. It's in a similar area to where the vortices shed by the front wing are going.

If you read my previous post, you'll see that this isn't what's happening - the vortices are rotating the wrong way to seal the floor.

[chuckdanny]

Well, first it's not new, the also called bat wing was there with the W05 while not at every grand prix.
They are many theories about the use of vortices. Some claim it seal the underfloor, it improves the speed carried through the bottom of the sidepod by the stream under the nose and maybe burst right in the coke bottle shape area behind the sidepod at the very top speed where maybe the flow is detaching creating drag.

For me, it "obviously" can't seal the under floor. It's rotating the wrong way to do that. This would actually draw air out from under the floor, not force it to stay under there.

Yes, i knew there would be confusion there, of course not this one, i was talking about vortices and there different uses.
THe horns that are placed just behind the bargeboard in front of the underfloor behind front wheels and the front sides of the tea tray do that.
THeses ones seal the flow accelerated under the nose where there are no more front wheel (and there wake) to do that.
So the question is why accelerate the flow there? To match or even improve the speed of the diffuser, i have read it is very important, actually i think it is like in the trailing edge of an efficient wing where the speed at the extrados is bigger than the speed at the intrados right in the trailing edge location. It's a condition of a well shut wake.
But i always wondered how the flow could be attached at top speed in the coke bottle shape area where surfaces are facing backward even with the help of the rear wheels wake because sidepod are a pretty inefficient aero shape as seen from top thats why they reduce the height of it toward the end.
It seems that the mclaren honda gave me an answer. Especially for a so tight coke bottle shape. It seems (i say it seems) that there is a low pressure area there that build where they connect Y250 vortex and even maybe reaccelerate it with the twisting air falling from the top of the sidepod and directed there with the little flap above the heat exchanger.

Maybe they even don't generate Y250 vortices anymore as suggested by a very vertical front flap group and replace it with these ones.

[SiLo]

I thought this would either direct more air into the sidepods, giving a much cleaner stream of air and requiring smaller inlets, or it flows around the bottom of the sidepods and along the the length of the car to the rear. It looks too high to help seal the floor.

[Just_a_fan]

The next question, is how does it improve the car?

I think it's vortices help at the outer edges of the floor to create a stronger seal. It's in a similar area to where the vortices shed by the front wing are going.

If you read my previous post, you'll see that this isn't what's happening - the vortices are rotating the wrong way to seal the floor.

Perhaps you should explain how/why rather than just stating a "fact". Explain/show why their rotation is wrong for the task suggested.

[trinidefender]

Well, first it's not new, the also called bat wing was there with the W05 while not at every grand prix.
They are many theories about the use of vortices. Some claim it seal the underfloor, it improves the speed carried through the bottom of the sidepod by the stream under the nose and maybe burst right in the coke bottle shape area behind the sidepod at the very top speed where maybe the flow is detaching creating drag.

For me, it "obviously" can't seal the under floor. It's rotating the wrong way to do that. This would actually draw air out from under the floor, not force it to stay under there.

You've got things muddled up in your head. Underneath the floor there is a low pressure as a result of the very low T-tray and the rake that all F1 cars run nowadays. This means that as air flows backwards underneath the floor it has to expand to fill the expanding space. As the airflow expands the pressure drops. This pressure drop means that airflow from the edge (sides) of the floor wants to flow underneath it. If air is allowed to flow in from the sides then it means less expansion of air, a higher pressure under the floor and ergo, less downforce created by the floor.

The ideal solution is a sliding skirt as was used decades ago until it got banned. This stopped pretty much all airflow from going underneath the car except that that entered from the front of the floor. This ensured maximum expansion and maximum downforce.

You want the downforce to be rotating in a direction that actually helps to draw air out from underneath the floor. This is what seals it and stop air from leaking in.

On the topic of the batwing I highly doubt it is for that. It looks like it is placed to high up for that. From my knowledge it appears the main vortex that is used to seal the floor is created at the corner of the front of the floor next to the sidepods and flowing back along the flick up that all the F1 cars run these days. It is this wing like corner and flick up that creates a counter clockwise vortex on the right hand side of the car (looking forwards) and a clockwise vortex on the left side of the car.

[tok-tokkie]

EDIT: I miss-read the post.

You write looking forwards with a clockwise vortex on the right hand side of the floor. Would not a anti-clockwise vortex be better? It depends on the diameter of the vortex - if the center of the vortex is no lower than the edge of the floor I would suggest that anti-clockwise would be better. Clockwise vortex on the right would have its outer layers peeled off by the floor rather like a woodworking plane blade & that peeled off air would flow under the floor.

[timbo]

This means that as air flows backwards underneath the floor it has to expand to fill the expanding space. As the airflow expands the pressure drops.

Well, this bit is just plain wrong.
The expansion actually slows the flow and raises the (static) pressure.

[trinidefender]

This means that as air flows backwards underneath the floor it has to expand to fill the expanding space. As the airflow expands the pressure drops.

Well, this bit is just plain wrong.
The expansion actually slows the flow and raises the (static) pressure.

Why would the airflow slow down? It has to fill a constantly expanding space therefore it actually has to speed up. A floor with rake works in the same way that a diffuser works. If what you say is right then a diffuser would see high pressure but it doesn't.

[chuckdanny]

This means that as air flows backwards underneath the floor it has to expand to fill the expanding space. As the airflow expands the pressure drops.

Well, this bit is just plain wrong.
The expansion actually slows the flow and raises the (static) pressure.

Why would the airflow slow down? It has to fill a constantly expanding space therefore it actually has to speed up. A floor with rake works in the same way that a diffuser works. If what you say is right then a diffuser would see high pressure but it doesn't.

It's the simple conservation of mass that proves this fact, Q1 = Q2 (no mass accumulated or lost) on two section of a flow tube of different diameter means v1S1 = v2S2 where S1< S2 (that is volume in = volume out, incompressible flow) means v1>v2. Now you still have to find the right tube which in a turbulent flow is what is looked for and never found but lets think about an enjoyable laminar flow.

It's true that pressure is less in the diffuser than on the rest of the underfloor (except entrance of the floor) but still it increases and it is less because air was accelerated at the extractor just cm away.

Looking at the wing of this angry bird, the shape is close to the horns found on the outer front edge of the floor that is a tip at the trailing edge lower point of the adjacent edges, i then suppose that flow must be rotating the same way that is clockwise as seen from the back of the car

[PhillipM]

Why would the airflow slow down? It has to fill a constantly expanding space therefore it actually has to speed up. A floor with rake works in the same way that a diffuser works. If what you say is right then a diffuser would see high pressure but it doesn't.

It does see higher pressure, it's higher pressure than the rest of the floor that is feeding it, the purpose of the diffuser is to allow lower pressures and higher airspeeds under the floor by providing recovery back to free stream pressure. That's why powerful diffuser and floor setups generate downforce gains both front and rear. If it was just the diffuser generating low pressure you'd have to balance it out with a skinny rear wing and a massive front.