Side-pod flow deflector

[hardingfv32]

CofP moved forwards because the pod vane directs better airflow to the rear, by shifting the front tyre wake outboard. Without it the rear aero is less effective, but the front aero remains the same, hence the forward shift.

1) Is it more accurate to state that the pod van shifts flow from the front tyre wake outboard, thus allowing better airflow to the rear wing?

2) Isn't the correct interpretation of the above data that the CofP shifted forward because of gains in the CLf numbers, not a decrease in the CLr numbers. Rear aero is the same and front aero is better with the pod van in place.

Brian

[bhall]

Your question is confusing. On one hand, you mention the removal of parts, but on the other, you've asked about the effect of adding those parts. (I think.)


The Prnt Scrn button is your friend.

The effect of the "side pod fenders," as deduced by their removal, is shown in the results detailed above.


Dallara F312

I'm working on an answer to your query.

EDIT: This might help, because I don't quite know how to explain the connection between the "Coke bottle" and the undercut of the side pods; I just know it exists. Hopefully, someone can step in and make it appropriately engineerish.

[superdread]

The only explanation for the front gain in DF (with fenders in place), I can think of, is that it affects the splitter performance. The splitter is very sensitive to setup (ride-height and springing) as a splitter closer to the floor produces more DF bringing it even closer (the circle continues till an equilibrium is reached). The added DF at the base of the fender (it holds up air above the floor -> creates DF) could move that equilibrium quite a bit.

So the forward DF shift is more a question of setup (if they where forced to develop the car without fenders they would make the front ride height a bit lower and claw most of the front DF back). The advantage of this explanation is that it incorporates the, conventional believed, main use of the fenders as flow conditioners to the rear. On the other hand there are no setup and ride height data, so it is speculative.

[hollus]

Off the top of my head and without real data to back it up:
Without a rolling road, air that normally would flow under the floor might just be piling up in front of the side pods. This stagnant air would disrupt the airflow on the front wing, as it has to eventually find a way around the new obstacle, this might mean for example creating an obliquous flow on the front wing. Removing the side pod deflectors might simply be alleviating this problem, as they are a further obstacle for that stagnant air, while with a rolling road they would direct an airflow that was more or less laminar.
So their absence can also result in an increase on air to the rear wing, without a rolling road, that is.

Edit: I misunderstood the results. Adding the deflector increased the front downforce, so the above sounds a bit silly now. Still, the point that that deflector, without the rolling road, is being fed the wrong flow (implied above, explicited below), stands. As does the point that flow over the front wing will have to eventually find a path around that stagnant flow (which might well exist only in my imagination), and probably starts to do so while interacting with the front wing.

[bhall]

Couldn't you also say that the "front sidepod fenders," at least the bottom parts of them anyway, shield the air flow around the sidepods from the turbulent wake of the front wheels, which guards against stagnation?

[hollus]

Quite possibly, but without a rolling road, the flow around the front wheels will be anything but representative of a moving car.
I guess the point is that one is removing flow modifiers, but without the rolling road one has the wrong flow to modify. Hence that the helpers (fenders, deflectors) seem to not help or even do unintuitive things.

[bhall]

I ask because apparently the F2012 has a problem with stagnant air flow at the front of the sidepods...




...and Ferrari has thrown everything but the kitchen sink at the area in an attempt to clean up and/or energize that air flow.




They've even gone so far to cut out an exit ramp on the floor...


...and they've cut out a portion of the front wing pylons.


But, one thing they haven't done is remove the sidepod "fenders."

I think their purpose is two-fold: to direct air flow to the rear wing/diffuser, and to keep air flow around the sidepods moving so that air flow from the front wing has somewhere to go, much like pre-2009 barge boards.

[hardingfv32]

Quite possibly, but without a rolling road, the flow around the front wheels will be anything but representative of a moving car.

This is not true. The CFD images look quite similar, rolling vs stationary, in regard to flow behind the wheel. PM for a PDF on the subject.

Also, the MIRA tunnel does control the flow on the floor, so underbody numbers are not completely unrepresentative.

Brian

[DaveW]

Also, the MIRA tunnel does control the flow on the floor, so underbody numbers are not completely unrepresentative.

Forgive me, but not when I last looked.... It has a boundary layer bleed around the test area, but no rolling road. Perhaps you would explain how the boundary layer is controlled under a car.

[hardingfv32]

I assumed that was the boundary layer bleed is used to control flow on the floor. Is this incorrect?

I also assume that this control is not going to match the performance of a rolling floor.

Brian

[skgoa]

But that is only good enough if you are manely concerned with aerodynamic devices that aren't in ground effect. (I.e. not when looking at the FW or floor.)

[hardingfv32]

But that is only good enough if you are manely concerned with aerodynamic devices that aren't in ground effect. (I.e. not when looking at the FW or floor.)

MIRA gets a lot of race car through their tunnel each year, most have FW and/or floors. You would think that business would be pretty bad by now if their results were rubbish.

What is the purpose of the ' boundary layer bleed' in your opinion? I would have thought it was to benefit FW and floor activities.

Brian

[amc]

The test was run on the Dallara F308:


The fenders are substantially more complex than on the 312 shown before. They appear to do quite an important job guiding air into the coke bottle and around the rear wheel. The 312 is much simpler as a whole around this area - the sidepods and coke bottle are much more like post-2009 F1. On the whole this means that the 312's fenders themselves are less complex because they have to direct and manage fewer flow streams.

On the issue of increasing front downforce:
Looking precisely at the bottom of the fender and where it attaches to the floor, it is angled straight outwards, thus acting as a splitter, or a front diffuser. It blocks the air going over the top of the floor, increasing the pressure differential at this point. This will enhance the downforce created at the leading edge of the floor, and...

...flow over the front wing will have to eventually find a path around that stagnant flow (which might well exist only in my imagination), and probably starts to do so while interacting with the front wing.

is also a good theory.

But that depends on exactly where the fenders were removed. If the front corner of the floor was removed, it would fairly obviously decrease the front downforce, and I don't have the information to know that. Still, having the fenders IS shown by the data to be beneficial.

In F1, the fender is one of very few parts that is virtually de-regulated, and is therefore a good indication of what teams are trying to do. Ferrari notably have been very active in this area:

I would suggest in Ferrari's case their 'Acer duct' combined with the quite wide sidepods (very little undercut by the 'infor' logo) is choking the coke bottle and causing it to not work as effectively as it has in the past. This is what is creating the stagnant flow problem under the sidepod. They have played around with the turning vanes, floor leading edge, front wing and pylons to improve it, but on the whole it is an issue that has arisen from the car's agressive design, and it will be difficult to properly solve.

[ringo]

Interesting topic. Haven't posted in a while but this is something new.
Why would the Cop move forward? hmmm.....

Could have to do with the floor of the car. The wake off the front wheel is also a factor. I cant draw conclussions without certain evidence, but i think those are clues.

As for the rear wing and diffuser, it doesn't have to be related to those parts of the car. We tend to think only those parts matter when in fact the rest of the car is just as important.

[superdread]

Interesting topic. Haven't posted in a while but this is something new.
Why would the Cop move forward? hmmm.....

Could have to do with the floor of the car. The wake off the front wheel is also a factor. I cant draw conclussions without certain evidence, but i think those are clues.

As for the rear wing and diffuser, it doesn't have to be related to those parts of the car. We tend to think only those parts matter when in fact the rest of the car is just as important.

The basic (part-time) fallacy is: because air moves from the front of the car to the back of the car, the front of the car influences the back of the car more than vice versa.
Especially in pressure driven effects it is often the other way around (e.g. the diffuser increases the DF of the whole floor).

Also the setup can be messed up by simply removing elements, the ride-height of a car is at an equilibrium of DF and spring stiffness and the DF is very dependent on ride height.
Removing a DF-effect increases ride height, thereby reducing DF, increasing ride-height, ... till a new equilibrium is reached.