Lotus E20 Drag Reduction Device

There’re quite a few comprehensive analysis on Lotus E20 Drag Reduction Device, however I’m trying here to put on a simple explanation to the system so that everyone can understand.

Lotus DRD, we call it DRD instead of DDRS as this system is nothing related to DRS, although the function is the same – reducing drag. It’s completely passively controlled by car speed to achieve drag reduction. The benefit of isolating from DRS (compared to the Mercedes DDRS system) is that it’s not limited use to the specific DRS area on the circuits and does not have a delay over activation – the Mercedes DDRS needs to go all the way from the rear wing to the front wing, causing delay.

The whole structure of this device looks like this:

Source: ScarbsF1

It basically contains two inlets – the airbox and the ‘ears’ and two outlets – the periscope/L duct and the mini diffuser/monkey seat. I’m not going through the internal ducting as it’s purely speculation going into this area, for which I’m not very sure about.

Inlet

Besides the normal airbox inlet, Lotus places two additional inlets along each side of it like two ears. Those ears help directing excess flow into the rear part, thus reducing turbulence from air spillage and help generating more downforce when DRD is not activated. In addition, it’s suspected that the air that goes into the ears and airbox subsequently flows into different route through internal ducting to the rear outlets. However, as I’ve mentioned, I’m not going into detail on this.

Source: Sutton Image

Airbox and ‘Ears’ On Lotus E20 Airbox

Outlet

There are two ways that the air can goes out of the car, either through the mini diffuser or the L duct. The path that the air goes depends on the speed, or air pressure.In a relatively low speed, i.e. off throttle condition, air mainly goes through the mini diffuser since higher pressure is required to push air through the narrow L duct. As the critical speed reaches, air can pass into the L duct then exit through 2 slots on each side of the duct, causing stall on the main plain of rear wing.

The structure of both the mini diffuser and the L duct is quite tricky if you look into the detail.

For the mini diffuser, there’s actually a small internal part inside which aids downforce generation when device is not activated.

Lotus E20 Mini Diffuser/ Monkey Seat Detail

The L duct is very narrow to ensure that it’s only activated when a certain speed is reached, those tiny air exiting slots make huge difference to the airflow pattern  – cause flow separation to stall the wing. The FlowViz picture can clearly show this effect:

Me

Lotus E20 Flow Viz Interpretation

Basically Flow Visualization paint is a special liquid sprayed to the car in order to study airflow on the surface. When the car runs, flow pattern is recorded as the paint redistribute due to the air goes over. So as can be seen in the Lotus Flow Viz illustration, there’s a V-shape pattern beneath the main rear plain right in the middle at the exit of the L duct, indicating flow separation, i.e. drag reduction. Also those 3-5 cm slots are shown clearly once zooming in to this area:

Lotus E20 L duct/ Periscope Slots Detail

The device need to be adjusted from race to race to modify the speed of activation, mainly by modifying the cross section of the mini diffuser and the L duct.

So as Mercedes came up with the intelligent DDRS which is activated by DRS, Lotus brought out a entirely passive system DRD. However, neither of the systems has given distinctive advantage to their cars. Regardless of that, it’s still a very clever idea that may inspire engineers for more innovation.

Advertisements

Aerodynamic Components on F1 Car

A F1 car is made of thousands of components and nearly every part need to take aerodynamics into consideration. However, there’re some major aerodynamics components that make huge difference to car aerodynamic performance.

Example of F1 Car Major Components – Exploded View of a BMW

These aero components get mentioned again and again in various F1 technical analysis assuming that people know what they are, but the fact is most people have no idea on those terms! I’m going through some major ones starting from the front of the car to the rear.

Front Wing

The first part we see on the front is definitely the front wing. Being the first means that it’s the first part on the car that interacts with the air, therefore having an important job to determine the under stream flow through the rest of car. The front wing generates 25% to 40% total downforce. Major design modification lies on the endplates and flaps of the wing, aiming to reduce tip vortex and wake of front wheel, which is one of the biggest drag components. In addition, ducts and slots are becoming popular in recent years, as can be seen in Mercedes W duct in 2011 and DDRS in 2012.

Sophisticated Front Wing Flaps and Endplate of MP4-27

Barge Board

This are vertical panels located between the front wheels and sidepods. It deals with the dirty air produced by the front wheels, guiding and smoothing air flow into the sidepod. In recent years’ designs, it may also have the function of feeding more air into the diffuser.

ferrari f2012 side view

Ferrari F2012 Side-view: Barge Board in White

Sidepod

Sidepod is the part alongside the cockpit that accommodates the radiator and engine exhaust. Main Function of Sidepod is to 1) cool down the engine and gearbox; 2) control underbody flow to generate desired downforce. The profile of sidepods are varied significantly on different cars based on different aerodynamics configuration. A memorable design is McLaren L-shaped sidepod on MP4-26 in 2011.

MP4-26 L-shaped Sidepod

Airbox

The opening channel above drivers head that guides fresh and cold air to the cylinder for cooling purpose. Nevertheless, besides the conventional aim of cooling, the air flow through airbox can be utilised to generate more downforce/reduce drag by guiding it later to the desired parts on the rear wing assembly. F duct is a good example making advantage of this air flow. It’s also suspected that the Lotus E20 DDRS/ Super DRS has a tricky design of ‘ear’ inside the airbox.

‘Ear’ Inside Lotus E20 Airbox to Help Guiding the Air

Rear Wing

With the use of F duct and DRS, rear wing is always under spotlight in recent seasons. We’re talking about rear wing assembly here which normally consists of two sets of airfoil. The upper set is the main downforce generator including DRS, while the lower set is known as the beam wing. The whole rear wing sets generate to 30% to 40% total downforce.

Adjustable Rear Flap (DRS)

Flap on the rear wing whose angle of attack can be adjusted by the driver in order to reduce drag. Check out more about DRS here.

F duct

A driver controlled drag reduction system, in which a slot gap is opened on the rear wing flap. This air flow through the gap is able to stall the wing, therefore reducing drag.

Beam Wing

A single element wing at the lower part of the rear wing that helps regulate the air below the upper rear wing sets and improves diffuser performance. As F duct mounted on the upper flap is banned, there is now more aerodynamics consideration taken into the beam wing design. E.g. Lotus DDRS system which utilise beam wing to further reduce drag.

Source: Sutton Image

Lotus E20 Rear Wing Assembly

Gurney Flap

An L-shaped strip along the trailing edge of the wing, commonly on rear wings. With the use of gurney flap, flow separation can be delayed at high angle of attack so that more downforce can be generated. Gurney are used more in wet weather where more grip (downforce) is needed. FIA regulates that Gurneys on the rear wing should not exceed 20mm.

Source: ScarbsF1

Gurney flap along the edge of rear wing

Diffuser

The rear element at the underbody of F1 car close to the floor, from which air exits the car. This is the last components where air interacts with the car. The speed of air flow can significantly influence downforce, whereby the faster the flow exits, the more downforce is generated. Most famous designs in recent years are Brawn GP double diffuser in 2009 and exhaust blown diffuser which many teams used in 2011.

Brawn GP double diffuser

Source: ScarbsF1

Exhaust Blown Diffuser