Thursday, May 21, 2009

Monaco - Formula One car set-up guide

Monaco may be the most unique race on the Formula One calendar, but for the engineers the challenge around the demanding street circuit remains the same: fine-tuning the car to achieve maximum performance. It's an unforgiving place, and getting the most from the R29 will require an unusual set-up and total commitment from the driver. As a street circuit, the track usually offers low grip in the early part of the weekend, but come Sunday it will be nicely rubbered-in and will continue to improve until the final lap of the Grand Prix. Renault explain how they plan to ready the R29...
Ride Heights
The roads in the principality may feel billiard-table-smooth at the wheel of a road car, but they are incredibly bumpy for the stiff suspension of a Formula One car. To cope with the variations in track surface, ride heights are raised between 5 and 7mm relative to the norm. The public roads are also sharply cambered and very slippery - especially on the traffic markings that are dotted around the circuit which require caution, especially if the track is damp.
Suspension
In order to maximise the car's grip, the team will use softer suspension settings than normal. This helps the car to ride the bumps and changes of camber. The surface also means that the wheels must be able to move independently to cope with the bumps and so we soften the anti-roll bars to achieve this. Special attention is paid to suspension camber angles too. The key objective is to give the driver a neutral, driveable car that he can have confidence in around the circuit, especially in the fast Massenet-Casino Square complex.
Renault driver Fernando Alonso explains: "The run through Massenet and Casino Square is one of the fastest parts of the lap. The first left- hander seems to go on forever and is quite bumpy so you have to be careful to balance the car on the throttle to avoid oversteer. You have to hug the barrier as much as possible to make a late apex and get online for the next right-hander which is a blind corner. The car becomes very light as there is a bump on the exit, but it's important to get on the throttle as early as possible for the approach to Mirabeau."
Aerodynamics
Monaco demands the highest downforce levels of the season. Contrary to popular belief, the primary benefit does not come in the corners, as many of them are taken at such low speeds that mechanical grip is of greater importance. Rather, the gains from high downforce come under braking and acceleration, keeping the car stable into the corners and ensuring optimum traction on the exit.
Driver Nelson Piquet explains: "The biggest braking zone on the circuit is the chicane of Turns 10 and 11. You come out of the tunnel, which is the fastest part of the lap in seventh gear and have to brake down to 70 km/h for the chicane. It's probably the best overtaking opportunity of the lap and you need good stability under braking."
Steering angle
The famous hairpin at the Grand Hotel is the tightest of the year - along with the sharp turn at Rascasse. Monaco therefore demands the highest steering angle of the season, some two times greater than anything required at the previous race in Barcelona. Dedicated Monaco front suspension is produced to ensure the necessary steering lock can be applied.
"The Grand Hotel hairpin is the tightest and slowest corner of the year,” said Alonso. “It's taken at under 50 km/h and requires full steering lock and is quite a technical corner. It's important to hit the apex so you don't lose too much time through this part of the lap."
Tyres
Previously this season the Bridgestone tyre compounds supplied to the teams have been two steps apart in terms of their characteristics. However, Monaco sees a change to this allocation philosophy due to the unique demands of the street circuit. Bridgestone will therefore bring the super-soft and soft compounds, which are well suited to working at lower temperatures.
Engine
Superficially, Monaco may seem the least demanding circuit of the year, with just 45 percent of the lap spent on full throttle. Appearances, though, do not reflect reality. The bumpy surface means the engine can easily over-rev if the wheels leave contact with the ground. A driveable engine and good traction from very low revs are extremely important.

Saturday, May 16, 2009

Aerodynamics explained – in detail

Aerodynamics is the science that studies objects moving through air.

It is closely related to fluid dynamics as air is considered a compressible fluid. Nowadays, aerodynamics is the utmost important factor in Formula One car performance. It has even nearly become one of the only aspects of performance gain due to the very marginal gains that can currently be made by engine changes or other mechanic component development. This downforce can be likened to a "virtual" increase in weight, pressing the car down onto the road and increasing the available frictional force between the car and the road, therefore enabling higher cornering speeds.

Furthermore, as Formula One teams have the greatest resources to develop aero efficiency of its cars, the greatest strives are made here. F1 teams have unrivalled CFD computing power and at least one full time wing tunnel, only for validating and improving their designs.

While basic aerodynamic methods and formulas can be simply resolved, other properties are verifiable with empirical formulas. More complex shapes such as airplanes or racing cars are however impossible to calculate precisely, rendering computational fluid dynamic systems (CFD applications on super computers) and wind tunnels an absolute requirement to validate designs.

 

 

 

 

 

Application in Formula One

F1 (and in general, all winged racing cars) can be considered to be canard configurations in the sense that the front and back wings are on opposite sides of the centre of gravity and both are "lifting" (strongly) in the same direction, in this case creating downforce.

From a spectator's point of view, a car can be considered in (at least) 3 parts: the front wing, the car's body and the rear wing. Each of the parts can be optimised for the required downforce at a minimum of drag. Practically however, every component has its influence on the behaviour of the car and cannot be regarded as an individual component. As a result, no element is tested individually, but always a complete scale model of a car.

Because a complete racing car is a very complex system, teams of engineers usually evolve the car step by step, developing a particular item and check its effect on the car. Such overall effect can then be calculated with "Amdahl's law":

Here is the fraction of the system (when this fraction generates 5% of the car's drag, then is 0.05) that can be improved, is the improvement factor on this fraction (division of the drag in Newtons and the new drag force after improving that element), and is the overall improvement that will be achieved.

After verifying its improvement, the car's efficiency is determined and then simulated on different tracks to see on where it is useful. That usefulness is always the result of a reduction in drag or an increase in downforce.

Drag

Drag is the aerodynamic force that is opposite to the velocity of an object moving through air (or any other fluid). Its size is proportional to the speed differential between the air and the solid object. It is therefore unimportant if either the air is moving around a static object or if the object is moving at a speed through static air.

Drag comes in various forms, one of them being friction drag which is the result of the friction of the solid molecules against air molecules in their neighbourhood. Friction and its drag depend on both the fluid and the solid properties. A smooth surface of the solid for example produces less skin friction compared to a rough one. For the fluid, the friction varies along with its viscosity and the relative magnitude of the viscous forces to the motion of the flow, expressed as the Reynolds number. Along the solid surface, a boundary layer of low energy flow is generated and the magnitude of the skin friction depends on conditions in the boundary layer.

Additionally, drag is a form of resistance from the air against the solid moving object. This form of drag is dependent on the particular shape of a wing, and is therefore called form drag. As air flows around a body, the local velocity and pressure are changed, effectively creating a force.

Interference drag or induced drag on the other hand is the result of vortices that are generated behind the solid object. Due to the change of direction of air around the wing, a vortex is created where the airflow meets unchanged, straight flow. The size of the vortex, and thereby its drag strength increases with an increasing angle of attack of the aerofoil. As a primary source of possible drag reduction, Formula One teams try to counteract this drag by adding end plates to wings or with fillets at the suspension arms.

Other sources of drag include wave drag and ram drag. The first is unimportant for normal racecars as it occurs when the moving object speeds up to the speed of sound. Ram drag on the other hand is the result of slowing down the free airstream, as in an air inlet.

The amount of drag that a certain object generates in an airflow is quantified in a drag coëfficient. This coëfficient expresses the ratio of the drag force to the force produced by the dynamic pressure times the area. Therefore, a of 1 denotes that all air flowing onto the object will be stopped, while a theoretical 0 is a perfectly clean air stream.

At relatively high speeds, ie. at high Reynolds number (), the aerodynamic drag force can be calculated by this formula:

where is the force of drag (in Newton), the density of the air, the speed of the object relative to the fluid (in m/s), the reference surface and the coëfficient of drag. Note the minus sign and the vector which indicate that the resulting drag force is opposite to the movement of the object.

Downforce

Aerofoils in motorsports are often called wings, referring to aircraft wings. In fact they are very similar. F1 wings and winglets aim to generate high downforce, by having a high angle of attack, thus also increasing the drag of the aerofoil.

The evolution of aerofoils to what they are now is mainly thanks to the genious and research of a few well known scientists. In 1686, Sir Isaac Newton presented his three laws of motion, one of them being the conservation of energy. He stated that energy is constant in a closed system, although it can be converted from one type to another. Out of that theory, Daniel Bernouilli deducted a formula proving that the total energy in a steadily flowing fluid system is a constant along the flow path. An increase in the fluid’s speed must therefore be matched by a decrease in its pressure. Adding up the pressure variation times the area around the entire body determines the aerodynamic force on the body.

An aerofoil's operation can be easily explained when you consider a wing in a steady, laminar flow of air. As air is a gas, its molecules are free to move around and may have a different speed at different locations in the airstream. As downforce generating aerofoils are mostly designed with more thickness on the lower side, the lower airstream is slightly reduced in surface, hence increasing the flow speed and decreasing the pressure. On top of the wing, the airspeed is lower, and thus the pressure difference will generate a downward force on the wing. Additionally, and in line with Newton's third law of motion, downforce wings are never straight and induce a new turning of the airflow. More specifically, the shape of the wing will turn air upwards and change its velocity. Such speed creates a net force on the body.

This shows that a force causes a change in velocity , or also, a change in velocity generates a force. Note that a velocity is a vectorial unit, having a speed and a direction component. So, to change of either of these components, you must impose a force. And if either the speed or the direction of a flow is changed, a force is generated.

It is very important to note that the turning of the fluid occurs because the molecules of the fluid stay in contact with the solid body since the molecules are free to move. Any part of the solid body can deflect a flow. Parts facing the oncoming flow are said to be windward, and parts facing away from the flow are said to be leeward. Both windward and leeward parts deflect a flow.

Downforce is however often explained by the "equal transit time" or "longer path" theory, stating that particles that split ahead of the aerofoil will join together behind it. In reality however, the air on the longer side of the wing will flow much faster, further increasing the downforce effect.

While these simplified versions are the basics of lift and downforce generation, the reality can hardly be simplified and is a complex study, requiring high power computer systems. For a gas, we have to simultaneously conserve the mass, momentum, and energy in the flow. Hence, a change in the velocity of a gas in one direction results in a change in the velocity of the gas in a direction perpendicular to the original change. The simultaneous conservation of mass, momentum, and energy of a fluid (while neglecting the effects of air viscosity) are called the Euler Equations after Leonard Euler. Several computer algorithms are based on these equations to make an approximation of the real situation.

Because of the complexity, today's Formula One cars are designed with CFD (computational fluid dynamics) and CAD (computer aided design) that allows engineers to design a car, and immediately simulate the airflow around it, incorporating environmental parameters like traction, wind speed and direction, and much more.

Wednesday, May 13, 2009

Ferrari revert to complex front endplates

There was a time when Ferrari was known for its complicated front wing endplates, and steadily it looks like that is coming back. The team however is now only a follower as they copy various design properties of other, faster cars.
The endplate has complicated since the car's first race. An additional vertical element was added, very similar to the Brawn BGP001. Slightly hidden is a small slot that catches air and directs it inwards of the end plate. Additionally the wing itself now has a higher curve close to the end plate, something that was also copied from Toyota.

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Tuesday, May 12, 2009

Aero updates for Brawn BGP001

Brawn have introduced their first car updates at the Spanish GP, keeping them ahead of the competition. One of the changes includes a redesigned engine cover. While the previous design was a smooth cover, the new updated sidepods have a sharper inward curve. More in the centre of the car, following the exhausts is a new cover of the suspension components.
Marked with a second arrow is also the slightly modified bodywork ahead of the exhaust openings, somehow resembling the curved sidepods of the Force India VJM02.

 

Monday, May 11, 2009

Formula 1 teams - aero upgrades seen in Spain

Aerodynamic updates are abundant at the Spanish Grand Prix

Pretty much every team on the Formula 1 grid has brought a major update to Barcelona for the Spanish Grand Prix. Some are clearly working, others are not working so well. When asked if the updated McLaren MP4/24 was improved driver Lewis Hamilton gave a clear answer to the BBC: "No." McLaren had one of the more minor update packages in Spain as it has focussed on introducing small updates at each race rather than large major updates. Brawn GP brought its BGP001's fitted with a new floor, engine cover, and bodywork around the rear suspension.

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Renault had a similar update kit as Pat Symonds explains "as we have said earlier we introduced our first double decker diffuser in China but it was very much our first attempt. There is a new attempt here. In addition, with visible parts, we have got new front wheel fairings, we have got a new top rear wing here. We have got modifications on rear suspension, so there is a lot going on."

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The biggest update of all was seen on the BMW-Sauber F1.09,  The nose, side pods and the rear wing are completely new, while the front wing, the engine cover and the diffuser have been modified. This has given the car a strange new look which has already enhanced usage of the cars 'ugly' tag. 

Friday, May 8, 2009

Barcelona's Circuit de Catalunya - an F1 set-up guide

The Spanish Grand Prix circuit near Barcelona is one that every Formula One team knows well from the hundreds of kilometres of testing carried out there over the winter. Few venues offer such a variety of medium and high-speed corners and it is widely acknowledged as the definitive aero circuit that provides a stern test of a car. With few big braking zones and so many high-speed corners, overtaking is extremely difficult and a good qualifying performance and sensible strategy are paramount for a successful weekend. Renault explain how they plan to ready the R29 for racing…

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Aerodynamics:
Aerodynamic efficiency is always a key factor at Barcelona, although the introduction of the chicane at the end of the lap in recent years has replaced on of the most critical high-speed parts of the lap and means the track is not as demanding as it once was. Even so, the circuit remains the ultimate test of a car's aero package and teams will run with high downforce levels to ensure competitiveness over the whole lap.
Renault driver Fernando Alonso explains: "There are lots of high-speed corners where good aero performance is critical. A good example is Turn Nine, a fast right hand corner taken in fifth gear at about 230km/h. You have to be very precise with the car as there is there is no room for error on the exit and it's important to carry good speed onto the back straight."
Suspension:
With the suspension we have to find the best compromise to give the drivers a well balanced and responsive car. This means we will use relatively stiff settings at the front of the car to get a good change of direction, while the rear will be slightly softer in order to get the best possible traction out of the slower corners, such as Turns 14 and 15.
Ride height is also an important parameter to consider as generally we can run the car quite low in order to gain maximum aerodynamic performance.

Engine Performance:

Barcelona is not generally thought of as an 'engine circuit' as the engine is not under particular stress as any point and only 61 percent of the lap is spent on full throttle. There are relatively few hard acceleration zones from low revs as the engine spends most of the lap accelerating from the middle of the rev range. As such, the priority is for the power delivery to be progressive and driveable in order to maintain the best handling balance, and limit tyre wear.

Tyres:

Barcelona is well known for being demanding on tyre wear because it includes so many long, high-speed corners and has a fairly abrasive track surface. The most demanding corner is perhaps Turn Three.

The tyres are therefore under high loadings, particularly the front left which has to work hard through Turn Three as well as Turn Nine. As a result Bridgestone will supply the hard and soft compounds this weekend, and the team will need to pay close attention to the wear and degradation during free practice to determine which compound to use for the majority of the race.

Wednesday, May 6, 2009

Force India, more upgrades but no KERS yet

Force India will add more modifications to their car for this weekend’s Spanish Grand Prix, but have put off introducing KERS until later in the season, choosing instead to focus on the VJM02’s aerodynamics.

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The team were pleasantly surprised by the performance gains obtained from a new diffuser and aero upgrades at the last round in Bahrain and further revisions for Barcelona could boost their competitiveness still further.
“We'll have yet more upgrades coming through based on the information we gained in Bahrain,” confirmed team principal Vijay Mallya. “We'll be running a driver-adjustable front wing flap and a further modification for the front wing. This is just part of our ongoing development cycle and there will be further upgrades at most of the forthcoming races.”
The Spanish Grand Prix had also been pencilled in as the race where Force India would add KERS to their armoury. However, after witnessing the mixed fortunes experienced by those teams running the system, Mallya says Force India will concentrate their efforts elsewhere for now.
“We have decided to put the emphasis on aero development where we feel the greater gains can be found,” he said. “As we've seen many other teams are not running KERS so we do not feel we are at a disadvantage. We still plan to use it later in the season, but this will be reviewed after each race in line with the other work we have going on in the background.”
Though world championship points have still eluded them, Force India have clinched a top-ten finish in 2009 - Adrian Sutil took ninth in Australia - and Mallya admitted their pace has exceeded his expectations.
“We always said that the first four flyaway races would be extended test sessions and we have indeed used them wisely,” he said. “We've accustomed ourselves to the new systems, new personnel and new ways of working and introduced some very worthwhile upgrades.

Monday, May 4, 2009

FIA reveals Formula 1 2010 regulations

Refuelling ban, and other cost limitation measures

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Formula 1 will not feature refuelling pit stops next year after the FIA revealed a number of changes to both the technical and sporting regulations. Many of the changes are aimed at reducing team budgets such as the introduction of a slightly different set of rules for cost regulated teams.

The ban on refuelling is also aimed at keeping costs under control, allowing teams to leave the large and weighty fuel rigs at home and thus save on freight.  This will have a major influence on race strategy as tyres will now define everything, fuel efficiency will also be critical. Notably the cars will also be 15kg heavier with an increased minimum weight of 620kg. Tyre warmers have been outlawed, meaning very few series now permit them at all, it seems likely that they will fall out of use entirely in the next few years

F1 KERS has undergone some notable changes, its usage is no longer permitted when the car is travelling at over 300kph, and all the storage devices must be situated between the front face of the engine and the driver's back when viewed in lateral projection. A brake valve can also be fitted to the energy recovery system which can reduce the pressure generated by the driver in the rear brake circuit during KERS operation.

With such major changes the teams now have a scramble to lodge entries by 29th May, the €309,000 entry fee to be payable on 1 November 2009.

Saturday, May 2, 2009

BMW pins hopes on upgrade package

BMW Sauber expects a 'significant' improvement in its pace when it introduces a swathe of upgrades for the Spanish Grand Prix, but with so many of its rivals doing likewise, the team is unsure whether its development efforts will pay off.

Technical director Willy Rampf explained that major aerodynamic changes were on the cards as last year's third-best team tried to get out of its current lower midfield position.

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"The nose section, more deeply undercut sidepods and the rear wing are all totally new," he said.

"Added to which, modifications have also been made to the front wing, engine cover and underbody. We expect these improvements to significantly reduce our lap times.

"Of course, we know that the other teams will also have made modifications to their cars for Barcelona.

"However, we expect to be able to close the gap to our rivals.

"We won't find this out for certain, though, until the race weekend.

"Up to then we will only have the results from the wind tunnel and simulations to go on and, of course, can no longer test in advance on the track."

Team boss Mario Theissen admitted that BMW's very poor start to 2009 had been tough to take.

"We cannot be satisfied at all with the first four races of the season," he said.

"After our positive winter testing, all of us at the BMW Sauber F1 team envisaged a rather different start to the season.

"The car is not fast enough and we have recorded only one podium finish.

"We are approaching this challenge in a positive way and are working intensively in Munich and Hinwil to get back to our old form.

"We will be lining up in Barcelona with an extensive aerodynamics-focused development package, and are already working on further upgrades to be introduced later on in the season."