Lee is a zone of lower wind speed on the leeward side ( Lee ) of a flow obstacle. The historical use of the slipstream is to plant rows of trees or hedgerows in the open fields where the wind shadow - prevents erosion - in six to seven times the length of the tree height. The term is referred to as slipstream during windless zone behind a moving object. The wind shadow behind moving objects plays an important role in various sports. When a moving object with additional side wind the wind shadow lies under the laws of vector analysis diagonally behind the object.
Use of the wind shadow in the sailing ships
In the sailing ships of the effect of the wind shadow is basically negative: On the leeward side of islands or coasts of the sailors has less wind and therefore less propulsion - the sailing race that is shifting between the counterparty and the wind direction ship takes the opponents the wind out of the sails, because it creates a wind shadow.
In cycling, the wind shadow plays an important role, because the flat terrain from about 20 km / h, the air resistance is greater than all the other resistors. When slipstreaming equally a cyclist traveling ahead is used as a " wind breaker " in the shadow of the drag force and thus - also necessary to overcome his share of the performance is up to 30 percent lower - at the same speed.
In most disciplines, this is allowed and even desirable - the speed of the field and the diversity of tactics to take.
Forms of slipstream driving in groups - team time trial
In a specific form of the slipstream driving, the so-called "Belgian gyro ", the driver alternate constantly, so the leadership is distributed equally among all the drivers and also drivers who in a second row in the backward movement for the end are the group ride in the slipstream. Disadvantages of this formation: The frequent change of leadership of each leading driver must considerably faster than the rate of the overall formation drive (because it gives the lead and approximately 1.80 to 2.00 m always at senior management level ) and the formation works only smoothly if all drivers are equally close. In the team time trial of the Tour de France, this technique is mostly no longer used in the top teams.
Other formations are the wind season, in which each can be about 250 m, the leader falling back to the end of the group or ( exclusively in training) the double series in which can be both leading driver outside fall back past the group.
In crosswind conditions you drive offset laterally in all forms of slipstream driving. For example, running at from the front left of next wind the first driver on the left side of the road, the others lined up to the right of their front man, whereby the front wheel depending on the angle of the obliquely incident wind should be on average approximately at the level of the bottom bracket of the front man. This may be due to the limited width of the road, only a limited number of riders in the group participate (20 to 25), making it the Belgian spring classics on the long straights obliquely incident from the Atlantic wind that fact alone, quickly to divide the field comes in many groups. In order to promote this, the leading driver can also drive instead of the wind incident side ( in the example on the left ) in the middle and almost right on the road to " take " only a small part of the group. This technique is therefore also called " on the windward edge depend ".
Outliers who want to break away from the peloton, usually have only have a real chance of success against the peloton when they alternate with each other in the slipstream.
Detailed studies with the mobile SRM Training System has shown that
- The drag reduction at different positions of a number of drivers - about the train of four - is different high. The last rider must allow up to 15 percent higher than the drag force overcome driving ahead in the lee of the first man;
- Also the leading drivers - surprisingly and in contrast to sailing ( so take wind out of the sails ) - undergoes a reduction in the drag force.
Triathlon and time trial
Only the triathlon (on the long and middle distance, but not in most competitions at the Olympic and Sprint distance) and the individual time trial, the Drafting is prohibited and will be punished with a disqualification or a time penalty because it is considered falsification of its own performance. Especially with the long straights of the Ironman distance in Hawaii by the volcanic desert in strong head winds and high temperatures occurs slipstreaming due to the very different performance levels of all parties very often and was just in the last two years to the controversial issue because regular margins were prescribed.
Driving behind pacemakers: pacemaker race - record attempts
By the slipstream you also created athletic special events such as the pacemaker race, in which, on cycle tracks speeds up to 100 km / h can be achieved in the race behind special motorcycles that are equipped with a steel spacer that role. In Germany, the sport enjoyed a special popularity since the 1920s up to the 1980s, when most German presented the world champion. An upright path still exists in Solingen.
On 3 October 1995, the Dutch Fred Rompelberg reached on the Bonneville Flats in the Great Salt Lake Desert in Utah ( USA) on his special bikes behind a dragster racing car with a huge windshield a speed of 268.831 km / h
See also: stayer world records on the Grenzlandring.
In -line skating has the wind shadow - despite the slower speed - due to the smaller distance to the vehicle ahead even greater pull than when cycling. However, the optimal exploitation of the wind shadow is a single step of the participants needed. Therefore, the skate movements must be carried out in a uniform rhythm, so that the wind shadow group can minimize the distance to the vehicle ahead and maximize the speed. Cheap positions within a slipstream group are the first positions according to the leader. Not only with tempo changes occur in the back of the wind shadow group for so-called " accordion effect ". Low speed differences in the group generate further back in the " holes" between the skaters. At a speed of tightening the skaters the gap to the vehicle ahead can not close often and thus have to be demolished.
As with the cycling of the slipstream inline skating has a decisive influence on the course of the race.
In many categories of motorsport, the wind shadow is used to gain a speed advantage when overtaking almost equivalent racing car or motorcycles. Here, the Afterward propelled leaves in the " quiet zone" of the person in front of this " zoom eye " and then attempts to use the excess speed of up to 25 km / h to get past him.
Especially on straights and banked curves represents the riding in the slipstream of an advantage dar. Therefore, especially on oval courses, as they are today drive on, among other things still in the IndyCar Series and the NASCAR series to almost constantly observe slipstream duels. However, this can happen dangerous collisions.
In sports car racing, such as the 24 - hour race at Le Mans with its long straights, the drafting is an important element in order to save fuel, as each additional pit stop will cost.
In touring car racing the wind shadow is partially used to achieve a better lap time in qualifying. These drive several cars (usually a team or a manufacturer) over a longer distance at a short distance behind the other. An extreme form, "pushing " the front man, which also leads to increasing one's speed is called into the NASCAR scene Bumpdraft.
In Formula 1, the slipstream earlier had a greater importance since it could be better used for overtaking. Since the mid- 1980s, provide diffusers and other air guide elements (eg winglets ) increasingly treacherous eddies at the rear ( "Dirty Air" ), the vehicle control specifically making it more difficult for immediately following, on the front axle and the overtaking.
What rehearsed truck drivers can practice driving in the convoy is already fuel - saving through consideration of and behind each other driving, which is limited by laws, however. With the advent autonomously controlled vehicles and their interconnection with the vehicle ahead vehicles slipstreaming to a certain extent also between cars is safer and thus be impractical.
Who tandem biking good is quasi the " wind shadow " between the pilot and stoker. Without side wind, the air resistance of an occupied tandems is significantly lower than that of two separated radelnden people.
Unlike cycling and motor sport where the slipstream has a positive effect, the wind shadow effect in aviation and air sports negative. Would a plane flying in the wind shadow of another aircraft, which would mean that the wings of the " pursuing " the aircraft are no longer sufficient flow and sags or falls in the worst case into a tailspin. For this reason, fly planes that fly in close formation, as it is sometimes seen at air shows in minimally different heights. In some cases, even the slipstream of an airplane this become a problem. Thus, the Lockheed had P -38 Lightning by their construction the property that she was not or difficult to intercept with a longer nose dive because the wing between engines and gondola generated such a large wind shadow that the elevator was not in the air stream and thus not longer worked. The problem was solved with dive brakes, the abbbremsten the aircraft so far that the elevator was flowing again.
It is similar in parachutists. So should not dwell on the parachute of another a skydiver because drops by the wind shadow of the lower parachutist, the air resistance of the upper parachutist and makes the parachute falls. In the worst case, the upper parachutist falls to the bottom of the parachute.
Very often one finds the use in the German area, that person B would have found in the "lee " of person A to success, what should figuratively say usually anything else that Person A would have prepared for B the way as it were, and B is less resistance to had to overcome.
The tendency of journalists to a pictorial language but also characterizes a not necessarily appropriate use, if it is meant " in the wake of" only in the sense of, such as " social plans in the lee of Hartz IV".