Cross-country Speed Research Articles

Optimization of the geometry of the glider wing taking into account statistical data

The article presents a synthesis of an optimization algorithm for an aerodynamic characteristics of a sailplane in preliminary design phase aimed at increasing average cross-country speed. The flight data of SZD-48-3 standard class FAI glider was collected and analyzed from weglide.org portal as a flight track files, saved in igc format. The general structure of an atmosphere was analyzed during cross-country flight basing on collected statistics. New integral criterion for the target function has been presented for usage in optimization routine loop. The criterion permits a reduction of multicriterial optimization problem to united parameter.
 Genetic Optimization algorithm has been selected as a main optimization tool due to its ability to find global optimum of an unsmooth multidimensional target function and robustness in general. The parametrization scheme with minimal number of parameters has been presented for a wing with a complex planform. The Lifting-Line Theory and XFOIL solver implemented as a mathematical model of an aerodynamic characteristics of the wing. As a result, prospective ways for consecutive development have been revealed. In particular, application of synthesized optimization algorithm towards any other classes of aerial vehicle and introduction of airfoil to wing parameterization.

Patterns of Nutrient Intake among Male and Female High School-Aged Cross-Country Skiers and Speed Skaters

This study aimed to determine the appropriate nutritional intakes and dietary habits of high school-aged cross-country skiers and speed skaters. The subjects, all high school students from N Prefecture, included 18 male cross-country skiers, 5 male speed skaters, 10 female cross-country ski players and 4 female speed skaters. Physical measurements, food intake frequency survey results, bone mineral density and exercise stress test outcomes, and lactic acid measurements were evaluated. Female athletes in both sports had higher body fat percentages relative to the average range stated for female athletes. Male speed skaters had a significantly higher maximum oxygen in-take than that male cross-country skiers did. By contrast, this parameter did not differ significantly among female athletes. A negative correlation was observed between the fat free mass and muscle mass, and a positive correlation was observed among the body fat percentage, fat percentage, and fat mass. Both male and female athletes had protein intake ratios within the reference ranges. All athletes except male speed skaters had lipid energy ratios that were higher than the upper limit of the reference value. Both male and female athletes also reported carbohydrate energy ratios within the reference ranges, but had cereal energy ratios below the reference values. Athletes should pay attention to the ingestion of various nutrients to ensure a sufficient energy intake. Accordingly, adolescent athletes should consume daily meals containing a good balance of staple foods, main dishes, side dishes, milk and other dairy products, and fruits.

Using an optimisation process for sailplane winglet design

ABSTRACTA multi-objective optimisation process is used to design winglets for a high-performance sailplane. The primary optimisation objective is to maximise the average cross-country speed over a range of thermal strengths. Additional contributions to the cost functions are the limitation of the total drag during high-speed cruise and the additional root bending moment due to the winglet. Rather than being a pure design study, the purpose of the herein presented study is to demonstrate that a multi-objective optimisation approach is a suitable and efficient alternative to the more traditional, experienced-based design approach. The flight performance of the winglet designs are evaluated using a higher-order potential flow method. Results of the optimisation are hand-selected for further analysis. They are compared to a traditionally designed winglet for the same aircraft, designed with similar objectives in mind. The chosen final designs provide an increase in average cross-country speed of 1.5% at lower thermal strengths and 0.4% at higher thermal strengths when compared to the traditional design. When approximating the effects of trim drag due to wing loading and static margin, these performance gains fall to 0.6% and 0.1% respectively, more closely matching the performance of the traditionally designed winglet. The final designs, along with the traditional design, provide performance benefits across all airspeeds of the flight envelope of the base aircraft without winglets.

Same Citius, Altius, Fortius … More Women, Crashes, and McTwists?

Almost half of the record 98 events being held at the 2014 Sochi Winter Olympic Games were either not held 20 years ago at Lillehammer or have been substantially modified. The Olympics as a global sports event are not stationary but must adapt and evolve in response to changing demands, just as the remarkable athletes who are competing do. While the Winter Olympics program has steadily grown since Chamonix in 1924, the rate of development has greatly accelerated in the last 20 years. Three factors seem to be instrumental. First, the Winter Olympics program has become more gender balanced. Female hockey teams are battling for gold, and this year women will compete in ski jumping for the first time. Most Winter Olympics sports have equal numbers of events for men and women today, although female participation still lags somewhat behind. Second, many traditional events have been modified by sport-governing bodies toward a more "TV friendly" format. Time-trial starts have been replaced by mass or group starts. "Sprint" and team events have been added to spice up traditional sports like cross-country skiing and speed skating. Finally "extreme" sports like half-pipe and ski-cross have crossed over from the X Games to the Olympics, with some arguing that the Olympics need these popular sports more than the X Games sports need the Olympics. All of these changes create new research questions for sport scientists who are also willing to adapt and evolve.

Cross-country speed record

Cross-country speed record

Timing and speed of migration in male, female and juvenile Ospreys Pandion haliaetus between Sweden and Africa as revealed by field observations, radar and satellite tracking

Breeding Ospreys were studied in southern Sweden and 13 birds were tracked by satellite telemetry on autumn migration to the African wintering grounds. This was supplemented with studies of migrating birds at Falsterbo and radar trackings from southern Sweden. Females generally left the nest site 2–3 weeks ahead of males and juveniles. Among males, failed breeders migrated significantly earlier than successful breeders. At Falsterbo, Ospreys passed in the order adult females (median 22 Aug), adult males (26 Aug) and juveniles (30 Aug). Birds tracked by radar achieved cross‐country speeds of 18–47 km/h. Most of our birds wintered in an area from The Gambia to the Ivory Coast, with one juvenile in Cameroon and one female in Mozambique. Ospreys spent on average 45 days travelling an average distance of 6742 km with no significant differences between sex and age categories. Between 0 and 44 days were used for stopovers en route. Females generally made more stopovers at northerly latitudes than males. Average speed on migration was 174 km/d, which is similar to speeds reported for other large raptors followed by satellite. Speed on travelling days was on average 257 km/d with males generally moving fastest. There was a clear tendency for lower speeds and more stopovers in Europe than during the crossing of the Sahara. Migratory activity generally took place between 8 a. m. and 5 p. m. local time and we have no indications of birds flying at night. With 9 hours travelling time the expected cross‐country speed, derived from the theory of thermal soaring flight and assuming thermal climb rates of 1–2 m/s, varies from 251 to 360 km/d, which is similar to the observed mean speed on travelling days. Even so, one male travelled 746 km/d between Sweden and Spain. Some Ospreys need a much larger fraction of travelling days than expected from theory, suggesting that they deposit fuel on the breeding grounds before departure. This is supported by a correlation between the observed fraction of days spent travelling and departure date. In late departing Ospreys, especially males and juveniles, a major part of the energy for migration is probably deposited on the breeding grounds.

A universal dimensionless model for the MacCready sailplane theory

An improvement of the MacCready speed-to-fly theory used in sailplanes cross-country flights is outlined. Two different parameters characterizing the thermal are introduced (the vertical speed of the air inside the thermal and the thermal radius) and a universal dimensionless model is proposed, which can be applied to any sailplane. The maximum average cross-country speed, the optimum airspeeds in descent and climb, the rate of climb in the helical trajectory and other flight variables are calculated versus two abbreviated parameters condensing thermal and sailplane data.

How Fast Can Birds Migrate?

Bird migration is typically characterized by periods of flight, when fuel is consumed, and intervening stopover periods when fuel is deposited. The resulting overall migration speed can be calculated on the basis of flight speed, rate of fuel deposition and power consumption during flight. Energy deposition rate (Pdep) can be estimated as the difference between metabolic scope and field metabolic rate during stopover. Evaluating how migration speed scales with body mass yields a declining speed with increasing mass for flapping flight ( m 0m9), while migration speed increases with increasing mass for soaring flight. For flapping flight, migration speed and power can be calculated according to aerodynamic theory, and in soaring flight cross-country speed can be estimated from rate of climb (when circling in thermals) and the glide polar. Power in soaring/gliding flight is assumed to be a constant multiple of the basal metabolic rate (BMR). We used this approach to calculate expected speeds of migration for 15 species. For a small bird with a typical energy deposition rate (Pdep = 1.0-BMR) and using flapping flight, predicted migration speed is about 200 km/day, while a maximum energy

Field Observations of Thermals and Thermal Streets, and the Theory of Cross-Country Soaring Flight

The classical theory of cross-country soaring flight postulates climbs in discrete thermals, separated by glides through stationary air, and prescribes an speed for the inter-thermal glides, based on the performance of the glider or bird, and the rate of climb in thermals. However, it is known that glider pilots usually fly slower than the theoretical optimum speed between thermals, and often achieve faster cross-country speeds than the maximum predicted by the theory. The reasons for this are analysed in relation to a survey of real thermals over the Serengeti National Park, Tanzania. About 1500 km was flown in straight lines, in a Schleicher ASK-14 motor glider, measuring the airmass lift (vertical velocity of the air) at 15-s intervals. It is shown how the bird or pilot can increase the mean rate of climb in the sample of thermals that are actually used, and so increase the cross-country speed, by selecting an inter-thermal speed below the supposed optimum. If the air between thermals is not stationary, the time lost in circling can be further reduced by variations of speed during the inter-thermal glides. Eventually, if thermals are organised into lines or streets, circling can be eliminated altogether, and linear soaring becomes possible. Linear soaring is also sometimes possible along ridges and escarpments. Soaring in discrete thermals may be seen as one end of a spectrum of soaring techniques, with linear soaring at the other end, giving much higher cross-country speeds. In straight flight, soaring and flapping are end members of another spectrum, connected by various intermediate techniques. A bird migrating by flapping flight in a straight line can reduce its power requirements by flying through thermals or other forms of rising air.

Migration by Flapping or Soaring: Flight Strategies of Marsh, Montagu's and Pallid Harriers in Southern Israel

Migratory flights of Marsh Harriers (Circus aeruginosus), Montagu's Harriers (Circus pygargus) and Pallid Harriers (Circus macrourus) in southern Israel were used to test flight theory predictions. The body sizes of these closely related species are between those of the typical large soaring migrants, such as eagles and storks, and the typical flapping migrants, such as small falcons and sparrowhawks. In soaring-gliding flight, Marsh Harriers reacted to different thermal conditions by adjusting their gliding airspeed to the actual climbing rate in thermal circling; consequently, cross-country speed was related to climbing rate. In contrast, the smaller Montagu's and Pallid Harriers did not adopt gliding airspeeds according to thermal conditions. All harrier species regularly used flapping-gliding flight, predominately soon after sunrise and before sunset, and more often in opposing winds than in following winds. Montagu's/Pallid Harriers used flapping-gliding more frequently than Marsh Harriers. Because they alternate between different flight styles, harriers are more independent of environmental factors, such as thermal activity and wind, compared to pure soaring migrants. This allows harriers to migrate under unfavorable thermal and wind conditions. Marsh Harriers are similar to typical soaring migrants in maximizing cross-country speed in soaring-gliding flight, whereas Montagu's and Pallid Harriers are less adapted to soaring-gliding flight and thus are similar to smaller flapping migrants. Optimal soaring-gliding flight seems to be less relevant for these smaller harriers; they maximize cross-country performance by efficiently combining different flight styles.

Soaring Migration of Steppe Eagles Aquila nipalensis in Southern Israel: Flight behaviour under Various Wind and Thermal Conditions

Raptor migration was studied at two locations in southern Israel in spring 1992. Tracking radars provided exact data on individual flight paths throughout the day, whereby emphasis was on recording entire 'inter-thermal gliding' and 'thermal circling' phases. Steppe Eagles Aquila nipalensis adjusted their flight tactics to the actual wind and thermal conditions: They increased their gliding airspeed under strong thermal convection and in opposing winds. Under certain conditions the usual circling in thermals and inter-thermal gliding tactic was combined with soaring in straight line gliding, suggesting large scale updrafts. Cross-country speeds were considerably enhanced if birds used this combined flight tactic, since it provides gain of altitude as well as progress in the direction of migration. Cross-country speed was positively related to climbing rate in thermal circling. Over the whole diurnal cycle, the mean climbing rate in thermal circling was 1.9 m/s. The highest climbing rates, occasionally up to 5 m/s, were reached around noon. Mean cross-country speed was 12.4 m/s, mean gliding airspeed 15.6 m/s. The upper limit of migration was at about 1600 m above ground level, but 90% of the Steppe Eagles flew below 1000 m above ground, 50% even below 400 m. A comparison with Steppe Buzzard Buteo buteo vulpinus and Honey Buzzard Pernis apivorus, observed under the same conditions, revealed similar flight characteristics. However, Steppe Eagles reached higher crosscountry speeds, reflecting a higher selectivity for optimal flight conditions combined with the use of updrafts while soaring in straight line gliding.

Optimal Flight Paths for Soaring Flight

The problem of optimizing sailplane flight paths to achieve maximum cross-country speeds with zero net altitude loss is considered. A variational formulation is chosen that includes three modes of cross-country soaring: thermalling, essing, and straight dolphining. Optimal solutions are obtained numerically for various atmospheric vertical velocity distributions using quadratic approximations to the polars of two sailplanes representing current high performance Standard and Open Class designs. Implications of the solutions are discussed; especially the optimality of any one mode when more than one mode is possible and the advance knowledge of the atmosphere required in order to choose an optimal speeds-to-fly policy. Particularly important is the result that the maximum cross-country speed through an element of the atmosphere capable of sustaining straight dolphin flight is attained with a speeds-to-fly policy identical to that of some equivalent interthermal flight.