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1、Aerodynamics 空氣動力學Basic Principles 基本原理The popularity and accessibility of paragliding has compelled theoreticians to simplify the fundamentals of aerodynamics so that it can be more comprehensible to everyone. In my attempt to follow this spirit in my book, I will explain Bernoullis general law or
2、principle, along with the concepts of glide ratio and polar curve, all of which will be outlined shortly. It is thanks to its aerodynamic wing that a paraglider is able to fly, and flying speed depends on the shape of the wing, which is specially designed and manufactured. During the launching proce
3、dure, as the wing is pulled overhead, air entering from the front fills the wing and internal pressure is built up, thus enabling it to take on its intended shape. The air enters the central part of the wing and circulates to build up pressure in the closed wing tips making a semi-rigid, more or les
4、s solid, wing.飛行傘（滑翔傘）的普及性和可及性使得理論家們不得不簡化空氣動力學的基礎原理，以便於每個人易於理解。我在書裡將試著沿用這種精神，我將跟滑降比率和性能曲線一起解釋伯努利一般定理或者原則，而上述幾個名詞亦將會簡短的說明。感謝空氣動力的翅膀使得飛行傘得以飛行，而飛行的速度取決於被特別設計並且製造的翅膀的形狀。在起飛階段，因為翅膀被拉在頭頂，由於自前面填充進入翅膀的空氣和內部的壓力的增加，使得它能夠呈現預計的形狀。而那些進入傘翼中央部分並且循環的空氣增加了傘翼封閉端壓力，並使其成為半硬式（多少是固態的）的傘翼/，At this point, the wing is infla
5、ted and aloft. While the wing is flying the air that meets the leading edge (front edge) is forced to separate into two airflows. Due to its design, the wing is almost flat underneath whereas it is curved above. 此時，傘翼膨脹並且位於高處。當傘翼在飛行中碰上前沿(前緣)的空氣時 空氣被迫分成兩道氣流。 由於設計的關係，傘翼的下緣相對於他的上緣是平坦的。 The lower portio
6、n of the separated airflow continues its course smoothly below, while the upper flow follows a larger course over the curved upper surface. The two flows meet simultaneously at the rear of the wing. 被分開的氣流中的較低的部份繼續沿著下面的路線順利的流動，而上面氣流沿著上緣彎曲的表面上的較長路線流動。兩道氣流同時在傘翼的後緣接觸。According to Bernoullis law of phys
7、ics, accelerated air reduces the pressure the air exerts on a surface, thus there is less pressure on the upper wing side and more pressure on the lower side. Thus due to this difference in pressure the wing acquires lift, an upward force that enables the wing to fly. 根據物理學上的伯努利定律，加速的空氣會降低壓力空氣並施加於表面
8、，因此上緣傘翼會有較低的壓力而下緣的傘翼會有較高的壓力。所以傘翼會因為這種壓力差而得到昇力（使傘翼能夠飛行的一個向上的力量）。If we take the analysis a little further, we can distinguish an other force. The opposite force to lift, which is gravity. 如果我們稍微更進一步的分析，我們能區分出一種其他力量。 昇力的相反的力量，即重力。According to Newtons law, all objects fall to Earth at a rate of accelera
9、tion of 9.8 meter per sec2 (32 ft/sec2), which in the case of our wing, is opposed or slowed down by the aerodynamic forces.根據牛頓定理，所有的物體皆以每秒 9.8 米(32 英呎/秒)的加速度的比率下降到地球。而我們傘翼情況，則是被空氣動力學的力量抵消或者減速。 The aerodynamic forces can be separated into those that work to offset gravity and those that impede forw
10、ard progress. These latter forces are called drag. Added to this drag is friction, which also impedes the glider. 空氣動力學的力量可以被區分為：抵銷重力的力量以及阻礙向前的力量。後面力量被稱為阻力，施加阻力是磨擦力，這也同時妨礙著飛行傘There are 3 sources of friction and drag: 磨擦和阻力的 3 個來源1. Friction on the wing surface from air passage. 2. Resistance of the
11、wing, lines and pilot as solid bodies blocking the airflow. 3. Vortices or swirls on the tips of the wing. 1. 來自空氣流過的傘翼表面的磨擦。2. 傘翼，傘繩和飛行員像固體般堵塞氣流產生的阻抗。 3. 在傘翼上方的渦流或氣旋。The result of all the forces balancing on the wing is the capacity of the paraglider to fly steadily in a gradual downward sloping di
12、rection. The only way we may gain altitude is if the surrounding air current is ascending enough to offset our gradual sinking. As we fly along, our forward motion creates an airflow called the relative wind, which is the wind we feel blowing in our face. Our forward motion through the air and relat
13、ive wind have the same speed. In practice, the wing starts to move through the air when we begin loading it and aerodynamic forces build up. 所有力量在傘翼上平衡的結果，是提供飛行傘一種沿著逐漸向下的傾斜方向穩定飛行的能力。唯一能夠使我們獲得高度的方式，是我們周遭的氣流上昇力的足夠抵銷我們逐漸下沈的力量。當我們獨自飛行時，我們前進的動作製造了一種空氣的流動，稱之為相對風（是一種我們覺得吹在臉上的風）。我們前進通過空氣的動作和相對風有著一樣的速率。實際上，當
14、我們對傘翼進行負重時他就開始移過空氣，而空氣動力學的力量使他增強。Paraglider designers have been trying to achieve greater lift and lower drag, thus improving performance. This is, however, a balancing act since wings enjoying large spans and little chord (depth) produce better performance but are more susceptible to collapse and r
15、equire greater piloting skills. In other words, designers can create the perfect wing in terms of performance but safety may be compromised. The important factor is always safety and this is where experienced test pilots assist in development. Theory and practice have improved the gliders to a high
16、level compared to the older gliders. 飛行傘設計者早已試著獲取更大的昇力及更低的阻力，如此方能改進性能。假如傘翼有著較大的翼展及較小的翼弦（深度、寬度）則會製造更好的性能，但也更易於潰傘也就需要更好的飛行技巧，這兩者之間必須要取得平衡。換句話說，設計者可以製造一個在性能上完美的傘翼，但在安全上就必須被妥協。而安全永遠是一個重要的因子，這也就是試飛員在開發過程中能有所幫助的地方。相對於舊的飛行傘，新的飛行傘在理論與實務方面已經有大幅度的改善了。Let us now analyze forces and the angles that result from them: 現在讓我們分析各種力量的的角度及結果：Description of Terms 名詞解釋R: Attitude angle is the angle between the chord of the wing and the horizon. It is positive above and negative bel
