英语翻译英译汉,不要图片形式,公式不必翻译If there is no viscous separation or in

英语翻译
英译汉,不要图片形式,公式不必翻译
If there is no viscous separation or induced downwash,the leading-edge suction force exactly balances the rearward component of the normal force and the airfoil experiences zero drag.This is the idea 2-D case described by d’Alembert’s paradox,and is called“100% leading-edge suction.”
A 3-D wing is considered to have 100% leading-edge suction when the Oswald efficiency factor (e) exactly equals 1.0.When e equals 1.0,the induced-drag constant K exactly equals the inverse of the aspect ratio times π.
On the right side of Fig.12.35 is a zero-thickness flat-plate airfoil.Even without the leading-edge separation,which will almost certainly occur,this airfoil must have higher drag because there is no forward-facing area for the leading-edge pressure forces to act against.All pressure force for a zero-thickness flat plate must act in a direction perpendicular to the plate,shown as N.There is zero leading-edge suction,and the lift and induced drag are simply .
Thus,in the worst case of zero leading-edge suction,the drag-due-to-lift factor K is simply the inverse of the slope of the life curve (in radians),as previously determined.
All real wings operate somewhere between 100 and 0% leading-edge suction.The percentage of leading-edge suction a wing attains is called S (not to be confused with the force S in Fig.12.35).
During subsonic cruise,a wing with moderate sweep and a large leading-edge radius will have S equal to about 0.85-0.95(85-95% leading-edge suction).The wing of a supersonic fighter in a high-g turn may have an S approaching zero.
The following method for calculating K for high-speed aircraft is based upon an empirical estimate of the actual percent of leading-edge suction attainable by a wing,which is then applied to the calculated K values for 100 and 0% leading-edge suction.The actual is calculated as a weighted average of the 100 and 0% K.as in Eq.(12.58):
K=SK_100+ (1-S)K_0 (12.58)
The 0% K value is the inverse of the slope of the lift curve,as determined before.The 100%K value in subsonic flight is the inverse of the aspect ratio times π.
In transonic flight .staring at Mdd,the shock formation interferes with leading-edge suction .This increases the K value.When the leading-edge becomes supersonic,the suction goes to zero,and so the K value equals the 0% K value.
This occurs at the speed at which the Mach angle (arcsine1/M) equals the leading-edge sweep .Above that speed the wing has zero leading-edge suction so the K values is always the inverse of the slope of the life curve.
For initial analysis,the supersonic behavior of the 100% K line may be approximated by a smooth curve .as shown in Fig.12.36.This shows the typical behavior of the 100 and 0% K values vs Mach number.
必须通顺,想用翻译软件糊弄的就不要来凑数了

如果没有粘性分离或诱导下洗流,前缘吸力正好平衡了外力向后的分量,此时机翼处于零阻力状态.这就是贝朗特相悖论描述的理想二维状态,也叫做“100%前缘吸力”状态.
而对于三维机翼来说,当奥斯瓦德有效因数等于1.0时,可认为有100%的前缘吸力.诱导阻力常数K为π乘以长宽比的倒数.
图12.35的右侧是一个零厚度的平板机翼.即使没有前沿气流的分离,机翼一定具有很强的阻力,因为前缘压力在机翼表面没有向前的着力面.所有加在零厚度平板上的压力一定作用在垂直于板面方向,及图中的N方向.平板机翼没有前缘吸力,并且升力和诱导阻力都比较简单.因此,零前缘吸力的最坏情况是：由升力引起的阻力系数K是前面确定的升力曲线斜率的倒数（弧度制）.
所有实体机翼都处在100%~0%的前缘吸力之间.机翼所获得的前缘吸力的百分比被称为S（不要与图12.35中的力S混淆）
在亚音速巡航中,小后掠角和大前缘半径的机翼的S值大概在0.85-0.95（前缘吸力的85%-95%）.超音速战斗机的机翼在大速度,小半径转弯时的S值接近于0.
接下来计算高速度飞行器K值的方法基于对机翼获得实际前缘吸力百分比的经验估计值, 此经验估计值用于计算100%和0%前缘吸力时K的值.实际计算的是100%和0%K的加权平均数.例如方程（12.58）
K=SK_100+ (1-S)K_0 (12.58)
0%K的值是前面确定的升力曲线的斜率倒数.对于亚音速飞机,100%k的值是π乘以长宽比倒数.
在跨声速飞行中,激波的形成会干扰前缘吸力,这会使K值增加.当前缘速度变为超音速时,吸力下降为0, 此时的K值也等于0% K的值.
当速度为马赫角（arcsin 1/M）等于前缘后掠角时的速度,就按前面的方法计算K值.当速度大于马赫角（arcsin 1/M）等于前缘后掠角时的速度时,机翼的前缘吸力为零,此时的K值一直保持为升力曲线斜率的倒数值.
对于初始分析,100%K值曲线在超音速时的趋势接近于一条平滑曲线.如图12.36所示.图中为100%k和0%K值与马赫数之间的典型关系.