前体边条控制技术对航向静稳定性的影响

当飞机航向失稳时，垂尾所在的机身后体处于低能的翼身涡尾流中，效率降低，而机身前体则位于尚未干扰的气流中，在机身头部加前体边条，可以起到增加航向静稳定性作用。通过对一系列前体边条的试验研究，发现长度为机身总长3%的前体边条，可将全机航向失稳迎角提高约8°左右，且侧滑角越小，航向失稳迎角提高越多。通过测压和PIV试验数据可以发现，前体边条提高航向静稳定性，主要是由于前体边条产生边条涡，该涡主要影响机身前体，使得前体背风侧负压力值减小，从而导致前体截面不稳定偏航力矩减小，增加了全机的航向静稳定性。

Effect of forebody strake control technology on static directional stability

When static directional stability of an aircraft is unstable, the typical effectiveness of the vertical tail and rudder to the yawing moment falls off because the vertical tail gradually becomes enveloped in the wake of wing and fuselage. Meanwhile, the forebody remains in the undisturbed flow field, and therefore the static directional stability can be enhanced though addition of forebody strake at the forebody. From the results of a series of experiments on forebody strake, it was found that the angle of attack for static directional stability from stable to unstable was increased by about 8° when chord of the forebody strake being 3% of the length of the fuselage was used. Moreover, as the sideslip angle became smaller, the more angle of attack for static directional stability from stable to unstable rose. The positive effects of forebody strake on static directional stability is due to the vortices of the forebody strake, which could affect the front part of fuselage and thus result in the reduction of negative pressure value on leeward side of forebody. Hence, the unstable yawing moment of cross sections of forebody also decreases, and the static directional stability increases.