航空機用ベンチュリ速度計

抄録

Pitot tubes and Bruhn tubes (double Venturi-type) are widely used for aeronautic speed meters at the present time. However, the former are unsuitable for other than for high speed uses because of their low sensitivities, and the latter are likewise unsuitable except for low speed uses because of their too high throat velocities, which attain sound velocity when outside wind velocity reaches to about 270km/hr. The object of the author's reseach is to obtain a new speed meter that is fit for medium speed uses.
From numerous experimental reseaches carried by the author, he has obtained the following two excellent tubes of the single Venturi-type. Both measure 18mm in outer diameter and 105mm in length, and have such merits that their actions are almost unaffected by manufactural errors. The one type of tube has constant value of velocity coefficient K=7.3 above the air speed of V=80km/hr. (In the above K=Δp/(γV²/2g), where Δp means the manometric pressure of the air speed meter.) The other type of tube has constant value of K=5.8 above V=15km/hr, and its critical speed (when the throat air velocity reaches that of the sound) is more than 400km/hr.
These air speed meters might also be used for naval purposes in the water. In this case, in making use of the second type of tube, the pressure difference Δp corresponding to height of 80mm of water column, is probably obtainable at the speed of one knot, and be of sufficient accuracy even under that speed.