Гидродинамика

368 а m o d i f i c a t i o n o f k i r c h h o f f ' s m e t h o d where Fi(u) is a whole rational function; and e,. are real quantities. The points (s;., 0) are termed the p o l e s of t h e d i r e c t i n g s e t ; they are situated on focal seg'ments and cor ­ respond- to points where the direction of a wall turns through When the generating; and the directing sets are constructed, all currents are easily determined. In fact, by superposing both sets so as t o make the corresponding points coincide, we shall b e able, by following in the plane (;, -q) the stream-line 'i* == const, t o find from the directing set the values of 0 and a t every point of the curve for the given value of the potential 9. Thus 0 and Я will be obtained as functions of the potential 'f; there remains but to find the shape of the contour of the current from the obtained values of f on its free surface, and to deter ­ mine the pressure exerted by the fluid on the wall from the known value of i) for the wall in question. This is done by Prof. Joukowsky in the following manner. a finite angle. Since ' = e ( •/' V w iience for the .shape of the contour of the currents we have dx =' -e''cos 71) (.14j (16)