Гидродинамика

ON SNOWDRIFTS AND ON SlLTiNG OF RIVERS In his second article on snowdrifts Prof. Joukowsky makes a more searching analysis of the phenomenon, considering not only the lines of flow but also the motion of snowflakes near the obstacle- On the basis of tests of Eiffel and of Lukianov on the one hand and of Stokes's formula on the other hand, the resistance of a liquid to the motion of small particles is, at small veloci ­ ties, directly proportional to velocity. An apparatus used for the measurement of the hydraulic velocity i. e. of the velocity of a particle of weight mg, falling with a uniform velocity in a resting liquid, is shown in Fig. 1 (the Kennedy recorder). Assuming the resistance of the liquid to vary directly as velo­ city of the moving particle, Prof. Joukowsky studies the motion of a snowflake near the critical point, at which the velocity of wind is zero. The critical points may be of two kinds. In the vicinity of a critical point of the first kind the lines of flow are hyperbolas having common asymptotes (Fig. 2), and the flow function is the oblique axes x' and y' being di­ rected along the asymptotes; in the vicinity of a critical point of the second kind the lines of flow are similar ellipses, and the In front of the obstacle, there is formed a critical point of the first kind, one of the asymptotes coinciding with the surface of the ground; in the rear of the obstacle is formed a critical point of the second kind. In the first case the differential equations of motion of a par- .ticle have the form (3). In the integrals (4) and (2) the arbitrary current-function