Гидродинамика

ON SUCTION EXERTED ON LAMINA BY FLOW OF AIR By t h e term suction Prof. Joukowsky denotes the projection o n the direction of the lamina of the pressure experienced by the lamina "when the projection is directed opposite to the flow. P r o f . Joukowsky distinguishes two kinds of flow in which suc ­ t i o n c a n b e produced. In t h e flow of the first kind — a non-vortical flow—a free current i s formed in the fluid where this departs from the edge of the l ami na (Fig. 3).By formulae given in the paper „А Modi ­ f i ca t i on of Kirchhoff's Method" the segment OE — h can b e d e t e r m i n e d t ha t is cut on the perpendicular OK to the lamina b y t h e cur r en t departing from the lamina 0 0 (formula 11). In f o rmu l a C^ l ) is the angle between the direction of flow and the n o rma l t o t he lamina, 2b is the width of the lamina, and ; is the q u a n t i t y given by formula (10). So long as the segment OE is l a r ge r t h a n the thickness of the lamina there will be no suction i n t h e d i r e c t i on of the A'-axis. But if angle [J- is increased there will a r i s e the condition when OE will but slightly differ from t h e t h i c k n e s s of t he lamina; the space ODE will then become c l os ed , t h u s forming- a region of reduced pressure that will cause s u c t i on i n t he direction of OX. A s i t is seen from formula (11), an increase of brings abou t a reduction of h. This result is in perfect agreement with R i a b o u s h i n s k y ' s experiments on autorotation of a sector (Fig. 2) w a s h e d by a flow of air at right angles to the plane of t he s e c t o r . I n t h e flow of the second kind, the velocity circulation a r o u n d the plate has a determinate value 2k not equal to zero, and t h e plate has a cross-section in the form of a narrow ellipse. Th e v e l o c i t y potential is made up of three functions, viz, f u n