Physics. — “Stationary streaming caused by a body in a fluid 
with friction”. By Prof. J. M. Burgers. (Communicated by 
Prof. P. EHRENFEST). 
(Communicated at the meetings of 18 Dec. 1920 and 29 Jan. 1921). 
§ 1. In this paper a summary will be given of some types found 
in the literature of the stationary streaming in a fluid caused by 
the uniform rectilinear motion of a simple symmetrical body. The 
fluid will be supposed to be incompressible, illimited in all directi- 
ons and adhering to the sides of the body. Neither the possibility 
of lability of the stationary (or laminary) currents will be attended 
to, nor peculiarities or differences occurring when the body deviates 
more or less from the spherical form or when we pass from the 
three-dimensional problem to the two-dimensional one. 
The body however is assumed to have in both cases its axis of 
symmetry parallel with the direction of the current and to possess 
no sharp edges. 
The character of the streaming is wholly governed by the nwmber 
of REYNOLDs: 
yv 
U is the velocity of the body with respect to the undisturbed 
fluid; d is a dimension of the body f. i. the greatest dimension 
perpendicular to the direction of the motion, u is the cinematic 
coëfficient of friction of the fluid (== u/e)*). At one limit, friction 
infinite or motion infinitely slow, A= 0, at the other limit, fluid 
without friction, R = oo. 
Remark. For shoriness sake the expression: absolute current is 
used here to indicate the current seen by an observer for whom 
the fluid at an infinite distance is at rest while the body is moving 
with the velocity U. The streamlines are displaced with the body; 
') This number of comparison was introduced by O. Reynorps in the investi- 
gation of the flow through tubes, Phil. Trans. Lond. 174, p. 935, 1883. It is of 
great importance for all model-experiments in hydrodynamics and in aerodynamics. 
See f.i. L. Barrstow, Applied Aerodynamics, London 1920, Ch. VIII (p. 372) and 
other new textbooks. 
