On existence of two-dimensional nonstationary flows of an ideal incompressible liquid admitting a curl nonsummable to any power greater than 1

1992 ◽  
Vol 33 (5) ◽  
pp. 934-937 ◽  
Author(s):  
A. B. Morgulis

The present note extends the theory of fish propulsion by E. H. Smith & D. E. Stone, taking into account the wake effect which was not discussed in the original paper. The motion of a fish is simulated by a flexible plate of infinitesimal thickness, infinite span, and constant chord length, moving in the two-dimensional flow field of an ideal incompressible liquid. The perturbation velocity potential for the flexible plate is obtained by solving the Laplace equation in an elliptic cylindrical co-ordinate system, while the wake velocity potential follows from the application of a method which is due to Theodorsen. The results are shown to be identical with those derived previously by Siekmann. A simple example is given for illustration and results predicted by theory are compared with experimental data.


2007 ◽  
Vol 572 ◽  
pp. 59-85 ◽  
Author(s):  
J. M. OLIVER

The theory of Wagner from 1932 for the normal symmetric impact of a two-dimensional body of small deadrise angle on a half-space of ideal and incompressible liquid is extended to derive the second-order corrections for the locations of the higher-pressure jet-root regions and for the upward force on the impactor using a systematic matched-asymptotic analysis. The second-order predictions for the upward force on an entering wedge and parabola are compared with numerical and experimental data, respectively, and it is concluded that a significant improvement in the predictive capability of Wagner's theory is afforded by proceeding to second order.


1954 ◽  
Vol 50 (1) ◽  
pp. 125-130 ◽  
Author(s):  
W. R. Dean

1. In §§ 2–4 of this paper approximate expressions are found for the stream function and pressure in the steady two-dimensional motion of viscous incompressible liquid past a fixed parabolic cylinder; exact expressions for the stream-function and pressure in a perfect liquid are derived as limits in § 5.


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