Wu 



thrust by legs 

 i thrust by arms 



Fig. Dl - Results of tests on swimmers 



DISCUSSION 



H. Schwanecke 



Versuchanstalt fur Sckiffbau 



Hamburg, Germany 



The paper presented by Professor Wu is excellent, as we could expect. May 

 I refer to the problem of fish propulsion. It has been discussed many times if 

 there is any mechanical propulsion device by which an arbitrary sea vehicle can 

 be driven at a relatively high speed and at a high propulsive efficiency as it is 

 with certain kinds of fishes. Moreover, this device should not be too compli- 

 cated in order to obtain a high mechanical efficiency. 



Some years ago, a propulsive device named "well-propeller" was proposed 

 by Schmidt. Schmidt has also performed some experiments in air on this de- 

 vice. Unfortunately, I received the experimental results too late to refer to 

 them. The well-propeller is a combination of two foils. One performs a trans- 

 latory motion in such a way that every point of it describes a circle with the 



1202 



