Panel Discussion 



R. Goethals, was entitled Research on High-Speed Hydrofoils. The abstract of 

 this presentation is as follows: 



On March 1966 a blow-down water tunnel was started by the CEAT 

 for research sponsored by the "Direction des Recherches et Moyens 

 d'Essais". This research deals with supercavitating hydrofoils, 

 submarine propulsion, and air-cushion vehicles over water. In our 

 facility, water is driven out by compressed air from a tank and runs -. 

 in free surface channels (cross area 1-2 dm-^) with a maximum ve- 

 locity of 50 m./sec. The facility gets all the necessary equipment 

 for pressure and force measurements. 



The first research work was a theoretical and experimental study of 

 wall effect on force measurements. Especially for a test without 

 wall correction, we designed a bottom with parallel slots. Research 

 has been done on experimental studies of a hydrofoil family of finite 

 aspect ratio in supercavitating flow. We have studied some hydrofoil 

 groups corresponding to the same aspect ratio with various 

 planforms. 



We have initiated the study in unsteady range of two-dimensional 

 hydrofoils. We use the method of forced oscillations, and we are 

 looking for the rotary derivatives. 



Further, along with the "Centre de Calcul Analogique," we have 

 studied the design of a hydrofoil according to a given lifting pressure 

 distribution. The control tests are under way. 



Again, in spite of encouragement from the panel chairman, no discussion of 

 hydrofoil experimentation was offered, save a question by M. Tulin (Hydronau- 

 tics, Inc., Laurel, Md.) who inquired if this new facility at CEAT had been em- 

 ployed to study flutter problems as it possessed the unique advantage of high 

 speeds. The answer was no. 



M. Tulin next presented a summary of work done by Dr. M. Martin in sur- 

 veying methods for study of hydrofoil flutter. The conclusions reached were as 

 follows: 



It appears to be abundantly clear from the preceding survey that 

 the hydro-elastic behavior of hydrofoils in the low mass density 

 range is extremely sensitive to small changes in system parameters. 



Continuing research into obtaining a better understanding of viscous 

 and nonlinear effects on the unsteady forces and moments on oscillat- 

 ing lifting surfaces is needed. Careful observations with the aid of 

 dyes, motion pictures, and other flow visualization techniques, of 

 the flow field around oscillating hydrofoils should provide some of 

 the necessary ingredients for a lifting theory which corrects for the 

 nonsatisfaction of the Kutta condition, for nonplanar wake effects, 

 etc. 



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