Aiv-Sea Interactions ; Program at IMST 



begin to join together towards the end of the working section, leading 

 to a fully developed channel flow, are also apparent. 



As already mentioned (see III. 5), it is therefore necessary to 

 take steps to restrict the development of the lateral and upper bound- 

 ary layers. Tests performed under different conditions have proven 

 that the contemplated control method was efficient in this respect 

 (Pouchain [ 1970]). Fig. 13 illustrates typical results obtained for 

 various blowing rates (i.e. ratios of jet velocity to mean flow veloc- 

 ity), while sucking through a porous wall and blowing across a 15 

 millimeters height slot. The improvement in velocity distribution 

 is clear. As shown by Fig. 14, the turbulent intensity distribution is 

 also ameliorated. Some problems related to pressure perturbations 

 still have to be solved, but, on the whole, the method appears as 

 promising. 



8 m/s 



2000 



I I I I I ! \ I I ! I 



,.,^ I 1 



4000 



6.000 



8000 X„„ z„,„ 



280 



"T>-^-f-V-4->--VV>l 



Uj /U, = 1.31 



200 

 280 



No blowing 



With blowing Uj /U, = 1.05 



Fig. 13. Improvement in test section's flow by means of boundary 

 layer control: a) Flow configurations for three rates of 

 blowing; b) Variation of boundary layers' thickness. 



55 



