Hydrodynamic Problems Solved by Rheoelectric Analogies 



This property, accurate in two-dimensional situations, is only approximative 

 in three-dimensional cases. In adopting it for the latter, we are at least assured 

 that the balance of the total resistance will always be respected. For a flat wing 

 placed at incidence a the above expression becomes even more simple, since 



d^/dx = a: „- ■ 



Ce(y) - ^ 



The solution of the problem is then to impose the overall boundary condi- 

 tions of the function i', as indicated in Fig. 20. Because of the function of the 

 transformer, the zero- flow condition is automatically fulfilled; the potentiome- 

 ter Pi allows the Joukowski condition on the trailing edge, and the potentiome- 

 ter P2 regulates, by successive approximations, the condition of equality between 

 the potential difference Cj(y) = 4>i{y) - 4> (y) and the value of the resistance cal- 

 culated at the same section in far downstream. 



«p=0 



9*=^ 



' F=si<x.y, ^>r=o *-=*. 



dn a 



ax 



Upper Surface 



m 



m\ 



miiiiiiiLLiiilLmiiiiiu 



iiiiiunnuim 



Lower Surface 

 Fig. 20 - Overall boundary conditions of the function 



Figure 21 shows the shape of the cavity thus obtained for a flat wing of 

 trapezoidal planform, with a strut of the same width as the central chord, for 

 incidence a = 5°. The calculated lift coefficient is Cl = 0.12 and the lift- drag 

 ratio L/D = 11.5, for a reduced immersion d/s - 0.4. The high value of the 



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