Determination of Aerohydrodynamic Performance of ACVs 



with a mechanism of compensating for the model inertia forces and 

 with an electric harmonic analyzer for automatically defining and 

 recording the signal constant components which are proportional to 

 the required rotational and translational derivatives. The model is 

 mounted upside-down (figure 3) on two supporting pillars which make 

 reciprocating oscillations with arbitrary shift in phases with respect 

 to each other. Each pillar is supplied with a strain gauge which ser- 

 ves as a connecting link between the model and the oscillating pillar. 



The distances to the ground board h; the trim angle *+* and 

 their first-order and second-order time derivatives h, <y , h, ly are 

 adopted as kinematic parameters defining the model aerodynamic 

 characteristics in the longitudinal plane. In linear approximation the 

 expansion of the vertical force or longitudinal moment as a series in 

 kinematic parameters has the form 



R = R (h ,4/ ) + R h (h , y ) . h + R^(h , ^ )y+ R h (h ,y )h ... 

 000 00 00 00 



(2) 



+ R^(h y ) y + R h (h , y ) h + R^(h , y ) CL 



0,0 00 00 



where h Q 14; are mean values of height and trim in respect of which 

 the values h and 141 are changed. 



The tests are carried out for two types of motion : transla- 

 tory and angular harmonic oscillations of the model where, with the 

 results of the model static tests also used, all the derivatives entering 

 into equation (2) can be determined. The values of rotatory and trans, 

 latory derivatives of the vertical force and the longitudinal moment 

 are determined and they are transformed to a dimensionless form 

 through dividing these by the model weight G or by the product GL. 



v-t M * = ^t (3) 



As the dimensionless kinematic parameters the following factors are 

 used : 



57,3 ' L3g 



3 * Qo "F- h Q2 ° 7jT_ ^ Q o 



Y " L 2 g L^ g2 L4 g2 



265 



(4) 



