Determination of Aerohydrodynamio Performance of ACVs 



side force and yawing moment with respect to the yaw angle /3 for 

 /9 = which are necessary for the calculation of ACV movement in 

 the horizontal plane. The aerodynamic forces are related to the pro- 

 duct of the velocity head & and centerplane area S, while the moment 

 is related to^SL where L is the model length. The moment is calcu- 

 lated with respect to the middle of the hull length. 



As is seen from the Table 1, the resistance is mainly influen- 

 ced by the forebody form. With the change of relationship -ktL from 

 0. 5 to 2 the resistance factor decreases by 30-40 per cent. The in- 

 fluence of the stern form on the resistance is less important, which is 

 due to separation effects and the formation of the dead zone at the 

 stern. The angle of run ranging from ^ ■ = to 2 leads to a decrea- 

 se in resistance only by 10 per cent. 



It is known that the heave stability of the ACV s mainly de- 

 pends on the sign and value of the derivative m ". The minimum va- 

 lue of the derivative m " which is favourable from the viewpoint of 

 stability of motion occurs for the models 7 and 8 with the smallest 

 values of angles of run and entrance. As is seen from the Table, the 

 bow elongation results in increasing the destabilizing moment m , 

 so the requirements of minimum values for the coefficients of resis- 

 tance and yawing moment are rather inconsistent. Since the required 

 value of the derivative m P can always be obtained due to the fitting 

 of vertical stabilizers without noticeable increase in resistance, the 

 hulls with elongated bows and blunt sterns appear to be the most ad- 

 vantageous. 



For the approximate estimates of the ACV s aerodynamic 

 characteristics at the initial stages of designing the theoretical me- 

 thods are of interest. The method is developed for the calculation of 

 both the total and distributed aerodynamic characteristics of ACV 

 hulls with flat sterns at different yaw angles and angular velocity*^) y 

 depending upon the forebody forms and paramenters — and — « . 



The method is based on replacing the hull of the ACV by a 

 vortex surface which extends beyond the hull for modelling the vor- 

 tex trace effect (figure 1). The free water surface is simulated by an 

 image body so that in fact consideration is given to a model with a 

 double height H. The transverse vortices are directed parallel to 

 the lines forming the flat stern contour. The longitudinal vortex which 

 leaves the body from stern contour corners has the density equal to 

 the difference between the densities of vertical and horizontal vorti- 

 ces replacing the contour. Longitudinal vortices arranged in the deck 

 plane are parallel to the longitudinal axis of the hull. Calculations 



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