Hydrodynamic characteristics of low aspect ratio vertical cambered otter board

For analyzing the hydrodynamic performance of low aspect ratio vertical cambered otter board at different angles of inclination and angle of attack,the lift coefficient(C_L),drag coefficient(C_D),buoyancy coefficient(C_Z)and lift to drag ratio(K)were calculated through the tank model experiment.The experimental results were as follows:(1)C_L and K showed a trend of first increasing and then decreasing with the increase of angle of attack(α),C_D reflected an upward trend with the increase of α;(2)With no angle of inclination,when α=30°,the max lift coefficient(C_Lmax)was 1.699,in this case C_D=1.140,K=1.490.When α=15°,the max lift to drag ratio(K_max)was 2.421,in this case C_L=1.120,C_D=0.463;(3)When the heeling angle(β)changed between -10°-10°,C_Lmax=1.816(α=25°,β=-10°),K_max=3.405(α=10°,β=-10°).The otter board had a certain buoyancy when β was -5° and -10°,the average buoyancy coefficient was 0.16 and 0.25 respectively,when α was between 10°-30°;(4)When the trim angle(γ)changed between -10°-10°,C_Lmax=1.823(α=25° or α=30°,γ=-10°),K_max=2.729(α=5°,γ=-5°).The otter board had a certain buoyancy when γ was -5°,-10° and 5°,the average buoyancy coefficient was 0.16,0.18 and 0.16 respectively,when α was between 10°-30°.It is suggested that the best working scope of angle of attack was between 15°-30°,in which case C_L>1.1 and K>1.45.Finally compared the hydrodynamic performance of different types of otter board,we provided a reference basis for the rational use and further development of the new types of otter board.