Experimental investigation of the effect of sail geometry on the flow around the SUBOFF submarine model inspired by the dolphin’s dorsal fin

ABSTRACT

The geometric shape of the submarine sail has a significant effect on the flow uniformity amount in the submarine impeller plane. In the present study, using a Hotwire and a five-hole probe, the downstream flow field for the three sail in the SUBOFF submarine model was investigated. Two of the sails have the same NACA0018 cross-section and height, one of which has a fillet on the leading-edge. The third sail has the NACA0018 cross-section which is shaped like a dolphin’s dorsal fin. In this study, the rotational field of the vortex downstream of the sail has been studied. The presence of fillets at the leading-edge of the sail significantly reduces the amount and intensity of the vortex. The sail with a dolphin’s dorsal fin geometry also has a significant effect on improving the flow quality. In addition, as the distance from the sail increases downstream, the wake becomes weaker.

KEYWORDS:

• Horseshoe vortex
• sail
• hotwire anemometer
• five-hole probe
• submarine

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclature

$X$	=	Axial (streamwise) coordinate
$Y$	=	Normal (vertical) coordinate
$Z$	=	Transverse (spanwise) coordinate
$L$	=	Overall length of the submarine model
$D$	=	Maximum diameter of the submarine model
$H$	=	Height of the sail
$l$	=	Length of the sail
$r_f$	=	Radius of leading-edge fillet
$R_{\max }$	=	Maximum radius of the submarine model
$R_0$	=	Local radius of the submarine model
$R{e}_L$	=	Reynolds number based on the length of model
$h_c$	=	The vertical distance of vortex centre from the model surface
$r$	=	The vertical distance of vortex centre from the model centreline
$V_x,V_y,V_z$	=	Velocity components in x, y, and z-direction, respectively
$U$	=	Mean velocity in the x -direction
$U_e$	=	Mean velocity at the edge of the wake
$V_0$	=	Velocity at the edge of the wake
$V_{\mathrm{\infty }}$	=	Freestream velocity
$u^{\mathrm{\prime }}$	=	Fluctuating velocity in the x-direction
$u_{\mathrm{rms}}$	=	Root mean square velocity in the x-direction
${\omega }_x$	=	Streamwise vorticity
$\mathrm{\Gamma }$	=	Circulation
$\gamma$	=	Dimensionless circulation
$P_t$	=	Total pressure
$q_{\mathrm{\infty }}$	=	Freestream dynamic pressure
$\alpha$	=	Angle of pitch (angle of attack)