CFD INVESTIGATION ON THE HYDRODYNAMIC CHARACTERISTICS OF BLENDED WING UNMANNED UNDERWATER GLIDERS WITH EMPHASIS ON THE CONTROL SURFACES

Underwater Gliders are unique buoyancy propelled oceanographic profiling vehicles. Their speed and endurance in longitudinal motion are affected by the symmetry, sweep, dihedral angle and span of the control surfaces. In the low-velocity regime, these parameters can be varied to examine the flow around the glider. They also affect the lift-to-drag ratio (L/D) essential for the manoeuvring path in longitudinal and transverse motions. In this paper, the sweep angle of the main wing of a blended wing autonomous underwater glider configuration is varied as 10 degrees, 15 degrees, 30 degrees, 45 degrees and 60 degrees and the resulting hull forms are numerically simulated in the commercial software, STARCCM+. The main wing is a tapered NACA0018 section (taken as per the general arrangement requirement) with 1.5m chord at the root and 0.1m at the tip. The numerical model is validated using the CFD results of NACA0012 airfoil from Sun.C et al., 2015 [1]. The hydrodynamic forces are obtained by varying the angle of attack (a) of the body from -15 degrees to 15 degrees, for flow velocity of 0.4m/s. The hydrodynamic coefficients (lift-todrag ratios) and flow physics around the wing are analyzed to arrive at an optimum Lift-to-drag ratio for increased endurance.