Experimental investigation of hydrodynamic characteristics of a submersible vehicle model with a non-axisymmetric nose in pitch maneuver

•Hydrodynamic coefficients of a submarine model with non-axisymmetric nose are investigated in a wind tunnel.•Flow visualization is used to explore the flow structures around the model at various pitch angles.•Reynolds number affects drag coefficient of the model up to a critical Reynold number.•The force measurements and visualized flow patterns revealed the strong effects of pitch angle.

Experimental investigation is conducted to study the behavior of a submarine model with a non-axisymmetric nose in pitch maneuver. The submarine model with all its appendages is tested in a wind tunnel at Reynolds number of 6.6×106, based on the model length, and a range of pitch angles −10°≤α≤+27°. The Reynolds number effects on drag coefficient are investigated for a range of Reynolds numbers between 4.7×106 and 8.0×106. By increasing the pitch angle, a continuous increase in drag and lift coefficients is observed. However, the measured pitching moment approaches to almost an asymptotic constant value when the pitch angle increased beyond +10°. Smoke flow visualization tests are also conducted to explore the details of flow structure around the submarine model for various values of pitch angles. The visualized flow revealed the formation of cross flow vortices and flow separation over the submarine model. These results show that the location of the flow separation for the non-axisymmetric nose shape is closer to the nose tip than the symmetric nose shape at high angle of attack.