Smoke visualization over a spinning cone at angle of attack in flight

Smoke visualization over a spinning truncated cone at angle of attack is carried out to study qualitatively the salient features of the flow field. A twisted wire pair is used for generating equally spaced smoke streaks in vertical planes. Detailed images of flow patterns over a spinning cone with a half angle $\theta_c = 30^\circ$ and a base diameter of $20\,cm$ are captured with a high speed camera. The rotational speed of the cone is set at $\Omega = 5\,revs/s$, the axial flow at $U_\infty = 1\,m/s$, and the angles of attack up to $36^\circ$. The Reynolds number, based on the cone size, is $\sim 10^4$. The analytic description of the axisymmetric potential flow over a fixed cone at zero incidence is reviewed for comparison of the flow field outside the boundary layer. Good agreement in the streakline patterns between experiment and theory is observed near the tip of the cone at zero incidence for both fixed and rotating cases. At angle of attack, the streakline patterns outside the boundary layers are similar for both fixed and rotating cases, including evidence of vortex formation. Streakline patterns in the boundary layers reflect the effect of rotation of the surface.