Field observation and numerical analysis of a rotating pipe in flight

Abstract

The present purpose is to reveal the mechanism of a flying pipe from an aerodynamic point of view. At first, we conduct field observations of a flying pipe using a pair of high-speed video cameras, together with three-dimensional motion analyses. In addition, we conduct numerical analyses by a finite difference method based on the MAC scheme. As a result, the observed orbit is approximated to be not an obvious parabolic curve but rather a straight line, after an initial instable and complicated curve. The stable flight with this approximately-straight orbit suggests the importance of aerodynamics in flying mechanism. More specifically, the model is in an unstable and complicated flight during an initial flight, afterwards becomes in a stable and approximately-straight flight. In the initial instable and complicated flight, the model flies fluctuating its posture upward, downward, left-ward and right-ward. As flight distance increases, the absolute value and the amplitude of moment becomes small to zero. During such a decaying and stabilising process, the gyroscopic effect plays a primary role balancing not angular acceleration of the model but aerodynamic fluid moment. In the stable and approximately-straight flight, the flow in the stable and approximately-straight flight is nearly the velocity-potential one, and accompanies very-small drag force. And, we could ignore the influence of model's rotation upon the flow and the orbit. In this context, the model's rotation is only to stabilise its posture, and gives negligible contribution upon its aerodynamics.

Theoretical and Experimental Investigation into the flight of an X-Zylo

“…This work aims to resolve this issue by using a dedicated launch mechanism for better control on the initial flight parameters. The X-Zylo itself was also subject of former investigations [4,5], but in less depth than in the present study. Future applications could involve the optimization of such toys as well as potential insights in annular airfoil technology experimentally used for coleopters in the past.…”

“…For the lift slope the deviation to the CFD results is more than 180%, also the viscous drag is only half of what was computed (42% for k-ω-SST, 56% for Transition SST). The approach by Hirata, et al [4] also underestimates drag and lift forces. When comparing the sole data point given to the Fluent simulation a difference of 40% for the lift force (both models) and 41% (k-ω-SST) or 27% (Transition SST) difference for the drag force is calculated.…”

“…While the CFD results use a non-rotating X-Zylo with wavy trailing edge, the other sources are calculated for a thin ring wing with length 54.5 mm and diameter 97 mm. As Hirata, et al [4] calculated the drag and lift coefficient of a simplified model with a length of 60 mm and a diameter of 100 mm using motion analysis, the values are scaled accordingly to fit the real dimensions of an X-Zylo. It also has to be mentioned that source [4] only lists a single value for C D and C L at an AoA of 2°.…”

“…As Hirata, et al [4] calculated the drag and lift coefficient of a simplified model with a length of 60 mm and a diameter of 100 mm using motion analysis, the values are scaled accordingly to fit the real dimensions of an X-Zylo. It also has to be mentioned that source [4] only lists a single value for C D and C L at an AoA of 2°. Therefore this data is not listed in figure 10.…”

“…It has to be noted that when thrown by a human, the initial condition with 0°AoA is not perfectly met, additionally the ring wobbles a lot and stabilizes only after a short amount of time [4]. This makes the flight hard to predict since the launch conditions are hard to measure accurately.…”