Abstract
The induced and profile drag coefficients of a wing are typically determined through a complex experimental technique, such as wake surveying. Such a technique requires measurement of all three orthogonal components of the downstream velocity to find the components of drag, which results in the necessary usage of a sophisticated and costly measurement device, such as multi-hole pressure probe. However, in this paper data is presented which demonstrate that the relative changes in the induced and profile drag coefficients can largely be determined through the sole measurement of the downstream, streamwise velocity. To demonstrate this, the induced and profile drags of two NACA 0021 wings, one with a smooth leading edge and the other wing a tubercled leading edge for comparison, are determined through the measurement of the three orthogonal velocities. The downstream, streamwise velocity distribution of each wing is then constructed and relationships can be determined. The wings were surveyed at 3°, 9°, and 12°. It has been found that the relative magnitude of the profile drag coefficient can be found for all considered angles of attack, while the relative magnitude of the induced drag coefficient can be found at 9° and 12°. These findings produce an innovative, simpler, and more cost effective experimental technique in determining the components of drag of a wing, and reduces the burdensome requirement of a sophisticated measurement device for such an experiment. Further investigation is required to determine the induced drag at 3°.
Highlights
The induced and profile drag coefficients of a wing are typically determined through a complex experimental technique, such as wake surveying
Such a technique requires measurement of all three orthogonal components of the downstream velocity to find the components of drag, which results in the necessary usage of a sophisticated and costly measurement device, such as multi-hole pressure probe
A typical method used to investigate the induced and profile drags of a wing is to perform a wake survey, whereby the wing is placed in a wind tunnel and a plane downstream of the wing is designated as the “wake plane”, as detailed in figure 1
Summary
A typical method used to investigate the induced and profile drags of a wing is to perform a wake survey, whereby the wing is placed in a wind tunnel and a plane downstream of the wing is designated as the “wake plane”, as detailed in figure 1. This wake plane is divided into a grid of nodes and the three orthogonal velocities are measured at each node. By reducing the number of parameters that must be measured a simpler methodology that can be utilised by a greater number of researchers, may result, thereby accelerate the wing design process
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