Experimental study of the effect of the LEX angle on the flow pattern of a diamond wing with an airfoil cross section

• Published in: Journal of visualization 2023-12, Vol.26 (6), p.1247-1262
• Main Authors: Hashemi, Mohammad Reza, Dehghan Manshadi, Mojtaba
• Format: Article
• Language: English
• Subjects: Angle of attack; Circuits; Classical and Continuum Physics; Computer Imaging; Engineering; Engineering Fluid Dynamics; Engineering Thermodynamics; Equivalence; Flow distribution; Flow velocity; Fluid dynamics; Fluid flow; Free flow; Frequency analysis; Heat and Mass Transfer; Kinetic energy; Low aspect ratio wings; Pattern Recognition and Graphics; Qualitative analysis; Regular Paper; Reynolds number; Sweep angle; Swept wings; Turbulence intensity; Turbulent flow; Upstream; Vision; Vortex breakdown; Vortices; Wind tunnels
• ISSN: 1343-8875; 1875-8975
• DOI: 10.1007/s12650-023-00942-2

In this research, the effect of the leading-edge extension (LEX) angle on the flow pattern upstream and downstream of the diamond wing has been investigated experimentally. The measurement of turbulence intensity by the hot-wire and the measurement of pressure on the wing by the five-hole probe in a closed-circuit wind tunnel at a free flow velocity of 12.5 m/s, which is equivalent to the Reynolds number of 202,000, have been carried out. In order to better observe the flow physics and qualitative analysis of the vortex flow, the smoke tunnel has been used. In this case, the free flow velocity is equal to 1 m/s equivalent to the Reynolds number of 16,000. The results indicated that the increase in the LEX sweep angle has led to an increase in the strength of the vortex, and with the increase in the angle of attack, the vortices have moved further away from the wing's upper surface. Also, the increase in the angle of attack shifts the breakdown location upstream, eventually reaching a complete wing stall. The use of LEX produced a vortex flow, which delayed the vortex breakdown by increasing the kinetic energy in the vortex core. The turbulence downstream of the wing is reduced with the breakdown delay. The frequency analysis showed that at the vortex core, the instantaneous velocity fluctuations are very high, which indicates an increase in turbulent kinetic energy. Graphical abstract