![]() ![]() The rectangular cross-section of the test section measured 180 mm ×360mm, and the test section was covered on all sides with acrylic sidewalls. Figure 2 displays the full experimental setup. The turbulence intensity at the test section center was approximately 0.3% at 5.0 m/s. ![]() Four screens and a honeycomb were installed upstream of the contraction section for turbulence reduction, and the contraction ratio was 1/8. We conducted a series of experiments using an open-circuit low-speed wind tunnel at Kyushu University. The chord and span lengths of the test models are 80 mm and 180 mm, respectively.Īerodynamic force measurement and flow visualization Experimental setup and conditionsīoth test models are made of high-transmission stereolithography resins. Additionally, the flowfield around the airfoils were visualized by employing the smoke-wire method at Re = 23,000. Thus, the Reynolds number was changed from 23,000 to 60,000. In the flight sequence assumed for the Japanese Mars airplane, a Reynolds number less than 23,000 is a transitive condition. This study investigates the Reynolds number effect on the lift and drag characteristics of Ishii and SD7003 airfoils. Since low-Reynolds number aircrafts such as the Mars airplane fly at various altitudes and speeds, it is necessary to reveal how changes in the Reynolds number impact aerodynamic performance, especially lift characteristics. ![]() Although aerodynamic characteristics and flowfields around the airfoils at the specific Reynolds numbers have been studied, knowledge is still lacking about how the Reynolds number affects aerodynamic characteristics. Moreover, the lower surface of the airfoil shape does not significantly affect the flow structure around the airfoil because the attached flow is commonly maintained on the lower surface. The results revealed that the airfoil shape of the upper surface dominates both the formation of laminar separation bubbles and the transition to turbulence around the airfoil. Aono et al., 16 compared the aerodynamic characteristics of these two airfoils at Re = 23,000 via large-eddy simulations. In particular, Ishii airfoil is considered a likely main-wing airfoil candidate for the Japanese Mars airplane due to its high L/D around the cruising Reynolds number of 23,000. 14 These two airfoils have relatively high lift-to-drag ( L/D) ratios below Re = 70,000 where the low-Reynolds-number effect becomes pronounced 15 and are known as high-performance airfoils at low-Reynolds numbers. More practical asymmetric airfoils with aerodynamic characteristics have also been reported, including Selig-Donovan (SD) 7003 airfoil 13 and Ishii airfoil. The behavior of separation bubbles on representative symmetric airfoils, such as NACA0012 airfoil 8, 9 and flat plate, 10–12 has been well investigated. 7 Therefore, aerodynamic predictions based on physical properties are essential for high-performance wing design of low-Reynolds number aircrafts. This type of physical phenomenon strongly depends on airfoil shape, Reynolds number, and angle of attack, and causes non-linear lift curves as well as influences the Reynolds number effect on aerodynamic performance. In such a low-Reynolds-number range, the formation and bursting of separation bubbles occur on the wing surface. ![]() 2–5 A Japanese research group has already developed the first prototype for the Mars airplane with a fixed wing, which performed a high-altitude flight-demonstration test in 2016. 1 Recently, a new application for low-Reynolds-number aircraft has emerged to enable aerial exploration on Mars this so-called Mars airplane has been considered and discussed for a several years in Japan. The aerodynamic performance of low-Reynolds number airfoils in chord Reynolds numbers ( Re) less than 10 5 is important for various engineering applications, such as micro air vehicles, unmanned air vehicles, and low-speed/high-altitude aircrafts. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |