![]() These UAVs have take-off masses from 15 kg up to about 700 kg, and they are often used for reconnaissance, surveillance, and search and rescue missions. #Skin friction coefficient skin#A careful literature review revealed that neither an equivalent skin friction factor nor wetted area correlations have yet been derived for short-to-medium range UAVs. The empirical skin friction coefficient depends on the aircraft category to account for their specific aspects. In this method, the complete parasitic drag of an aircraft is based on an equivalent skin friction coefficient and its multiplication with the wetted area of the airframe. The parasitic drag has a direct effect on flight performance prediction and propulsion system sizing.Ī well-known approach is to use an equivalent skin friction method. One of these critical models is responsible for estimating the new aircraft's parasitic drag. The accuracy of such underlying models is of critical importance as their outcomes drive the design to convergence. The design routine is divided into several sub-models that are responsible for estimating the new aircraft’s properties, including weight, propulsion, cost, or aerodynamics. The improved parasitic drag estimation yields a much heavier unmanned aircraft when compared to the sizing results using available drag data of manned aircraft.Ĭonceptual aircraft design is a multidisciplinary optimization problem. It is used to initially size an unmanned aircraft for a typical reconnaissance mission. The new equivalent skin friction coefficient accounts for these effects and is significantly higher compared to other aircraft categories. These components are responsible for almost half of an unmanned aircraft’s total parasitic drag. The UAV’s parasitic drag is significantly influenced by the presence of miscellaneous components like fixed landing gears or electro-optical sensor turrets. The aircraft is simulated using a validated unsteady Reynolds-averaged Navier Stokes approach. The new coefficient is derived from an aerodynamic analysis of ten different unmanned aircraft used for surveillance, reconnaissance, and search and rescue missions. The skin friction coefficient varies with age, gender and body site, and positively correlates with stratum corneum hydration on some body sites.The paper presents the derivation of a new equivalent skin friction coefficient for estimating the parasitic drag of short-to-medium range fixed-wing unmanned aircraft. In contrast, in males, the skin friction coefficient was positively correlated with stratum corneum hydration on the forehead and the dorsal hand skin (p < 0.05 and p < 0.0001, respectively). On the canthus and the dorsal hand skin of females, a positive correlation was found between skin friction coefficient and stratum corneum hydration (p < 0.001 and p < 0.0001, respectively). Skin friction coefficients on some body sites were higher in females than in age-matched males in some age groups. In the males, the skin friction coefficient on the dorsal hand skin gradually increased from 0 to 40 years of age, and changed little afterward. In the females, the maximum skin friction coefficients on both the canthus and the dorsal hand skin were observed around the age of 40 years. A Frictiometer FR 770 and Corneometer CM 825 (C&K MPA 5) were used to measure the skin friction coefficient and stratum corneum hydration, respectively, on the dorsal surface of the hand, the forehead and the canthus. In the present study, we assess the skin friction coefficient in a larger Chinese population.Ī total of 633 subjects (300 males and 333 females) aged 0.15-79 years were enrolled. However, the characteristics of the skin friction coefficient in different genders and age groups have not yet been well established. Studies have demonstrated that some cutaneous biophysical properties vary with age, gender and body sites. ![]()
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