Flow control by distributed suction behind three-dimensional roughness element on the straight wing model

The paper is devoted to the close investigation of the flow over perforated suction section in the presence of the three-dimensional roughness element. Measurements were conducted over the surface of the straight wing with and without suction. It was shown that distributed suction allows diminishing the intensity of longitudinal structure. Also the boundaries of the effective suction usage were found.

Didactical Tool for Wing Weight Estimation in a Preliminary Aircraft Design Stage

Aircraft preliminary design requires a lot of complex evaluations and assumptions related to design variables that are not completely known at a very initial stage. Didactical activity becomes unclear since students ask for precise values in the starting point. A tentative in providing a simple tool for wing weight estimation is presented for overcoming these common difficulties and explaining the following points: a) the intrinsic iterative nature of the preliminary design stage, b) provide useful and realistic calculation for the wing weight with very simple assumption not covered by cumbersome calculations and formulas. The purpose of the paper is to provide a didactic tool to facilitate the understanding of some steps in estimating wing weight at the preliminary design level. The problems of identifying the main variables for the initial estimation is dealt with and specifi aspects that are usually hidden by the complexity of the involved disciplines and by the usual calculation methods applied in structural design are pointed out. The procedure is addressed to highlight main steps in wing weight estimation for straight wing weight to highlight the main steps in estimating the wing weight for a general aviation straight wing aircraft at the preliminary design stage. The effect of the main variables on the wing weight variation is also presented confirming well-known results from literature and design manuals.

Effect of Fuel Weight Distribution on the Aeroelastic Instability of Swept Wings

In this work, a study has been conducted to observe the influence of fuel weight distribution on the flutter characteristics of a high aspect ratio swept wing. In this paper, B777-200 wing model having a 34º sweptback angle is used as a baseline and two other models with the swept angles of 0º (straight wing) and 30º (forward swept) are considered in this study. Aeroelastic analysis is performed ranging from sea level up to 35,000 ft and the influence of in-flight fuel management in several flight altitudes is also investigated. There are four different fuel distribution model are investigated and it was found that some fuel distribution configuration are more critical which may lead to flutter. Moreover it was found that the flight altitude significantly affects the aeroelastic instability.

Aerodynamic Characteristics of a Straight Wing with a Spiroid Wingtip Device

Spiroid wingtip devices (WD) offer a promising way of improving the lift drag ratio of UAVs, but may on the other hand lead to negative aerodynamic interference of the wing with the WD and deterioration of the aerodynamic characteristics as compared to a wing without the WD. Determining the influence of the geometric parameters of a spiroid WD on aerodynamic wing characteristics, however, remains an understudied field. In our study, we investigated the influence of the following geometrical parameters on wing aerodynamic characteristics with WD: area, radius, camber angle, constriction, and pitch of the spiroid. We found that the positive effect of the WD is present at a relative radius > 0.05, as well as with an increase in the lift coefficient C L as a result of an increase in the proportion of inductive resistance. For example, with the Reynolds number Re = 2.1×105 for a rectangular wing with an aspect ratio θ = 5.12 equipped with a spiroid WD with =0.15 the quality gain is almost 10% at C L = 0.5, and at C L = 0.7 is almost 20% and at C L = 0.7 – almost 20% compared to a wing without WD. Moreover, we found that a change in the camber angle WD θ provides an increase in the derivative of the lift coefficient with respect to the angle of attack in the range from θ = 0° to θ = 130°. By changing the camber angle, it is possible to increase the lift drag ratio of the layout up to 7.5% at θ = 90° compared to θ = 0° at the Reynolds number Re = 2.1×105. From the point of view of ensuring maximum lift drag ratio and minimum inductive drag, the angle θ = 90° is the most beneficial.

Baccharis rectialata (Compositae: Astereae): a new species of carqueja from Uruguay

Baccharis rectialata (Compositae: Astereae), a new species of B. sect. Caulopterae from the grasslands in northeastern Uruguay is described. The new species is morphologically similar to B. crispa and can be differentiated by its straight wing margins, shorter involucres and pappus in staminate capitula. We provide a detailed morphological description, and information on the distribution, habitat, phenology, and conservation status. Additionally, we discuss the main differences between B. rectialata and other closely related and morphologically similar species, and provide a key for identification of subshrubs belonging to B. sect. Caulopterae occurring in Uruguay, as well as illustrations, images, and a distribution map of the new species.

Control of Nonlinear Stage of the Laminar-Turbulent Transition on an Airfoil by Distributed Suction through a Finely Perforated Surface

The results of experimental investigations of the influence of distributed suction through a finely perforated surface on the spatial development of perturbations of the straight wing boundary layer at the nonlinear stage of its evolution are presented in this article. It was found that distributed suction reduces the intensity of integral pulsations for natural disturbances by 90 times. A spectral analysis of disturbances showed a decrease in the intensity of high-frequency fluctuations in a narrow frequency band by two orders of magnitude for natural and forced disturbances generated by an external acoustic field. It was found that the distributed suction affects the average flow, namely, when the suction is on, the turbulent state of the boundary layer is eliminated, its separation near the trailing edge of the wing and the laminar flow is defined in the boundary layer.