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Introduction of Supersonic Flight
Published in Rose G. Davies, Aerodynamics Principles for Air Transport Pilots, 2020
When μ < σ, as shown in Figure 11.14 (a), the leading edge of the swept wing would be likely in supersonic flow (chordwise). Oblique shockwaves would be formed at the leading edge close to the wing root. After an oblique shockwave airflow is still supersonic at the leading edge of the wing, so a series of shockwaves can be formed along the leading edge of the swept wing as shown in Figure 11.15. Therefore, the shock drag of a swept wing would increase considerably at a high Mach number. The tip effect in a supersonic leading edge on a swept wing would reduce lift and make a low L/D ratio at a high Mach number.
Boeing and the Cold War: From the Jet Bomber to the Civil Transport
Published in Philip K. Lawrence, David W. Thornton, Deep Stall, 2017
Philip K. Lawrence, David W. Thornton
Recognizing the potential importance of these discoveries for the B-47 project, Schairer had sent drawings and notes of his impressions to Seattle, where the B-47 design team immediately began to test the new design in the tunnel, (Rodgers, 1995, p. 98). With the safe arrival of Schairer's urgent communication from Germany, Boeing engineers realized the full significance that the rapid and effective application of such a design might have for the company, (Irving, p. 83). Within a week of receiving Schairer's letter, Boeing engineers had a crude swept wing in the tunnel, and 'at once they could see the significance for the XB-47', (Irving, p. 86). The radical wing would allow the plane to approach closer than ever to the speed of sound, and with speed came improved fuel-efficiency and increased range: 'The swept wing would render the jet engine more efficient at the bomber's optimum performance', (Irving, p. 87). Therefore, armed with top-secret military information and equipped with the industry's most advanced test facilities, Boeing established itself as the vanguard of the jet age: 'Right at the start, Boeing jumped out to a lead it never relinquished, using revolutionary development techniques and producing a design that was radically different from the designs of its competitors', (Rodgers, 1996, p. 93).
Drag force and drag coefficient
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
In general, a shock wave is always required to bring supersonic flow back to subsonic regime. In a subsonic free stream, whenever the local Mach number becomes >1 over the surface of a wing or body, the flow must be decelerated to a subsonic speed before reaching the trailing edge. If the surface could be shaped such that the surface Mach number is reduced to 1 and then decelerated subsonically to reach the trailing edge at the surrounding free-stream pressure, there would be no shock wave and no shock drag. A major goal of transonic airfoil design is to reduce the local supersonic Mach number to as close to 1 as possible before the shock wave. One of the main functions of sweep angle in a swept wing is to reduce wave drag at transonic and supersonic airspeeds.
Static and free vibration analyses of functionally graded porous skew plates reinforced by graphene platelet based on three-dimensional elasticity theory
Published in Waves in Random and Complex Media, 2022
Xiaoling Shi, Ruoqi Suo, Lingqin Xia, Xinping Yu, Masoud Babaie
From the early 1950s, researchers investigated the static and vibration behavior of skew plates, since there was a need to study their mechanical behavior due to the new swept-wing aircraft concept [59]. Skew plates are also extensively applied in other engineering structures, such as skew bridge decks, skew floor slabs, vehicle bodies, and ship decks. Many researchers have employed various methods to analyze the static and free vibration behavior of skew plates some of which are mentioned here. Upadhyay and Shukla [60] investigated the non-linear static and dynamic behavior of skew sandwich plates based on HSDT and von-Karman’s non-linearity employing finite double Chebyshev series. Asemi et al. [61] employed the 3D finite element method to study the static and dynamic analyses of FGM skew plates. Joodaki and Joodaki [62] presented a semi analytical solution to study the static behavior of thin skew plates on Winkler and Pasternak foundations based on CLPT. Katariya [63] studied the bending and vibration behavior of skew sandwich plates based on HSDT and FEM.
Calculation of flutter and dynamic behavior of advanced composite swept wings with tapered cross section in unsteady incompressible flow
Published in Mechanics of Advanced Materials and Structures, 2019
Although the primary motivation for a positive sweep angle is to improve aircraft performance by increasing the critical flight speed, sweep angle has important effect on the aeroelastic behavior of the aircraft wing as well. There are two ways in which the sweep influences the aeroelastic behavior. One is the loss of aerodynamic effectiveness (Un = U∞cos Λ) and the second effect is the influence of bending and torsion slopes on the effective angle of attack and downwash velocity, which leads to an aeroelastic bending–torsion coupling. This coupling has an important influence on both divergence and load distribution and makes the forward swept wing more susceptible to divergence. Figure 24 displays the effects of different sweep angle on response. The response for the sweep angle Λ = −40°, 0°, 40° is considered. As the sweep angle increases, the response amplitude for bending mode also increases. Likewise, the time needed for response damping also increases.
Active aeroelastic wing application on a forward swept wing configuration
Published in Engineering Applications of Computational Fluid Mechanics, 2019
Rongrong Xue, Zhengyin Ye, Kun Ye
The forward swept wing (FSW), which is a challenging configuration, is subject to aeroelastic torsion divergence problems at high dynamic pressure (Rongrong, Zhengyin, & Gang, 2016; Weisshaar, 1979). The aeroelastic torsion divergence problem is caused by the aerodynamic center (AC) always positioning in front of the structure stiffness center, which results in a head-up twist on the FSW. This characteristic increases the local angle of attack (AOA), and generally generates more lift and aeroelastic torsional deformation until the structure fails because of the uncontrollable aerodynamic forces. This feature seriously restrains the application of FSWs on commercial airplanes.