“…Figure 2(a) shows a distinctive nonequilibrium phenomenon in vx distribution, i.e., the platformshaped distribution near the central plane. This platform-like phenomenon can also be found in reference [8], and we believe this phenomenon may be a typical nonequilibrium phenomenon in the strong-shear relaxation process. Thus, as the representative velocity component, vx is selected to be the main object in this study.…”
“…In group 1, Lz is fixed, and γ varies with uup accordingly. The settings in group 1 are given in table 1: Lz and uup are nondimensionalized by λ0 and a0 respectively; γ is nondimensionalized by λ0 and a0, i.e., γλ0/a0, which can describe the shear nonequilibrium effect as mentioned in reference [8]. Other settings remain the same as section 2.1.…”
Section: 31mentioning
confidence: 99%
“…Experiments conducted by Smoluchowski [1] and Knudsen [2] revealed some nonequilibrium phenomena (e.g., velocity slip and temperature jump) in the near-wall region of several mean free paths (λ) [3], and this region is usually called the Knudsen layer. The aerodynamic/aerothermal prediction of hypersonic vehicle relies on the momentum/energy transfer between the gas and wall, which involves the rarefied flow in the Knudsen layer, thus, some former works have been conducted to research the hypersonic Knudsen-layer flow [4][5][6][7][8][9][10].…”
A series of plane Couette flows of rarefied argon gas under different flowfield settings are simulated by the direct simulation Monte Carlo method. The relaxation process of strong shear nonequilibrium is systematically studied. The results show a qualitatively platform-shaped distribution of molecular streamwise velocity under the conditions of small wall spacing (roughly in the Knudsen layer), and large shear rate and wall speed. The analysis of this phenomenon will help understand the relaxation process of hypersonic Knudsen-layer flow and provide some references for future modelling research.
“…Figure 2(a) shows a distinctive nonequilibrium phenomenon in vx distribution, i.e., the platformshaped distribution near the central plane. This platform-like phenomenon can also be found in reference [8], and we believe this phenomenon may be a typical nonequilibrium phenomenon in the strong-shear relaxation process. Thus, as the representative velocity component, vx is selected to be the main object in this study.…”
“…In group 1, Lz is fixed, and γ varies with uup accordingly. The settings in group 1 are given in table 1: Lz and uup are nondimensionalized by λ0 and a0 respectively; γ is nondimensionalized by λ0 and a0, i.e., γλ0/a0, which can describe the shear nonequilibrium effect as mentioned in reference [8]. Other settings remain the same as section 2.1.…”
Section: 31mentioning
confidence: 99%
“…Experiments conducted by Smoluchowski [1] and Knudsen [2] revealed some nonequilibrium phenomena (e.g., velocity slip and temperature jump) in the near-wall region of several mean free paths (λ) [3], and this region is usually called the Knudsen layer. The aerodynamic/aerothermal prediction of hypersonic vehicle relies on the momentum/energy transfer between the gas and wall, which involves the rarefied flow in the Knudsen layer, thus, some former works have been conducted to research the hypersonic Knudsen-layer flow [4][5][6][7][8][9][10].…”
A series of plane Couette flows of rarefied argon gas under different flowfield settings are simulated by the direct simulation Monte Carlo method. The relaxation process of strong shear nonequilibrium is systematically studied. The results show a qualitatively platform-shaped distribution of molecular streamwise velocity under the conditions of small wall spacing (roughly in the Knudsen layer), and large shear rate and wall speed. The analysis of this phenomenon will help understand the relaxation process of hypersonic Knudsen-layer flow and provide some references for future modelling research.
“…Whether this unique phenomenon is just a coincidence for the current specific flying wing configuration or is universal, and whether this phenomenon depends only on the aircraft shape or also on the Mach number (Tu et al. 2021; Chen & Zhou 2021), Reynolds number, moment of inertia and other parameters need further research. Figure 3.Roll angle time history of the ( a ) flying wing (Case I), ( b ) 65° delta wing (Case II) and ( c ) 80° delta wing (Case III).…”
The flying wing is an aerodynamic configuration with high efficiency, but the lack of lateral-directional stability has always been an obstacle that limits its application. In this study, the wing rock motion of a 65° swept flying-wing aircraft is studied via wind tunnel experiments and numerical simulations at a low speed, and various unsteady motion phenomena are focused on. Both the experimental and numerical results show that the flying wing has a bicyclic
${C_l}$
–
$\phi $
hysteresis loop during its wing rock, different from the slender delta wing, rectangular wing, generic aircraft configuration, etc., which have a tricyclic hysteresis loop. This form of hysteresis loop implies a different energy exchange manner of the flying wing in the wing rock oscillation. Further analysis shows that the flying wing forms a unilateral leading-edge vortex (LEV) under a high roll angle, with its wing rock oscillation driven by the ‘vortex–shear-layer’ structure, which is different from that of slender and non-slender delta wings. Moreover, the quantitative dynamic hysteresis characteristics of the LEV's strength and location for the flying wing and the slender delta wing are also different. These results have proven the existence of a wing rock mode which is different from previous investigations, which enriches the understanding of self-induced oscillation. Present discoveries are also conducive to the aerodynamic shape design and flight manipulation of a flying-wing aircraft, which is significant for its wider application.
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