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Multiscale simulation of rarefied gas dynamics via direct intermittent GSIS-DSMC coupling 通过 GSIS-DSMC 直接间歇耦合对稀薄气体动力学进行多尺度模拟
IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-09-10 DOI: 10.1186/s42774-024-00188-y
Liyan Luo, Lei Wu
The general synthetic iterative scheme (GSIS) has proven its efficacy in modeling rarefied gas dynamics, where the steady-state solutions are obtained after dozens of iterations of the Boltzmann equation, with minimal numerical dissipation even using large spatial cells. In this paper, the fast convergence and asymptotic-preserving properties of the GSIS are harnessed to remove the limitations of the direct simulation Monte Carlo (DSMC) method. The GSIS, which leverages high-order constitutive relations derived from DSMC, is applied intermittently, which not only rapidly steers the DSMC towards steady state, but also eliminates the requirement that the cell size must be smaller than the molecular mean free path. Several numerical tests have been conducted to validate the accuracy and efficiency of this hybrid GSIS-DSMC approach.
一般合成迭代方案(GSIS)在稀薄气体动力学建模中的功效已得到证明,在该方案中,波尔兹曼方程经过数十次迭代后即可得到稳态解,即使使用大空间单元,数值耗散也很小。本文利用 GSIS 的快速收敛和渐近保留特性,消除了直接模拟蒙特卡罗(DSMC)方法的局限性。GSIS 利用从 DSMC 派生的高阶构成关系,间歇性地应用,不仅能快速引导 DSMC 进入稳态,还能消除单元大小必须小于分子平均自由路径的要求。为了验证这种 GSIS-DSMC 混合方法的准确性和效率,我们进行了多次数值测试。
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引用次数: 0
On the effects of non-zero yaw on leading-edge tubercled wings 关于非零偏航对前缘块状翼的影响
IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-09-05 DOI: 10.1186/s42774-024-00182-4
T. H. New, S. Mandrà
Steady-state numerical simulations were conducted to capture the aerodynamic characteristics and flow patterns resulting from a tubercled and non-tubercled wing subjected to various combined pitch and yaw conditions at $$Re=1.8 times 10^{5}$$ . Pitch angle ranged from $$0^{circ }$$ to $$25^{circ }$$ , while two different yaw angles of $$10^{circ }$$ and $$30^{circ }$$ were used. Results show that $$10^{circ }$$ yaw angle does not impact upon the lift and drag characteristics significantly, while a $$30^{circ }$$ yaw angle leads to substantial lift and drag losses. Additionally, the tubercled wing continues to confer favourable stall-mitigating characteristics even for the larger yaw angle. Finally, despite skewing the flow structures significantly, the $$30^{circ }$$ yaw angle also reduces the formations of bi-periodic flow structures, flow separations and recirculating regions along the leading-edge tubercles, suggesting potentially better flow stability and controllability. • Steady-state numerical study is conducted on NACA 634021 baseline and tubercled wings • Two yaw angles of $$10^{circ }$$ and $$30^{circ }$$ are used together with pitch angles from $$0^{circ }$$ to $$25^{circ }$$ • Results show $$10^{circ }$$ yaw angle has minimal impact on the lift and drag characteristics, while $$30^{circ }$$ yaw angle reduces both lift and drag levels significantly • Larger yaw angle leads to more skewed flows, as well as reduced flow separations and recirculating regions • Larger yaw angle also suppresses bi-periodic flow behaviour in tubercled wings, suggesting better flow stability and controllability
我们进行了稳态数值模拟,以捕捉在 $$Re=1.8 times 10^{5}$ 条件下受各种俯仰和偏航组合条件影响的带瘤和不带瘤机翼所产生的气动特性和流动模式。俯仰角从 $$0^{circ }$ 到 $$25^{/circ}$,而偏航角为 $$10^{circ }$ 和 $$30^{circ }$。结果表明,10^{circ }$ 的偏航角对升力和阻力特性的影响不大,而 30^{circ }$ 的偏航角会导致升力和阻力的大幅损失。此外,即使偏航角越大,块根翼仍能保持良好的失速抑制特性。最后,尽管30^{circ }$$偏航角显著歪斜了流动结构,但也减少了沿前缘小瘤形成的双周期流动结构、流动分离和再循环区域,这表明流动稳定性和可控性可能会更好。- 对 NACA 634021 基准翼和带瘤翼进行了稳态数值研究 - 使用了 $$10^{circ }$ 和 $$30^{circ }$ 两种偏航角以及从 $$0^{circ }$ 到 $$25^{circ }$ 的俯仰角 - 结果表明 $$10^{circ }$ 偏航角对升力和阻力特性的影响最小,而 $$30^{circ }$ 偏航角对升力和阻力特性的影响最大、偏航角越大,流动越倾斜,流动分离和再循环区域越小 - 偏航角越大,还能抑制管状机翼中的双周期流动行为,表明流动稳定性和可控性越好
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引用次数: 0
Wind-resistant design theory and safety guarantee for large oil and gas storage tanks in coastal areas 沿海地区大型油气储罐的抗风设计理论与安全保障
IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-08-27 DOI: 10.1186/s42774-024-00184-2
Bin Huang, Xijie Liu, Zhengnong Li, Dabo Xin, Jinke Liu, Shujie Qin, Tianyin Xiao, Jinshuang Dong
Large oil and gas storage tanks serve as crucial industrial energy infrastructures, which are usually thin-walled steel structures with large volumes and light weights, and they are sensitive to wind loads. Under the influence of strong winds or typhoons, large oil and gas storage tanks may suffer wind-induced damage, resulting in the leakage of gas or liquid inside the tanks, posing hazards to the ecological environment and public safety. Therefore, it is of great theoretical and engineering significance to research the wind resistance of large oil and gas storage tanks. This paper provides a comprehensive review of key issues in wind resistance for large oil and gas storage tanks, including characteristics of flow around circular cylinders, wind effects on structures with circular cross-sections, near-surface wind field characteristics, wind effects on large oil and gas storage tanks, wind-induced interference effects, structural dynamic characteristics, wind loads and wind-induced response calculations, multiple load effects, and wind-induced vibration control. The deficiencies of current research are summarized. The prospects for research on the design theory and safety assurance of large oil and gas storage tanks are presented through various methods, including field measurements of near-surface wind fields and wind effects, wind tunnel tests utilizing aeroelastic models, numerical simulations involving fluid–solid coupling, theoretical analysis, and machine learning.
大型油气储罐是重要的工业能源基础设施,通常为薄壁钢结构,体积大、重量轻,对风荷载敏感。在强风或台风的影响下,大型油气储罐可能会受到风力的破坏,导致罐内气体或液体泄漏,对生态环境和公共安全造成危害。因此,研究大型油气储罐的抗风能力具有重要的理论和工程意义。本文全面综述了大型油气储罐抗风性能的关键问题,包括圆柱体周围流动特性、风对圆形截面结构的影响、近地面风场特性、风对大型油气储罐的影响、风引起的干扰效应、结构动力特性、风荷载和风引起的响应计算、多重荷载效应以及风引起的振动控制。总结了当前研究的不足之处。通过各种方法,包括近地面风场和风效应的实地测量、利用空气弹性模型进行的风洞试验、涉及流固耦合的数值模拟、理论分析和机器学习,介绍了大型油气储罐的设计理论和安全保证的研究前景。
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引用次数: 0
Open-jet facility for bio-inspired micro-air-vehicle flight experiment at low speed and high turbulence intensity 用于生物启发微型空气飞行器低速高湍流强度飞行实验的开放式喷气设施
IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-08-02 DOI: 10.1186/s42774-024-00180-6
Zhifeng Liu, Yue Yang
Bio-inspired micro-air-vehicles (MAVs) usually operate in the atmospheric boundary layer at a low Reynolds number and complex wind conditions including large-scale turbulence, strong shear, and gusts. We develop an open jet facility (OJF) to meet the requirements of MAV flight experiments at very low speed and high turbulence intensity. Powered by a stage-driven fan, the OJF is capable of generating wind speeds covering 0.1 – 16.8 m/s, with a velocity ratio of 100:1. The contraction section of the OJF is designed using an adjoint-driven optimization method, resulting in a contraction ratio of 3:1 and a length-to-diameter ratio of 0.75. A modularized design of the jet nozzle can produce laminar or high-turbulence wind conditions. Flow field calibration results demonstrate that the OJF is capable of producing a high-quality baseline flow with steady airspeed as low as 0.1 m/s, uniform region around 80% of the cross-sectional test area, and turbulence intensity around 0.5%. Equipped with an optimized active grid (AG), the OJF can reproduce controllable, fully-developed turbulent wind conditions with the turbulence intensity up to 24%, energy spectrum satisfying the five-thirds power law, and the uniform region close to 70% of the cross-sectional area of the test section. The turbulence intensity, integral length scale, Kolmogorov length scale, and mean energy dissipation rate of the generated flow can be adjusted by varying the area of the triangular through-hole in the wings of the AG.
受生物启发的微型空气飞行器(MAV)通常在低雷诺数和复杂风况(包括大尺度湍流、强切变和阵风)的大气边界层中运行。我们开发了一种开放式喷气设施(OJF),以满足微型飞行器在极低速度和高湍流强度下进行飞行实验的要求。开放式喷气设施由台风机驱动,能够产生 0.1 - 16.8 米/秒的风速,风速比为 100:1。OJF 的收缩部分采用了邻接驱动优化法设计,收缩比为 3:1,长径比为 0.75。模块化设计的射流喷嘴可产生层流或高湍流风况。流场校准结果表明,OJF 能够产生高质量的基线流,稳定空速低至 0.1 米/秒,均匀区域约为横截面测试区域的 80%,湍流强度约为 0.5%。OJF 配备了优化的有源网格(AG),可以再现可控的、充分发展的湍流风条件,湍流强度可达 24%,能谱满足三分之二幂律,均匀区域接近测试截面面积的 70%。通过改变 AG 机翼上三角形通孔的面积,可以调节所产生气流的湍流强度、积分长度尺度、科尔莫哥洛夫长度尺度和平均能量耗散率。
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引用次数: 0
Numerical simulation and analysis of a ducted-fan drone hovering in confined environments 在密闭环境中悬停的风扇式无人机的数值模拟与分析
IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-26 DOI: 10.1186/s42774-024-00179-z
Yiwei Luo, Yuhang He, Bin Xu, Tianfu Ai, Yuping Qian, Yangjun Zhang
Ducted-fan drones are expected to become the main drone configuration in the future due to their high efficiency and minimal noise. When drones operate in confined spaces, significant proximity effects may interfere with the aerodynamic performance and pose challenges to flight safety. This study utilizes computational fluid dynamics simulation with the Unsteady Reynolds-averaged Navier–Stokes (URANS) method to estimate the proximity effects. Through experimental validation, our computational results show that the influence range of proximity effects lies within four rotor radii. The ground effect and the ceiling effect mainly affect thrust properties, while the wall effect mainly affects the lateral force and the pitching moment. In ground effect, the rotor thrust increases exponentially by up to 26% with ground distance compared with that in open space. Minimum duct thrust and total thrust are observed at one rotor radius above the ground. In ceiling effect, all the thrusts rise as the drone approaches the ceiling, and total thrust increases by up to 19%. In wall effect, all the thrusts stay constant. The pitching moment and lateral force rise exponentially with the wall distance. Changes in blade angle of attack and duct pressure distributions can account for the performance change. The results are of great importance to the path planning and flight controller design of ducted-fan drones for safe and efficient operations in confined environments.
风扇式无人机效率高、噪音小,有望成为未来无人机的主要配置。当无人机在密闭空间内运行时,明显的邻近效应可能会干扰气动性能,并对飞行安全构成挑战。本研究利用非稳态雷诺平均纳维-斯托克斯(URANS)方法进行计算流体动力学模拟,以估算邻近效应。通过实验验证,我们的计算结果表明,近地效应的影响范围在四个旋翼半径内。地面效应和顶棚效应主要影响推力特性,而壁面效应主要影响侧向力和俯仰力矩。在地面效应中,与开放空间相比,转子推力随地面距离的增加呈指数增长,最高可达 26%。在离地面一个转子半径处可观察到最小的风道推力和总推力。在天花板效应中,当无人机接近天花板时,所有推力都会上升,总推力最多增加 19%。在墙壁效应下,所有推力保持不变。俯仰力矩和侧向力随墙壁距离呈指数上升。叶片攻角和风道压力分布的变化可以解释性能的变化。这些结果对风道扇形无人机的路径规划和飞行控制器设计具有重要意义,可使其在狭窄环境中安全高效地运行。
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引用次数: 0
Effect of tip clearance on non-synchronous propagating flow disturbances of compressor rotors under high aerodynamic loading conditions 在高空气动力负荷条件下,叶尖间隙对压缩机转子非同步传播流动扰动的影响
IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-04 DOI: 10.1186/s42774-024-00178-0
Songbai Wang, Yong Chen, Yadong Wu
The complex tip flow instability and its induced non-synchronous vibration have become significant challenges, especially as aerodynamic loading continues to increase. This study investigates the effects of tip clearance on non-synchronous propagating flow disturbances of compressor rotors under high aerodynamic loading conditions by conducting full-annulus unsteady numerical simulations with three typical tip clearance values for a 1-1/2 stage transonic compressor. The non-synchronous aerodynamic excitation frequency, circumferential mode characteristics, and annular unstable flow structures are analyzed under near stall conditions. The results show that the total pressure ratio and normalized mass flow parameters first increase and then decrease as the tip clearance increases from 0.5%C (where C represents the tip chord length) to 2%C under high aerodynamic loading conditions, instead of constantly decreasing. For the 0.5%C tip clearance case, the traveling large-scale tornado-like separation vortices cause a low non-synchronous aerodynamic excitation frequency and severe pressure fluctuations. The periodic shedding and reattachment processes of the rotor blades separated by 2 – 3 pitches result in 19 dominant mode orders in the circumferential direction. As the tip clearance increases from 1%C to 2%C, the difference of tip flow structures in each blade passage is significantly weakened, and the dominant mode order of the disturbance is equal to the rotor blade-passing number. The pressure fluctuation is mainly caused by cross-channel tip leakage flow, and the aerodynamic excitation frequency exhibits evident broadband hump characteristics, which has been reported as a rotating instability phenomenon.
复杂的尖端流动不稳定性及其诱发的非同步振动已成为重大挑战,尤其是随着空气动力载荷的不断增加。本研究通过对 1-1/2 级跨音速压缩机进行全模量非稳态数值模拟,采用三种典型的顶端间隙值,研究了在高空气动力载荷条件下,顶端间隙对压缩机转子非同步传播流动扰动的影响。分析了近失速条件下的非同步空气动力激励频率、圆周模态特性和环形不稳定流动结构。结果表明,在高空气动力载荷条件下,随着顶端间隙从 0.5%C(C 代表顶端弦长)增加到 2%C,总压比和归一化质量流量参数不是持续下降,而是先增加后下降。在翼尖间隙为 0.5%C 的情况下,移动的大尺度龙卷风状分离涡导致较低的非同步气动激励频率和严重的压力波动。相隔 2 - 3 个螺距的转子叶片的周期性脱落和重新附着过程导致圆周方向上出现 19 个主导模态阶次。随着叶尖间隙从 1%C 增加到 2%C,每个叶片通道中的叶尖流动结构差异明显减弱,扰动的主模阶等于转子叶片通过数。压力波动主要由跨通道叶尖泄漏流引起,气动激励频率表现出明显的宽带驼峰特征,有报道称这是一种旋转不稳定现象。
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引用次数: 0
Direct numerical simulation of supersonic boundary layer transition induced by gap-type roughness 间隙型粗糙度诱发超音速边界层过渡的直接数值模拟
IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-02 DOI: 10.1186/s42774-024-00177-1
Hongkang Liu, Kehui Peng, Yatian Zhao, Qian Yu, Zhiqiang Kong, Jianqiang Chen
The transition of the supersonic boundary layer induced by roughness is a highly intricate process. Gaining a profound understanding of the transition phenomena and mechanisms is crucial for accurate prediction and control. In this study, to delve into the flow mechanisms of a transition in a supersonic boundary layer induced by the medium gap-type roughness, direct numerical simulation is employed to capture and analyze the transition process. Research indicates that as the flow over the flat plate passes the gap, the spanwise convergence effect leads to the formation of both upper and lower counter-rotating vortex pairs. As the flow progresses, these counter-rotating vortex pairs in the central region exhibit attenuation, with streamwise vortices developing on both sides. At a certain downstream distance, the boundary layer becomes unstable, triggering the formation of streamwise vortex legs. These streamwise vortex legs undergo further evolution, transforming into hairpin vortices and leg-buffer vortices. The formation of the central low-speed zone downstream of the roughness element is mainly attributed to the lift-up effect of the low-speed flow propelled by the central counter-rotating vortex pairs. The low-speed streaks on both sides are primarily influenced by the streamwise vortices. Through a meticulous analysis of the turbulent kinetic energy distribution and its generation mechanisms during the transition phase, this study infers that the primary sources of turbulent kinetic energy are the hairpin vortices, leg-buffer vortices, and their consequent secondary vortices. Combined with modal analysis, the study further elucidates the generation and breakdown of hairpin and leg-buffer vortices.
粗糙度引起的超音速边界层过渡是一个非常复杂的过程。深刻理解过渡现象和机制对于准确预测和控制至关重要。在本研究中,为了深入探讨介质间隙型粗糙度诱导的超音速边界层过渡的流动机制,采用了直接数值模拟来捕捉和分析过渡过程。研究表明,当流过平板的气流通过间隙时,跨向收敛效应会导致上下反向旋转涡对的形成。随着气流的前进,中心区域的这些逆旋转涡对出现衰减,两侧形成流向涡。在下游一定距离处,边界层变得不稳定,引发流向涡腿的形成。这些流向涡腿进一步演变,变成发夹涡和涡腿缓冲涡。粗糙度元件下游中央低速区的形成主要归因于中央反向旋转涡对推动的低速流的抬升效应。两侧的低速条纹则主要受到流向涡的影响。通过对过渡阶段湍流动能分布及其产生机制的细致分析,本研究推断湍流动能的主要来源是发夹涡、腿缓冲涡及其随之产生的次级涡。结合模态分析,该研究进一步阐明了发夹涡和腿缓冲涡的产生和分解。
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引用次数: 0
Numerical study on the thermodynamic behavior of de-icing liquid droplets impacting walls 除冰液滴撞击墙壁的热力学行为数值研究
IF 2.3 3区 工程技术 Q2 Engineering Pub Date : 2024-06-01 DOI: 10.1186/s42774-024-00176-2
Jing Cui, Shuxin Niu, Guangfeng Yang
Spraying de-icing fluid is a key method to ensure the safe operation of aircraft in icy and snowy weather. The film aggregation and internal mixing of de-icing fluid droplets on the aircraft skin during a collision are crucial. Considering the rheological properties of the molecular viscosity change of the de-icing fluid droplets during the collision and the heat transfer model of the heat loss after the impact, the phase field method is used to capture the gas–liquid interface, and a thermal pressure/viscous coupling model is constructed. The thermodynamic behavior of different axial distances is calculated. The results show that, as the dimensionless axial distance of the droplet increases, the spreading length of the fused droplet decreases instead, and the heat transfer rate of the droplet increases with the increase in spreading length. After stabilizing, the increase or decrease in the heat transfer rate depends on the strength of the heat transfer between the liquid layers. As the dimensionless axial distance increases, the internal flow of the droplet weakens and, between the droplet and the wall, the heat flux density gradually decreases and the average temperature drop of the droplet becomes gradual.
喷洒除冰液是确保飞机在冰雪天气中安全运行的关键方法。在碰撞过程中,飞机蒙皮上除冰液滴的薄膜聚集和内部混合至关重要。考虑到碰撞过程中除冰液液滴分子粘度变化的流变特性和撞击后热损失的传热模型,采用相场法捕捉气液界面,并构建了热压/粘性耦合模型。计算了不同轴向距离的热力学行为。结果表明,随着液滴无量纲轴向距离的增加,熔融液滴的铺展长度反而减小,液滴的传热速率随铺展长度的增加而增加。稳定后,传热速率的增减取决于液层间传热的强度。随着无量纲轴向距离的增加,液滴内部流动减弱,在液滴和壁面之间,热流密度逐渐降低,液滴的平均温度逐渐下降。
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引用次数: 0
The characteristics and corrections of ventral support interferences in the transonic-speed wind tunnel for the blended-wing-body aircraft 混合翼身飞机跨音速风洞中腹部支撑干扰的特征与修正
IF 2.3 3区 工程技术 Q2 Engineering Pub Date : 2024-05-20 DOI: 10.1186/s42774-024-00175-3
A. Qiu, W. Sang, Shuya Du, Bo An, Dong Li, Binqian Zhang
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引用次数: 0
The Full Non-linear Vortex Tube-Vorton Method: the pre-stall condition 全非线性涡管-涡顿法:预滞留条件
IF 2.3 3区 工程技术 Q2 Engineering Pub Date : 2024-04-18 DOI: 10.1186/s42774-023-00168-8
Jesus Carlos Pimentel-Garcia
The present hybrid vortex tube-vorton method is based entirely on the Full Multi-wake Vortex Lattice Method (FMVLM) concepts, which means detaching vorticity with precise vortex strength and orientation along all separation lines between each discretized element of a shell-body, including all external edges. Since the classic Vortex Particle Method (VPM) is unstable by itself because it does not conserve the total amount of circulation as time evolves (Kelvin’s circulation theorem), an isolated Vortex (regularized) Filament Method (VFM) approach is implemented to obtain advection of vorticity, while the induced velocity field is obtained through its corresponding full vorton cloud. Further, a novel vortex squeezing/stretching scheme for such a vortex cylinder-sphere approach is proposed based on variation in time for vortex volumes in order to precisely (zero residual) conserve both circulation and vorticity at each time step (for each detached vortex element), while the viscous effect can be accounted for via the Core Spreading Method (CSM).
目前的涡管-涡顿混合方法完全基于全多醒涡晶格法(FMVLM)概念,这意味着沿着壳体每个离散元素之间的所有分离线,包括所有外部边缘,分离出具有精确涡流强度和方向的涡度。由于经典的涡旋粒子法(VPM)本身并不稳定,因为它不能随着时间的推移保留循环总量(开尔文循环定理),因此采用了一种孤立的涡旋(正则化)细丝法(VFM)来获得涡度的平流,同时通过其相应的全涡旋云来获得诱导速度场。此外,还为这种涡旋圆柱-球方法提出了一种基于涡旋体积时间变化的新型涡旋挤压/拉伸方案,以便在每个时间步(对于每个分离的涡旋元素)精确地(零残余)保持环流和涡度,同时通过核心扩散法(CSM)考虑粘性效应。
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引用次数: 0
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Advances in Aerodynamics
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