IMECH-IR中国科学院力学研究所http://dspace.imech.ac.cn:802024-03-19T02:41:25Z2024-03-19T02:41:25ZA cluster analysis-based shock wave pattern recognition method for two-dimensional inviscid compressible flowsChang SY(常思源)Liu J(刘君)Cui K(崔凯)http://dspace.imech.ac.cn:80/handle/311007/943962024-03-18T10:17:42Z2024-03-18T09:49:15ZTitle: A cluster analysis-based shock wave pattern recognition method for two-dimensional inviscid compressible flows
Authors: Chang SY(常思源); Liu J(刘君); Cui K(崔凯)
Description: <p>Compressible flows typically exhibit multiple shock waves which interact with each other, making the detection of these shock waves crucial for various aspects of flow studies including construction of high-order numerical schemes (e.g., shock-fitting), adaptive grid refinement, and flow visualization. This study aims to effectively identify and localize multiple shock waves and their interaction points in two-dimensional inviscid steady and unsteady flows. A novel shock wave pattern recognition method based on cluster analysis is proposed, including three processes. First, a series of grid-cells located at the transition zones of captured shock waves are extracted using a shock wave detection approach based on local flow variation. Subsequently, these grid-cells are grouped into numerous clusters using the classical <em>K</em>-means clustering algorithm, with categorization based on nearest neighbor features. Finally, a strategy is introduced to merge relevant adjacent clusters and further localize the points where shock waves interact. The Bézier curve fitting technique is then employed to obtain the high-quality shock-lines. Several numerical cases demonstrate that this method achieves high localization accuracy for shock-lines while being minimally affected by grid type and scale variations. Moreover, it enables clear and effective identification of the shock interaction patterns in both steady and unsteady flows, providing an effective visualization means for analyzing the motion and evolution of shock wave configurations.</p>2024-03-18T09:49:15ZThermocapillarity transition-induced unconventional thermal behavior and dilution in laser welding of metals with dissimilar sulfur contentZhiyong LiXiuli HeShaoxia LiGang Yuhttp://dspace.imech.ac.cn:80/handle/311007/943952024-03-15T17:06:56Z2024-03-15T17:07:32ZTitle: Thermocapillarity transition-induced unconventional thermal behavior and dilution in laser welding of metals with dissimilar sulfur content
Authors: Zhiyong Li; Xiuli He; Shaoxia Li; Gang Yu
Description: <p>An enhanced three-dimensional transient Thermal-Fluid-Dilution model, integrating a sub-model that accounts for surface tension, is proposed to investigate the unconventional thermal behavior and dilution induced by the surface-active element (sulfur) during the laser joining process of 304SS with higher sulfur content and pure nickel with lower sulfur content. Surface tension is modeled as a function dependent on local temperature and the concentration of the surface-active element (sulfur) at the free surface. The temperature and sulfur-dependent surface tension initially generate an unconventional driving force, subsequently leading to the transitions of heat transfer, flow pattern, and species dilution. Specifically, the inclusion of the sulfur effect results in a redistribution of larger surface shear stress along the transition boundary, causing unconventional flow behavior. The temperature coefficient of surface tension (TCST) is the coexistence of TCST (-) and TCST (+), leading to a novel flow pattern with combined inward-outward flows. Moreover, the anomalous flow exhibits observed phenomena such as the rotation of the major axis (RA) and center line shift (CLS) within the melt pool, showing more reasonable simulated melt pool dimensions when accounting for the sulfur effect. Additionally, the dilution model integrated with the unconventional flow pattern presents a more uniform concentration distribution compared to the conventional dilution. Finally, the simulated distribution of alloy elements is validated effectively by experimental data obtained from Energy Dispersive Spectrometer (EDS) analysis.</p>2024-03-15T17:07:32ZEffect of copper loading on synergism in CuO/CeO<sub>2</sub> nanorod catalysts for toluene combustion高鑫Yun, JianyuDeng, Linlin衣晓坤Teng, ZihaoWang, YifanDou, Baojuan宾峰http://dspace.imech.ac.cn:80/handle/311007/943942024-03-14T07:45:10Z2024-03-11T08:07:24ZTitle: Effect of copper loading on synergism in CuO/CeO<sub>2</sub> nanorod catalysts for toluene combustion
Authors: 高鑫; Yun, Jianyu; Deng, Linlin; 衣晓坤; Teng, Zihao; Wang, Yifan; Dou, Baojuan; 宾峰
Description: CuO/CeO2 catalysts were widely studied as an alternative to precious metal catalysts, and the Cu-Ce synergy was essential to improve the catalytic performance. In this paper, the effects of CuO loading on Cu-Ce synergy in CuO/CeO2 nanorod catalysts and their performance in toluene combustion were systematically investigated. It was found that non-equilibrium plasma facilitated the dispersion of CuO active species on the CeO2 surface. With the increase of the CuO loading from 1 wt% to 4 wt%, the Cu-Ce synergistic effect was gradually improved, which generated Cu+/Cu2+ and Ce3+/Ce4+ redox electron pairs. The highest oxygen vacancy concentration and Cu+ content of CuCe-4 (4 wt%) resulting from strong Cu-Ce synergy accelerated the activation of chemisorbed oxygen and consequently improved the efficiency of toluene catalytic combustion.2024-03-11T08:07:24ZA theoretical model of cross-flow heat transfer for the cooling process in a horizontal moving bed of high-temperature particles潘利生Shi, Weixiu魏小林http://dspace.imech.ac.cn:80/handle/311007/943912024-03-14T07:45:11Z2024-03-11T08:07:22ZTitle: A theoretical model of cross-flow heat transfer for the cooling process in a horizontal moving bed of high-temperature particles
Authors: 潘利生; Shi, Weixiu; 魏小林
Description: Besides waste gas and liquid, high-temperature particles are important media of waste heat and their temperature exceeds 1000 degrees C on many occasions. The cross-flow heat transfer is important in this waste heat recovering process, but there are few references reported about the theoretical modeling. Therefore, a theoretical model was developed for the cooling process in a horizontal moving bed of high-temperature particles. The purpose of the study is to estimate the influence of temperature field and flow field on heat transfer and bed resistance in the cross-flow cooling process. Three modes such as conduction, convection and radiation are considered in the model. This model was used to analyze heat transfer in a horizontal moving bed of cement clinker and was verified by comparing some simulative results with the tested and collected data from an actual cement clinker plant in China. The simulative temperature of cement clinker was 200 degrees C as same as that collected in the actual cement clinker plant. In the moving bed, the highest pressure drop occurs at the front top and the strongest heat transfer occurs at the front bottom. In the considered conditions with even distribution of cooling air, the highest pressure drop is 3205.9 Pa/m, the biggest specific heat transfer rate of 1683.1 kW/m3. Thermal radiation plays a minor role in this cooling process with the biggest radiation proportion is only 0.149 at the front top. This mode plays a minor role in this cooling process of the cement clinker, comparing with the thermal convection. With constant flow rate of cooling air, the distribution can regulate the local cooling rate rather than the final temperature of the cement clinker.2024-03-11T08:07:22ZPolymorphic phase transition in CoCrNi medium-entropy alloy under impact loadings周文博曹富华杨增宇李统牛洋洋陈艳汪海英戴兰宏http://dspace.imech.ac.cn:80/handle/311007/943882024-03-14T07:45:13Z2024-03-11T08:07:20ZTitle: Polymorphic phase transition in CoCrNi medium-entropy alloy under impact loadings
Authors: 周文博; 曹富华; 杨增宇; 李统; 牛洋洋; 陈艳; 汪海英; 戴兰宏
Description: Polymorphic phase transition in metallic materials under high pressure is a critical aspect of dynamic properties and has been attracting a great interest. Despite the extensive researches have been made on understanding of this phase transition in traditional single -principal element alloys, little is known about the phase transition in recently emergent multi-principal medium and high entropy alloys, especially compressed under high strain rates. In this work, based on molecular dynamic simulations, three impact loading strategies with distinct loading paths, such as single-shock, double-shock and ramp-wave loading are carried out on the single crystalline CoCrNi medium-entropy alloy (MEA) to investigate the phase transition under high strain-rate compression. Careful characterizations show that the phase transition of CoCrNi MEA is loading-path dependent, as evidenced by the significant differences in macroscopic pressure evolution and microscopic structural phase transition among the samples under various thermodynamic paths. An intriguing pressure "overshoot" is found and demonstrated as the characteristic of the critical structural phase transition from face-centered cubic (FCC) structure to hexagonal-close-packed (HCP) structure mediated by body-centered cubic (BCC) like clusters. We show that such loading-path dependence is attributed to the strain rate and temperature rise in the loading process, which control the evolution of microstructure and deformation field. The inherent correlation between the atomistic process of phase transition and loading strategies results in polymorphic phase transition under high strain rates. These findings shed new light on the nature of impact phase transition of multi-principal alloys.2024-03-11T08:07:20ZValidation of local approach-based statistical models for cleavage fracture of ferritic steels in uniaxial tensionLei, WeiSheng钱桂安Zhang, Peileihttp://dspace.imech.ac.cn:80/handle/311007/943852024-03-14T07:45:16Z2024-03-11T08:07:19ZTitle: Validation of local approach-based statistical models for cleavage fracture of ferritic steels in uniaxial tension
Authors: Lei, WeiSheng; 钱桂安; Zhang, Peilei
Description: Five major local approach (LA)-based statistical cleavage fracture models are evaluated in uniaxial tension. The focus is to inspect their mathematical conformity to the axiom of probability on normality and their physical adherence to the consensus that cleavage fracture occurs after plastic deformation. Only the LA model that incorporates a stress-state and temperature dependent threshold satisfies both requirements. Two sets of experimental data in uniaxial tension are analyzed to support the arguments.
The normality axiom of probability applies to any probability model. It is a consensus that cleavage fracture of steels is preceded by plastic yielding. 5 statistical cleavage fracture models are checked by the 2 points in uniaxial tension. 1 model observes both points; 4 models fail to satisfy both criteria.2024-03-11T08:07:19ZNumerical study on hypersonic aerodynamic characteristics of the high-pressure capturing wing configuration with wing dihedral常思源肖尧李广利田中伟崔凯http://dspace.imech.ac.cn:80/handle/311007/943822024-03-14T07:45:11Z2024-03-11T08:07:17ZTitle: Numerical study on hypersonic aerodynamic characteristics of the high-pressure capturing wing configuration with wing dihedral
Authors: 常思源; 肖尧; 李广利; 田中伟; 崔凯
Description: High-pressure capturing wing (HCW) configuration is a potential hypersonic aerodynamic configuration that can simultaneously have good lift-drag characteristics with a large volumetric ratio. The effects of wing dihedral angle on the hypersonic aerodynamic characteristics of a conceptual HCW configuration with two lifting wings are investigated in this paper. Specifically, the dihedral angles of two wings, the upper HCW and the conventional delta wing at the bottom of the body, were regarded as the design variables with a given space. Furthermore, the uniform experimental design method, computational fluid dynamics simulation techniques, and kriging surrogate model algorithm were successively utilized to establish the distributions of aerodynamic parameters over the design space. The results indicate that the lift, drag, and lift-to-drag ratio (L/D) have the similar variation trends as the dihedral angles of the two wings change, and are more sensitive to the positive dihedral angle of the delta wing. When the angle of attack is small, the increasing positive dihedral angle significantly reduces L/D, but as the negative dihedral angle increases, L/D will first increase slightly and then decrease slowly. In particular, when the angle of attack is large, the wing dihedral angles have less influence on L/D. For the longitudinal stability, it is mainly affected by the dihedral angles of the delta wing, and the positive dihedral angle can slightly weaken it, while the negative one hardly changes it. The directional stability can be enhanced by the wing dihedral angles, especially the negative angle. The positive dihedral angle can improve the lateral stability, while the negative weaken it. However, when the angle of attack is large, the large positive dihedral angle of the delta wing may lead to a decrease in the lateral stability.2024-03-11T08:07:17ZInterfacial instabilities driven by co-directional rarefaction and shock wavesGao, XingGuo, XuZhai, Zhigang罗喜胜http://dspace.imech.ac.cn:80/handle/311007/943792024-03-14T07:44:57Z2024-03-11T08:05:17ZTitle: Interfacial instabilities driven by co-directional rarefaction and shock waves
Authors: Gao, Xing; Guo, Xu; Zhai, Zhigang; 罗喜胜
Description: We report the first experiments on hydrodynamic instabilities of a single-mode light/heavy interface driven by codirectional rarefaction and shock waves. The experiments are conducted in a specially designed rarefaction-shock tube that enables the decoupling of interfacial instabilities caused by these co-directional waves. After the impacts of rarefaction and shock waves, the interface evolution transitions into Richtmyer-Meshkov unstable states from Rayleigh-Taylor (RT) stable states, which is different from the finding in the previous case with counter-directional rarefaction and shock waves. A scaling method is proposed, which effectively collapses the RT stable perturbation growths. An analytical theory for predicting the time-dependent acceleration and density induced by rarefaction waves is established. Based on the analytical theory, the model proposed by Mikaelian (Phys. Fluids, vol. 21, 2009, p. 024103) is revised to provide a good description of the dimensionless RT stable behaviour. Before the shock arrival, the unequal interface velocities, caused by rarefaction-induced uneven vorticity, result in a V-shape-like interface. The linear growth rate of the amplitude is insensitive to the pre-shock interface shape, and can be well predicted by the linear superposition of growth rates induced by rarefaction and shock waves. The nonlinear growth rate is higher than that of a pure single-mode case, which can be predicted by the nonlinear models (Sadot et al., Phys. Rev. Lett., vol. 80, 1998, pp. 1654-1657; Dimonte & Ramaprabhu, Phys. Fluids, vol. 22, 2010, p. 014104).2024-03-11T08:05:17ZMagnetic field recovery technique based on distance weighting multipole expansion methodLiu, BinbinYang, ZhenQiang, LiEPeng, XiaodongMa, Xiaoshan徐鹏罗子人Tang, WenlinZhang, YuzhuGao, Chenhttp://dspace.imech.ac.cn:80/handle/311007/943762024-03-14T07:45:04Z2024-03-11T08:05:15ZTitle: Magnetic field recovery technique based on distance weighting multipole expansion method
Authors: Liu, Binbin; Yang, Zhen; Qiang, LiE; Peng, Xiaodong; Ma, Xiaoshan; 徐鹏; 罗子人; Tang, Wenlin; Zhang, Yuzhu; Gao, Chen
Description: - A space-borne gravitational wave detector requires the test mass (TM) to be in an ultra-low disturbance state. However, magnetic field fluctuations will disturb the TM and produce acceleration noise. To assess the influence of the magnetic field on the TM, it is necessary to monitor and reconstruct the magnetic field near the TM in real time. In this paper, a distance weighting multipole expansion (DWME) method was proposed, and its magnetic field reconstruction accuracy was analyzed. The results demonstrated that the proposed DWME method significantly improved the reconstruction precision compared to traditional methods. It reduced the average reconstruction error of the sensitive axial magnetic field from 1.2% to 0.8% and the maximum error from 16% to 8%. In the in-orbit situation, the DWME method also outperforms traditional methods.2024-03-11T08:05:15ZStudy on the influence of perforation parameters on hydraulic fracture initiation and propagation based on CDEMLi, Jing王理想冯春Zhang, Rui朱心广Zhang, Yiminghttp://dspace.imech.ac.cn:80/handle/311007/943732024-03-14T07:45:03Z2024-03-11T08:05:13ZTitle: Study on the influence of perforation parameters on hydraulic fracture initiation and propagation based on CDEM
Authors: Li, Jing; 王理想; 冯春; Zhang, Rui; 朱心广; Zhang, Yiming
Description: Perforation hydraulic fracturing plays a crucial role in the development of oil and gas reservoirs, and perforation layout can significantly affect the initiation and propagation of complex reservoir rock fractures. In this paper, we used a mixed finite-discrete element method with an explicit iterative scheme called the continuous-discontinuous element method (CDEM) to study the process of hydraulic fracture propagation through perforation. The coupling effects of fluid flow and reservoir mechanics are fully considered, and the accuracy of the model in simulating the directional propagation of perforation hydraulic fractures is validated by comparison with physical experimental results. We also discussed in detail the impact of perforation pattern, density, depth, and aperture on crack initiation, propagation, and complexity, and used the new index of fracture degree to quantitatively evaluate the fracturing effects under the influence of multiple perforation layout parameters. The results indicate that: (i) hydraulic fractures near the wellbore compete for initiation, and the length distribution of cracks is uneven and intricate; (ii) linear perforation patterns produce the maximum initiation pressure, which is negatively correlated with the perforation density and positively correlated with the perforation depth and aperture; (iii) the fracture degree is mainly affected by perforation density and depth, and is less affected by aperture. Perforation can effectively control the fracture morphology and initiation pressure, and has a substantial influence on the crack propagation layout near the wellbore. This study provides a basis for the rational selection and optimization of perforation parameters, which can effectively improve the fracturing effects of tight oil and gas reservoirs.2024-03-11T08:05:13Z