241 research outputs found
Study on Porosity and Permeability Characteristics of Sandstone Geothermal Reservoir Under Recharge Conditions: A Case Study of Decheng District, Shandong Province
No full textAgainst the backdrop of growing concerns over environmental degradation and fossil fuel harms, geothermal energy—clean, low-carbon, widely distributed, and stably supplied—has gained increasing attention, becoming a key focus of renewable energy research. This study focused on a typical doublet-well system in Decheng District, Shandong Province, China, a region with mature geothermal development and high recharge demand. To investigate the water–rock interaction mechanism and its impact on reservoir properties, we combined indoor high-temperature/pressure static experiments with a hydro–thermo–chemistry coupling numerical simulation using TOUGHREACT V4.13-OMP. Experimental validation was conducted by matching the simulated major ion concentrations and pH values with the experimental results, confirming the reliability of the model parameters. The methodology integrated mineral composition analysis (XRD/XRF), hydrochemical testing of reaction solutions, and long-term numerical simulation of the doublet-well system under 50 heating cycles. The key qualitative results include the following: (1) feldspar minerals (sodium/potassium feldspar) are the main dissolved minerals, while dolomite and illite are the dominant precipitated minerals during recharge; (2) recharge-induced mineral precipitation causes significant near-well pore plugging, leading to continuous attenuation of porosity and permeability; (3) reducing Ca2+/Mg2+ concentrations in recharge water effectively alleviates permeability reduction, providing a feasible optimization direction for geothermal recharge schemes worldwide. This study enriches our understanding of sandstone geothermal reservoir evolution under recharge conditions and offers practical references for optimizing recharge strategies in similar geothermal fields globally
Stictoptera trajiciens Walker 1857
No full textStictoptera trajiciens (Walker, 1857) Figs. 12, 13, 104, 131, 157 Steiria trajiciens Walker, 1857, List Specimens lepid. Insects Colln Br. Mus., 13: 1137. Syntypes: Ceylon [Sri Lanka] (BMNH). Stictoptera trajiciens: Hampson, 1912, Cat. Lepid. Phal. Br. Mus., 11: 154. Diagnosis. The wing pattern of this species is distinctive. It is characterized by the diffused longitudinal lines of the forewing. V-shaped transversal triple line lies from the costal margin and gathered at the anal margin of forewing. In the male genitalia, the uncus bends centrally; the membranous webbing present from distal one fifth of costal lobe vertically to the basal one third of the sacculus, then extended to its end. Material examined. CHINA, Hainan: 2 males, Jianfengling, 21.VI., 21.X. 1982, coll. Liu Yuanfu and Chen Peizhen; 1 male, 1 female, Diaoluoshan, 930 m, 11–12.XII. 2007, coll. Li Jing and Chen Fuqiang (IZCAS). Guangxi: 1 male, Bobai, 200 m. 11.X. 1983, coll. Wang Jizhen; 1 male, Shangsi, 250 m, 28.V. 1999, coll. Yuan Decheng; 2 males, Fangcheng, Dalu, 250 m, 8.VI. 2000, coll. Li Wenzhu; 1 male, 1 female, Fangcheng, Fulong, 24–25.V. 1999, coll. Yuan Decheng and Zhang Yanzhou (IZCAS). Yunnan: 1 male, 2 females, Hekou, 80 m, 7.VI. 1956, coll. Huang Keren (IZCAS). Guangxi: 1 male, Pingxiang, 13.VI. 1976; 1 female, same locality, 12.V. 1963, coll. Yang Jikun (CAU). Distribution. China (Hainan, Guangxi, Hong Kong, Guizhou, Yunnan), India, Sri Lanka, Philippines, Malaysia, Singapore, Papua New Guinea, South Pacific islands. Biological notes. The larval host plants were recorded as Garcinia indica (Bell & Scott 1937) and Garcinia kandis (Clusiaceae) (Tho Yow Pong, in Holloway 1985).Published as part of Qi, Feng, Wang, Ke, Xue, Dayong & Yang, Ding, 2011, A taxonomic revision of the Stictopterinae (Lepidoptera, Noctuoidea, Noctuidae) in China, pp. 1-45 in Zootaxa 2926 on pages 6-7, DOI: 10.5281/zenodo.20593
Free-Surface Effects on the Evolution of a Marine Propeller's Wake
No full textThe present paper analyses the vortical structures in the wake of a naval propeller operating underneath a free surface using detached-eddy simulation. We investigate the flow topology for several loading conditions and compare it with analogous observations behind a propeller operating in open water. We show that the wake topology is similar to that observed in open water only for low-loading conditions. For mild blade loading, the free surface's presence seems to stabilize the flow. On the contrary, for high blade loading, the mutual interaction between the vortex system and the free surface leads to vortex breakdown that over-shadows the multiple pairing mechanisms observed in open-water conditions.The structure of propeller wakes received great attention in the past (Kerwin, 1986) and in recent years (Felli et al., 2011; Muscari et al., 2013; Di Mascio et al., 2014a; Muscari et al., 2017a; Magionesi et al., 2018) because the evolution of the main vortical structures that emanate from the blade tips and the hub is tightly related to vibrations, noise and aerodynamic/hydrodynamic performances. The wake of a rotor has a very complex topology, with several vortical systems with various shapes and strengths. Three main structures are generally present: tip vortices, blade vortex sheets and hub vortex. For each blade, the tip vortex and the blade vortex sheet correspond to the trailing vortex system of a wing, whose local strength is proportional to the radial variation of blade circulation. Since the most significant circulation variation appears at the blade end, vorticity is markedly higher at the tip than in the rest of the blade vortex sheet, with a distinguishable concentrated tip vortex. The hub vortex system is a well-defined streamwise structure, where the vorticity is equal in strength and opposite in orientation to the sum of blade vortex systems (in a simplified portrait of inviscid flow plus horseshoe vortices, it consists of the sum of each horseshoe vortex for the blades). In a more realistic picture of a viscous fluid, the blade vortex sheet also carries the vorticity generated in the boundary layer that detaches at the trailing edge. Moreover, horseshoe vortices are also present at each blade root. All these structures interact during downstream convection in a peculiar way that depends on the blade load (i.e. local incidence). For some loading conditions, the regular vortex system becomes unstable. These basic mechanisms were largely studied for the four-bladed E779A marine propeller by means of flow visualizations (Felli et al., 2011) and further corroborated by numerical simulations (Muscari et al., 2013; Ahmed et al., 2020; Wang et al., 2021a,b). The tip vortex is the first to experience helical instabilities associated with self- and coil-to-coil interaction due to self-induction. These perturbations propagate along the vortex tube and cause transverse oscillations of the cores. Further downstream, due to the weakening of the blade vortex sheet, the tip and hub vortices are no longer linked and evolve independently as separate structures, giving rise to destabilization process (Okulov and Sørensen, 2007). In facts, in the absence of the blade sheet (that damps tip vortex oscillations), the interactions between consecutive tip vortices are strengthened, giving rise to long-wave instabilities and promoting the merging of two adjacent tip vortices. Reduced- order analysis using proper orthogonal decomposition and dynamic mode decomposition of detached-eddy simulations proved that the merging process consists of a sequence of modes with an asymmetric evolution of the coupled tip vortices at the periphery of the slipstream (Magionesi et al., 2018). Consequently, the hub vortex experiences transverse oscillations that amplify downstream, driving a low-frequency precession motion of the outer structures. These mechanisms amplify vortex stretching and tilting, with complete redistribution of the vorticity that leads to the complete loss of coherence in the wake and transition to almost homogeneous turbulence. Experimental observations and numerical simulations show that all vortex pairing mechanisms and instabilities move upstream when the blade load increases; this happens because the distance between tip vortices decreases, thus increasing the mutual interaction
Chemical and rheological properties of polymer modified bitumen incorporating bio-oil derived from waste cooking oil
No full textThe chemical and rheological properties of polymer modified bitumen incorporating bio-oil derived from waste cooking oil (WCO) were investigated in this paper. At first, the chemical composition and mixing mechanism of the experimental materials were analysed from the perspective of functional group, and the influence of bio-oil on the activation energy was also researched. Then, the effect of bio-oil on the rotational viscosities of polymer modified bitumen and construction temperatures of corresponding mixtures was studied. Finally, the shear and bending rheological properties of polymer modified bitumen containing bio-oil were investigated. The results show that the bio-oil and styrene–butadiene–styrene (SBS) modified bitumen is mainly physically mixed, the addition of bio-oil decreases the activation energy of SBS modified bitumen. Additionally, the SBS modified bitumen containing bio-oil has lower viscosity values, and corresponding mixtures also have lower construction temperatures. Furthermore, the addition of bio-oil in SBS modified bitumen reduces the shear modulus and increases the bending creep compliance, which means bio-oil has positive effect on the low-temperature thermal cracking resistance performance while sacrificing the high-temperature rutting resistance performance to some extent. Therefore, the incorporation of WCO-based bio-oil in polymer modified bitumen is a promising technique to be used in cold regions where the low-temperature problems are more crucial.Accepted Author ManuscriptPavement Engineerin
Analysis of the microcharacteristics of different kinds of asphalt based on different aging conditions
No full textAsphalt aging often leads to rapid degradation of road performance, which seriously affects the service life of asphalt pavement. Exploring the influence of asphalt oil sources, asphalt grades, and filler types on asphalt microcharacteristics in the asphalt aging process can provide an essential reference to guide asphalt pavement maintenance. In this study, we selected seven kinds of asphalt and three fillers commonly used in China for research. The pressurized aging vessel (PAV) and homemade ultraviolet (UV) aging equipment were used to perform thermo-oxidative aging and UV aging tests, respectively, of asphalt. The microcharacteristics of asphalt before and after aging were analyzed via attenuated total reflectance fourier transformation infrared spectroscopy and nuclear magnetic resonance 1H spectroscopy. The results show that the oil source of asphalt exerted the most significant influence on the microcharacteristics of the aged asphalt, while the effect of the asphalt grade was relatively limited. The addition of fillers did not affect the aging mechanism of asphalt. UV and PAV aging generated apparent differences in the changes in the aged asphalt microstructure.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pavement Engineerin
Aetheomorpha coerulea Jacoby 1892
No full textAetheomorpha coerulea (Jacoby, 1892) (Figures 8A–I, 12H) Jacoby, 1892: 882 (orig.: Aspidolopha coerulea; type locality: Burma, Carin Chebà; type deposited: MSNG); 1908: 134; Clavareau, 1913: 44 (catalogue); Kimoto and Gressitt, 1981: 297 (transfer to Aetheomorpha; Thailand, Vietnam); Regalin and Medvedev, 2010: 564 (catalogue); Medvedev, 2010: 198 (Yunnan: Xishuangbanna). Material examined CHINA: Hainan: one male, one female, Jianfengling, 12 August 1981, leg. Maobin Gu; Yunnan: two males, Xishuangbanna, Xiaomengyang, 12 July 1957, leg. Lingchao Zang; two females, Xishuangbanna, Xiaomengyang, 13 July 1957, leg. Shuyong Wang; one male, Xishuangbanna, Menghun, 19 May 1958, leg. Yiran Zhang; one male, six females, Xishuangbanna, Menghun, 6 June 1958, leg. Xuwu Meng; one female, Xishuangbanna, Menghai, 21 July 1958, leg. Fuji Pu; one male, one female, Xishuangbanna, Mengzhe, 25 July 1958, leg. Shuyong Wang; one male, Xishuangbanna, Meng’a, 9 August 1958, leg. Shuyong Wang; one female, Xishuangbanna, Mengla, 20 May 1958, leg. Facai Zhang; one female, Xishuangbanna, Mengsong, 24 July 1958, leg. Leyi Zheng; one female, Ruili, Wanting, 10 June 1992, leg. Decheng Yuan (IZ-CAS). Distribution China (Hainan, Yunnan); Burma, Thailand, Vietnam, Malaysia. Remarks This species is well defined by its characteristic colouration: elytra are completely bluish black and pronotum is fulvous with a central black band. Also, the aedeagal apex slightly bent ventrally; the spermathecal duct is long, irregularly coiled dozens of times and the dorsal central sclerite is sub-oblong.Published as part of Wang, Feng-Yan & Zhou, Hong-Zhang, 2012, Taxonomy of the genus Aetheomorpha Lacordaire (Coleoptera: Chrysomelidae: Cryptocephalinae: Clytrini) from China, with description of five new species, pp. 1407-1440 in Journal of Natural History 46 (23 - 24) on page 1426, DOI: 10.1080/00222933.2012.673642, http://zenodo.org/record/520011
Hydrodynamic validation of a semi-submersible floating platform supporting a 15MW wind turbine toweunder extreme loading scenarios with DualSPHysics and MoorDyn+
No full textTo investigate the hydrodynamic performance of the floating platform VolturnUS-S as configured for the 1st Floating Offshore Wind Turbine (FOWT) Comparative Study, we have used a Smoothed Particle Hydrodynamics (SPH) based solver that features a coupling to the cable dynamic solver MoorDyn+ to reproduce the proposed benchmarks. This is a quite novel application of the method to simulate semi-submersible platforms for offshore wind energy. For this benchmark, which does not include aerodynamic actions, we have proposed a new procedure, leveraging offline coupling techniques to model the problem in a sub-domain of the reference wave basin. Our approach is detailed and validated for wave propagation only, and thus applied to reproduce the wave-platform interaction for an extreme focused wave condition. Good results are obtained for the wave generation and validation using open boundary conditions as well as for the platform motion under the extreme event
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