Browsing by Author "Chen, Wenlong"

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    Data supporting the publication 'Clay swelling: role of cations in stabilizing/destabilizing mechanisms'
    (Cranfield University, 2022-01-18 16:34) Chen, Wenlong; Grabowski, Robert; Goel, Saurav
    In the compressed dataset, there are two subdirectories, one in the name of 'Example' and another 'PostprocessData'. The Example directory contains input files, output data and postprocessed data for case Na12 starting at a d-space of onelayer value, where files starts with in.* are input files for lammps software, files ending with .dat or .lmptrj are output files from lammps, and files ending with .mat are matlab processed data. The 'postporcessedata' contains matlab processed results for all simulations in this study, contains simulation for NaMMT, KMMT, CaMMT and NaBD starting at onelayer, twolayer and threelayer d-space values.
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    Data supporting: 'Green Nourishment: An Innovative Nature-Based Solution for Coastal Erosion'
    (Cranfield University, 2022-10-13 16:22) Chen, Wenlong; Grabowski, Robert; Goel, Saurav
    Coastal erosion poses an urgent threat to life and property in low-lying regions. Sand nourishment is increasing used as a nature-based solution but requires significant natural resources and replenishment over time. In this study, a novel form of nourishment is explored that combines shoreface nourishment and seagrass restoration to mitigate coastal erosion (i.e. green nourishment). Using the coastal morphodynamic model Xbeach, the impact of seagrass planting on wave energy dissipation, sediment erosion and transport, and morphological evolution of a cross-shore profile was studied for mild wave conditions and an intense storm. Model results indicate that a seagrass meadow enhanced the wave energy dissipation provided by a shoreface nourishment and suggest that it may be particularly effective in sediment transport mitigation when implemented in the sheltered nearshore area. The morphological feature of the shoreface nourishment reduced the wave strength on the seagrass meadow and reduced the rate of seagrass destroyed by deposition or erosion over the grass height after storm event. Green nourishment also reduced beach foreshore erosion caused by a simulated storm event. An alternative, more cost-effective planting technique using seagrass seeds was explored, which showed similar coastal erosion protection benefits to seagrass transplants. This modelling study found that green nourishment is potentially an effective nature-based solution for coastal erosion and flooding on sandy coasts, and future studies are recommended to evaluate its morphological, ecological and flood risk reduction benefits in the field.
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    Experimental and numerical studies on progressive debonding of grouted rock bolts
    (Elsevier, 2021-10-15) Shi, Hao; Song, Lei; Zhang, Houquan; Chen, Wenlong; Lin, Huasheng; Li, Danqi; Wang, Guozhu; Zhao, Huayun
    Understanding the mechanism of progressive debonding of bolts is of great significance for underground safety. In this paper, both laboratory experiment and numerical simulation of the pull-out tests were performed. The experimental pull-out test specimens were prepared using cement mortar material, and a relationship between the pull-out strength of the bolt and the uniaxial compressive strength (UCS) of cement mortar material specimen was established. The locations of crack developed in the pull-out process were identified using the acoustic emission (AE) technique. The pull-out test was reproduced using 2D Particle Flow Code (PFC2D) with calibrated parameters. The experimental results show that the axial displacement of the cement mortar material at the peak load during the test was approximately 5 mm for cement-based grout of all strength. In contrast, the peak load of the bolt increased with the UCS of the confining medium. Under peak load, cracks propagated to less than one half of the anchorage length, indicating a lag between crack propagation and axial bolt load transmission. The simulation results show that the dilatation between the bolt and the rock induced cracks and extended the force field along the anchorage direction; and, it was identified as the major contributing factor for the pull-out failure of rock bolt.
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    Experimental study on three-effect tubular solar still under vacuum and immersion cooling
    (Elsevier, 2021-06-28) Yan, Tiantong; Xie, Guo; Chen, Wenlong; Wu, Zhanglin; Xu, Jialing; Liu, Yingzhang
    Solar still is widely used for supplying fresh water to small communities in remote areas. One drawback of this technique lies in the low freshwater yield. Recent studies on stills of multi-effect and vacuum design proved their potential for high yield. However, such systems suffer from high electricity consumption and insufficient cooling. In this study, a novel system with a periodic pressure control scheme and water immersion cooling has been proposed to mitigate these defects. A prototype was constructed and associated with a 0.19-m2 solar panel. A 5-day outdoor experiment was conducted to evaluate the overall performance. Results indicated that the highest yield during the test was 9.8 kg/m2 at operating pressure of 40 kPa. A significant performance ratio of 1.87 was achieved with immersion cooling, i.e., 0.42 higher than that with air cooling. Thermal analysis showed that the heat transfer coefficient of water immersion cooling was 15–50 times higher than that of air cooling. Compared with previous vacuum-operated systems, the specific electricity consumption of maintaining vacuum was greatly reduced, i.e., from 21.6 kJ/kg to 1.7 kJ/kg for the case at 60 kPa. The forecast cost of the distilled water is $0.012/kg, representing an affordable desalination technique for off-grid communities.
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    Modelling short-range interaction of clay particles to improve erodibility prediction
    (EGU: European Geophysical Union, 2022-05-27) Chen, Wenlong; Grabowski, Robert C.; Goel, Saurav
    Introduction: Erosion has become an urgent problem to society due to the increasing intensity and frequency of disturbances, e.g. storms, wave energy and rainfall. Yet, a universal model to predict erosion thresholds for cohesive sediment is still missing. Short range interaction of clays is recognized as the source of cohesion and adhesion of cohesive sediment. The interaction of negatively charged (i.e., montmorillonite (MMT) and beidellite (BD)) and neutral clay particles (i.e., kaolinite (KL)) are traditionally simulated through DLVO theory and van der Waals interaction[1]. However, the applicability of DLVO theory at short range (i.e., at distance less than 3 nm) has been increasingly challenged in molecular dynamics simulations[2]. A suitable description of short-range clay particle interaction is crucial for the prediction of cohesive sediment erodibility. The aim of this study was to determine how clay mineralogy and water chemistry influence clay particle interactions at short range to affect inter-particle attraction and stability under imposed forces.
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    New non-destructive method for testing the strength of cement mortar material based on vibration frequency of steel bar: Theory and experiment
    (Elsevier, 2020-09-30) Shi, Hao; Song, Lei; Chen, Wenlong; Zhang, Houquan; Wang, Guozhu; Yuan, Guotao; Zhang, Wenliang; Chen, Guiwu; Wang, Yu; Lin, Gang
    Timely and accurately obtaining the strength of pouring material, e.g., concrete, cement mortar, is of great significance for engineering construction. In this paper, a non-destructive, economical and accurate strength detection method that suites for on-site using is proposed for the steel bar cement mortar material. The method based on the relationship between the vibration frequency of the steel bar and the properties of the mortar material, which is obtained by solving the Euler-Bernoulli beam problem. Both Particle Flow Code (PFC) software simulation (calibrated) and Split Hopkinson pressure Bar experiment on test samples of cement mortar and steel bar were performed to verify the theoretically obtained relationship. Studies on samples of various aggregate ratio further confirmed such correspondence. Results show that the dynamic stiffness of the cement mortar material dominates the calculation of the vibration frequency of steel bar, while the combined effect of the density, length, elastic modulus, inertia moment of the steel bar can be safely ignored. A single-valued mapping relation exists in between the dynamic stiffness coefficient and the Uniaxial Compressive Strength (UCS) of the cement mortar sample, i.e., increased dynamic stiffness coefficient with increasing UCS. Both experimental and predicted results showed a linear relationship between the vibration frequency of the steel bar and the strength of the mortar material. Fitted linear relations were proposed with coefficients depending on sample size and aggregate ratio and might serve as a good indicator for the strength of the mortar material. Further studies on the effect of internal defects of the mortar materials as well as on samples of more size and aggregate ratio are required to make the proposed method a practical tool
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    Performance of multi-stage tubular solar still operating under vacuum
    (Elsevier, 2022-11-21) Chen, Wenlong; Xie, Guo
    Multi-stage solar desalination running under vacuum is a low-cost, effective and sustainable way to mitigate fresh water shortage. However, questions remain on the operation pressure (Pop) and stage number of the multi-stage solar still. To address these questions, a predictive model was developed for the yield of multi-stage tubular solar still under vacuum (MSSV) and validated against field experiments. A 3-stage tubular still under typical weather (i.e. 19.75 MJ/m2 cumulative solar radiation) produced maximum water yield (7.15 kg/m2) with optimal Pop (48 kPa), much higher than under normal (5.81 kg/m2) and lower pressure (1.58 kg/m2 with Pop=20kPa). At optimal Pop, a delicate balance exists between the energy adsorbed and dissipated. Stronger solar intensity leads to more water yield and higher optimal Pop, while increasing the stage number improved the fresh water yield with diminishing marginal effect and slightly shifted the optimal Pop to a lower value. Using water immersion cooling other than air cooling significantly increased the water yield from 7.15 kg/m2 to 10.51 kg/m2. The MSSV model enriched the fundamental understanding of energy utilization for solar desalination and could serve as a design tool to maximize the performance of multi-stage solar still by optimizing still parameters and geometry.