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Transport mechanism of eroded sediment particles under freeze-thaw and runoff conditions

Journal of Arid Land 2022年第5期14卷 490-501页

作者： WANG Tian li Peng HOU Jingming TONG Yu li Jing WANG Feng li zhanbin State Key Laboratory of Eco-hydraulics in Northwest Arid Region Xi'an University of TechnologyXi'an 710048China Key Laboratory of National Forestry Administration on Ecological Hydrology and Disaster Prevention in Arid Regions Xi'an University of TechnologyXi'an 710048China

Hydraulic erosion associated with seasonal freeze-thaw cycles is one of the most predominant factors,which drives soil stripping and transportation.In this study,indoor simulated meltwater erosion experiments were used to investigate the sorting characteristics and transport mechanism of sediment particles under different freeze-thaw conditions(unfrozen,shallow-thawed,and frozen slopes)and runoff rates(1,2,and 4 L/min).Results showed that the order of sediment particle contents was silt>sand>clay during erosion process on unfrozen,shallow-thawed,and frozen slopes.Compared with original soils,clay and silt were lost,and sand was deposited.On unfrozen and shallow-thawed slopes,the change of runoff rate had a significant impact on the enrichment of clay,silt,and sand particles.In this study,the sediment particles transported in the form of suspension/saltation were 83.58%–86.54%on unfrozen slopes,69.24%–84.89%on shallow-thawed slopes,and 83.75%–87.44%on frozen slopes.Moreover,sediment particles smaller than 0.027 mm were preferentially transported.On shallow-thawed slope,relative contribution percentage of suspension/saltation sediment particles gradually increased with the increase in runoff rate,and an opposite trend occurred on unfrozen and frozen slopes.At the same runoff rate,freeze-thaw process had a significant impact on the relative contribution percentage of sediment particle transport via suspension/saltation and rolling during erosion process.The research results provide an improved transport mechanism under freeze-thaw condition for steep loessal slopes.

关键词： freeze-thaw runoff conditions erosion process sediment particles transport mechanism

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Fluid-Thermal-Mechanical Coupled Analysis and Optimized Design of Printed Circuit Heat Exchanger with Airfoil Fins of S-CO_(2) Brayton Cycle

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Journal of Thermal Science 2022年第6期31卷 2264-2280页

作者： JIANG Tao li Mingjia WANG Wenqi li Dong liU zhanbin Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education School of Energy and Power EngineeringXi’an Jiaotong UniversityXi'an710049China

Printed Circuit Heat Exchanger(PCHE) with high-efficiency and compact structure has great application prospect in the supercritical carbon dioxide(S-CO_(2)) power systems for the next generation of high-temperature concentrated solar and advanced nuclear energy. However, the high operating temperature and pressure require PCHE to maintain good heat transfer performance, as well as reliable mechanical performance at the same time. It is necessary to carry out the fluid-thermal-mechanical coupled analysis of PCHE for the safe and efficient operation of the S-CO_(2) cycle. In this paper, a three-dimensional fluid-structure coupled numerical model was established to study the fluid-thermal-mechanical coupled characteristics of PCHE under different airfoil fin arrangements. The stress distribution of the single airfoil fin was studied, and a better airfoil arrangement that comprehensively considers heat transfer characteristics and stress distribution was obtained. Aiming at the high stress caused by the stress concentration at both ends of the airfoil fin, an optimized configuration combining straight channel and airfoil channel was proposed. The results show that the difference between the flow and heat transfer performance of the two optimized structures and the reference structure is only within 1.5%, but the maximum stresses of the two optimized structures are respectively reduced by 69.4% and 70.0% compared with that of the reference structure, which significantly reduces the stress intensity of PCHE. The result provides a new method to develop the airfoil PCHE with uniform stress distribution and good thermo-hydraulic performance.

关键词： printed circuit heat exchanger supercritical carbon dioxide airfoil fin thermal-mechanical coupling

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Distribution characteristics of available trace elements in soil from a reclaimed land in a mining area of north Shaanxi,China

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International Soil and Water Conservation Research 2013年第1期1卷 65-75页

作者： li zhanbin Zhang Qinling li Peng Key Lab of Northwest Water Resources and Environment Ecology of MOE Xi'an University of Technology Xi'an 710048ShaanxiP.R.China State Key Laboratory of Soil Erosion and Dry-land Farming on the Lous Plateau Institute of Soil and Water ConservationChinese Academy of SciencesYangling 712100ShaanxiP.R.China Soil and Water Conservation Bureau in Shaanxi Province Xi'an 710042ShaanxiP.R.China

Through field and laboratory tests we studied the temporal and spatial variation in the soil content of four available trace elements:copper(Cu),iron(Fe),manganese(Mn)and zinc(Zn),to analyze their distribution characteristics in reclaimed mining land under different reclamation conditions.The available trace elements content varied considerably with different land reclamation patterns.Extended reclamation time was helpful for the recovery of the available trace element content in the soil,and after more than eight years of soil reclamation,the content of available trace elements was closer to or greater than that in soil under natural conditions.Various treatment measures significantly influenced the content and distribution of available trace elements in the soil,and reasonable artificial treatments,including covering the soil and growing shrubs and herbaceous plants,increased the content of available trace elements.

关键词： Available trace element Reclaimed land Reclamation time Treatment measure Mining area

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Hydrological and sediment connectivity under freeze-thaw meltwater compound erosion conditions on a loessal slope

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International Soil and Water Conservation Research 2023年第2期11卷 402-411页

作者： Tian Wang Jingsi li Jingming Hou Yongyong Ma Peng li Yu Tong Jing li zhanbin li State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China Xi'an University of TechnologyXi'an710048ShaanxiChina Key Laboratory of National Forestry Administration on Ecological Hydrology and Disaster Prevention in Arid Regions Xian University of TechnologyXi'an 710048ShaanxiChina Shaanxi Province Institute of Water Resources and Electric Power Investigation and Design Xi'an710005ShaanxiChina

Freeze-thaw processes can influence hydrology,soil erosion,and morphological development by altering the connectivity between active pathways of water and sediment transport.Concentrated flow experi-ments were conducted involving frozen,shallow thawed,and unfrozen soil slopes under 1,2,and 4 L/min runoff rates at a temperature of approximately 5℃.In this study,hydrological connectivity was analysed via the simplified hydrological curve and relative surface connection function.Sediment con-nectivity was analysed via the sediment structure connectivity and sediment functional connectivity.Results indicated that hydrological connectivity was greatest on frozen slopes(FS),followed by shallow thawed slopes(STS),and unfrozen slopes(UFS)given a constant flow rate.Hydrological connectivity increased with increasing runoff rate for each freeze-thaw condition.Freezing condition and runoff rate exhibited a positive response to the hydrological connectivity.Sediment structure connectivity increased with increasing runoff rate for each slope condition.The ordering of sediment structure connectivity across freeze-thaw condition was that FS was greater than STS while STS was greater than UFS inde-pendent of flow rate.Sediment functional connectivity included longitudinal,lateral,and vertical con-nectivity components.Sediment longitudinal and vertical connectivity indicated a trend of first increasing and then decreasing under the different runoff rates and freeze-thaw conditions.For a given runoff rate,the ordering of sediment longitudinal and vertical connectivity across freeze-thaw condition was that FS was greater than STS while STS was greater than UFS.Sediment lateral connectivity exhibited a trend of first decreasing and then stabilizing.The ordering of sediment lateral connectivity across freeze-thaw condition was that UFS was greater than STS while STS was greater than FS.FS could more easily reach longitudinal and vertical penetration.Sediment longitudinal and vertical connectivity rates demonstrated increasing trends

关键词： Freeze-thaw Runoff Erosion Structureand functional connectivity Loessal slope

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Effects of a check dam system on the runoff generation and concentration processes of a catchment on the Loess Plateau

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International Soil and Water Conservation Research 2022年第1期10卷 86-98页

作者： Shuilong Yuan zhanbin li li Chen Peng li Zeyu Zhang Junzheng Zhang Anna Wang kunxia Yu State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China Xi'an University of TechnologyXi'an710048ShaanxiChina Key Laboratory of National Forestry Administration on Ecological Hydrology and Disaster Prevention in Arid Regions Xi'an University of TechnologyXi'an710048ShaanxiChina Desert Research Institute Las VegasNV89012USA Institute of Soil and Water Conservation Investigation and Planning of Shaanxi Province Xi'an710100ShaanxiChina

As an important soil and water conservation engineering measure,more than 100,000 check dams are constructed across the Loess Plateau;these dams play a vital role in reducing floods and sediment in the region.However,the effects of check dams on hydrologic process are still unclear,particularly when they are deployed as a system for watershed soil and water management.This study examined the watershed hydrologic process modulated by the check dam system in a typical Loess Plateau catchment.By simulating scenarios with various numbers of check dams using a distributed physically-based hydro-logical model,the effects of the number of check dams on runoff generation and concentration were analyzed for the study catchment.The results showed that the presence of check dams reduced the peak discharge and the flood volume and extended the flood duration;the reduction effect on peak discharge was most significant among the three factors.The system of check dams substantially decreased the runoff coefficient,and the runoff coefficient reduction rate was greater for rainstorms with shorter return periods than for rainstorms with longer return periods.The check dams increased the capacity of the catchment regulating and storing floods and extended the average runoff concentration time in the catchment that flattened the instantaneous unit hydrograph.This study reveals the influencing mech-anism of check dam system on the watershed hydrological process under heavy rainstorm conditions and provides a theoretical basis for evaluating the effects of numerous check dams on regional hydrology and water resources on the Loess Plateau.

关键词： Check dam system Runoff generation Runoff concentration Instantaneous unit hydrograph Loess Plateau

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Quantitative study on influences of terraced field construction and check-dam siltation on soil erosion

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Journal of Geographical Sciences 2012年第5期22卷 946-960页

作者： GAO Haidong li zhanbin li Peng JIA lianlian ZHANG Xiang institute of Soil and Water Conservation CAS and Ministry of Water Resources Yangling 712100 Shaanxi China Key Lab of Northwest Water Resources and Environment Ecology of Ministry of Education Xi'an University of Technology Xi'an 710048 China Upper and Middle Yellow River Bureau Yellow River Conservancy Commission of the Ministry of Water Resources Xi'an 710021 China

To study the influences of terraced field construction and check-dam siltation on soil erosion of a watershed, we built a simplified watershed model for the Loess Plateau hilly-gully region including terraced fields, slope farmlands, steep-slope grasslands, and dam farmlands and defined three states of watershed （i.e., pioneer, intermediate, and climax stages, respec- tively）. Then, the watershed soil erosion moduli at various stages were studied by using a revised universal soil loss equation. Our results show that the pioneer and climax stages are the extreme states of watershed soil-and-water conservation and control; in the pioneer stage the soil erosion modulus was 299.56 t.ha-l.a 1 above the edge of gully, 136.64 t.ha-La-1 below the edge of gully, and 229.74 t.ha-~.a-~ on average; in the climax stage, the soil erosion modulus was 39.10 t.ha .a-1 above the edge of gully, 1.10 t.ha-La-1 below the edge of gully, and 22.81 t-ha-La-1 on average; in the intermediate stage, the soil erosion modulus above the edge of gully exhibited an exponential decline along with the increase in terraced field area percentage, while the soil erosion modulus below the edge of gully exhibited a linear decline along with the increase in siltation height.

关键词： soil-and-water conservation Revised Universal Soil Loss Equation succession the Loess Plateau

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Establishment of a sediment transport capacity equation on loessal slope via experimental investigation

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International Journal of Sediment Research 2023年第2期38卷 166-174页

作者： Tian Wang Jingsi li Jingming Hou Peng li Shengdong Cheng Feng Wang Wen Wang zhanbin li Reinhard Hinkelmann State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China Xi'an University of Technology Chair of Water Resources Management and Modeling of Hydrosystems Department of Civil Engineering Technische Universit at Berlin Shaanxi Province Institute of Water Resources and Electric Power Investigation and Design Key Laboratory of National Forestry Administration on Ecological Hydrology and Disaster Prevention in Arid Regions Xi'an University of Technology

Areliable sediment transport capacity function provides response against challenges of soil erosion prediction on the Loess Plateau of China. The popular sediment transport capacity functions are questionable on loess slopes because the experimental conditions from which they were derived, like bed materials, gentle slopes,and surface roughness, are different from soil erosion processes on the loess slopes. Due to the foregoing uncertainty, a suitable sediment transport capacity function was developed based on a flume experiment investigation. The erodible bed experiment was implemented for five unit width discharges(1.3 × 10-4-3.3 × 10-4m2/s) and ten slopes(5.2%-57.7%). The selected sediment transport capacity equations were tested in an applicability evaluation. The results of this evaluation found that the Govers(1990) function had the best performance(P.O.0.5-2.0= 76%, R2= 0.93, RMSE = 0.03 kg/(m·s)), followed by the Yalin(1963) function(P.O.0.5-2.0= 80%, R2= 0.81, RMSE = 0.05 kg/(m·s)), and finally by the Low(1989) function(P.O.0.5-2.0= 72%,R2= 0.79, RMSE = 0.04 kg/(m·s)), where P.O.0.5-2.0is the percentage of estimated values with logarithmic discrepancies with the measured value between 0.5 and 2.0; R2is the coefficient of determination and RMSE is the roof mean squares error. The cohesive sediment incipient motion velocity is introduced into the Govers(1990) function, and the sediment particle parameter is determined from measured experimental data. The developed sediment transport capacity equation has good performance with predicted values corresponding to measured values(P.O.0.5-2.0= 98%, R2= 0.98, RMSE = 0.006 kg/(m·s)). The research results provide an improved sediment transport capacity function on the basis of experiments for steep loessal slopes.

关键词： Experimental investigation Hydraulic conditions Loessal slope Sediment transport capacity

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An improved constant volume cycle model for performance analysis and shape design of PDRE nozzle

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Applied Mathematics and Mechanics(English Edition) 2018年第2期39卷 193-206页

作者： Guangyu li Xiaowei li Jue DING Peifen WENG zhanbin LU Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

An improved constant volume cycle （CVC） model is developed to analyze the nozzle effects on the thrust and specific impulse of pulse detonation rocket engine （PDRE）. Theoretically, this model shows that the thrust coefficient/specific impulse of PDRE is a function of the nozzle contraction/expansion ratio and the operating frequency. The relationship between the nozzle contraction ratio and the operation frequency is obtained by introducing the duty ratio, by which the key problem in the theoretical design can be solved. Therefore, the performance of PDRE can be accessed to guide the preliminary shape design of nozzle conveniently and quickly. The higher the operating frequency of PDRE is, the smaller the nozzle contraction ratio should be. Besides, the lower the ambient pressure is, the larger the expansion ratio of the nozzle should be. When the ambient pressure is 1.013 × 105 Pa, the optimal expansion ratio will be less than 2.26. When the ambient pressure is reduced to vacuum, the extremum of the optimal thrust coefficient is 2.236 9, and the extremum of the specific impulse is 321.01 s. The results of the improved model are verified by numerical simulation.

关键词： pulse detonation rocket engine （PDRE） nozzle specific impulse thrust,constant volume cycle （CVC） model

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Influences of sand cover on erosion processes of loess slopes based on rainfall simulation experiments

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Journal of Arid Land 2018年第1期10卷 39-52页

作者： ZHANG Xiang li zhanbin li Peng TANG Shanshan WANG Tian ZHANG Hui Post-doctoral Research Station of Xi'an Chan-Ba National Ecological District Xi'an 710024China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water ConservationChinese Academy of Science and Ministry of Water ResourcesYangling 712100China State Key Laboratory Base of Eco-Hydraulic Engineering in Arid Area Xi'an University of TechnologyXi'an 710048China

Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China. Understanding the composition, distribution, and transport processes of eroded sediments in these regions is of considerable scientific significance for controlling soil erosion. In this study, based on laboratory rainfall simulation experiments, we analyzed rainfall-induced erosion processes on sand-covered loess slopes （SS） with different sand cover patterns （including length and thickness） and uncovered loess slopes （LS） to investigate the influences of sand cover on erosion processes of loess slopes in case regions of aeolian-fluvial erosion. The grain-size curves of eroded sediments were fitted using the Weibull function. Compositions of eroded sediments under different sand cover patterns and rainfall intensities were analyzed to explore sediment transport modes of SS. The influences of sand cover amount and pattern on erosion processes of loess slopes were also discussed. The results show that sand cover on loess slopes influences the proportion of loess erosion and that the compositions of eroded sediments vary between SS and LS. Sand cover on loess slopes transforms silt erosion into sand erosion by reducing splash erosion and changing the rainfall-induced erosion processes. The percentage of eroded sand from SS in the early stage of runoff and sediment generation is always higher than that in the late stage. Sand cover on loess slopes aggravates loess erosion, not only by adding sand as additional eroded sediments but also by increasing the amount of eroded loess, compared with the loess slopes without sand cover. The influence of sand cover pattern on runoff yield and the amount of eroded sediments is larger than that of sand cover amount. Furthermore, given the same sand cover pattern, a thicker sand cover could increase sand erosion while a thinner sand cover could aggravate loess erosion. This difference explains the existence of intense erosion on slopes

关键词： aeolian-fluvial erosion sand-covered loess slopes sand cover amount sand cover pattern rainfall intensity grain-size distribution Inner Mongolia Reach of the Yellow River

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Temporal and spatial variation characteristics of extreme precipitation on the Loess Plateau of China facing the precipitation process

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Journal of Arid Land 2023年第4期15卷 439-459页

作者： ZHANG Yixin li Peng XU Guoce MIN Zhiqiang li Qingshun li zhanbin WANG Bin CHEN Yiting State Key Laboratory of Eco-Hydraulic in Northwest Arid Region Xi'an University of TechnologyXi'an 710048China Key Laboratory of National Forestry and Grassland Administration on Ecological Hydrology and Disaster Prevention in Arid Regions Northwest Survey and Planning Institute of National Forestry and Grassland AdministrationXi'an 710048China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Chinese Academy of Sciences and Ministry of Water ResourcesYangling 712100China

The preceding and succeeding precipitation(PSP)often act together with extreme precipitation(EP),in turn,causing floods,which is an objective component that is often overlooked with regard to summer flood hazards in the arid region of Northwest China.In this study,event-based extreme precipitation(EEP)was defined as continuous precipitation that includes at least one day of EP.We analyzed the spatiotemporal variation characteristics of four EEP types(front EEP,late EEP,balanced EEP,and single day EEP)across the Loess Plateau(LP)based on data acquired from 87 meteorological stations from 1960 to 2019.Precipitation on the LP basically maintained a spatial pattern of"low in the northwest region and high in the southeast region",and EP over the last 10 a increased significantly.The cumulative precipitation percentage of single day EEP was 34%and was dominant for 60 a,while the cumulative precipitation percentage of front,late,and balanced EEP types associated with PSP accounted for 66%,which confirms to the connotation of EEP.The cumulative frequencies of front and late EEP types were 23%and 21%,respectively,while the cumulative frequency of balanced EEP had the lowest value at only 13%.Moreover,global warming could lead to more single day EEP across the LP,and continuous EEP could increase in the northwestern region and decrease in the eastern region in the future.The concept of process-oriented EP could facilitate further exploration of disaster-causing processes associated with different types of EP,and provide a theoretical basis for deriving precipitation disaster chains and construction of disaster cluster characteristics.

关键词： temporal and spatial variation climate change extreme precipitation(EP) event-based extreme precipitation(EEP) Loess Plateau

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