Sediment Erosion on Pelton Turbines:A Review

The Pelton turbine has been widely used to develop high-head water resources with sediments because of its advantages in life cycle costs.When a flood or monsoon season occurs,the sediment concentration in the river increases suddenly,causing severe erosion to the nozzle,needle,and runner of Pelton turbines.After decades of development,researchers have developed practical engineering experience to reduce the sediment concentration of the flow through the turbine and ensure the safety and efficiency of power generation.Research on the mechanism of sediment erosion,development of anti-erosion materials,and establishment of erosion prediction models have attracted scholarly interest in recent years.Extensive research has been conducted to determine a complete and valuable syndication erosion model.However,owing to the complexity of the flow and wear mechanisms,the influence of specific parameters of erosion and the syndication effect is still difficult to determine.Computational fluid dynamics and erosion monitoring technology have also been evaluated and applied.This paper presents a comprehensive review of the erosion of Pelton turbines,some of the latest technical methods,and possible future development directions.

Numerical simulation on sand sedimentation and erosion characteristics around HDPE sheet sand barrier under different wind angles

For the safety of railroad operations,sand barriers are utilized to mitigate wind-sand disaster effects.These disasters,characterized by multi-directional wind patterns,result in diverse angles among the barriers.In this study,using numerical simulations,we examined the behavior of High Density Polyethylene(HDPE)sheet sand barriers under different wind angles,focusing on flow field distribution,windproof efficiency,and sedimentation erosion dynamics.This study discovered that at a steady wind speed,airflow velocity varies as the angle between the airflow and the HDPE barrier changes.Specifically,a 90°angle results in the widest low-speed airflow area on the barrier’s downwind side.If the airflow is not perpendicular to the barrier,it prompts a lateral airflow movement which decreases as the angle expands.The windproof efficiency correlates directly with this angle but inversely with the wind’s speed.Notably,with a wind angle of 90°,wind speed drops by 81%.The minimum wind speed is found at 5.1H(the sand barrier height)on the barrier’s downwind side.As the angle grows,the barrier’s windproof efficiency improves,extending its protective reach.Sedimentation is most prominent on the barrier’s downwind side,as the wind angle shifts from 30°to 90°,the sand sedimentation area on the barrier’s downwind side enlarges by 14.8H.As the angle grows,sedimentation intensifies,eventually overtakes the forward erosion and enlarges the sedimentation area.

Numerical simulation of flow field deposition and erosion characteristics around bridge-road transition section

Wind-sand flow generates erosion and deposition around obstacles such as bridges and roadbeds, resulting in sand damage and endangering railway systems in sandy regions. Previous studies have mainly focused on the flow field around roadbeds, overlooking detailed examinations of sand particle erosion and deposition patterns near bridges and roadbeds. This study employs numerical simulations to analyze the influence of varying heights and wind speeds on sand deposition and erosion characteristics at different locations: the bridge-road transition section(side piers), middle piers, and roadbeds. The results show that the side piers, experience greater accumulation than the middle piers. Similarly, the leeward side of the roadbed witnesses more deposition compared to the windward side. Another finding reveals a reduced sand deposition length as the vertical profile, in alignment with the wind direction, moves further from the bridge abutments at the same clearance height. As wind speeds rise, there’s a decline in sand deposition and a marked increase in erosion around the side piers, middle piers and roadbeds. In conclusion, a bridge clearance that’s too low can cause intense sand damage near the side piers, while an extremely high roadbed may lead to extensive surface sand deposition. Hence, railway bridges in areas prone to sandy winds should strike a balance in clearance height. This research provides valuable guidelines for determining the most suitable bridge and roadbed heights in regions affected by wind and sand.

Erosion and Sediment Production in Small Watershed in Purple Hilly Areas and Prevention Techniques

Purple Soil distributes extensively and mainly in China. Because of abundant easily weatherable parent rocks/ materials and unstable soil structure, and also influenced by parent materials, usage systems, and slope gradients, erosion and sediment production of purple soils are very severe with main fashions of water erosion and gravitational erosion. Basing on observed data in small watersheds, rainfall erosivity, vegetation coverage, previous soil water content, flow and relating factors such as climate, topograph of small watershed, land usage, and soil kinds are all the influence factors of erosion and erodibility of purple soil as well as sediment production and transport in small watershed of purple hilly areas. The effective technological countermeasures of ecosystem restoration, agricultural tillage for water conservation and erosion prevention, agriculture project, and soil changing for fertility and anti-erosion were provided.

Influence of Vegetation on Runoff and Sediment in Wind-water Erosion Crisscross Region in the Upper Yellow River of China

All characteristics of vegetation,runoff and sediment from 1960 to 2010 in the Xiliu Gully Watershed,which is a representative watershed in wind-water erosion crisscross region in the upper reaches of the Yellow River of China,have been analyzed in this study.Based on the remote sensing image data,and used multi-spectral interpretation method,the characteristics of vegetation variation in the Xiliu Gully Watershed have been analyzed.And the rules of precipitation,runoff and sediment's changes have been illuminated by using mathematical statistics method.What′s more,the influence mechanism of vegetation on runoff and sediment has been discussed by using the data obtained from artificial rainfall simulation test.The results showed that the main vegetation type was given priority to low coverage,and the area of the low vegetation coverage type was reducing year by year.On the country,the area of the high vegetation coverage type was gradually increasing.In a word,vegetation conditions had got better improved since 2000 when the watershed management project started.The average annual precipitation of the river basin also got slightly increase in 2000–2010.The average annual runoff reduced by 37.5%,and the average annual sediment reduced by 73.9% in the same period.The results of artificial rainfall simulation tests showed that the improvement of vegetation coverage could increase not only soil infiltration but also vegetation evapotranspiration,and then made the rainfall-induced runoff production decrease.Vegetation root system could increases the resistance ability of soil to erosion,and vegetation aboveground part could reduce raindrop kinetic energy and splash soil erosion.Therefore,with the increase of vegetation coverage,the rainfall-induced sediment could decrease.

Erosion and Sediment Disasters in Cambodia1

This report first gives a general description of Cambodia and then discusses its topographic and geological features. Finally, the current situation concerning erosion and sediment disasters is discussed.

Analysis of deposition and erosion of Dongting Lake by GIS

The sediments of the Dongting Lake come from four channels (one of them was closed in 1959), connected with the Yangtze River, four tributaries (Lishui, Yuanjiang, Zishui and Xiangjiang) and local area, and some of them are transported into the Yangtze River in Chenglingji, which is located at the exit of the Dongting Lake, some of them deposit into drainage system in the lake region and the rest deposit into the lake. The annual mean sediment is 166,555x104 t, of which 80% come from the four channels, 18% from the four tributaries and 2% from local area, whereas 26% of the total sediments are transported into the Yangtze River and 74% deposited into the lake and the lake drainage system. Based on topographic maps of 1974, 1988 and 1998, and the spatial analysis method with geographic information system (GIS), changes in sediment deposition and erosion are studied in this paper. By overlay analysis of 1974 and 1988, 1988 and 1998, erosion and sediments deposition areas are defined. The main conclusions are: (1) sediment rate in the lake is larger than erosion rate from 1974 to 1998. The mean deposition in the lake is 0.43 m; (2) annual sediment deposition is the same between 1974-1988 and 1988-1998, but the annual volume of deposition and erosion of 1988-1998 is bigger than that in 1974-1988; (3) before the completion of the Three Gorges Reservoir, there will be 7.82x108 m3 of sediments deposited in the lake, which would make the lake silted up by 0.33 m; (4) in the lake, the deposition area is found in the north of the east Dongting Lake, the south-west of the south Dongting Lake, and the east of the west Dongting Lake; while the eroded area is in the south of the east Dongting Lake, the middle of the south Dongting Lake, the west of the west Dongting Lake, as well as Xiangjiang and Lishui river flood channels.

Effects of Suspended Culture of the Seaweed Laminaria japonica Aresch on the Flow Structure and Sedimentation Processes

The culture of suspended kelp, such as Laminaria japonica Aresch, has arisen in nearshore areas for approximately 30 years since the 1980 s. This long-term activity has significant impact on the regional hydrodynamic and sedimentary environments. In this study the impact was investigated, based on synchronized multi-station data from continuous observations made within and around the culture area. In total, three current velocity profiles were identified inside and on the landward side of the culture area. Based on the current velocity profiles we calculated the boundary layer parameters, the fluxes of erosion/deposition, and the rate of sediment transport in different times at each observation site. Comparison between culture and non-culture periods showed that the presence of suspended kelp caused the reduction in the average flow velocity by approximately 49.5%, the bottom friction velocity by 24.8%, the seabed roughness length by 62.7%, and the shear stress and the flux of resuspended sediment by approximately 50%. From analyses in combination with the corresponding vertical variation of the suspended sediment distribution, it is revealed that the lifted sediments by resuspension is mixed with the upper suspended material, which will modify the regional distribution of suspended sediment. These changes in flow structure and sediment movement will accelerate seabed siltation, which corresponds to the changes in seabed erosion/deposition. However, under the influences of the seasonal changes in kelp growth the magnitude of change with the seabed siltation was not obvious inside the culture area, but a fundamental change was apparent around the culture area.

Re-evaluating the vertical mass-flux profiles of aeolian sediment at the southern fringe of the Taklimakan Desert, China

Reliable estimation of the mass-flux profiles of aeolian sediment is essential for predicting sediment transport rates accurately and designing measures to cope with wind-erosion. Vertical mass-flux profiles from seventeen wind-erosion events were re-evaluated using five typical models based on observed data obtained from a smooth bare field at the southern fringe of the Taklimakan Desert, China. The results showed that the exponential-function model and the logarithmic-function model exhibited the poorest fit between observed and predicted mass-flux profiles. The power-function model and the modified power-function model improved the fit to field data to an equivalent extent, while the five-parameter combined-function model with a scale constant（σ） of 0.00001 m（different from the σ value proposed by Fryear, which represented the height above which 50% of the total mass flux occurred） was verified as the best for describing the vertical aeolian sediment mass-flux profiles using goodness of fit（R2） and the Akaike Information Criterion（AIC） values to evaluate model performance. According to relationships among model parameters, the modified power model played a prominent explanatory role in describing the vertical profiles of the observed data, whereas the exponential model played a coordinating role. In addition, it was found that the vertical profiles could not be extrapolated using the five selected models or easily estimated using an efficient model without field observations by a near-surface sampler at 0 to 0.05 m.

Suspended sediment dynamics in the meltwater of Chhota Shigri glacier, Chandra basin, Lahaul-Spiti valley, India

Present study shows suspended sediment dynamics in the meltwater of Chhota Shigri glacier,Himachal Pradesh,India for different melt seasons during the period 2011-2014.Maximum suspended sediment concentration in the meltwater was found during the month of July 2011,2012 and 2014 constituting to 55.2%,48.3% and 46.9%,respectively.Whereas in 2013,maximum suspended sediment concentration was observed in August accounting for46.1% of the total.On the other hand,maximum suspended sediment load was monitored in the month of July 2011,2012 and 2014 constituting 59.5%,63% and 55.7% of the total,respectively.Whereas in2013,maximum suspended sediment load was observed in the month of August accounting for 49.8% of the total suspended sediment load.Annual distribution of suspended sediment concentration(SSC)and suspended sediment load(SSL)in the Chhota Shigri glacier shows higher value of SSC and SSL during the study period 2012 and 2013,which may be due to the presence of high glacial runoff and negative mass balance of the studied area during these time periods.Marked diurnal variation has been observed in the SSC of meltwater.Strong correlation was observed between SSC and SSL with discharge.On the other hand,SSC and SSL also showed strong exponential correlation with air temperature of the studied area.Sediment yield from the catchment of Chhota Shigri glacier is high during the peak melt season(July and August)and low during the late melt season(September and October).The average value of erosion rate for Chhota Shigri glacier basin during the study period 2011-2014 was calculated to be 1.1mm/yr,which is lower than the average erosion rate of other Himalayan glaciers such as Rakiot,Chorabari and Gangotri glaciers,which may be caused by its geological setting containing high erosion resistant rocks such as granite,granite gneiss and porphyritic granite.

喀斯特山地石漠化过程中地表地下侵蚀产沙特征

喀斯特地区特殊的地表、地下侵蚀产沙是引发石漠化发生发展的重要物理过程。以喀斯特山地石漠化过程中不同石漠化状况的裸坡面为研究对象,通过模拟其地表微地貌及地下孔(裂)隙构造特征,采用人工模拟降雨试验研究其地表及地下侵蚀产沙特征。结果表明:无石漠化、潜在石漠化和轻度石漠化的裸坡在相同条件下的地表产沙量总体上高于地下产沙量,且10 min降雨时段内地下产沙量在0~100 g之间。不同石漠化强度的裸坡地表、地下侵蚀产沙量均随雨强的增大而增加;小雨强(30~80 mm h^(-1))下,随着石漠化强度加剧其地表越不易发生侵蚀,而石漠化强度达到一定程度时(基岩裸露率40%)土壤流失以地下流失为主;大雨强(150 mm h^(-1))下,地表产沙量及其分配比例随基岩裸露率变化不明显,而地下产沙量则呈先增加后减小的变化且在基岩裸露率为30%时达到最大。不同石漠化强度的裸坡地表产沙量及其分配比例随地下孔(裂)隙度变化不明显,地下产沙量及其分配比例总体上随地下孔(裂)隙度增加而增加;在不同地下孔(裂)隙度下(1%~5%),地表、地下产沙量及其分配比例随基岩裸露率变化(10%~50%)差异较大。研究结果对认识喀斯特地区石漠化发生发展机制、揭示土壤侵蚀特征、防治地表地下水土流失具有重要的理论和现实意义。

紫色土坡面径流与侵蚀特征模拟试验研究

应用人工模拟降雨试验,对紫色土坡面径流与侵蚀特征进行了模拟试验研究。结果表明:紫色土坡面初始产流时间随着雨强的增大而减少,且在小雨强下坡度对初始产流时间的影响显著;紫色土坡面径流总量有随坡度和雨强的增加而增大的趋势,坡度较大时,雨强对径流总量影响不明显;紫色土坡面侵蚀总量随坡度和雨强的增大而增大,10°、15°、20°坡的侵蚀量较大,在3 106.03～8 117.09 g之间,故应在坡度≥10°的坡地上实施有效的水土保持措施。

黄土高原侵蚀产沙的地貌临界

从地貌学的角度,较为深入地研究了黄土高原侵蚀产沙的几个临界问题:坡地系统的产沙临界、河道系统的产沙临界、以及地貌发育阶段的临界问题等,对地貌临界在黄土高原侵蚀产沙中应用作了进一步的探讨。结果表明,在黄土高原地貌发育阶段的不同临界范围内,其产沙量是不同的,因此,研究地貌临界不仅蕴涵着比较深刻的哲学和科学理论意义,而且具有一定的实践意义。

Experimental Study of Hydrodynamic and Self-Buried Behavior of Submarine Pipeline with Perpendicular Spoilers

The spoiler is a kind of device to disturb current and promote burying.At present,all submarine pipeline spoilers at home and abroad are parallel spoilers,that is,the plane of the spoiler is parallel to the vertical plane of the pipeline axis.According to the results of indoor experiments,when the pipeline with the forward spoiler is installed perpendicular to the direction of water flow,the spoiler will accelerate the seabed erosion and cause the pipeline to endure downward pressure,which will eventually cause the pipeline self-buried to form a protection.However,when the pipeline direction is consistent with the flow direction,the self-buried behavior and protective effect is vanished.By aiming at the defect that the forward spoiler cannot be self-buried when the direction of the pipeline and the flow are basically parallel,the spoiler burying aid device perpendicular to the pipeline axis has been innovatively developed,and the hydrodynamic changes and sediment erosion characteristics near the pipeline after the installation of the device were studied based on the experiment.Results reveal that although the perpendicular spoiler cannot generate downforce,it can greatly increase the turbulent kinetic energy of the flow and the rate of sediment erosion.The larger the angle between the pipeline axis and the spoiler plane is,the larger the increase in turbulent energy will be.The increase in turbulent energy near the bed surface can reach up about 70%when the angle is 90°,while serious sediment erosion mainly occurs along both sides of the pipeline with a distance of about 2−4 times the pipe diameter.In the future,we can further explore the influence of the perpendicular spoiler size and installation position on the pipeline downforce and the effect of burying promotion.At the same time,field tests on the perpendicular spoiler burying aid device currently developed will conduct to observe the actual effect of perpendicular spoiler promoting pipeline scouring and burying,and improve submarine pipeline safety protection technology.

生草覆盖条件下不同降雨强度对紫色土坡面侵蚀产沙的影响

造林种草,增加植被覆盖度是防止土壤侵蚀的重要措施.通过人工模拟降雨试验,探讨生草覆盖下紫色土坡面侵蚀产沙的动态变化.结果表明,有生草覆盖的坡面径流含沙量较裸地的径流含沙量更快达到稳定状态;坡面侵蚀产沙率随覆盖度增加呈指数型递减,且坡下种草的减沙效果最好;覆盖度与降雨强度对坡面侵蚀产沙量的影响存在对比消长关系,但生草覆盖度对产沙量的影响小于降雨强度的变化对产沙量的影响.

上方来水来沙的异位侵蚀效应研究进展

上方来水来沙作为上下不同地貌部位之间水流能量传递的媒介和泥沙输移的载体,对下游侵蚀产沙过程具有重要影响,是土壤侵蚀研究的关键环节。以往研究多侧重于小流域泥沙来源以及上方来水来沙的异位沉积效应,对上方来水来沙的异位侵蚀效应研究相对较少。本文回顾了上方来水来沙异位侵蚀效应的研究方法,在总结归纳前人研究成果的基础上,首次提出了"异位侵蚀"的概念,从异位径流特征、侵蚀产沙等方面,分析了裸露坡面上方来水来沙的异位侵蚀效应,并对水土保持措施异位减蚀作用的研究进展进行了综述。在此基础上,进一步探讨了异位侵蚀研究中的热点和难点问题,提出可从明确异位侵蚀效应概念、探索异位侵蚀影响因素及其机理、阐明上方来水来沙异位侵蚀过程中水沙和能量传递特征、量化水土保持措施异位减蚀作用等4个方面进一步深入研究上方来水来沙的异位侵蚀效应。

崎岖列岛海区水沙特征及近期冲淤演变

利用1999年冬季水文泥沙观测资料,分析了崎岖列岛海区冬季水动力条件及悬沙特征;根据1998,2004,2005和2006年水下地形资料,计算了该海区冲淤量及冲淤速率,探讨了研究区域近年来冲淤演变的特征及规律,得出最近8年来海区总体呈冲蚀状态、岛链峡道西部水域和岛间汊道出现淤积的状况,出现这一状况的原因主要与长江入海泥沙减少和洋山港工程有关。洋山港堵汊工程改变了局部水动力环境,造成岛链峡道西部水域和岛间汊道的冲淤变化;长江入海泥沙减少和长江口、杭州湾大片围垦截沙,削减了对崎岖列岛海区的泥沙补给,导致了海区总体呈冲刷趋势。

A new ecological control method for Pisha sandstone based on hydrophilic polyurethane

The Pisha sandstone-coverd area is among the regions that suffer from the most severe water loss and soil erosion in China and is the main source of coarse sand for the Yellow River. This study demonstrated a new erosion control method using W-OH solution, a type of hydrophilic polyurethane, to prevent the Pisha sandstone from water erosion. We evaluated the comprehensive effects of W-OH on water erosion resistance and vegetation-growth promotion through simulated scouring tests and field demonstrations on the Ordos Plateau of China. The results of simulated scouring tests show that the water erosion resistance of W-OH treated area was excellent and the cumulative sediment yield reduction reached more than 99%. In the field demonstrations, the vegetation coverage reached approximately 95% in the consolidation-green area, and there was almost no shallow trenches on the entire slope in the treated area. In comparison, the control area experienced severe erosion with deep erosion gullies appeared on the slope and the vegetation coverage was less than 30%. This study illustrated that W-OH treatment can protect the Pisha sandstone from erosion and provide the vegetation seeds a chance to grow. Once the vegetation matured, the effects of consolidation-growth mutual promotion can efficiently and effectively improve the water erosion resistance and ecological restoration.

Canonical correlation analysis of hydrological response and soil erosion under moving rainfall

The impacts of rainfall direction on the degree of hydrological response to rainfall properties were investigated using comparative rainfall-runoff experiments on a small-scale slope(4 m×1 m),as well as canonical correlation analysis(CCA).The results of the CCA,based on the observed data showed that,under conditions of both upstream and downstream rainfall movements,the hydrological process can be divided into instantaneous and cumulative responses,for which the driving forces are rainfall intensity and total rainfall,and coupling with splash erosion and wash erosion,respectively.The response of peak runoff(Pr)to intensity-dominated rainfall action appeared to be the most significant,and also runoff(R)to rainfall-dominated action,both for upstream-and downstream-moving conditions.Furthermore,the responses of sediment erosion in downstream-moving condition were more significant than those in upstream-moving condition.This study indicated that a CCA between rainfall and hydrological characteristics is effective for further exploring the rainfall-runoff-erosion mechanism under conditions of moving rainfall,especially for the downstream movement condition.

Calculation method for sediment load in flood and non-flood seasons in the Inner Mongolia reach of the Yellow River

Based on an empirical sediment transport equation that reflects the characteristics of ＂more input, more output＂ for sediment-laden flow in rivers, a general sediment transport expression was developed, which can take into account the effects of upstream sediment input, previous cumulative sediment deposition, critical runoff for sediment initiation, and the differences in sediment particle sizes between the mainstream and tributaries. Then, sedi- ment load equations for non-flood and flood seasons for the sub-reaches from Bayangaole to Sanhuhekou and from Sanhuhekou to Toudaoguai, as well as the whole Inner Mongolia reach from Bayangaole to Toudaoguai, were formulated based on data collected between 1952 and 2010. The corresponding sediment deposition and the cumulative values at each river reach were calculated using the proposed sediment transport equations for the period 1952 to 2010 according to the principle of sediment conservation. Comparisons between the calculated and measured values using the proposed sediment load equations for the sub-reaches and the entire reach showed that the calculated sediment load and sediment deposition and the cor- responding cumulative values in the flood and non-flood seasons were in good agreement with the measured values. These results indicated that the proposed methods can be applied to calculate the sediment load and the associated sediment deposition in the flood and non-flood seasons for long-term trend analysis of sediment deposition in the Inner Mongolia reach of the Yellow River.