Hydrodynamic Intensity Research Articles

Research of heat and mass transfer parameters at drying poly (ethylene terephthalate) granules

In this article, drying characteristics were studied for polyethylene terephthalate (PET) granules. For data analysis, a modified quasistationary method was used. The values of the reduced time and the hydrodynamic intensity index were obtained for the generalized drying curve of the entire drying process in the temperature range from 120 to 185°C. The duration of the first drying period of PET granules was determined for all experiments.

The Study of Heat and Mass-Exchange Processes during the Drying of Granulate of Hydrophobic Polymers

In this article, the drying characteristics were studied for granules of hydrophobic polymers, in particular, poly (ethylene terephthalate). To analyze the data, the modified quasi-stationary method was used. A modified quasi-stationary method has been proposed to describe drying kinetics of particulate materials dried in convective dryers with active hydrodynamic regimes. Parameters of reduced time and hydrodynamic intensity index were obtained for the generalized drying curve. Equations with refined parameters can be used to calculate the drying time and determine the temporal change in moisture content and material temperature.

Мшанки (Bryozoa) северной части Баренцева моря: видовой состав, распределение, экология (по материалам экспедиций ММБИ 2016–2017 гг.).

The modern data about fauna of Bryozoa in the northern part of Barents Sea are obtained. The taxonomic and biogeographic composition, distribution features of bryozoan communities, and their quantitative indicators are analyzed. 124 Bryozoa species are identified in the samples, one of which (Uschakovia gorbunoviKluge, 1946) is a new for the Barents Sea fauna. It was found that the richness of the bryozoan fauna is determined by the variety of environmental conditions and depends on the bottom relief (and related factors: soil, hydrodynamic intensity and sedimentation) and the parameters of water masses.

The effect of groundwater velocities on sulfidation of arsenic-bearing ferrihydrite: Insight from column experiments

The sulfidation of Fe oxides/hydroxides has an important effect on the migration and transformation of As in groundwater. We examine the sulfidation of As (III)-bearing ferrihydrite and subsequent As repartitioning induced by sulfide in column experiments. Groundwater velocities has an obvious influence on sulfidation and the subsequent formation/transformation of secondary minerals. At a slower flow 1 pore volume·d-1), adsorbed As blocks the ferrihydrite surface, resulting in a slower sulfidation and thus slower generation of S0 and Fe2+. Mackinawite is subsequently generated by reaction of Fe2+ with excess sulfide and then reacts with S0 to form greigite. At a faster flow (5 pore volumes·d-1), stronger water elution results in desorption of much of the adsorbed As. Faster sulfidation produces considerable amounts of S0 and Fe2+ and restricts the formation of mackinawite. Fe2+ then adsorbs and catalyzes the conversion of residual ferrihydrite to hematite. The mackinawite also reacts with S0 to form pyrrhotite rather than greigite. Overall, heavy sulfidation does not effectively prevent the release of As caused by the reduction of ferrihydrite at either groundwater velocities. Sufficient As retention may be achieved by adjusting the hydrodynamic intensity of the system to determine the product of the sulfidation.

Organic geochemical and petrophysical characteristics of transitional coal-measure shale gas reservoirs and their relationships with sedimentary environments: A case study from the Carboniferous-Permian Qinshui Basin, China

The Carboniferous-Permian Qinshui Basin has shale gas resource potential. In this study, eighteen shale samples from two representative wells were analyzed to investigate the coal-measure shale reservoir characteristics and their relationships with the transitional sedimentary environments. The results show that controlled by sedimentary environments, the tidal flat and barrier-lagoon (TFBL) system is prone to developing more organic matter (OM) than the pro-delta and delta front (PDDF) and delta plain and fluvial (DPF) systems. Shale porosity is positively correlated with clay mineral content, but shows no obvious relationship with quartz content. However, biogenic quartz content exhibits a negative correlation with shale porosity, but has a positive correlation with shale brittleness in the PDDF system, while no obvious correlation between detrital quartz and reservoir quality is found in the TFBL system. In terms of its better preservation of pyrite, which improves shale reservoir brittleness, there is more enhancement of the shale reservoir quality within the TFBL system than the PDDF system. The coal-measure shale samples exhibit a positive logarithmic correlation between reservoir porosity and permeability due to the pore size distribution. In terms of micropores (pore size < 2 nm), interlaminar OM micropores and clay mineral micropores are mainly controlled by hydrodynamic intensity, while columnar OM micropores are dominated by TOC content. Compared with the PDDF and DPF systems, the TFBL system is prone to forming laminar structures of shale in response to the sedimentary environment changes, which favor pore network development. The results of this study aim to provide a basis for shale gas exploration in coal-measure intervals in the Qinshui Basin and other similar transitional basins.

The Effect of Dissolved Organic Matter (DOM) on the Release and Distribution of Endocrine-Disrupting Chemicals (Edcs) from Sediment under Hydrodynamic Forces, A Case Study of Bisphenol A (BPA) and Nonylphenol (NP).

Endocrine-disrupting chemicals (EDCs) that exist in the aquatic system bring severe environmental risks. In this study, we investigate the dissolved organic matter (DOM) effect on the release and distribution of EDCs under varied hydrodynamic conditions. A water chamber mesocosm was designed to simulate the hydrodynamic forces in a shallow lake. The contents of bisphenol A (BPA) and nonylphenol (NP) in colloid-bound and soluble phases were measured under four increasing hydrodynamic intensities that were 5%, 20%, 50%, and 80% of the critical shear stress. The total BPA and NP contents in overlying water grew linearly with the hydrodynamic intensity (R2 = 0.997 and 0.987), from 108.28 to 415.92 ng/L of BPA and 87.73 to 255.52 ng/L of NP. The exponential relationships of EDC content and hydrodynamic intensity in soluble phase (R2 = 0.985 of BPA and 0.987 of NP) and colloid phase (R2 = 0.992 of BPA and 0.995 of NP) were also detected. The DOM concentrations in colloid-bound phase (cDOM) and in soluble phase (sDOM) were measured and the linear relationships with BPA content (R2 = 0.967 of cDOM and 0.989 of sDOM) and NP content (R2 = 0.978 of cDOM and 0.965 of sDOM) were detected. We analyzed the ratio (αDOM) of sDOM and cDOM that grew logarithmically with the hydrodynamic intensity (R2 = 0.999). Moreover, the ratio (αEDCs) of BPA and NP contents in soluble and colloid-bound phases varied differently with αDOM. The results suggested that BPA tended to be in the soluble phase and NP tended to be in the colloid-bound phase due to the increasing value of αDOM.

Comparison of detrital mineral compositions between stream sediments of the Yangtze River (Changjiang) and the Yellow River (Huanghe) and their provenance implication

ABSTRACT A comparative comparative study on the detrital mineral composition of stream sediments of the Yangtze River (Changjiang) and Yellow River (Huanghe) shows that, light minerals of the Yangtze River basin were mainly quartz, feldspar, and detritus, the compositional characteristics of light minerals differed among tributaries, the main stream had a generally higher maturity index than tributaries; heavy mineral content tended to decrease progressively from the upper stream to lower stream of the Yangtze River, the primary assemblage was magnetite-hornblende-augite-garnet-epidote, and diagnostic minerals of different river basins were capable of indicating the nature and distribution of the source rock. Detrital mineral assemblages in sediments of tributaries and the main stream of the Yellow River were basically similar, Primary heavy mineral assemblage was opaque mineral-garnet-epidote-carbonate mineral and alteration mineral. Variations in the contents of garnet, opaque mineral, and hornblende mainly reflected the degree of sedimentary differentiation in suspended sediment and the hydrodynamic intensity of a drainage system. The heavy mineral differentiation index F revealed sedimentary differentiation of diagnostic detrital mineral composition due to changes in regional hydrodynamic intensity and can serve as an indicator for studying the dynamic sedimentary environment of a single-provenance river and the degree of sedimentary differentiation of its detrital minerals. Changes in detrital mineral content of the Yellow River was not completely controlled by provenance but reflected gravity sorting of the detrital mineral due to variations in the ephemeral river hydrodynamic intensity and sedimentary environment, however the index changing of Yangtze River were mainly influenced by the complex sediment sources. Therefore caution must be exercised in using the detrital mineral composition of marginal sea to determine the contribution of the Yangtze River and Yellow River. © 2019 China Geology Editorial Office.

The spatial discrepancy of Miocene transgression and its corresponding channel transformation pattern: A case study of the carabobo region in the northeast Venezuela basin

The Eastern Venezuela Basin serves as a world-class petroliferous basin, with the sedimentary environment controlled by interactions between the Caribbean and South American plates. This complex tectonic movement could have an important impact on the unsynchronized sedimentary evolution process and heterogeneous marine transgression of different regions within the basin. Thus, it is important to clarify the impact of interactions between the fluviatic- and marine-deposits on the development of the sedimentary environment, the transition of different delta types, and sand-body distribution within this complicated tectonic movement. Based on interpretation of 3D seismic data, electrical well-logging facies and analysis of the sedimentary characteristics of the core, we were able to identify the different sedimentary association types and understand the evolutionary process of the sedimentary system within the study area. We found that the differential sedimentary process in the eastern and western Carabobo block in the Eastern Venezuela Basin was caused by differential uplift and the corresponding spatial discrepancy transgression process in the Middle and Early Miocene foreland basins in this region. The flat geomorphology in the eastern Carabobo block contributed to the obvious sea level transgression process from North to South, but the uplift in the center of the western Carabobo block continuously blocked the sea level transgression. The different transgression processes led to the different sedimentary evolution processes in the eastern and western Carabobo blocks. In the eastern Carabobo block, braided river deltas (23.3–20.43 Ma) gradually changed into meandering river deltas (20.43–15.97 Ma) and finally into tide-influenced estuaries (15.97 Ma). However, in the western subsiding Carabobo block, impacted by the uplift in the center of this area, braided river deltas (23.3–15.97 Ma) in front of the uplift (adjacent to the sea) quickly changed into tide-influenced estuaries (15.97 Ma) with the generation of meandering distributary channels. However, the relatively weak transgression impacting the area behind the uplift resulted in braided channels being retained. Along with the evolution of the sedimentary environment, the tide-related deltaic distributary channel began to change from a braided channel to a meandering one. After rebuilding the paleo-hydrodynamic field, ancient geomorphology, and combining the hydrodynamic equations, we were able to quantitatively explain why sausage-shaped mouth bars occurred in the West and isolated mouth bars occurred in the East. Differential sedimentary environment evolution in eastern and western Carabobo is related to the spatial discrepancy of transgression, which resulted in the rate of change in hydrodynamic intensity, the direction of water flow confluence, and paleo-geomorphology.

Sedimentary evidence of outburst deposits induced by the Diexi paleolandslide-dammed lake of the upper Minjiang River in China

This study reveals that a distinct damming incident occurred during a prehistory period (approximately 30 ka BP) in the upper Minjiang River, at the southeastern margin of the Tibetan Plateau, which formed a giant dammed lake. It can be inferred that paleoseismic induced major landslides were the direct cause of the river damming. The dammed lake breached and caused a large outburst flood at about 27 ka BP. Between the section of the prehistoric ancient dam-body and its downstream areas (5 km), an abundance of diamicts consisting of a poor-sorted wide range of particle sizes, including gravel, sand, and minor silt and clay, have been observed. The outburst deposits in the Diexi area maybe divided into two periods: the thick outburst deposits represented the earlier and largest dammed-break event, and the deposit terrace was due to the subsequent and smaller dammed-break event. The sedimentary structures of the outburst deposits included imbrication, cavitation, matrix, and massive structures, as well as gravel support-stacked structures. Furthermore, a special sedimentary structure became evident, consisting of a rhythmite interbedded structure composed of a coarser gravel layer, and a finer sand and gravel layer, with no sand lens formed within the layers. This special structure can potentially provide an important original criterion for the outburst deposits in this area. The two types of facies associations have been recorded which indicate contrasting sediment transport regimes. The characteristics of boulder facies were most likely associated with hyperconcentrated flood flows. However, the finer-grained Gm/Gfm/GRm facies, which overlaid the Bcm facies, were determined to represent the waning stage of the flooding events. The delicate structures, as well as the absence of coarse components in the Sh facies, indicated an episode of accumulations, which was subsequent to the deposition of the underlying Bcm facies. The results of this study potentially provide important implications for the interpretation of the diamicts in the Diexi area. The grain-size frequency curves of the outburst deposits in the Diexi area were found to all be bimodal (a main peak and an inconspicuous sub-peak). These findings indicated a poorly sorted sedimentary structure. It was found that, from the upstream segment to the downstream segment, the gravel sediment became gradually lessened, while the fine-grained sediment increased. Additionally, the outburst flood hydrodynamic intensity was found to have gradually become weakened.

Assessment of hydrodynamic competence in extreme marine events through application of Boussinesq–Green–Naghdi models

Here in present work, rotational Boussinesq–Green–Naghdi models were applied to assess the hydrodynamic intensity through the study of the boulder transport in east coast of Philippines during typhoon Haiyan and damage to coastal residences in New Jersey coast due to hurricane Sandy. The hydrodynamic forces were quantitatively analyzed and correlated to both boulder transport distance and the structural damage state in the two cases. The boulder transport was found initiated at vicinity of infragravity swash bores. Inertial force generated by the acceleration in front of the bore was found increasingly large as boulder sizes increased therefore far from negligible as in some other literatures. Besides, transport distances were highly sensitive to wave-heights and boulder sizes, so that onshore positions might be a viable approach of identifying rough magnitudes of paleostorm before other information is available. Fragility functions to predict the damage state of coastal residences due to runups was derived and preliminary validated. Water velocity and the shielding parameter were identified as major predictors of damage while free board and water depth are relatively insignificant. Due to the relative lack of wind damage observed, nearshore hydrodynamics featuring instantaneous nonhydrostatic impact might be the persistent cause of massive littoral processes and low-level structural failure in coastal regions during extreme marine events. Nonhydrostatic phase-resolving models such as Boussinesq-type models would be necessary complements for the intermediate-scale assessment of marine hazards in coastal ocean.

Control of coal facies to adsorption-desorption divergence of coals: A case from the Xiqu Drainage Area, Gujiao CBM Block, North China

Adsorption and desorption of coal to methane are substantially related to coal facies, referring to the production potential of a coalbed methane (CBM) well. Based on analyses of the stratified channel samples from coal seams No. 2, No. 4 and No. 9 in the Xiqu Drainage Area, Gujiao CBM Block, North China, the relationship between coal facies and adsorption-desorption behaviors was first proposed and discussed. Using the coal facies diagrams suggested by previous investigators, four types of coal facies were distinguished in the coal seams, including the upper delta plain wet forest swamp (I), the lower delta plain fen (II), the lower delta plain marsh (III) and the back barrier low moor (IV). The upper delta plain wet forest swamp occurred dominantly, developing at the bottom and top of all the coal seams. Both the ash yield and groundwater index (GWI) tend to increase from coal facies I to IV, whereas the volatile compounds, fixed carbon, organic sulfur, total sulfur, micropore volume and specific surface area, tissue preservation index (TPI) and vegetation index (VI) decreased, which indicates changes in the vegetation types, water supplements and disturbance, acid-base properties and redox conditions in the paleomires. Paleomire evolution accompanied the rise and drop of the sea level, with a transgression or regression process that could be represented by the coal facies sequence. Coal seams No. 2, No. 4 and No. 9 were discriminated into two, three and two evolving stages, respectively, and these stages were characterized by complete cycles, except stage 4-I from the lower delta plain marsh. Mudstone partings in the coal seams deposited during the highest sea level. Collectively, paleomire environments, especially the variation of vegetation types and mire water condition, result in adsorption and desorption divergences among different coal facies. Arborescent plants decrease from coal facies I to IV as the hydrodynamic intensity increases, leading to corresponding changes in botanical tissue preservation, medium oxidizability, mineral content and, ultimately, adsorption and desorption behaviors. In view of the gas content and desorption capacity of the coal layers in the same coal seam, the layers from the upper delta plain wet forest swamp may have the best potential for CBM drainage, followed by those from the lower delta plain fen and marsh, while those from the back barrier low moor may have the worst potential.

Carbonate sedimentary characteristics of the beach rocks around Qilian Islets and Cays, Xisha Islands: Implication for coral reef development and decline

Beach rocks, developed on the coast of Qilian Islets and Cays, Xisha Islands, China, represent carbonate sedimentary formation on a typical biogenic coast adjacent to coral reef areas. The subaerial and submarine distribution and natural outcrop sections of beach rocks around three islets were surveyed, traced, measured and mapped to determine their development and depositional successions. Carbonate sedimentary characteristics of the beach rocks show that more than 95% of sediments are sourced from adjacent reef flat and reef crest, and are dominated by reef-building coral skeletal fragments and detritus, calcareous algae, and other skeletal grains of reef dwellers. Bioclastic content, algal and microbial content, sorting and roundness of skeletal grains and porosity in depositional successions change with sediment source, sediment accumulation rate, grain characteristics and textures of sediments, hydrodynamic intensity and cementation features. Cementation of the beach rocks is characterized by the binding action of algae and microbes, the micritization caused by boring of endolithic algae and microbes, the early marine cementation, and the early meteoric cementation. Algal and microbial activity played a major role in micritization of skeletal grains of beach rocks. The beach rock formation is mainly affected by the algal and microbial content in beach sediments, the sediment supply from reef flat, the grain characteristics of beach sediments, cementation and diagenesis process, the hydrodynamic intensity driven by wind and monsoons, and sea-level changes. The developmental dimensions and spatial extent of coral reef architecture, the flourishing and extinction of reef-building organisms in reef ecosystem, the abundance of algae and microbes and the diversity of reef dwellers may influence wave energy dissipation and sediment transport patterns in reef flat, thus alter the carbonate sediment budget of the coastal environment.

Dynamics of variability and mechanism of harmful cyanobacteria bloom in Lake Taihu, China

Eutrophication of lakes and harmful algae blooms are recently widespread water ecological environmental issues all over the world. Lake Taihu is a typical large shallow and eutrophic lake, and the cyanobacteria blooms induced by eutrophication have always been presenting high spatial-temporal variability and instability that made it very difficult to monitor and predict. Many previous publications have related to the eutrophication and cyanobacteria bloom with the most attention paid to phytoplankton growth, biomass increase and dominant species, while a few works addressed the appearance/disappearance of cyanobacteria bloom; however, none of them could explain the swift shift of cyanobacteria bloom in time and space in Lake Taihu. Based on the long-term field observation data and simulation experiments in Lake Taihu, here we presented a physical process controlled cyanobacteria bloom formation mechanism. In Lake Taihu, the visible cyanobacteria bloom occurrence was mainly controlled by the hydrodynamic intensity. When the cyanobacteria biomass accumulated in the water column, the large size colonies would increase during the process of cell division and proliferation, cells and colonies collisions, colonies aggregation (due to the stick extracellular polysaccharides) and disaggregation (due to the intensive turbulence). The bloom would occur if the wind influence decline and the colonies suspended at water column were able to float to the water surface to form bloom and scum. These colonies floating at the surface couldnot migrate downward because of the large size and great buoyancy; furthermore, they would drift to the downwind zone. But even the hydrodynamic process played the key role in the cyanobacteria bloom formation in this large shallow lake; it couldnot exclude the existence of other dynamics determining the cyanobacteria bloom formation. During the calm weather periods, the light controlled colonies diurnal migration, the zooplankton predation induced colony formation, and toxic materials induced colony aggregation, all would promote the cyanobacteria bloom formation. Thus these physiological induced cyanobacteria bloom occurrence modes and physical process controlled modes would alternatively take place in this large shallow lake. This revised cyanobacteria bloom occurrence dynamics in large eutrophic lake provided the possibility for forecasting and preventing the cyanobacteria bloom. Because Lake Taihu has been functioning as drinking water source for millions of around people, precise prediction and precaution of the bloom could increase the efficiency of cyanobacteria bloom collection, which had important practical significance for reducing the nutrient loading for reuse by cyanobacteria and decreasing the risk of cyanobacteria scum decaying induced drinking water pollution.

Agglomeration of Ni-Rich Hydroxide in Reaction Crystallization: Effect of Taylor Vortex Dimension and Intensity

The effect of a Taylor vortex flow on the agglomeration of Ni-rich hydroxide (Ni0.90Co0.05Mn0.05)(OH)2 was investigated in a Couette–Taylor (CT) crystallizer. The agglomeration process was found to be significantly affected by the rotation speed of the inner cylinder (hydrodynamic intensity) and gap size between the inner and outer cylinders of the CT crystallizer (vortex dimension), as these parameters affected the fluid shear and stability of the Taylor vortex flow. Thus, the agglomerate size was reduced when increasing the rotation speed and decreasing the gap size due to the increased fluid shear. A high rotation speed also improved the agglomerate size distribution and tap density. However, the agglomerate size distribution became broader and the tap density lower when decreasing the gap size, despite the increased fluid shear. This was due to an increase in the axial dispersion effect in the CT crystallizer when decreasing the gap size. As a result, the effective fluid motion of the Taylor vortex pr...

陆相碎屑岩中粘土矿物的形成机理及蚀变规律—以济阳坳陷始新统孔店组为例

粘土矿物是碎屑岩中重要的填隙物，对油气储层有着重要的地质意义。本文利用X衍射、扫描电镜、铸体薄片和电子显微镜等方法，对济阳坳陷始新统孔店组粘土矿物的特征、形成机理、蚀变规律及影响因素进行了研究。结果表明：济阳坳陷始新统孔店组所含粘土矿物主要为伊利石、高岭石、绿泥石和伊/蒙混层，伊利石在扫描电镜下呈蜂窝状、丝缕状和丝带状，高岭石呈书页状、蠕虫状，绿泥石呈叶片状、细鳞片状，伊/蒙混层则呈不规则细粒状、鳞片状；粘土矿物的形成机理可分为陆源碎屑粘土矿物形成机理和自身粘土矿物形成机理两种，陆源碎屑粘土矿物形成机理与水动力强度有关，自生粘土矿物的形成机理受地温，成岩流体性质的影响，在一定的温度下，成岩流体在碱性范围内易形成蒙脱石、伊利石、绿泥石而在酸性范围内则有利于高岭石的形成；古地温和成岩流体共同控制了粘土矿物的形成机理和蚀变过程，当地温为70℃~140℃时，蒙脱石和高岭石蚀变形成伊利石；当地温升高到100℃~140℃时，伊/蒙混层蚀变成伊利石；当成岩流体由酸性变为碱性时，高岭石蚀变形成绿泥石；当成岩流体碱性逐渐变强时，蒙脱石蚀变形成伊利石和绿泥石。 Clay minerals are the important fillings in clastic rocks, have important geological significance for oil and gas reservoir. In this paper, the characteristics, formation mechanism, alteration law and influence factors of the clay minerals in the new system of Jiyang Depression are studied by means of X diffraction, scanning electron microscopy, and electron microscopy. The results show: The Eocene Kongdian formation of clay minerals such as illite, kaolinite, chlorite and illite/smectite in Jiyang depression, Illite honeycomb, silk thread and ribbon shaped under the scanning electron microscope, a book like kaolinite, chlorite, wormlike, lobular flake, Illite/smectite irregular gra-nular, flake; The formation mechanism of clay minerals can be divided into mineral terrigenous detrital clay mineral formation mechanism and its mechanism of two kinds of clay. The formation mechanism of terrigenous detrital clay minerals associated with hydrodynamic intensity. The formation mechanism of the in-situ clay minerals is influenced by the temperature and the fluid properties. At a certain temperature, into the rock and fluid in the alkaline range to form mont-morillonite, illite and chlorite in the acidic range is conducive to kaolinite formation; The formation mechanism and alteration process of clay minerals are controlled by the paleo temperature and the formation of the fluid. When the temperature of the local temperature was 70 - 140, the montmorillonite and kaolinite altered to form illite; The local temperature rises to 100 - 140 DEG C, illite/smectite illite alteration; When the diagenetic fluid from acid to alkaline, kaolinite chlorite alteration was formed; When the alkaline diagenetic fluid gradually becomes stronger, montmo-rillonite alteration of illite and chlorite is formed.

Mass transfer in the apparatuses with preformed packing bodies

The article describes the various types of preformed and random packing for heat and mass transfer apparatuses, and determines their advantages and disadvantages. It is shown that preformed moving packing is of considerable interest to the intensification of heat and mass transfer processes due to the possibility of establishing regular vortex structure in the contact zone. There are represented the results of experimental studies of hydraulic resistance, coefficient of longitudinal mixing liquid, mass transfer coefficient in the gas and liquid phases in the apparatuses both with a preformed moving sheet and ball tips. Empirical equations for calculating main hydrodynamic and mass transfer intensity characteristics have been obtained.

Environmental changes in Chaohu Lake (southeast, China) since the mid 20th century: The interactive impacts of nutrients, hydrology and climate

Abstract Chaohu Lake, the fifth largest freshwater lake in the Yangtze floodplain, is faced with multiple stresses from anthropogenic disturbances and climate change. To explore the ecological changes in Chaohu Lake since the mid 20th century, we examined diatoms, geochemical indicators and particle size in 210 Pb-dated sediment core from the lake. Diatom succession revealed that the lake had switched to a eutrophic state since the late 1970s. Redundancy analysis using limnological data, hydrological and meteorological variables showed that sedimentary total phosphorus (TP) and total organic carbon (TOC), annual mean temperature, annual mean wind velocity, and water-level amplitude (WLA) were five significant factors influencing diatom succession. Diatom assemblages from 1950 till 1978 were driven by WLA and wind. The establishment of Chaohu Dam baffled hydrological connectivity between the lake and the Yangtze River in 1962, and reducing water exchange-induced flow. Meanwhile, weak wind velocity reduced the wind-induced flow in the 1960s. Due to the weak hydrodynamic intensity, the dominant species ( Aulacoseira granulata , a species with high sinking rate) became less important during this period. From 1979 till 2006, diatom assemblages were mainly driven by TP, TOC and temperature, which were highly correlative. Increasing nutrient loading promoted the blooms of eutrophic species (e.g., Cyclostephanos dubius ). In addition, rising temperature would indirectly influence diatom assemblages by mediating nutrient release process. As a consequence, multiple stresses in concert have caused the lake switch to a further eutrophic state indicated by prominent increases in more eutrophic species (e.g., Stephanodiscus parvus ) since 2000. This study provided information on complex trajectories of aquatic ecosystem shifts driven by increasing nutrient loading, hydrological alteration and climate warming in the Yangtze floodplain lake.

Physical simulation of hydrodynamic conditions in high rank coalbed methane reservoir formation

In order to select highly productive and enriched areas of high rank coalbed methane reservoirs, based on hydrologic geology as one of the main factors controlling coalbed methane (CBM) reservoir formations, the effect of hydrodynamic forces controlling CBM reservoir formations was studied by a physical simulation experiment in which we used CBM reservoir simulation facilities. The hydrodynamic conditions of high coal rank reservoirs in the Qinshui basin were analyzed. Our experiment shows the following results: under strong hydrodynamic alternating action, δC 1 of coalbed methane reservoir changed from the start at −2.95% ∼ −3.66%, and the lightening process occurred in phases; the CH 4 volume reduced from 96.35% to 12.42%; the CO 2 volume decreased from 0.75% in sample 1 to 0.68% in sample 2, then rose to 1.13% in sample 3; the N 2 volume changed from 2.9% in sample 1 to 86.45% in sample 3. On one hand, these changes show the complexity of CBM reservoir formation; on the other hand, they indicate that strong hydrodynamic actions have an unfavorable impact on CBM reservoir formation. It was found that the gas volume and hydrodynamic intensity were negatively correlated and low hydrodynamic flow conditions might result in highly productive and enriched areas of high rank CBM.

The morphology of cavitation damage of heat-treated medium carbon steel

In this paper the morphology of the cavitation damage to heat-treated medium carbon steel was analyzed. The experiments were conducted using a modified vibratory cavitation test set up. The erosion rates were measured by an analytical method. The morphology of the cavitation damage was studied by the scanning electron microscopy and optical microscopy techniques. The present work was aimed at understanding the cavitation erosion behavior of heat-treated medium carbon steel under laboratory conditions. The results indicate that the heat-treated medium carbon steel is not to be recommended for the production of hydraulic machinery parts exposed to high hydrodynamic intensity.

A Quasi-stationary Approach to Drying Kinetics of Fluidized Particulate Materials

A modified quasi-stationary method has been proposed to describe drying kinetics of particulate materials dried in convective dryers with active hydrodynamic regimes. Both our own results and literature data were used. These include sliced celery, cranberry, diced carrot, wheat and polystyrene granules dried in four types of dryers: pulsed fluid bed dryer, fluid bed dryer with a mixer, spouted bed dryer with a draft tube, and vortex dryer. The method was validated by comparing experimental data with results of modeling in terms of a reduced moisture content and material temperature. A new form of the generalized drying curve has been proposed with the reduced time and the index of hydrodynamic intensity as parameters. The equations developed can be used to calculate the total drying time and determine the temporal variation of the moisture content and material temperature.