Short Flow Paths Research Articles

A Study on Simulating Landslides Using Unity Software

The main rivers in Taiwan present numerous distinct features, such as narrow catchment areas, short main flow paths, fast-flowing rapids, and steep slopes. In Taiwan, typhoon season in summer and fall is the period during which torrential rainfall frequently occurs. Large amounts of rainfall in short periods increase the likelihood of disasters, such as hillside collapses, landslides, and floods. By using a computer simulation to visually present landslide disasters, disaster evacuation can be facilitated and casualties can be reduced. In the present study, we compiled the causes of hillside landslides by employing a remote helicopter equipped with a camera to capture images of landslide-prone rivers and hillsides. ReCap computation was adopted to establish 3D river and hillside models for mesh optimization, which were then imported into the Unity software. Finally, by referencing slope and geographical data, and considering various landside factors such as cause, scale, flow direction, flow speed, and damage, model disaster scenarios were created to perform simulations. The results were uploaded to Web-and mobile-based platforms, providing a reference for assisting the general public in implementing preventive measures, thereby reducing the occurrence of disaster incidents.

Manufacturing of polygon fiber reinforced plastic profiles by rotational molding and intrinsic hybridization

The manufacturing of lightweight shafts, pipes and profiles often uses hollow structures made from fiber reinforced plastics (FRP) due to their better density related properties. For applications with locally high tribological stresses, the use of FRP is not yielding proper results. In terms of lightweight construction, a hybrid design with a hollow FRP basic structure and local metallic elements in areas of high tribological stress is ideal for these applications. A promising approach for the production of these parts is rotational molding. Rotational molding for FRP–metal profiles is understood as a manufacturing process where machined, metallic elements and dry continuous fiber structures will be assembled and laid in a closed mold. Afterwards, the liquid matrix will be casted and the mold is then rotated at high speed until the fiber structure is fully impregnated and the matrix is cured. As there are short flow paths, this process is offering the potential to realize short cycle times of only a few minutes. Within this paper, the manufacturing of polygon profiles via rotational molding is described. These profiles can be produced by using centrifugal cores which were developed at the wbk Institute of Production Science. These cores are made of an elastomer composite material and they expand during the rotational molding process. The modeling of these cores and their impact on the impregnation pressure is shown here as well as their contribution in achieving higher fiber volume fractions.

Dissolved organic carbon lability increases with water residence time in the alluvial aquifer of a river floodplain ecosystem

AbstractWe assessed spatial and temporal patterns of dissolved organic carbon (DOC) lability and composition throughout the alluvial aquifer of the 16 km2 Nyack Floodplain in northwest Montana, USA. Water influx to the aquifer derives almost exclusively from the Middle Fork of the Flathead River, and water residence times within the aquifer range from days to months. Across seasons and channel discharge conditions, we measured DOC concentration, lability, and optical properties of aquifer water sampled from 12 wells, both near and ~3 m below the water table. Concentrations of DOC were typically low (542 ± 22.7 µg L−1; mean ± se), and the percentage of labile DOC averaged 18 ± 12% during 3 day laboratory assays. Parallel factor analysis of fluorescence excitation‐emission matrices revealed two humic‐like and two amino acid‐like fluorescence groups. Total DOC, humic‐like components, and specific UV absorbance decreased with water residence time, consistent with sorption to aquifer sediments. However, labile DOC (both concentration and fraction) increased with water residence time, suggesting a concurrent influx or production of labile DOC. Thus, although the carbon‐poor, oxygen‐rich aquifer is a net sink for DOC, recalcitrant DOC appears to be replaced with more labile DOC along aquifer flow paths. Our observation of DOC production in long flow paths contrasts with studies of hyporheic DOC consumption along short (centimeters to meters) flow paths and highlights the importance of understanding the role of labile organic matter production and/or influx in alluvial aquifer carbon cycling.

A study of the characteristics of karst groundwater circulation based on multi-isotope approach in the Liulin spring area, North China

Due to the significance of karst groundwater for water supply in arid and semi-arid regions, the characteristics of the karst groundwater flow system in the Liulin spring area, North China, are analysed through isotopic tracing (δ2H, δ18O, δ13C and 3H) and dating approaches (14C). The results show that the primary recharge source of karst groundwater is precipitation. Evaporation during dropping and infiltration of rainfall results in a certain offset in the values of δ2H and δ18O in groundwater samples from the global meteoric water line (GMWL) and the local meteoric water line (LMWL). The altitudes of the recharge region calculated by δ18O range from 1280 to 2020 m above sea level, which is consistent with the altitudes of the recharge area. The Liulin spring groups could be regarded as the mixing of groundwater with long and short flow paths at a ratio of 4:1. In the upgradient of the Liulin spring, the groundwater represents modern groundwater features and its is mainly derived from dissolution of soil CO2, while in the downgradient of the Liulin spring, the 14C age of dissolved inorganic carbon (DIC) in groundwater shows an apparent increase and is mainly derived from the dissolution of carbonate rocks. The mean flow rate calculated by 14C ages of DIC between IS10 and IS12 is 1.23 m/year.

The role of interbasin groundwater transfers in geologically complex terranes, demonstrated by the Great Basin in the western United States

In the Great Basin, USA, bedrock interbasin flow is conceptualized as the mechanism by which large groundwater fluxes flow through multiple basins and intervening mountains. Interbasin flow is propounded based on: (1) water budget imbalances, (2) potential differences between basins, (3) stable isotope evidence, and (4) modeling studies. However, water budgets are too imprecise to discern interbasin transfers and potential differences may exist with or without interbasin fluxes. Potentiometric maps are dependent on conceptual underpinnings, leading to possible false inferences regarding interbasin transfers. Isotopic evidence is prone to non-unique interpretation and may be confounded by the effects of climate change. Structural and stratigraphic considerations in a geologically complex region like the Great Basin should produce compartmentalization, where increasing aquifer size increases the odds of segmentation along a given flow path. Initial conceptual hypotheses should explain flow with local recharge and short flow paths. Where bedrock interbasin flow is suspected, it is most likely controlled by diversion of water into the damage zones of normal faults, where fault cores act as barriers. Large-scale bedrock interbasin flow where fluxes must transect multiple basins, ranges, and faults at high angles should be the conceptual model of last resort.

Effects of future urban and biofuel crop expansions on the riverine export of phosphorus to the Laurentian Great Lakes

Increased phosphorus (P) loadings threaten the health of the world's largest freshwater resource, the Laurentian Great Lakes (GL). To understand the linkages between land use and P delivery, we coupled two spatially explicit models, the landscape-scale SPARROW P fate and transport watershed model and the Land Transformation Model (LTM) land use change model, to predict future P export from nonpoint and point sources caused by changes in land use. According to LTM predictions over the period 2010–2040, the GL region of the U.S. may experience a doubling of urbanized areas and agricultural areas may increase by 10%, due to biofuel feedstock cultivation. These land use changes are predicted to increase P loadings from the U.S. side of the GL basin by 3.5–9.5%, depending on the Lake watershed and development scenario. The exception is Lake Ontario, where loading is predicted to decrease by 1.8% for one scenario, due to population losses in the drainage area. Overall, urban expansion is estimated to increase P loadings by 3.4%. Agricultural expansion associated with predicted biofuel feedstock cultivation is predicted to increase P loadings by an additional 2.4%. Watersheds that export P most efficiently and thus are the most vulnerable to increases in P sources tend to be found along southern Lake Ontario, southeastern Lake Erie, western Lake Michigan, and southwestern Lake Superior where watershed areas are concentrated along the coastline with shorter flow paths. In contrast, watersheds with high soil permeabilities, fractions of land underlain by tile drains, and long distances to the GL are less vulnerable.

Dry tree well flow assurance challenges and solutions for offshore gas condensate field development

Offshore field developments usually conceive that the dry tree wells (DTW) have less flow assurance challenges when compared with subsea development options. The relatively short vertical flow path for the DTW production risers causes fewer issues with respect to hydrate and wax management; however, the DTWs have particular flow assurance challenges due to dry tree well platforms design constraints. This extended abstract presents the various flow assurance challenges associated with the design and operation of DTWs for deepwater gas-condensate field developments, including: the impact of production riser annulus thermal behaviour and soil modelling uncertainties on the topsides materials selection; the coupling of low temperature propagation and cold liquid management issues topsides during cold well start-up; and, the narrow operating window to establish the forward flow for the downstream systems following cold well start-up. The absence of the capacity provided by subsea pipelines and flowlines, thus, leads to the requirement for integrated consideration of the DTWs and downstream topsides and potentially pipeline systems. The coupling for low temperature and liquid management issues, particularly for transient operations, requires rigorous flow assurance analysis. This extended abstract summarises the analytical solutions developed, applying the advanced flow assurance tools available, by considering the operating constraints, with the downstream process and export systems, to determine practical design solutions and operating philosophies.

Spawning tactics of summer chum salmon Oncorhynchus keta in relation to channel complexity and hyporheic exchange

Vertical hydraulic gradient, channel hydraulic, and substratum data were collected at active chum salmon redds to evaluate their influence on redd site selection in the Kwethluk River, a wandering gravel-bedded tributary of Alaska’s Lower Kuskokwim River. Two distinct summer chum salmon spawning tacitcs: primary- and off-channel groups spawning in different hydraulic and thermal environments. Channel hydraulics, ground-surface water exchanges, and bed sediment data were collected throughout the range of topographic conditions at sites occupied and unoccupied by spawners. Analyses of these data showed that redd site selection was incoherent with channel hydraulics and substratum size, when all channel types were considered. Rather, spawning was associated with the exchange of river and groundwater at four spatial scales. In primary channels, chum salmon spawned only in reaches where the regional hydraulic gradient (regional scale) promoted the penetration of river water, or downwelling, into the bed sediments. Within these reaches, primary-channel spawning was influenced by bed topography (fluvial scale) that promoted strong localized downwelling; a logit model, fitted to constituent hydraulics, discriminated between selected and unselected sites with 89 % accuracy. In contrast, spawners in off-channel habitats (flood and spring channels) selected areas of upwelling groundwater, regardless of channel hydraulics and the regional hydraulic gradient. In parafluvial flood channels, spawners selected localized upwelling associated with short groundwater flow paths (parafluvial scale). In spring channels, within the floodplain’s forested riparia (orthofluvial scale), spawners eschewed areas of localized downwelling and uniformly selected upwelling zones feeding these channels. Thus, redd selectivity differentiated two spawning tactics (groups) in this complex channel network where ground and surface water exchange is an important predictor of spawning habitat.

Eight emitters clogging characteristics and its suitability under on-site reclaimed water drip irrigation

Drip irrigation is the most effective and reliable method for reclaimed water irrigation. The water usually contains a lot of suspended particles, metal salt ions, organisms and microbial communities, which will enhance the possibility of emitter clogging or more complex clogging mechanism. Emitter clogging has become one of the key problems to the application and popularization of the drip irrigation technology. In this paper, we selected four kinds of pressure-compensating emitters and four kinds of non-pressure-compensating emitters, and executed the experiment of drip irrigation with on-site reclaimed water treated with cyclic activated sludge system (CASS). The emitter discharge ratio variation (Dra), coefficient of uniformity (CU) and clogging rate distribution were analyzed to evaluate the emitter clogging characteristics after eliminating the effect of temperature and pressure on the emitter outflow by data correction. The results showed that Dra and CU varied in three periods as system operation. The beginning of experiment was the fluctuated balance period, Dra and CU recurrent fluctuated in 5 %, and the emitters clogged at some spots after the system run 36–48 h. Then the two parameters varied linearly in 60–108 h, tuning into the initiate linear period, as the non-pressure-compensating emitters got an obvious linear change than the pressure-compensating ones with the gradient changed from −0.094 to 0.042 and −0.073 to 0.047, respectively. Some of the emitters have a significant difference on these two parameters at this stage. After the restarting in the second year, Dra and CU decreased sharply. The maximum decrement was, respectively, 9.6 and 10.7 %. Then they varied in line with a greater slope degree as all emitters reached the significant level, the gradient ranges were −0.176 to 0.115 and −0.216 to 0.117, respectively. This stage was called the accelerated linear period. Seriously clogged and completely clogged emitters appeared, and both Dra and CU dropped down to 38.7 and 41.5 %. Various degrees of clogged emitters often emerged in the end part of lateral at first then propelled to the head gradually, the completely clogged emitters in the end accounted for more than 73.0 % when the system run 540 h. Comprehensively considered, the pressure-compensating emitters and cusp-shaped saw-tooth non-pressure-compensating emitters with short flow path are recommended in reclaimed water drip irrigation. These researches are aimed to provide references explaining the emitter clogging mechanism of reclaimed water drip irrigation as well as its technological application and popularization.

Manifold microchannel heat sink design using optimization under uncertainty

A three-dimensional numerical model is developed and validated to study the effect of geometric parameters such as microchannel depth and width, manifold depth, and manifold inlet and outlet lengths on the performance of a manifold microchannel (MMC) heat sink. The manifold arrangement used to distribute the flow through alternating inlet and outlet pairs greatly reduces the pressure drop incurred in conventional fluid supply arrangements due to its shorter flow paths, while simultaneously enhancing the heat transfer coefficient by limiting the growth of thermal boundary layers. The computational analysis is performed on a simple unit-cell model to obtain an optimized design for uniform thermal boundary conditions, as well as on a porous-medium model to obtain a complete system-level analysis of multiple microchannels across one manifold. The porous-medium approach can be further modified to analyze the performance under asymmetrical heating conditions. Along with conventional deterministic optimization, a probabilistic optimization study is performed to identify the optimal geometric design parameters that maximize heat transfer coefficient while minimizing pressure drop for an MMC heat sink. In the presence of uncertainties in the geometric and operating parameters of the system, this probabilistic optimization approach yields a design that is robust and reliable, in addition to being optimal. Such an optimization analysis provides a quantitative estimate of the allowable uncertainty in input parameters for acceptable uncertainties in the relevant output parameters. The approach also yields information such as the local and global sensitivities which are used to identify microchannel width and manifold inlet length as the critical input parameters to which the outputs are most sensitive. The deterministic analysis shows that the heat transfer performance of the MMC heat sink is optimal at a manifold inlet to outlet length ratio of 3. A comparison between the deterministic and probabilistic optimization approaches is presented for the unit-cell model. A probabilistic optimization study is performed for the porous-medium model and the results thus obtained are compared with those of the unit-cell model for a uniform heat flux distribution.

Study on Operating Principle and Application of an Advanced Integrated Processing Technology - Air Lift Bioreactor (ALB) for Nitrogen and Phosphorus Removal

ALB integration is consisted of anaerobic hydrolysis regulating, anaerobic aerobic reaction, air-lift reflux circulating and suspension clarifying precipitate. It is a new compact energy-saving technology of active sludge nitrogen and phosphorus removal. Its properties include shorter flow path, less land used, lower construction cost, lower operation cost, less discharge sludge, easier management, more reliable operation and so on. It propitious to be used for small-scale sewage treatments.

Efficiency of rainwater harvesting of microcatchments and the role of their design

Microcatchment is a technique for collecting, storing and conserving local surface runoff in order to grow trees/shrubs. In this system, runoff water is generated on a plot and stored in the soil during runoff events, and trees/shrubs may utilize this water during the next dry season.Microcatchments have relatively small runoff generation areas (from dozens to hundreds sq. m) and are cheap and simple to implement Their collection area is usually a small depression located nearby the runoff generating area in which one or a few trees/shrubs may be planted Due to the short overland flow path runoff generation is efficient and even short low intensity storms may generate runoff. The drawback is however that due to the small size of the generating area small volumes of water are conveyed to the storage plots. Another drawback is susceptibility of the augmented water to evaporation. The main objective of present research presented hereafter was to estimate the effect the depth of the depression has on the efficiency of the water conservation in the soil profile. In the present study the storage plots were circular pits and the effect their depth had on evaporative losses and water distribution were studied.The results clearly show that the depth of the pit significantly affects evaporative water losses. The losses were separately computed for the soil cylinder whose upper surface is the bottom of the pit and for the surrounding shell. No differences between treatments were evident for losses from the inner cylinder. Significant differences in water losses were however observed for the surrounding shell where the shallow pits losing as much as six times more than the deeper pits.

Catchment-scale soil erosion and sediment yield simulation using a spatially distributed erosion model

Increasing rainfall intensity and frequency due to extreme climate change and haphazard land development are aggravating soil erosion problems in Korea. A quantitative estimate of the amount of sediment from the catchment is essential for soil and water conservation planning and management. Essential to catchment-scale soil erosion modeling is the ability to represent the fluvial transport system associated with the processes of detachment, transport, and deposition of soil particles due to rainfall and surface flow. This study applied a spatially distributed hydrologic model of rainfall–runoff–sediment yield simulation for flood events due to typhoons and then assessed the impact of topographic and climatic factors on erosion and deposition at a catchment scale. Measured versus predicted values of runoff and sediment discharge were acceptable in terms of applied model performance measures despite underestimation of simulated sediment loads near peak concentrations. Erosion occurred widely throughout the catchment, whereas deposition appeared near the channel network grid cells with a short hillslope flow path distance and gentle slope; the critical values of both topographic factors, providing only deposition, were observed at 3.5 (km) (hillslope flow path distance) and 0.2 (m/m) (local slope), respectively. In addition, spatially heterogeneous rainfall intensity, dependent on Thiessen polygons, led to spatially distinct net-erosion patterns; erosion increased gradually as rainfall amount increased, whereas deposition responded irregularly to variations in rainfall.

Experimental investigation of the effect of channel length on performance and water accumulation in a PEMFC parallel flow field

Longer channels within serpentine flow fields are highly effective at removing liquid water slugs and have little water accumulation; however, the long flow path causes a large pressure drop across the cell. This results in both a significant concentration gradient between the inlet and outlet, and high pumping losses. Parallel flow fields have a shorter flow path and smaller pressure drop between the inlet and outlet. This low pressure drop and multiple routes for reactants in parallel channels allows for significant formation of liquid water slugs and water accumulation. To investigate these differences, a polymer electrolyte membrane fuel cell parallel flow field with the ability to modify the length of the channels was designed, fabricated, and tested. Polarization curves and the performance, water accumulation, and pressure drop were measured during 15 min of 0.5 A cm −2 steady-state operation. An analysis of variance was performed to determine if the channel length had a significant effect on performance. It was found that the longer 25 cm channels had significantly higher and more stable performance than the shorter 5 cm channels with an 18% and an 87% higher maximum power density and maximum current density, respectively. Channel lengths which result in a pressure drop, across the flow field, slightly larger than that required to expel liquid water slugs were found to have minimal water accumulation and high performance, while requiring minimal parasitic pumping power. ► The effects of flow-field channel length on water accumulation and performance are investigated. ► Polarization curves are measured for 5 cm, 15 cm, and 25 cm parallel channel lengths. ► Performance, water accumulation, and pressure drop are measured during steady-state operation. ► Longer flow-field channels had higher and more stable performance, and decreased water accumulation.

Investigation of polymer electrolyte membrane fuel cell parallel flow field with induced cross flow

We present a novel idea to utilize a parallel channel design with a pressure difference between channels in an effort to maintain a short flow path, while attaining the cross flow inherent in serpentine flow fields. For this study, a polymer electrolyte membrane (PEM) fuel cell with the ability to control the back pressure on every other flow channel (high pressure channels, HPCs), in order to induce cross flow from the high pressure to the low pressure channels (LPCs), was designed and built. Polarization curves for different back pressures on the HPCs and for different stoichiometries on the cathode were measured. Performance gains were found at the end of the ohmic and mass transport loss regimes (voltages under 0.55 V). Secondly, the current density and net power (subtracting approximate pumping work) were determined based on HPC back pressure at steady state voltages of 0.5 V, 0.3 V, and 0.1 V. The parallel flow field with induced cross flow at the optimal back pressure had up to a 24% improvement in current density and a 14% improvement in net power over the standard parallel channel design.

Comparison of regional stream and lake chemistry: Differences, similarities, and potential drivers

We compared lakes and streams in northern Wisconsin to ask how regional patterns of water chemistry differed, and how ecosystem size relates to water chemistry. By applying traditional statistical approaches in novel ways, we identified factors influencing regional chemistry of lakes and streams. Chemistry differed significantly among the two ecosystem types (p = 0.01), and two distinct variable groups were apparent. Almost two thirds of the variation in 16 constituents was associated with concentration gradients related to groundwater inputs (group 1, represented by Ca) and adjacent wetlands (group 2, represented by dissolved organic carbon [DOC]). Largest differences were observed in groundwater‐associated variables. Median Ca concentrations in lakes were an order of magnitude lower than in streams (lake = 1.43 mg L−1, stream = 12.45 mg L−1), and indicate that regional lake chemistry is strongly influenced by precipitation or short groundwater flow paths, whereas streams are more affected by groundwater with substantial mineral water contact. In contrast, variables reflecting wetland influence (e.g., DOC) did not differ between streams and lakes. Despite these differences, as lake and stream size increased, their biogeochemical attributes converged, likely reflecting increased diversity of flow paths to larger systems, greater biogeochemical processing, and changes in landscape composition. Our results have identified critical differences (groundwater inputs) and similarities (organic carbon dynamics) between lakes and streams and emphasize the importance of ecosystem size in interpreting these observations at the regional scale. Studies such as this will provide essential pieces of information for regional and global biogeochemical studies of freshwater ecosystems.

Delineating volcanic aquifer recharge areas using geochemical and isotopic tools

Relative recharge areas are evaluated using geochemical and isotopic tools, and inverse modeling. Geochemistry and water quality in springs discharging from a volcanic aquifer system in Guatemala are related to relative recharge area elevations and land use. Plagioclase feldspar and olivine react with volcanically derived CO2 to produce Ca-montmorillonite, chalcedony and goethite in the groundwater. Alkalinity, Mg, Ca, Na, and SiO2(aq) are produced, along with minor increases in Cl and SO4 concentrations. Variations in groundwater δD and δ18O values are attributed to recharge elevation and used in concert with geochemical evolution to distinguish local, intermediate, and regional flow systems. Springs with geochemically inferred short flow paths provided useful proxies to estimate an isotopic gradient for precipitation (−0.67 δ18O/100 m). No correlation between spring discharge and relative flow-path length or interpreted recharge elevation was observed. The conceptual model was consistent with evidence of anthropogenic impacts (sewage and manure) in springs recharged in the lower watershed where livestock and humans reside. Spring sampling is a low-budget approach that can be used to develop a useful conceptual model of the relative scale of groundwater flow (and appropriate watershed protection areas), particularly in volcanic terrain where wells and boreholes are scarce.

Correlates of Arsenic Mobilization into the Groundwater in El Paso, Texas

This paper addresses the contamination of groundwater by arsenic, a naturally occurring phenomenon that has caused serious cases of arsenic poisoning around the world. While a number of chemical processes are known to be capable of mobilizing arsenic, the extent to which different processes are active in actual geological settings is much less clear. In this work, the El Paso, Texas region is analyzed as a case study to better understand the factors associated with high arsenic levels in groundwater. This study includes two basins that supply drinking water to approximately 2.5 million people. The average arsenic was 8.5 ppb, which is below the current American and WHO Maximum Contaminant Level of 10 ppb. However, arsenic concentrations reached approximately 80 ppb in three different locations. Governmental archival information was combined with field water sampling, and with leaching and analysis of solid phase materials from well cuttings (sediments of the aquifers). The study identifies evidence for both competitive desorption and reductive dissolution operating to mobilize arsenic, with the importance of different mechanisms likely varying throughout the aquifers. A mean of 21% of the solid arsenic content was leached out to solution at pH 9, and mean solid phase arsenic concentration was 4.3 ppm, solid phase iron 7000 ppm, and solid carbon 0.6%, consistent with arsenic desorption out of sediments into the aqueous phase. A potential role of geothermal waters was also identified at a southern hot spot. This information is important to better understand the basic science of the arsenic geochemical cycle and may also provide a rough guide as to where low arsenic waters may be found: groundwater with high potentiometric head and short flow paths, groundwater under the influence of surface water, and lower pH groundwater.

Manufacturing of Light Metal Matrix Composites by Combined Thermal Spray and Semisolid Forming Process – Summary of the Current State of Technology

The demand for lightweight structures in the automotive and aerospace industry increases permanently, and the importance of lightweight design principles is also increasing in other industrial branches, aiming towards improved energy efficiency and sustainability. Light metals are promising candidates to realize security relevant lightweight components because of their high specific strength; and amongst them, aluminum alloys are the most interesting materials due to their high plasticity and strain to failure, good processability, passivation in oxygen containing atmosphere, and low cost. However, for many applications, their stiffness as well as strength and fatigue behavior at elevated temperature are insufficient. Metal matrix composite (MMC) formation by integration of reinforcements in the form of continuous or discontinuous (short) fibers can yield a high increase in the alloys’ specific mechanical properties at room temperature and at elevated temperature. The integration of fibers with conventional manufacturing techniques like squeeze casting, hot pressing or diffusion bonding leads to restrictions in the component’s geometry. Moreover, these techniques result in elevated process costs mainly caused by long cycle times and the need of additional protective fiber coatings. In the present paper, an alternative method for the manufacturing of aluminum matrix composites is described, combining thermal spraying and semisolid forming (thixoforging) technologies for the formation of fiber prepregs and subsequent forming with simultaneous densification. Therefore, prepregs with the matrix alloy as a thick surface coating on the reinforcement fibers are manufactured in a fast, automated coating process, while reheating, densification and shaping are performed in a separate process, allowing an optimization of both processes towards cycle times and resulting material properties. Continuous fiber and short fiber reinforced aluminum matrix composites are manufactured using woven or parallel arranged continuous fibers, or short fibers as a fleece or fiber paper material. For the coating process, twin-wire electric arc spraying is applied as a well established, cost efficient thermal spray technology. The coating process is optimized towards microstructure of the matrix alloy prior to semisolid forming, which requires a globular alloy microstructure, and reduced fiber damage during the high-temperature liquid melt deposition. The thermally sprayed fine-grained matrix material enables semisolid forming at liquid contents of 40-60 vol% of the alloy, with short flow paths, reduced mechanical loads and short cycle times. Thus, limited fiber damage and residual stresses will occur, leading to good mechanical material properties. A production line for industrial-scale coating of fiber fabric coils in a continuous process is introduced in order to provide prepregs of various fiber-reinforcement materials and fiber architectures; moreover, a winding equipment for simultaneous fiber winding and coating is presented that enables local reinforcement for components with adapted, tailored composite material design.

Effect of draw solution concentration and operating conditions on forward osmosis and pressure retarded osmosis performance in a spiral wound module

Forward osmosis (FO) and pressure retarded osmosis (PRO) are concentration-driven membrane processes. While they can be potentially used in water, wastewater, and energy applications, these processes suffer from the concentration polarization inside the porous membrane support resulting in severe flux decrease, a phenomenon known as internal concentration polarization (ICP). Researchers have investigated the effect of ICP both in theoretical and experimental studies. The current study extends the existing ICP model to include the effect of draw solution dilution by membrane permeate flow in a spiral wound FO module (SWFO). FO and PRO experiments were performed using a Hydrowell ® SWFO under both submerged and cross-flow conditions. The effect of draw solution concentration, draw solution flow rate, feed water flow rate, and membrane orientation on FO and PRO water flux performance was systematically investigated. Permeate flow increased with greater draw solution concentration in both FO and PRO modes. ICP was found to drastically limit the available membrane flux in the concentration-driven membrane processes, and its adverse effect was more severe at greater draw solution concentration. Membrane flux was also affected by the dilution of draw solution when the permeate flow rate was comparable or greater than the draw solution flow rate. The submerged FO configuration performed nearly as good as the cross-flow configuration with feed water circulating outside of the membrane envelope (shorter flow path). In this case, the feed water flow rate only had limited effect on membrane flux likely due to its low mass transfer resistance. In contrary, the membrane flux can be adversely affected at low feed water flow rate when it was circulated inside of the membrane envelope (longer flow path).