Simulating Climate Change Impacts on the Recharge Dynamics of a Mediterranean Karst Aquifer

2020 ◽  
Author(s):  
Lysander Bresinsky ◽  
Jannes Kordilla ◽  
Emanuel Thoenes ◽  
Thibault Würsch ◽  
Irina Engelhardt ◽  
...  
Keyword(s):  
High Performance ◽  
Overland Flow ◽  
Karst Aquifer ◽  
Extreme Rainfall ◽  
Small Scale ◽  
Surface Zone ◽  
Dry Valleys ◽  
Flow Through ◽  
Infiltration Excess ◽  
The Impact

<p><span>Integrated surface-subsurface flow models </span><span>solving the Richards’ equation </span><span>allow t</span><span>o simulate</span><span> flow within all compartments (e.g. vadose, phreatic and surface zone) and their reciprocal interaction, </span><span>and </span><span>provid</span><span>e</span><span> a useful tool to investigate the impact of climatic changes on infiltration dynamics. The Mediterranean karst aquifers are in particular prone to shifting climates, as a decrease in mean precipitation with increasing intensity and frequency of short-duration extreme rainfall, may have a significant impact on recharge dynamics and the overall water budget. Here, we use the finite element, distributed, multi-continuum flow simulator HydroGeoSphere (Aquanty, 2015) on a high-performance-computing platform to simulate infiltration and groundwater flow of the Western-Mountain-Aquifer (WMA) c</span><span>onsidering</span><span> chang</span><span>ing</span><span> hydrologic conditions. A thin soil cover and abundant exposed bare karstic carbonate rock compose the recharge area, providing efficient pathways </span><span>for</span><span> fast direct infiltration along karst features (e.g., sinkholes and dolines). The lowered total annual precipitation may not result in a decrease in recharge since the severity and frequency of individual rainfall storms are projected to increase. </span></p><p><span>To account for the duality of karst flow dynamics, both in the vadose and phreatic zones, with rapid flow through conduits and slow flow through the fractured rock matrix, we apply a double-continuum approach based on the volume-effective Richards’ equation with van Genuchten parameters. A 2-D friction-based overland flow continuum, coupled via a first-order exchange term to the subsurface, accounts for overland flow d</span><span>ue</span> <span>to</span><span> infiltration excess. This allows t</span><span>o represent</span><span> the partitioning of rainfall into diffuse and rapid direct recharge, e.g., along dry valleys or sinkholes. This modeling approach, therefore, accounts for complex spatially distributed infiltration characteristics of the rock-soil landscape, with focused recharge along karst features and transmission losses of ephemeral streams (wadis) under variable precipitation patterns.</span></p><p>To get a better understanding of the complex interaction dynamics of the surface and subsurface domain in a coupled unsaturated single- and dual-continuum model we carried out small-scale process-oriented studies. Two types of synthetic karst features, (1) a dry valley averaged from field data (i.e., Wadi Natuf) and (2) an analytical generalized doline, were investigated. Geometries close to natural systems, such as sub-catchments of the WMA, were implemented. Sensitivity studies reveal complex dependencies of domain properties on linear- and log-scales. However, the exchange parameters controlling the coupling between the subsurface continua are insensitive.</p>

The impact of ionic strength on the molecular weight distribution (MWD) of lignin dissolved during softwood kraft cooking in a flow-through reactor

Holzforschung ◽  
2016 ◽  
Vol 70 (6) ◽  
pp. 495-501 ◽  
Author(s):  
Binh T.T. Dang ◽  
Harald Brelid ◽  
Hans Theliander
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Average Molecular Weight ◽  
Ion Concentration ◽  
Small Scale ◽  
Kraft Cooking ◽  
Flow Through ◽  
Cooking Times ◽  
The Impact

Abstract The molecular weight distribution (MWD) of dissolved lignin as a function of time during kraft cooking of Scots pine (Pinus silvestris L) has been investigated, while the influence of sodium ion concentration ([Na+]) on the MWD was in focus. The kraft cooking was performed in a small scale flow-through reactor and the [Na+] was controlled by the addition of either Na2CO3 or NaCl. Fractions of black liquors (BL) were collected at different cooking times and the lignin was separated from the BL by acidification. The MWD of the dissolved lignin was analyzed by GPC. Results show that the weight average molecular weight (Mw) of dissolved lignin increases gradually as function of cooking time. An increase of [Na+] in the cooking liquor leads to Mw decrement. Findings from cooks with constant and varying [Na+] imply that the retarding effect of an increased [Na+] on delignification is related to the decrease in lignin solubility at higher [Na+].

scholarly journals Urban Flood Event and Associated Damage in the Benue Valley, Nigeria

2021 ◽  
Author(s):  
Temi Ologunorisa ◽  
Obioma Ogbuokiri ◽  
Adebayo Oluwole Eludoyin
Keyword(s):  
Flood Control ◽  
Overland Flow ◽  
Standardized Precipitation Index ◽  
Flood Damage ◽  
Geographical Information ◽  
Flood Event ◽  
Discharge Data ◽  
Precipitation Concentration Index ◽  
Infiltration Excess ◽  
The Impact

Abstract Flooding events in the Lower Benue valley of Nigeria are often associated with huge damage to properties and loss of life in the adjoining communities. Specific objective of this study is to evaluate the impact of 2017 flood event as typical of the study area. Method used was an integrated environmental approach that combines analysis of rainfall and discharge data with social surveys, remote sensing and geographical information system. Standardized Precipitation Index (SPI), Precipitation Concentration Index (PCI) as well as flood damage curves were analysed with landuse/cover change and soil data to establish the nature of the flood and its impacts. Result showed that the flood in the study area is essentially saturation overland flow, which is more associated with saturation-excess than infiltration excess flow, and that the flood events are recurrent and predictable. 85% of the affected residents are however poor, earning an equivalent of US $4.3 daily, and live in non-reinforced concrete masonry (64%) and wooden buildings (24%). Many of the affected communities lived within flood plain and most buildings were structurally deficient. Victims received no compensation, and the properties were generally uninsured. The study recommends extensive flood control policy for the area and similar flood-prone communities.

scholarly journals Impacts of climate change on groundwater flooding and ecohydrology in lowland karst

2021 ◽  
Vol 25 (4) ◽  
pp. 1923-1941
Author(s):  
Patrick Morrissey ◽  
Paul Nolan ◽  
Ted McCormack ◽  
Paul Johnston ◽  
Owen Naughton ◽  
...  
Keyword(s):  
Climate Change ◽  
Agricultural Land ◽  
Karst Aquifer ◽  
Global Climate Models ◽  
Small Scale ◽  
Wetland Ecosystems ◽  
Extreme Flooding ◽  
Karst Systems ◽  
The Impact ◽  
Impacts Of Climate Change

Abstract. Lowland karst aquifers can generate unique wetland ecosystems which are caused by groundwater fluctuations that result in extensive groundwater–surface water interactions (i.e. flooding). However, the complex hydrogeological attributes of these systems, linked to extremely fast aquifer recharge processes and flow through well-connected conduit networks, often present difficulty in predicting how they will respond to changing climatological conditions. This study investigates the predicted impacts of climate change on a lowland karst catchment by using a semi-distributed pipe network model of the karst aquifer populated with output from the high spatial resolution (4 km) Consortium for Small-scale Modelling Climate Lokalmodell (COSMO-CLM) regional climate model simulations for Ireland. An ensemble of projections for the future Irish climate were generated by downscaling from five different global climate models (GCMs), each based on four Representative Concentration Pathways (RCPs; RCP2.6, RCP4.5, RCP6.0 and RCP8.5) to account for the uncertainty in the estimation of future global emissions of greenhouse gases. The one-dimensional hydraulic/hydrologic karst model incorporates urban drainage software to simulate open channel and pressurised flow within the conduits, with flooding on the land surface represented by storage nodes with the same stage volume properties of the physical turlough basins. The lowland karst limestone catchment is located on the west coast of Ireland and is characterised by a well-developed conduit-dominated karst aquifer which discharges to the sea via intertidal and submarine springs. Annual above ground flooding associated with this complex karst system has led to the development of unique wetland ecosystems in the form of ephemeral lakes known as turloughs; however, extreme flooding of these features causes widespread damage and disruption in the catchment. This analysis has shown that mean, 95th and 99th percentile flood levels are expected to increase by significant proportions for all future emission scenarios. The frequency of events currently considered to be extreme is predicted to increase, indicating that more significant groundwater flooding events seem likely to become far more common. The depth and duration of flooding is of extreme importance, both from an ecological perspective in terms of wetland species distribution and for extreme flooding in terms of the disruption to homes, transport links and agricultural land inundated by flood waters. The seasonality of annual flooding is also predicted to shift later in the flooding season, which could have consequences in terms of ecology and land use in the catchment. The investigation of increasing mean sea levels, however, showed that anticipated rises would have very little impact on groundwater flooding due to the marginal impact on ebb tide outflow volumes. Overall, this study highlights the relative vulnerability of lowland karst systems to future changing climate conditions, mainly due to the extremely fast recharge which can occur in such systems. The study presents a novel and highly effective methodology for studying the impact of climate change in lowland karst systems by coupling karst hydrogeological models with the output from high-resolution climate simulations.

scholarly journals Impact of overland flow on soil characteristics in Třebsín experimental plots

2017 ◽  
Vol 12 (No. 3) ◽  
pp. 187-193
Author(s):  
H. Bačinová ◽  
P. Kovář
Keyword(s):  
Overland Flow ◽  
Extreme Rainfall ◽  
Field Capacity ◽  
Rainfall Runoff ◽  
The Czech Republic ◽  
Physically Based ◽  
Runoff Discharge ◽  
The Impact ◽  
First Time ◽  
Experimental Plots

This paper describes the continuation of simulated outcomes from the plots No. 4 and No. 5 with two different soils, using the KINFIL model to assess the runoff from extreme rainfall. The KINFIL model is a physically-based, parameter-distributed 3D model that has been applied to the Třebsín experimental station in the Czech Republic. This model was used for the first time in 2012 to simulate the impact of overland flow caused by natural or sprinkler-made intensive rains on four of the nine experimental plots. This measurement of a rain simulator producing a high-intensity rainfall involves also hydraulic conductivity, soil sorptivity, plot geometry and granulometric curves to be used for the present analysis. However, since 2012, the KINFIL model has been amended to provide a more effective comparison of the measured and computed results using the values of new parameters such as storage suction factor and field capacity on plot 4 and plot 5. The KINFIL model uses all input data mentioned above, and it produces the output data such as gross rainfall, effective rainfall, runoff discharge hydraulic depths, hydraulic velocities and shear velocities as well as shear stress values depending on the soil particle distribution. These processes are innovative, physically based, and both the measured and the computed results fit reliably.  

Apparent impact sound insulation performance of cross laminated timber floors with floating concrete toppings

2021 ◽  
Vol 263 (1) ◽  
pp. 5203-5215
Author(s):  
Jianhui Zhou ◽  
Zijian Zhao
Keyword(s):  
High Performance ◽  
Dynamic Stiffness ◽  
Steel Structures ◽  
Bending Stiffness ◽  
Sound Insulation ◽  
Small Scale ◽  
Cross Laminated Timber ◽  
Mass Timber ◽  
The Impact ◽  
Insulation Performance

Mass timber buildings are gaining increasing popularity as a sustainable alternative to concrete and steel structures. Mass timber panels, especially cross-laminated timber (CLT), are often used as floors due to their dry and fast construction. CLT has poor impact sound insulation performance due to its lightweight and relatively high bending stiffness. Floating concrete toppings are often applied to increase both the airborne and impact sound insulation performance. However, the impact sound insulation performance of floating concrete toppings on CLT structural floors is affected by both the concrete thickness and resilient interlayer. This study investigated the efficiency of both continuous and discrete floating floor assemblies through mock-up building tests using small-scale concrete toppings according to ASTM E1007-16. It was found that the improvements by continuous floating floor assemblies are dependent on the concrete thicknesses and dynamic stiffness of resilient interlayers. The improvements cannot be well predicted by the equations developed for concrete structural floors. The highest apparent impact sound insulation class (AIIC) achieved with continuous floating floor assemblies in this study was 53 dBA, while that of the discrete floating floor assemblies was up to 62 dBA. The discrete floating floor solution showed great potential for use in mass timber buildings due to the high performance with thinner concrete toppings.

Studies of the thermal protective performance of fabrics under fire exposure: from small-scale to hexagon tests

2017 ◽  
Vol 88 (20) ◽  
pp. 2339-2352 ◽  
Author(s):  
Sumit Mandal ◽  
Simon Annaheim ◽  
Thomas Pitts ◽  
Martin Camenzind ◽  
René M Rossi
Keyword(s):  
Heat Transfer ◽  
High Performance ◽  
Radiant Heat ◽  
Air Permeability ◽  
Small Scale ◽  
Fire Exposure ◽  
Thermal Protective Performance ◽  
Flash Fire ◽  
Protective Performance ◽  
The Impact

This study aims to investigate the thermal protective performance of fabrics used in firefighters' clothing under high-intensity fire exposure. The performance of thermal protective fabric systems with different physical properties was evaluated under laboratory simulated fire exposure. Additionally, the influence of the configuration of the fire exposure tests and modes of heat transfer through the fabrics was also thoroughly investigated. The protective performance was evaluated using the standard small-scale flame [International Organization for Standardization (ISO) 9151:1995] and radiant heat (ISO 6942:2002) exposure tests. Additionally, the protective performance was evaluated under flash-fire exposure using a newly developed hexagon test. The protective performance values obtained from the small-scale (flame and radiant heat) and hexagon (flash fire) tests were compared and discussed. It has been found that a multi-layered fabric with high weight, thickness, and thermal resistance can significantly and positively affect the protective performance. If the air permeability of this fabric is high, it can show a lower protective performance; however, the impact of air permeability on the protective performance is insignificant especially in the case of the hexagon test. Notably, the protective performance can differ under two types of small-scale tests − flame and radiant heat. Also, this protective performance value is generally higher in the case of hexagon test in comparison with the small-scale tests. These differences in protective performance are mainly due to the unique configurations of these tests and/or different modes of heat transfer through the tested fabrics. The findings from this study will guide textile or materials engineers in the design and selection of materials for high performance thermal protective clothing; in turn, it will improve the occupational health and safety for firefighters.

scholarly journals Analysis of flood propagation and its impact on Negeri Lima Village due to the failure of Way Ela Dam

2019 ◽  
Vol 270 ◽  
pp. 04011
Author(s):  
Bagus Pramono Yakti ◽  
Mohammad Bagus Adityawan ◽  
Iwan Kridasantausa Hadihardaja ◽  
Yadi Suryadi ◽  
Joko Nugroho ◽  
...  
Keyword(s):  
Numerical Model ◽  
Overland Flow ◽  
Extreme Rainfall ◽  
Disaster Risk ◽  
Small Scale ◽  
Two Dimensional ◽  
High Rainfall ◽  
Public Facilities ◽  
Natural Dam ◽  
The Government

Way Ela dam is a dam to be built in the Negeri Lima village. In the negeri lima village there was also a dam that formed naturally by landslide due to high rainfall on 13 July 2012. A year after it was formed, on 25 July 2013 flooding occurred due to an extreme rainfall that caused the failure of the natural dam. The event of the failure on 2012 generated flood that severely damaged houses and various public facilities to negeri lima village down toward to the coast. As a result of this event, a small-scale reservoir is formed. The Government plans to utilize the established reservoir to build the new Way Ela Dam. This study was conducted to analyze floods with scenarios in the event of a failure in the new Way Ela Dam. The overland flow is simulate with two dimensional numerical model HEC-RAS v.5. Determining strategies for mitigation needs to be assessed comprehensively, by simulating disaster scenarios on the dam, analyzing the impacts and then planning recommendations for disaster risk. The results are expected to be a reference for mitigation plans for the new Way Ela Dam.

scholarly journals TURBULENT OSCILLATORY FLOW OVER RIPPLES AT HIGH REYNOLDS NUMBERS FOR PETA-SCALE SIMULATIONS

2018 ◽  
pp. 95
Author(s):  
Guillermo Oyarzun ◽  
Athanassios Dimas
Keyword(s):  
Coastal Zone ◽  
High Performance ◽  
Oscillatory Flow ◽  
Three Dimensional ◽  
Small Scale ◽  
Poisson Solver ◽  
Execution Model ◽  
High Reynolds ◽  
Wave Induced ◽  
The Impact

Surface waves in the coastal zone induce oscillatory flow motions in the vicinity of the seabed. These wave-induced coastal flows interact with the sandy seabed and modify the bed shape by generating coherent small-scale bed structures, which are generally known as ripples. The presence of ripples in oscillatory flows is important due to the impact they have on the seabed roughness and how they affect the near-bed boundary layer hydrodynamics. Simulations of higher and more real-scale Reynolds number (Re) require the use of supercomputers in order to obtain results in a reasonable amount of time. However, the constant evolution of the computing facilities makes the development of parallel algorithms a rather difficult task. The objective of the proposed research is to advance in the comprehension of coastal processes utilizing high performance computing (HPC) for the numerical simulation of the three-dimensional, turbulent flow, which is induced in the coastal zone by wave propagation. In particular, our CFD code (SimuCoast) has been developed using a hybrid MPI+OpenACC execution model that increases its scalability and allows it to engage the vast majority of high-end supercomputers. Special attention has been paid in the parallelization strategy of the Poisson solver that is the most computational demanding operation.

scholarly journals Imbalance Response and Damping Force Coefficients of a Rotor Supported on End Sealed Integral Squeeze Film Dampers

1999 ◽  
Author(s):  
Oscar C. De Santiago ◽  
Luis A. San Andrés
Keyword(s):  
High Performance ◽  
Effective Means ◽  
Squeeze Film ◽  
Damping Force ◽  
Damping Coefficients ◽  
Squeeze Film Dampers ◽  
Flow Through ◽  
Structural Isolation ◽  
The Impact ◽  
Severe Penalty

To this date, squeeze film dampers (SFDs) are effective means to reduce vibrations and provide structural isolation in high performance aeroengine systems. Integral squeeze film dampers (ISFDs) offer distinct advantages such as reduced overall weight, accuracy of positioning, and a split segment construction allowing easier assembly, inspection and retrofit. An experimental study is conducted to evaluate the effectiveness of integral dampers in attenuating the imbalance response of a massive test rotor. Damping coefficients for end sealed dampers are identified from the peak rotor responses due to imbalances while passing through the fundamental critical speeds. Impact response measurements at null rotor speed are also conducted to identify system damping coefficients for increasing values of the lubricant temperature. The impact tests and imbalance response measurements demonstrate that end gap seals increase effectively the ISFD viscous damping coefficients and without a severe penalty in the flow through the dampers. The experiments further demonstrate that the amplitudes of rotor synchronous response are proportional to the imbalance displacements without subsynchronous frequencies or (nonlinear) jump responses.

The Effect of Chevrons on Crackle: Engine and Scale Model Results

2011 ◽  
Author(s):  
Steve Martens ◽  
John T. Spyropoulos ◽  
Zac Nagel
Keyword(s):  
High Performance ◽  
Jet Noise ◽  
Scale Model ◽  
Small Scale ◽  
Mixing Enhancement ◽  
Noise Component ◽  
Acoustic Environment ◽  
Jet Mixing ◽  
Near Term ◽  
The Impact

GE and the USN continue to work together to find and develop practical techniques to reduce jet noise on tactical aircraft such as the F/A-18 E/F/G. Noise is an important issue for the Navy because of the harsh acoustic environment induced during operations of these aircraft on aircraft carriers and the impact to communities around Naval Air Bases and training sites. The noise generated by these systems is predominantly the noise generated by the exhaust plume due to the low bypass ratio of the engine and very high exhaust jet velocities. The main components of this jet noise are the jet mixing, shock and crackle noise. The present paper reports on progress, following Reference [1] with the F/A-18 E/F/G jet noise reduction program, which is currently focused on the USN near term goal of up to 3 dB reduction in the peak directivity direction. This goal also includes the reduction of the shock and crackle noise components. These goals are currently being pursued with nozzle plume mixing enhancement employing mechanical chevrons. These chevrons can be incorporated in the production version as a redesign of the F414 nozzle seals and do not involve the introduction of additional parts to the nozzle. This paper focuses on the effect of chevrons on the crackle noise component both in full scale on the F404 engine, and in small scale on the F414 engine nozzle in the twin configuration. The paper aims to make the case that this effect, which was first observed during ground engine testing of prototype chevrons, is a beneficial one in reducing/eliminating crackle which continues to be prevalent in high performance tactical aircraft engines today.

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