3D Flow Model Research Articles

Simulation of interactions between dam-break flows and complex downstream beds using Flow 3D model

Dam-break flow simulations are conducted all over the world, especially in the climate change phenomena taking place, complicated and impacting humans’ lives as well as the infrastructures. This paper introduces the interactions between dam-break flows and complex beds using the Flow-3D model. The analytical solution and the physical experiment are implemented to the dam-break flow over the simple and nonrough bed case to calibrate the numerical simulation. Two complex rough beds, which are the hump bed and the solid column bed, are selected to simulate the interactions between dam-break flows and these structures. With the hump bed, the Flow 3D model accurately simulates the flow characteristics over the rough bed and the flow height overtopping the hump. With the solid column bed, the flow velocities before and after a collision are simulated correctly when compared to the experimental data.

Abstract Number ‐ 23: In vitro evaluation of thrombectomy techniques: What is the most efficient combined technique?

Introduction A combined technique with contact aspiration and stent retriever is widely used for the treatment of patients with acute ischemic stroke due to the potential synergistic effect of the two technologies. However, there are no large studies that conclude the combined technique is more efficient compared to stent retriever only or contact aspiration. One of the issues in combined techniques may be the complexity, and multiple variations of combined techniques exist. We performed an in vitro study using three‐dimensional (3D) flow models and performed clot retrieval in order to explore effective and safe techniques for mechanical thrombectomy. Methods In a 3D silicone flow model with moderate tortuosity, we compared several techniques: 1. a pinching combination method (pull out stent retriever and aspiration catheter as a unit) with several variations of aspiration catheter locations; 2. an ingestion combination method (stent retriever removal through aspiration catheter); 3. stent retriever only; and 4. contact aspiration. We evaluated the success retrieval rates of a thrombus in the M2 branch. In addition, we measured pulling force during each technique to determine the amount of force exerted on the distal MCA vessel. Results The highest clot retrieval rate was achieved with a pinching combination technique with close contact with an aspiration catheter. The pulling force on the distal MCA vessel was high with the techniques that had high clot retrieval rates and low with the techniques that had low success rates. The pulling force was higher when the stent retriever was fully deployed compared with a pinching technique with a stent partially covered with an aspiration catheter. Conclusions In our in vitro model, the pinching combination method showed the highest clot retrieval rate when the aspiration catheter was advanced to the clot and the stent retriever. The pulling force experiments suggested the shorter stent retriever may decrease the rate of subarachnoid hemorrhage due to low pulling force.

Analysis of ozone generation in a planar atmospheric pressure air dielectric barrier discharge reactor

This work investigates O3 production in a planar atmospheric pressure air dielectric barrier discharge reactor numerically and experimentally. The surface temperature of the reactor is measured by an infrared (IR) thermal imager, and the O3 densities of cases in the reactive zone are measured by ultraviolet absorption spectroscopy. The 1.5D plasma fluid model (PFM) with transverse convection is employed to capture the average properties of a single microdischarge (MD) generated in the reactor. The concept of equivalent reaction is proposed to calculate spatial-cyclic average species sources obtained by the 1.5D PFM and provided to the chemical model of a 3D gas flow model (GFM) for obtaining density distributions of reactive species generated by MDs in the reactive zone. The simulated temperature distribution of the reactor surface is validated by that measured with the IR thermal imager since the gas temperature was reported as a critical discharge parameter for O3 generation. The simulated O3 densities show the same trend as the flow rate changes, which demonstrates the proposed model captures the average discharge dynamics in different operating conditions. In the 1.5D PFM, the simulated results show that the O3 molecules produced in the case of 4 SLM are much more than those produced in the case of 1 SLM though the O atoms produced in the case of 1 SLM are around 20% more than those produced in the case of 4 SLM. In the case of 1 SLM, more than 48% of O3 molecular generated are destructed, while only around 14% of O3 molecules are destructed in the case of 4 SLM. The analysis shows that around 73% of O atoms generated in the 1.5D PFM are consumed in the formation of O3 molecules in the case of 4 SLM, while only 18% of O atoms generated in the case of 1 SLM are consumed in the formation of O3 molecules. In the 3D GFM, the O3 destructed is around 24% of that destructed in the 1.5D PFM in the case of 4 SLM due to the oxidation reaction of NO, while only 11% of O3 molecules destructed as that destructed in the 1.5D PFM in the case of 1 SLM. The amounts of O3 molecules generated in the 3D GFM are minor if they are compared with those generated in the 1.5D PFM in all cases. The overall O3 yield efficiency reaches 97 g kWh−1 with the O3 concentration increasing up to 2700 ppm in the case of 4 SLM, while the O3 yield efficiency decreases to 10 g kWh−1 and O3 concentration drops to 1400 ppm in the case of 1 SLM.

Prediction and uncertainty quantification of shale well performance using multifidelity Monte Carlo

Uncertainty quantification is an integral component of reservoir management, especially considering the inherent uncertainty in subsurface systems. While a standard practice to estimate the uncertainty, Monte Carlo (MC) simulation is computationally intense when the sampling population comprises high-fidelity simulations. Alternatively, the Multi-fidelity Monte Carlo (MFMC) simulation overcomes this computational intensity by integrating low- and high-fidelity simulations. Our goal is to minimize the number of expensive high-fidelity simulations while maintaining accuracy and using numerous fast and cheap low-fidelity simulations to efficiently sample to input parameter space of interest. We selected gas production from unconventional wells to demonstrate the potential speedups and accuracy of the MFMC approach. The model fidelity usually determines the trade-off between accuracy and efficiency. While the high-fidelity model is more accurate, the low-fidelity model is more efficient. Our high-fidelity simulation includes reservoir simulations of a hydraulically fractured well. On the other hand, our low-fidelity model comprises the parallel-plate flow model. We used differential programming to efficiently solve the 1D flow model, where automatic differentiation is used to efficiently compute the gradients. We matched the production profile of high-fidelity simulations with our low-fidelity simulations. Then, we used a support vector regression to map the high- and low-fidelity input parameters. The mapping function is essential to tune the low-dimensional parameter space of the low-fidelity model to the high-dimensional parameter space of the high-fidelity model. We found that we can use a combination of 9 high fidelity and 10,000 low fidelity simulations to efficiently and accurately simulate pressure management. This method is at least two orders of magnitude faster than only using high-fidelity simulations. From a broader perspective, MFMC could efficiently estimate the uncertainty of various systems and models, integrating low- and high-fidelity models.

Влияние потенциального оледенения на безопасность подземного хранилища радиоактивных отходов на участке «Енисейский» (Красноярский край)

The paper evaluates the impact of potential glaciation on the migration of radionuclides from an underground radioactive waste repository to be sited at the Yeniseiskiy site. The problem was solved by mathematical modeling methods. The study considers a 3D model of groundwater flow and radionuclide migration taking into account the heterogeneous rock permeability. Groundwater dynamics equation was solved by the successive overrelaxation method, equation governing radionuclide migration was integrated by the alternating directions method using the Douglas’ scheme. The paper describes the influence of freeze-thaw cycles on rock permeability at the site taking into account available experimental data on samples collected from different rocks. Simulation showed that in the most unfavorable case glaciation could lead to a twofold increase of time-averaged velocity of radioactive plume propagation from the repository.

"THREE-DIMENSIONAL MODELLING OF RAILS / WHEELS MANUFACTURED BY ER6 AND ER7 IN TRAMWAY APPLICATIONS "

The wheels and rails of the train, tram etc. are often verified from their microstructure and plastic deformation, which usually appear in the outer layer of a wheel and rail, to analyse the causes of geometrical defects by monitoring the applied loads and variation of the temperature as suggested in the literature. This paper studies the effect of thermal stress applied with variations of the loads in contact on wheel/rail for the tramway, tracking through the state of the rail to discover the causes of geometric defects started by temperature variations and loads, and applying these variations of temperature and loads to know its resistance to these climatic conditions. 3D model of temperature distrubtion and heat flow in the wheel and the rail ER6 and ER7 has been developped using the finite element method based on the COMSOL Multiphisics.

A novel concept for estimating the contaminant mass discharge of chlorinated ethenes emanating from clay till sites

Interest in using contaminant mass discharge (CMD) for risk assessment of contaminated sites has increased over the years, as it accounts for the contaminant mass that is moving and posing a risk to water resources and receptors. The most common investigation of CMD involves a transect of multilevel wells; however, this is an expensive undertaking, and it is difficult to place it in the right position in a plume. Additionally, infrastructure at the site needs to be considered. To derive an initial CMD estimate at a contaminated site and to allow for the prioritization of further investigations and remedial actions, the ProfileFlux method has been developed. It is targeted at former industrial sites with a source zone in a low conductivity layer with primarily vertical flow overlying an aquifer with primarily horizontal groundwater flow. The ProfileFlux method was developed for mature chlorinated solvent plumes, typically originating from more than 30 to 50-year-old spills, as the usage of chlorinated solvents is mainly historical. Thus, it is assumed that the contaminant had time to distribute in the low conductivity layer by mainly diffusive processes. Today the contamination is continuously released to the underlying aquifer, where advection and dispersive (other than diffusive) processes are of higher importance. The approach combines high-resolution, depth-discrete vertical concentration profiles and a simple 2D flow and transport model to estimate CMD by comparing measured and simulated concentration profiles in the aquifer. The study presented herein includes a global sensitivity analysis, in order to identify crucial field parameters, and of particular importance in this regard are source length, groundwater flux and infiltration. The ProfileFlux method was tested at a well-examined industrial site primarily contaminated with trichloroethylene, thereby allowing a comparison between CMD from the ProfileFlux method and the traditional transect method. CMD was estimated at 117–170 g/year, when using the ProfileFlux method, against 143 g/year with the transect method, thus validating ProfileFlux method's ability to estimate CMD. In addition, applying the method identified weak points in the conceptual site model. The method will be incorporated into a user-friendly online tool directed at environmental consultants and decision-makers working on the risk assessment and prioritization of contaminated sites with the specific hydrogeological conditions of an aquifer with an overlying low permeability layer.

Patient-specific 0D–3D modeling of blood flow in newborns to predict risks of complications after surgery

Abnormal developments of the cardiovascular system are common congenital malformations. Computational fluid dynamics and mathematical modeling can be used to perform quantitative predictive assessments of hemodynamic properties in varied conditions. This article addresses the development of a coupled 0D–3D model of blood flow in newborns to predict risks of complications after surgery. The 0D-model of systemic circulations is created by using the analogy between the blood flow in vessels and the flow of current through an electric circuit. A shunted section of the aorta and pulmonary artery is replaced with a 3D-model with two-way fluid-solid interaction (FSI).A section in a vessel with the aortic valve is examined in a separate 3D-model. Three-dimensional geometry is based on real CT-scans of a patient. The algorithm for coupling models of different levels relies on meeting the condition that pressures and volumetric blood flows are equal at the interaction boundary. We have developed an algorithm for identifying personal parameters from the results obtained by solving an optimization problem. Computational experiments with different individual geometry of the aorta and aortic valve made it possible to analyze blood flow velocities, near-wall stresses, flows, and valve deformations. Observable near-wall stresses can be considered risk factors that could cause calcification on valve leaflets and other valve diseases. Computational solutions in the “aorta – shunt – pulmonary artery” 3D-system allowed obtaining spatial distributions of velocities, pressures, near-wall stresses and other parameters that are significant in respect to probable pathology development. The developed approaches are primarily relevant for decision-making in surgical practice to predict risks of postoperative complications. In future, our plans are to develop the model so that it covers also saturation and oxygen exchange. This is necessary for assessing whether oxygen supply to the lungs is adequate.

Персонализированное 0d–3d-моделирование течения крови у новорожденных для прогнозирования рисков осложнений после оперативного лечения

Abnormal developments of the cardiovascular system are common congenital malformations. Computational fluid dynamics and mathematical modeling can be used to perform quantitative predictive assessments of hemodynamic properties in varied conditions. This article addresses the development of a coupled 0D–3D model of blood flow in newborns to predict risks of complications after surgery. The 0D-model of systemic circulations is created by using the analogy between the blood flow in vessels and the flow of current through an electric circuit. A shunted section of the aorta and pulmonary artery is replaced with a 3D-model with two-way fluid-solid interaction (FSI).A section in a vessel with the aortic valve is examined in a separate 3D-model. Three-dimensional geometry is based on real CT-scans of a patient. The algorithm for coupling models of different levels relies on meeting the condition that pressures and volumetric blood flows are equal at the interaction boundary. We have developed an algorithm for identifying personal parameters from the results obtained by solving an optimization problem. Computational experiments with different individual geometry of the aorta and aortic valve made it possible to analyze blood flow velocities, near-wall stresses, flows, and valve deformations. Observable near-wall stresses can be considered risk factors that could cause calcification on valve leaflets and other valve diseases. Computational solutions in the “aorta – shunt – pulmonary artery” 3D-system allowed obtaining spatial distributions of velocities, pressures, near-wall stresses and other parameters that are significant in respect to probable pathology development. The developed approaches are primarily relevant for decision-making in surgical practice to predict risks of postoperative complications. In future, our plans are to develop the model so that it covers also saturation and oxygen exchange. This is necessary for assessing whether oxygen supply to the lungs is adequate.

Physical and numerical modeling of four different shapes of breakwaters to test the suspended sediment trapping capacity in the Mekong Delta

Extreme coastline erosion has become a major issue in Vietnam's Mekong Delta. Many coastal protection measures have been assessed based on their ability to dissipate incoming waves rather than their ability to facilitate environmental exchange and sedimentation processes. The goal of this study is to evaluate the ability of hollow and porous types of breakwaters to exchange suspended sediment on the deltaic coast. The experiments are set considering the hydrodynamic conditions of the Mekong Delta. We thought of four different types of breakwaters, including pile-rock porous breakwaters (CMD), two-sided perforated hollow breakwaters (TC1 & DRT/VTC), and curtain breakwaters (CWB45). Physical modeling in a wave flume was engaged to investigate the relationship between breakwater shape and sediment-capturing ability. All different breakwaters were placed on the wave flume with identical boundary conditions. Besides the physical modeling in the laboratory, Computational Fluid Dynamics (CFD) techniques using the FLOW3D model were applied. This provided an opportunity to understand the current distribution and the interactions between the fluid and the breakwater, as well as the ability to extract the vertical velocity profile and further additional insights from the interactions of waves and currents with the breakwaters. The wave parameters collected in the lab were further used to evaluate the numerical simulations in FLOW3D, and model validation demonstrated a good agreement with R2 = 0.74–0.98 and NSE = 0.74–0.96 for FLOW3D calibration and validation. It was found that fine sand and mud silt deposition on the shoreline of the breakwater alignment were significantly reduced in the case of the perforated hollow breakwaters. Therefore, using these hollow breakwaters for wave energy dissipation and sediment trapping presents a dual purpose in creating an environmentally friendly solution to recover mudflats. Hollow breakwaters also provide numerous advantages for supporting the creation of favorable conditions for the revival of mangrove forests, development of regional biodiversity, and overall improvement of coastal ecosystems on the deltaic coast.

Comparison of one-dimensional and three-dimensional glottal flow models in left-right asymmetric vocal fold conditions.

While the glottal flow is often simplified as one-dimensional (1D) in computational models of phonation to reduce computational costs, the 1D flow model has not been validated in left-right asymmetric vocal fold conditions, as often occur in both normal and pathological voice production. In this study, we performed three-dimensional (3D) and 1D flow simulations coupled to a two-mass model of adult male vocal folds and compared voice production at different degrees of left-right stiffness asymmetry. The flow and acoustic fields in 3D were obtained by solving the compressible Navier-Stokes equations using the volume penalization method with the moving vocal fold wall as an immersed boundary. Despite differences in the predicted flow pressure on vocal fold surface between the 1D and 3D flow models, the results showed reasonable agreement in vocal fold vibration patterns and selected voice outcome measures between the 1D and 3D models for the range of left-right asymmetric conditions investigated. This indicates that vocal fold properties play a larger role than the glottal flow in determining the overall pattern of vocal fold vibration and the produced voice, and the 1D flow simplification is sufficient in modeling phonation, at least for the simplified glottal geometry of this study.

Response of hydrogeological processes in a regional groundwater system to environmental changes: A modeling study of Yinchuan Basin, China

The sustainable development of groundwater resources in arid and semi-arid regions is a challenging task hindered by climate change and human activities. The rational utilization and management of groundwater resources is, therefore, dependent on an understanding of the influences of human and climatic factors on the spatial distribution of groundwater resources and their change over time. The thick Quaternary aquifers in the Yinchuan Basin, China were used herein as an example of how to quantitatively assess spatial and temporal trends in groundwater resources in response to human activities and climate change. A 3D transient groundwater flow model was constructed and used to simulate the evolution and spatial variability of hydrogeological processes from 1990 to 2020. By subsequently applying regime shift detection and correlation analysis to the simulation results, we found that: 1) groundwater storage was continuously depleted over the 30-year period, reaching a cumulative depletion of 1.89×109 m3; 2) human activities were mainly responsible for variations in regional hydrogeological processes for a period of up to 30 years. Climate only affected short-term interannual fluctuations in groundwater storage; 3) human activities (e.g., river water diversion and groundwater abstractions) were the decisive factors causing a continuous reduction of groundwater resources. A policy-driven reduction in water diversion from the Yellow River directly led to a significant drop in groundwater storage, which had a consequent effect on surface water and groundwater interactions and altered agricultural irrigation patterns (crop patterns and irrigation methods); 4) the amount of groundwater recharge from the Yellow River and local lakes increased from 1990 to 2020, whereas the discharge of groundwater to the Yellow River and lakes decreased.

Assessing local scour at rectangular bridge piers

The scour depth at bridge piers depends on a large number of variables. This study aims at revisiting the influence of rectangular piers' shape on local scouring. The scour around circular and rectangular bridge piers with length to width (L/D) of 1, 3, 4.5, 6, 7.5, and 9 was experimentally and numerically investigated at shallow water conditions (water depth to pier width (h/D) ratio varied from 1.4 to 2.32). Fifty-two experimental runs were carried out with a mobile bed made of non-ripples uniform sand with a median sediment grain size (d50) of 0.6 mm. The results show that L/D would influence the dimensionless scour depth (ys/D). The rectangular pier with L/D of 4.5 had the maximum ys/D and at L/D of 7.5 and 9 the ys/D was highly reduced. The Flow 3D model was used to verify the effect of downflow, shear stress, streamwise velocity and turbulence (energy and intensity) on the ys/D. The numerical results emphasized that the maximum scour would occur in terms of downflow and shear stress at L/D of 4.5. A new empirical equation (R2 = 0.904 and RMSE = 0.238) for predicting the maximum ys/D at rectangular piers was obtained. Compared with the similar formulas in the literature for predicting ys/D, accurate predictions at the rectangular pier with L/D of 1–9 were registered in this study.

Numerical modeling and parametric sensitivity analysis of heat transfer and two-phase oil and water flow characteristics in horizontal and inclined flowlines using OpenFOAM

Estimating the oil-water temperatures in flowlines is challenging especially in deepwater and ultra-deepwater offshore applications where issues of flow assurance and dramatic heat transfer are likely to occur due to the temperature difference between the fluids and the surroundings. Heat transfer analysis is very important for the prediction and prevention of deposits in oil and water flowlines, which could impede the flow and give rise to huge financial losses. Therefore, a 3D mathematical model of oil-water Newtonian flow under non-isothermal conditions is established to explore the complex mechanisms of the two-phase oil-water transportation and heat transfer in different flowline inclinations. In this work, a non-isothermal two-phase flow model is first modified and then implemented in the InterFoam solver by introducing the energy equation using OpenFOAM® code. The Low Reynolds Number (LRN) k-ε turbulence model is utilized to resolve the turbulence phenomena within the oil and water mixtures. The flow patterns and the local heat transfer coefficients (HTC) for two-phase oil-water flow at different flowlines inclinations (0°, +4°, +7°) are validated by the experimental literature results and the relative errors are also compared. Global sensitivity analysis is then conducted to determine the effect of the different parameters on the performance of the produced two-phase hydrocarbon systems for effective subsea fluid transportation. Thereafter, HTC and flow patterns for oil-water flows at downward inclinations of 4°, and 7° can be predicted by the models. The velocity distribution, pressure gradient, liquid holdup, and temperature variation at the flowline cross-sections are simulated and analyzed in detail. Consequently, the numerical model can be generally applied to compute the global properties of the fluid and other operating parameters that are beneficial in the management of two-phase oil-water transportation.

Thermal regime of the Grigoriev ice cap and the Sary-Tor glacier in the inner Tien Shan, Kyrgyzstan

Abstract. The thermal regime of glaciers and ice caps represents the internal distribution of ice temperatures. An accurate knowledge of the thermal regime of glaciers and ice caps is important to understand their dynamics and response to climate change and to model their evolution. Although the assumption is that most ice masses in the Tien Shan are polythermal, this has not been examined in appropriate detail so far. In this research, we investigate the thermal regime of the Grigoriev ice cap and the Sary-Tor glacier, both located in the inner Tien Shan in Kyrgyzstan, using a 3D higher-order thermomechanical ice flow model. Input data and boundary conditions are inferred from a surface energy mass balance model, a historical air temperature and precipitation series, ice thickness measurements and reconstructions, and digital elevation models. Calibration and validation of the englacial temperatures are performed using historical borehole measurements on the Grigoriev ice cap and radar measurements for the Sary-Tor glacier. The results of this study reveal a polythermal structure of the Sary-Tor glacier and a cold structure of the Grigoriev ice cap. The difference is related to the larger amount of snow (insulation) and refreezing meltwater (release of latent heat) for the Sary-Tor glacier, resulting in higher surface layer temperature, especially in the accumulation area, which is subsequently advected downstream. Further, ice velocities are much lower for the Grigoriev ice cap, with consequent lower horizontal advection rates. A detailed analysis concerning the influence of temperature and precipitation changes at the surface reveals that the thermal structure of both ice bodies is not constant over time, with recent climate change causing increasing ice temperatures in higher areas. The selected ice masses are representative examples of the (inner) Tien Shan glaciers and ice caps. Therefore, our findings and the calibrated parameters can be generalised, allowing improved understanding of the dynamics and future evolution of other glaciers and ice caps in the region.

Molten pool behavior and solidification characterization in steady magnetic field assisted laser-MIG hybrid welding of aluminum alloy

Microstructure evolution is highly correlated with the melt flow characterization in welding. In this study, a 3D heat flow model with consideration of magnetic field was constructed to describe the temperature field, the flow and keyhole behaviors in the molten pool during the laser-MIG hybrid welding. The role of magnetic flux density in the molten pool dynamics and microstructure evolution was explored. A moving hybrid heat source model including Gaussian surface heat source model and Gaussian rotary body heat source model as well as double ellipsoidal heat source model was carried out to elucidate the laser and MIG arc energy distribution. Decent agreement is realized between the measured weld geometry and predicted weld pool dimension. Numerical results indicate that an expanded molten pool is clearly observed under magnetic field. As the magnetic flux density increases, the downward flow velocity of the molten pool is enhanced. Moreover, visible difference of oscillation growth period for keyhole depth is produced and this leads to a variation in the time it takes for the molten pool to stabilize. Significant grain refinement appearing in both arc-affected zone at the weld upper part and laser-affected zone at the weld lower part is documented although the refinement degree varies at different zones. This is attributed to the formation of many initial nuclei or crystallites, originated from the enhanced flow of the molten pool with the assistance of magnetic field. This study provides a perspective in understanding the physical phenomena involved in magnetic field assisted laser-MIG hybrid welding and lays the foundation for weld microstructure optimization.

Influence of the free surface reconstruction on the spatial laser energy distribution in high power laser beam welding modeling

An accurate and efficient description of the spatial distribution of laser energy is a crucial factor for the modeling of laser material processing, e.g., laser welding, laser cutting, or laser-based additive manufacturing. In this study, a 3D heat transfer and fluid flow model coupled with the volume-of-fluid algorithm for free surface tracking is developed for the simulation of molten pool dynamics in high-power laser beam welding. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by a ray-tracing method. Two strategies of free surface reconstruction used in the ray-tracing method are investigated: a typical piecewise linear interface calculation (PLIC)-based method and a novel localized level-set method. The PLIC-based method is discrete, resulting in non-continuous free surface reconstruction. In the localized level-set method, a continuous free surface is reconstructed, and, thus, the exact reflection points can be determined. The calculated spatial laser energy distribution and the corresponding molten pool dynamics from the two methods are analyzed and compared. The obtained numerical results are evaluated with experimental measurements to assure the validity of the proposed model. It is found that distinct patterns of the beam multiple reflections are obtained with the different free surface reconstructions, which shows significant influence not only on the molten pool behaviors but also on the localized keyhole dynamics.

Investigation of the impact of the implementation of the coastal aquifer management plan on nitrate pollution in Gaza Strip Aquifer using modeling techniques

Groundwater is the principal source of public water supply and for satisfying the daily water needs. The Gaza strip coastal aquifer is suffering from salinity and contamination due to human activities especially agriculture activities. Although, the nitrate is necessary for agriculture activities it can affect the groundwater quality if leached nitrate from the soil into freshwaters after some time. The main objective of this research is to evaluate the current situation of the Gaza strip coastal aquifer and to predict the nitrate concentrations resulting from agriculture activities over the next twenty years using modelling approach. 3D Numerical groundwater flow modeling was developed to simulate the impacts of transport of nitrate loading from agricultural land on groundwater system using finite difference method GMS 10.4 software (MODFLOW 2005 code and MT3DMS package). Five management scenarios were considered to study the effect of pumping and recharge parameters on the groundwater flow system and the impacts of transport of nitrate loading from agricultural areas on the aquifer. Ten different wells were selected to investigate the impact of management scenarios on the nitrate concentration. All management scenarios indicated that there is a relationship between the water level and nitrate concentration in aquifer therefore the rates of nitrate concentration in the southern regions of Gaza strip is more than the northern regions.

Spatio-temporal variations of shallow seismic velocity changes in Salton Sea Geothermal Field, California in response to large regional earthquakes and long-term geothermal activities

We measure spatio-temporal variations of seismic velocity changes in Salton Sea Geothermal Field, California based on cross correlations of daily seismic traces recorded by a borehole seismic network from December 2007 to January 2014. We find clear co-seismic velocity reductions during the 2010 M 7.2 ​El Mayor–Cucapah, Mexico earthquake at ∼100 ​km further south, followed by long-term recoveries. The co-seismic reductions are larger with longer post-seismic recoveries in higher frequency bands, indicating that material damage and healing process mostly occurred in the shallow depth. In addition, the co-seismic velocity reductions are larger for ray paths outside the active fluid injection/extraction regions. The ray paths inside injection/extraction regions are associated with smaller co-seismic reductions, but subtle long-term velocity increases. We also build 3D transient water flow models based on monthly injection/extraction rates, and find correlations between several water flow parameters and co-seismic velocity reductions. We interpret the relative lack of co-seismic velocity changes within the geothermal region as unclogging of fracture network due to persistent fluid flows of geothermal production. The long-term velocity increase is likely associated with the ground water depletion and subsidence due to net production.

Thermal Impact by Open-Loop Geothermal Heat Pump Systems in Two Different Local Underground Conditions on the Alluvial Fan of the Nagara River, Gifu City, Central Japan

An alluvial fan is a good area to install open-loop geothermal heat pump (GHP) systems due to shallower aquifers, faster groundwater flow, and fewer land subsidence risks. The natural temperature change in groundwater occurs in alluvial fans due to the recharge of river water and faster groundwater flow, and the thermal impact of the open-loop system has not been studied well in such areas. The purpose of this research is to understand the thermal impact of open-loop GHP systems on an alluvial fan. A regional 3D model of groundwater flow with heat transport was created to determine the distribution of flow velocity and temperature of groundwater. After that, two local models with different groundwater velocities were constructed to demonstrate the thermal impact of an open-loop GHP system using one extraction and one injection well. The results indicated that the local model with faster groundwater flow had a smaller thermal impact. The natural temperature change in groundwater causes groundwater temperature to be lower in the summer and higher in winter during the operation in the local model, with faster groundwater flow.