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Blowouts are a common type of wind-eroded landform found in sandy and desertified areas. They also represent a major degradative surface process affecting grassland ecosystems. Blowouts exacerbate changes in surface morphology through their effects on other surface phenomena including vegetation. In this paper, Xilingol League sandy grassland blowouts are taken as the research object, and the U.S. Keyhole satellite data and China's Gaofen-1 satellite data are used as the data source, and the blowouts are extracted based on the 3 S technology for a total of six periods of high-resolution remote sensing image data in the study area from 1962 to 2023. The Landscape Pattern Index method and Fuzzy Land Use Simulation (FLUS) modelling applied to changes over the last six decades provided spatial evolution parameters for predicting future blowout distributions. Results showed that blowouts affecting the Xilingol grassland area increased by 16.81% over the past 60 years. The patch density (PD) increased by 0.9 per hectare. The mean proximity index (PROX_MN) and mean Euclidean nearest neighbour distance (ENN_MN) showed a tendency to decrease and then increase indicating initial expansion and then merging of adjacent blowouts to create the present landscape. The FLUS model used ten factors to predict changes in blowout distributions from 2023 to 2033. Factors included digital elevation model (DEM), slope, aspect, normalized difference vegetation index (NDVI), mean annual temperature, mean annual precipitation, population density, real GDP, distance to water, and distance to impervious surfaces. It was found that grassland area decreased by 6217.12 hm2 and blowout area decreased by 102.91 hm2. Results of this study can expand understanding of blowout morphodynamics in ecologically sensitive areas. [ABSTRACT FROM AUTHOR]

Abstract Blowouts are a common type of wind-eroded landform found in sandy and desertified areas. They also represent a major degradative surface process affecting grassland ecosystems. Blowouts exacerbate changes in surface morphology through their effects on other surface phenomena including vegetation. In this paper, Xilingol League sandy grassland blowouts are taken as the research object, and the U.S. Keyhole satellite data and China’s Gaofen-1 satellite data are used as the data source, and the blowouts are extracted based on the 3 S technology for a total of six periods of high-resolution remote sensing image data in the study area from 1962 to 2023. The Landscape Pattern Index method and Fuzzy Land Use Simulation (FLUS) modelling applied to changes over the last six decades provided spatial evolution parameters for predicting future blowout distributions. Results showed that blowouts affecting the Xilingol grassland area increased by 16.81% over the past 60 years. The patch density (PD) increased by 0.9 per hectare. The mean proximity index (PROX_MN) and mean Euclidean nearest neighbour distance (ENN_MN) showed a tendency to decrease and then increase indicating initial expansion and then merging of adjacent blowouts to create the present landscape. The FLUS model used ten factors to predict changes in blowout distributions from 2023 to 2033. Factors included digital elevation model (DEM), slope, aspect, normalized difference vegetation index (NDVI), mean annual temperature, mean annual precipitation, population density, real GDP, distance to water, and distance to impervious surfaces. It was found that grassland area decreased by 6217.12 hm2 and blowout area decreased by 102.91 hm2. Results of this study can expand understanding of blowout morphodynamics in ecologically sensitive areas.

Maintaining pressure within the wellbore to avoid the uncontrolled flow of formation fluids is essential, and this process is known as well control. When there is an influx during drilling, different techniques are employed to maintain well control. The Driller's Method and Wait and Weight Method are common conventional methods used in the drilling industry due to their effectiveness and adaptability. One of the limitations of these two methods is when having a kick size exceeding the kick tolerance. In order to ensure the safety and integrity of a well in such conditions, it is imperative to explore alternative methods for managing large influxes of formation fluids that may occur during drilling operations. One promising approach involves implementing a reverse well control operation, which would enable the circulation of such influxes from the wellbore without compromising the integrity of the well. By reversing the flow of fluids from the wellbore and diverting them inside the strongest pipe from the beginning, the annulus pressures will be lower. This method can effectively manage and control huge influx sizes without exposing the annulus to high pressures. This paper does a detailed comparison between the Driller's Method and Reverse Driller's Method. [ABSTRACT FROM AUTHOR]

Accurately estimating the gas-flow rate at a wellhead to invert the formation pressure and production capacity information can be the basis for subsequent well-killing parameter design following oil and gas-well drilling blowout and ignition. Based on the multicomponent characteristics of the blowout gas and the turbulence intensity of the blowout flame, as well as the effects of complex factors such as environmental wind direction, wind speed, and wellhead structure, a numerical model for actual drilling blowout ignition is established. Jet-flame experiments are conducted under blowout conditions to verify the accuracy of the model. The temperature and radiation fields and flame morphologies of the well jet flow flame under different lateral wind speeds, well jet flow rates, and wellhead diameters are analyzed. Previous studies have found that as the lateral wind speed increases, the maximum temperature and maximum thermal radiation intensity of the blowout flame first decrease and then increase. However, as the amount of well jet increases, although the flame influence area increases, the maximum temperature does not increase significantly, and the maximum thermal radiation intensity actually decreases. Based on experimental and numerical simulation datasets, a high-yield gas-well jet volume prediction method based on the flame height and thermal radiation intensity of the well jet flow is constructed, which has important engineering application value for achieving successful well killing following well jet ignition. [ABSTRACT FROM AUTHOR]

Safety and risk assessment of the offshore geological storage of carbon dioxide (CO 2) in the Carbon Capture, Utilization, and Storage (CCUS) value chain needs the evaluation of the consequences of possible accidental submarine CO 2 leakages, including releases having high flow rate and very long duration, as blowouts. An innovative procedure for the estimation of the effects of submarine blowouts in shallow water was developed, based on the integration of specific sub-models. A model for blowout simulation is used to predict the features of the source term. The fate of the submarine plume is then assessed. Finally, the atmospheric dispersion of the surfacing gas is simulated, to estimate damage distances. The application of the methodology to a set of case studies evidences that in extremely shallow water the threshold distances of the gas cloud dispersing in the air can be higher for CO 2 than for natural gas. However, when considering higher water depths, the release of CO 2 to the atmosphere is strongly attenuated by the dissolution of CO 2 in the water column. [ABSTRACT FROM AUTHOR]

Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Most geotechnical stability research is linked to “active” failures, in which soil instability occurs due to soil self-weight and external surcharge applications. In contrast, research on passive failure is not common, as it is predominately caused by external loads that act against the soil self-weight. An earlier active trapdoor stability investigation using the Terzaghi's three stability factor approach was shown to be a feasible method for evaluating cohesive-frictional soil stability. Therefore, this technical note aims to expand “active” trapdoor research to assess drained circular trapdoor passive stability (blowout condition) in cohesive-frictional soil under axisymmetric conditions. Using numerical finite element limit analysis (FELA) simulations, soil cohesion, surcharge, and soil unit weight effects are considered using three stability factors (Fc, Fs, and Fγ), which are all associated with the cover-depth ratio and soil internal friction angle. Both upper-bound (UB) and lower-bound (LB) results are presented in design charts and tables, and the large dataset is further studied using an artificial neural network (ANN) as a predictive model to produce accurate design equations. The proposed passive trapdoor problem under axisymmetric conditions is significant when considering soil blowout stability owing to faulty underground storage tanks or pipelines with high internal pressures.

A recent study on active trapdoor stability has been completed by the authors using Terzaghi's three stability factors approach. It was concluded that the superposition approach is an effective way to evaluate the stability of cohesive-frictional soils. This technical note aims to extend the previous active trapdoor study to perform a stability assessment of a passive planar trapdoor (i.e., a blowout condition) in cohesive-frictional soil. Note that this passive trapdoor problem represents the blowout stability of soils due to defective pipelines under high water main pressures, in spite of the frequent media news about the water main bursts which enlightens the relevance of the problem. Numerical solutions of upper and lower bound finite element limit analyses are presented in form of the three stability factors (Fc, Fs, and Fγ), which consider the effect of cohesion, surcharge, and soil unit weight respectively. In the event of passive trapdoor stability, this technique can be used to determine a critical blowout pressure due to a water mains leak. The study continues with a series of sensitivity analyses with a widely selected range of parameters including the cover-depth ratio (H/B) and the drained frictional angle (φ). The influence of these parameters on the three stability factors is discussed, and a practical example of adapting these approaches is also introduced. All numerical results are provided in the forms of design charts and tables that can be efficiently used with confidence in design practice. [ABSTRACT FROM AUTHOR]

Blowouts are integral features of coastal dune fields. Their presence enhances both geomorphological and ecological diversity and enables the movement of sand by wind. Their role as a 'transport corridor' may be, however, considered negative from a coastal management perspective in heavily touristic areas, where the existence of blowouts close to the foredune can enhance the loss of sediment from the beach. This paper investigated the relationship between airflow dynamics and patterns of sediment transport from the beach to established dunes through a trough blowout located on the foredune. Seven three-cup anemometers were used to measure wind speed and direction over a 24 h sampling period at a frequency of 1 min under onshore (parallel to the blowout axis) medium and high wind speeds (max of 17.9 ms−1). To measure sediment transport, a total of 12 vertical sand traps were located at three positions along the length of the deflation basin. The results indicated that small amounts of sediments went into the blowout from the beach and that the highest rates of sediment remobilization took place within the deflation basin. These results highlight two processes: (a) flow channelization induced by the blowout topography caused an increase in wind speed and sediment transport toward the depositional lobe, and (b) the presence of embryo dunes and herbaceous vegetation at the beach–blowout boundary effectively reduced the amount of sediment transport from the beach to the landform. The results confirmed the significant role that vegetation plays in controlling sediment movement and conserving the beach–dune system. [ABSTRACT FROM AUTHOR]

A recent study on active trapdoor stability has been completed by the authors using Terzaghi's three stability factors approach. It was concluded that the superposition approach is an effective way to evaluate the stability of cohesive-frictional soils. This technical note aims to extend the previous active trapdoor study to perform a stability assessment of a passive planar trapdoor (i.e., a blowout condition) in cohesive-frictional soil. Note that this passive trapdoor problem represents the blowout stability of soils due to defective pipelines under high water main pressures, in spite of the frequent media news about the water main bursts which enlightens the relevance of the problem. Numerical solutions of upper and lower bound finite element limit analyses are presented in form of the three stability factors (Fc, Fs, and Fγ), which consider the effect of cohesion, surcharge, and soil unit weight respectively. In the event of passive trapdoor stability, this technique can be used to determine a critical blowout pressure due to a water mains leak. The study continues with a series of sensitivity analyses with a widely selected range of parameters including the cover-depth ratio (H/B) and the drained frictional angle (ϕ). The influence of these parameters on the three stability factors is discussed, and a practical example of adapting these approaches is also introduced. All numerical results are provided in the forms of design charts and tables that can be efficiently used with confidence in design practice.

The problem of road-related sinkhole stability has long been one of the main safety concerns to pavement engineers. Collapse and blowout failures are two typical types of pipeline-related sinkhole failures. Although much research on sinkhole stability analyses can be found in the literature, most of them assume a simple circular or rectangular shape of a cavity. In this study, the problem of sinkhole stability in an ellipsoidal cavity is investigated under both blowout and collapse conditions using advanced finite element limit analysis with adaptive meshing in an axisymmetric condition. A dimensionless pressure ratio is defined to represent sinkhole stability that is a function of many design parameters such as depth ratio, elliptical shape ratio, and soil strength ratio. Selected results are compared with published solutions, and comprehensive solutions of the parametric study are presented in the form of charts for use by design engineers. The present study contributes to the understanding of sinkhole stability under an ellipsoidal cavity, and it should be of interest to the road engineering community.

To date, scholars have side-stepped examining the applicability of the Anti-Blowout thesis in parallel sports. This essay is an attempt to test this construct in the context of endurance footraces. After a review of the central tenets of Dixon's definition of the Anti-Blowout thesis, I will provide a sketch of what blowouts look like in footraces including a description of a secured victory and the subsequent creation of a wide margin of victory. Conclusions suggest that opportunities do exist for runners to malevolently run others into the ground, although efforts to remedy such actions are challenging due to the structure of the footrace practice. [ABSTRACT FROM AUTHOR]

Purpose: The literature reports a varying occurrence (3–33%) of blowout of the rectal remnant after Hartmann's procedure, and there is a lack of multivariate analyses on potential risk factors for blowout following Hartmann's procedure. We aimed to estimate the incidence of blowout within 90 days after a primary Hartmann's procedure and to identify potential risk factors for blowout through multivariate analysis. Methods: A retrospective cohort study was conducted at the Department of Surgery, Aarhus University Hospital, a Danish primary and tertiary hospital. Patients who underwent primary surgery with Hartmann's procedure irrespective of surgical setting and indications between September 2016 and August 2021 were included. Blowout was defined as a defective closure line of the rectal stump or a pelvic abscess. Results: A total of 178 patients were included, and blowout occurred in 30 patients (16.9%) within 90 days after a primary Hartmann's procedure. Multivariate analysis showed increased risk of blowout among patients with Hinchey IV diverticulitis (relative risk 6.32 (95% CI 4.09–9.75)), previous radiotherapy (relative risk 3.35 (95% CI 1.67–6.74)), and alcohol overconsumption (relative risk 1.69 (95% CI 1.05–2.72)). Intraoperative insertion of a Foley catheter in the rectal remnant significantly reduced the risk of blowout within 90 days after a primary Hartmann's procedure (relative risk 0.18 (95% CI 0.05–0.65)). Conclusion: Blowout remains a severe and common complication within 90 days after a primary Hartmann's procedure. Hinchey IV diverticulitis, pelvic radiotherapy, and alcohol overconsumption are risk factors. An intraoperatively inserted rectal Foley catheter is a protective factor and can be considered used in all patients undergoing Hartmann's procedure. [ABSTRACT FROM AUTHOR]

Resonant pulse combustors, one of the deflagration-based pressure gain combustion devices, can significantly increase thermal efficiency in gas turbine engines. This experimental study investigates the stability characteristics of a newly designed actively valved resonant pulse combustor, capable of sustained operation and meaningful stagnation pressure gain. The resonant pulse combustor was fired with liquid gasoline fuel while ion and pressure sensors captured the temporally resolved heat release and chamber pressure. First, experimental results were used to demonstrate the general operating principle of the combustor. Then, the stability characteristics of the device were investigated through frequency domain analysis of the ion probe and pressure signal traces. A low frequency oscillation (also observed in steady flames and passively valved resonant pulse combustors), was observed as the device was brought near to its blowout limit. Finally, an index was defined to predict the stability characteristics of the resonant pulse combustor by quantifying the competition between low frequency oscillations and combustion-driven resonance. Experimental results demonstrated the ability of this index to provide early prediction of a blowout event for this device. [ABSTRACT FROM AUTHOR]

The stability of the tunnel face during tunneling is one of the major criteria for the design and construction of the tunnel. Collapse and blowout are two modes of tunnel face failure during the excavation. The cover-to-diameter ratio is one of the main parameters controlling these failure modes. Several analytical solutions have been proposed to estimate the range of support pressure applied on the tunnel face to avoid both the collapse and the blowout. However, most of those models deal with homogeneous soils. This paper aims at proposing an analytical model to predict the blowout of the tunneling face of a tunnel in multi-layered soils. The derivation is based on a limit equilibrium analysis, which considers the water tCiable. The proposed model is validated against the real blowout data reported from the tunneling in the Second Heinenoord Tunnel project in the Netherlands. Then, the maximum support pressure exerted on the tunneling face is predicted as a function of the cover-to-diameter ratio, the tunnel diameter, and the water table level for five representative soils. Finally, the model is applied to an underground segment of the Hanoi Metro Line 3 project (in Vietnam) to show the role of the multi-layer aspect. [ABSTRACT FROM AUTHOR]

In the Experimental Advanced Superconducting Tokamak (EAST), the water in the cooling channel of the divertor needs to be pushed out by the blowout system to avoid water leakage, otherwise it will further endanger the safe operation. However, diffusers often used to change the pipe size have an adverse effect on the water discharge in divertors. Therefore, research on the blowout process in the divertor and diffuser is essential to improving the dryness of the blowout system. In this paper, the mutual restriction between divertor and diffuser is proposed by the experiment research, such restriction is an important factor in reducing the dryness of the divertor. According to the experimental results, the larger the resistance loss is in the divertor, the smaller the effective pressure difference will be in the diffuser. Meanwhile, liquid phase water flows rotationally in the diffuser under a small pressure difference, thus reducing the dryness of the divertor. Moreover, the diffuser increases the pressure difference required for complete blowout in the divertor. These results will provide a reference for the design and optimization of the EAST blowout system in the future.

Copyright of Bányászati és Kohászati Lapok - Kohászat is the property of Hungarian Mining & Metallurgical Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Blowouts are integral features of coastal dune fields. Their presence enhances both geomorphological and ecological diversity and enables the movement of sand by wind. Their role as a ‘transport corridor’ may be, however, considered negative from a coastal management perspective in heavily touristic areas, where the existence of blowouts close to the foredune can enhance the loss of sediment from the beach. This paper investigated the relationship between airflow dynamics and patterns of sediment transport from the beach to established dunes through a trough blowout located on the foredune. Seven three-cup anemometers were used to measure wind speed and direction over a 24 h sampling period at a frequency of 1 min under onshore (parallel to the blowout axis) medium and high wind speeds (max of 17.9 ms−1). To measure sediment transport, a total of 12 vertical sand traps were located at three positions along the length of the deflation basin. The results indicated that small amounts of sediments went into the blowout from the beach and that the highest rates of sediment remobilization took place within the deflation basin. These results highlight two processes: (a) flow channelization induced by the blowout topography caused an increase in wind speed and sediment transport toward the depositional lobe, and (b) the presence of embryo dunes and herbaceous vegetation at the beach–blowout boundary effectively reduced the amount of sediment transport from the beach to the landform. The results confirmed the significant role that vegetation plays in controlling sediment movement and conserving the beach–dune system.

Natural and anthropogenic event information helped to simulate the physical--chemical behavior of hydrogen sulfide (H2S) in a deep oil spill and a hypothetical deep-ocean hydrothermal discharge. This research led to the development of the Lagrangian model of the discharge plumes in both cases and also analyzed the profiles of the H2S concentration at different depths taking into account its dissolution in ocean water and oceanographic conditions, such as thermohaline stratification, current fields, as well as the characteristics of the spilled hydrocarbon and the hydrothermal. The results revealed a first approximation in the identification of the dynamic behavior of the concentration profiles of H2S as a function of the oceanographic conditions. Hydrogen sulfide concentrations vary between natural and anthropogenic discharges at various depths, leading to a numerical model for applying in chemical oceanography. [ABSTRACT FROM AUTHOR]

The higher pollutant level in non-premixed combustion and safety issues pertaining to premixed combustion can be counteracted by partially-premixed mode of combustion. The partially premixed flames exhibit the benefits of both premixed and non-premixed flames. Partially premixed flames enhances complete combustion leading to reduced soot formation and hence lower emission. However, the equivalence ratio plays an important role in the stability of such flames. This paper reports the experimental investigation on the flame characteristics and stability of partially premixed LPG-air flames in tubular burner. The stability curve obtained for the base case without any secondary flow shows that the velocity at lift-off, drop-back, and blowout increases with increasing equivalence ratio. In the presence of secondary co-flow air, the lift-off and blow off velocity decreases compared to base case indicating poor stability due to extensive flame stretch leading to aerodynamic quenching. The experimental results show that the velocity of flow at lift-off, blowout, and drop-back are higher in the presence of secondary swirl air than the base case. Co-swirl air increases the stability due to better mixing at the flame base with increased residence time. Flame stability deteriorates with co-flow air as co-flow strains the flame boundary due to flame stretch. [ABSTRACT FROM AUTHOR]

The formation and evolution of coastal dunes result from a complex interplay of eco-morphodynamic processes. State-of-the-art models can simulate aeolian transports and morphological dune evolution under certain conditions. However, a model combining these processes for coastal engineering applications was not yet available. This study aims to develop a predictive tool for dune development to inform coastal management decisions and interventions. The aeolian sediment transport model AeoLiS is extended with functionalities that allow for simulations of coastal landforms. The added functionalities include the effect of topographic steering on wind shear, avalanching of steep slopes and vegetation processes in the form of growth and wind shear reduction. The model is validated by simulating four distinct coastal landforms; barchan-, parabolic-, embryo dunes and blowouts. Simulations, based on real-world conditions, replicate the landform formation, migration rates and seasonal variability. • Dune shaping processes are implemented into AeoLiS enabling landform simulations. • Four distinct landform types are simulated utilizing AeoLiS. • AeoLiS replicates accurate landform shapes and dynamics under real-world conditions. • Capabilities added to AeoLiS enable its use for a range of engineering applications. [ABSTRACT FROM AUTHOR]

To prevent climate change, Europe and the world must shift to low-carbon and renewable energies. Hydrogen, as an energy vector, provides viable solutions for replacing polluting and carbon-emitting fossil fuels. Gaseous hydrogen can be stored underground and coupled with existing natural gas pipe networks. Salt cavern storage is the best suited technology to meet the challenges of new energy systems. Hydrogen storage caverns are currently operated in the UK and Texas. A preliminary risk analysis dedicated to underground hydrogen salt caverns highlighted the importance of containment losses (leaks) and the formation of gas clouds following blowouts, whose ignition may generate dangerous phenomena such as jet fires, unconfined vapor cloud explosions (UVCEs), or flashfires. A blowout is not a frequent accident in gas storage caverns. A safety valve is often set at a 30 m depth below ground level; it is automatically triggered following a pressure drop at the wellhead. Nevertheless, a blowout remains to be one of the significant accidental scenarios likely to occur during hydrogen underground storage in salt caverns. In this paper, we present modelling the subterraneous and aerial parts of a blowout on an EZ53 salt cavern fully filled with hydrogen. [ABSTRACT FROM AUTHOR]

Uncontrolled inflow of formation fluid (brine) into a well adversely affects the cation–anion bonds in solutions and leads to their dissociation and loss of aggregative stability. Blow-out significantly complicates the drilling process and leads to an increase in non-productive time and in financial costs for problem solving. It is necessary to create a blocking screen that allows separation of the layer from the well and prevents brine flow. This article is devoted to the development of polymeric-blocking compositions that work due to the crystallization reaction of divalent salts of calcium and magnesium chlorides. More than 14 components were detected in the formation fluid on the atomic emission spectrometer. Based on the study of the compatibility of components with brine and the study of rheology and filtration processes through a real core under HPHT conditions, the optimal component polymer composition was selected. The reason for the increase in the rheology of composition during its thickening was established. With the help of tomographic studies, the depth of penetration of the filtrate into the core of layers was determined. For further studies, an experimental stand was designed for physical simulation of the isolation process under HPHT conditions and backpressure from the formation. [ABSTRACT FROM AUTHOR]

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sand desertification is a serious ecological and environmental problem in semiarid grassland areas; thus an accurate understanding of its causes and process mechanisms is of significance for grassland desertification control. With the popularization of remote sensing monitoring technology, most research has focused on analyzing the trends of grassland sand patches and their impact on regional desertification, whereas fewer studies have explored the mechanisms of grassland desertification development. This study analyzed the dynamic changes in grassland landscape in the Hulun Buir grassland of China via multiperiod high‐resolution remote sensing images from 1959 to 2020, and examined the morphological changes, erosion patterns, grain size characteristics and sediment compaction of two trough blowouts. Our study noted that under climate change and human activities, grassland desertification is becoming increasingly serious, and its main manifestation is the occurrence and expansion of blowouts. Changes in blowout morphologies indicate that the area of the deflation basin shows a state of continuous growth, whereas the area of the depositional lobe shows fluctuating changes, which could mean that the deflation basin may be a useful indicator of desertification. Based on a detailed analysis of both climate and grassland changes, we believe that human activities determine the occurrence of blowouts, and climatic conditions determine the expansion of blowouts and the desertification degree. The morphological changes of blowouts are related to the removal mode and erosion resistance of the grassland soil, and the rate of removal of the soil limits the rate of blowout expansion. [ABSTRACT FROM AUTHOR]

The appearance of a blowout can be an obvious sign of accelerated coastline retreat or dune erosion and in response to serious coastal erosion, an increasing number of artificial foredunes are being built. However, over time, numerous blowouts have also developed on artificial foredunes. To our knowledge, no studies have been reported on the evolution of blowouts in artificial foredunes, and in response we explore the aerodynamics and morphodynamics of artificial blowouts at different stages, by conducting field experiments on the Changjiang Ao coast of Pingtan Island, China. Where a foredune was built on an artificial clay structure, with topography and wind fields around three blowouts in different developmental stages measured, preliminary results revealed that: (1) the blowout morphology and airflow patterns show distinct seasonal changes; (2) the development of blowouts in artificial foredunes involves five stages, in contrast to the four stages observed in natural foredunes; and (3) blowout development is controlled by a two‐way feedback between aeolian processes and blowout morphological development, and the artificial structure can interfere with this feedback mechanism by altering the path of blowout development. The findings enhance our understanding of geomorphic process–response systems in artificial foredunes and provide a reference for coastal management and dune stabilization policy and practice. [ABSTRACT FROM AUTHOR]

The stability of the tunnel face during tunneling is one of the major criteria for the design and construction of the tunnel. Collapse and blowout are two modes of tunnel face failure during the excavation. The cover-to-diameter ratio is one of the main parameters controlling these failure modes. Several analytical solutions have been proposed to estimate the range of support pressure applied on the tunnel face to avoid both the collapse and the blowout. However, most of those models deal with homogeneous soils. This paper aims at proposing an analytical model to predict the blowout of the tunneling face of a tunnel in multi-layered soils. The derivation is based on a limit equilibrium analysis, which considers the water tCiable. The proposed model is validated against the real blowout data reported from the tunneling in the Second Heinenoord Tunnel project in the Netherlands. Then, the maximum support pressure exerted on the tunneling face is predicted as a function of the cover-to-diameter ratio, the tunnel diameter, and the water table level for five representative soils. Finally, the model is applied to an underground segment of the Hanoi Metro Line 3 project (in Vietnam) to show the role of the multi-layer aspect.

BackgroundThe purpose of this study was to examine outcomes, toxicity, and dosimetric characteristics of patients treated with reirradiation for head and neck cancers.MethodsFifty patients underwent ≥2 courses of radiation therapy (RT) postoperatively or definitively with or without chemotherapy. Composite dose volume histograms (DVHs) for selected anatomic structures were correlated with grade ≥3 late toxicity.ResultsMedian initial and retreatment radiation dose was 64 and 60 Gy, respectively. Median overall survival (OS), progression-free survival (PFS), and 1-year PFS rates were 18 months, 11 months, and 45%, respectively, with 13 months median follow-up. Thirty-four percent of patients experienced grade ≥3 late toxicity with 1 death from carotid blowout. The DVH corresponding to the carotid blowout fell above the third quartile compared with other patients.ConclusionOur analysis is the first to systematically evaluate the dose to the carotid artery using composite dosimetry in head and neck reirradiation patients, and demonstrates a promising technique for evaluating the dose to other normal tissue structures. © 2015 Wiley Periodicals, Inc. Head Neck 38: E961-E969, 2016.

Flame stabilization is highly important in lean premixed combustion which is considered a desirable technology for low-emission gas turbines. Swirl stabilization is one of the most common methods used for this purpose. Simple generation of swirl, however, is not enough to reach an acceptable operating range. A method of improving stability is using a bluff body in order to resist flame flashback caused by combustion-induced vortex breakdown at moderate to high swirl numbers. The present study aims to investigate the effect of bluff body size on the stability boundaries of flashback and blowout and also on flame shape. A premixed swirl burner is designed and built to operate with natural gas at atmospheric condition. In addition to gas and air flow rates at stability limits, normal and chemiluminescence flame images are documented. The non-reacting flow is also simulated to investigate the flow pattern out of the burner nozzle. It is found that bluff body size has a significant influence on flashback prevention and to a lesser extent on lean blowout limit while having minor effect on the shape of the flame. Just before blowout, low-frequency fluctuations are observed in the chemiluminescence radiations that are associated with the periodic changes in flame zone. Nonetheless, no warning signs are observed before flashback. Looking into the velocity profiles at the nozzle exit also shows an increase in axial velocity near the center of the nozzle with larger bluff bodies, revealing the mechanism of improvement of burner resistance to flame flashback. [ABSTRACT FROM AUTHOR]

Explosions and fires on offshore drilling units and process plants, which cause loss of life and environmental damage, have been studied extensively. However, research on drilling units increased only after the 2010 Deepwater Horizon accident in the Gulf of Mexico. A major reason for explosions and fires on a drilling unit is blowout, which is caused by a failure to control the high temperatures and pressures upstream of the offshore underwater well. The area susceptible to explosion and fire due to blowout is the drill floor, which supports the main drilling system. Structural instability and collapse of the drill floor can threaten the structural integrity of the entire unit. This study simulates the behavior of fire subsequent to blowout and assesses the thermal load. A heat transfer structure analysis of the drill floor was carried out using the assessed thermal load, and the risk was noted. In order to maintain the structural integrity of the drill floor, passive fire protection of certain areas was recommended.

To clarify the effect of the micro-vortex generator on the unsteady characteristics of jet combustion, a set of experiments had been carried out in a cavity-based supersonic combustor. Based on the advanced combustion diagnosis techniques, the ignition process, initial cavity-stabilized flame and dynamic flame development at the initial equivalence ratio of 0.20 are revealed in detail. Although the ignition processes are identical, the time for the flame propagation process in the cavity can be shortened when an MVG (micro-vortex generator) is located properly upstream of the injection. The initial flame cannot be stabilized in the combustor if the MVG is too close to the injection. After achieving initial stable combustion, the chemical reactions in the flame front are more vigorous and the shear layer can be lifted a little higher in the experiment with an MVG. At the same dynamic fuel adjustment method, the flame can be stabilized in the combustor without an MVG while the flame is blown out with an MVG. Based on numerous experimental results, it is found that the MVG dwindles the adjustment range of the dynamic injection, which makes against the stability of the flame when the engine decreases the thrust. [ABSTRACT FROM AUTHOR]

To prevent climate change, Europe and the world must shift to low-carbon and renewable energies. Hydrogen, as an energy vector, provides viable solutions for replacing polluting and carbon-emitting fossil fuels. Gaseous hydrogen can be stored underground and coupled with existing natural gas pipe networks. Salt cavern storage is the best suited technology to meet the challenges of new energy systems. Hydrogen storage caverns are currently operated in the UK and Texas. A preliminary risk analysis dedicated to underground hydrogen salt caverns highlighted the importance of containment losses (leaks) and the formation of gas clouds following blowouts, whose ignition may generate dangerous phenomena such as jet fires, unconfined vapor cloud explosions (UVCEs), or flashfires. A blowout is not a frequent accident in gas storage caverns. A safety valve is often set at a 30 m depth below ground level; it is automatically triggered following a pressure drop at the wellhead. Nevertheless, a blowout remains to be one of the significant accidental scenarios likely to occur during hydrogen underground storage in salt caverns. In this paper, we present modelling the subterraneous and aerial parts of a blowout on an EZ53 salt cavern fully filled with hydrogen.

Uncontrolled inflow of formation fluid (brine) into a well adversely affects the cation–anion bonds in solutions and leads to their dissociation and loss of aggregative stability. Blow-out significantly complicates the drilling process and leads to an increase in non-productive time and in financial costs for problem solving. It is necessary to create a blocking screen that allows separation of the layer from the well and prevents brine flow. This article is devoted to the development of polymeric-blocking compositions that work due to the crystallization reaction of divalent salts of calcium and magnesium chlorides. More than 14 components were detected in the formation fluid on the atomic emission spectrometer. Based on the study of the compatibility of components with brine and the study of rheology and filtration processes through a real core under HPHT conditions, the optimal component polymer composition was selected. The reason for the increase in the rheology of composition during its thickening was established. With the help of tomographic studies, the depth of penetration of the filtrate into the core of layers was determined. For further studies, an experimental stand was designed for physical simulation of the isolation process under HPHT conditions and backpressure from the formation.

The effect of differentiating the thermal conductivity between inner and outer walls on the stability of a U-bend catalytic heat-recirculating micro-combustor was investigated. To this end, a two-dimensional computational fluid dynamics (CFD) model was developed using the commercial code ANSYS Fluent (release 2020 R1) and, for different combinations of values for the inner and outer thermal conductivities, simulations of lean pre-mixed propane/air combustion were performed by varying the inlet gas velocity. Numerical results have shown that extinction is mainly ruled by the inner wall, whereas the outer wall controls blowout. Differentiating the thermal conductivity has been found to be an effective strategy to jointly exploit the better extinction resistance of low-conductive (i.e., insulating) materials, required by the inner wall, and better blowout resistance of highly conductive materials, required by the outer wall, thus enlarging the stable operating window of the catalytic micro-combustor compared to the use of the same material for both walls. [ABSTRACT FROM AUTHOR]

Deepwater drilling involves complex operations and equipment, so it is faced with various operational challenges including well control accidents. This paper proposes a dynamic risk assessment model for evaluating the safety of deepwater drilling operations. The dynamic risk assessment process includes three key steps: constructing fault tree models to analyze risk factors leading to a blowout accident, developing dynamic Bayesian network model based on the constructed fault trees, and performing dynamic risk analysis to evaluate the safety of well control operation. The proposed model includes risk factors about kick cause, kick detection, shut-in operation and kill operation, which covers the full process of a blowout. The proposed model could analyze the risk of blowout more comprehensively and the influencing degree of these four phases could also be clarified. Besides, the modular modelling method could update the structure and parameters of the developed model easily if new factors or data are added. The results show kick cause has the greatest impact on blowout accidents, followed by shut-in operation, kill operation and kick detection. Mutual information analysis and uncertainty analysis is performed to investigate the effects of risk factors on blowout. Finally, some corresponding preventive measures for blowouts are proposed. [ABSTRACT FROM AUTHOR]

Lateral femoral wall perforation is a rare intra-operative complication in anterior cruciate ligament (ACL) reconstruction surgery. However, it can be challenging to manage if it occurs. We share our experience on lateral femoral wall perforation managed by a large fragment washer. A 25-year-old man with right ACL injury presented with knee instability despite physiotherapy. Anterior drawer test (ADT) and Lachman test were grade 3, glide on pivot shift was positive. During ACL reconstruction, the lateral femoral wall was perforated. Due to unavailability of the rescue endobutton and budget constraint, we passed the endobutton through a washer and allowed it to sit on the washer over the lateral femoral wall. ADT and Lachman test on post-operative 6, 12 and 24 weeks were grade 1, with a negative pivot shift test. Lysholm knee score improved from 69 pre-operatively to 98 post-operatively. Conventionally, lateral femoral wall perforation can be managed by rescue endobutton, or screw and washer post technique. As this complication is rare, the rescue endobutton may not be available at all times, and the cost of the implant is also another important factor to consider. A washer can be used as an alternative technique to manage lateral femoral wall perforation in ACL reconstruction as it is not only costeffective but also provides stable fixation with good functional outcome.

Abstract Background and aims: One of the major concerns in the oil and gas drilling industry are Blowouts. Blowout could have severe consequences, such as fire and explosions, releases of toxic gases and environmental disasters. The aim of this study is to identify the root causes of kick and blowout in drilling industry. Methods: In this study, FTA investigates root causes of a kick while ETA explores the possible consequences (including blowout) arising from a kick. Bow Tie Analysis (BTA) combines FTA and ETA to explore the root causes and consequences (blowout) of a kick in onshore exploration Results: 28 basic event (root causes) have been identified for kick. Also to mitigate kick consequences, 8 safety barriers recognized. The probability of kick and blowout was calculated as 1/23× and 2/94×,respectively. The order of importance measure of each root causes was listed. Conclusions: In this study, Getting into the high pressure zone and not filling well with drilling mud during the trip up, was identified as the most important root causes of kick. Furthermore, early diagnosis of kick and the proper functioning of Blow-Out Preventer (BOP) were recognized as the first safety barrier to prevent the blowout.

The oil and gas industry is variably classified in upstream sector and downstream sector, with both sectors having exposure to a good number of hazards. The crude oil extraction process is one of the prime objectives of the upstream sector which includes the exploration of the crude, subsequent drilling operation and maximum recovery of the crude oil and gas from the site of operation. The uncontrolled flow of hydrocarbon in well may lead to blowout and will probably have environmental impact; thus, the extraction process can have a huge impact on the elements of earth, which include the soil (area of exploration and production), water and air. Approximately on global scale, there are forty-thousand crude oil sites and millions of people work or live in nearby vicinity; and workers associated with the job will be largely influenced in regard of their safety and health. On comparison of O & G extraction industry with the construction industry, the fatality rate goes up by 2.5 times (Goldberg and Moye in the first hundred years of the Bureau of Labor Statistics. US Department of Labor, 1985), as exposure to hazards like noise, radiation, H2S, crystalline silica is significant. In the article further, we review the safety hazards and health hazards associated with the extraction of the crude along with assessing the probable causes of the fatal incidents and exposure to hazardous substances. Workers involved in crude extraction process have potential impact on their health such as loss of immunity, cancerous cell development, liver and respiratory tract damage and neurological disorders. [ABSTRACT FROM AUTHOR]

In order to solve the complex production process, high technical content, bad working environment, frequent blowout accidents, and other problems. A method based on the concentration distribution characteristics of explosion flue gas emission in deepwater area is proposed. Based on the computational fluid dynamics theory, the basic governing equations of blowout and explosion of natural gas in deepwater are obtained. Based on the basic governing equations of deepwater natural gas blowout and explosion, the diffusion of natural gas in deepwater natural gas blowout and explosion is studied by using the K-turbulence model. The diffusion process of gas explosion in deepwater is obtained. Two Gaussian smoke model parameters, atmospheric diffusion parameter and average wind speed, were realized by combining the segmenting smoke flow with Gaussian smoke mass concentration distribution. The blowout and explosion process of natural gas in deepwater is simulated by MATLAB software, and the distribution characteristics of flue gas concentration are analyzed. The results showed that the smoke concentration and the change of smoke concentration were not affected by the change. [ABSTRACT FROM AUTHOR]

This study reports measurements of stability limits and exhaust NO mole fractions of technically-premixed swirl ammonia-air flames enriched with either methane or hydrogen. Experiments were conducted at different pressures from atmospheric to 5 bar, representative of commercial micro gas turbines. The full range of ammonia fractions in the fuel blend, x NH3 , was considered, from 0 (pure methane or hydrogen) to 1 (pure ammonia), covering very lean (φ = 0.25) to rich (φ = 1.60) equivalence ratios. Results show that increasing pressure widens the range of stable equivalence ratios for pure ammonia-air flames. Regardless of pressure, there is a critical ammonia fraction above which the range of stable equivalence ratios suddenly widens. This is because flashback does not occur anymore when the equivalence ratio is progressively increased towards stoichiometric and rich blowout occurs instead. This critical ammonia fraction increases with pressure and is larger for ammonia-hydrogen than for ammonia-methane. Provided that enough hydrogen is blended with ammonia (x NH3 < 0.9), flames with very lean equivalence ratios (φ < 0.7) can be stabilized and these yield competitively low NO emissions (<200 ppm), regardless of pressure. For this reason, very lean swirl ammonia-hydrogen-air flames are promising candidates for micro gas turbines. However, N 2 O emissions have the potential to be unacceptably large for these operating conditions if heat loss is too large or residence time is too short. As a consequence, the post flame region must be considered carefully. Due to the lower reactivity of methane compared to that of hydrogen, very lean swirl ammonia-methane-air flames could not be stabilized and good NO performance is limited to rich equivalence ratios for ammonia-methane fuel blends. The equivalence ratio above which good NO performance depends on pressure and bulk velocity. • Increasing pressure widens the range of stability of ammonia-air flames. • Increasing pressure increases the ammonia fuel fraction for which the transition from flashback to rich blowout occurs. • NO emissions from ammonia-hydrogen/methane-air flames decrease as pressure increases. • Good NO performance is found for very lean ammonia-hydrogen-air flames under elevated pressures. [ABSTRACT FROM AUTHOR]