Flow Lines Research Articles

Multidecadal Changes in the Flow Velocity and Mass Balance of the Hailuogou Glacier in Mount Gongga, Southeastern Tibetan Plateau

Maritime glaciers in the southeastern Tibetan Plateau (TP) have experienced important changes in mass and dynamics over the past decades, challenging the regional water supply and glacier-related hazards. However, knowledge about long-term variations in the surface velocity and mass balance of maritime glaciers remains incomplete due to the lack of representative observations in the southeastern TP. In this study, offset tracking is employed to measure spatiotemporal variation in the surface velocity of the Hailuogou Glacier (HLG) in Mount Gongga of the southeastern TP using Sentinel-1A imagery, while the time series of the HLG mass balance is reconstructed since 1950 by a physically based energy–mass balance model. Our satellite-based results find that HLG surface velocity shows significant spatial heterogeneity with a double-peak pattern along the flow line, and sustained slowdown below the icefall zone has been observed during the past nearly 40 years, although the icefall zone and the area above it have become relatively active. Our modeling indicates a persistent increase in mass loss over the last seven decades with an average rate of −0.58 m water equivalent (w.e.) year−1, which has accelerated in the past two decades. Sustained slowdown on the glacier is concomitant with pronounced negative mass balance, thereby enhancing glacier wastage in recent decades. The long-term trend in HLG mass loss is mainly driven by an increase in positive air temperature that decreases surface albedo and solid precipitation ratio and increases longwave incoming radiation, besides the influence of supraglacial debris cover. Large-scale atmospheric circulation patterns in the Eurasian region provide important implications for regional-to-local climate variability, unsustainably intensifying the trend of the negative mass balance of the HLG in the southeastern TP in the past two decades.

Simulation of Fountain Flow based on Molecular Dynamics Method

In this paper, numerical simulations of the fountain effect on the flow front of polymer dilute solutions are carried out based on molecular dynamics principles and the FENE dumbbell model. The Euler method is used to solve the constitutive equations of the mechanical model for the simple shear flow field and the dislocation equations of the dumbbell molecules, and subsequently obtain the tracer flow lines and the dumbbell distribution of the flow front. The results are used to calculate the stress field, analyze the rheological evolution law, study the effect of temperature and shear rate and other parameters on the model and analyze the effectiveness of the FENE dumbbell molecular model for the fountain effect. The study shows that due to the fountain effect the dumbbell molecules stretch more with increasing shear rate, the polymer stress at the flow front will show a complex change of stress overshoot and then stabilize, and the dumbbell molecules are oriented along the fountain flow line.

Experimental investigation and theoretical modeling on Bernoulli gripper using water for supply power enhancement

Bernoulli gripper is a fluid-driven vacuum suction device, widely used in automated production lines, with suction force regarded as its key mechanical indicator. Previous design methods for optimizing the structure and parameters showed very limited enhancement in suction force due to the compressibility of air, which limits the supply pressure and supply power. Therefore, this study proposes an innovative design for replacing the fluid medium from compressible gas to incompressible liquid (e.g., water). It was experimentally validated that the gripper using water can increase the supply power several times and the suction force dozens of times compared with that using air. Then, the pressure distribution and flow field of the gripper were investigated experimentally, implying that the flow field exists in the water-film zone and the bubble zone, with radial lines of water flow of equal cross section formed in the bubble zone. Furthermore, a model of pressure distribution was established, including the water-film zone, the bubble zone, and the boundary between the two. The theoretical results were basically consistent with the experimental results. This study provides an innovative idea, theoretical model, and experimental data for the optimal design and application of the Bernoulli gripper.

WITHDRAWN: Comparative Analysis of Asphaltene Deposition Methods : Stability indices, Stability plots, and Equation of state

Asphaltene deposition is one of the major problems that hinder hydrocarbon production. It can occur anywhere between the reservoir and the surface. Therefore, it is imperative that there be a procedure for minimizing the deposition of asphaltene in the production flow lines. There are several screening criteria that can be considered to determine the asphaltene deposition. This research will conduct a comprehensive study on different methodologies to determine the stability of asphaltene: the first category is the stability criteria using indices such as: the colloidal instability index (CII), the colloidal stability index (CSI), the stability index (SI), and the asphaltene stability predicting model (ANJIS). These four methods are used to predict the stability of asphaltene using SARA analysis. The fifth one is called modified CII which uses the compositions analysis of reservoir fluids, instead of SARA analysis, to determine the stability of asphaltene. The second method uses SARA Analysis to predict the stability via plots such as: Stankiewics plot (SP), De Boer plot, Sepulveda stability criterion (SCP). The third method is using compositional analysis of reservoir fluids and the equation of state model to predict the asphaltene onset pressure (AOP). In the last method Soave Redlich Kwong (SRK) equation of state model was used to predict asphaltene precipitations.In this work, a dataset of 166 was created which includes reservoir information, depth, compositional analysis, and SARA analysis. These data are used to study the potential of asphaltene deposition at the reservoir level. It was found that the stability criteria using indices and plots shows discrepancy in the results. The only two methods that show all the datasets are stable are the modified CII and the EOS model. As far as predicting asphaltene stability is concerned, the EOS method, based on compositional analysis and the thermodynamic model, appears to be the most reliable and trustworthy method. The other methods presented are observational rather than thermodynamic. Using these criteria is intended as a quick and fast estimate of the stability potential of asphaltene, not for planning or management of asphaltene deposition issues.

Fluctuaciones recientes del glaciar Alerce (1953-2020), Andes de Patagonia norte

In recent decades, glacier retreat has been observed in all the world’s mountain ranges. Over the last 20 years, glaciers in the Andes have lost mass at one of the highest rates on record. Particularly, glaciers in the northern Patagonian Andes show the highest rate of loss of all the Andean regions for the last decade. Detailed records of long-term variations in glacier extent are crucial to put current climate change into context and quantify its impact on mountain areas. In the present study, a reconstruction of the extension (length and area) of the Alerce glacier (41.15° S-71.81° W) for the last 70 years was carried out. By means of historical documents and satellite images (Landsat and Pléiades), detailed maps of glacier fluctuations were generated for the period 1953-2020. Four methodologies were evaluated to measure the front position: i) central flow line; ii) curvilinear box; iii) multiline; and iv) variable box. The magnitude of the front position variations depends on the methodology applied. The method that best addresses glacier front variations over the period analyzed is the variable box method. Between 1953 and 2020, the Alerce glacier lost 35% of its area (1.1±0.1 km2) and 67% of its total length (1.49±0.04 km). It is possible to distinguish periods with different rates of retreat. A stage of slight retreat (-11.3±0.5 ma-1) between 1953 and 1976, followed by a period of stability (-6.7±0.5 ma-1) between 1977 and 1983, then a strong retreat (-58.7±0.5 ma-1) between 1984 and 1999, followed by another period of stability (-5.4±0.5 ma-1) between 2000 and 2009 and, finally, another retreat (-8.7±0.5 ma-1) between 2010 and 2020. The retreat rates for the Alerce glacier mimic those observed in other glaciers in the region, possibly representing a regional climatic signal.

A Methodology for Rating Electricity Transmission Lines to Assess the Most Important or Critical Lines

The proposed method, based on three combined criteria—Sn—design capacity of the power line, LF, (line flow)—power flow in an electric transmission line, MVA, and the ratio of LF/Sn—allows for ranking electric transmission lines when calculations are performed in normal/pre-emergency modes. A combined set of criteria used to study critical/post-emergency N-k modes is developed. The simulations were performed on the real Baltic 330 kV electricity transmission system. The results reveal that when the power system operates in different load modes, most of the critical power lines determined by our method fall into the actual set of important/“critical” power transmission lines. This allows us to significantly reduce the number of simulated combinations and shorten the calculation time required for it. During the study of the Baltic electricity system, it was found that the developed method was accurate and efficient and suitable for the assessment of the reliability of real electricity transmission networks when planning operational and perspective work modes. The simulations results revealed the high reliability of the Baltic electricity system. The 330 kV electricity transmission network of the Baltic countries fully meets the N-2 criterion (usually, electricity transmission networks are designed to meet the N-1 criterion).

Design of Fast Real Time Controller for the SSSC Based on Takagi-Sugeno (TS) Adaptive Neuro-Fuzzy Control System

FACTS (Flexible AC Transmission Systems) technology is one aspect of the power electronics revolution that is taking place in all areas of electric energy. The power transfer capability of a transmission line can be enhanced by using power electronics based system like FACTS that offer high speed and reliable control capability. The Static Synchronous Series Compensator (SSSC) is the second generation of the FACTS controller, which is used to control the power flow in the transmission line. In this paper, a new scheme to control SSSC using adaptive neuro fuzzy logic is proposed, in this controller, Takagi-Sugeno fuzzy rules are trained using off-line neuro fuzzy system, also, instantaneous power theory is used to calculate the power system parameters due to its high accuracy and less computation. The simulation and practical results show that real time application of the proposed controller is possible and robust compared to conventional controllers previously investigated. The experiment results obtained using the dSPACE data acquisition system and Matlab real time toolbox.

Singularity attenuation with quantum‐mechanically revisited metric tensor

AbstractThe space and initial singularities are reexamined in the most reliable solutions to the Einstein's field equations (EFE), that is, the Einstein–Gilbert–Straus (EGS) metric. In discretized Finsler geometry, additional curvatures and thereby geometric structures likely emerge, which are distinct from the conventional spacetime curvatures and geometric structures that the Einstein's theory of general relativity introduced. The generalized fundamental tensor, which is obtained in the Fisleriean geometry, imposes quantum‐mechanically revisions on the Landau–Raychaudhuri evolution equations. The time‐like geodesic congruence in EGS metric is then analyzed, analytically and numerically. The evolution of a family of trajectories whose congruence is defined by the flow lines generated by velocity fields is determined. We conclude that both two types of singularities seem to be attenuated or even regulate. With the singularity attenuation, we refer to the fundamental nature of the additional curvatures at quantum relativistic scales.

Inkjet-printed transistors with coffee ring aligned carbon nanotubes

Low-concentration deposition techniques such as inkjet printing for forming carbon nanotube (CNT) transistor channels typically result in higher on–off current ratio, while lowering the field-effect mobility compared to traditional high-concentration techniques. In this paper, we show that inkjet-printed devices can have both high field-effect mobility and on–off current ratio by utilizing coffee ring induced thickness variation in the channel. The coffee ring effect occurs naturally in printed patterns with most solvents and substrates, and it pushes dissolved particles to the edges of printed features. Thickness variation and coffee ring effect are usually avoided in the channel of solution processed thin-film transistors by implementing additional expensive steps in the fabrication process. Instead, here, we control these variations and utilize them to create inkjet-printed CNT channels with printing induced thickness variation that improves transistor properties. Printing properties such as printing speed, and number of layers are studied to manipulate capillary flow and form thicker line edges, which ultimately enhance current transport in the CNT network. A two-pass printing pattern with separate lines improves the field-effect mobility five times compared to a pattern with connected lines that has no defined edges. The field-effect mobility increases from 1.1 to 5.7 cm2 V−1 s−1 at a drain voltage of −2 V.

Study on Flow Line Characteristics and Well Test Interpretation Methods of Multi Branch Fractured Wells in Dual Porous Media

Fractured reservoirs have developed fractures, strong heterogeneity, and complex seepage patterns. The analysis of core and imaging logging data in Bohai BZ Oilfield shows that there are a large number of fractures developed in the formation, with some wells having up to 6-8 fractures per meter. To study the impact of fractures on seepage, a multi fracture system seepage field simulation method was established, and the characteristic curves of flow lines under different fracture shapes were drawn. The fracture flow line morphology shows that there is a significant difference in the distribution of flow lines between the presence and absence of fractures, and the location of the fractures The size and shape of the reservoir have varying degrees of influence on the distribution of the streamline. The streamline around the well is distributed radially around it. When the fluid encounters an area with developed fractures, it first flows into the fractures and then flows from the fractures towards the wellbore. At the same time, based on the characteristics of fracture development in BZ oilfield and the theory of vertical fracture well testing, a dual medium multi fracture system oil well testing model was established. The model was numerically solved using Laplace transform, and a dual logarithmic curve chart for dual pore medium multi branch fracture well testing was obtained. The effects of fracture branching number, fracture length, conductivity coefficient ratio, and fracture conductivity on the shape of the testing curve were analyzed. The established well testing interpretation model can analyze oilfield stratigraphic information, reservoir fracture development, and boundary conditions. The research results have important guiding significance for evaluating the dynamic performance of oil wells in a dual pore medium multi fracture system and designing oilfield development plans.

Hierarchical Blocking Control for Mitigating Cascading Failures in Power Systems with Wind Power Integration

The increasing uncertainty of wind power brings greater challenges to the control for mitigation of cascading failures. In order to minimize the risk of cascading failures in large-scale wind power systems at a lower economic cost, a multi-stage blocking control model is proposed based on sensitivity analysis. Firstly, the propagation mechanism of cascading failures in power systems with wind power integration is analyzed, and the propagation path of such failures is predicted. Subsequently, sensitive lines that are prone to failure are identified using the power sensitivity matrix, taking into account the effects of blocking control on the propagation path. By constraining the power flow of these sensitive lines, a multi-stage blocking control model for the predicted cascading failure path is proposed with the objective of minimizing the control cost and cascading failure probability. Based on probabilistic optimal power flow calculations, the constraints related to wind power uncertainty are transformed into opportunity constraints. To validate the effectiveness of the proposed model, the IEEE 39-node system is used as an example, and the results show that the obtained control method is able to balance economy and safety. In addition, the control costs for the same initial failure are higher as the wind power penetration rates and confidence levels increase.

Innovative Industrial Solutions for Improving the Technical/Economic Competitiveness of Concentrated Solar Power

The modernization, efficiency, and decarbonization of the energy supply systems are among the new challenges to be faced in the coming decades to achieve the targets and objectives dictated by European strategic policies. Despite the countless benefits related to renewable energy sources (RES) integration, this brings key challenges to the power system, such as the risk of imbalance between energy generation and demand, sudden changes in flows in transmission lines with a need for expensive and time-consuming upgrades, and the withdrawal of conventional generation systems with consequent demands for new solutions and innovation to support grid services. A potential solution to limit the huge intermittence and fluctuation in power generation from RES is Concentrated Solar Power (CSP) technology integrated with thermal energy storage. The aim of this paper is to discuss the potential benefits related to the use of CSP technology by presenting innovative industrial solutions developed in the Italian SOLARGRID Project, namely the hybridization of CSP–PV systems and the solar thermo-electric system developed by MAGALDI, the parabolic trough collector of Eni, and the new linear Fresnel reflector configuration of IDEA S.r.l. These plant and component solutions are developed for improving the technical performance of CSP technology and reducing the levelized cost of electricity, thereby fostering an effective and massive deployment and encouraging the creation of new business models.

Analysis and Resolution of Flow Line Defects in Rare Earth Magnesium Alloys

Analysis and Resolution of Flow Line Defects in Rare Earth Magnesium Alloys

Experimental and numerical analysis of the Microstructure and mechanical properties of unidirectional glass fiber reinforced epoxy composites

This paper proposes a numerical model to predict the pattern and features of the fracture surface and to understand the mechanisms and cause of the failure. Various fiber orientations of 0°, 90°, 0°/90° and ± 45° were utilized in the production of unidirectional glass-fiber-reinforced epoxy composites via the vacuum bagging technique. The mechanical properties of the manufactured composites were evaluated by measuring parameters including tensile strength, compressive strength, flexural strength and interlaminar shear strength. High-resolution scanning electron microscopy was used to examine the mechanisms of fracture in laminates. The mechanical properties of the composite material were found to be considerably improved when a unidirectional 0° fiber orientation was used, as compared to other fiber orientations. This was true for tensile, compressive, flexural and interlaminar shear loading modes. The composite laminates demonstrated several modes of breaking, including fibers pulling away from the matrix, holes in the matrix and river flow lines, depending on the direction of the fibers. The outcomes of the numerical simulation demonstrate a high level of fidelity with experimental findings. This study provides a valuable reference for predicting numerical analysis of the microstructure and mechanical properties.

Effect of Semi-Transverse Ventilation Velocity on Combustion Characteristics of Pool Fire Sources in a Scaled Tunnel

Compared to longitudinal ventilation, there are few studies on fire source development under semi-transverse ventilation. This work studied the influence of semi-transverse ventilation on the combustion characteristics of fire sources in a scaled tunnel. The burning rate and heat transfer feedback during pool fire combustion were revealed under different longitudinal and transverse ventilation velocities. The results showed that transverse ventilation had little influence on combustion characteristics, and the burning rate was more obviously affected by longitudinal ventilation. The heat convection feedback increased monotonically with the increase of the longitudinal ventilation, which led to the increase of the total heat feedback on the fuel. The heat radiation feedback changed little, and the heat conduction feedback decreased monotonically with the increase of the longitudinal ventilation velocity. By aid of a Fire Dynamics Simulator, it was found that the flame tilted downstream and was in the flow line of the lower cold air flow coming from upstream and the upper hot smoke flow outgoing in the downstream direction. The transverse ventilation of 2 m/s or lower hardly affected the combustion field of the fire source. Therefore, semi-transverse ventilation is preferable to longitudinal ventilation from the point of view of limiting fire expansion.

APPLICATION OF NUMERICAL MODELING TO PIPE LEAKS IN FLUID FLOW

Pipes are a medium used to move flowing fluids and are very dependent on pressure and speed. Leaks in pipes can cause physical loss of water. This can be caused by many things, one of which is a leak caused by a hole in the pipe which can disrupt the flow of water so that the flow of water or fluid will change, including the pressure and speed. A fluid flow can be visualized using simulation or mathematical modeling using finite differences. By using the GNU Octave application, namely numerical computing which can be accessed for free without a license which is used as data visualization, it can provide an overview of fluid flow including the occurrence of leaks in pipes, namely by visually representing the state of fluid flow when a leak occurs in a pipe. With this visualization, a fluid flow pattern is produced where leaks occur at several different points. From the research results, it was found that the pipe before it got a leak would be laminar, but when it got a leak, the fluid flow would become a fluid flow that switched to transitional fluid flow or turbulence. Apart from that, the placement of coordinate variations slightly affects the fluid flow line

Integrated sand management: modeling of sand erosion in a mature oil field in Malaysia

Sand production can lead to various problems, including erosion in production flow lines that may lead to total production loss for extended periods and costly workover operations. The extent of erosive damage is determined by many factors, among which the flow and sand rates are the most significant. Three main issues must be addressed to ensure an efficient production operation: Sand erosion estimation, Sand monitoring (settling and deposition), and maintaining optimum production rates. If sand production exceeds certain levels, i.e., allowable sand rate, the erosion in the production network becomes problematic. Sand production has been problematic in some wells in Reservoir X. Core, and historical production data was used to build a comprehensive model using Schlumberger PIPESIM™ hydraulic modelling. The software allows for detailed modelling of the production network by which erosion rate, erosion hotspots, and deposition of the produced sand can be quantitatively analyzed. Considering an allowable erosion rate of 0.3 mm/year, the model outcomes indicate that sand erosion is critical in wells J-1, J-2, and L-2. The next step was identifying the hotspots where the produced sand is deposited in the abovementioned wells. The modelling results indicated that sand deposition is primarily severe in the teeline between the platforms. Moreover, the gas-oil ratio was identified as the most influential factor in the sand deposition. Lastly, a sensitivity analysis was conducted on the allowable flow rates and maximum (technical) allowable sand production and erosion rates to find optimum production rates from reservoir X.

Systematizing Complaints About Healthcare and Services at University Hospitals: Content Analysis of Patient/Family Letters.

Patient/family complaints are a valuable source of information for providing patient-oriented healthcare. This study aimed to identify and systematize patient/family complaints about healthcare services, focusing on complaints caused by "things." A qualitative descriptive study was designed. Open data of patient and family voices published on the website of university hospital were collected from 27 hospitals for the period June 2020 to August 2020. From the collected data, we excluded praise and compliments, and complaints regarding "people." The results revealed 1,476 complaints, with 1,755 codes. Patient/family complaints were categorized into five domains (access to hospital or line of flow in the hospital, outpatient, inpatient, facilities/equipment, publicity/documents), 46 categories, and 150 sub-categories. A total of 545 codes were excluded to avoid duplication: [1] 253 related to hardware, [2] 222 related to operations, and [3] 70 related to maintenance. This study may provide useful data to inform future studies using patient/family complaints to improve healthcare services for hospitals aiming to provide patient-centered care.

Improving the uniformity of the inkjet-printed polymer film in a bank by Marangoni flow and contact line sliding

Printed polymer films with higher film uniformity and device-performance were obtained by regulating the Marangoni flow and contact line sliding with co-solvents of different surface tension.

Admissible Control Laws for Constrained Linear Power Flow: The General Case

Linearized power flow with line flow and voltage constraints can be modeled as a system of linear inequalities depending on the power injections. When some injections are controlled by the grid operator while others are determined exogenously, robust control aims at determining grid operator's actions under imperfect system observability such that the grid state is feasible for all possible realizations of the exogenous actions. It was shown how to design and analyze such admissible control policies efficiently for the subclass of affine control laws, but this paper shows that there are important cases that require more general control policies. We show that, for the constrained linear power flow setting, general admissible control policies can always be chosen as piecewise affine (PWA) mappings. The PWA mapping can be explicitly characterized offline or control actions can be computed online by solving an optimization problem given a current observation. For the latter setup, we provide an algorithm that verifies offline that the online control scheme is admissible. This verification step is a crucial precondition to apply the online control scheme in real, safety-critical power grids. The proposed framework is demonstrated with applications to voltage regulation in active distribution grids subject to uncertain prosumers and low observability.