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Experimental Verification for Numerical Flow Analysis in Mixing Vessel
Get PDFVisualization of a streak line pattern in a mixing vessel is quite useful for understanding the mixing mechanism and designing an optimal mixing vessel. However, conventional experimental methods for visualizing streak lines require a lot of time to construct impellers and prepare solutions. Although various commercial fluid analysis software has been developed, there are still no examples of its use for calculating streak lines in mixing vessels. A simulation method was developed to quickly evaluate the streak line pattern in a laminar mixing vessel by numerical analysis with commercial code. A commercial CFD code can calculate streak line patterns in a laminar mixing vessel. It was found that a lattice method was more suitable than a particle method for the simulation of the streak line
The Optimal Reverberation for Masjids: A Subjective Assessment for Worshippers’ Demands
Get PDFThis study investigates the optimal reverberation time in masjids (mosques) from worshippers' viewpoint for the two modes of performance: recitation and sermon/speech. It also examines the effect of both age and gender on worshippers' preferences. To this end, specially convolved five audio clips (five acoustic setups) for each mode were created and uploaded to Google Drive. More than 300, Arabic-speaking participants, males, and females of different ages, listened to these clips. The participants judged the quality (Q, or appropriateness) of these audio clips for listening either to the recitation (QR) or speech (QS) on a unipolar discrete five-grade scale via a questionnaire that was created on Google Forms. Results indicated that both QR and QS are functions of gender and age. Overall, younger worshippers preferred higher reverberation and vice versa, while gender significantly affected the perception of the desirable reverberation for both recitation and speech. Females tended to the shorter reverberant environment (1.38 s for recitation mode, 0.75 s for speech mode, in the mid-frequency range) than males who preferred longer reverberation for recitation in particular (1.77 s)
Review of the Leak-off Tests with a Focus on Automation and Digitalization
Get PDFThe drilling and research communities are leading the way toward more digitally-controlled operations to ensure that the drilling process takes place as safely and gently as possible with the lowest possible carbon footprint. Today’s cutting-edge operations are run on large high-performance drilling installations where operations are largely run remotely from the driller’s operating station. Digitalization of the drilling process is the goal for performing drilling operations remotely from onshore. Leak-off test (LOT) or extended leak-off test (XLOT) plays a critical role in the petroleum industry. Therefore, recognizing all affecting parameters on LOT/XLOT and Formation integrity test (FIT) performance is vital. Because, in some cases, it is not possible to fully understand what happened during the test, having a deep insight into the LOT procedure is very important. One of the current study's main objectives is to thoroughly explain all stages of these tests and assemble all the significant parameters. Thus, many scientific papers on these tests were deeply reviewed and were classified into four main groups focusing on the application of LOT/XLOT (i) in stress estimation and geomechanical studies, (ii) concerning hydraulic fracturing, (iii) concerning wellbore stability, and (iv) numerical modeling, and then, the corresponding discussions were conducted. It was found that in-situ stress estimation is the most common application of the leak-off test.
Moreover, considering the importance of LOT and the desire to digitize operations in the oil and gas industry, it was found that the automatic LOT/XLOT is a fully required approach. The primary purpose of this study, which is hence considered its main contribution, is to prepare a LOT flowchart that would set off the further code development tasks of the field. The fundamental code of the present study was written and checked using a real dataset in a Python environment. The results were satisfying and indicated a successful start, which lays a foundation for future automated LOT/XLOT tests
Gas to Wire (GTW) Model in Brazil: Challenges and Possibilities
Get PDFThe expansion of natural gas production in Brazil presents some obstacles, the main one being the reduced volume of investments in expanding the transportation, distribution, and commercialization of natural gas produced offshore and onshore in the country. If, on the one hand, the lack of investments in infrastructure for the flow of natural gas produced in the country prevents the expansion of natural gas production in the onshore basins, the transformation of electric power near the reservoirs of natural gas has enabled the viability of projects for exploration and production of natural gas in the Brazilian onshore basins. A review of literature and analysis of secondary data allows the study of technical, legal, and economic factors that enable the implementation of a reservoir to wire projects, from the production of natural gas in the onshore basins of Brazil, aiming at the supply of electric power to the National Electric System. This way, natural gas changes its condition as a complementary energy source, together with the National Electricity System, to exercise the function of a basic energy source for parts of the national system
Performance of Management Interventions to the Impacts of Prosopis juliflora in Arid and Semiarid Regions of the Middle Awash Valley, Ethiopia
Get PDFThe objective of this paper is to provide up-to-date empirical information on the expansion of P. juliflora, its environmental and livelihood impacts, and the performance of past and current management strategies in the Middle Awash Valley (MAV), Ethiopia. This study was based on data collected using focus group discussion, key informant interviews, and field observation. The results show that P. juliflora has expanded rapidly and invaded valuable grazing and croplands, and settlement areas. The rapid expansion of P. juliflora in the study area is attributed to climate change (increased temperature and declined rainfall), its ecological competition, spreading of seeds by wild animals and pastoral (mobile livestock) livelihood system, and recent occurrences of flood and drought-induced pasture scarcity that has forced livestock to eat more P. juliflora seed pods. Also, delays in the use of land cleared for farming activity have created good opportunities for Prosopis expansion. The perception and views of people on the benefits of P. juliflora and management options vary according to livelihood systems and stakeholder types (e.g., environmental managers and pastoralists). The attempted management strategies to eradicate P. juliflora (cutting, burning, and bulldozering or converting into economic utilization by making charcoal, fodder, and furniture) failed to achieve the intended outcomes. These management interventions failed due to many reasons. Some of these were the rapid rate of P. juliflora expansion triggered by the recurrent drought, severe scarcity of pasture that forced livestock to eat P. juliflora’s seed pods and travel into new areas, inadequate technologies to aid utilization and eradication, inability to collect sufficient quantity of pods to produce fodder for livestock, and absence of sufficient and satisfactory markets for the end-product (fodder). The results generally imply the need for urgent policy and management interventions. This study also highlights important issues that should be considered in introducing and implementing management strategies in the future
Examining the effect of Debris Flow on Oil and Gas Pipelines Using Numerical Analysis
Get PDFThis article examines the impact of debris flow on semi-exposed pipelines to determine the plastic deformation and stresses by considering pipe-debris flow interaction. A 3-D finite element approach was adopted to study the mechanical behavior of pipelines subjected to debris flow. Integration of pipeline property (thickness) with debris flow intensity (impact pressure and angle) was also considered in a finite element numerical model for semi-exposed. The analysis showed that the impact angle between 35° and 75° with an impact pressure of 200 kPa and 250 kPa significantly affected the stability and integrity of the pipeline. There was a slight impact of wall thickness on the stability of the pipeline due to the passive soil resistance. Maximum plastic deformation of 124 mm was encountered in the case of 35° impact angle, which was 3% more than the deformation observed at 20° impact angle.
Moreover, large distribution of von mises stresses was observed, as 1390 Mpa, 1450 Mpa, 1440 Mpa, and 1440 Mpa for impact angles of 20°, 35°, 75°, and 90° in the impacted zone of the pipeline in each set of analysis. Shear failure of the pipeline was observed during the analysis as von misses’ stresses were more than the yield stress (520 Mpa) of the pipeline. The developed model in this study can be utilized for further research and will be a basis for designing pipelines crossing through mountainous regions
Interference Effects on the Square and Circular Cross-Sectional High-Rise Buildings Under Turbulent Flows
Get PDFEstimating the wind-induced responses of high-rise buildings requires a detailed investigation of wind force characteristics and structural dynamics, especially when an existing neighboring building has an equivalent volume at adjacent locations. The interference effects caused by such an adjacent building may seriously alternate the wind loading characteristics on the target building and further affect its responses to safety or habitability evaluation. This research investigates the interference effects on the wind-induced responses of high-rise buildings under turbulent boundary layer flows based on a series of wind tunnel tests. This study mainly concerns three disturbance factors to the interference effects: the approaching turbulent flows, the interference locations, and two typical section shapes of the concerned high-rise buildings. Results show that the terrain effect, the interference location effect, and the shape effect of both the principal and the interfering buildings significantly change the interference mechanism to the aerodynamic force and the estimated responses. The aerodynamic and the response interference factors defined in this study have shown distinct different patterns, indicating the interfered resonant response plays a vital role in dominating the interference mechanism. Finally, discretized maps with a satisfactory 0.5B × 0.5B grid resolution under statistical assumptions are proposed as examples for future codification works
Study on the Recommended Placement and Air Distribution of Split Floor-Standing Room Air Conditioners
Get PDFIn recent years, split floor-standing room air conditioners have been widely used in civil and office buildings because of their high cooling capacity and easy installation, and the air draft sensation has attracted more and more attention. In this study, a target air supply evaluation index for regional thermal comfort evaluation in the work area, the air velocity target value, is proposed. A computational fluid dynamics model for common office is established, and a total of 204 working conditions are numerically simulated for each combination of different positions, different rotation angles, and different air supply velocities (1 m/s, 2 m/s and 3 m/s) of air conditioners in the room. The influence of the rotation angle of the air conditioner on the indoor air distribution was studied, and the distribution of the indoor velocity flow field at different positions was analyzed. The air-conditioning rotation angle that makes the velocity target value of the five preset planes in the room smaller under different conditions is summarized as the recommended rotation angle. The numerical simulation results were verified by experimental means and found to be consistent with the measured results. This study can provide theoretical guidance and reference for the placement of indoor air conditioning units for users in real life
Fuzzy Best Dominants for Certain Fuzzy Differential Subordinations
Get PDFThis paper aims to present a survey on certain fuzzy subordination properties for analytic functions defined in the open unit disk. The new results are derived by considering a certain differential operator. By making use of two differential properties of the operator we determine sufficient conditions to find the fuzzy best dominants for several fuzzy differential subordinations. Some interesting further fuzzy consequences are also considered
Attention Mechanisms Evaluated on Stenosis Detection using X-ray Angiography Images
Get PDFCoronary stenosis results from unnatural narrowing of the heart arteries due to the accumulation of adipose depots, leading to different heart diseases and yielding top mortality worldwide. Thus far, deep learning-based methods for automatic stenosis over X-ray Coronary Angiography (XCA) have employed state-of-the-art architectures to solve the ImageNet challenge. With the advance of deep learning, contemporary architectures incorporated a variety of attention mechanisms to improve performance. Therefore, this paper presents a study of three attention mechanisms for stenosis detection in XCA images. Extensive experiments and comparisons over different Residual backbone networks are presented to verify the effectiveness of including such attention modules. An improvement of 4%, 10%, and 10% on the accuracy, recall, and F1-score was achieved using the approach, reaching mean values of 0.8787, 0.8610, and 0.8732, respectively