Eccentric Position Research Articles

PERFORMANCE OF H. PLESNER’S PHILOSOPHICAL ANTHROPOLOGY: ECCENTRIC POSITIONALITY AND THEORY OF PERSONAL SOCIALIZATION

Helmut Plesner’s philosophical anthropology introduces not only the division of the world of the living being into self and environment, but also a superstructure over the zip distribution: eccentric positionality. This reflexive ability of the self to relate to itself allows the formation of personal-relative, i.e., social life. The aim of the article is: to trace the possibilities of methodological renewal of sociotheoretical discourse, which opens for him the principle of eccentric positionality.The study uses historical-comparative and logical-analytical methods. Research results. H. Plesner in the idea of eccentric positionality unfolds the perspective and possible practical consequences of the establishment of human openness in the world, not stopping at the danger of finally breaking the anthropological framework of his philosophy, dissolving it in the concept of personal socialization.Conclusion. Plesner’s «social» is presented as a life phenomenon – it is the highest manifestation of life, and the process of personalization of life manifestations is a process of socialization. Taking the self beyond oneself in eccentric positionality is something more than separating oneself from the environment, opposing oneself to it and establishing an attitude towards it. In the course of establishing the relation to oneself, the self does not form it automatically – the positioning of eccentricity cannot be carried out directly – which enables a special space favorable for the «inter-self» existence of living beings, a specific sphere of «inter-self» relations – the sphere of social existence.

Numerical Analysis of Heat Transfer Behaviours of Melting Process for Ice Thermal Storage Based on Various Heat Source Configurations

Ice thermal storage (ITS) performance for cooling systems is greatly influenced by the poor thermal conductivity of phase change material (PCM). The effect of natural convection on the melting process is significant for heat transfer enhancement. Thus, the melting performance of PCM in a shell-and-tube latent heat storage (STLHS) unit is numerically studied by considering natural convection in terms of various heat source positions and configurations, i.e., central position, eccentric position, and flat-tube type. Temperature distribution, melting time, and the overall heat transfer coefficient during the process are investigated. The results show that the circulation vortex formed by natural convection is a dominant factor that affects melting front evolution and the overall heat transfer coefficient. When input heat flux is relatively weak, PCM below the heat source is liquefied first. In contrast, PCM in the upper part melts earlier when the heat flux is excellent. The overall heat transfer coefficient decreases sharply with the increase in melting time in the early stage. Then, the heat transfer coefficient tends to be constant. PCM in an STLHS unit with a heat source in a lower position and a configuration of vertical flat-tube type has a desirable performance when compared with other cases, which could provide good support for ITS application.

Numerical Analysis of Two Way Slab With Openings

Slabs are the concrete elements used as significant components in building. It is common to have openings in slabs for various operational reasons like electrical, mechanical and plumbing services as a result decreases their capacity to carry loads. Along with this, insufficient data is available for slabs having openings at centre and at eccentric positions to resist applied loads. Moreover, many difficulties were faced analytically while modelling the complex behaviour of RCC slabs in nonlinear zone. Therefore, they require special attention in both analysis and design. This research gives more attention on studying structural behaviour of two-way slab having openings at centre and at eccentric positions along with solid slab. To study this type of behaviour seven different models of square slabs having different shapes of openings like square, rectangular and circular at centre and eccentrically has been generated in ANSYS, which is a FEM based software. All specimens were subjected to load, which was increased from zero to failure load. The effects of opening shape on crack formation were also analysed.

Величина шеечно-диафизарного угла ножки эндопротеза тазобедренного сустава как биомеханическая предпосылка развития асептической нестабильности вертлужного компонента (экспериментальное исследование)

Introduction Causes of aseptic loosening of THA components and improvement of the implants remain the subject of scientific discussions. The objective was to perform comparative analysis of the results of biomechanical modeling of cementless total hip arthroplasty using implants with different stem neck-shaft angles as a prerequisite of aseptic loosening of the acetabular component. Material and methods A biomechanical model of the pelvis and an implant with different stem neck-shaft angles was constructed based on computed tomography findings. Stresses and strains that the patient typically experienced under full weight-bearing on the operated lower limb were explored. Results The use of a stem neck-shaft angle of 125° provided the most favorable localization of the contact patch at the border of the acetabular component – the pelvic bone and lower values of equivalent stresses and contact pressure in comparison with more "valgus" femoral components (135° and 145°). Discussion The data obtained were fully consistent with the results of biomechanical studies by L. Quagliarella et al. (2006) who reported the substantial significance of the neck-shaft angle for on the parameters of contact pressure, since wear and debris-associated osteolysis decrease with a decreased neck-shaft angle. The use of stem neckshaft angles equal to 125° can be indicated for young patients with good bone quality and equal lower limb length. Unstable femoral cup can be caused by eccentric position of the contact spot at the border of the bone and the acetabular component and distribution of contact pressure and equivalent stresses inside the spot that are typical for artificial joints with stem neck-shaft angle of 145°. Conclusion The findings suggested that the value of stem neck-shaft angle was likely be considered a prerequisite for aseptic loosening of the acetabular component.

Three-dimensional evaluation of condylar position in skeletal Class I and Class II malocclusions along with vertical facial morphology

Objectives: This study aimed to three-dimensionally evaluate and compare anatomic condylar position to glenoid fossa in skeletal Classes I and II malocclusions along with vertical facial morphology (VFM). Material and Methods: Full skull 50 cone-beam computed tomographies (CBCTs) were taken with teeth in maximum intercuspation of patients aged 18–45 years who were grouped as skeletal Classes I and II, 25 each based on ANB angle and the patient’s right condyle was analyzed on CareStream-3D viewing software. The VFM was categorized based on the Jarabak ratio. Statistical analysis was performed using Mann–Whitney and Chi-square test. Results: In skeletal Class II when compared to Class I, the condyle in the glenoid fossa was anteriorly positioned with reduced anterior (P = 0.006) and increased posterior (P = 0.04) distance showing eccentric position. The condyle was also positioned lower suggesting an increased distance in the upper joint space (P = 0.04). The reduced height of the articular eminence indicated the condylar path and its position. The angle of articular eminence (P = 0.44) was decreased. Statistically, significant difference was not found between the various vertical facial morphologies. Conclusion: CBCT provides precise diagnostic values of joint spaces in skeletal Classes I and II to differentiate ideal condylar position from non-ideal according to different skeletal patterns, VFM, and also to notice minor discrepancies in joint spaces quantitatively. Depending on increased or decreased distances in the joint spaces, one can identify any temporomandibular joint-related discrepancies.

A CFD Validation Effect of YP/PV from Laboratory-Formulated SBMDIF for Productive Transport Load to the Surface

Several technical factors contribute to the flow of cuttings from the wellbore to the surface of the well, some of which are fundamentally due to the speed and inclination of the drill pipe at different positions (concentric and eccentric), the efficacy of the drilling mud considers plastic viscosity (PV) and yield point (YP), the weight of the cuttings, and the deviation of the well. Moreover, these overlaying cutting beds breed destruction in the drilling operation, some of which cause stuck pipes, reducing the rate of rotation and penetration. This current study, while it addresses the apropos of artificial intelligence (AI) with symmetry, employs a three-dimensional computational fluid dynamic (CFD) simulation model to validate an effective synthetic-based mud-drilling and to investigate the potency of the muds’ flow behaviours for transporting cuttings. Furthermore, the study examines the ratio effects of YP/PV to attain the safe transport of cuttings based on the turbulence of solid-particle suspension from the drilling fluid and the cuttings, and its velocity–pressure influence in a vertical well under a concentric and eccentric position of the drilling pipe. The resulting CFD analysis explains that the YP/PV of SBM and OBM, which generated the required capacity to suspend the cuttings to the surface, are symmetric to the experimental results and hence, the position of the drill pipe at the concentric position in vertical wells required a lower rotational speed. A computational study of the synthetic-based mud and its potency of not damaging the wellbore under an eccentric drill pipe position can be further examined.

Electrohydrodynamic enhancement of phase change material melting in cylindrical annuli under microgravity

Latent heat thermal energy storage has been recommended as an effective technology for the thermal management system of space exploration for its excellent ability to store thermal energy. However, the low thermal conductivity of phase change material seriously weakens the heat charging and discharging rates of the system. This paper introduces electrohydrodynamic, a popular active heat transfer enhancement technology, to enhance the phase change material melting in a shell-tube latent heat storage system under microgravity using the lattice Boltzmann method. Different from some previous works, this work mainly focuses on the combined effects of the electric Rayleigh number T and different gravity conditions on the melting performance. Results indicate that the electrohydrodynamic technique always shows good performance in accelerating the melting process, and especially, it is possible to save up to 90% of the charging time in some cases. In addition, the effect of eccentricity on the charging process is investigated, and it is found that although the concentric annulus is always the optimal configuration under no-gravity conditions, the optimal eccentric position of the internal tube largely depends on the electric Rayleigh number if one takes into account the gravity effects. Moreover, the effect of radius ratio Γ on the heat storage efficiency is also evaluated under no-gravity condition. The present work illustrates that electrohydrodynamic is an effective method for enhancing phase change material melting even under microgravity. • The combined effect of Coulomb force and gravity on PCM melting is studied. • The transient charging process of PCM melting under an electric field is presented. • A maximum of over 90% melting time saving can be observed under an electric field. • The optimal eccentric position relies on the gravity condition.

Buckling strength and post-ultimate behaviour of lipped channel section short columns under eccentric compression

The paper presents the results of a large experimental testing campaign and of a numerical parametric study on the influence of the load eccentricity on the buckling behaviour and the ultimate strength of thin-walled cold-formed steel columns with lipped channel cross-section subjected to eccentric compression around the major axis. The numerical study was carried out using the finite element method (code Ansys) and the finite strip method (code CUFSM). The selected numerical results were compared with the experimental test results. Some conclusions concerning sensitivity of buckling strength and redundancy of load-carrying capacity in the post-buckling (either elastic–plastic or plastic) range to the magnitude of eccentricity, depending on the eccentricity position according to major axis and column dimensions are derived.

Melting and solidification characteristics of a semi-rotational eccentric tube horizontal latent heat thermal energy storage

• Effect of eccentricity was investigated for the latent heat thermal energy storage. • Bottom eccentricity significantly improved the melting process. • Top eccentricity showed the potential to enhance the solidification process. • A novel semi-rotation of the storage system was proposed. • An optimum eccentricity was justified, and key parameters were investigated. Research showed that bottom eccentricity improved the melting performance in the horizontal shell-and-tube latent heat thermal energy storage (LHTES) system. However, it largely reduced the solidification performance. To solve this problem, this study investigated the effects of different eccentric positions of the inner heat transfer fluid (HTF) tube on the thermal performance of a horizontal shell-and-tube LHTES system during the melting and solidification processes. A novel technique with the intermittent rotation of the LHTES device was proposed to take the advantage of eccentric tube configurations for enhancing both the melting process during charging and the solidification process during discharging. Numerical simulations were conducted and validated in the FLUENT application of ANSYS software by utilizing the enthalpy-porosity method. Liquid fraction, average temperature, energy storage rate, and velocity distribution were used to evaluate the LHTES system thermal performance. Results showed that the bottom eccentricity significantly improved the melting process, however, it slowed down the solidification process. But the further study found that the top eccentricity could enhance the solidification process. Based on the average energy storage rate, the optimum bottom eccentricity laid between 0.60 and 0.75 for the charging process, which improved the melting rate by 64–74%. However, the optimal top eccentricity was between −0.15 and −0.30 for the discharging process. The proposed novel rotational technique well adapted the bottom eccentricity to improve the melting process during charging and the top eccentricity to enhance the solidification process during discharging. It was found that an optimal eccentricity of 0.30 could well tradeoff between the bottom eccentricity for charging and top eccentricity for discharging process in the proposed approach. Both the HTF cooling temperature and shell-to-tube radius ratio did not show a significant impact on the optimal eccentricity of the LHTES system.

Novel ureteral navigation with a fluorescent catheter during hemi-hysterectomy in cloacal exstrophy

We used a near-infrared ray catheter (NIRC) in a child with cloacal exstrophy presenting with hematometra and assessed whether the NIRC could help with complicated adhesiolysis during hemi-hysterectomy in children. A 6-French pig tail-type NIRC was inserted into the left ureter with guidance from a cystoscope. Laparoscopic hemi-hysterectomy with fluorescence observation was performed using the VISERA ELITE 2 system. NIRC insertion into the left ureter was not as difficult as expected despite the eccentric position of the left ureter orifice. When we found an enlarged left uterus and fallopian tube, adhesion was extremely severe around them due to chronic inflammation caused by hematometra. When near-infrared rays were applied, a fluorescent ureteral catheter that emitted bright green excitation light was observed on the dorsal side of the enlarged left uterus and fallopian tube. Under ureteral navigation with an NIRC, dissection of the adhesions was performed safely and smoothly. Hemi-hysterectomy and adnexectomy were performed successfully. The patient was doing well 2 years postoperatively without any complications. An NIRC can provide useful real-time visualization of the ureter course and reduce the risk of ureteral damage in children with advanced adhesions.

Effect of transcatheter edge-to-edge repair device position on diastolic hemodynamic parameters: An echocardiography-based simulation study.

BackgroundTranscatheter edge-to-edge repair (TEER) has developed from innovative technology to an established treatment strategy of mitral regurgitation (MR). The risk of iatrogenic mitral stenosis after TEER is, however, a critical factor in the conflict of interest between maximal reduction of MR and minimal impairment of left ventricular filling. We aim to investigate systematically the impact of device position on the post treatment hemodynamic outcome by involving the patient-specific segmentation of the diseased mitral valve.Materials and methodsTransesophageal echocardiographic image data of ten patients with severe MR (age: 57 ± 8 years, 20% female) were segmented and virtually treated with TEER at three positions by using a position based dynamics approach. Pre- and post-interventional patient geometries were preprocessed for computational fluid dynamics (CFD) and simulated at peak-diastole with patient-specific blood flow boundary conditions. Simulations were performed with boundary conditions mimicking rest and stress. The simulation results were compared with clinical data acquired for a cohort of 21 symptomatic MR patients (age: 79 ± 6 years, 43% female) treated with TEER.ResultsVirtual TEER reduces the mitral valve area (MVA) from 7.5 ± 1.6 to 2.6 ± 0.6 cm2. Central device positioning resulted in a 14% smaller MVA than eccentric device positions. Furthermore, residual MVA is better predictable for central than for eccentric device positions (R2 = 0.81 vs. R2 = 0.49). The MVA reduction led to significantly higher maximal diastolic velocities (pre: 0.9 ± 0.2 m/s, post: 2.0 ± 0.5 m/s) and pressure gradients (pre: 1.5 ± 0.6 mmHg, post: 16.3 ± 9 mmHg) in spite of a mean flow rate reduction by 23% due to reduced MR after the treatment. On average, velocities were 12% and pressure gradients were 25% higher with devices in central compared to lateral or medial positions.ConclusionVirtual TEER treatment combined with CFD is a promising tool for predicting individual morphometric and hemodynamic outcomes. Such a tool can potentially be used to support clinical decision making, procedure planning, and risk estimation to prevent post-procedural iatrogenic mitral stenosis.

Effects of fluid shear-thinning and yield stress on free convection in concentric and eccentric cylindrical annuli

Laminar free convection in yield-pseudoplastic fluids (the Herschel-Bulkley model) for concentric and eccentric cylindrical annuli has been studied numerically. The combined effects of shear-thinning viscosity and yield stress on the heat transfer characteristics have been examined for the following ranges of parameters: Rayleigh number, Ra (103 to 106), Oldroyd number, Od (0 to Odmax), power-law index, n (0.2–1), Prandtl number, Pr (10–100), eccentricity, ε (0–1.18) and angular position of the inner cylinder, ϕ (0° to 180°). The results are interpreted in terms of the yield surfaces, fraction of yielded fluid, streamlines, isotherms, local Nusselt number and average Nusselt number. Overall, the eccentric positioning of the heated cylinder along the vertical centreline fosters convective transport with reference to that for the case of the concentric annulus. It is possible to achieve augmentation of up to 30% in heat transfer for the case of ε = 1.18, ϕ = 0° with respect to the concentric case at Ra = 105, Pr = 10. This is ascribed to the greater fraction of the annular area occupied by the yielded fluid-like regions. Conversely, horizontal shifting of the inner cylinder to an off-centre position has an adverse effect on heat transfer. Limited transient simulations have also been run to identify the conditions for the loss of steady flow behaviour. A predictive correlation has been developed for the average Nusselt number for its estimation in new applications.

Erosion prediction of bypass crossover sub in eccentric operating positions in horizontal wells

Erosion wear is a serious problem in the fracturing process. The erosion of the bypass crossover sub, particularly in eccentric position, during fracturing in high flow rate and high proppant concentration can make a big difference in erosion results. CFD technology with Euler–Lagrangian approach is employed to solve the continuous phase and the discrete phase. In the fluid phase, realizable k−ϵ model was used to calculate the turbulent flows, and the Lagrangian method was applied to track the particle motion in the solid phase. In order to validate the accuracy of numerical simulation, scale model testing is used to obtain velocity of flow field in bypass crossover sub. The velocity profile is measured by a laser Doppler Anemonmetry (LDA). CFD simulation results are in a good agreement with experiment data. In this study, the particle trajectories and volume fraction in central and eccentric positions were obtained by simulation. This work aimed to conduct a detailed study on the flow phenomena of bypass crossover sub and analyze the difference in the bypass crossover sub between central and eccentric positions in terms of the magnitude of erosion rates and severe erosion locations and find out which erosion model is the most applicable to predict erosion. The numerical results show that the erosion contours predicted by the three erosion models have huge differences. Oka et al. erosion model is in a good agreement with practical observations by analyzing erosion patterns of the three erosion equations at specified locations and comparing them with actual image. The simulation of different flow rates and sand volume fraction were carried out. This research can help predict the erosion of bypass crossover sub more accurately and provide references for erosion prediction, as well as experiences for designing and improving the bypass crossover sub of horizontal wells in engineering.

Being grateful to Georg Simmel. Emotions, gratitude, and the relational concern of sociology in the globalized society

This paper argues for a sociological and relational concern of “gratitude” in Simmel’s thought as a key feature of human interaction as well as a key “emotive disposition” (Stimmung) to engage with the challenges of modern society. Georg Simmel is undoubtedly one of the most crucial theorists and a pillar in the social sciences, and his theoretical contribution also stands as the foundation of relational sociology stricto sensu. He taught that interactions supporting social processes must be investigated as forms of relations. A relation is a precise mode of being connected to others; it is a tie emerging from reciprocal action and acquires its consistency by generating causal effects on involved actors. Among his main insights within the sociological tradition, Simmel’s excellent concepts and arguments engage emotions as a sociological matter, that is, under a relational aspect. Not only do emotions have sociological relevance (that is, they are a worthy subject for sociologists), but they also characterize the precise manner of interaction among individuals. Emotions are the relational effect of being associated in an increasingly differentiated society, which apparently only neutralizes individuals’ emotive sides, or else instrumentally drives or “colonizes” them. Simmel explored gratitude as a particular emotion that is a form of relation and interaction: it has an eccentric position among the other emotions that he investigated in his many essays. Gratitude represents a non-symmetrical or economic (exchangeable) “transactive” emotion: it puts the giver and receiver in a peculiar socio-emotional form of reciprocity. By considering relations, emotions, and gratitude through rigorous textual exploration, this paper tackles Simmel’s view and challenges a globalized world and hybridized digital society. Finally, gratitude could be regarded as a demarcation criterion for identifying and distinguishing social interaction forms from other kinds of non-social processes or transactions.

Stochastic Physiological Gaze-Evoked Nystagmus With Slow Centripetal Drift During Fixational Eye Movements at Small Gaze Eccentricities.

Involuntary eye movement during gaze (GZ) fixation, referred to as fixational eye movement (FEM), consists of two types of components: a Brownian motion like component called drifts-tremor (DRT) and a ballistic component called microsaccade (MS) with a mean saccadic amplitude of about 0.3° and a mean inter-MS interval of about 0.5 s. During GZ fixation in healthy people in an eccentric position, typically with an eccentricity more than 30°, eyes exhibit oscillatory movements alternating between centripetal drift and centrifugal saccade with a mean saccadic amplitude of about 1° and a period in the range of 0.5–1.0 s, which has been known as the physiological gaze-evoked nystagmus (GEN). Here, we designed a simple experimental paradigm of GZ fixation on a target shifted horizontally from the front-facing position with fewer eccentricities. We found a clear tendency of centripetal DRT and centrifugal MS as in GEN, but with more stochasticity and with slower drift velocity compared to GEN, even during FEM at GZ positions with small eccentricities. Our results showed that the target shift-dependent balance between DRT and MS achieves the GZ bounded around each of the given targets. In other words, GZ relaxes slowly with the centripetal DRT toward the front-facing position during inter-MS intervals, as if there always exists a quasi-stable equilibrium posture in the front-facing position, and MS actions pull GZ intermittently back to the target position in the opposite direction to DRT.

When social change happens: observation of experience and the paradoxes of pivot-making

ABSTRACT This article is an attempt to draw attention on passages when social change happens, beginning with people’s efforts to observe demanding experiences in order to work through them. This work is made possible by “pivots,” i.e. resources found in culture (a story, a conversation, a memory, an image) that allow a person to gain an eccentric position for observing his/her experience – and regain the ability to make intentional choices within it. In the process, people add to the trail of “pivots” that can help others make new distinctions in their particular circumstances – and so contribute to social change.

Self-similar velocity and solid fraction profiles in silos with eccentrically located outlets

We examine the gravity-induced flow of dry and cohesionless granular media through an outlet placed eccentrically in a planar silo, employing computations based on a soft-sphere discrete element method. The vertical velocity profiles, measured at the outlet, are self-similar when the eccentric position of an outlet is given in terms of the smallest gap (s) between its corners and the lateral walls. On the other hand, the self-similarity of vertical velocity does not always hold for all eccentricities (e) given by the distance between the centers of an outlet and the silo base, which is a typical metric of eccentricity. For the former measure of the eccentric location, the flow conditions are observed to be similar for different outlet sizes. In contrast, we observe, the latter leads to differing flow patterns for the highest eccentricity wherein the largest outlet touches the sidewall and the rest are located at a distance. The effect of using s on the self-similarity of solid fraction profiles is observed to be minor in comparison to e. This study establishes the importance of s compared to e from the viewpoint of the self-similarity of the vertical velocity profiles at the outlet and generalizes the notion of the scaling of velocity and solid fraction reported by Janda et al. [“Flow rate of particles through apertures obtained from self-similar density and velocity profiles,” Phys. Rev. Lett. 108, 248001 (2012)] in a silo with a centric exit to the one with eccentric granular discharge. Finally, we propose expressions for the scaled vertical velocity and solid fraction in terms of s.

In-depth field survey of a rockslide detachment surface to recognise the occurrence of gravity-induced cracking

This work describes field evidence of gravity-induced cracking that has been identified on the failure scar of a small rockslide (volume = 6–7 m3) that occurred in March 2004 in the Rosandra Valley near the town of Trieste (north-eastern Italy). This shallow rock slope failure involved a limestone slope that was re-profiled through blasting about 135 years ago for the construction of an old railway, which has now been reconverted into a cycle path. Field observations ascertained that the slope failure was characterised by a cascading rupture process in which adjacent blocks collapsed in rapid sequence as a result of the progressive breakage of a number of rock bridges (domino-like collapse), thus highlighting a progressive failure mechanism. The rock bridges were localised in eccentric positions on lateral and rear release planes and failed in tension as a result of combined tensile and bending loading conditions (tensile strength of intact rock = 5 ± 2 MPa). The rockslide was triggered by cyclic loading related to freeze-thaw (ice jacking) that occurred over some consecutive days of daily snowmelt and nocturnal frost. The recognition of newly formed fractures also proves the current progressive development of 3D rupture surfaces of some unstable blocks susceptible to failure. This study provides innovative content to detect gravity-induced cracking in the field, which is an important precursory sign relating to the progressive failure of rock slopes. Gravity-induced cracks can be distinguished from pre-existing discontinuities for their more irregular profile (zigzag pattern), rougher surface, lower persistence and potentially different orientation. This study also provides some new insights into the step-path failure process of steep rock slopes. The mechanical process of initiation, growing and coalescence of gravity-induced fractures is strongly time- and stress-dependent. In the absence of external changing factors that profoundly modify the acting stress state (for instance, engineering countermeasures), progressive failure is a dynamic and irreversible process. For excavated slopes, the creation of a new rock face may abruptly provide the kinematic freedom of potentially unstable blocks, thus determining a very quick stress redistribution. If the mechanical system is not able to redistribute the stress on resisting stiff parts without overcoming the intact rock strength, gravity-induced cracking initiates and propagates until reaching slope collapse within times that are much shorter (from hours to 100–200 years) compared to natural rock slopes subjected to long-lasting geological processes (from 1000 to 2000 up to 10,000–20,000 years).

Study on shear fracture performance of subsea test tree under emergency conditions in the deepwater oil and gas completion testing

Subsea test tree (SSTT) is an essential safety device for the completion testing operations of deepwater extraction of oil, natural gas, and natural gas hydrate. During the implementation of the emergency release procedure of the SSTT, the coiled tubing or steel wire running in it must be quickly and effectively sheared by its ball valve mechanism. Therefore, clearly revealing the shearing mechanism and accurately evaluating the shearing performance of the ball valve mechanism is essential for maximizing the safety performance of SSTT operation. The finite element numerical simulation method established a dynamic shear model of the SSTT's ball valve under different working conditions and structural parameters to clarify the influencing factors and laws of the ball valve shearing performance. The results of numerical simulation model agree well with the laboratory tests, verifying the scientific validity and accuracy of the numerical simulation method and the generated model. Further, the SSTT's shearing process under different working conditions and geometry was calculated based on the method and model mentioned above. It shows that the tension of coiled tubing is greater, the required of shear moment is smaller. The internal pressure lead to more difficult shearing conditions. In the eccentric position, the ball valve was subjected to a reaction force moment perpendicular to the rotation direction of the ball valve. The larger the ball valve diameter, the shear force required to shear coiled tubing. The SSTT upper seat Angle also affects shear failure performance, and coiled tubing can be shear at 10°, 30°, and 40° with less shear moment. The minimum shear moment is required when the edge of the shearing ball valve has a 1.5 mm circular chamfering. This study proposes an optimization method to improve the shear fracture performance of ball valves. Moreover, this study provides essential guidelines for the optimal design and application operation on the SSTT's ball-valve mechanism.

Pressure transient response with random distributed fracture networks using a semi-analytical method for fractured horizontal wells in a rectangular closed reservoir

The focus of this paper is to establish a general model, which is capable of dynamic simulation of discrete fractures at any position and arbitrary distribution in rectangular closed reservoir. In this article, a semi-analytical model for fractured horizontal wells with random distributed fracture networks is proposed to facilitate pressure transient response using a double node method. A rectangular closed reservoir model and fracture network flow model are established respectively, and then coupled at the fracture wall. In order to deal with the flow distribution at the fracture intersection, a simple adaptive material balance method is proposed in this paper, which successfully solves the flow distribution at the intersection. Using advanced mathematical means, the model is successfully solved in Laplace space, and then the pressure response solution in real space is obtained by Stehfest numerical inversion method. The obtained solutions are verified and compared with the numerical simulation results. The calculation results show that the flow characteristics of the orthogonal fracture network can be roughly divided into six stages, namely, bi-linear flow, first linear flow, first radial flow, second linear flow, second radial flow and boundary dominated flow. However, these flow characteristics will deviate or even be missing, depending on the complexity of the fracture network. Finally, the effects of some important parameters (such as dimensionless fracture network conductivity, main fracture length, fracture network density, reservoir area and eccentric position) on pressure response and pressure field distribution are discussed in detail.