Variable Internal Pressure Research Articles

An improved correction of radial velocity systematics for the SOPHIE spectrograph

High-precision spectrographs can on occasion exhibit temporal variations in their reference velocity or nightly zero point (NZP). One way to monitor the NZP is to measure bright stars, whose intrinsic radial velocity variation is assumed to be much smaller than the instrument precision. The variations of these bright stars, which is primarily assumed to be instrumental, are then smoothed into a reference radial velocity time series (master constant) that is subtracted from the observed targets. While this method is effective in most cases, it does not fully propagate the uncertainty arising from NZP variations. We present a new method for correcting for NZP variations in radial velocity time series. This method uses Gaussian processes based on ancillary information to model these systematic effects. Moreover, it enables us to propagate the uncertainties of this correction into the overall error budget. Another advantage of this approach is that it relies on ancillary data that are collected simultaneously with the spectra and does not solely depend on dedicated observations of constant stars. We applied this method to the SOPHIE spectrograph at the Haute-Provence Observatory using a few instrument housekeeping data, such as the internal pressure and temperature variations. Our results demonstrate that this method effectively models the red noise of constant stars, even with a limited number of housekeeping data, while preserving the signals of exoplanets. Using simulations with mock planets and real data, we found that this method significantly improves the false-alarm probability of detections. It improves the probability by several orders of magnitude. Additionally, by simulating numerous planetary signals, we were able to detect up to 10% more planets with small-amplitude radial velocity signals. We used this new correction to reanalyse the planetary system around HD158259 and to improve the detection of the outermost planets. We propose this technique as a complementary approach to the classical master-constant correction of the instrumental red noise. We also suggest to decrease the observing cadence of the constant stars to optimise the telescope time for scientific targets.

Numerical Analysis of Functionally Graded Material (FGM) Axisymmetric Cylinder under Transient Thermal Load and Variable Internal Pressure

Numerical Analysis of Functionally Graded Material (FGM) Axisymmetric Cylinder under Transient Thermal Load and Variable Internal Pressure

Post-buckling behavior of variable-arc-length elastica pipe conveying fluid including effects of self-weight and pressure variation

This paper investigated the post-buckling behaviors of a variable-arc-length (VAL) elastica pipe caused by internal transporting fluid motion, accounting for the effects of the self-weight and variation of internal fluid pressure. Both weak-form and strong-form formulations of the VAL elastica pipe were developed. The weak-form formulation was derived by the virtual work principle, and later solved using the nonlinear finite element method (FEM). The strong-form formulation was derived using equilibrium of the force and moment equations, the geometrical relationship of the differential pipe segment, and the energy conservation of the transported fluid. Because of the large displacement analysis, the variation in the internal pressure inside the pipe was considered, which was taken into account by energy conservation based on the Bernoulli principle. Then, the set of nonlinear governing first-order differential equations, corresponding to the two-point boundary value problem, was conveniently solved using the shooting optimization method (SOM). The numerical results obtained from the presented FEM and SOM analyses independently verified each other, with good agreement between these two methods. The parametric study considered the effects of gravity load (pipe and fluid self-weights) and internal fluid pressure on the post-buckling characteristics of the VAL pipe. The numerical results showed that without the pipe and internal fluid weights, the transporting fluid exerted an axial compressive force on the pipe, causing post-buckling phenomena. Beyond the critical state, the support rotation and the length of the VAL pipe increased as the internal fluid velocity decreased. Finally, by including the effect of self-weight, the mode exchange of the odd buckling modes (1st and 3rd modes) was found from the load-displacement path.

Theoretical study on the most unfavorable tunnel length (MUTL) based on the interior pressure variations of high-speed subway trains

When a high-speed subway passes through a tunnel, the external aerodynamic pressure of the train is transmitted into the train interior, which adversely affects the passenger comfort. The effect of tunnel length on the interior pressure variation of the train cannot be ignored. According to previous studies, there is a most unfavorable tunnel length (abbreviated as MUTL in this paper) for the exterior pressure of the train. However, MUTL for the interior pressure variation is still a research gap. In this study, the effect of tunnel length on the interior pressure variation of tunnel and train was investigated using numerical simulation and TWS method. Additionally, the theoretical formula of MUTL based on the internal pressure variation at the head and tail of the train was established and verified using the results of past field measurements and TWS method. The findings indicate that the interior pressure variation with tunnel lengths within a certain time interval is not monotonic. Moreover, there may be two or even more MUTLs, and the MUTL is also be influenced by the dynamic sealing index. MUTL decreases with increasing train speed and increases with increasing number of cars. The research findings of this paper address the research gap in the study of MUTL on the pressure variation inside trains. These findings offer new theoretical guidance for the research of aerodynamic effects in high-speed subway tunnels, and provide a valuable reference engineering design and optimization.

Effects of Fatigue Parameters on Fatigue Crack Growth Rate of Pipe Steels and Girth Weld

Abstract Oil and gas pipeline steels and welds are subjected to a wide variety of cyclic loadings: internal pressure variation, pulsation of gas pressure resulting from the cyclic operation of a reciprocating compressor at a gas compressor station, internal flow-induced vibration resulting from the turbulent flow within the pipe, vortex-induced vibration of a free-spanning section exposed to air (wind) for aboveground pipelines or water for water-crossing pipelines, and cyclic thermal stresses developed by significant changes in temperature due to seasonal changes or changes in operating temperatures. These cyclic loadings are very variable and complex. Considering the fatigue situations, a better understanding of the effects of fatigue test parameters on fatigue behaviors of pipeline steels and welds is required. Hence, in this study, the influences of fatigue test parameters on the Paris law coefficients were studied for pipeline steels and welds. It was analyzed for pipe steels of X65∼X100 and a girth weld of X70. Influences of material strength, crack orientation relative to the pipe axis, and frequency in the range of 1∼30 Hz were insignificant. It was found that the coefficients a1 and b2 of the m-ln(C) relationships linearly relied on the load ratio. The constants (α1, β1, α2, and β2) of these linear relationships between R-ratio and a1 (and b2) were determined for pipe steels.

Modelling and optimisation of PV-PEMEC hydrogen generation system considering partial shading conditions

This study addresses the adverse effects of PSC on both PV output and PEMEC performance. It establishes a PV-PEMEC hydrogen production simulation model considering complex PSC scenarios. The analysis delves into the impacts of PSC on electrolyzer performance, including internal overpotential, internal pressure variation, and electrolysis efficiency. A hybrid GMPPT algorithm based on IGWO and AP&Q is proposed to mitigate PSC effects on the electrolyzer. The algorithm enhances population initialization with chaotic mapping and antagonistic learning mechanisms within the GWO algorithm. Additionally, it incorporates Levy flight and random walk strategies to improve local search capability, coupled with AP&Q to enhance convergence speed. Results indicate significant impacts of PV array PSC on PEM electrolyzer internal electrochemical mechanisms, particularly affecting Ohmic and diffusion overvoltages. Different local shading scenarios cause continuous fluctuations in electrolysis efficiency, more pronounced at lower current densities. PSC induces substantial fluctuations in hydrogen partial pressure and fewer fluctuations in oxygen partial pressure. The IGWO-AP&Q hybrid algorithm exhibits high responsiveness and tracking efficiency, yielding the highest PV-PEMEC electrolysis efficiency. This study effectively integrates complex multi-scenario PSC with PEMEC for solar-powered hydrogen production, laying a solid theoretical foundation for regions with high solar indices.

Hydrohelical ESP Gas Separator Increases Flow Range, Improves Reliability

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 214723, “New High-Performance ESP Gas Separator,” by Barry Nicholson, SPE, and Scott R. Harryman, SPE, Oxy, and Donn J. Brown, SPE, Halliburton, et al. The paper has not been peer reviewed. _ The complete paper presents research, design, and field testing of a new type of mechanical gas separator for electrical submersible pump (ESP) systems that increases operating flow range and separation efficiency while decreasing erosion problems and improving reliability. The hydrohelical separator system has been proved effective in different types of wells. Background Several methods and techniques exist for avoiding gas in ESPs, including inverted shrouds, passive separators, mechanical gas separators, and tandem gas separators. Most share the limitations of limited flow capabilities and reduced performance at higher total flow rates. The many variables associated with complex two-phase flow behavior, internal and external pressure variations, separation methods, velocity and viscosity of fluids, effect of the pump bolted above, inherent erosion issues, and single vs. tandem designs add to the challenge of basic mechanical gas-separator operation. In 2016, a program was initiated that featured investment in both experienced personnel and advanced testing technology to unravel the aforementioned challenges and improve understanding of the operation of downhole mechanical gas separation. The team investigated innovative methods of testing and created a transparent testing system that allowed visual observation of individual internal flow regimes as well as component performance. Using a combination of high-speed photography, computational fluid dynamics validation, and specialized instrumentation, every component of a mechanical separator system was enhanced for higher flow capabilities, improved separation efficiency, and higher reliability for a variety of downhole conditions. The result was the development of a new type of mechanical gas separator for ESP use. Development Most gas separators ingest multiphase fluid into a separation chamber, separate the gas and liquid phases, eject the separated gas phase into the well annulus, and provide sufficient liquid phase fluid to the pump to enable efficient pumping. Existing designs vary, but they share separation methods that result in decreased efficiency at higher flow rates and low maximum flow rates compared with the pumps they feed. The hydrohelical gas separator is the first downhole, dynamic gas-separator design improvement in more than 30 years designed to address these deficiencies (Fig. 1). The design was aimed at the following main objectives: - Increase total fluid flow rate through the separator - Maximize efficiency of every internal and external component of the system - Reduce erosion characteristics common in traditional gas-separator designs - Improve reliability The design of the hydrohelical gas separator is based on a stationary helical vortex inducer and pump stages that enable movement of large quantities of fluid while remaining immune to gas locking. The stationary helical vortex inducer design enables increased efficiency and flow rate through the separator by reducing turbulence in remixing regions within the helical inducer and separation chamber.

Fabrication and Experimental Investigation of Composite Pressure Vessel

Abstract: Composite pressure vessels are an important type of high-pressure containers that are widely used in aerospace industries. The pressure vessels develop hoop stresses that are twice the longitudinal stresses. CFRP (Carbon Fiber Reinforced Polymer) composite materials with their higher specific strength and characteristics will result in reduction of weight of the structure when compared with isotropic materials like steel. The present work is aimed in understanding the behaviour of the Composite Pressure Vessel with variation of internal pressure. In this connection, a pressure vessel using CFRP (Carbon Fiber Reinforced Polymer) is fabricated which can hold liquids or gases under pressure and is tested at various pressures. The FEA tool ANSYS 14.5 is used to determine better fiber angle required for liquid storage, when the conventional low carbon steel cylinder is replaced with CFRP Pressure Vessel.

Stress state analysis of root notch for X80 girth welds with variable wall thickness and misalignment geometric features

Notches formed due to weld geometric features seriously affect the structural safety of the pipeline. In this paper, the stress states of girth welds under various forming conditions and internal pressures are thoroughly evaluated via numerical simulation analysis. Controlled studies are carried out between crack-free and cracked welds. The susceptibilities of stress state to variations in internal pressure under different forming conditions are elucidated. Also, newly modified single-edge notch tensile specimens (MSENT) are manufactured, and the strain characteristic and fracture behavior analysis are performed. The calculation results reveal that the stress states of either the root notch or the crack tip are significantly intensified by welds' geometric features, and the increased brittle fracture sensitivity can be qualitatively demonstrated by MSENT analysis. Simultaneously, the misalignment continuously enhances the sensitivity of stress states to internal pressure variation. However, opposite patterns are observed between crack-free and cracked welds characterizing variable-wall-thickness features. The research results can provide a strong reference for the structural design, service evaluation, and related research of pipelines.

Mechanical behavior of PCCPs with broken wires under complex service conditions

Buried prestressed concrete cylinder pipes (PCCPs) are subjected to the combined effects of soil cover loads, internal water pressure, and additional loads. However, there is scarce research on their mechanical performance under complex service conditions after being buried. In this study, 3D nonlinear finite element (FE) models of PCCPs and soils, along with fluid models, were developed using ABAQUS and FLUENT, respectively. Fluid–solid coupling numerical simulations of PCCPs with broken wires under complex service conditions were conducted using the MpCCI platform. The study focused on investigating the mechanical behaviors of PCCP pipes with broken wires, aiming to determine the effects of different numbers and locations of broken wires, as well as the magnitude of operating water pressure. The results shows that the number of broken wires is a crucial factor affecting the mechanical behaviors of the PCCPs; the dynamic variation of internal pressure within the pipe can cause further damage to PCCPs with pre-existing defects; when wire breakage occurs alone the springline of the PCCPs, the outer concrete core exhibited a tendency to crack before the inner concrete core. Conversely, when wire breaks occurred at the crown and invert, the inner concrete core cracked before the outer concrete core. These results provide valuable insights into the behavior of PCCPs under complex conditions and contribute to the understanding of their structural integrity. The findings can aid in the development of improved design and maintenance strategies for PCCPs, ensuring their reliable performance in underground applications.

Rubber‐Like Soft Lattice Structure for Anti‐Ballooning in Fluidic Elastic Soft Robots

Additive manufacturing of lattice structures provides materials with enhanced strength, stiffness, and lightweight properties. While most research focuses on stiff, low‐stretch materials like metals and acrylonitrile butadiene styrene, herein, the tensile behavior of soft, elastomeric lattice structures is explored. Soft‐material 3D‐printing advancements have enabled increased usage of directly printed soft robots. Traditional fluidic elastic actuators, however, face limitations due to the ballooning effect of soft polymers, causing potential explosions or leakages. To mitigate this, the study proposes using a soft lattice structure to reinforce soft inflatable robots, thereby reducing the ballooning effect and increasing design freedom. Herein, soft lattices are fabricated using Agilus30 in a Stratasys J735 printer and their behaviors under compression and stretching are compared. It is indicated in the results that lattice reinforcement maintains the soft robot's shape under higher pressure and allows tunability of stiffness with variable internal pressure. The implementation of this method in non‐convex soft robots successfully demonstrates its anti‐ballooning effect.

Enhanced predictive method for pipeline strain demand subject to permanent ground displacements with internal pressure & temperature: a finite difference approach

Pipelines subject to ground deformations generated by geohazard loads carry high importance on pipeline analysis, design, and assessment due to risk of structural damage or failure. Additionally, internal pressure and temperature variation within an operating pipe induce additional strains in combination with pipe strains generated by ground displacement. In this study, an enhanced predictive method is proposed founded upon methods employed by Zheng et al. (2022) to assess pipeline behaviour subject to permanent ground displacement, while considering effects of internal operating pressure and temperature variation. The finite difference-based method previously proposed for strain analysis of buried steel pipes subject to ground movement ignores the effects of internal pressure and/or temperature loading, limiting the applicability of this approach to exclude the operating conditions of pipelines. To address this limitation, the proposed enhanced method accounts for the initial thermal strains and biaxial stress state in the pipe due to hoop stress generated by internal pressure. These additional strains are considered within the expressions of internal axial force and bending moment, derived based on the actual stress distribution on the pipe cross-section. The accuracy of the proposed method is validated against the finite element method (FEM) with respect to results of strain and deformation demand using several indicative case studies. This research provides an effective method of incorporating temperature and internal pressure loads of pipelines subject to permanent ground displacements of varying types, magnitudes, and directions.

Variation of peripheral pulse transit time with internal vascular pressure changes induced by arm movement.

Pulse transit time (PTT) and blood pressure (BP) are widely used to quantify arterial characteristics. Arm position influences arterial BP and peripheral PTT. This study aims to quantify the relationship between PTT changes with internal vascular pressure variations induced by the arm moving. With left arm at horizontal position as reference and the right arm moving from 90 to 45, 0, -45, and -90° respectively, PTT difference was calculated by the difference of the pulse foot between right arm and left arm within the same heartbeat. The change in the BP was calculated from the gravitational effect with the measured arm length. Our results showed that the change in PTT with arm elevating is more obvious than that with arm lowering, indicating the different relationship between PTT changes due to the internal BP changes. This can help in understanding the inherent physiological/pathological mechanism of cardiovascular system.

Feed-Forward Neural Network Based Petroleum Wells Equipment Failure Prediction

In the oil industry, the productivity of oil wells depends on the performance of the sub-surface equipment system. These systems often have problems stemming from sand, corrosion, internal pressure variation, or other factors. In order to ensure high equipment performance and avoid high-cost losses, it is essential to identify the source of possible failures in the early stage. However, this requires additional maintenance fees and human power. Moreover, the losses caused by these problems may lead to interruptions in the whole production process. In order to minimize maintenance costs, in this paper, we introduce a model for predicting equipment failure based on processing the historical data collected from multiple sensors. The state of the system is predicted by a Feed-Forward Neural Network (FFNN) with an SGD and Backpropagation algorithm is applied in the training process. Our model’s primary goal is to identify potential malfunctions at an early stage to ensure the production process’ continued high performance. We also evaluated the effectiveness of our model against other solutions currently available in the industry. The results of our study show that the FFNN can attain an accuracy score of 97% on the given dataset, which exceeds the performance of the models provided.

Shear dilation of subglacial till results in time-dependent sliding laws

The dynamics of glacial sliding over water-saturated tills are poorly constrained and difficult to capture realistically in large-scale models. Experiments characterize till as a plastic material with a pressure-dependent yield stress, but the subglacial water pressure may fluctuate on annual to daily timescales, leading to transient adjustment of the till. We construct a continuum two-phase model of coupled fluid and solid deformation, describing the movement of water through the pore space of a till that is itself dilating and deforming. By forcing the model with time-dependent effective pressure at the ice–till interface, we infer the resulting relationships between basal traction, solid fraction and rate of deformation. We find that shear dilation introduces internal pressure variations and transient dilatant strengthening emerges, leading to hysteretic behaviour in low-permeability materials. The result is a time-dependent effective sliding law, with permeability-dependent lag between changes in effective pressure and the slidingspeed. This deviation from traditional steady-state sliding laws may play an important role in a wide range of transient ice-sheet phenomena, from glacier surges to the tidal response of ice streams.

Ultraacoustic and conductometric studies on the interactions of l-glutamic acid with potassium sorbate and sodium benzoate in aqueous media

The objective of this investigation is to study and understand the nature of interactions between different ionic, polar and alkyl segments of l-glutamic acid (Glu) and food preservatives with carboxylate ions, e.g. Potassium sorbate (PS) and sodium benzoate (SB), with each other and with water. Acoustic properties were determined by measuring the velocity of ultrasonic sound (U) passing through the aqueous solutions of different concentration of Glu and PS/SB at 298.15 K. Compressibility parameters like isentropic compressibility (Ks), apparent molar isentropic compressibility (Ks,ϕ) and isothermal compressibility (KT) were analysed to elucidate the type of ion–solvent and ion-ion interactions and structural changes of water molecules in the solvation shells with the influence of solute (Glu) and cosolute (PS/SB) ions. Variation of relative association (RA), internal pressure (πi) and acoustic impedance (Z) with concentration of solute and cosolute in the solutions provide knowledge of ion-ion and ion–solvent interactions, structure building/breaking behavior of solute and cosolutes and formation of ion pairs or triplets. Additionally, electrical conductance (К) of the solutions was measured at different temperatures (T = 293.15–313.15 K with 5 K interval). Molar conductance values (Λm), Walden factor (Λm0η0), thermodynamic variables for the process of ion association (ΔGA,ΔHAandΔSA) and energy of activation (EA) for transportation of electrical charges were studied to explore the spontaneity of ion association and mobility of the charged particles through the solution. Critical evaluation of all these physicochemical and thermodynamic data leads to the conclusion that stronger ion–solvent interactions prevail in the solutions, Glu acts as a structure builder in attendance of PS/SB and the process of ion pair formation is spontaneous.

Mathematical modeling of forced oscillations of manometric tubular springs

Difficult working conditions, as well as vibrations of technological process units and unstable load intensity impose high demands on overpressure monitoring devices that ensure the required measurement accuracy and trouble-free operation of equipment. The use of pressure gauges today is a mandatory requirement for monitoring overpressure. The main type of pressure gauges uses manometric tubular springs (MTP) as elastic sensing elements. Therefore, the issue of calculating the motion of the MTP under the influence of external variable loads, in particular variable internal pressure, is relevant. Issues related to the influence of internal pressure pulsations and external periodically changing external forces remain unexplored. For successful operation, the strength and frequency characteristics of vibrations of tubular springs were previously investigated, the effects of cross-sectional shapes and basic geometric dimensions on their vibration characteristics were considered, and the process of vibration damping by liquid was analyzed. The paper presents a mathematical model of forced oscillations of the MTP based on Lagrange equations of the second kind. The MTP is considered as a mechanical system with two degrees of freedom, that is, defined by two generalized coordinates. They are a relative change in the main angle of the tube and an increase in the small semi-axis of the cross section. The model allows us to determine the nature of the movement of the MTP under the influence of periodically changing internal pressure. To implement it, a program has been developed in MATLAB, which makes it possible to determine the required characteristics of pressure monitoring devices that exclude the possibility of resonance. With the help of the developed program, the influence of geometric characteristics and internal pressure pulsations on the movements of the free end of the MTP is estimated. The presented model can be successfully used for dynamic calculations of manometric tubes, since it is a classical approach to solving problems of vibrations of mechanical systems. In addition, it will allow you to calculate the parameters of tubular elastic elements used in various mechanisms as power elements.

Gripe-Needle: A Sticky Suction Cup Gripper Equipped Needle for Targeted Therapeutics Delivery.

This paper presents a multi-purpose gripping and incision tool-set to reduce the number of required manipulators for targeted therapeutics delivery in Minimally Invasive Surgery. We have recently proposed the use of multi-arm Concentric Tube Robots (CTR) consisting of an incision, a camera, and a gripper manipulator for deep orbital interventions, with a focus on Optic Nerve Sheath Fenestration (ONSF). The proposed prototype in this research, called Gripe-Needle, is a needle equipped with a sticky suction cup gripper capable of performing both gripping of target tissue and incision tasks in the optic nerve area by exploiting the multi-tube arrangement of a CTR for actuation of the different tool-set units. As a result, there will be no need for an independent gripper arm for an incision task. The CTR innermost tube is equipped with a needle, providing the pathway for drug delivery, and the immediate outer tube is attached to the suction cup, providing the suction pathway. Based on experiments on various materials, we observed that adding a sticky surface with bio-inspired grooves to a normal suction cup gripper has many advantages such as, 1) enhanced adhesion through material stickiness and by air-tightening the contact surface, 2) maintained adhesion despite internal pressure variations, e.g. due to the needle motion, and 3) sliding resistance. Simple Finite Element and theoretical modeling frameworks are proposed, based on which a miniature tool-set is designed to achieve the required gripping forces during ONSF. The final designs were successfully tested for accessing the optic nerve of a realistic eye phantom in a skull eye orbit, robust gripping and incision on units of a plastic bubble wrap sample, and manipulating different tissue types of porcine eye samples.

Effect of the gust wave on the dynamic behavior of cavity closure and pressure: A numerical study

Ventilated partial cavity has been proven as an environmental-friendly and promising technology for ship drag reduction. However, the dynamic behavior of cavity closure and pressure under the wave effect still remains unclear. In this paper, the evolution of cavity shape and the oscillation of internal cavity pressure under the influence of different kinds of gust waves are investigated using the RANS coupled VOF method. Two types of cavity closure mode are found due to the presence of the gust wave. A strong correlation between the internal pressure variation and cavity oscillation behavior is revealed by the time–frequency analysis. Besides, it is found that the natural frequency of the cavity leads to an additional pressure fluctuation of the cavity, which is independent of waves.

Numerical Study of the Thermo-mechanical Behavior of 304L Stainless Steel Pipeline Junctions

The present paper is focused on the behavior of different junctions under the effect of internal pressure and temperature variation. The main junctions studied are of the T-junction and Y-junction type. The goal being to calculate the stress fields coupled to the temperature variation. This coupling realistically defines the thermo-mechanical behavior of the junction and in particular at the intersection where high stress concentrations are observed. The junction is an element widely used in industrial installations such as the cooling circuits of nuclear power plants which are subject to temperature fluctuations due to the mixture of hot fluids and cold these are called mixing zones. These fluctuations can lead to thermal or mechanical fatigue damage and cracking in the circuits causing leaks. Numerical modelling is carried out on the ANSYS calculation code based on the finite element method.