Fluid Pressure Research Articles

Design, Development, and Testing of Active Valve Piezo-hydraulic Pump

Abstract Valves play a major role in rectifying the fluid flow through piezo-hydraulic pumps, which may be active or passive. Passive valves operate due to changes in the fluid pressure whereas active valves are operated through control signals. This paper presents a novel design of an active valve chamber assembly for a piezo-hydraulic pump. It is a novel design since none of the research publications has addressed the application of a Flexurally amplified piezoelectric actuator (FAPA) for valve actuation in active valve chamber assembly. The piezo-hydraulic pump design is done using Solid Edge design software. FAPA’s are used for pumping and valve actuation. Structural analysis with experimental verification for the valve chamber component is presented. The valve opening and the pumping displacement are mathematically modeled in MATLAB Simulink software. Also, mathematical simulations for pump flow rates at different actuation frequencies and voltage are discussed. The piezo-hydraulic pump components are fabricated and assembled with the actuators. Experimental investigations on the flow rate performance of the active valve piezo-hydraulic pump are carried out with changing frequency and voltage amplitude of actuators. The interpretation of results is done by comparing the experimental and simulation results. During experiments, the pump delivered a maximum flow rate of 4.5mL/min at 140V when actuated at 0.25Hz actuation frequency.

Wireless and Battery-Free Sensor for Interstitial Fluid Pressure Monitoring

Congestive heart failure (CHF) is a fatal disease with progressive severity and no cure; the heart’s inability to adequately pump blood leads to fluid accumulation and frequent hospital readmissions after initial treatments. Therefore, it is imperative to continuously monitor CHF patients during its early stages to slow its progression and enable timely medical interventions for optimal treatment. An increase in interstitial fluid pressure (IFP) is indicative of acute CHF exacerbation, making IFP a viable biomarker for predicting upcoming CHF if continuously monitored. In this paper, we present an inductor-capacitor (LC) sensor for subcutaneous wireless and continuous IFP monitoring. The sensor is composed of inexpensive planar copper coils defined by a simple craft cutter, which serves as both the inductor and capacitor. Because of its sensing mechanism, the sensor does not require batteries and can wirelessly transmit pressure information. The sensor has a low-profile form factor for subcutaneous implantation and can communicate with a readout device through 4 layers of skin (12.7 mm thick in total). With a soft silicone rubber as the dielectric material between the copper coils, the sensor demonstrates an average sensitivity as high as –8.03 MHz/mmHg during in vitro simulations.

Epidural pressure measurement using a fiber-optic sensor (proof-of-principle invivo animal trial).

An increase in epidural pressure around the stenosis has been observed in patients with lumbar spinal stenosis (LSS) with positive signs of sedimentation or redundant nerve roots. Further analysis of the pressure conditions in the stenotic area would be of great interest. We hypothesized that it would be possible to determine the physiological parameters of the epidural pulse wave and its course in pathological stenosis as a basis for objective identification of LSS based on pressure using a new measuring method with continuous spatial and temporal resolution. We performed a single-case proof-of-principle invivo animal trial and used a newly developed hybrid pressure-measurement probe with a fiber-tip Fabry-Pérot interferometer and several fiber Bragg gratings (FBG). With reproducible precision, we determined the mean epidural pressure to be 7.5 mmHg and the peak-to-peak value to be 4-5 mmHg. When analyzing the pressure measured by an FBG array, both the heart and respiratory rates can be precisely determined. This study was the first to measure the pulse wave velocity of the cerebrospinal fluid pressure wave as 0.97 m/s using the newly developed pressure probe. A simulated LSS was detected in real time and located exactly. The developed fiber-optic pressure sensor probe enables a new objective measurement of epidural pressure. We confirmed our hypothesis that physiological parameters of the epidural pulse wave can be determined and that it is possible to identify an LSS.

A laboratory perspective on accelerating preparatory processes before earthquakes and implications for foreshock detectability

Dynamic failure in the laboratory is commonly preceded by many foreshocks which accompany premonitory aseismic slip. Aseismic slip is also thought to govern earthquake nucleation in nature, yet, foreshocks are rare. Here, we examine how heterogeneity due to different roughness, damage and pore pressures affects premonitory slip and acoustic emission characteristics. High fluid pressures increase stiffness and reduce heterogeneity which promotes more rapid slip acceleration and shorter precursory periods, similar to the effect of low geometric heterogeneity on smooth faults. The associated acoustic emission activity in low-heterogeneity samples becomes increasingly dominated by earthquake-like double-couple focal mechanisms. The similarity of fluid pressure increase and roughness reduction suggests that increased stress and geometric homogeneity may substantially shorten the duration of foreshock activity. Gradual fault activation and extended foreshock activity is more likely observable on immature faults at shallow depth.

Permeability of large‐scale fractures with ununiform proppant distributions in coalbed methane development

AbstractThe coalbed methane (CBM) productivity is directly determined by the fracture permeability during hydraulic fracturing, which is regulated by the distribution of proppants. The proppant may be unevenly distributed in the fracture because of variables like the architecture of the fracture and the characteristics of the sand‐carrying fluid. This study used two types of random functions to produce different ununiform distributions of proppant clusters in large‐scale fractures, with the aim of investigating the effect of these distributions on the overall permeability of the fracture. A model of fluid‐structure coupling is proposed. The closure of large‐scale fractures under in‐situ stress is analyzed using solid mechanics and the penalty function; the CBM flowing in proppant clusters and the high‐speed channel between them is simulated using Darcy's law and the Navier–Stokes equation, respectively; and the overall permeability of fractures is computed using the fluid pressure drop throughout the fracture and the fluid flowing velocity in the fracture's outlet. Since most CBM flows along high‐speed channels between the proppant clusters, the simulated findings show that the overall permeability of fractures with an uneven distribution of proppant clusters is significantly higher than that of the proppant cluster itself. As CBM becomes more discretely distributed, the proportion of CBM flowing within the proppant cluster continuously drops. As the permeability of the proppant cluster increases, the volume ratio of proppant clusters decreases, and the distribution of proppant clusters becomes more discrete, the overall permeability of the fracture continuously increases.

Impacts of Hydrostatic Pressure on Distributed Temperature-Sensing Optical Fibers for Extreme Ocean and Ice Environments

Optical fiber is increasingly used for both communication and distributed sensing of temperature and strain in environmental studies. In this work, we demonstrate the viability of unreinforced fiber tethers (bare fiber) for Raman-based distributed temperature sensing in deep ocean and deep ice environments. High-pressure testing of single-mode and multimode optical fiber showed little to no changes in light attenuation over pressures from atmospheric to 600 bars. Most importantly, the differential attenuation between Stokes and anti-Stokes frequencies, critical for the evaluation of distributed temperature sensing, was shown to be insignificantly affected by fluid pressures over the range of pressures tested for single-mode fiber, and only very slightly affected in multimode fiber. For multimode fiber deployments to ocean depths as great as 6000 m, the effect of pressure-dependent differential attenuation was shown to impact the estimated temperatures by only 0.15 °K. These new results indicate that bare fiber tethers, in addition to use for communication, can be used for distributed temperature or strain in fibers subjected to large depth (pressure) in varying environments such as deep oceans, glaciers and potentially the icy moons of Saturn and Jupiter.

Intraoperative fluid management is not predictive of AKI in major pancreatic surgery: a retrospective cohort study

BackgroundPancreatic surgery is associated with a significant risk for acute kidney injury (AKI) and clinically relevant postoperative pancreatic fistula (CR-POPF). This investigation evaluated the impact of intraoperative volume administration, vasopressor therapy, and blood pressure management on the primary outcome of AKI and the secondary outcome of a CR-POPF after pancreatic surgery.MethodsThis retrospective single-center cohort investigated 200 consecutive pancreatic surgeries (January 2018–December 2021). Patients were categorized for the presence/absence of AKI (Kidney Disease Improving Global Outcomes) and CR-POPF. After univariate analysis, multivariable models were constructed to control for the univariate cofactor differences in the primary and secondary outcomes.ResultsAKI was identified in 20 patients (10%) with significant univariate differences in demographics (body mass index and gender), comorbidities, indices of chronic renal insufficiency, and an increased AKI Risk score. Surgical characteristics, intraoperative fluid, vasopressor, and blood pressure management were similar in patients with and without AKI. Patients with AKI had increased blood loss, lower urine output, and packed red blood cell administration. After multivariate analysis, male gender (OR = 7.9, 95% C.I. 1.8–35.1) and the AKI Risk score (OR = 6.3, 95% C.I. 2.4–16.4) were associated with the development of AKI (p < 0.001). Intraoperative and postoperative volume, vasopressor administration, and intraoperative hypotension had no significant impact in the multivariate analysis. CR-POPF occurred in 23 patients (11.9%) with no significant contributing factors in the multivariate analysis. Patients who developed AKI or a CR-POPF had an increase in surgical complications, length of stay, discharge to a skilled nursing facility, and mortality.ConclusionIn this analysis, intraoperative volume administration, vasopressor therapy, and a blood pressure < 55 mmHg for more than 10 min were not associated with an increased risk of AKI. After multivariate analysis, male gender and an elevated AKI Risk score were associated with an increased likelihood of AKI.

Towards chemical source tracking and characterization using physics-informed neural networks

This paper presents a new algorithm using physics-informed neural networks (PINNs) to track and characterize spatio-temporally varying chemical sources based on time-resolved measurements of chemical concentration, fluid velocity, and pressure. Chemical source emission functions, chemical concentration, fluid velocity and fluid pressure fields are modeled as multi-layer percepterons (MLPs). During the training process, sensors readings of chemical concentratio, fluid velocity, and fluid pressure are matched to the output of the respective MLPs at the given spatio-temporal locations. Simultaneously, the physics of fluid flow and chemical dispersion at an arbitrary number of spatio-temporal locations in the domain of interest are enforced through regularization. Once trained, the constituent MLPs can be evaluated to generate the time resolved maps of source emissions, chemical concentration, fluid velocity and pressure. Extensive numerical simulation validate the method, including scenarios with both static and dynamic sources in complex flow fields. This innovative approach marks a significant advancement in environmental monitoring technologies.

Permeability evolution of fluid-injection-reactivated granite fractures of contrasting roughnesses

Fracture/fault instability induced by fluid injection in deep geothermal reservoirs could not only vary the reservoir permeability but also trigger hazardous seismicity. To address this, we conducted triaxial shear experiments on granite fractures with different architected roughnesses reactivated under fluid injection, to investigate the controls on permeability evolution linked to reactivation. Our results indicate that the fracture roughness and injection strategies are two main factors affecting permeability evolution. For fractures with different roughnesses, a rougher fracture leads to a lower peak reactivated permeability (kmax), and varying the fluid injection strategy (including the confining pressure and injection rate) has a less impact on kmax, indicating that the evolution of permeability during fluid pressurization is likely to be determined by the fracture roughness along the shear direction. Both the fracture roughness and injection strategies affect the average rates of permeability change and this parameter also reflects the long-term reservoir recovery. Our results have important implications for understanding the permeability evolution and the injection-induced fracture/fault slips in granite reservoirs during the deep geothermal energy extraction.

Development of numerical and experimental performance evaluation techniques for high-reliability turbine flow meters of ice-making water-dispenser

A turbine flowmeter for sensing the water supply in an ice-making system of a refrigerator requires high sensitivity to the flow rate. This research aims to develop a comprehensive performance evaluation technique by constructing an experimental setup and establishing a numerical technique to simulate the rotational motion of the impeller in response to the injection of water into the flowmeter. An experimental rig was built to secure the measurement accuracy according to the fluid temperature and pressure changes and verify the reliability under various flow conditions from low to high. A numerical method based on the six-degree of freedom method was used to confirm its validity, which is different from a moving reference frame, which numerically analyzes the rotational speed of the turbine by backtracking the rotational speed to correspond to the flow conditions by giving it a constant rotational speed. By simulating water injection into the flowmeter, generating kinetic energy in the impeller according to the flow rate, and subsequently rotating the impeller due to the generated torque, the numerical analysis cost was reduced, allowing direct numerical analysis of the impeller’s acceleration motion. The results were evaluated in terms of angular velocity and pulse signal, and the applicability and reliability of the numerical technique were verified by comparing the numerical results with experimental results. The aerodynamic performance of the impeller was analyzed to understand the phenomena as the impeller rotates. The results of this study can be utilized to conduct future research to improve the performance of flow meters, thus proving its value as a preliminary study.

Study on the Influence of Working Characteristics of Centripetal Pump Based on VOF/Mixture Model

Aviation fuel contamination can seriously affect aircraft flight safety, and the centripetal pump is the core component of aviation fuel purification equipment. The performance of centripetal pumps is highly demanded for purification equipment. The operating parameters of centripetal pumps significantly affect the internal flow characteristics, which affects the performance of centripetal pumps. However, the flow characteristics of a centripetal pump influenced by the operating parameters have not yet been elaborated upon. In this research, a three-dimensional numerical simulation of the air-fuel two-phase flow field inside a centripetal pump was carried out using the VOF/Mixture model to investigate the effects of three relatively independent physical quantities, namely, fuel flow, outlet fuel discharge pressure, and rotational speed, on the operating characteristics of the centripetal pump. The flow law inside the flow channel of a centripetal pump was analyzed based on a rotating fluid pressure model, the free liquid surface radius of air-fuel, and the total pressure recovery coefficient. It was found that centripetal pumps have a steady working state and an unsteady working state. In a steady working state, the proportion of separated zones in the flow channel of the centripetal pump is small, the flow coefficient C of the flow channel is greater than 1, and the total pressure recovery coefficient of the centripetal pump is high. In an unsteady working state, the separation zone in the flow channel of the centripetal pump accounts for a large proportion, the flow channel flow coefficient C is less than 1, and the total pressure recovery coefficient of the centripetal pump is low. An unsteady working state can easily occur in small flow, high-speed conditions. By analyzing the working state and flow characteristics of the centripetal pump, the mechanism of the influence of the flow, outlet fuel discharge pressure, and rotational speed on the working state of the centripetal pump is revealed, which provides a basis for the stable operation of the centripetal pump.

The Complex Tumor Microenvironment in Ovarian Cancer: Therapeutic Challenges and Opportunities

The tumor microenvironment (TME) in ovarian cancer (OC) has much greater complexity than previously understood. In response to aggressive pro-angiogenic stimulus, blood vessels form rapidly and are dysfunctional, resulting in poor perfusion, tissue hypoxia, and leakiness, which leads to increased interstitial fluid pressure (IFP). Decreased perfusion and high IFP significantly inhibit the uptake of therapies into the tumor. Within the TME, there are numerous inhibitor cells, such as myeloid-derived suppressor cells (MDSCs), tumor association macrophages (TAMs), regulatory T cells (Tregs), and cancer-associated fibroblasts (CAFs) that secrete high numbers of immunosuppressive cytokines. This immunosuppressive environment is thought to contribute to the lack of success of immunotherapies such as immune checkpoint inhibitor (ICI) treatment. This review discusses the components of the TME in OC, how these characteristics impede therapeutic efficacy, and some strategies to alleviate this inhibition.

Compaction Creep and Evolution of Transport Properties of Carbonate Fault Gouges During the Percolation of CO2‐Rich Fluids

AbstractTo investigate the impact of CO2‐rich fluids on compaction behaviors and transport properties in carbonate fault zones, we conducted compaction‐coupled fluid flow experiments with CO2‐rich fluids percolating precompacted calcite aggregates. Our findings reveal distinct responses among samples subjected to different fluid conditions. Specifically, samples exposed to dry conditions exhibited negligible compaction strain, while those under wet‐closed conditions displayed relatively minor strain. In contrast, samples subjected to flow‐through conditions demonstrated significant compaction strain, with strain rates higher by 2–3 orders of magnitude than closed conditions due to enhanced pressure solution, subcritical cracking, and chemical dissolution. Strain rate, permeability, and grain size distribution exhibited spontaneous variations in response to fluid flow and compaction. Microstructures and mechanical and transport data suggest that deformation during the initial infiltration of CO2‐rich fluids was dominated by subcritical cracking, followed by pressure solution as grain size evolved, which resulted in compaction and reduced permeability. The persistent infiltration of CO2‐rich fluids further enhanced inhomogeneous dissolution‐precipitation with preferred dissolution channels serving as fluid pathways. The re‐precipitations may cement fault rocks and form low permeability seals, resulting in anisotropic fluid flow and localized fluid pressure in fault zones. As applied to nature, our results provide experimental evidence for the evolution of internal structures and transport behaviors, shedding important light on the mechanisms and sealing potential of carbonate faults in response to the infiltration of CO2‐rich fluids during the post‐seismic and inter‐seismic processes.

Stress Field Dynamics and Fault Slip Potential in the Paradox Basin

AbstractThe Paradox Basin, straddling Utah, Colorado, Arizona, and New Mexico is characterized by an intricate amalgamation of evaporites and clastic layers and is dominated by prominent salt walls and related subsurface structures. Our research offers a new examination of the stress distribution across the basin, deriving from continuous and discrete stress measurements conducted in boreholes in the region and focal mechanism analysis, emphasizing variations over salt structures. Integrating Coulomb failure criteria with probabilistic methods, we assess potential fault movements resulting from fluid pressure alterations. Our approach provides a comprehensive understanding of the Paradox Basin's state of stress, showing a continuous change of the maximum horizontal stress orientation from N‐S at the Wasatch Fault Zone to WNW‐ESE in the northern part of the Paradox Basin and to WSW‐ENE in the southern part of the basin. Further East, into the Colorado Plateau and the Uncompahgre Uplift, the SHmax orientation becomes E‐W. Decoding stress orientation dynamics has enabled critical insights into fault slip potential, especially in the basin's northern region. The salt wall faults are less likely to slip, and the Paradox Formation's evaporite and clastic rock sequence can serve as a potential low seismic risk target for carbon storage and hydrocarbon extraction.

Micro-fracture propagation and numerical simulation of fracture propagation under thermal simulation experiment of organic-rich shale: Chang-7 source rock in Yanchang, Ordos Basin

Organic-rich shale as a high-quality source rock which is usually deposited in a high-temperature and high-pressure environment, and its internal organic matter will gradually transform into hydrocarbon and be discharged from shale. However, shale has polar porosity and permeability, making it difficult for hydrocarbon to be discharged from the shale through the pore throat. The latest research suggests that due to the strong hydrocarbon generation potential of shale rich in organic matter, the pressure generated by hydrocarbon can cause micro-fracture in the shale, leading to the expulsion of hydrocarbon from the micro-fracture. Therefore, this article uses hydrocarbon generation simulation experiments and Comsol Multiphysics to analyze the mechanical characteristics and damage propagation of micro-fracture during shale hydrocarbon generation process. The results show that with the increase of temperature and fluid pressure, micro-fracture of different lengths have different initial fracture pressures, and during the diffusion of micro-fracture, the stress inside the shale matrix and micro-fracture exhibits different diffusion characteristics.

Note on quasi-optimal error estimates for the pressure for shear-thickening fluids

In this paper, we derive quasi-optimal a priori error estimates for the kinematic pressure for a Local Discontinuous Galerkin (LDG) approximation of steady systems of $p$-Navier--Stokes type in the case of shear-thickening, \textit{i.e.}, $p&gt;2$, imposing a new Muckenhoupt regularity condition on the viscosity of the fluid, which is mild in the two-dimensional case but potentially restrictive in the three-dimensional case.

Adhesion-Lubrication Paradox of Articular Cartilage.

The friction of solids is primarily understood through the adhesive interactions between the surfaces. As a result, slick materials tend to be nonstick (e.g., Teflon), and sticky materials tend to produce high friction (e.g., tires and tape). Paradoxically, cartilage, the slippery bearing material of human joints, is also among the stickiest of known materials. This study aims to elucidate this apparent paradox. Cartilage is a biphasic material, and the most cited explanation is that both friction and adhesion increase as load transfers from the pressurized interstitial fluid to the solid matrix over time. In other words, cartilage is slippery and sticky under different times and conditions. This study challenges this explanation, demonstrating the strong adhesion of cartilage under high and low interstitial hydration conditions. Additionally, we find that cartilage clings to itself (a porous material) and Teflon (a nonstick material), as well as other surfaces. We conclude that the unusually strong interfacial tension produced by cartilage reflects suction (like a clingfish) rather than adhesion (like a gecko). This finding is surprising given its unusually large roughness, which typically allows for easy interfacial flow and defeats suction. The results provide compelling evidence that cartilage, like a clingfish, conforms to opposing surfaces and effectively seals submerged contacts. Further, we argue that interfacial sealing is itself a critical function, enabling cartilage to retain hydration, load support, and lubrication across long periods of inactivity.

Constraints on fracture connectivity from AVAz analysis

The analysis of seismic reflection amplitude variations with incidence angle and azimuth (AVAz) is a powerful tool for studying and characterizing fractured formations. There is evidence to suggest that wave-induced fluid pressure diffusion (FPD) within connected fractures can significantly affect the AVAz response. This, in turn, indicates that this seismic attribute may contain information on the connectivity degree of the fracture network, which represents a key hydraulic property of fractured formations. The assessment of the sensitivity of seismic reflectivity with respect to fracture connectivity accounting for FPD effects is so far limited to 2D models, which is mainly due to the complexity and the associated computational cost of modeling the effective properties of corresponding generically anisotropic 3D media. To overcome these issues, we employ a numerical upscaling procedure based on Biot’s theory of poroelasticity that allows us to obtain effective anisotropic representations of 3D fractured formations accounting for FPD effects. Using these effective properties, we then perform a plane-wave analysis to compute the reflection coefficients at the top of the corresponding fractured formation. The results of our numerical analyses extend previous 2D studies and demonstrate that seismic reflection coefficients are highly sensitive to the degree of connectivity of the fracture networks. The reflectivity responses of formations comprising connected and unconnected fractures show pronounced differences not only with respect to incidence angle, but also with respect to azimuth. Quite importantly, our results also demonstrate that crossplots of commonly used AVAz coefficients permit us to identify regions with higher or lower fracture connectivity.

Fatigue performance testing and life prediction of welded fuel pipes

The external piping system which connects power devices, valve control devices, actuators, etc. is an essential system on the aero engine. Under the combined effects of high fluid pressure and external vibration, multiaxial fatigue failure is the main factor that seriously affects the safety of the piping system. The objective of this paper is to establish the multiaxial fatigue life model for the typical welded fuel pipe of the piping system by combining fatigue testing, simulation and theoretical analysis which is of great guiding significance for the engineering application of the piping system. Firstly, the fatigue limits of welded fuel pipes under no and 13.5 MPa internal pressure are obtained by rotational bending fatigue tests using the up-and-down method. Three additional stress levels of rotational bending fatigue tests under no internal pressure are supplemented and then the S-N curve is further obtained by the group method. Since the corresponding fracture surface of the specimens locates at the weld toe near the fixed end, peak stress method is adopted to evaluate the fatigue performance of the weld toe on the pipe specimens. In addition, by comparing the fatigue limit with no and 13.5 MPa internal pressured pipes, it is obvious that the equivalent uniaxial stress corrected by Gerber formula is not applicable for the multiaxial fatigue condition which is caused by the combined effect of fluid pressure and displacement load. The local stress concentration factor caused by the weld toe is determined and based on Findley critical plane model, the multiaxial fatigue life model is established which simultaneously takes the local stress concentration effect, mean stress effect and multiaxial stress effect into consideration. The results of rotational bending fatigue tests under 13.5 MPa internal pressure are within the triple error dispersion band and the accuracy of the proposed life model are verified.

Modelling of water injection-induced shear stimulation and heat extraction in hot fractured reservoirs

Hydroshearing has been proposed as an effective technique for enhancing the permeability of fractured geothermal reservoirs. This approach involves complicated thermo-hydro-mechanical (THM) coupling, but the shear behaviour and its effect on flow and heat transfer are often simplified. In this study, Barton–Bandis (BB) joint behaviour is extended to include nonlinear rock joint deformation, shear dilation and post peak softening and healing behaviours. Two models of field-scale fractured geothermal reservoirs are considered. In addition, the widely used Mohr-Coulomb (MC) model is also incorporated into the THM coupled model for comparison. The results show that cold water injection-induced high-temperature rock contraction and fluid pressure increase, reducing the effective stress and promoting fracture shear deformation and irreversible slip. Moreover, shear dilation, shear softening, and nonlinear fracture opening notably alter reservoir permeability. The two models exhibit entirely different behaviours due to different pathway evolutions and consequent pressure build-up. The BB model displays a larger shear disturbance zone than the MC model, significantly enhancing the permeability and heat extraction within the fractured reservoirs. Accurate descriptions of the mechanical behaviour of rock fractures in hydroshearing models are crucial, suggesting the potential of these models to enhance fractured reservoirs and regulate fracturing for improved geothermal heat extraction.