Spatial Pressure Distribution Research Articles

Quantitative assessment of acoustic field characteristics in water by radial extracorporeal shockwave therapy

Radial extracorporeal shockwave therapy (rESWT) is a noninvasive medical technique that treats a range of musculoskeletal conditions. To understand its biological effects and develop personalized treatment plans, it is crucial to fully characterize the acoustic field that rESWT generates. This study presents a quantitative assessment of rESWT's acoustic field, achieved through experiments and simulations. The study measures the acoustic fields using a needle-type hydrophone under different machine settings and establishes and calibrates a computational model based on the experimental measurements. The study also determines the spatial distributions of peak pressure and energy flux density for different driving pressures. High-speed photography is used to visualize cavitation bubbles, which correspond to the negative pressure distribution. The study finds that the axial pressure distribution is similar to the acoustic radiation from an oscillating circular piston, whereas the radial pressure distribution cannot be described by acoustic radiation. Furthermore, the study develops a machine learning model that predicts positive pressure distributions for continuous driving pressure. Overall, this study expands our understanding of the acoustic fields generated by rESWT and provides quantitative information to explore underlying biological mechanisms and determine personalized treatment approaches.

Constructing high-density crack-microstructures within MXene interlayers for ultrasensitive and superhydrophobic cellulosic fibers-based sensors

Incorporating biopolymers into two-dimensional transition metal carbides and/or nitrides (2D MXene) has been demonstrated as an effective strategy to improve the mechanical behaviors of MXene-based composites. However, the insulate nature of biopolymers inevitably deteriorated the electrical conductivity and the sensitivity of assembled sensors. Herein, a novel cellulose nanofiber (CNF)/MXene/carbon black (CB) composite was demonstrated as the conductive layer in eco-friendly cellulose paper-based sensors by intercalating the CB into the MXene/CNF interlayer, followed by coating hydrophobic SiO2 for encapsulation. Befitting from the high-density crack-microstructures between CB and MXene, the fabricated superhydrophobic paper CB/CNF/MXene/SiO2 sensor delivered ultrahigh sensitivity of 729.52 kPa−1, low detect limit of 0.29 Pa, rapid response time of 80 ms and excellent stability over 10,000 cycles. Moreover, the fabricated sensor was capable of detecting the physiological parameter of human (e.g. huge/subtle movements) and spatial pressure distribution. Furthermore, the presence of SiO2 layer endowed the sensor with superhydrophobic performance (water contact angle ∼158.2 o) and stable electrical signals under high moisture conditions or even under water. Our work proposed a novel strategy to boost the sensitivity of MXene-based conductive layer in flexible electronic devices.

Printing paper-derived ultralight and highly sensitive E-skin for health monitoring and information encryption

Simplified fabrication technology and excellent sensing performance are highly desired for the development of flexible and user-friendly wearable sensors. However, there is usually a trade-off between the simplicity of the fabrication technology and the sensing performance of the device. Recently, paper-based wearable sensors have attracted much attention due to their excellent flexibility, simplified preparation, and low cost etc. However, the pressure sensitivity of the paper-derived sensors is far from satisfactory. In this work, a strategy of pencil graphite frottage (PGF) is reported by employing sandpaper as template and a pencil sketch technique to achieve functional printing paper as pressure-sensitive layers for electronic skin (e-skin). As a result, the e-skin prepared by our PGF technique shows excellent reproducibility and pressure sensing performance, including a maximum sensitivity of 7202.2 kPa−1, a fast response time of 25.0 ms, and an excellent durability over 20,000 loading/unloading cycles, and high ambient stability (> 6 months). For application demonstration, the e-skins are applied to monitor human wrist pulses, acoustical vibration and information encryption. Furthermore, pressure sensing arrays are developed and employed to map the spatial pressure distribution, indicating potential application in intelligent robots and prosthetics. It is believed that the fabrication strategies proposed in this work can bring insight onto the other area of bionic e-skin and multifunctional sensor devices.

Multiphysical evolution and dynamic competition involved in natural gas hydrate dissociation in porous media and its implications for engineering

Hydrate (shorted for natural gas hydrate) is one of the most promising future energies, and dissociating hydrate in situ is commonly recognized as the best strategy to realize commercial exploitation. So it is significant to understand the fundamental mechanism in the process of hydrate dissociation involving complicated thermal-hydraulic-mechanical-chemical phenomena. To date, the multiphysical evolution patterns are not revealed by the overall comparison among different phenomena, and we still have little knowledge on the contributions of different influence factors to hydrate dissociation rate. More importantly, the fundamental study has a considerable gap to the real engineering. Therefore, in this paper, a fully-coupled thermal-hydraulic-mechanical-chemical model is developed to further analyze the evolution of all phenomena from both global and local perspectives and find the coupled relationships among physical/chemical phenomena from a dynamic competition perspective. Results show that the global spatial distributions of pressure, hydrate saturation and strain show one simple pattern during hydrate dissociation，while those of temperature and hydrate dissociation rate manifest four and three complex patterns respectively. The effective hydrate reaction specific area, reaction coefficient and pressure difference play different roles in the domination of the trend and value of hydrate dissociation rate. Additionally, two examples are given to demonstrate the implications of the fundamental mechanism to the engineering. A negative-power-law relation is found between the finish time of hydrate dissociation and the heat transfer coefficient of outside heat source (geothermal heat in real engineering). A good linear relation between hydrate dissociation front and pressure transfer front is found, which provides a possible easy way to predict the range of dissociated hydrate by pressure in the real engineering.

Free-Boundary Plasma Equilibrium Computation in Spherical Globus-M2 Tokamak by Means of the pyGSS Code

The pyGSS code constructed for computation of free-boundary plasma equilibrium in sphericalGlobus-M2 tokamak is described. Currents in the coils of the electromagnetic system, their coordinates,plasma current, positions of the limiter and current-conducting wall, etc., are used as the input parameters.Free parameters determining spatial distribution of equilibrium pressure and current density are selected inthe course of code execution in such a way that the results of reconstruction would agree with the experimentalmeasurements of the poloidal magnetic flux by means of toroidally closed loops. The results of computationof equilibrium are compared with those obtained by means of other codes and experimentally measuredthermal plasma energy, position of the separatrix outer leg, the diamagnetic-loop signal, etc.

Subject-specific one-dimensional fluid dynamics model of chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) develops due to the accumulation of blood clots in the lung vasculature that obstructs flow and increases pressure. The mechanobiological factors that drive progression of CTEPH are not understood, in part because mechanical and hemodynamic changes in the small pulmonary arteries due to CTEPH are not easily measurable. Using previously published hemodynamic measurements and imaging from a large animal model of CTEPH, we applied a subject-specific one-dimensional (1D) computational fluid dynamic (CFD) approach to investigate the impact of CTEPH on pulmonary artery stiffening, time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) in extralobar (main, right, and left) pulmonary arteries and intralobar (distal to the extralobar) arteries. Our results demonstrate that CTEPH increases pulmonary artery wall stiffness and decreases TAWSS in extralobar and intralobar arteries. Moreover, CTEPH increases the percentage of the intralobar arterial network with both low TAWSS and high OSI, quantified by the novel parameter φ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varphi$$\\end{document}, which is related to thrombogenicity. Our analysis reveals a strong positive correlation between increases in mean pulmonary artery pressure (mPAP) and φ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varphi$$\\end{document} from baseline to CTEPH in individual subjects, which supports the suggestion that increased φ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varphi$$\\end{document} drives disease severity. This subject-specific experimental–computational framework shows potential as a predictor of the impact of CTEPH on pulmonary arterial hemodynamics and pulmonary vascular mechanics. By leveraging advanced modeling techniques and calibrated model parameters, we predict spatial distributions of flow and pressure, from which we can compute potential physiomarkers of disease progression. Ultimately, this approach can lead to more spatially targeted interventions that address the needs of individual CTEPH patients.

Flexible capacitive pressure sensor based on interdigital electrodes with porous microneedle arrays for physiological signal monitoring

Flexible pressure sensors have many potential applications in the monitoring of physiological signals because of their good biocompatibility and wearability. However, their relatively low sensitivity, linearity, and stability have hindered their large-scale commercial application. Herein, a flexible capacitive pressure sensor based on an interdigital electrode structure with two porous microneedle arrays (MNAs) is proposed. The porous substrate that constitutes the MNA is a mixed product of polydimethylsiloxane and NaHCO3. Due to its porous and interdigital structure, the maximum sensitivity (0.07 kPa−1) of a porous MNA-based pressure sensor was found to be seven times higher than that of an imporous MNA pressure sensor, and it was much greater than that of a flat pressure sensor without a porous MNA structure. Finite-element analysis showed that the interdigital MNA structure can greatly increase the strain and improve the sensitivity of the sensor. In addition, the porous MNA-based pressure sensor was found to have good stability over 1500 loading cycles as a result of its bilayer parylene-enhanced conductive electrode structure. Most importantly, it was found that the sensor could accurately monitor the motion of a finger, wrist joint, arm, face, abdomen, eye, and Adam’s apple. Furthermore, preliminary semantic recognition was achieved by monitoring the movement of the Adam’s apple. Finally, multiple pressure sensors were integrated into a 3 × 3 array to detect a spatial pressure distribution. Compared to the sensors reported in previous works, the interdigital electrode structure presented in this work improves sensitivity and stability by modifying the electrode layer rather than the dielectric layer.

Investigation on the pore water pressure in steel bridge deck pavement under the coupling effect of water and vehicle load

The water damage is a severe problem existing steel bridge deck pavement (SBDP) and still has not been fully studied. To investigate the pore water pressure of SBDP under the coupling effect of water and vehicle load, some typical permeability characterization parameters are selected firstly. Then, the water permeability simulation model under the most unfavorable vehicle load is established. Next, the spatial distribution of pore water pressure in different area of SBDP is analyzed and compared. Lastly, the process of water flow and pore water pressure changes are discussed. Results show that the simulation results are consistent with the characteristics of water permeability phenomenon during practical vehicle travel. The process of water flow and pore water pressure changes is corresponding to the pumping phenomenon in the engineering practice. This positive and negative cycle of pore water pressure could lead to spalling between asphalt and aggregate, which would accelerate the appearance and development of SBDP distress. This paper clarifies the permeability characteristics and pore water pressure change in SBDP. The findings are important for the design, construction and maintenance of SBDP to mitigate or avoid water damage.

Fabrication of high-resolution, wide-range and low-crosstalk capacitive pressure sensing array for medical diagnosis

Flexible pressure sensors have found widespread application in medical diagnosis and human–computer interaction. These practical applications often require large-area pressure sensing arrays (PSAs) to explore spatial pressure distributions. However, the development of high-performance PSAs still presents significant challenges. Here, a new method is proposed for the fabrication of a high-resolution capacitive PSA in a 10 × 10 configuration. The array comprises the upper and lower electrode arrays of laser-induced graphene patterned on polyimide films, as well as the sandwiched dielectric units based on electrospun nanofiber membranes of H3PO4@PVPP (cross-linked polyvinyl pyrrolidone). Experimental results indicate that the PSA exhibits high sensitivity across a wide pressure range (0–200 kPa), while offering a rapid response/recovery time of 24/41 ms (at 1 kPa), an exceptionally low detection limit of ∼1.2 Pa, and a good stability of 4000 cycles. Moreover, the crosstalk of the PSA was found to be as low as 1.3%. By employing the PSA in conjunction with a convolutional neural network algorithm, a human foot-arch diagnostic system was developed for accurate detection and quantification of the plantar pressure for different types of foot arches. Such technology has significant potential in clinical detection and disease diagnosis of human foot.

A Numerical Study of the Hydrodynamic Noise of Podded Propulsors Based on Proper Orthogonal Decomposition

Podded propulsors have become a focal point of research in the field of marine propulsion in recent years due to their high efficiency, low noise, and excellent maneuverability. To investigate the acoustic characteristics induced by the flow field of podded propulsors, a high-precision unsteady numerical simulation was conducted using the Delayed Detached Eddy Simulation (DDES) coupled with Ffowcs Williams–Hawkings (FW-H) equations. Multiple spatial acoustic receiving arrays were employed, and analysis methods including Proper Orthogonal Decomposition (POD) and Fast Fourier Transform (FFT) were utilized to determine the spatial distribution of the acoustic field of the podded propulsor. The results show that the blade passing frequency and the shaft frequency consistently dominate as the primary characteristic frequencies. On the plane of the propeller disk, the distribution of sound pressure levels is uniform without distinct directivity. Across the space curved surface, approximately the first ten POD modes encompass 99.8% of the total energy, and their spatial distribution characteristics of sound pressure are closely related to the pod structure. Additionally, these modes exhibit characteristic frequencies such as the blade passing frequency and shaft frequency. The spatial distribution of sound pressure at a single frequency on the spatial surface corresponds well with the results obtained from the POD analysis.

Large-scale fabrication of conductive yarn with synergistic conductive coating for high-efficient strain sensing and photothermal conversion

With the rapid development of wearable electronics, conductive yarn strain sensors have attracted much attention due to their excellent flexibility, conformability, and knittability. However, it is still a great challenge to prepare flexible conductive yarn strain sensors with high sensitivity and wide working range simultaneously. Here, a large-scale fabrication of conductive spandex yarn (SY) with synergistic conductive coating composed of lower stable carbon nanotubes (CNTs)-polyaniline (PANi) hybrid layer and upper ultrasensitive cracked PANi layer was successfully achieved via the simple solvent swelling, non-solvent-induced phase separation (NIPS), and in-situ reduction processes. Thanks to the synergistic effect of the double layered conductive coating and its tunable microstructure based on the PANi content, the assembled conductive SY strain sensor exhibits wide working range (0–321 %), high sensitivity (GF is 43, 950, and 2439 for strain range of 0–100 %, 170–270 %, and 280–321 %, respectively), ultralow detection limit (0.5 %), fast response/recovery time (140 ms/160 ms), and excellent fatigue resistance (4000 cycles). As a proof of concept, the strain sensor can be used for wearable applications to achieve the effective detection of full-range human motion and physiologic signals. Besides, it also displays great potential in human-computer interaction for reliable operation of remote-control manipulator and flexible electronic textile for spatial pressure distribution identification. Finally, owing to the excellent optical absorbing ability of PANi and CNTs, the conductive SY exhibits high-efficient and stable photothermal conversion capacity even under the stretching and bending states, endowing it with good wearing comfort. This study provides a convenient but effective strategy for the fabrication of high-performance wearable strain sensor with excellent thermal management capacity.

Image-Based Modeling of Drug Delivery during Intraperitoneal Chemotherapy in a Heterogeneous Tumor Nodule.

Intraperitoneal (IP) chemotherapy is a promising treatment approach for patients diagnosed with peritoneal carcinomatosis, allowing the direct delivery of therapeutic agents to the tumor site within the abdominal cavity. Nevertheless, limited drug penetration into the tumor remains a primary drawback of this method. The process of delivering drugs to the tumor entails numerous complications, primarily stemming from the specific pathophysiology of the tumor. Investigating drug delivery during IP chemotherapy and studying the parameters affecting it are challenging due to the limitations of experimental studies. In contrast, mathematical modeling, with its capabilities such as enabling single-parameter studies, and cost and time efficiency, emerges as a potent tool for this purpose. In this study, we developed a numerical model to investigate IP chemotherapy by incorporating an actual image of a tumor with heterogeneous vasculature. The tumor's geometry is reconstructed using image processing techniques. The model also incorporates drug binding and uptake by cancer cells. After 60 min of IP treatment with Doxorubicin, the area under the curve (AUC) of the average free drug concentration versus time curve, serving as an indicator of drug availability to the tumor, reached 295.18 mol·m-3·s-1. Additionally, the half-width parameter W1/2, which reflects drug penetration into the tumor, ranged from 0.11 to 0.14 mm. Furthermore, the treatment resulted in a fraction of killed cells reaching 20.4% by the end of the procedure. Analyzing the spatial distribution of interstitial fluid velocity, pressure, and drug concentration in the tumor revealed that the heterogeneous distribution of tumor vasculature influences the drug delivery process. Our findings underscore the significance of considering the specific vascular network of a tumor when modeling intraperitoneal chemotherapy. The proposed methodology holds promise for application in patient-specific studies.

All-Fabric Capacitive Pressure Sensors with Piezoelectric Nanofibers for Wearable Electronics and Robotic Sensing.

Flexible pressure sensors are increasingly sought after for applications ranging from physiological signal monitoring to robotic sensing; however, the challenges associated with fabricating highly sensitive, comfortable, and cost-effective sensors remain formidable. This study presents a high-performance, all-fabric capacitive pressure sensor (AFCPS) that incorporates piezoelectric nanofibers. Through the meticulous optimization of conductive fiber electrodes and P(VDF-TrFE) nanofiber dielectric layers, the AFCPS exhibits exceptional attributes such as high sensitivity (4.05 kPa-1), an ultralow detection limit (0.6 Pa), an extensive detection range (∼100 kPa), rapid response time (<26 ms), and robust stability (>14,000 cycles). The sensor's porous structure enhances its compressibility, while its piezoelectric properties expedite charge separation, thereby increasing the interface capacitance and augmenting overall performance. These features are elucidated further through multiphysical field-coupling simulations and experimental testing. Owing to its comprehensive superior performance, the AFCPS has demonstrated its efficacy in monitoring human activity and physiological signals, as well as in discerning soft robotic grasping movements. Additionally, we have successfully implemented multiple AFCPS units as pressure sensor arrays to ascertain spatial pressure distribution and enable intelligent robotic gripping. Our research underscores the promising potential of the AFCPS device in wearable electronics and robotic sensing, thereby contributing significantly to the advancement of high-performance fabric-based sensors.

Operando Spatial Pressure Mapping Analysis for Prototype Lithium Metal Pouch Cells Under Practical Conditions.

Monitoring and diagnosing the battery status in real-time are of utmost importance for clarifying failure mechanism, improving battery performance, and ensuring safety, particularly under fast charging conditions. Recently, advanced operando techniques have been developed to observe changes in the microstructures of lithium deposits using laboratory-scale cell designs, focusing on understanding the nature of Li metal electrodes. However, the macroscopic spatial inhomogeneity of lithium electroplating/stripping in the prototype pressurized pouch cells has not been measured in real-time under practical conditions. Herein, a new noninvasive operando technique, spatial pressure mapping analysis, is introduced to macroscopically and quantitatively measure spatial pressure changes in a pressurized pouch cell during cycling. Moreover, dynamic spatial changes in the macroscopic morphology of the lithium metal electrode are theoretically visualized by combining operando pressure mapping data with mechanical analyses of cell components. Additionally, under fast charging conditions, the direct correlation between abrupt capacity fading and sudden increases in spatial pressure distribution inhomogeneity is demonstrated through comparative analysis of pouch cells under various external pressures, electrolyte species, and electrolyte weight to cell capacity (e/c) ratios. This operando technique provides insights for assessing the current battery status and understanding the complex origin of cell degradation behavior in pressurized pouch cells.

Highly-sensitive expandable microsphere-based flexible pressure sensor for human–machine interaction

Flexible microstructural pressure sensors (FMPSs) have been widely used in different areas including health monitoring, human–machine interaction and electronic skin for their good reliability, easy fabrication, and highly sensitive sensing performance. Although the use of a sensing layer with microstructure improves the sensor sensitivity, it also results in limited sensitive pressure range, slow response and poor cyclic stability, which prevents the sensors from being utilized in applications requiring wide detect range, real-time response and high durability. Here, we propose an advanced micro-structured sensing layer through doping thermally expandable microspheres into the screen-printing carbon black slurry to enhance its mechanical properties. An FMPS is then developed based on this enhanced micro-structured sensing layer. Benefiting from the expanded microsphere-like microstructure, the as-prepared sensor features high sensitivity (37.16 kPa−1), fast response/recovery time (126/52 ms), and good mechanical stability (over 3000 cycles). In addition, a home-made and effective collision avoidance system consisting of a robotic arm, the pressure sensor, a MEGA2560 microcontroller unit and a computer is constructed to indicate the sensor’s outstanding tactile perception characteristic, making it a promising candidate for intelligent robotic applications such as human–robot collaboration. Furthermore, we develop a pressure sensor array and demonstrate its ability to spatial pressure distribution perception. The developed microsphere-based pressure sensor and its array show great potential to be adopted in various monitoring and interactive applications such as humanoid robots, smart home, human–machine interaction, etc.

A grating lobes suppression method for a steerable parametric array loudspeaker

A parametric array loudspeaker (PAL) is a highly directional sound source with small aperture size. To achieve accurate sound projection, the steerable PAL is implemented by the use of the phased array technology. In this paper, the sound field model based on the Westervelt equation of a practical steerable PAL is presented, and a quasi-linear approximation is adopted to obtain the spatial sound pressure distribution. By applying the phased array technology, the audio beam can steer to the target direction. However, the grating lobe arises when the transducers are spaced more than half a wavelength, which disturbs the effect of beam steering. We further propose the grating lobes suppression method and apply it to the steerable PAL. Simulation results validate the performance of the proposed method.

Simulation of the Frequency Response Analysis of Gas Diffusion in Zeolites by Means of Computational Fluid Dynamics

Frequency response (FR) analysis allows the characterization of gas diffusion occurring within a porous solid system. The shape of the pressure response curves obtained after a volume modulation in the reactor gives essential information about the gas adsorption and desorption properties of the porous material, e.g., zeolites, which is in contact with a certain gas environment, as well as information about the transport phenomena such as diffusion. In this work, a simulation model developed in COMSOL Multiphysics® is introduced to reproduce the experimental behavior of the tested solid/gas systems. This approach covers, for the first time, a coupling of computational fluid dynamics (CFD), porous media flow, and a customized mass adsorption/desorption function to simulate the behavior of real frequency response systems. The simulation results are compared to experimental data obtained from the interaction of propane in MFI zeolites as well as additional data from the literature to evaluate the model validity. Furthermore, a small variation study of the effect of simulation parameters such as the mass of the sample, bed porosity, or geometry is performed and analyzed. The essential advantage of this model with respect to other analytical approaches is to observe the spatial pressure and adsorption distribution (along with other local effects) of the gas within the porous material. Thus, local environments can be visualized, and non-idealities can, therefore, be detected in contrast to the general integral simulation approach.

Wearable Capacitive Tactile Sensor Based on Porous Dielectric Composite of Polyurethane and Silver Nanowire.

In recent years, the implementation of wearable and biocompatible tactile sensing elements with sufficient response into healthcare, medical detection, and electronic skin/amputee prosthetics has been an intriguing but challenging quest. Here, we propose a flexible all-polyurethane capacitive tactile sensor that utilizes a salt crystal-templated porous elastomeric framework filling with silver nanowire as the composite dielectric material, sandwiched by a set of polyurethane films covering silver nanowire networks as electrodes. With the aids of these cubic air pores and conducting nanowires, the fabricated capacitive tactile sensor provides pronounced enhancement of both sensor compressibility and effective relative dielectric permittivity across a broad pressure regime (from a few Pa to tens of thousands of Pa). The fabricated silver nanowire-porous polyurethane sensor presents a sensitivity improvement of up to 4-60 times as compared to a flat polyurethane device. An ultrasmall external stimulus as light as 3 mg, equivalent to an applied pressure of ∼0.3 Pa, can also be clearly recognized. Our all-polyurethane capacitive tactile sensor based on a porous dielectric framework hybrid with conducting nanowire reveals versatile potential applications in physiological activity detection, arterial pulse monitoring, and spatial pressure distribution, paving the way for wearable electronics and artificial skin.

Analytical solution of electroosmotic-surcharge preloading coupled consolidation for unsaturated soil via Electric Prefabricated Vertical Drains (EVDs)

Electric prefabricated vertical drain made of new geosynthetic materials has the advantages of corrosion resistance, good water filtration, and unobstructed drainage. It has been used in unsaturated soils for embankment and slope stabilization as well as roadbed improvement. A theoretical model of the axisymmetric, free-strain consolidation for unsaturated soil under the coupled electrical-flow-mechanical fields considering radial-vertical flow is formulated, using the homogenization theory, method of separation of variables, and Bessel-Fourier series orthogonality. The relevant cases of saturated and unsaturated conditions are compared with the current analytical solution to examine the validity. The spatial and temporal distributions of excess pore-water and pore-air pressure are accurately reflected in the proposed solution, and its variation under electric fields is effectively displayed. The numerical calculations are also performed to investigate the effects of various important parameters, such as the single-layer unsaturated soil thickness, the effective voltage, and the radial water-to-electrical permeability ratio, on the excess pore-water pressure, excess pore-air pressure, and surface settlement. It is observed that the final negative pore-water pressure and the final settlement increase linearly as the effective voltage increases.

Methods for calculating aerodynamics inside high-speed railway tunnel lining cracks and predicating stress intensity factors

PurposeThis study aims to propose a series of numerical and surrogate models to investigate the aerodynamic pressure inside cracks in high-speed railway tunnel linings and to predict the stress intensity factors (SIFs) at the crack tip.Design/methodology/approachA computational fluid dynamics (CFD) model is used to calculate the aerodynamic pressure exerted on two cracked surfaces. The simulation uses the viscous unsteady κ-ε turbulence model. Using this CFD model, the spatial and temporal distribution of aerodynamic pressure inside longitudinal, oblique and circumferential cracks are analyzed. The mechanism behind the pressure variation in tunnel lining cracks is revealed by the air density field. Furthermore, a response surface model (RSM) is proposed to predict the maximum SIF at the crack tip of circumferential cracks and analyze its influential parameters.FindingsThe initial compression wave amplifies and oscillates in cracks in tunnel linings, resulting from an increase in air density at the crack front. The maximum pressure in the circumferential crack is 2.27 and 1.76 times higher than that in the longitudinal and oblique cracks, respectively. The RSM accurately predicts the SIF at the crack tip of circumferential cracks. The SIF at the crack tip is most affected by variations in train velocities, followed by the depth and length of the cracks.Originality/valueThe mechanism behind the variation of aerodynamic pressure in tunnel lining cracks is revealed. In addition, a reliable surrogate model is proposed to predict the mechanical response of the crack tip under aerodynamic pressures.