Pressure Field Measurements Research Articles

INFLUENCE OF VISUAL FIELD TESTING ON INTRAOCULAR PRESSURE IN PATIENTS WITH GLAUCOMA SUSPECTS ATTENDING TERTIARY CARE CENTER IN KATHMANDU

Background: The evaluation of glaucoma includes measurement of the intraocular pressure and Visual field. Both procedures frequently take place on the same appointment. A rise in intraocular pressure brought on by either internal or external sources could change the recommended course of treatment. The management of patients, therefore, benefits from understanding intraocular pressure changes and their implications. The goal of this study was to determine how visual field testing affected intraocular pressure in glaucoma suspects and glaucoma patients. Methods: The study’s cross-sectional design was carried out from October 15, 2020, to September 15, 2021, in a tertiary eye care facility. Intraocular pressure was measured before and after the visual field test. Data entry, as well as data analysis, was done on IBM SPSS 20. For comparisons of the intraocular pressure, the Wilcoxon signed-ranks test was used. A P ≤0.05 was considered statistically significant. Results: The Analysis of the data set showed no statistical significance difference between the intraocular pressures obtained before and after the test in each of the eyes and regarding the test duration Conclusions: Short-duration visual field testing did not significantly influence intraocular pressure, according to the study. This finding suggests that when clinically evaluating both the glaucoma patients and suspects, the visual field test may be done concurrently with the intraocular pressure measurement.

Application of Hardening State Parameter Constitutive Model for Prediction of Overconsolidated Soft Clay Behavior Due to Embankment Loading

This paper investigates the possibility of the application of the HArdening State Parameter (HASP) constitutive model for numerical modelling of overconsolidated soft clay under embankment loading. The HASP constitutive model is a critical state soil model with a combined hardening rule that uses a state parameter to determine the dilatancy of overconsolidated clay. The model overcomes some shortcomings of the Modified Cam Clay (MCC) model in the prediction of overconsolidated clay’s behavior, while preserving the simplicity and the same set of five parameters. The HASP model was implemented in finite element software. In order to verify the applicability of the model in predicting the behavior of soft overconsolidated clay due to embankment loading, two examples reported in the literature are analyzed. The numerical predictions of the HASP model are compared with the field measurements of ground settlements and pore water pressures, and with the MCC model’s predictions. The results indicate that the HASP model predicts the development of the settlements of the overconsolidated soft clay deposits with a high accuracy from an engineering point of view. There are certain deviations from the field measurements in predicting the pore pressure development, which is often observed for other models as well. For the embankment settlement assessment, as important serviceability issue, the HASP model has an advantage over more complex models that require a large number of parameters. Since the parameters of the HASP model are obtained from standard laboratory tests, it can be easily applied for routine geotechnical analyses.

Experimental and numerical study of reverse power generation in coastal axial flow pump system using coastal water

Coastal areas require frequent drainage to prevent waterlogging, and are often equipped with axial flow pump systems to enable this. Reverse power generation from CAPS (coastal axial flow pump systems) using coastal water is an untapped but high-potential source of renewable energy. However, the design of CAPS usually considers only the pumping conditions; there isa huge difference in flow during the reverse power generation condition (TC) and the conventional pumping condition (PC). If such a CAPS were to operate under TC, there would be unknown risks to its hydraulic performance and operational stability. In this study a special experimental test bench is built for the evaluation of CAPS. Energy test and measurement of internal pressure field are carried out for TC and PC of CAPS under full flow condition. Then, the energy loss characteristics and the propagation law of CAPS under PC and TC are investigated by an unsteady numerical simulation, and the results of the simulation are compared with the experimental results. The flow field difference between the PC and TC is analyzed in detail, and the hydraulic performance, operation safety, and stability of CAPS under TC are evaluated. This paper is expected to be of reference value for the renewable utilization of low-head water resources in coastal areas.

Investigation on favorable pressure gradient in an atmospheric boundary layer wind tunnel using large‐eddy simulation and its impact on wind field and surface pressure measurement

AbstractA constant cross‐section wind tunnel usually experiences a negative pressure gradient (ie, favorable pressure gradient, FPG), resulting in a certain degree of discrepancy between the simulated and idealized atmospheric boundary layer (ABL) flows. To investigate its impact, three large‐eddy simulation (LES) cases were conducted in this study: one simply reproduced a wind tunnel, one removed the FPG by adjusting the ceiling height, and one reduced the FPG by canceling unnecessary boundary layers associated with the tunnel sidewalls and ceiling. The required ceiling height in the second case was estimated based on the pressure gradient in the first case. The FPG was found mainly generated by the contraction effect induced by the boundary layers over the tunnel walls because it can be largely removed in the third case. In addition, we investigated the mean and standard deviation of the surrounding wind field and surface pressure coefficient of an isolated square‐section building model. Because the FPG in the macroscale ABL is negligible compared with the adverse pressure gradient in the microscale near‐wall boundary layers of the building, the influence of the FPG is negligible in a wind tunnel experiment conducted in a relatively large wind tunnel with a safe blockage ratio.

Evaluation of Air Conditioner Performance using Different Methods of Temperature Measurement

Performance evaluation of an air conditioner using R410a has been evaluated by field measurement of pressure and temperature at suction and discharge line. Two methods were used for temperature measurement. First, the sensors were mounted on the outer wall of pipe and second, the sensors were inserted into the refrigerant flow in the pipe. Using the second method, the suction temperature is averagely 5.0°C lower and the discharge temperature is 17.8°C higher than that of the first method. The coefficient of performance and power consumption resulted from the second method is in a good agreement with that of standardized test according to ISO 5151:2017. This indicates that the temperature sensor insertion to the refrigerant flow gives the better accuracy in the evaluation of performance of an air conditioner.

Pressure Measurement of Coal Seam with Active Nitrogen Injection: Model and Experimental Analysis.

Coal seam gas pressure is the core index of coal mine gas disaster prevention and control. Research on active nitrogen injection pressure measurement can effectively shorten the pressure measurement time and is of great significance to improve the pressure measurement efficiency. The purpose of this paper is to study the variation in gas pressure in the process of active nitrogen injection and the influence of different gas injection pressures on pressure measurement. Through the design of active pressure test device, pressure measurement experiments with different nitrogen injection pressures were carried out. The multicomponent gas migration model of active pressure measurement was constructed, and the active pressure numerical solver was developed based on OpenFOAM and C++ language. The borehole gas pressure equation was verified by field pressure data. The results show that when the injected nitrogen pressure is closer to the original coal seam gas pressure, the borehole gas pressure balance time is shorter. The gas change rate in this process depends on the pressure difference and concentration difference between the borehole and the surrounding coal. When the nitrogen injection pressure is greater than the gas pressure around the borehole, N2 will percolate, diffuse, and adsorb into the coal. In contrast, it is dominated by the desorption, diffusion, and seepage of CH4 to the borehole. The correlation coefficient R 2 between the borehole gas pressure equation and the field pressure measurement data is more than 0.88. Therefore, the equation can verify the reliability of the measurement results of active gas injection pressure in the field. The research results provide a reference for further understanding the mechanism and application of pressure measurement in coal seam injected with active nitrogen.

Bayesian inference of axisymmetric plasma equilibrium

We present a Bayesian method for inferring axisymmetric plasma equilibria from the magnetic field and plasma pressure measurements. The method calculates all possible solutions for plasma current and pressure distributions consistent with the measurements and magnetohydrodynamic (MHD) force balance. Toroidal plasma current and magnetic field coils are modelled as a set of axisymmetric current-carrying solid beams. The other parameters such as plasma pressure and poloidal current flux are given as a function of poloidal magnetic flux, which is determined given a 2D current distribution. Plasma pressure and poloidal current flux profiles are modelled as Gaussian processes whose smoothness is optimally chosen based on the principle of Occam’s razor. To find equilibrium solutions, we introduce an MHD force balance constraint at every plasma current beam as a part of the prior knowledge. Given all these physical quantities, predictions calculated by the predictive (forward) models for diagnostics are compared to the observations. The high dimensional complex posterior probability distribution is explored by a new algorithm based on the Gibbs sampling scheme.

Background-oriented schlieren technique with vector tomography for measurement of axisymmetric pressure fields of laser-induced underwater shock waves

This study aims to overcome the problems that existing background-oriented schlieren (BOS) techniques based on computed tomography (CT-BOS) face when measuring pressure fields of laser-induced underwater shock waves. To do this, it proposes a novel BOS technique based on vector tomography (VT-BOS) of an axisymmetric target. The remarkable feature of the proposed technique is the reconstruction of an axisymmetric vector field with nonzero divergence, such as the field of a laser-induced underwater shock wave. This approach is based on an approximate relation between the projection of the axisymmetric vector field and the reconstructed vector field. For comparison, the pressure fields of underwater shock waves are measured with VT-BOS, CT-BOS, and a needle hydrophone. It is found that VT-BOS is significantly better than CT-BOS in terms of better convergence, less dependence on the spatial resolution of the acquired images, and lower computational cost. The proposed technique can be applied not only to fluid dynamical fields, but also to other axisymmetric targets in other areas, such as electromagnetics and thermodynamics.Graphical abstract

Research on the Application of Foamed Lightweight Concrete (FLC) in the Construction of Highway Soft Soil Foundation Engineering with Buried High-Pressure Gas Pipes

In order to study the feasibility and superiority of foam lightweight concrete (FLC) for existing buried high-pressure gas pipeline section under soft soil roadbed, this paper takes the buried existing high-pressure gas pipeline section under the second phase of the Foqingcong Expressway project as the engineering background, and designs two soft soil roadbed treatment schemes, the pile composite foundation method, and the foam lightweight concrete (FLC). Through bearing capacity and settlement calculations, it was confirmed that FLC is feasible for soft soil roadbeds in the existing buried high-pressure gas pipe section, and the three major aspects of analysis, namely the safety benefits, economic benefits and ecological benefits based on the LCA carbon emission calculation, showed that the FLC soft soil roadbed treatment method can reduce the cost by 12% compared with the pile composite foundation treatment method, which is about 1.07 million RMB, and the carbon emission is reduced by about one third. This is a clear benefit advantage. Finally, the feasibility of FLC for buried high-pressure gas pipe sections under both soft soil roadbeds was further verified by field measurements of settlement and earth pressure, which has broad application prospects.

Comparative study between field measurements of wind pressures on a 600-m-high skyscraper during Super Typhoon Mangkhut and wind tunnel test

Wind pressures on cladding of a 600-m-high skyscraper during Super Typhoon Mangkhut were monitored by a synchronous monitoring system including 48 pressure transducers. Then, simultaneous wind pressure measurements on a 1:500 scale model of the skyscraper were conducted in wind tunnel test. The field measurements of wind pressures are further analyzed to investigate the wind pressure characteristics on the skyscraper under extreme windstorm condition and utilized to validate the wind tunnel test results. The full-scale and model-scale wind pressure coefficients (mean, root mean square, maximum and minimum) are compared with each other and analyzed in detail. Moreover, to explore the deviations between the full-scale and model-scale results, the Reynolds number effect (5.5 × 104 to 1.8 × 108) on the wind pressure coefficients, probability distributions, power spectral densities, spatial correlations and coherences of wind pressures are investigated. The comparative study shows that the wind tunnel test can reproduce the wind pressures on the windward face. While for the other faces, the results from the wind tunnel test generally deviate from those from the field measurements. The reasons that caused the discrepancies, especially the Reynolds number effect, are discussed. The objectives of this paper are to examine the accuracy of wind tunnel testing for predicting wind pressures on high-rise buildings under severe wind condition and enhance the understanding of wind pressures on high-rise buildings during strong windstorms, and therefore provide useful information for the wind-resistant design of skyscrapers.

Discrimination Method of Gas Pressure Measurement in Coal Seams: Physical Experiment and Model Development.

Coal seam gas pressure is a key parameter of gas accident control and gas drainage. At present, there are some problems in field pressure measurement, such as long period, and there is often a need to drill more holes to ensure the reliability of pressure measurement. In this research, a physical gas pressure measurement experiment in a coal sample borehole was carried out, and a mathematical model of gas pressure evolution with time was constructed. Based on the OpenFOAM platform and C++ language, a numerical solver was developed, and the mathematical model was verified by the data of gas pressure in coal seam boreholes. The results show that the evolution process of gas pressure in coal seam boreholes can be divided into two stages. In the first stage, the gas pressure increases rapidly, and the pressure change rate decreases continuously. In the second stage, the gas pressure is slow and stable, and the pressure change rate tends to 0. The correlation coefficients between the mathematical model and the field-measured data are more than 0.94, and the calculation and prediction accuracy are high. Therefore, the model can be used to verify the field data during pressure measurement, which has better field significance and application value.

Mechanism of hysteresis and uncontrolled deflection in jet vectoring control based on Coanda effect

We investigated the mechanism of hysteresis and uncontrolled deflection in jet vectoring control based on the Coanda effect. Thrust vectoring control based on the Coanda effect is highly applicable in the field of fluid dynamics because they can achieve jet deflection control with a simple geometric structure and low energy consumption. However, the hysteresis and uncontrolled deflection phenomena considerably hinder the practical application of these technologies. We designed a new passive fluidic thrust vectoring control model to analyze the mechanism of these disadvantages. We developed a synchronous pressure, force, and flow field measurement system to investigate the evolutions of flow structures and their effects on wall pressure distribution and vectoring force. The characteristics of the key flow structures, including the separation bubble, the secondary flow, and the backflow, were investigated. The transient features of jet attachment and jet detachment were researched to identify the transition of near-wall flow structures and wall pressure distribution during jet uncontrolled deflection. The mechanism of uncontrolled deflection is that the formation/breakdown of the separation bubble changes the flow state of the backflow, and the near-wall mass flux balance is collapsed. This causes a dramatic change in the jet vectoring angle, which is out of the valve's control. During attachment, the shear layer first touches the wall and forms a separation bubble, and then, the bubble shrinks. During detachment, the bubble first enlarges and then breaks down. Therefore, the formation and breakdown of the separation bubble correspond to different valve positions, which is the mechanism of hysteresis.

Time-resolved multi-parameter flow diagnostics by filtered Rayleigh scattering: system design through multi-objective optimisation

The measurement of the time-resolved three-component (3C) velocity field together with scalar flow quantities such as temperature or pressure by laser-optical diagnostics is a challenging task. Current approaches usually employ combinations of different methods relying on tracer particles or molecules. This typically requires usage of at least two laser systems and detection units as well as elaborate calibration of the luminous properties of the applied tracer species with regard to the specific thermodynamic conditions anticipated for the flow case at hand. In contrast to this, the tracer-free filtered Rayleigh scattering (FRS) technique has been proven to obtain combined time-averaged velocity and scalar fields and might offer a viable alternative for unsteady flow diagnostics. By applying multiple perspective views, two detection system variants are presented, combining (1) six observation branches with one camera/molecular filter and (2) three camera views with two cameras and molecular filters of differing vapour densities. Both configurations in principle allow for the simultaneous measurement of instantaneous 3C velocity, temperature and pressure fields. Multi-objective optimisation is used to enhance the detection setups for different sets of experimental configurations. It is shown that a higher number of observation positions and the associated dynamics of the FRS signal prove to be advantageous compared to the use of less views in combination with two acquisition channels equipped with different molecular filters. It is also shown that the use of circularly polarised laser light offers no advantage over linear polarisation. By demonstrating a moderate sensitivity of the optimised observation arrangement to alignment errors, the presented FRS concept provides a practical solution for the simultaneous measurement of time-resolved 3C flow velocity and scalar fields.

Unsteady Multi-Parameter Flow Diagnostics By Filtered Rayleigh Scattering: System Design By Multi-Objective Optimisation

The measurement of the time-resolved three-component (3C) velocity field together with scalar flow quantities such as temperature or pressure by laser-optical diagnostics is a challenging task. Current approaches typically employ combinations of different methods relying on tracer particles or molecules, which requires elaborate calibration procedures of the tracer's photo-physical properties and extensive instrumentation. In contrast to this, the tracer-free filtered Rayleigh scattering (FRS) technique has been proven to obtain combined time-averaged velocity and scalar fields and might offer a viable alternative for unsteady flow diagnostics. By applying multiple perspective views, two detection system variants are presented, combining 1) six observation branches with one camera/molecular filter and 2) four camera views with two cameras and molecular filters of differing vapour densities. Both configurations in principle allow for the simultaneous measurement of instantaneous 3C velocity, temperature and pressure fields. Multi-objective optimisation is used to enhance the detection setups for different sets of experimental configurations. It is shown that a higher number of observation positions and the associated dynamics of the FRS signal prove to be advantageous compared to the use of less views in combination with two acquisition channels equipped with different molecular filters. It is also demonstrated that the use of linearly polarised laser light is preferred over circular polarisation. Future work will focus on the realisation of the multiple-view FRS concept for the combined measurement of 3C velocity and scalar fields.

Development of a wireless, non-intrusive, MEMS-based pressure and acoustic measurement system for large-scale operating wind turbine blades

Abstract. As the wind energy industry is maturing and wind turbines are becoming larger, there is an increasing need for cost-effective monitoring and data analysis solutions to understand the complex aerodynamic and acoustic behaviour of the flexible blades. Published measurements on operating rotor blades in real conditions are very scarce due to the complexity of the installation and use of measurement systems. However, recent developments in electronics, wireless communication and MEMS (micro-electromechanical systems) sensors are making it possible to acquire data in a cost-effective and energy-efficient way. In this work, therefore, a cost-effective MEMS-based aerodynamic and acoustic wireless measurement system that is thin, non-intrusive, easy to install, low power and self-sustaining is designed and tested in a wind tunnel. The measurement system does not require an electrical connection to the wind turbine and can be mounted and removed without damaging the blade.The results show that the system is capable of delivering relevant results continuously, although work needs to be done on calibrating and correcting the pressure signals as well as on refining the concept for the attachment sleeve for weather protection in the field. Finally, two methods for using the measurements to provide added value to the wind energy industry are developed and demonstrated: (1) inferring the local angle of attack via stagnation point detection using differential pressure sensors near the leading edge and (2) detecting and classifying leading edge erosion using instantaneous snapshots of the measured pressure fields. Ongoing work involves field tests on a 6 kW operating wind turbine in Switzerland.

THM-coupled numerical analysis of temperature and groundwater level in-situ measurements in artificial ground freezing

Belarusian Potash salt deposits are bedded under aquifers and unstable soil stratums. Therefore, to develop the deposits a vertical mine shaft sinking is performed using the artificial ground freezing technology. Nowadays, real time observations of ground temperature and groundwater level is applied to control the ground freezing process. Numerical simulation can be used for a comprehensive analysis of measurements results. In this paper a thermo-hydro-mechanical model of freezing of water saturated soil is proposed. The governing equations of the model are based on balance laws for mass, energy and momentum for a fully saturated porous media. Clausius-Clayperon equation and poroelastic constitutive relations are adopted for description of a coupled change in water and ice pore pressure, porosity and a stress-strain state of freezing soil. The proposed model enables us to describe evolution of equivalent water content measured in Mizoguchi’s test and predict frost heave strain in one-sided freezing test. Numerical simulation of ground freezing in the Petrikov mining complex located in Belarus has shown that the model is able to describe field measurements of pore pressure inside a forming frozen wall. Furthermore, the mismatch between hydro- and thermo-monitoring data obtained during the artificial freezing is analyzed.

Numerical investigation of the unsteady distortion for an S-duct intake with mechanical vortex generators

Flow control devices are used within complex intakes to reduce the flow distortion which can adversely impact the stability and performance of embedded engines. There is a need to assess the capability of modern computational methods such as detached eddy based models to compute the unsteady flowfield and to evaluate the potential benefits of flow control devices on the unsteady distortion. This paper investigates the unsteady flowfield for an S-duct using Zonal Detached Eddy Simulations (ZDES) with passive flow control devices modelled with an overlapping Chimera grid method. The ability of ZDES to evaluate the impact of passive flow control devices on the unsteady flow distortion was assessed. The computed unsteady flowfield at the Aerodynamic Interface Plane was compared with experimental data based on total pressure and velocity field measurements. For the baseline configuration, the ZDES model has proven to be able to simulate the unsteady flowfield at the AIP, to provide the time averaged and fluctuating levels of swirl distortion within 1% and 13% respectively of the measurements. The strong impact of the flow control devices on the AIP flowfield was also captured by the ZDES. The overall increase of pressure ratio (PR) at the AIP due to the flow control devices was predicted with less than 1% error. The 65% reduction in swirl distortion fluctuation when the flow control devices are used was predicted within less than 8% error by the ZDES compared with S-PIV measurements. Overall it was determined that the ZDES method is able to simulate the unsteady flow and distortion characteristics for both the baseline reference configuration as well as the case with flow control.

Pressure field measurements on large-scale propeller blades using pressure-sensitive paint

Pressure field measurements on large-scale propeller blades using pressure-sensitive paint

Segmented ROSI method: Beamforming method for investigating turbomachinery noise sources along segmented trajectories

The rotating source identifier (ROSI) beamforming method is a method designed for localizing rotating noise sources in a uniform flow based on out-of-flow acoustic pressure field measurement data. It has been developed for sources moving along a circular trajectory, such as turbomachinery blades. The original ROSI method processes the measured acoustic signals over a long time segment to reconstruct the noise sources, providing time-averaged results for each noise source. By doing so, it does not take into consideration certain features of the noise sources, such as the directivity of the trailing edge and leading-edge noise sources. A further development of the ROSI method is presented herein, which separates the sound-pressure signal of one revolution into multiple segments. In this way, the beamforming maps can provide one with a better understanding of the differences between the noise sources as a function of angular position. This method will be referred to herein as the segmented ROSI method. The goal of this further development is to improve the capability of the method in identifying the position-dependent modulations of the various noise sources as they are moving along their trajectories, rotating around the axis. The investigation presents the theory behind the new segmented ROSI method along with simulation and measurement-based test cases which help in comparing the new method to the original ROSI method. The results show that the novel method provides a strong tool for investigating turbomachinery noise sources that vary along segments of their trajectories. It is therefore expected that the tool will be useful in cases that look at turbomachinery from an angle and cases where the loading of the blades changes as a function of angular position.

Improving Carbonate Equilibria-Based Estimation of pCO2 in Anthropogenically Impacted River Systems

Estimating riverine carbon dioxide (CO2) emissions has been constrained by lacking field measurements of the partial pressure of CO2 (pCO2) and inaccuracies in calculating pCO2 using carbonate equilibria-based models such as CO2SYS. To evaluate potential errors in applying the carbonate equilibria-based pCO2 calculation to river systems affected by monsoon rainfall and water pollution, we compared pCO2 values calculated using CO2SYS and those measured by headspace equilibration in five Asian rivers (Ganges, Mekong, Yangtze, Yellow, and Han rivers) undergoing various water pollution stages. Across the five rivers, calculated and measured pCO2 values exhibited larger discrepancies during the monsoon season, particularly in the low pH range, while in the Han River mismatches were also noticeable during the dry season. In the Han River, pH was negatively correlated with dissolved organic carbon (DOC) during the monsoon, indicating organic acids flushed from soils during rainfalls as a key factor for overestimated pCO2 at sites with low pH and alkalinity, whereas dry-season overestimation of pCO2 may be ascribed to non-carbonate alkalinity including organic acids and inorganic anions delivered by wastewater effluents or sporadic rainfalls. The four large rivers exhibited a positive correlation between pH and DOC in tributaries during the monsoon season, indicating that DOC flushed from soils may be diluted by monsoonal floods to such a degree as to exert little influence on pH and hence pCO2. Therefore, the monsoonal overestimation of pCO2 at sites with low pH and alkalinity warrants further investigation of other factors than non-carbonate alkalinity to explain the increased sensitivity of pCO2 to subtle changes in acidity and buffering. These results illustrate the importance of direct measurements of pCO2 in highly polluted rivers, especially during the monsoon season. For river systems lacking pCO2 measurements, we suggest that carbonate equilibria-based models be complemented with corrective measures: 1) presenting pCO2 values calculated from low pH values (pH < 6.5 for monsoon and pH < 6.3 for dry season) together with the pH range to warn potential overestimation; 2) using pre-established regressions between measured pCO2 and environmental variables to correct pCO2 values, particularly during wet periods when large changes in pH and acid buffering are expected.