Pressure Fluctuations Research Articles

Comparison of measured and LES-predicted wind pressures on the Space Needle

The majority of wind damage is to building envelope components. Large eddy simulations (LESs), which can predict flow fields at high resolution, have significant potential for analyzing component loads. This study aims to (1) demonstrate that LESs can elucidate flow phenomena behind peak pressure loads, and (2) quantitatively compare LESs to full-scale measurements performed on the roof of the 184 m tall Space Needle. The simulations revealed unsteady flow features responsible for pressure signals observed in separation regions and shear layers. Furthermore, predictions for fluctuation pressure coefficients were quantitatively representative of field data. The main discrepancy observed was a more pronounced variability of measured, compared to simulated, shear layer peak pressures. Detailed measurements of the incoming wind field would be needed to further investigate this discrepancy. The results demonstrate the value of joint field measurements and LESs for studying wind effects.

PH-Optimized Biomethane Production: Evaluating Carrier Materials for Ex-situ Biomethanation

Choosing the appropriate carrier material for ex-situ biomethanation is a critical factor to consider when developing biogas upgrading technologies. The chosen material for biomethanation in a biotrickling filter reactor functions as a substrate that immobilises microorganisms, which act as catalysts in the reaction for producing biomethane. This study conducted experiments on waste-derived materials, including glass foam and vulcanised wood ash material, in addition to polyurethane foam and expanded clay pellets. Pretreratment of wood ash was done to lower the pH of material. The manometric test measured the rate of CH4 generation by quantifying pressure fluctuations. The validity of these results was confirmed by analysing product gas samples using a Shimadzu Nexis GC-2030 gas chromatograph, which was equipped with two parallel lines, a flame ionisation detector (FID) and a thermal conductivity detector (TCD). In order to enhance the biomethane concentration in the end product, two strains of Methanobacterium alcaliphilum were evaluated alongside biogas sludge as the inoculum. These strains of microorganisms are methanogens that utilise hydrogen and can thrive in a high pH environment. Thus, they have the potential to demonstrate improved biomethane production outcomes when a vulcanised wood ash filter is used as the carrier material.

Interior noise prediction of inter-coach space of high-speed maglev trains based on wavenumber decomposition on aerodynamic excitation

Current research on noise and vibration control of high-speed maglev trains pays more attention to far-field noise, while the level of interior noise has a direct impact on the ride comfort and should be placed equal weight on. In this paper, inter-coach space, one of the main pressure fluctuation sources of a specific type of high-speed maglev train with a design speed of 600 km·h−1, is taken as the research object. The turbulent and acoustic components of wall pressure fluctuations (WPF) are separated based on a wavenumber-frequency analysis approach, and then each component is applied as different forms of source input to the vibroacoustic model, namely, finite element method-boundary element method (FEM-BEM) and statistical energy analysis (SEA) for low- and high-frequency ranges respectively, to investigate the contribution of both components to interior acoustic cavity in all frequency range. It can be seen quantitatively from the results that the amplitude of turbulent component is generally much higher than that of the acoustic one, but it can be vice versa when it comes to the interior response. The conclusion drawn in this paper are able to provide guidance for future researches on more targeted interior noise control of high-speed maglev trains.

Analysis of Shield Tunneling Parameters and Research on Prediction Model of Tunneling Excavation Speed in Volcanic Ash Strata of Jakarta–Bandung High-Speed Railway Project

Insufficient investigations have been conducted on the analysis of shield tunneling parameters and the prediction of the tunneling excavation speed in formations composed of volcanic ash strata. To address this issue, we employ a comprehensive approach utilizing literature research, mathematical statistics, and other methodologies, centered on the analysis of the No. 1 Tunnel of the Jakarta–Bandung High-Speed Railway. Our focus is on examining the evolution patterns and inter-relationships of shield tunneling parameters within volcanic ash strata. Subsequently, we propose an optimized strategy for these tunneling parameters. By employing six machine-learning algorithms to construct prediction models, we compare and analyze their performance in predicting the tunneling excavation speed. The results indicate a positive correlation between slurry pressure and tunnel depth in volcanic ash strata, suggesting that the grouting pressure should exceed the slurry pressure by approximately 0.22 MPa. In the composite stratum of “volcanic ash debris + round gravel”, the cutter torque exhibits a strong negative correlation with the total thrust (−0.77). Due to tool wear and ground resistance, the excavation speed and cutter speed are weakly negatively correlated. Compared to other strata, shield tunneling in volcanic ash strata exhibits larger grouting pressure fluctuations, slower tunneling excavation speed, greater total thrust, higher cutter torque, and lower cutter speed. Regarding shield tunneling excavation speed prediction, the ranking of the algorithm performance is RF > DNN > ANN > BPNN > MNR > SVM, with RF achieving a decision coefficient of 0.829. The RF model is well-suited for predicting the shield structure tunneling excavation speed.

Hybrid method for hydraulic transient analysis of liquid pipe networks based on characteristic lines and equivalent circuits

Water hammer poses a significant concern in the transportation of pipelines and pipe networks. Due to the passage of reflection of water hammer waves at nodes, a large number of high-frequency pressure fluctuation signals appear in the pipe network, demanding an intensive computational workload. A novel hybrid method based on characteristic lines and equivalent circuits is proposed for the accurate and fast simulation of pipe networks. Multiple methods are employed for the simulation of pipelines and pipe networks, followed by a comparative analysis. The accuracy of the hybrid method is validated by comparing the proposed method with simulation results of commercial software. The hybrid method reduces the significant computational workload inherent in the classic method of characteristics and enhances the accuracy at high frequencies in the state-of-the-art elastic water column model. A trade-off between simulation accuracy and computation speed is achieved by adjusting the time step. The accuracy of calculating higher-frequency pressure fluctuations is further validated with an increase in the pipe diameter and a corresponding reduction in the friction loss. Generally, this method enables the simultaneous descriptions of high-frequency characteristics and nonlinear friction loss, enhancing calculation speed with little impact on the accuracy. The results demonstrate that the proposed model can be utilized for the transient analysis of pipe networks, providing support for predicting system performance and designing optimal strategies.

The impact of whole-process visualization collaborative nursing discussions education on perioperative symptoms and emotional well-being in radical prostatectomy patients.

Prostate cancer is one of the most common malignant neoplasms in elderly males, with radical prostatectomy being the established therapeutic approach for localized disease. Patients undergoing this surgical procedure frequently experience increased negative emotions and symptomatology during the perioperative period, likely due to concerns about the illness and its treatment. The present study aims to investigate the effects of a novel educational approach involving a whole-process visualization and collaborative nursing discussions on perioperative symptoms and emotional well-being in radical prostatectomy patients. Data were prospectively collected from 310 patients admitted to the hospital between June 2021 and December 2023, all of whom were scheduled to undergo radical prostatectomy. These patients were randomly assigned to either the intervention group (receiving new model education) or the control group (receiving conventional education), with 155 patients in each group. The study compared basic demographic information, anxiety and depression scores, fear of disease progression scores, quality-of-life scores, main symptom scores, and changes in perioperative vital signs between the two groups. No statistically significant differences were observed between the two groups in terms of age, comorbidities, insurance type, education level, income, and tumor history (P > 0.05). Similarly, there were no significant differences in anxiety and depression scores, proportion of patients with anxiety and depression, vital signs, and fear of disease progression scores between the two groups at Time 1 stage (P > 0.05). During stages Time 2 and Time 3, the intervention group exhibited lower anxiety and depression scores, a lower proportion of anxious and depressed patients, as well as significantly reduced blood pressure and heart rate fluctuations compared to the control group (P < 0.05). Following radical prostatectomy, the main symptoms of patients, such as pain, nausea, and fatigue, were assessed using the MADIS Symptom Assessment Scale on days 1-3 post-surgery. The intervention group exhibited significantly lower scores for three symptoms compared to the control group (P < 0.05); at Time 4 stage, the patients in the intervention group also demonstrated significantly improved quality-of-life scores compared to the control group (P < 0.05). Additionally, blood pressure and heart rate of patients returned to baseline levels at Time 4 stage, with no significant difference between the two groups (P > 0.05). Nevertheless, the anxiety and depression scores in the intervention group at the Time 4 stage remained significantly lower than those in the control group (P < 0.05). Additionally, the fear of disease progression scores in both groups were lower than those at the Time 1 stage, with a more pronounced improvement observed in the intervention group compared to the control group (P < 0.05). Patients diagnosed with malignant tumors often experience fear and anxiety regarding the progression of their disease and upcoming surgery, as well as uncertainty surrounding their treatment and prognosis. This heightened emotional distress can contribute to a greater symptom burden during the perioperative period. Utilizing a whole-process visualization and collaborative nursing discussion approach, as compared to traditional communication methods, has been shown to alleviate patients' fears, reduce anxiety and depression, and ultimately lessen the symptom burden experienced during the perioperative phase. Ultimately, this approach can enhance the overall quality of life for patients facing malignant tumors.

Qualitative assessment of optimizing the well spacings based on the economic analysis

The design of well spacing significantly influences the sustainability and economic benefit of geothermal energy extraction. However, most studies have predominantly employed heat production-related parameters as indicators of well spacing, and a comprehensive analysis of well spacing design based on an economic model is necessary for practical implementation. In this study, an economic indicator considering the benefits derived from heat production and operating costs is proposed and applied in the Caofeidian, a typical abandoned oilfield in the Bohai Bay Basin. It offers a refined portrayal of directional wells, moving beyond rudimentary representations, to capture their appropriate degree of complexity and behavior in drilling configurations. First, by integrating thermophysical information and site investigation data from previous oil investigations, a heterogeneous 3D model is constructed to forecast the 30-year temperature and pressure evolution. Then, a modified levelized cost of heat (LCOH-HT) is proposed to perform economic analysis in optimizing the well spacing, revealing an optimal range of 300–600 m for the different selected wells. In comparison with results derived solely from heat production considerations, drilling and pumping costs contribute to a 300 m reduction in the optimal well spacing based on the proposed approach, as a larger well spacing leads to increased hydraulic losses and drilling cost, necessitating greater pumping efforts and costs. This finding underscores the need to balance economic and thermal considerations. In addition, we found the difference in the optimal well spacing in space is also caused by the porosity variations. Porosity affects fluid temperature and pressure, leading to changes in the benefits and costs associated with pressure fluctuations. Notably, this novel economic analysis method is not limited to spacing optimization; it can also be used to optimize operating parameters, such as the flow rate, which could provide practical strategies for geothermal energy extraction.

Dynamic characterization of water hammer in gangue fly ash slurry pipelines during valve closure

In the process of coal-filling mining, the gangue fly-ash slurry (GFS) needs to be transported over a long distance to reach the gobs. The abrupt closure of the valve during the transportation of GFS can result in a water hammer that significantly endangers the stability and safety of the pipeline transport system. To study the fluctuations in pressure induced by abrupt closure of the valve, experiments on the rheological parameters of gangue-coal ash slurry were conducted. Transient numerical simulations were carried out using the computational fluid dynamics method for various valve closing times. The results indicate that, with the increase of slurry concentration, the yield stress of the slurry significantly increases. When the concentration exceeds 76%, the increase in yield stress reaches 38.4% and 35.1%, respectively. Upon valve closure, the internal pressure of the slurry in the pipeline exhibits periodic dynamic oscillations. As the duration of valve closure increases, the frequency of periodic water hammer events decreases. The maximum water hammer pressure caused by valve closure decreases with the increasing distance between the valve and the closure point. At the same time, the intensity of maximum water hammer pressure fluctuations increases with the increase in slurry concentration and flow velocity in the pipeline. The results can provide references for water hammer protection and pipeline selection during the transportation of backfill slurry in mining.

The Measured Flow at the Inlet of a Francis Turbine Runner Operating in Speed No-Load Condition

Abstract For Francis turbines, speed-no-load (SNL) represents one of the most detrimental operating conditions, marked by significant pressure and strain fluctuations on the runner. Mitigating these fluctuations necessitates a comprehensive understanding and characterization of the flow phenomena responsible for their generation. This paper presents an experimental investigation of the flow at the inlet of a Francis turbine runner model operating in speed-no-load condition using high-speed stereoscopic and endoscopic particle image velocimetry (PIV). The measurements are made in a radial-azimuthal plane that covers the vaneless space and a large region in the interblade channel. This study marks the first-time measurement of critical flow phenomena at this operating point, performed in the runner. Instantaneous and average velocity fields are analyzed, along with other statistical data. The results not only confirm the stochastic nature of the flow at speed-no-load but also highlight the general structure of the flow observed in other studies. The high velocity fluctuations on the suction side are associated with a backflow extending into the vaneless space and a circulation zone occasionally generated by this backflow. Both phenomena are frequently present, but fluctuate stochastically. Additionally, two other circulation zones intermittently form on the pressure side of the blades. The presence of vortices, smaller than the circulation zones, near the blade's leading edge correlates with the backflow intensity.

Impact of Ultrafiltration Profiling Compared to Conventional Methods on Blood Pressure Regulation Among Hemodialysis Patients

Background: Standard hemodialysis sessions pose challenges for patients due to fluctuations in blood pressure. Alternative strategies, such as ultrafiltration profiling, have been proposed as potentially more effective treatments. Objectives: This study aimed to evaluate the effects of ultrafiltration profiling compared to the conventional method on blood pressure regulation among hemodialysis patients. Methods: This study employed a pre-test and post-test design, involving a single group of 30 hemodialysis patients undergoing treatment at Shahid Beheshti Hospital in Hamadan in 2022. The sampling method used was simple random sampling. The intervention consisted of three sessions using the routine method, followed by three sessions utilizing the ultrafiltration profile method, which employed an interval with a negative slope. Demographic and clinical information about the patients was recorded on a checklist. Systolic and diastolic blood pressure measurements were taken before the commencement of hemodialysis, at 1-, 2-, and 3-hour intervals post-treatment initiation, and again 15 minutes after completing hemodialysis. Results: The mean blood pressure changes observed during dialysis stages increased with both methods; however, there was a significant difference between the methods (P &lt; 0.001). Specifically, patients receiving the ultrafiltration profile method experienced significantly lower increases in blood pressure compared to those receiving the routine method. Conclusions: Based on the research results, integrating ultrafiltration profiling into hemodialysis can be regarded as an effective and viable strategy for enhancing blood pressure regulation in patients undergoing hemodialysis treatment. Therefore, it is recommended that this approach be considered in hemodialysis programs as well.

Numerical Study On the Effect of Channel Configuration On Mixture Formation of an Axial Flow Wave Rotor Combustor

Abstract Wave rotor combustor technology is a new technical means to improve the thermal efficiency of aero-engine by using unsteady flow and constant volume combustion. In this article, the influence of wave rotor combustor channel structure on the mixture formation in the channel was studied by numerical simulation. The results showed that the internal flow field structure and change of any structure channel are similar. Flow separation will occur in all channels, and wake regions will be formed in the channels. The turbulence kinetic energy in the wake region was increased, and the velocity and pressure were decreased, resulted in the vortex in the channel. When the channel width was reduced to half of the original design, the Relative Standard Deviation (RSD) of the mixture was reduced by at least 54.92% compared to the original design, and the global fuel mass fraction in the channel was increased by at least 27.32%. In addition, the fluctuation of discharge pressure was also reduced. The reduction of the channel height does not lead to a significant improvement in the aforementioned results. This study can provide guidance for the structural design of wave rotor combustor channel.

Investigation of Non-Uniform Inflow Effects on Impeller Forces in Axial-Flow Pumps Operating as Turbines

Due to the existence of an inlet elbow, transmission shaft, and other structural components, the inflow of axial-flow pumps as turbines (PATs) becomes non-uniform, resulting in the complexity of internal flow and adverse effects such as structural vibration. In this paper, numerical methods were employed to explore the non-uniform inflow effects on impeller forces and internal flow field characteristics within an axial-flow PAT. The study results indicated that non-uniform inflow caused uneven pressure distribution inside the impeller, which leads to an imbalance in radial forces and offsetting the center of radial forces. With an increasing flow rate, the asymmetry of radial forces as well as the amplitude of their fluctuations increased. Non-uniform inflow was found to induce unstable flow structures inside the impeller, leading to low-frequency, high-amplitude pressure fluctuations near the hub. Using the enstrophy transport equation, it was shown that the relative vortex generation term played a major part in the spatiotemporal evolution of vortices, with minimal viscous effects.

Analysis of the Flow Behavior and Pressure Fluctuation of a Pump Turbine with Splitter Blades in Part-Load Pump Mode

The internal flow of a pump turbine is unstable in part-load pump mode for small guide-vane openings, and the strong vibration caused by pressure pulsation is related to the safe and stable operation of the unit. A pump turbine with a six-splitter-blade runner was chosen for unsteady simulation analyses. A standard k-epsilon turbulence model was adopted to study the unsteady flow and pressure pulsation in part-load pump mode. The predicted results show that the flow in the draft tube and the runner with splitter blades was relatively stable and the flow of the blade-to-blade channel was symmetrical. When the inlet and outlet velocity distribution of the vanes was not uniform, a vortex began to form in the stay-vane domain. The reason for this vortex formation is explained, and it is pointed out that the existence of the vortex and backflow leads to uneven velocity distribution. The unsteady calculation results showed that the pressure-pulsation peak-to-peak amplitudes in the vaneless area and guide vanes were much higher than those of other monitor points because of rotor–stator interference between the rotating runner and the vanes. In addition, the pulsation characteristics of the monitor points at different circumferential positions in the vaneless region were quite different. In the vaneless area, the velocity gradient along the circumferential direction was very large, and there was a phenomenon of backflow. Also, the pressure pulsation was 0.2 times that of the runner rotational frequency, and the blade-passing frequency was a third-order frequency. At the outlet of the guide vane, the pressure pulsation was mainly of a low frequency with a complex vortex flow. Finally, the pressure pulsation began to decrease rapidly in the stay-vane region.

Characterization of the Endwall Flow in a Low-Pressure Turbine Cascade Perturbed by Periodically Incoming Wakes, Part 2: Unsteady Blade Surface Measurements Using Pressure-Sensitive Paint

Unsteady pressure-sensitive paint (i-PSP) measurements were performed at a sampling rate of 30 kHz to investigate the near-endwall blade suction surface flow inside a low-pressure turbine cascade operating at engine-relevant high-speed and low-Re conditions. The investigation focuses on the interaction of periodically incoming bar wakes at 500 Hz with the secondary flow and the blade suction surface. The results build on extensive PIV measurements presented in the first part of this two-part publication, which captured the ’negative-jet-effect’ of the wakes throughout the blade passage. The surface pressure distributions are combined with CFD to analyze the flow topology, such as the passage vortex separation line. By analyzing data from phase-locked PIV and PSP measurements, a wake-induced moving pressure gradient negative in space and positive in time is found, which is intensified in the secondary flow region by 33% with respect to midspan. Furthermore, two methods of frequency-filtering based on FFT and SPOD are compared and utilized to associate a pressure fluctuation peak around 678 Hz with separation bubble oscillation.

3D-Printed Piezoelectric Stents for Electricity Generation Driven by Pressure Fluctuation.

Vascular stenting is a common procedure used to treat diseased blood vessels by opening the narrowed vessel lumen and restoring blood flow to ischemic tissues in the heart and other organs. In this work, we report a novel piezoelectric stent featuring a zigzag shape fabricated by fused deposition modeling three-dimensional (3D) printing with a built-in electric field. The piezoelectric composite was made of potassium sodium niobite microparticles and poly(vinylidene fluoride-co-hexafluoropropylene), complementing each other with good piezoelectric performance and mechanical resilience. The in situ poling yielded an appreciable piezoelectricity (d33 ∼ 4.2 pC N-1) of the as-printed stents. In vitro testing revealed that materials are nontoxic to vascular cells and have low thrombotic potential. Under stimulated blood pressure fluctuation, the as-printed piezoelectric stent was able to generate peak-to-peak voltage from 0.07 to 0.15 V corresponding to pressure changes from 20 to 120 Psi, giving a sensitivity of 7.02 × 10-4 V Psi-1. Biocompatible piezoelectric stents bring potential opportunities for the real-time monitoring of blood vessels or enabling therapeutic functions.

Novel Metric for Non-Invasive Beat-to-Beat Blood Pressure Measurements Demonstrates Physiological Blood Pressure Fluctuations during Pregnancy.

Beat-to-beat (B2B) variability in biomedical signals has been shown to have high diagnostic power in the treatment of various cardiovascular and autonomic disorders. In recent years, new techniques and devices have been developed to enable non-invasive blood pressure (BP) measurements. In this work, we aim to establish the concept of two-dimensional signal warping, an approved method from ECG signal processing, for non-invasive continuous BP signals. To this end, we introduce a novel BP-specific beat annotation algorithm and a B2B-BP fluctuation (B2B-BPF) metric novel for BP measurements that considers the entire BP waveform. In addition to careful validation with synthetic data, we applied the generated analysis pipeline to non-invasive continuous BP signals of 44 healthy pregnant women (30.9 ± 5.7 years) between the 21st and 30th week of gestation (WOG). In line with established variability metrics, a significant increase (p < 0.05) in B2B-BPF can be observed with advancing WOGs. Our processing pipeline enables robust extraction of B2B-BPF, demonstrates the influence of various factors such as increasing WOG or exercise on blood pressure during pregnancy, and indicates the potential of novel non-invasive biosignal sensing techniques in diagnostics. The results represent B2B-BP changes in healthy pregnant women and allow for future comparison with those signals acquired from women with hypertensive disorders.

Fluidization characteristics of loaded vibrating fluidized bed and dewatering and deashing effect of moist fine-grained coal

ABSTRACT The influence of a thermal vibrating fluidized bed on the dewatering and deashing effect of moist fine-grained coal was investigated by digital image processing and signal analysis methods. Comparative analysis results of the pressure signals of a loaded vibrating fluidized bed indicated that high or low gas velocity and strong or weak vibration conditions easily caused the formation of numerous irregular bubbles and contributed to violent fluctuations in the bed. An interaction between gas velocity and vibration energy was found, with vibration energy being the dominant factor influencing the bubble behavior at low gas velocities. Moreover, at high gas velocities, the advantages arising from vibrations were weakened. Under the condition of f = 20 Hz, A = 2 mm, v = 18 cm⋅s−1, the contact efficiency between the gas – solid two phases was higher, and the pressure fluctuation of the bed became more stable. Under this condition, the ash content of clean coal and the moisture removal rate were 11.76% and 83.54%, respectively. Finally, comparison and analysis of the influence of different parameters on the calorific value of clean coal revealed that the influence of each parameter on heat generation of the selected product was found to be in the following order: f > A > V > T.

Modeling a storage tank of carbon capture technology in a power plant in southern Iraq

The IEA's special study on CO2 collection, usage, and storage, released in 2020, estimates global CO2 capacity for storage to be among 8,000 and 55,000 gigatons. One of the most significant issues in introducing carbon into the energy market is improving carbon storage and developing more efficient distribution systems to increase the quantity of carbon that is held as liquid while decreasing storage pressure. The goal of this work is to investigate the efficiency of adsorption-based carbon-storing units from a "systems" perspective. The finite element approach, utilized in COMSOL Multi-physics™, is used to create an appropriate two-dimensional axisymmetric geometrical structure that balances energy, mass, and momentum based on thermodynamic extinction rules. We examine charging and discharging the storage unit with a rated pressure of 9 MPa and an initial temperature of 302 K.The storage tank is chilled using ice water. The research findings demonstrate that both simulated fluctuations in pressure and temperature during storage operations are extremely valuable. At the conclusion of charge time, the temperatures in the tank's center region are greater than those at the entry and along the wall, but at the end of discharge time, they are lower. The velocities are highest near the entry and progressively diminish throughout the tank's axis. As a result, even the lowest possible number (8,000 Gt) substantially surpasses the 100 Gt of CO2 required to be stored by 2055 under the "sustainable development" scenario. The IEA analysis also states that the land potential exceeds the offshore potential. Land-based storage capacity is estimated to be between 6,000 and 42,000 Gt, while offshore capacity is estimated to be between 2,000 and 13,000 Gt, assuming only sites less than 300 kilometers from the coast, at depths less than 300 meters, and outside the Arctic and Antarctic zones. Development of a prediction model to improve knowledge of a novel CO2 adsorbent during the adsorbent-desorption cycle, taking into account all transport events. Validation of the model against published data for H2 storage. Predicting pressure and temperature dispersion at various storage tank sites.

Associations of long-term fluctuation in blood pressure and ocular perfusion pressure with visual field progression in normal-tension glaucoma

BackgroudThe aim of this study was to investigate the associations between fluctuation in blood pressure (BP), ocular perfusion pressure (OPP) and visual field (VF) progression in normal-tension glaucoma (NTG).MethodsThis prospective, longitudinal study included 44 patients with NTG. Only newly diagnosed NTG patients who had not been treated with a glaucoma medication were included. Patients were examined every year for 7 years. Intraocular pressure (IOP), heart rate (HR), systolic BP (SBP), diastolic BP (DBP), ocular perfusion pressure (OPP), and diastolic ocular perfusion pressure (DOPP) were measured at the same time. Ophthalmic examinations, including perimetry, were performed also. Initial VF were compared with follow-up data after 7 years.ResultsAfter 7 years of follow-up, 9 of the 44 patients showed VF progression. The standard deviation (SD) of SBP and OPP were significantly associated with VF progression (P = 0.007, < 0.001, respectively). Multiple regression analysis showed that VF progression was significantly associated with SD of OPP (odds ratio, OR = 2.012, 95% CI = 1.016–3.985; P = 0.045).ConclusionsFluctuation in OPP was associated with VF progression in patients with NTG.

Novel adjustable backflow structure in electric coolant pump for balancing hydraulic performance and reducing temperature rise

An electric coolant pump serves as the source for coolant circulation in the thermal management of electric vehicles. To address the thermal issues for the printed circuit board integrated within the electric coolant pump, a novel backflow structure with an adjustable orifice diameter is designed from the impeller outlet to the printed circuit board to promote convective heat dissipation. Eventually, this flow returns to the impeller inlet, thereby altering the hydraulic performance of pump. The balance between hydraulic performance and temperature rise is achieved by adjusting the orifice diameter. Considering the variations in coolant properties with respect to temperature, numerical simulations of the electric coolant pump are performed using the unsteady compressible Reynolds-Averaged Navier-Stokes Equations. There is good agreement between experimental and numerical simulations results in both cases with and without an orifice. On an average, by increasing the orifice diameter by 1.5 mm which results in a 1.11 % decrease in efficiency, a 0.008 decrease in pressure coefficient, and a reduction of temperature by 2.98 K on printed circuit board. As the orifice diameter increases, leakage losses in the rear side chamber increases with the improvement of heat dissipation. The clash between the backflow jet and the inflow from the suction pipe results in significant entropy generation, forming jet vortices and increasing in pressure fluctuation. However, when the orifice diameter exceeds 3 mm, the cooling advantages no longer justify the trade-off in hydraulic performance. Thus, 3 mm orifice diameter is an optimal compromise between hydraulic performance and temperature control.