Pressure Distribution Research Articles

Refined simulation and verification of blast loads on curved shells

Terrorist attacks and accidental explosions pose significant challenges to the security of public buildings. This study combines detailed test data from three different curved shells to simulate different blast scenarios, effectively validating the simulation of blast loads and blast waves. Based on dynamic time warping and blast damage criteria, a similarity algorithm for blast loads based on overpressure histories of multi-gauge is proposed, and the similarity of blast loads on curved shells under four different scenarios is systematically evaluated. The spatiotemporal distribution of blast pressure around curved shells is analyzed based on simulation results. This paper provides a convenient tool for predicting blast loads on complex building shapes and optimizing blast-resistant designs.

Custom-made ocular prosthesis: enhancing the iris position of post-evisceration patient

Individuals who have impaired vision as a result of illness or injury may have their appearance improved with the use of a prosthesis eye. To construct realism, symmetry, and a glance that appears natural, it is necessary to duplicate the size and arrangement of the iris with accurate pinpoint accuracy. This is crucial for developing a realistic-looking gaze. Eye loss has a profoundly debilitating impact on the mental state of the person who has suffered it. The ultimate goal of every ocular prosthesis procedure is to facilitate the patient's reintegration into society while preserving their healthy visage and self-esteem. This article provides a clinical report on the rehabilitation of a patient whose left eye had suffered intraocular foreign body damage following evisceration. A closer fit between the prosthesis and the ocular base tissue can be achieved with custom-made acrylic resin ocular prosthesis that are sized and shaped to fit the ocular socket of the patient. This close fit results in a more uniform distribution of pressure compared to factory stock eye prosthesis and is more cost-effective than stock eye prosthesis

Experimental and numerical study on vibration response, VIV mechanism and aerostatic coefficients of triple-separated decks under different vertical distances

In this study, aerodynamic interference effects (AIE) on the vibration response, aerostatic coefficient (AC) and vortex-induced vibration (VIV) mechanism of the triple-separated decks under different incoming wind directions and vertical distances were investigated via wind tunnel tests and numerical simulations, respectively. The test results show that the AIE increases the displacement of VIV, and the VIV responses reaches maximum value under S/H = −1.0 (S is the vertical distance between the centers of RB and HB decks, and H is the height of RB deck) when the RB deck is on the windward side (the maximum displacements of VIV are 193.86% and 37.30% higher than the case of single RB deck and S/H = 0.0, respectively). The pressure distribution and flow structure show that the scale of vortex that alternately shed off from the tail of the deck becomes stronger and the fluctuating pressure coefficient increases under AIE, which increase the VIV amplitude of the RB deck and cause the VIV of HB decks. The experimental and numerical results indicated that the aerostatic coefficients (AC) of the leeward girder are more affected by the AIE. The interference factor (IF) of drag coefficient (CD) is far less than 1.0 under the case of F-5 (S/H = 0.0).

Numerical Analysis of Harmful Environmental Impact of Accidental Explosion at a Hydrogen Filling Station Environmental Impact of an Accident Hydrogen Explosion at a Gas Station

The purpose of this study is to evaluate numerically the consequences of a hydrogen-air mixture explosion at a vehicle hydrogen filling station. The physical process of the explosion, which takes place after the hydrogen gas release into the air due to the accidental destruction of a number of high-pressure storage cylinders, is considered. The blast pressure wave moves in all directions from the epicenter of the accident, gradually losing its intensity and having a negative shock impact on the service personnel of the filling station and the structures of the surrounding buildings. The scale of the accident depends on the number of destroyed cylinders, which determines the size of the hydrogen-air cloud and the power of the explosion. The degree of negative consequences for the environment depends on the maximum overpressure in the blast wave front. Numerical obtaining of spatial pressure distributions in the area of the accident based on a hydrogen explosion mathematical modeling makes it possible to separate zones that are dangerous to human health and building structures strength. The direct problem of gas dynamics of combustion products of a hemispherical cloud of a stoichiometric hydrogen-air mixture in the surface layer of the atmosphere is considered. The mathematical model of an instantaneous hydrogen explosion takes into account the three-dimensional and non-stationary nature of the propagation of the explosion wave, the compressibility of the gas flow, the complex terrain, the shape and initial concentration of the cloud of hydrogen combustion products, and their thermodynamic parameters. The model makes it possible to obtain three-dimensional fields of maximum overpressure, which are the basis for deterministic assessment of the consequences of an accident for human health and the integrity of structures in the area of the explosion. The presented computer technology allows security experts to identify potential dangerous zones by means of mathematical modeling, recommend effective protective measures to mitigate or even eliminate the negative consequences of the blast wave environmental impact.

Human-Centered Design and Manufacturing of a Pressure-Profile-Based Pad for Better Car Seat Comfort

A car seat’s function is to support, protect, and make passengers and drivers feel comfortable during a trip. A more uniform pressure distribution and a larger contact area usually provide less discomfort. Consequently, the seat pan’s material and geometry play an essential role in the design process. A shaped pad was opportunely designed and realized, starting from the pressure distributions between the buttocks and the seat pan; pressure data were acquired during an initial experiment involving 41 people, representing a wide range of percentiles. The shaped pad was compared with a standard one by building a special seat with an interchangeable internal pad and testing the standard and the new seat; the second experiment involved 52 people that tested both seats. The tests were conducted to assess comfort (33 subjects were asked to be seated for 1 min each) and discomfort (19 subjects were asked to be seated for 15 min each); during the tests, pressure distribution and contact area data were gathered. The results showed that, for both tests, about 80% of the participants, among which 100% of the female sample, preferred the shaped seat pan pad. Even if the material was exactly the same, the shaped pad seemed to be softer, more comfortable, and more suited to the body’s shape than the standard one. The design methodology was demonstrated to be very useful for granting a more uniform pressure distribution and a wider contact area, i.e., higher comfort and less discomfort.

Experimental Parametric Study on Flow Separation Control Mechanisms around NACA0015 Airfoil Using a Plasma Actuator with Burst Actuation over Reynolds Numbers of 105–106

Dielectric barrier discharge plasma actuators (DBD-PAs) have the potential to improve the performance of fluid machineries such as aircrafts and wind turbines by preventing flow separation. In this study, to identify the multiple flow control mechanisms in high Reynolds number flow, parametric experiments for an actuation parameter F+ with a wide range of Re values (105–106) for NACA0015 airfoil was conducted. We conducted wind tunnel tests by applying a DBD-PA to the flow field around a wing model at the leading edge. Lift characteristics, turbulent kinetic energy in the flow field, shear layer height, and the separation point of the boundary layer were evaluated based on pressure distributions on the wing surface and velocity of the flow field, with the effect of DBD-PA on the post-stall flow around the wing and the mechanism behind the increase in the lift coefficient CL analyzed based on these evaluation results. The following phenomena contributed to the increase in CL: (1) increase in turbulent kinetic energy; (2) increase in circulation; and (3) acceleration of the flow near the leading edge. Thus, this study effectively investigated the dependence of the increase in lift on F+ and the lift-increasing mechanism for a wide range of Re values.

Multifaceted simulation: Finite volume and finite element modeling of blood flow in multiple stenosed arteries

Cardiovascular illnesses are a primary global health concern because they are frequently brought on by arterial stenosis. The complicated hemodynamics of blood flow via elliptically shaped arteries with numerous stenotic lesions along their top and bottom walls are examined in this paper. Carreau fluid model is used with Navier–Stokes equations in this study. The complete comparative study is done by using the Finite Element and Finite Volume Methods. This study uses commercial software to examine blood flow velocity, pressure and temperature distributions under various physiological situations at Reynolds number 30. Our results illuminate the interaction between flow dynamics, stenosis characteristics, and arterial geometry. The novelty of the work is to investigate how stenosis size, shape, and location affect pressure gradients, and flow disturbances. These observations provide helpful direction for understanding disease progression, designing treatments, and possibly new stent designs. The future direction of this research may involve further exploration of the interplay between hemodynamics and arterial stenosis by incorporating advanced computational models. Additionally, studies focusing on in vivo validation and clinical applications could enhance the translational impact of the findings. Collaborations between researchers, clinicians, and engineers may pave the way for personalized treatment strategies and innovations in cardiovascular care based on a deeper understanding of the intricate dynamics within diseased arteries.

Investigation of the dynamic response of h-type anti-slide pile based on shaking table test

The h-type anti-slide piles (hTPs) are extensively utilized in slope stabilization projects, yet their response to seismic activities remains inadequately understood. This study investigated the dynamic response of hTPs with circular cross-sections (hTCPs) through a shaking table test, focusing on seismic events along Jiuzhaigou-Mianyang highway slopes (ZK142 + 124 to ZK142 + 274). Time-frequency analysis using Fast Fourier Transform (FFT) and Hilbert-Huang Transform (HHT) was conducted. The peak acceleration and its direction, dynamic earth pressure and its sharing ratio, and moment were characterized, and the variations of pile displacement and the seismic damage on different parts of hTCPs were analyzed under varying loading conditions. Results reveal a distinct pressure distribution and damage characteristics between the long and short piles in hTCPs. A positive correlation between peak accelerations and loading conditions was observed in both long and short piles, with peak amplification occurring only at the top of long piles. Long piles exhibited diverse acceleration directions under different loading conditions, contrasting with the infrequent occurrence in short piles. The peak dynamic earth pressure distribution varied between the front and back side of pile bodies, with opposite overall trends between the long and short piles. The sharing ratio displayed an increasing followed by decreasing trend in long piles, but an opposite trend in short piles, with the turn point occurring at a loading condition of 0.3 g. These differences were significantly influenced by El Centro waves within a low frequency band (13.34 Hz–16.18 Hz), as a single large peak HHT energy spectrum was observed in long piles, but multiple and destructive low-frequency energy spectra in short piles. The results suggest an independent dynamic response occurred in the long and short piles of hTCPs during shaking table test, providing insights for their field engineering application in seismic active regions.

The influence of crosswinds and leg positions on cycling aerodynamics

This work investigated the influence of crosswinds and leg positions on the aerodynamics of an articulated cycling mannequin on a track bicycle. Force, wake total pressure and wake velocity measurements were made in a low-speed sports wind tunnel of closed-circuit type. The freestream velocity and wheel speeds were kept at 15m/s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$15\\, \\hbox {m/s}$$\\end{document}. The crank angle of the mannequin was varied across a pedal cycle. Yaw angles from 0∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0^{\\circ }$$\\end{document} to 20∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$20^{\\circ }$$\\end{document} were examined. The experimental results reveal that the leg position significantly affects the aerodynamic performance of a cyclist. At high yaw angles, the aerodynamic drag on the cyclist showed noticeable deviations between most leg positions and their 180∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$180^{\\circ }$$\\end{document}-apart pairs. A wake analysis technique effectively captured the influence of leg positions on drag. The total pressure deficit contributes dominantly to the overall drag. The wake pressure contours demonstrate how leg-wheel interaction affects the total pressure distribution and drag under crosswinds. This study offers valuable insights into the flow behavior and drag generation around a cyclist with varying leg positions under crosswinds.

Resolving nonuniform flow in gas turbines: challenges, progress, and moving forward

Abstract The flow in gas turbines exhibits a highly unsteady, complex and nonuniform manner, which presents two main challenges. Firstly, it introduces instrumentation errors, contributing to uncertainties when calculating one-dimensional performance metrics during rig or engine tests using fixed-location rakes. Secondly, it raises mechanical concerns, including high-cycle fatigue due to blade row interactions in turbomachines and thermal fatigue caused by hot-streaks at the combustor exit. Experimental characterisation of the flow nonuniformity in gas turbines is highly challenging due to the confined space and harsh environment for instrumentation. This paper presents recent efforts to address this issue by resolving the nonuniform flow in gas turbines using spatially under-sampled measurements. The proposed approach utilises discrete probe data and leverages a ‘Fourier-based approximation’ method developed by the author. The technique has undergone preliminary experimental validation involving reconstruction of the total pressure distribution in a multi-stage axial compressor and the total temperature field at the exit of the combustor and high-pressure turbine. Results show that, in the multi-stage axial compressor environment, reconstruction of inter-stage total pressure is achieved using a reduced dataset covering less than 20% of the annulus with reasonably good accuracy. The reconstructed total pressure yields almost identical mean total pressure values at all spanwise locations, with a maximum deviation of less than 0.02%. Additionally, reconstruction of the total temperature distribution at an engine-representative full annulus combustor is achieved using measurements at ten carefully selected circumferential locations. Results show that the reconstructed temperature field successfully captures the primary features associated with combustor exit temperature flow. The reconstructed temperature field yields excellent agreement in the magnitude of radial temperature distribution factor (RTDF) and overall temperature distribution factor (OTDF) predictions to the experiment, with a deviation of less than 0.5% for RTDF and less than 2.5% for OTDF. Lastly, reconstruction of the total temperature distribution at the exit of the GE E3 high-pressure turbine (HPT) is achieved using measurements at eight carefully selected circumferential locations. Results demonstrate remarkable robustness in resolving the temperature profile at the HPT exit with high fidelity, irrespective of the HPT inlet conditions. The initial validation results are promising, demonstrating that the new probe layout scheme and the Fourier-based approximation method enable effective characterisation of flow nonuniformity in gas turbines, thereby providing valuable insights into the complex flow of gas turbine engines.

Innovative claw rotor design for claw vacuum pump and its power consumption analysis

The claw vacuum pump is extensively utilized in semiconductor, photovoltaic and aerospace industries because of its dry oil-free and compact structure. In order to reduce the power consumption of the claw vacuum pump caused by its special mixing process during operation, a novel pair of claw rotors was proposed. This innovation involves replacing the conventional circular arc at the dedendum of the claw rotors with an eccentric circular arc. A geometric model of the novel claw rotor was established, and the geometric characteristics of both the novel and conventional claw rotors were compared. Subsequently, the optimal design parameters were determined. The pressure distribution and power consumption of two claw vacuum pumps were analyzed with numerical simulations. Study results indicates that the power consumption of the proposed claw vacuum pump in the mixing process is reduced by 72.3 %, and the total power consumption is reduced by 12.6 % compared to the conventional pump. The study is of great significance for reducing power consumption of the claw vacuum pumps and improving application.

Flow Around a Pile Under Highly Non-linear Waves Using an Unstructured Finite-Volume Technique

This study has coupled a wave generating model with the existing in-house 3D Large Eddy Simulation (LES) hydrodynamic model. The primary focus is to simulate the hydrodynamics around a circular cylinder under non-linear waves. To accurately capture the behaviour of non-linear waves, a relaxation method is implemented on an unstructured grid, and its effectiveness is examined in a numerical wave tank with a vertical cylinder. To validate the accuracy of the proposed model, we compare the simulation results with experimental data, specifically analysing the transmission of the wave surface across the cylinder and examining the phased-averaged pressure distribution. The simulations also consider the shedding of lee-wake vortices, and the results are extensively discussed. Significantly, this paper represents the first known investigation of hydrodynamics under non-linear waves using the large-eddy simulation technique on unstructured grids. This approach opens up new possibilities for studying complex wave-structure interactions with improved accuracy and realism.

Wearable self-powered ballistic signal detectors with ferroelectric composites arrays for cardiovascular and diabetic complication

Abstract Background Flexible and wearable electronic devices with lightweight are needed to monitor and guide treatment in patients with cardiovascular disease and diabetic complication. We aimed to develop self-powered wearable bio-signal sensing arrays for cardiovascular and diabetic complication diagnosis and continuous monitoring. Methods Ferroelectric composites were designed to have piezoelectric property and high flexibility. Detection of arterial pulse as ballistogram (BCG) was simultaneously compared with electrocardiogram (ECG) in 20 controls. Heart rate and components of ECG was compared with those of BCG. Then, 9 ferroelectric BCG sensors as a square type array with self-power generation were fabricated to attachable thin film. Pressure distribution with BCG sensor array attached to socks were compared between 20 controls and 20 patients with diabetic neuropathy or vasculopathy during standing and ambulation for gait pressure distribution. Pressure distribution pattern was compared to neuropathy and vasculopathy parameters. Results Heart rate between BCG and ECG was significantly correlated (interclass correlation coefficient, ICC 0.99, 95% CI 0.98-0.99, p<0.001). QRS and T wave in ECG were correlated to second and third wave in BCG. Radial artery augmentation index by blood pressure monitoring was significantly correlated to BCG pressure (ICC 0.76, 95% CI 0.38-0.90, p=0.002). Analysis of foot pressure distribution demonstrated the highest pressure point at the anterolateral plantar area below a little tow. However, pressure gradient between anterolateral and anteromedial plantar area in diabetic patients was greater than that in controls (42.3±10.2 mV vs. 31.2±8.5 mV, p=0.024). Pressure gradient in diabetic patients was correlated to ankle-brachial index (ICC 0.62, 95% CI 0.32-0.90, p=0.036), but not to neuropathy parameters. Conclusion Wearable BCG sensor could accurately detect heart rate, blood pressure index and significantly correlated to ABI. Pressure distribution pattern and gradient analysis in diabetic patients by wearable BCG sensor arrays might predict diabetic complications. Gait remedial training guided by wearable BCG sensor arrays might aid to prevent diabetic complications.

A critical review on analysis of sand producing and sand-control technologies for oil well in oilfields

Sand production in oil wells seriously affects the production of oil and gas in oilfields. Although conventional sand-control techniques can effectively prevent sand production, it may also limit the productivity of oil wells. Fracturing and packing sand control technology changes the distribution of pressure and flow in the wellbore, while foam polymer resin diversion technology reduces the anisotropy of reservoir permeability and increases the area of oil leakage in the reservoir, both achieving the goal of sand control and increased production. The sand-free production rate is successfully increased thanks to zeta potential sand control technology, which modifies the formation’s sand potential and causes the sand to agglomerate without harming the reservoir. This article first looks into the causes of sand production in oil and gas wells before examining the fundamentals, implementation strategies, and effects of traditional sand control techniques, fracturing and filling sand control technology, foam polymer resin diversion technology, and Zeta potential sand control technology. In this article, the experience of sand control technology in actual oil field applications is summarized, explained in detail, and the future development possibilities of sand control technology are discussed.

Comparative evaluation of the sleep quality metrics between a cardboard bed and a camp cot: a randomized controlled crossover study.

Health-beneficial emergency bedding has become increasingly important for dealing with natural disasters such as the anticipated Nankai Trough earthquake in Japan. When the Great East Japan Earthquake occurred, cardboard beds were provided to evacuees. However, there were concerns about lower back pain and sleep disturbances, as cardboard beds offer insufficient pressure distribution. This study aimed to compare the effects of cardboard beds with those of foldable camp cots on sleep quality. A randomized controlled crossover study involving 20 healthy participants aged 18-45 years was conducted between June 2022 and January 2023. Participants were asked to sleep for one night on a camp cot and for another night on a cardboard bed, with a minimum three-day washout period between the two nights. Body pressure distribution and sleep metrics obtained from polysomnography (PSG) and questionnaires were compared between the two-bed types (P < 0.05). The camp cot exhibited better body pressure distribution than a cardboard bed, leading to improved sleep satisfaction, bedding comfort, and reduced morning sleepiness. Nevertheless, polysomnography revealed no notable differences in sleep metrics or sleep architecture between the two types of beds. Our findings indicate that cardboard beds have lower pressure dispersion capabilities than camp cots, leading to an increased number of position changes during sleep. Additionally, subjective sleep quality, such as alertness on waking, sleep comfort, and sleep satisfaction, was lower for cardboard beds, suggesting that camp cots might offer a more comfortable bedding option for evacuees. However, there were no discernible differences between the two-bed types in terms of objective sleep metrics derived from PSG. The potential for sleep disturbances caused by lower back pain from a hard mattress has been noted, and it is possible that a single night's experience in healthy individuals might not be enough for sleep issues to manifest.

Nonlinear excitation of energetic particle driven geodesic acoustic mode by Alfvén instability in ASDEX-Upgrade Tokamak

Recently, the coexistence of multiple energetic particle driven instabilities was observed in experiments on the ASDEX-Upgrade tokamak (Lauber et al 2018 27th IAEA Fusion Energy Conf.). A hybrid simulation using the MEGA code was performed to investigate the properties of those instabilities. The basic mode properties obtained in the simulations, such as mode frequencies, mode numbers, and inward energetic particle (EP) redistribution, are in good agreement with the experiments. It is found that the energetic particle driven geodesic acoustic mode (EGAM) is initially stable, then zonal flow gradually occurs with the growth of the Alfvén instability, and finally, the EGAM is nonlinearly excited and the amplitude exceeds the Alfvén instability. The dependence of EGAM properties on EP pressure and pitch angle distribution is analyzed. The EGAM amplitude increases with EP pressure. The nonlinearly excited EGAM is a high-frequency branch that appears even under the condition of a slowing-down EP distribution. The resonant particles are also analyzed, but the dominant resonant particles of the EGAM in the linear growth phase are not found because the EGAM does not grow in the linear regime. In the phase space of pitch angle variable Λ and energy E, it is found that initially the Alfvén instability is excited by EPs with poloidal frequency 70 kHz, then, after the saturation of the Alfvén instability, the resonance region moves towards lower energy and touches the EGAM resonance line, and finally, EGAM is excited by the particles with poloidal frequency 50 kHz . This process is a kind of resonance overlap.

Laser Doppler Vibrometer measurements of the 3D pressure field for the estimation of the radiation force produced by an acoustic standing-wave levitator

Acoustic levitation devices use powerful ultrasonic standing waves to levitate objects in mid-air. We have created a system and method to measure the full harmonic content of the acoustic field accurately. Our study revealed that levitated particles alter the pressure field in a way that is not immediately apparent from the first harmonic alone, highlighting the importance of precise and non-invasive measurement techniques. Our method uses computational tomography and optical sensing with the acousto-optic effect and a 3 DOF mechanical scanner. Our experiment results in a detailed 3D pressure distribution map for each harmonic of the ultrasonic acoustic field that generates the levitation forces.

Full time-dependent SOLPS-ITER simulation of the SPARC tokamak: Actuator design for particle and divertor condition control

Abstract This paper presents the application of full time-dependent SOLPS-ITER simulations for actuator design in the SPARC tokamak. This study employs both the EIRENE module, a neutral solver, and the B2.5 plasma module in a time-dependent mode. This is in contrast to most SOLPS simulations, which focus on steady-state solutions, where the neutral distribution is evolved without any time limit or for a time step of 1·10-3 second, which is several orders of magnitude larger than the fluid plasma time step. The time-dependent EIRENE was tested with a fixed B2.5 background and compared with a simple conductance based model in a simplified pump chamber geometry. This comparison aimed to verify the reliability of the neutral relaxation timescale derived from the time-dependent EIRENE. Subsequently, a full time-dependent simulation was performed in a realistic geometry, with the Monte-Carlo neutral time step synchronized with the plasma fluid time step. The numerical setup of the code, including relative time steps and the size of the census data used to store Monte-Carlo particle information is considered. The full-time dependent simulations are then applied to inform the design of the SPARC louver structure, which affects divertor plasma parameters by regulating the neutral conductance from the divertor to the pump. The response of the plasma and neutral parameters was captured on a timescale that enables the design of the actuator to consider time-dependent control capability. It was found that changing the louver opacity has an equivalent effect as varying the gas throughput via puff actuation. Therefore, equivalent divertor plasma conditions can be obtained from both actuators, while the neutral pressure distribution in the pump and divertor differs for each actuator.

A novel method for evaluating stack pressure in real high-rise buildings: Optimization of measurement points

Excessive stack pressure in a high-rise building always causes various problems, and the most direct way to understand the extent of the stack pressure across building components is to derive pressure distribution profiles for the entire buildings. As an alternative to measurement process, which is generally time-consuming and labor-intensive, an optimal field measurement method is proposed to investigate the real-time pressure distribution in operating high-rise buildings. The absolute pressure at unmeasured points can be accurately predicted from measured values at selected key points, both horizontally and vertically. Robust linear regression and the MARS model are applied to develop the related prediction models, and the number and positions of measurement points in the horizontal and vertical directions are optimized sequentially. Two high-rise buildings were selected to validate the applicability of the method, and five and six key pressure measurement points were finally determined, respectively. The measured and predicted absolute pressure values at unmeasured points were further compared, and the results showed a high goodness of fits as the R2 values were higher than 0.98 and the average MAE values were less than 2.0 Pa for all models. It is observed that the proposed method is suitable for engineering applications and demonstrates a practical method for investigating stack pressure distribution within high-rise buildings.

Parametric Study of Flow and Combustion Characteristic in a Cavitied Scramjet with Multi-Position Injection

This study focuses on the three-dimensional flow and combustion characteristics of a cavitied scramjet engine with multi-position injection. A single-equation large eddy simulation (LES) turbulence model is employed, with a detailed reaction mechanism for hydrogen combustion, as described by Jachimowski. The combustion characteristics of hydrogen in the scramjet combustion chamber are analyzed. Based on the combustion chamber model, the influence of different equivalence ratios, injection timing, injection positions, and injection pressures on the flame formation and propagation process are compared. The results indicate that within a certain range, an increase in the equivalence ratio enhances the combustion intensity and chamber pressure. In the case of multi-position injection, the order of injection from different nozzles has little effect on the final flame stabilization mode and pressure distribution. The opposite-side distribution of nozzles can effectively improve the fuel efficiency and the internal pressure. Furthermore, when the nozzles are closely placed in the opposite-side distribution, the combustion efficiency increases, although this leads to a higher total pressure loss. In scenarios where the fuel injection duration is short, an increase in the injection pressure at the upstream nozzles of the cavity results in a higher local equivalence ratio, as well as reduced fuel mixing and ignition time.