Plane Height Research Articles

Identifying Risk Factors for Wound Complications Following Fronto-Orbital Advancement in Patients With Craniosynostosis: 3-dimensional Craniometrics Analysis.

This study aims to identify 3-dimensional (3D) craniometric predictors of wound complications following fronto-orbital advancement (FOA) surgery in craniosynostosis patients. The authors conducted a retrospective review of medical records for 43 patients (25 female, 18 male) who underwent open FOA between 2006 and 2023, with an average follow-up duration of 91.8 months. The data collected included age at surgery, sex, whether the craniosynostosis was syndromic, involvement of multiple sutures, history of suturectomy, wound complications (categorized as minor or major), and preoperative and postoperative 3D CT scans. The authors quantified relative changes in intracranial volume (ICV), cranial area above the Frankfurt Horizontal plane, anteroposterior diameter (APD), and cranial height (CH) using Mimics software. A logistic regression analysis was performed to identify predictors of wound complications post-FOA. Among the 43 patients who underwent FOA, 10 experienced postoperative wound complications (4 minor, 6 major), revealing significant associations with multisuture involvement and changes in △cranial area, △APD, and △CH (all P<0.05). In the multivariable analysis with backward elimination, △cranial area, and △CH were identified as significant risk factors for wound complications (OR 1.17, 95% CI: 1.01-1.36, P=0.032; and OR 0.59, 95% CI: 0.38-0.92, P=0.019, respectively). The cutoff values for △cranial area and △APD were 5.95% and 7.93%, respectively. This study identified measurable craniometric changes, especially in the cranial area, as risk factors for wound complications following FOA. It underscores the necessity for personalized surgical planning and meticulous postoperative wound care in FOA to enhance patient outcomes through risk-aware strategies.

Analysis of 3D positioning error for multipath indoor VLC system

SummaryA comparative analysis of 3D positioning error for two different configurations using different layouts of visible light communication (VLC) systems is presented in this paper. The Received Signal Strength (RSS) has been implemented for indoor localization systems using Line‐of‐Sight (LoS) and diffused reflection signals. The room size for configuration‐1 is 5 m × 5 m × 3 m, and the distance between adjacent LEDs is 2.5 m, 2.00 m, and 1.5 m for cases‐1, case‐2, and case‐3, respectively, whereas the room size for configuration‐2 is 7 m × 7 m × 5 m, and the separation between the LEDs is 3.5 m, 3 m, and 2.5 m for their respective cases. Through investigation, it has been shown that when only LS signal is considered, the separation between LEDs may not be an issue because positioning error changes by a very small amount as the separation between LEDs changes. The results show that as the distance between adjacent LEDs decreases, the received signal strength for LoS and L‐R1 signals increases. However, positioning error and BER rise, while the bit rate falls. Furthermore, the positioning error Vs receiver plane height for all three cases in configuration‐1 is the same up to a height of 2.89 m, whereas the positioning error in configuration‐2 is the same up to 4.4 m for all cases. The positioning error for case‐1 decreases as the height in configuration‐1 exceeds 2.89 m. Similarly, after reaching a height of 4.4 m for case‐2, the positioning error in configuration‐2 decreases. The LoS positioning error versus semi angle of the LED as well as the FOV of the receiver has been simulated for different positions of the receiver in configuration‐1. The investigation shows that the minimum positioning error is achieved at and FOV equal to 66.660 for all the positions of the receiver in the room. Thus, before configuring a practical indoor VLC geometrical model, proper VLC configurations such as LED separation, FOV of the receiver, semi angle of LED, and receiver height should be chosen based on the room dimensions.

Triple notched MIMO antenna for S and C band applications

ABSTRACT A hexagon-shaped fractal multiple-input multiple-output (MIMO) antenna for WLAN, WiMax, and C band applications is proposed. The antenna consists of two hexagon-shaped self-similar fractal structures placed at a 6 mm gap with a reduced ground plane along with a ground stub at the centre. The proposed design covers the 2.37–7.82 GHz band with band rejections at 2.54–2.87 GHz, 3.56–3.83 GHz and 6.26–7.13 GHz. The notches are introduced to avoid interference between different application bands. The parametrically optimised reduced height of the ground plane and the strategical placement of a stub at the centre of this ground plane provide notch bands and reduce the mutual coupling below −17 dB throughout the operating bands. The proposed antenna gain varies between 2–3 dBi in the operating bands. The diversity parameters like envelope correlation coefficient (ECC) and diversity gain, channel capacity loss (CCL) and Total Active Reflection Coefficient (TARC) are calculated and found to be well below the acceptable range. A prototype of the proposed design is fabricated and measured. The measurement results are in good agreement with their simulated counterparts.

Tailoring bistability in optical tweezers with vortex beams and spherical aberration

We demonstrate a bistable optical trap by tightly focusing a vortex laser beam. The optical potential has the form of a Mexican hat with an additional minimum at the center. The bistable trapping corresponds to a nonequilibrium steady state, where the microsphere continually hops, due to thermal activation, between an axial equilibrium state and an orbital state driven by the optical torque. We develop a theoretical model for the optical force field, based entirely on experimentally accessible parameters, combining a Debye-type nonparaxial description of the focused vortex beam with Mie scattering by the microsphere. The theoretical prediction that the microsphere and the annular laser focal spot should have comparable sizes is confirmed experimentally by taking different values for the topological charge of the vortex beam. Spherical aberration introduced by refraction at the interface between the glass slide and the sample is considered and allows us to finetune between axial, bistable, and orbital states as the sample is shifted with respect to the objective focal plane. We find overall agreement between theory and experiment for a rather broad range of topological charges. Our results open the way for applications in stochastic thermodynamics, as they establish a control parameter—the height of the objective focal plane with respect to the glass slide—that allows us to shape the optical force field in real time and in a controllable way. Published by the American Physical Society 2024

Experimental and numerical investigations on fire development in a timber-based compartment with identification of characteristic events

An experiment and numerical simulations were carried out to investigate the mechanism of the incipient and growth stages of a building fire. The building, constructed in the 1980s with wooden components, has one compartment and one opening. The average fire load density was 1495.3 MJ/m2, including the wooden columns, beams, furniture, etc. The evolution of indoor temperature, gas concentration, gas flow rate and burning behaviors were obtained and analyzed. To better understand the fire development process, we identified characteristic events, including pilot fire, incipient fire, pre-flashover fire spread, ceiling jet period, and flashover and spill plume. By defining dimensionless time (τ = ti/tflashover), it was found that the fire development process simulated by Fire Dynamic Simulator experienced the same characteristic events as the experiment. In this work, when flashover occurred, the neutral plane height decreased to about half the height of the opening, the velocity of hot smoke outflow was higher than 3 m/s, and the maximum thickness of the wood charred layer reached 1 cm. Two theoretical methods to estimate the heat release rate (HRR) in the fuel-controlled stage before flashover were proposed. The HRRs at the time of flashover with the two methods are at the same order of 5 MW, and the error between them was within 18.1%, which verifies the feasibility of the above methods to a certain extent. This study helps to learn the characteristics of early and growth stages of building fires with wooden components.

Multi-objective hybrid split-ring resonator and electromagnetic bandgap structure-based fractal antennas using hybrid metaheuristic framework for wireless applications

Design closure and parameter optimisation are crucial in creating cutting-edge antennas. Antenna performance can be improved by fine-tuning preliminary designs created using theoretical considerations and rough dimension adjustment via supervised parameter sweeps. This paper introduces a frequency reconfigurable antenna design that can operate at 28/38 GHz frequencies to meet FCC and Ofcom standards for 5G applications and in the 18 GHz frequency band for K-band radar applications. A PIN diode is used in this design to configure multiple frequency bands. The antenna has a modified rectangular patch-like structure and two optimised plugins on either side. The study that is being presented focuses on maximising the parameters that are subject to optimisation, including length (Ls), width (Ws), strip line width (W1), and height (ht), where the antenna characteristic parameters such as directivity is tuned by a hybrid optimisation scheme called Elephant Clan Updated Grey Wolf Algorithm (ECU-GWA). Here, the performance of gain and directivity are optimally attained by considering parameters such as length, width, ground plane length, width, height, and feed offsets X and Y. The bandwidth of the proposed antenna at − 10 dB is 0.8 GHz, 1.94 GHz, and 7.92 GHz, respectively, at frequencies 18.5 GHz, 28.1 GHz, and 38.1 GHz. Also, according to the simulation results, in the 18 GHz, 28 GHz, and 38 GHz frequencies S11, the return loss is − 60.81 dB, − 56.31 dB, and − 14.19 dB, respectively. The proposed frequency reconfigurable antenna simulation results achieve gains of 4.41 dBi, 6.33 dBi, and 7.70 dBi at 18.5 GHz, 28.1 GHz, and 38.1 GHz, respectively. Also, a microstrip quarter-wave monopole antenna with an ellipsoidal-shaped complementary split-ring resonator-electromagnetic bandgap structure (ECSRR-EBG) structure has been designed based on a genetic algorithm having resonating at 2.9 GHz, 4.7 GHz, 6 GHz for WLAN applications. The gain of the suggested ECSRR metamaterial and EBG periodic structure, with and without the ECCSRR bow-tie antenna. This is done both in the lab and with numbers. The measured result shows that the ECSRR metamaterial boosts gain by 5.2 dBi at 5.9 GHz. At 5.57 GHz, the two-element MIMO antenna achieves its lowest ECC of 0.00081.

Radiographic Investigation of Coronal Plane and Patellar Height and Changes Following Tibial Deflection Osteotomy for Correction of Tibial Slope in Combination With ACL Reconstruction

Background: A tibial deflexion osteotomy (TDO) is performed to decrease the sagittal tibial slope to reduce the relative risk of anterior cruciate ligament (ACL) reconstruction (ACLR) graft failure. Given that coronal plane osteotomies can cause consequential changes in the sagittal plane to patellar height and tibial slope, potential changes to coronal plane alignment and patellar height can result after a sagittal plane osteotomy. Purpose: To compare preoperative and postoperative coronal plane alignment after TDO, as well as to analyze the effect of the osteotomy on patellar height. Study Design: Case series; Level of evidence, 4. Methods: This study was conducted on a consecutive series of patients with primary and revision ACLR with concomitant TDO between 2011 and 2022. Inclusion criteria were 1-stage autograft ACLR combined with supratubercular TDO with pre- and 3 months postoperative radiographs of sufficient quality. Indications for TDO were anterior instability requiring ACL revision surgery and a posterior tibial slope (PTS) >9° or a PTS >14° in the primary ACL surgery patients. Anteroposterior and lateral knee radiographs were reviewed, and the medial proximal tibial angle (MPTA), PTS, Caton-Deschamps index (CDI), and modified Insall-Salvati ratio were measured directly from the radiographs by 2 independent reviewers. Results: A total of 68 patients were included in this study. Pre- and postoperative radiographs were performed 1 month before and 3 months after surgery, respectively. There was a significant increase in the mean MPTA of 0.95° varus (SD, 2.1°; range, increase of 4.23° valgus to increase of 7.74° varus; P < .01), a decreased PTS of 8.86° (SD, 3.03°; P < .01), and an increased CDI of 0.08 (range, decrease of 0.27 to increase of 0.64) (P < .01; SD, 0.17) in patients undergoing TDO. Insall-Salvati ratio measurements showed no difference. There was good intra- and interobserver reliability, with intraclass correlation coefficients of 0.97 and 0.91 for MPTA, 0.97 and 0.87 for PTS, 0.87 and 0.93 for CDI, and 0.88 and 0.76 the Insall-Salvati ratio. Conclusion: This study, the largest series on TDO for ACLR, demonstrates that the TDO can be performed safely without large changes to coronal alignment or patellar height. The tibial slope was reduced by a mean of 8.86° (range, 2.3°-11.5°; P < .01). The TDO produces a small statistically significant change to coronal alignment, inducing a mean increased varus of <1° and an increased patellar height of 0.1 CDI. Therefore, TDO can be performed safely without dramatic changes to coronal alignment or patellar height, this study highlights technical aspects to minimize iatrogenic varus.

The Effect of the Fuel Location and Ventilation Factor on the Fire Dynamics of Informal Settlement Dwellings

AbstractThree full-scale experimental compartment fires are compared to investigate the effect of the fuel location and the ventilation factor on under ventilated thermally thin bounded ISO-9705 compartments. Wood cribs were used as the fuel load and the crib placement was varied between two locations (back and middle) to study the effect of the fuel location. Furthermore, the ventilation conditions were changed from a door and window (i.e., ventilation factor of 2.58 m5/2) to only a door (i.e., ventilation factor of 2.26 m5/2) for the scenario where the cribs were placed at the back of the compartment. The novelty of this work lies in its examination of the time to flashover, gas layer temperature, heat release rate, and external radiative heat fluxes, specifically considering the impact of fuel location and ventilation factor. It was observed that placing the fuel package in the middle of the compartment led to a longer growth phase, hotter gas layer temperature, a higher Heat Release Rate (HRR) needed for flashover ($$\dot{q}_{fo}$$ q ˙ fo ), and higher external radiative heat fluxes through openings. It was also found that, decreasing the ventilation factor decreased the heat losses and therefore the $$\dot{q}_{fo}$$ q ˙ fo . Decreased ventilation also affected the height of the neutral plane, as one would expect, and the shape of the external plume, but did not have significant effect on the temperature within the compartment, the walls of the compartment, and the external radiative heat flux.

Estimation of Road Surface Plane and Object Height Focusing on the Division Scale in Disparity Image Using Fisheye Stereo Camera

In this paper, we propose a novel algorithm for estimating road surface shapes and object heights using a fisheye stereo camera. Environmental recognition is an important task for advanced driver-assistance systems. However, previous studies have only achieved narrow measurement ranges owing to sensor restrictions. Moreover, the previous approaches cannot be used in environments where the slope changes because they assume inflexible constraints on the road surfaces. We use a fisheye stereo camera capable of measuring wide and dense 3D information and design a novel algorithm by focusing on the degree of division in a disparity image to overcome these defects. Experiments show that our method can detect an object in various environments, including those with inclined road surfaces.

Assessment of the Performance of FireFOAM in Simulating a Real-Scale Fire Scenario Using High Resolution Data

An assessment of the performance of FireFOAM in simulating a large-scale compartment fire scenario is presented in this study, using the Edinburgh Tall Building Fire Test I (2017) as the basis for evaluation. Different mesh geometries and sizes are tested, and both theory-based and experiment-based validation approaches are employed. The theory-based validation revealed that the implemented finite volumes method is generally conservative, but unaccounted deviations of up to 20% for the heat release rate were observed due to errors in numerically modelling subgrid phenomena, particularly with tetrahedral meshes. In the experiment-based validation, the simulated data showed good agreement with experimental measurements for flow patterns inside the compartment, neutral plane height, and temperatures outside the ceiling jet. However, there were relatively large errors in incident radiation in the hot gas zone, thermal boundary layer transient temperatures, and compartment inflow/outflow velocities. Systematic errors were attributed to deficient heat transfer boundary conditions and under-estimated air entrainment. The study also identified ways to improve run-time efficiency by implementing parallel processing or reducing solid angles in FVDOM, although using large meshes (30 cm and 40 cm cell size) resulted in faster run-times at the cost of accuracy.

An analytical model of stack ventilation in a shaft with controllable air volume

This work investigates a stack ventilation system in a shaft with controllable air volume suitable for large public buildings, which can adjust natural ventilation volume on demand and avoid heat loss in winter. The driving force and resistance of this system was analysed, a correction coefficient C0 for air confluence in the shaft was proposed based on the local resistance of a confluent T-junction, and a quantitative model of ventilation volume and height of a neutral plane was developed. Then, the inlet air volume obtained from field tests of the shaft in an actual project during the autumn, as well as the driving temperature obtained from computational fluid dynamics (CFD) simulations of the airflow in the shaft (using the test results as the boundary conditions), were used to solve for C0. Finally, the model was validated by the comparison of predictions with the inlet air volume obtained from tests of the shaft in the same project during the winter and heights of the neutral plane from the simulations. The results showed that this model was reasonably accurate and suitable for the design of stack ventilation systems in shafts for large public buildings with controllable air volume.

Experiment study of fire characteristics in full-scale bedrooms under different vents and sprinkler conditions

The risk of fire in residential buildings is relatively high, with a significant number of incidents and loss of life reported. This study aimed to examine fire scenarios in bedroom by conducting real scale experiments with different set-up of vents and using realistic fuel loads. Five full-scale compartment fire tests were conducted, and a sprinkler system was installed in one of the rooms. The experimental setup, fuel arrangement, and instrumentation are described, and the fire characteristics was analyzed based on visual observations and temperature data processing. The performance of the fire detectors and sprinklers in the tests are discussed. The influence of opening size on the peak temperature, heat release rate, and the constant coefficient of Kawagoe law are estimated and analyzed. Furthermore, a non-dimensional neutral plane height was found to have strong relationship with the constant coefficient of Kawagoe law.

The imprint of galaxy mergers on satellite planes in a cosmological context

ABSTRACT Flattened and kinematically correlated planes of dwarf satellite galaxies have been observed in the Local Volume. The slinging out of satellites during host galaxy mergers has been suggested as a formation mechanism for these peculiar structures. We statistically examined the impact of major mergers on present-time satellite systems for the first time in a full cosmological context using the IllustrisTNG suite of hydrodynamic simulations. Mergers with mass ratios above 1/3 generally have a negligible or adverse impact on the phase-space correlation of observationally motivated satellites. Even high angular momentum mergers are inefficient at slinging satellites outward due to the extended nature of simulated satellite distributions. Furthermore, any potential merger imprint is partially washed out by post-merger accretion of satellites, while satellites bound to the merging haloes since the merger’s beginning are disrupted and stripped of mass – minimizing the merger’s influence on the present-time distribution of the most massive satellites after $2{\!-\!}5\, \mathrm{Gyr}$. Constraining our sample to satellites bound to their host throughout the full duration of their system’s last merger, we recover no particular improvement in their phase-space correlation. Instead, such participant satellites experience a contraction of their radial distribution during and after the merger, resulting in smaller absolute plane heights (but comparable axial ratios). Overall, major mergers do not appear to form correlated planes in a statistical sample. Mergers that efficiently transfer their angular momentum to satellite distributions can marginally enhance their phase-space correlation, but cannot form highly flattened and orbitally coherent configurations as observed in our local Universe.

Efficient Evaluation of Concrete Fracture Surface Roughness Using Fringe Projection Technology.

The evaluation of concrete surface roughness is crucial in the field of civil engineering. The purpose of this study is to propose a no-contact and efficient method for the measurement of the roughness of concrete fracture surfaces based on fringe-projection technology. A simple phase-correction method using one additional strip image is presented for the phase unwrapping to improve the measurement efficiency and accuracy. The experimental results indicate that the measuring error for plane height is less than 0.1mm, and the relative accuracy for measuring a cylindrical object is about 0.1%, meeting the requirements for concrete fracture-surface measurement. On this basis, three-dimensional reconstructions were carried out on various concrete fracture surfaces to evaluate the roughness. The results reveal that the surface roughness (R) and fractal dimension (D) decrease as the concrete strength increases or the water-to-cement ratio decreases, consistent with previous studies. In addition, compared with the surface roughness, the fractal dimension is more sensitive to the change in concrete surface shape. The proposed method is effective for detecting concrete fracture-surface features.

In-situ desulfurization using porous Ca-based materials for the oxy-CFB process: A computational study

Within circulating fluidized bed (CFB) processes, gas and solid behaviors are mutually affected by operating conditions. Therefore, understanding the behaviors of gas and solid materials inside CFB processes is required for designing and operating those processes. In addition, in order to minimize the environmental impact, modeling to reduce pollutants such as SOx emitted from those processes is essential, and simulation reproduction is necessary for optimization, but little is known. In this study, the gas and solid behaviors in a pilot-scale circulating fluidized bed combustor were investigated by using computational particle fluid dynamics (CPFD) numerical simulation based on the multiphase particle-in-cell (MP-PIC) method under oxy-fuel combustion conditions. In particular, the combustion and in-situ desulfurization reactions simultaneously were considered in this CPFD model. Effect of fluidization number (ULS/Umf) was investigated through the comparison of particle circulation rates with regards to the loop seal flux plane and bed height in the standpipe. In addition, the effects of parameters (temperature, Ca/S molar ratio, and particle size distribution), sensitive indicators for the desulfurization efficiency of limestone, were confirmed. Based on the cycle of the thermodynamic equilibrium curve of limestone, it is suggested that direct and indirect desulfurization occur simultaneously under different operating conditions in CFB, creating an environment in which various reactions other than desulfurization can occur. Addition of the reaction equations (i.e., porosity, diffusion) to the established simple model minimizes uncertainty in the results. Furthermore, the model can be utilized to optimize in-situ desulfurization under oxy-CFB operating conditions.

Experimental and theoretical study on the characteristics of the spill plume in a compartment fire with high-low opposing openings

This paper presents the characteristics of the spill plume in a compartment fire with high-low opposing openings. Three sizes of doors (low openings), six sizes of windows (high openings), and three heat release rates were adopted. Mass flow rates through the openings were calculated with new length scales considering the effect of bidirectional airflow at the door, and then the expression of the neutral plane height was derived. The calculated results had good agreement with the experimental results. To reveal the effect of the opening sizes on the energy proportion, the heat fluxes from the openings were calculated based on the new length scales, and the heat lost through compartment boundaries was also obtained. It was found the size variation of any opening would affect the proportion of each part of the energy and the ratio of heat flow through openings can be represented by the 5/2 power of the ratio of the new length scales. The fire spill plume thickness is related to the horizontal velocity of the plume ejected from the window, and one linear relationship was established. Moreover, the heat flux along the façade and the temperature distribution of the fire spill plume outside the window were given with the new length scale.

A novel bi-planar calibration method for digital templating in total hip arthroplasty

In total hip arthroplasty and reconstructive orthopedic surgery, pre-operative digital templating is essential for surgical treatment optimization, risk management, and quality control. Calibration is performed before templating to address magnification effects. Conventional methods including fixed calibration factors, individual marker-based calibration and dual-scale marker methods are not reliable. A novel bi-planar calibration method is described aiming to reduce the error below clinical significance. The bi-planar calibration method requires two conventional orthogonal radiographs and a standard radiopaque marker ball. An algorithm computes the hip plane height parallel to the detector in the antero-posterior radiograph. Foreseeable errors (i.e., patient rotation and misplaced markers or lateral offset) are considered in a correction algorithm. Potential effects of errors are quantified in a standard model. Influence of rotation in lateral radiographs and lateral offset of marker on the calibration factor are quantified. Without correction, patient rotation in the lateral radiograph of 30° results in absolute calibration error of 2.2% with 0 mm offset and 6.5% with 60 mm lateral offset. The error is below the threshold of 1.5% for rotation less than 26° with 0 mm offset and 10° with 60 mm offset. The method is supposed to be reliable in precisely predicting the hip plane and thereby the calibration factor. It may be superior to other methods available. In theory, the method allows correction of clinically relevant rotation of at least 30° and marker displacement without impacting the computed calibration factor.

Analysis of Load Transfer and the Law of Deformation within a Pile-Supported Reinforced Embankment

In this paper, the load-transfer mechanism and settlement behaviors of the pile-supported reinforced embankment are reviewed by laboratory model tests, and a series of finite element method (FEM) modellings are conducted to analyze the soil-arching geometry and embankment deformation patterns of the pile-supported reinforced embankment. The results show that: the embankment load distribution is significantly impacted by the filling cohesion because of the effect of cohesion on the interaction between particles. The soil pressure difference between the center and corner of the pile caps decreases with the increase of filling cohesion. The pile-subsoil stress ratio decreases with the increase of filling cohesion. The embankment deformation behavior and soil-arching geometry are less affected by the change in filling cohesion compared with the influence of pile spacing. That may because of the fact that although the cohesion of the embankment filling has been increased, the granular material’s properties have not been fundamentally changed. Pile-subsoil different settlement decreases with the increase of embankment filling cohesion, and the different settlement at the mid-span between four piles decreases by 4.09% and 6.34%, respectively, as filling cohesion increases from 0 kPa to 11 kPa and 25 kPa. The height of the soil-arching crown decreases with the increase of filling cohesion, and the height of the soil-arching crown between horizontal adjacent piles decreases by 3.85%, 7.69%, and 9.62%, as filling cohesion increases from 5 kPa to 15 kPa, 25 kPa and 45 kPa. The rate of decrease in soil-arching height gradually decreases with increasing cohesion. The height of the soil-arching between the horizontal adjacent piles is about 1.0 (s−a). The height of soil arching between the diagonal adjacent piles is about 1.02 (s−a). The differential settlement at the same height inside the embankment decreases with the increase of filling cohesion, and the height of the equal settlement plane is basically the same as the height of soil arching.

Study on the maximum temperature beneath the ceiling with different neutral plane heights for long narrow space fires

Study on the maximum temperature beneath the ceiling with different neutral plane heights for long narrow space fires

Comparative Study on Theoretical and Numerical Calculations of Mass Flow Rate through Opening of Compartment

In this study, stratified, well-mixed, and simplified theoretical model equations and Fire Dynamics Simulator (FDS) were used to calculate the mass inflow, outflow and neutral height to determine the usefulness of previously proposed simple formulas for the calculation of the mas flow rate through openings of compartments in case of fire. The mass flow rate through the opening was evaluated for two conditions, i.e., a fire inside the compartment and no fire, with a high-temperature homogeneous mixture filled inside the compartment. The height of the neutral plane calculated using the theory and FDS under the condition of fire inside the compartment well obeyed the trend of the experiment. In particular, the FDS results for the neutral plane height and inlet air mass flow well agreed with the experiment. However, for the inlet air mass flow rate, the theoretically obtained stratified and well-mixed model equations overestimated the mass flow variation trend according to the increase in opening width. The results of the stratified model equation were the most consistent with the FDS calculation results regardless of temperature, under the condition of a uniform mixture inside the compartment. Regarding the inlet air flow rate, the difference between the theoretical equation result and FDS result was not small. In contrast, for the effluent air flow rate, the results of the simplified formula were the most consistent with the FDS results.