Application of Zone Models for Under-Ventilated Compartment Fires

2006 ◽  
Author(s):  
T. Mizukami ◽  
Y. Utiskul ◽  
J. G. Quintiere
Keyword(s):  
Loss Rate ◽  
Lower Layer ◽  
Mass Loss Rate ◽  
Thermal Conditions ◽  
Small Scale ◽  
Zone Model ◽  
Fuel Type ◽  
Ambient Oxygen ◽  
Good Agreement ◽  
Lower Compartment

A model is presented that explains the mass loss rate in a compartment as a function of fuel type and scale. The effect of ventilation is included in the model by the inclusion of the ambient oxygen concentration in the lower layer that results due to vent mixing. The model is executed in BRI2002, a zone model, capable of computing species and thermal conditions in the upper and lower compartment gas layers. Computations show good agreement with small-scale compartment data for heptane pools. The results can accurately portray extinction, oscillations in burning, reduction in the flaming area, and quasi-steady behaviors.

scholarly journals ESTIMATING THE PROPAGATION OF A UNIFORMLY ACCELERATED JET

2021 ◽  
Vol 57 (2) ◽  
pp. 297-309
Author(s):  
J. I. Castorena ◽  
A. C. Raga ◽  
A. Esquivel ◽  
A. Rodríguez-González ◽  
L. Hernández-Martínez ◽  
...  
Keyword(s):  
Loss Rate ◽  
Mass Loss Rate ◽  
Center Of Mass ◽  
Analytic Solutions ◽  
Pressure Balance ◽  
Working Surface ◽  
Ram Pressure ◽  
Balance Solution ◽  
Analytic Models ◽  
Good Agreement

We study the problem of a Herbig-Haro jet with a uniformly accelerating ejection velocity, travelling into a uniform environment. For the ejection density we consider two cases: a time-independent density, and a time-independent mass loss rate. For these two cases, we obtain analytic solutions for the motion of the jet head using a ram-pressure balance and a center of mass equation of motion. We also compute axisymmetric numerical simulations of the same flow, and compare the time-dependent positions of the leading working surface shocks with the predictions of the two analytic models. We find that if the jet is over-dense and over-pressured (with respect to the environment) during its evolution, a good agreement is obtained with the analytic models, with the flow initially following the center of mass analytic solution, and (for the constant ejection density case) at later times approaching the ram-pressure balance solution.

Examination of the Transferability of CTOA From Small-Scale DWTT to Full-Scale Pipe Geometries Using a Cohesive Zone Model

2020 ◽  
Author(s):  
Chris Bassindale ◽  
Xin Wang ◽  
William R. Tyson ◽  
Su Xu
Keyword(s):  
Finite Element ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Element Model ◽  
Full Scale ◽  
Opening Angle ◽  
Small Scale ◽  
Zone Model ◽  
Pipe Model ◽  
Good Agreement

Abstract In this work, the cohesive zone model (CZM) was used to examine the transferability of the crack tip opening angle (CTOA) from small-scale to full-scale geometries. The pipe steel STPG370 was modeled. A drop-weight tear test (DWTT) model and pipe model were studied using the finite element code ABAQUS 2017x. The cohesive zone model was used to simulate crack propagation in 3D. The CZM parameters were calibrated based on matching the surface CTOA measured from a DWTT finite element model to the surface CTOA measured from the experimental DWTT specimen. The mid-thickness CTOA of the DWTT model was in good agreement with the experimental value determined from E3039 and the University of Tokyo group’s load-displacement data. The CZM parameters were then applied to the pipe model. The internal pressure distribution and decay during the pipe fracture process was modeled using the experimental data and implemented through a user-subroutine (VDLOAD). The mid-thickness CTOA from the DWTT model was similar to the mid-thickness CTOA from the pipe model. The average surface CTOA of the pipe model was in good agreement with the average experimental value. The results give confidence in the transferability of the CTOA between small-scale specimens and full-scale pipe.

Applicability of FLASH-CAT Model to Cable Tray Fire Modeling in Zone Model BRI2002

2020 ◽  
Author(s):  
Koji Shirai ◽  
Koji Tasaka ◽  
Toshiko Udagawa
Keyword(s):  
Mass Loss ◽  
Large Scale ◽  
Fire Test ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Zone Model ◽  
Gas Temperature ◽  
Fire Source ◽  
Gas Burner ◽  
Tray Fire

Abstract To clarify the heat and smoke propagation in multi-compartments under the spread of cable fire, a large-scale multi-compartment fire test (hereinafter the CFS-2 test) was performed by the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) in France within the framework promoted by the Nuclear Energy Agency (NEA) in Organization for Economic Co-operation and Development (OECD) program PRISME2 (OECD/NEA, 2017). In the CFS-2 test, two rooms of a large-scale facility were adopted and these rooms have an identical volume (120 m3) enclosed with fire walls and were connected by a doorway (0.8 m in width and 2.17 m in height). As a fire source, five-layer cable trays (tray length of 2.4m, tray width of 0.45m and separation distance between trays of 0.3 m) with a fire-retardant PVC cable (77 kg) were used and ignited by a propane gas burner. The power level of the propane gas burner was set to around 80 kW. Moreover, all rooms were mechanically ventilated, and the renewal rate was 15 times per hour (3600 m3/h). During the fire test, the mass loss rate of fuel, gas and soot mass concentration, gas temperature, and etc. were measured. The measured peak values of the HRR, the mass loss rate and gas temperature were about 800 kW, 58 g/s and greater than 600 °C, respectively (Zavaleta, 2017). As a fire model predicting fire characteristics in a compartment, a two-zone model, which divides the fire room into the hot smoke upper layer and lower layer consisting of cool fresh air, is widely used due to the advantages of the brevity of the calculation routine and the reliability of the calculation results. Among them, the BRI2 series, developed in Japan, is now reaching the current BRI2002 software (Wakamatsu, 2004) after several upgrades to improve the calculation precision. The Central Research Institute of Electric Power Industry (CRIEPI) introduced the cable tray fire source model based on the FLASH-CAT (Flame Spread over Horizontal Cable Trays) developed by National Institute of Standards and Technology (NIST) (McGrattan, 2012) into the zone code BRI2002. By comparing the numerical results with the experimental values measured during the CFS-2 test, the methodology for ignition time delay of each tray and horizontal flame propagation speed for each tray were discussed.

scholarly journals Solar wind, mass and momentum losses during the solar cycle

2010 ◽  
Vol 6 (S271) ◽  
pp. 395-396
Author(s):  
R. Pinto ◽  
S. Brun ◽  
L. Jouve ◽  
R. Grappin
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Wind Speed ◽  
Mass Flux ◽  
Solar Minimum ◽  
Momentum Flux ◽  
Loss Rate ◽  
Convection Zone ◽  
Mass Loss Rate ◽  
Good Agreement

AbstractWe study the connections between the sun's convection zone evolution and the dynamics of the solar wind and corona. We input the magnetic fields generated by a 2.5D axisymmetric kinematic dynamo code (STELEM) into a 2.5D axisymmetric coronal MHD code (DIP). The computations were carried out for an 11 year cycle. We show that the solar wind's velocity and mass flux vary in latitude and in time in good agreement with the well known time-latitude assymptotic wind speed diagram. Overall sun's mass loss rate, momentum flux and magnetic breaking torque are maximal near the solar minimum.

scholarly journals Bottom fire behaviour of thermally thick natural rubber latex foam

e-Polymers ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 9-14 ◽  
Author(s):  
Shuwen Wang ◽  
Dongmei Huang ◽  
Chenning Guo ◽  
Qi Yuan ◽  
Yongliang Chen ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Rear Surface ◽  
Natural Rubber Latex ◽  
Bottom Surface ◽  
Small Scale ◽  
Fire Behaviour ◽  
Full Development ◽  
Three Stages

AbstractIn this paper, the bottom fire behaviour of 25 cm × 25 cm × 5 cm natural rubber (NR) latex foam with uniformly distributed 6 mm diameter holes was investigated experimentally in a small-scale experimental platform under bottom ventilation. The bottom fire behaviour was analysed. The results show that the burning process of the thermally thick NR latex foam under bottom ventilation conditions can be divided into three stages: initial growing, full development, and decay. A deflagration covered the entire rear surface was observed at 308 s. The burning balls moving at a speed of 0.15 m/s were observed after the bottom ignition and they moved from the center to the sides along with the expansion. The mass loss rate of the sample was accelerated dramatically from 0.2 g/s to 0.5 g/s when the bottom surface was ignited at 308 s.

scholarly journals Delta-slow solution to explain B supergiant stars' winds

2014 ◽  
Vol 9 (S307) ◽  
pp. 104-105
Author(s):  
M. Haucke ◽  
I. Araya ◽  
C. Arcos ◽  
M. Curé ◽  
L. Cidale ◽  
...  
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Radiation Force ◽  
Terminal Velocity ◽  
Radiative Transport ◽  
Synthetic Spectra ◽  
Transport Code ◽  
Fast Solution ◽  
Good Agreement

AbstractA new radiation-driven wind solution called δ-slow was found by Curé et al. (2011) and it predicts a mass-loss rate and terminal velocity slower than the fast solution (m-CAK, Pauldrach et al. 1986). In this work, we present our first synthetic spectra based on the δ-slow solution for the wind of B supergiant (BSG) stars. We use the output of our hydrodynamical code HYDWIND as input in the radiative transport code FASTWIND (Puls et al. 2005). In order to obtain stellar and wind parameters, we try to reproduce the observed Hα, Hβ, Hγ, Hδ, Hei 4471, Hei 6678 and Heii 4686 lines. The synthetic profiles obtained with the new hydrodynamical solutions are in good agreement with the observations and could give us clues about the parameters involved in the radiation force.

Wind inhibition in HMXBs: the effect of clumping and implications for X-ray luminosity

2018 ◽  
Vol 14 (S346) ◽  
pp. 28-33
Author(s):  
Jiří Krtička ◽  
Jiří Kubát ◽  
Iva Krtičková
Keyword(s):  
Stellar Wind ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Small Scale ◽  
Radiative Force ◽  
Ionization State ◽  
Hot Stars ◽  
X Ray ◽  
Wind Structure ◽  
Absorption Of Light

AbstractWinds of hot stars are driven by the radiative force due to absorption of light in the lines of heavier elements. Consequently, the mass-loss rate and the wind velocity depend on the ionization state of the wind. As a result of this, there is a feedback between the ionizing X-ray source and the stellar wind in HMXBs powered by wind accretion. We study the influence of the small-scale wind structure (clumping) on this feedback using our NLTE hydrodynamical wind models. We find that clumping weakens the effect of X-ray irradiation. Moreover, we show that the observed X-ray luminosities of HMXBs can not be explained by wind accretion scenario without introducing the X-ray feedback. Taking into account the feedback, the observed and estimated X-ray luminosities nicely agree. We identify two cases of X-ray feedback with low and high X-ray luminosities that can explain the dichotomy between SFXTs and sgXBs.

A Method Evaluating Fire Hazard of Multiple-Layer Cable Tray and its Validation

2017 ◽  
Author(s):  
Xianjia Huang ◽  
Kun Bi ◽  
Jun Xiao ◽  
Lan Peng ◽  
He Zhu ◽  
...  
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Zone Model ◽  
Fire Source ◽  
Multiple Layer ◽  
Cat Model ◽  
Tray Fire

Multi-layer cable tray fire has special burning characteristics that the cable flame spreads horizontally along cable tray and propagates vertically from bottom layer to upper layer at the same time. With respect of accuracy and speed of calculation, simulation of multi-layer cable tray fire remains a challenge for fire models. In this paper, a method is proposed to simulate multi-layer cable tray fire. By developing a more accurate fire source description, this method can provide accurate simulation for multi-layer cable tray fire rapidly. In this method, Firstly, the heat release rate of each burning cable tray is evaluated by FLASH-CAT model. Based on the results from FLASH-CAT, a more accurate fire source definition for multiple lay cable tray is developed for zone model. Taking account of each burning cable tray considered as one fire source point, zone model is applied to predict the fire dynamics process. In order to validate this method, four-layer cable tray fire experiments and replicated experiments were carried out in a confined compartment. The histories of mass loss rate of cable tray and temperatures at the middle of compartment were recorded during the cable fire. From the replicated experimental results of total mass loss rate, it is concluded that the four-layer cable tray fire experiment has good repetition in this scenario. Vertical temperature profile shows that the fire circumstance generated by multiple-layer cable tray burning can be divided into upper hot layer and lower cool layer, which conforms to the basic assumption of zone model. As a consequence, the zone model can be applied to simulating multiple-layer cable tray fire. By comparing the experimental total heat release rate with predictions, it is found that characteristics of multiple-layer cable tray fire are well captured. On account of good prediction on overall heat release rate for multi-layer cable tray fire, predicted heat release rate for each burning cable layer by FLASH-CAT model is believed to be reliable. Then, each burning cable layer is set as one fire source and the heat release rate of each burning cable layer is input into zone model, respectively. The comparisons between simulations and experimental data show that the predicted upper layer temperature and lower layer temperature agree well with experimental data. As a result, it can be concluded that this method provides reliable prediction for multiple-layer cable tray fire rapidly.

scholarly journals Wind inhibition by X-ray irradiation in HMXBs: the influence of clumping and the final X-ray luminosity

2018 ◽  
Vol 620 ◽  
pp. A150 ◽  
Author(s):  
J. Krtička ◽  
J. Kubát ◽  
I. Krtičková
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Terminal Velocity ◽  
High Mass ◽  
Small Scale ◽  
X Rays ◽  
X Ray ◽  
X Ray Binaries

Context. In wind-powered X-ray binaries, the radiatively driven stellar wind from the primary may be inhibited by the X-ray irradiation. This creates the feedback that limits the X-ray luminosity of the compact secondary. Wind inhibition might be weakened by the effect of small-scale wind inhomogeneities (clumping) possibly affecting the limiting X-ray luminosity. Aims. We study the influence of X-ray irradiation on the stellar wind for different radial distributions of clumping. Methods. We calculate hot star wind models with external irradiation and clumping using our global wind code. The models are calculated for different parameters of the binary. We determine the parameters for which the X-ray wind ionization is so strong that it leads to a decrease of the radiative force. This causes a decrease of the wind velocity and even of the mass-loss rate in the case of extreme X-ray irradiation. Results. Clumping weakens the effect of X-ray irradiation because it favours recombination and leads to an increase of the wind mass-loss rate. The best match between the models and observed properties of high-mass X-ray binaries (HMXBs) is derived with radially variable clumping. We describe the influence of X-ray irradiation on the terminal velocity and on the mass-loss rate in a parametric way. The X-ray luminosities predicted within the Bondi-Hoyle-Lyttleton theory agree nicely with observations when accounting for X-ray irradiation. Conclusions. The ionizing feedback regulates the accretion onto the compact companion resulting in a relatively stable X-ray source. The wind-powered accretion model can account for large luminosities in HMXBs only when introducing the ionizing feedback. There are two possible states following from the dependence of X-ray luminosity on the wind terminal velocity and mass-loss rate. One state has low X-ray luminosity and a nearly undisturbed wind, and the second state has high X-ray luminosity and exhibits a strong influence of X-rays on the flow.

scholarly journals The nature of V861 Sco (=HD 152667)

1981 ◽  
Vol 59 ◽  
pp. 481-486
Author(s):  
Ian D. Howarth ◽  
R. Wilson
Keyword(s):  
Light Curve ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Curve Analysis ◽  
Physical Parameters ◽  
Evolutionary Models ◽  
Light Curve Analysis ◽  
Phase Dependence ◽  
Large Phase ◽  
Good Agreement

AbstractThe physical parameters of the components of V861 Sco are derived from light-curve analysis and published spectroscopy. Good agreement with evolutionary models is obtained. The stellar wind is investigated using IUE data; the results include no large phase dependence of the mass loss rate and insensitivity of the velocity of the wind (measured with respect to interstellar lines) to changes in the photospheric velocity, even near the base of the wind. However, small random changes in velocity near the base of the wind are amplified to larger changes further out.

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