Spill Plumes Research Articles

A new approach to smoke control systems in complex atria

Large occupied spaces such as the atria can have additional internal elements like balconies, stairs, or decorations. Unfortunately, detailed design rules for smoke management systems are lacking in these large contemporary spaces. A series of smoke tests and CFD simulations were conducted to address this shortfall. The project’s first step was realised with full-scale hot smoke tests in Smoke Laboratory, which allowed the observation of a significant influence of the suspended balconies on smoke mass production. CFD simulations confirmed the preliminary observations and were used to evaluate this phenomenon quantitatively. This proved that the wider the balcony, the greater the mass increase. The same fire scenarios were examined with theoretical NFPA 92 correlations dedicated to axisymmetric and balcony spill plumes. They showed that using the standard axisymmetric plume correlation in a complex atrium could lead to a strong underprediction of the required smoke control system parameters. A proposed adapted balcony spill plume correlation can improve the smoke mase calculations. Practical application This study demonstrates that existing standards like NFPA 92 NFPA 204, or BS 7346-4. Do not cover the need for smoke control systems in complex and irregular atria solutions, which often appear in modern buildings. It has been proven that the obstructions in the atrium space significantly influence the smoke mass production. As a consequence, using the original axisymmetric plume correlation in a complex atrium could lead to a strong underprediction of smoke control system requirements. The authors proposed a new correlation for the approach to smoke control systems parameters approach at the design process.

Transport phenomena of fire-induced smoke flow in a semi-open vertical shaft

PurposeThe purpose of this study is to investigate the transport phenomena of smoke flow in a semi-open vertical shaft.Design/methodology/approachThe large eddy simulation (LES) method was used to model the movement of fire-induced thermal flow in a full-scale vertical shaft. With this model, different fire locations and heat release rates (HRRs) were considered simultaneously.FindingsIt was determined that the burning intensity of the fire is enhanced when the fire attaches to the sidewall, resulting in a larger continuous flame region in the compartment and higher temperatures of the spill plume in the shaft compared to a center fire. In the initial stage of the fire with a small HRR, the buoyancy-driven spill plumes incline toward the side of the shaft opposite the window. Meanwhile, the thermal plumes are also directed away from the center of the shaft by the entrained airflow, but the inclination diminishes as HRR increases. This is because a greater HRR produces higher temperatures, resulting in a stronger buoyancy to drive smoke movement evenly in the shaft. In addition, a dimensionless equation was proposed to predict the rise-time of the smoke plume front in the shaft.Research limitations/implicationsThe results need to be verified with experiments.Practical implicationsThe results could be applied for design and assessment of semi-open shafts.Originality/valueThis study shows the transport phenomena of smoke flow in a vertical shaft with one open side.

Fire spill plume from a compartment with dual symmetric openings under cross wind

This paper presents a comprehensive theoretical and experimental study on the fire spill plume from a compartment with dual symmetric openings under cross wind. Experiments of spill plume were performed at the outlet of a wind tunnel using a bench-scale compartment with a leeward façade wall and dual symmetric openings. The experimental fire compartment was well-mixed. The effect of wind is theoretically elucidated by derivations on the pressure differences between inside and outside. The neutral planes for the two openings are theoretically formulated and compared with those in single-opening and no-wind case. The formulations of the neutral plane heights are verified by using video image analysis and velocity data regression analysis. Also a new method using the data of wind speed and neutral plane height in no-wind case is proposed to determine the neutral plane heights for higher wind speeds. The results suggest that the neutral plane heights vary monotonically with cross wind speed. Two new length scales with variable neutral plane heights are proposed by theoretical derivations to develop scaling models of spill plume. It is indicated that the new length scales are applicable to correlate the axial plume temperature and the total heat flux along the façade. The radial temperature profiles of spill plumes are well described by a Gaussian function normalized by the temperature radius, which is independent on the wind speed. It is found that wind enhances the air entrainment of spill plume in both the near and far fields, thereby the transition from continuous flame, intermittent flame to buoyant plume is accelerated. The data of total heat flux and temperature distribution along the façade indicate that cross-wind has two competitive effects on the heat transportation from the spill plume to the façade.

Ocean current estimation using a Multi-Model Ensemble Kalman Filter during the Grand Lagrangian Deployment experiment (GLAD)

In the summer and fall of 2012, during the GLAD experiment in the Gulf of Mexico, the Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE) used several ocean models to assist the deployment of more than 300 surface drifters. The Navy Coastal Ocean Model (NCOM) at 1km and 3km resolutions, the US Navy operational NCOM at 3km resolution (AMSEAS), and two versions of the Hybrid Coordinates Ocean Model (HYCOM) set at 4km were running daily and delivering 72-h range forecasts. They all assimilated remote sensing and local profile data but they were not assimilating the drifter’s observations. This work presents a non-intrusive methodology named Multi-Model Ensemble Kalman Filter that allows assimilating the local drifter data into such a set of models, to produce improved ocean currents forecasts. The filter is to be used when several modeling systems or ensembles are available and/or observations are not entirely handled by the operational data assimilation process. It allows using generic in situ measurements over short time windows to improve the predictability of local ocean dynamics and associated high-resolution parameters of interest for which a forward model exists (e.g. oil spill plumes). Results can be used for operational applications or to derive enhanced background fields for other data assimilation systems, thus providing an expedite method to non-intrusively assimilate local observations of variables with complex operators. Results for the GLAD experiment show the method can improve water velocity predictions along the observed drifter trajectories, hence enhancing the skills of the models to predict individual trajectories.

Predicting Spill Plumes with the Fire Risk Zone Model B-RISK

Recent experimental research on spill plume entrainment has developed a range of empirically-based formulae for smoke management design. These formulae form the spill plume entrainment model in B-RISK, a new fire risk zone model. This article describes the performance of B-RISK in predicting spill plume entrainment. Selected experimental data from the series of reduced-scale experiments used to form the new design formulae have been used for model validation, along with other full-scale experimental data from ‘hot smoke tests’ conducted to assess the performance of installed smoke management systems. B-RISK provides predictions of the plume clear-layer height that generally agree with experimental results within the range of experimental error. This gives confidence in its use to predict spill plume entrainment for smoke management design purposes.

Numerical study of smoke extraction for adhered spill plumes in atria: Impact of extraction rate and geometrical parameters

In case of fire in an atrium, a smoke and heat control (SHC) system can be designed to improve safety inside the atrium. An important design criterion is the smoke free height in the atrium. This smoke free height is the result of a number of parameters, of which the fire heat release rate (HRR), the SHC extraction mass flow rate, the position of the extraction device or opening and the size and position of openings for make-up air are of primary importance. In the present paper, an extensive numerical study, based on computational fluid dynamics (CFD), is presented in which these parameters are varied. The presence of a downstand or balcony is not covered in the study at hand. From the results, a correlation is presented for adhered spill plumes in atria without downstand, relating the smoke extraction rate to the smoke free height in the atrium. The smoke layer in the atrium is illustrated to become multi-dimensional beyond a certain threshold value of the smoke extraction rate and existing correlations, which do not take this phenomenon into account, are not conservative. The position and exact size of the make-up air inlet openings are shown not to affect the observations, as long as the openings are sufficiently large.

Constructing a Distributed AUV Network for Underwater Plume-Tracking Operations

In recent years, there has been significant concern about the impacts of offshore oil spill plumes and harmful algal blooms on the coastal ocean environment and biology, as well as on the human populations adjacent to these coastal regions. Thus, it has become increasingly important to determine the 3D extent of these ocean features (“plumes”) and how they evolve over time. The ocean environment is largely inaccessible to sensing directly by humans, motivating the need for robots to intelligently sense the ocean for us. In this paper, we propose the use of an autonomous underwater vehicle (AUV) network to track and predict plume shape and motion, discussing solutions to the challenges of spatiotemporal data aliasing (coverage versus resolution), underwater communication, AUV autonomy, data fusion, and coordination of multiple AUVs. A plume simulation is also developed here as the first step toward implementing behaviors for autonomous, adaptive plume tracking with AUVs, modeling a plume as a sum of Fourier orders and examining the resulting errors. This is then extended to include plume forecasting based on time variations, and future improvements and implementation are discussed.

On adhered spill plume entrainment

The weak rectangular plume formulation of Kumar, Cox and Thomas [1] for unconstrained spill plumes is here modified for application to “adhered” plumes. This simple treatment provides a natural theoretical description of the transition from two to three dimensional flow in contrast to the recent correlations of Harrison and Spearpoint [2]. Reasonable agreement with Harrison’s [3] data is demonstrated using the same entrainment coefficient as for the free plume [1].

A comparison between channelled and unchannelled balcony spill plumes

The use of channelling screens in smoke management design can reduce balcony spill plume entrainment by restricting smoke spread under the balcony. The omission of channelling screens can gave rise to a greater lateral extent resulting in a change in the entrainment conditions. This work provides new experimental data using physical scale modelling to enable a comparison between channelled and unchannelled plumes. The lateral spread for unchannelled plumes was found to be dependent upon the velocity of the flow from the fire compartment opening. The measured entrainment for plumes without screens was greater than that from equivalent plumes with screens and the relative difference in entrainment increased as the width of the fire compartment opening decreased. A simple approximation to predict entrainment for unchannelled plumes from wide fire compartment openings is proposed. Practical application: The ability to determine amount of entrainment from a balcony spill plume is important to fire engineers involved in smoke management design. Whether channelling screens are part of the design will likely affect this entrainment. This article presents a simple approximation that can be used to predict entrainment for unchannelled plumes from wide fire compartment openings building on previous work by Law.

Air entrainment into balcony spill plumes

New plume formulations have been developed for assessing air entrainment into thermal plumes that spill over a balcony edge into an atrium void. A simple weak rectangular plume treatment is developed to incorporate the effects of entrainment into plume ends. This is shown to be asymptotic to two dimensional, line plume (near the balcony) and three dimensional axisymmetric plume limits (in the far field). In addition a strong curved plume analysis that also includes the influences of the horizontal momentum of the smoke layer at the balcony edge is developed. The results of the analytical formulations have been compared with Harrison’s new comprehensive experimental data [1] and with CFD predictions from the JASMINE CFD model. It is shown that a virtual line source located a distance approximately three layer depths below the balcony edge provides a reasonably good description of mass fluxes for plumes with and without end entrainment. It is concluded that for practical engineering application, a simple rectangular plume treatment describes the transition from two- to three dimensional flow sufficiently well to be a simple option for the inclusion of end effects.

Physical scale modelling of adhered spill plume entrainment

This work provides new experimental data to characterise entrainment of air into adhered thermal spill plumes using physical scale modelling. For the two-dimensional plume, the rate of entrainment with respect to height of rise is approximately half that of an equivalent two-dimensional balcony spill plume. For the three-dimensional plume, the rate of entrainment appears to be linked to the plume behaviour, which has been characterised in terms of the width and depth of the layer flow below the spill edge. In general, a layer flow below the spill edge that is shallow compared to its width will tend to adhere to the wall above the opening compared to flows whose depth approaches its width. This work proposes new empirical entrainment design formulae that have been developed on a more general basis compared to existing methods.

Application of FDS to Adhered Spill Plumes in Atria

In a recently published article (Poreh et al., Fire Saf J 43(5):344-350, 2008), Poreh et al. carried out a number of experiments in a small-scale atrium. They investigated the mass flow of the spill plume in case of fire emerging from an adjacent room or corridor. Based on these experiments, the equation for the mass flow rates of adhered spill plumes in atria was adjusted. In our article, we repeat the experiments in a computational fluid dynamics (CFD) program. The results agree well, both with the experiments and the suggested formula. After this first validation, large-scale CFD-simulations are carried out. It appears that the equation suggested by Poreh et al. is only valid in the case of a uniform smoke layer depth. If the smoke layer has a more complex configuration, the formula is no longer reliable for the design of the smoke and heat exhaust ventilation system.

A critical study on fire-induced aerodynamics of balcony spill plumes

Balcony spill plume is one of the main plume forms in an atrium fire, its thermal behavior which is important to the designers for the smoke control system design is still not well understood now. The fire-induced aerodynamics of balcony spill plume would be studied by the numerical method in this paper. Some uncertainties relating to the available calculation methods for the smoke production rate would be reexamined. Numerical results indicated that using an entrainment coefficient 0.11 would be better than 0.16 in describing the entrainment behavior, end effect should not be ignored for the plume being not two-dimensional (2-D). Suitable empirical spill plume equations would be recommended for the smoke management system design.

A Comparative Analysis of the Use of Different Zone Models to Predict the Mass Smoke Flow for Axisymetric and Spill Plumes

Sanderson [1]examined the theoretical basis for and the experimentation supporting the predictive smoke zone models currently being used in fire engineering design that are cited, in nationally and internationally accepted guidance documents, to support the increasing use of performance-based building codes/regulations throughout the world. This critical examination identified anomalies: 1) between different researcher’s results, when considering the same fire environment, and 2) areas where the models used in guidance documents have limited empirical support. The variance between models was examined by the parametric variation of critical data input parameters the impact of which indicated that the most recent research produced models that predict a lower level of mass smoke flow than the earlier models. It may be suggested that the more recent research, building on previous work, produces models that can be used with a greater level of confidence however there is no robust evidence to support this. This paper illustrates the variances between the model outputs by means of a case study. Currently there is a move towards the use of Computational Fluid Dynamic modelling of fire. However, given the limited validation of these models in the area of smoke movement and the computer time and power required to run these models, there is still a place in fire engineering design for the zone model. As an increasing number of countries adopt performance building and fire codes/regulations and given the consequent need for predictive mass smoke flow models in which regulators, fire engineers and society can have confidence, it is concluded that the research supporting zone modelling of fire should be extended. This research should be robust and transparent in order to either produce models that are substantially more acceptable than those currently being used or to provide more confidence in models.

Derivation of aquatic screening benchmarks for 1,2-dibromoethane.

Ethylene dibromide (1,2-dibromoethane or EDB) was primarily used in the United States as an additive in leaded gasoline and as a soil and grain fumigant for worm and insect control until it was banned in 1983. Historical releases of EDB have resulted in detectable EDB in groundwater and drinking wells, and recently concentrations up to 16 microg/L were detected in ground water at two fuel spill plumes in the vicinity of the Massachusetts Military Reservation Base on Cape Cod, Massachusetts. Because the ground water in this area is used to flood cranberry bogs for the purposes of harvesting, the U.S. Air Force sponsored the development of aquatic screening benchmarks for EDB. Acute toxicity tests with Pimephales promelas (fathead minnow), Daphnia magna, and Ceriodaphnia dubia were conducted to provide data needed for development of screening benchmarks. Using a closed test-system to prevent volatilization of EDB, the 48-h LC50S (concentration that kills 50% of the test organisms) for P. promelas, D. magna, and C. dubia were 4.3 mg/L, 6.5 mg/L, and 3.6 mg/L, respectively. The screening benchmark for aquatic organisms, derived as the Tier II chronic water quality criteria, is 0.031 mg EDB/L. The sediment screening benchmark, based on equilibrium partitioning, is 2.45 mg EDB/kg of organic carbon in the sediment. The screening benchmarks developed here are an important component of an ecological risk assessment, during which perhaps hundreds of chemicals must be evaluated for their potential to cause ecological harm.

Association of ethylene dibromide (EDB) with mature cranberry (Vaccinium macrocarpon) fruit.

Ethylene dibromide (EDB), a potential carcinogen, has been used in gasoline mixtures to avoid the accumulation of metallic lead in engines. Ethylene dibromide is present in the environment and in groundwater. Previous analysis has shown that EDB levels have reached up to 16 microg L-1 in the groundwater at two fuel spill plumes in the vicinity of the Massachusetts Military Reservation (MMR) Base and up to 1.69 microg L-1 in the Coonamessett and Quashnet Rivers in Cape Cod, MA (U.S. Air Force IRP, Fact Sheet #98-10, 1998). Groundwater and river water from this area are used to flood some local cranberry bogs for irrigation and harvesting of cranberry fruits. The potential sorption of EDB by cranberry fruits during harvest has caused concern but information regarding its occurrence is not available. In this study, low levels of EDB (0.04-0.15 microg kg-1) were found to be associated with cranberry fruits that were exposed to EDB at levels ranging from 3 to 12 microg L-1 at 10, 20, and 30 degrees C for up to 7 days. Rinsing EDB-exposed cranberry fruits twice with deionized water or once with 0.01 M NaCl solution reduced the amount of EDB associated with the cranberry fruits by 65-72% to a level of 0.02 microg kg-1. Therefore, the EDB most likely is associated with the water residue on the surface of the cranberry fruit rather than being absorbed into the flesh of the fruit during the EDB exposure.

Numerical simulations on balcony spill plume

Balcony spill plumes were studied by computational fluid dynamics (CFD). Reference was made to the scale model studies reported by Morgan and co-workers in which an atrium hood adjacent to a fire compartment was considered. Mechanical smoke extraction through a vertical air duct was also studied. Six sets of simulations were carried out and are reported in this paper. The computing domains of each simulation were extended outside the model geometry so that the free boundary condition could be treated properly. It was found that the free boundary conditions have to be specified carefully in carrying out CFD simulations, especially for cases where pressure distributions are important. The neutral plane heights under different extraction rates were studied. From the CFD studies, the neutral plane heights moved up when extraction rates increased. Further, a real life scenario on designing a smoke control system for a super tall atrium using CFD was briefly outlined. Copyright © 1999 John Wiley & Sons, Ltd.

Numerical simulations on balcony spill plume

Balcony spill plumes were studied by computational fluid dynamics (CFD). Reference was made to the scale model studies reported by Morgan and co-workers in which an atrium hood adjacent to a fire compartment was considered. Mechanical smoke extraction through a vertical air duct was also studied. Six sets of simulations were carried out and are reported in this paper. The computing domains of each simulation were extended outside the model geometry so that the free boundary condition could be treated properly. It was found that the free boundary conditions have to be specified carefully in carrying out CFD simulations, especially for cases where pressure distributions are important. The neutral plane heights under different extraction rates were studied. From the CFD studies, the neutral plane heights moved up when extraction rates increased. Further, a real life scenario on designing a smoke control system for a super tall atrium using CFD was briefly outlined. Copyright © 1999 John Wiley & Sons, Ltd.

Entrainment by two-dimensional spill plumes

Abstract A simple model is proposed for estimating the mass entrainment into two-dimensional (2D) free plumes. The model rests on the assumption that the entrainment into the curved section of a spilling plume is approximately equal to the entrainment into a vertical free plume rising through the same height. The model is shown to be in good agreement with measurements in several small-scale models. The measured entrainment coefficient for the 2D plumes in the scale model studies, which had been determined from measurements of entrainment into the vertical portion of those plumes, was found to be around C m =0·44, slightly below recently proposed values for unbounded 2D plumes. It is suggested that the observed deviations from the proposed model of measurements in two small-scale models of atria might have been caused by the relatively small size or shape of those atria.