Safe Separation Distance Research Articles

The impact of horizontal projections on lateral fire spread in multi-unit residential buildings - comparison of numerical and similarity correlations

Balconies and horizontal projections on building façades can affect the hazard of external fire plumes. The impingement of a fire plume beneath a horizontal projection results in the radial extension of flame, which may increase the likelihood of lateral fire spread along the facade. Continuous balconies in multi-unit residential buildings (MURBs) often lack fire separation between units. Without a fire separation, an external fire plume can produce an intense heat flux on the façade. Unprotected openings in the façade can often be found in close proximity, which presents a path for exterior fire spread to adjacent compartments. Fire Dynamics Simulator (FDS) was used to predict the heat flux imposed on façades, with and without horizontal projections. Predictions achieved close agreement to experiments and empirically derived equations. Results show the presence of horizontal projections can significantly increase heat flux at greater distances along the facade. The hazard of lateral fire spread to adjacent compartments can be reduced by defining a safe separation distance between openings or the use of fire separation on balconies between compartments.

Statistical Properties and Airspace Capacity for Unmanned Aerial Vehicle Networks Subject to Sense-and-Avoid Safety Protocols

Random mobility models (RMMs) capture the random mobility patterns of mobile agents, and have been widely used as the modeling framework for the evaluation and design of mobile networks. All existing RMMs in the literature assume independent movements of mobile agents, which does not hold for unmanned aircraft systems (UASs). In particular, UASs must maintain a safe separation distance to avoid collision. In this paper, we propose a new modeling framework of random mobility models equipped with physical sense-and-avoid protocols to capture the flexible, variable, and uncertain movement patterns of UASs subject to separation safety constraints. For the random direction (RD) RMM equipped with a commonly used sense-and-avoid (S&A) protocol, named sense-and-stop (S&S), we provide its statistical properties including stationary location distribution and stationary inter-vehicle distance distribution, using the Markov analysis. This study provides knowledge on the impact of S&A protocols to critical UAS networking statistics. In addition, we define collision probabilities and airspace capacity concepts for UASs based on the inter-vehicle distance distribution, and derive their closed-form expressions. This analytical framework mathematically bridges local autonomy with global airspace capacity, and allows the impact analysis of local autonomy configurations for effective UAS airspace capacity management.

Advanced dynamic modeling study of fire and smoke of crude oil storage tanks

The combustion properties of large-scale crude oil pool fire have great significance for security design and firefighting of current crude oil reserves. Burning rate, flame shape and radiation intensity are the most important parameters for fire properties. The novelty of this study is that the Fire Dynamics Simulator (FDS) is adopted to simulate pool fires in a tank farm. It does not only investigate and analyze heat radiation flux, but also the temperature difference rise and flame/smoke temperature contours behavior. This simulation is performed in order to predict the potentials of a large crude oil storage tank fire outbreak and the smoke temperature distribution that counters in and around the tank. These data are used in designing tank farms and applying the firefighting strategy. A super CPU with large RAM is used to operate the simulation program, to simulate one of the largest crude oil farms in the world. The model will be investigated for identifying the worst-case scenarios that might occur in a large crude oil tank. One of these scenarios might be fire outbreak in rim seal in one of the four storage tanks, where the fire is transferred to full surface fire. The model predicts the potential of tank fire outbreak, smoke tracing and both smoke/flame temperature that spreads at wind speed of 3 m/s, 9 m/s, 18 m/s in south-west direction. FDS model provides qualitative data that increase the level of safety, such as the minimum safe separation distances and the location of firefighters during the firefighting process. It also determines the most critical area, which is needed for water-cooling system. This study also tackles the duration after which human beings feel pain after being exposed to heat radiation.

Optimization-Based Distributed Flocking Control for Multiple Rigid Bodies

This letter considers distributed flocking control on the Special Euclidean group for networked rigid bodies. The method captures the three flocking rules proposed by Reynolds: cohesion; alignment; and separation. The proposed controller is based only on relative pose (position and attitude) information with respect to neighboring rigid bodies so that it can be implemented in a fully distributed manner using only local sensors. The flocking algorithm is moreover based on pose synchronization methods for the cohesion/alignment rules and achieves safe separation distances through the application of control barrier functions. The control input for each rigid body is chosen by solving a distributed optimization problem with constraints for pose synchronization and collision avoidance. Here, the inherent conflict between cohesion and separation is explicitly handled by relaxing the position synchronization constraint. The effectiveness of the proposed flocking algorithm is demonstrated via simulation and hardware experiments.

Attenuation of rotavirus, MS2 bacteriophage and biomolecule-modified silica nanoparticles in undisturbed silt loam over gravels dosed with onsite wastewater

Contamination of potable groundwater by pathogenic viruses from on-site wastewater treatment systems (OWTS) poses a serious health risk. This study investigated the attenuation and transport of rotavirus, bacteriophage MS2 and DNA-labelled-glycoprotein-coated silica nanoparticles (DGSnp) in 2 intact cores of silt loam over gravels dosed with wastewater from an OWTS at 3.53 L/day. To simulate a worst-case scenario, experiments were conducted under saturated conditions. The results from 6 experiments demonstrated that the rotavirus and DGSnp reductions were very similar and markedly greater than the MS2 reduction. This was reflected in the peak concentrations, relative mass recoveries, and temporal and spatial reduction rates. For a given log10 reduction, the estimated soil depth required for MS2 was over twice that required for rotavirus and DGSnp. This is the first study in which DGSnp was used as a rotavirus surrogate in soil under wastewater applications. Consistent with previous studies, DGSnp showed promise at mimicking rotavirus attenuation and transport in porous media. The results suggest DGSnp could be used to assess the attenuation capacity of subsurface media to rotavirus. However, DGSnp is not conservative and will underestimate the setback distances required for rotavirus reductions by 3%. On the other hand, separation distances determined using the rotavirus parameters and criteria but based on MS2 attenuation, can be too conservative in some subsurface media. To determine safe and realistic separation distances, it would be beneficial and complementary to apply both conservative virus surrogate using MS2 bacteriophage and representative but non-conservative new virus surrogates using biomolecule-modified silica nanoparticles.

Computational fluid dynamics (CFD) study of heat radiation from large liquefied petroleum gas (LPG) pool fires

Liquefied petroleum gas (LPG) is flammable and has risks of pool fires during its transportation, storage, and applications. The heat radiation by LPG pool fires poses hazards to individuals nearby and can lead to potential failures of ambient facilities. Due to the high costs and invasive nature of experiments for investigating large-scale pool fires, computational fluid dynamics (CFD) is employed in this study as the cost-effective and noninvasive method to simulate the process and analyze the characteristics of large hydrocarbon pool fires. Specifically, an experimentally validated 3-D CFD model has been built to simulate surface emissive power (SEP) and incident radiation of large-scale LPG pool fires with three different diameters and wind speeds. Steady-state simulations with P1 radiation and probability density function (PDF) combustion models were employed to obtain reliable data after the optimizations based on the comparisons with experimental data and empirical models. The comparison with benchmark experimental data demonstrates that the CFD model employed in this study can accurately predict the incident radiation of large LPG pool fires. A new SEP correlation is also proposed, which is specifically for LPG pool fires with a diameter between 10 m and 20 m. Additionally, the safe separation distances between LPG facilities and surrounded objects have been estimated based on the CFD simulation results. The high-resolution CFD model for large LPG pool fires in this work provides noninvasive and direct quantitative evidence to enhance the fundamental understanding on the safety of large LPG pool fires and can assist regulatory agencies in refining the safety limits in the cost-effective and time-saving manners.

Optimal Safe Layout of Fuel Storage Tanks Exposed to Pool Fire: One Dimensional Deterministic Modelling Approach

Fire hazard is one of the main risks associated to fuel storage tanks in petroleum and in the petrochemical industries. Such a hazard includes pool fires in the storage tanks or in the bunds, fire propagation from the source tank to target tanks both in absence and in presence of wind, and also the cascading/domino effect due to confined and unconfined vapour cloud explosion and or BLEVE associated with the source tank. In the present work, a radiation shield of flowing water has been introduced at a distance from the source fuel storage tank to prevent the domino effect originating from this source tank, under fire, to the target fuel storage tanks in a tank farm. A simple one dimensional model has been developed from the steady state energy balance to simulate the safe distances (i.e. rim–rim distance) between fuel storage tanks containing class-I fuel (e.g. gasoline), both in presence and absence of a water-shield under no-wind and cross-wind conditions. The model predictions have shown that the maximum safe inter-tank separation distance of 28.42 m is anticipated at a wind velocity of 6 m/s, compared to 16.34 m in no-wind condition, beyond which the centroid of the parallelepiped (a solid-flame geometry) falls outside the base of the tilted flame geometry causing flattening of flame and a very sluggish increase in the flame tilt angle as the inverse of the Richardson number in the presence of wind velocity vector increases. Furthermore, the present one dimensional mathematical model has also been extended to show that introduction of a water-shield with an appropriate thickness (δopt) is able to prevent the propagation of radiation heat flux under both no-wind and cross-wind conditions to a much lower distance close to 8.34 m between tanks (measured from the centre of the source tank), than those predicted from the existing empirical models; viz. Point Source model and Shokrie-Beyler’s model.

Consequence analysis of large-scale pool fire in oil storage terminal based on computational fluid dynamic (CFD)

In this study, the Fire Dynamics Simulator (FDS) is adopted to simulate tank and dike pool fires in a tank farm. These simulations are performed in order to evaluate the potential for secondary fire events in nearby storage tanks based on the resulting incident radiative heat flux. As a precursor to the tank farm fire scenario case studies, the model is compared with experimental data of 1 m crude oil pool fire and 30 m and 50 m diameter kerosene pool fires. These comparisons are made to validate the modeling approach ahead of the application of the modeling to a problem of practical interest. The results of the FDS are consistent with experimental data. The FDS results indicate that the studied dike pool fire has the potential of triggering the domino effects in the tank farm, but not so true in the case of the tank fire. Quantitative results obtained by FDS modeling can be used in quantitative risk assessment of a tank farm and determination of safe inter-tank separation distances.

Concurrent co-location maneuver planning for geostationary satellites

This paper details the development of a planning algorithm for multiple co-located geostationary satellites to perform station keeping and momentum unloading maneuvers concurrently. The objective is to minimize the overall fuel consumption while guaranteeing a safe separation distance between the satellites within a specific geostationary slot, as well as managing their stored angular momentum to maintain their nadir pointing orientation. The algorithm adopts the leader-follower architecture to define relative orbital elements of the satellites equipped with four gimbaled on-off electric thrusters, and solves a convex optimization problem with inequality constraints, including momentum unloading requirements, to determine the optimal maneuvers. The proposed algorithm is verified, in terms of fuel consumption, constraints enforcement and satellites performance, using numerical simulations that take into account dominant perturbations in the geostationary environment.

Design safe distance between a buried pipe and a soil slope

Leakage from pipes buried in a soil slope can lead to failure and scour of the slope. Placing the pipe at a safe distance from the slope crest is a key concern in design. The objectives of the work reported here were to investigate the wetting front advancement in a soil slope due to leakage from buried pipes at variable distances from the slope crest considering different soil densities and boundary conditions of the slope, and to recommend a safe separation distance based on the relation between the factor of safety of the slope and the separation distance. Stability charts for slopes were established for different separation distances and infiltration times, which will serve as a guide to determining a safe separation distance. The safe distance depends on soil permeability, slope geometry and infiltration time. A safe distance, regardless of how long the leakage is expected to last, is recommended as twice the slope height for soil slopes 15 m in height and 35° in inclination compacted to 95% relative compaction under impermeable side and bottom boundary conditions. When a pipe is laid within this distance, the ability to detect and repair pipe leakage in a timely manner becomes an essential means of maintaining slope stability.

Lab-scale observations of flame attachment on slopes with implications for firefighter safety zones

The Coanda effect is the phenomenon in which a jet entering quiescent fluid attaches to a nearby solid object due to inhibited entrainment of ambient fluid near the solid. Little is known about the influence of the Coanda effect on wildland fire behavior. Specifically, there is a lack of knowledge regarding how the flame attachment on slopes influences firefighter safety zone considerations in rugged terrain. This paper presents results for small-scale n-heptane pool fire experiments near a slope, showing how flame shape and heat flux are influenced by slope angle, slope boundary condition and distance from flame base. Flames near slopes leaned toward the slope, and at some slope angles the flames attached to the slope. The average angle at which the effects of slope were noticeable was between 10° and 45°, depending on the criteria used. No difference was observed between a bare slope and an insulated slope. Dimensional analysis showed that important characteristics of flame attachment on slopes in the small-scale experiments were in the range estimated for the large fires. The implication is that the traditional view of safe separation distance as being the distance from the flame base is inadequate for fires near slopes.

EFFECTS OF LAUNCHING PARAMETERS ON THE SEPARATION TRAJECTORY OF INTERNAL WEAPONS

A simplified buried weapon bay-door-missile model was simulated with Improved Delayed Detach Eddy Simulation (IDDES) method and dynamic grid technique under the condition of different inflow Mach numbers, launching speeds and initial angular velocities. The separation trajectory varying patterns of different cases were obtained. The results show that, in subsonic flow, the Mach number has little effect on the yaw angle, while under transonic and supersonic conditions, the missile yaws to the right due to the influence of shock waves. The increase in the Mach number leads to the reduction of missile yaw and pitch angle for supersonic inflow. Raising the launching speed can make the store reach safe separation distance faster and diminish store angular variation. Increasing the initial angular velocity of the missile can reduce the pitch angle and increase the separation speed of the missile without changing the ejection force.

Simulation of fire spread between residential buildings regarding safe separation distance

Simulation of fire spread between residential buildings regarding safe separation distance

Flight Performance Optimization of a Multilift Rotorcraft Formation

A numeric optimization is performed for maximizing the cruise performance of a multilift rotorcraft system. The optimization process locates the optimal relative positions of the formation rotorcraft. The optimization problem is formulated as a constrained nonlinear programming problem. Constraints on the distances between the formation rotorcraft are imposed in order to maintain safe separation distances. It is shown that, for every airspeed, an optimal formation geometry can be found that minimizes the rotorcraft power required. An optimization analysis for subsequent airspeeds yields an optimal recommended airspeed that is close to the “bucket” airspeed of the unloaded rotorcraft. The cable length is shown to have a secondary influence on optimization results. The improvement in the resulting multilift mission performance is demonstrated using a nonlinear simulation of the system. It is shown that the operational efficiency of the system can be significantly increased by adopting the optimization results.

Systems-Theoretic Process Analysis of Maritime Traffic Safety Management in the Gulf of Finland (Baltic Sea)

According to International Maritime Organization (IMO), the Baltic Sea Area has some of the densest maritime traffic in the world. The Baltic Sea was designated a Particularly Sensitive Sea Area (PSSA) at IMO Marine Environment Protection Committee's 53rd session in July 2005. The Mandatory Ship Reporting System in the Gulf of Finland Traffic Area (GOFREP) was established by IMO in 2003 and has been in operation since 2004. The objective of this study in progress is 1) to outline the hierarchical structure of the maritime navigation safety management system from European to ship onboard level and 2) to apply the Systems-Theoretic Process Analysis (STPA) to identify system level hazards and potentially unsafe ship speed and maneuvering control actions with respect to IMO Collision Regulations (COLREGs) Rules on ship safe speed, ship safe separation distances and the Traffic Separation Schemes requirements with the aim of evaluating the effective hazard control options to enable efficient updating of ship level situational awareness and the enforcement of safety constraints in real time.

Safe separation distance score: a new metric for evaluating wildland firefighter safety zones using lidar

ABSTRACTSafety zones are areas where firefighters can retreat to in order to avoid bodily harm when threatened by burnover or entrapment from wildland fire. At present, safety zones are primarily designated by firefighting personnel as part of daily fire management activities. Though critical to safety zone assessment, the effectiveness of this approach is inherently limited by the individual firefighter’s or crew boss’s ability to accurately and consistently interpret vegetation conditions, topography, and spatial characteristics of potential safety zones (e.g. area and geometry of a forest clearing). In order to facilitate the safety zone identification and characterization process, this study introduces a new metric for safety zone evaluation: the Safe Separation Distance Score (SSDS). The SSDS is a numerical representation of the relative suitability of a given area as a safety zone according to its size, geometry, and surrounding vegetation height. This paper describes an algorithm for calculating pixel-based and polygon-based SSDS from lidar data. SSDS is calculated for every potential safety zone within a lidar dataset covering Tahoe National Forest, California, USA. A total of 2367 potential safety zones with an SSDS ≥1 were mapped, representing areas that are suitable for fires burning in low wind and low slope conditions. The highest SSDS calculated within the study area was 9.65, a score that represents suitability in the highest wind-steepest slope conditions. Potential safety zones were clustered in space, with areas in the northern and eastern portions of the National Forest containing an abundance of safety zones while areas to the south and west were completely devoid of them. SSDS can be calculated for potential safety zones in advance of firefighting, and can allow firefighters to carefully compare and select safety zones based on their location, terrain, and wind conditions. This technique shows promise as a standard method for objectively identifying and ranking safety zones on a spatial basis.

On an analytical model of wake vortex separation of aircraft

ABSTRACTA theory is presented on the effect of wake turbulence of a leading aircraft on the roll stability of a following aircraft, leading to a simple formula for the safe separation distance between the two aircraft that provides estimates of aircraft separation distances comparable to existing empirical regulations, based on experience. The formula includes the effects of flight and atmospheric conditions, and the characteristics of the leading and following aircraft; it applies to similar or dissimilar aircraft, and it indicates the parameters and conditions leading to increasing or decreasing separation. The formula is applied not only to the three International Civil Aviation Organization (ICAO) categories of aircraft (light, medium and heavy, respectively, Cessna Citation, B737 and B747) but also to ‘special’ aircraft requiring larger separation distance (Boeing 757) and to the world’s largest airliner (Airbus A380).

A STUDY OF SEISMIC POUNDING EFFECT BETWEEN ADJACENT BUILDINGS AND ITS MITIGATION BY USING DIFFERENT TYPE OF BRACING SYSTEMS

Investigation of previous and recent earthquake damage have shown that the buildings are subjected to severe destruction or collapse during the earthquake ground motion. Among the probable structural damages, seismically induced pounding has been usually witnessed in most of the earthquakes. During the earthquake, Building vibrates out phase due there different dynamics characteristics. Such buildings are usually separated by expansion joint which is insufficient to accommodate the lateral movements of the buildings during the earthquake. Seismic pounding can be prevented by providing safe separation distances; sometimes availability of required safe separation gap is not possible in metropolitan cities due to high land value and limited availability of land. If building separation is found to be deficient to prevent pounding, then there should be some easy and cost-effective methods to prevent structural pounding between adjacent buildings. This study covers the effect of structural pounding on conventional beam column system adjacent to flat slab system .In order to observe pounding effect, Time history analysis is carried out by taking 1944 Elcentro earthquake data which is to be known as above average earthquake. This study also covers the prevention techniques of pounding by using retrofitting’s like introducing X cross bracings, Eccen forward and backward cross bracing, V cross bracing systems with proper placement are proposed as possible mitigation techniques for pounding between adjacent structures

Analysis of safe distance of flue from combustible construction parts in terms of fire safety in the European standards

This topic is very actual due to the high number of chimney and flue fires, including radiators especially during the heating season. The aim of the article is to compare and assess the strictness of the regulations in selected European countries in terms of safe separation distance of the flue from the combustible construction parts.

Vertical safe separation distance between openings in multi-storey buildings having a fire resistant spandrel

A novel comprehensive methodology is presented for the determination of the vertical separation distance between floor glazing openings in buildings having a fire resistant non-flammable spandrel. The spandrel height is specified by requiring that the heat flux is less than a critical heat flux for glazing failure at the base of the opening of the floor above the floor of fire origin. For a specified room, opening geometries and fuel type, the heat flux at the base of this opening is calculated by using correlations for the flame height and heat flux distribution of the facade flames for under ventilated fire conditions in the compartment of fire origin. As the compartment opening increases a transition occurs from under ventilated to over ventilated conditions reducing the facade fire spread hazard. The methodology and results can also be applied for wooden and lightweight facade walls to predict fire spread behavior on the wall and towards the openings to floors above the floor of fire origin. © Owned by the authors, published by EDP Sciences, 2016 Language: en