scholarly journals CFD Simulation and Mitigation with Boiling Liquid Expanding Vapor Explosion (BLEVE) Caused by Jet Fire

2018 ◽  
Vol 3 (1) ◽  
pp. 1 ◽  
Author(s):  
Alon Davidy
Keyword(s):  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Heat Fluxes ◽  
Heat Transfer Analysis ◽  
Superheated Liquid ◽  
Vapor Explosion ◽  
Fire Dynamics ◽  
Boiling Liquid ◽  
Eddy Simulation ◽  
The People

Different kinds of explosions are driven by the internal energy accumulated in compressed gas or superheated liquid. A well-known example of such an explosion is the burst of a vessel with pressure-liquefied substance, known as Boiling Liquid Expanding Vapor Explosion (BLEVE). Hot BLEVE accident is caused mainly by direct heating (pool fire or jet fire) of the steel casing at the vapor side of the tank to temperatures in excess of 400 °C. Thermal insulation around the tank can significantly reduce and retard the excessive heating of the tank casings in a fire. This will allow fire fighters enough time to reach the accident location and to cool the LPG (Liquid Petroleum Gas) tank to avoid the BLEVE, to extinguish the fire or to evacuate the people in the vicinity of the accident. The proposed algorithm addresses several aspects of the BLEVE accident and its mitigation: Computational Fluid Dynamic (CFD) Simulation of jet fire by using fire dynamics simulator (FDS) software by using large eddy simulation (LES); calculation of the convective and radiative heat fluxes by using the impinging jet fire theory; performing thermochemical and heat transfer analysis on the glass-woven vinyl ester coating of the vessel by using FDS software (version 5); and COMSOL Multiphysics (version 4.3b) during the heating phase of composite and calculation of the time period required to evaporate the liquefied propane by using the first and second laws of thermodynamics.

FireExplorer: A Graphical User Interface for Fire Modeling

2009 ◽  
Author(s):  
D. Swensen ◽  
S. Borodai ◽  
E. Eddings ◽  
M. McDonald ◽  
D. Swede ◽  
...  
Keyword(s):  
User Interface ◽  
Graphical User Interface ◽  
Fire Protection ◽  
Fluid Dynamic ◽  
Fire Spread ◽  
Fire Modeling ◽  
Heat Fluxes ◽  
Fire Dynamics ◽  
Modeling Software ◽  
Set Up

Fire modeling is used by Fire Protection Engineers and fire researchers to evaluate fire spread and damage for a wide variety of applications, including evaluating building fire protection systems, developing fire safety equipment and assisting in legal proceedings by assessing the source of a fire. Historically, empirical and zonal models that contained limited physics and accuracy were used for these analyses. Today, there is a greater emphasis on using Computational Fluid Dynamic (CFD) based models because these models can capture localized conditions (e.g., local temperatures, heat fluxes, gas composition, smoke travel) required to perform a proper analysis of a fire situation which can be crucial when evaluating product designs, safety procedures, fire re-enactments and smoke transport. Although several fire modeling software packages are available, the Fire Dynamics Simulator (FDS) package available from NIST is commonly used due to the fire modeling community having confidence in this tool because it has been validated. In this paper is described a new software package, FireExplorer®, which can be used to simplify the time-consuming and complex tasks required to create the inputs for the NIST FDS model, execute and monitor the simulation and view the results.. The tool employs an easy to use graphical user interface designed for use by the non-modeling expert. The tool contains all the capabilities required to set-up, execute, analyze and visualize a fire simulation in an environment that is robust, flexible and extensible.

Hydrodynamics and Hydroacoustics Investigation of a Blade Profile in a Hubless Propeller System Based on a Hybrid Approach

2019 ◽  
Vol 105 (4) ◽  
pp. 600-615
Author(s):  
Hoshang Sultani ◽  
Max Hieke ◽  
Otto von Estorff ◽  
Matthias Witte ◽  
Frank-Hendrik Wurm
Keyword(s):  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Hybrid Approach ◽  
Flow Simulation ◽  
Detached Eddy Simulation ◽  
Blade Profile ◽  
Eddy Simulation ◽  
System A ◽  
Pressure Fields ◽  
Experimental Hydrodynamics

The scope of the paper is the investigation of the hydrodynamic and hydroacoustic characteristic of a blade profile within a hubless propeller system. A hybrid procedure was applied in which the flow simulation results in terms of velocity and pressure fields were used as source terms for the hydroacoustics calculations. The Computational Fluid Dynamic (CFD) simulation of the complex 3D system was done using a scale resolving Detached Eddy Simulation (DES). The calculation of the acoustics was carried out using the Expansion about Incompressible Flow (EIF) approach. For the spatial discretization of the EIF equations the Finite Volume Moving Least Squares (FV-MLS) method was used. This method has promising features especially in the application of unstructured meshes. A first verification of the acoustic model is presented. For the validation of the used numerical methods extensive experimental hydrodynamics and hydroacoustics investigations of the hubless propeller system were carried out.

scholarly journals ANALYSIS OF THE TURBULENCE-RADIATION INTERACTION IN A METHANE-AIR DIFFUSION FLAME

2018 ◽  
Vol 17 (1) ◽  
pp. 86
Author(s):  
G. C. Fraga ◽  
A. P. Petry ◽  
F. H. R. França
Keyword(s):  
Heat Flux ◽  
Heat Source ◽  
Diffusion Flame ◽  
Radiative Heat ◽  
Numerical Study ◽  
Heat Fluxes ◽  
Fire Dynamics ◽  
Eddy Simulation ◽  
Volume Method ◽  
Air Diffusion

The phenomenon of turbulence-radiation interaction (TRI) has been demonstrated experimentally, theoretically and numerically to be important in a great number of engineering applications. This paper presents a numerical study on the subject, focusing on a methane-air diffusion flame confined in a rectangular enclosure. An open source, Fortran-based code, Fire Dynamics Simulator, is used for the analysis. Large Eddy Simulation (LES) is adopted to model the turbulence, and to resolve the sub-grid scale terms the dynamic Smagorinsky model is employed. To solve the radiative heat transfer, the finite volume method is used alongside the Weighted-Sum-of-Gray-Gases model. The main objective of the present work is to assess the magnitude of TRI effects for the configuration proposed. For this purpose, the time-averaged wall heat fluxes and volumetric radiative heat source, calculated from the LES results, are compared with those same quantities obtained by independent simulations initialized using mean temperature and species concentration fields. TRI effects are found to be responsible for differences up to 30% between results considering and neglecting turbulent fluctuations. These differences are larger for the radiative heat source and for the radiative heat flux to the walls, smaller for the total heat flux, and almost negligible for the convective heat flux. The influence of the fuel stream Reynolds number on the TRI effects is also evaluated, and a slight decrease on the magnitude of TRI is observed with the increase of that parameter.

scholarly journals Assessing IDDES-Based Wall-Modeled Large-Eddy Simulation (WMLES) for Separated Flows with Heat Transfer

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 246
Author(s):  
Rozie Zangeneh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Skin Friction ◽  
Heat Fluxes ◽  
Separated Flows ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Isothermal Wall

The Wall-modeled Large-eddy Simulation (WMLES) methods are commonly accompanied with an underprediction of the skin friction and a deviation of the velocity profile. The widely-used Improved Delayed Detached Eddy Simulation (IDDES) method is suggested to improve the prediction of the mean skin friction when it acts as WMLES, as claimed by the original authors. However, the model tested only on flow configurations with no heat transfer. This study takes a systematic approach to assess the performance of the IDDES model for separated flows with heat transfer. Separated flows on an isothermal wall and walls with mild and intense heat fluxes are considered. For the case of the wall with heat flux, the skin friction and Stanton number are underpredicted by the IDDES model however, the underprediction is less significant for the isothermal wall case. The simulations of the cases with intense wall heat transfer reveal an interesting dependence on the heat flux level supplied; as the heat flux increases, the IDDES model declines to predict the accurate skin friction.

scholarly journals Impeller Optimization in Crossflow Hydraulic Turbines

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 313
Author(s):  
Marco Sinagra ◽  
Calogero Picone ◽  
Costanza Aricò ◽  
Antonio Pantano ◽  
Tullio Tucciarelli ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Structural Safety ◽  
3D Fem ◽  
Good Efficiency ◽  
Standard Material ◽  
Variable Head ◽  
Hydraulic Turbines ◽  
Constructive Simplicity ◽  
Mechanical Optimization

Crossflow turbines represent a valuable choice for energy recovery in aqueducts, due to their constructive simplicity and good efficiency under variable head jump conditions. Several experimental and numerical studies concerning the optimal design of crossflow hydraulic turbines have already been proposed, but all of them assume that structural safety is fully compatible with the sought after geometry. We show first, with reference to a specific study case, that the geometry of the most efficient impeller would lead shortly, using blades with a traditional circular profile made with standard material, to their mechanical failure. A methodology for fully coupled fluid dynamic and mechanical optimization of the blade cross-section is then proposed. The methodology assumes a linear variation of the curvature of the blade external surface, along with an iterative use of two-dimensional (2D) computational fluid dynamic (CFD) and 3D structural finite element method (FEM) simulations. The proposed methodology was applied to the design of a power recovery system (PRS) turbine already installed in an operating water transport network and was finally validated with a fully 3D CFD simulation coupled with a 3D FEM structural analysis of the entire impeller.

scholarly journals Risk Analysis of Road Tunnels: A Computational Fluid Dynamic Model for Assessing the Effects of Natural Ventilation

2020 ◽  
Vol 11 (1) ◽  
pp. 32
Author(s):  
Ciro Caliendo ◽  
Gianluca Genovese ◽  
Isidoro Russo
Keyword(s):  
Natural Ventilation ◽  
Fluid Dynamic ◽  
Movement Time ◽  
Radiant Heat ◽  
Heat Fluxes ◽  
Maximum Heat ◽  
Road Tunnels ◽  
Maximum Heat Release ◽  
Computational Fluid Dynamics Cfd ◽  
Time Required

We have developed an appropriate Computational Fluid Dynamics (CFD) model for assessing the exposure to risk of tunnel users during their evacuation process in the event of fire. The effects on escaping users, which can be caused by fire from different types of vehicles located in various longitudinal positions within a one-way tunnel with natural ventilation only and length less than 1 km are shown. Simulated fires, in terms of maximum Heat Release Rate (HRR) are: 8, 30, 50, and 100 MW for two cars, a bus, and two types of Heavy Goods Vehicles (HGVs), respectively. With reference to environmental conditions (i.e., temperatures, radiant heat fluxes, visibility distances, and CO and CO2 concentrations) along the evacuation path, the results prove that these are always within the limits acceptable for user safety. The exposure to toxic gases and heat also confirms that the tunnel users can safely evacuate. The evacuation time was found to be higher when fire was related to the bus, which is due to a major pre-movement time required for leaving the vehicle. The findings show that mechanical ventilation is not necessary in the case of the tunnel investigated. It is to be emphasized that our modeling might represent a reference in investigating the effects of natural ventilation in tunnels.

scholarly journals Computational fluid dynamics (CFD) simulation analysis on retinal gas cover rates using computational eye models

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Makoto Gozawa ◽  
Yoshihiro Takamura ◽  
Tomoe Aoki ◽  
Kentaro Iwasaki ◽  
Masaru Inatani
Keyword(s):  
Cfd Simulation ◽  
Simulation Analysis ◽  
Fluid Dynamic ◽  
Fluid Analysis ◽  
Intraocular Gas ◽  
Pars Plana ◽  
Computational Fluid Dynamics Cfd ◽  
Multiple Breaks ◽  
Gas Volume ◽  
Wall Wettability

AbstractWe investigated the change in the retinal gas cover rates due to intraocular gas volume and positions using computational eye models and demonstrated the appropriate position after pars plana vitrectomy (PPV) with gas tamponade for rhegmatogenous retinal detachments (RRDs). Computational fluid dynamic (CFD) software was used to calculate the retinal wall wettability of a computational pseudophakic eye models using fluid analysis. The model utilized different gas volumes from 10 to 90%, in increments of 10% to the vitreous cavity in the supine, sitting, lateral, prone with closed eyes, and prone positions. Then, the gas cover rates of the retina were measured in each quadrant. When breaks are limited to the inferior retina anterior to the equator or multiple breaks are observed in two or more quadrants anterior to the equator, supine position maintained 100% gas cover rates in all breaks for the longest duration compared with other positions. When breaks are limited to either superior, nasal, or temporal retina, sitting, lower temporal, and lower nasal position were maintained at 100% gas cover rates for the longest duration, respectively. Our results may contribute to better surgical outcomes of RRDs and a reduction in the duration of the postoperative prone position.

scholarly journals Simulation of Hydraulic Cylinder Cushioning

2021 ◽  
Vol 13 (2) ◽  
pp. 494
Author(s):  
Antonio Algar ◽  
Javier Freire ◽  
Robert Castilla ◽  
Esteban Codina
Keyword(s):  
Dynamic Model ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Computational Fluid Dynamic Simulation ◽  
Hydraulic Cylinder ◽  
Outlet Port ◽  
Optimal Behavior ◽  
Radial Movement ◽  
Mechanical Shocks ◽  
Radial Gap

The internal cushioning systems of hydraulic linear actuators avoid mechanical shocks at the end of their stroke. The design where the piston with perimeter grooves regulates the flow by standing in front of the outlet port has been investigated. First, a bond graph dynamic model has been developed, including the flow throughout the internal cushion design, characterized in detail by computational fluid-dynamic simulation. Following this, the radial movement of the piston and the fluid-dynamic coefficients, experimentally validated, are integrated into the dynamic model. The registered radial movement is in coherence with the significant drag force estimated in the CFD simulation, generated by the flow through the grooves, where the laminar flow regime predominates. Ultimately, the model aims to predict the behavior of the cushioning during the movement of the arm of an excavator. The analytical model developed predicts the performance of the cushioning system, in coherence with empirical results. There is an optimal behavior, highly influenced by the mechanical stress conditions of the system, subject to a compromise between an increasing section of the grooves and an optimization of the radial gap.

Sign in / Sign up

Export Citation Format

Share Document