scholarly journals Simulating Smoke Filling in Big Halls by Computational Fluid Dynamics

2011 ◽  
Vol 2011 ◽  
pp. 1-16 ◽  
Author(s):  
W. K. Chow ◽  
C. L. Chow ◽  
S. S. Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Construction Projects ◽  
Far East ◽  
Mainland China ◽  
Convergence Criteria ◽  
Key Points ◽  
Set Up ◽  
Relaxation Factors ◽  
Smoke Filling

Many tall halls of big space volume were built and, to be built in many construction projects in the Far East, particularly Mainland China, Hong Kong, and Taiwan. Smoke is identified to be the key hazard to handle. Consequently, smoke exhaust systems are specified in the fire code in those areas. An update on applying Computational Fluid Dynamics (CFD) in smoke exhaust design will be presented in this paper. Key points to note in CFD simulations on smoke filling due to a fire in a big hall will be discussed. Mathematical aspects concerning of discretization of partial differential equations and algorithms for solving the velocity-pressure linked equations are briefly outlined. Results predicted by CFD with different free boundary conditions are compared with those on room fire tests. Standards on grid size, relaxation factors, convergence criteria, and false diffusion should be set up for numerical experiments with CFD.

Computational Fluid Dynamics Simulation of Fire-Induced Air Flow in a Large Space Building: Key Points to Note

2004 ◽  
Author(s):  
Y. F. Li ◽  
W. K. Chow
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Source ◽  
Air Flow ◽  
Region Of Interest ◽  
Dynamics Simulation ◽  
Navier Stokes ◽  
Convergence Criteria ◽  
Large Space ◽  
Key Points

Fire-induced air flow in a large span building by computational fluid dynamics (CFD) will be discussed in this paper. The CFD model is based on Reynolds Averaging Navier-Stokes (RANS) equations with k-ε based turbulence model for predicting velocity, pressure and temperature distribution. This technique is commonly used in practical design for smoke management system. The fire is taken as a volumetric heat source and buoyancy effects are included in equations for the vertical momentum and turbulent parameters. Several key points to note in the simulation will be discussed. These are: • Relaxation factor and convergence criteria. • False diffusion. • Sudden changes in flow parameters across the heat source. A large terminal hall with 1 MW fire is taken as an example to discuss the above points. The fire scenarios in a region of interest will be assessed by CFD.

scholarly journals Improving Performance of Simplified Computational Fluid Dynamics Models via Symmetric Successive Overrelaxation

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2438 ◽  
Author(s):  
Vojtěch Turek
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Direct Calculation ◽  
Steady State Solution ◽  
Computational Time ◽  
Process Equipment ◽  
Successive Overrelaxation ◽  
Lower Upper ◽  
Cfd Models ◽  
Relaxation Factors

The ability to model fluid flow and heat transfer in process equipment (e.g., shell-and-tube heat exchangers) is often critical. What is more, many different geometric variants may need to be evaluated during the design process. Although this can be done using detailed computational fluid dynamics (CFD) models, the time needed to evaluate a single variant can easily reach tens of hours on powerful computing hardware. Simplified CFD models providing solutions in much shorter time frames may, therefore, be employed instead. Still, even these models can prove to be too slow or not robust enough when used in optimization algorithms. Effort is thus devoted to further improving their performance by applying the symmetric successive overrelaxation (SSOR) preconditioning technique in which, in contrast to, e.g., incomplete lower–upper factorization (ILU), the respective preconditioning matrix can always be constructed. Because the efficacy of SSOR is influenced by the selection of forward and backward relaxation factors, whose direct calculation is prohibitively expensive, their combinations are experimentally investigated using several representative meshes. Performance is then compared in terms of the single-core computational time needed to reach a converged steady-state solution, and recommendations are made regarding relaxation factor combinations generally suitable for the discussed purpose. It is shown that SSOR can be used as a suitable fallback preconditioner for the fast-performing, but numerically sensitive, incomplete lower–upper factorization.

Computational fluid dynamics study of Savonius rotors using OpenFOAM

2020 ◽  
pp. 0309524X2092495
Author(s):  
Federico González Madina ◽  
Alejandro Gutiérrez ◽  
Pedro Galione
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Dynamics Simulation ◽  
Power Coefficient ◽  
Small Scale ◽  
Two Dimensional ◽  
Discretization Schemes ◽  
Set Up

In this work, two-dimensional models of Savonius rotors are simulated using OpenFOAM® in order to predict the aerodynamic performance of small-scale vertical-axis wind turbines. The results are reported analyzing the aerodynamic performance and forces acting on the rotors. Power coefficient, [Formula: see text], is compared with experimental data for each operation point, and for three different geometries. Simulations with first- and second-order discretization schemes are carried out and compared, both quantitative and qualitative. Since usual grid dimensions result not to be suitable for simulations of Savonius rotors, an analysis of different domains is performed and compared. Finally, a set up for computational fluid dynamics simulation of two-dimensional Savonius rotors is proposed. The fluid–rotor interaction is analyzed and the vortex shedding is correlated with [Formula: see text] values and wake description.

scholarly journals Mapping flow distortion on oceanographic platforms using computational fluid dynamics

Ocean Science ◽  
2013 ◽  
Vol 9 (5) ◽  
pp. 855-866 ◽  
Author(s):  
N. O'Sullivan ◽  
S. Landwehr ◽  
B. Ward
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Speed ◽  
Close Agreement ◽  
Velocity Fields ◽  
Experimental Measurements ◽  
Flow Distortion ◽  
Direct Measurements ◽  
Computational Fluid Dynamics Cfd ◽  
Set Up

Abstract. Wind speed measurements over the ocean on ships or buoys are affected by flow distortion from the platform and by the anemometer itself. This can lead to errors in direct measurements and the derived parametrisations. Here we computational fluid dynamics (CFD) to simulate the errors in wind speed measurements caused by flow distortion on the RV Celtic Explorer. Numerical measurements were obtained from the finite-volume CFD code OpenFOAM, which was used to simulate the velocity fields. This was done over a range of orientations in the test domain from −60 to +60° in increments of 10°. The simulation was also set up for a range of velocities, ranging from 5 to 25 m s−1 in increments of 0.5 m s−1. The numerical analysis showed close agreement to experimental measurements.

scholarly journals High-order computational fluid dynamics tools for aircraft design

2014 ◽  
Vol 372 (2022) ◽  
pp. 20130318 ◽  
Author(s):  
Z. J. Wang
Keyword(s):  
Fluid Dynamics ◽  
Growth Rate ◽  
Computational Fluid Dynamics ◽  
Fuel Economy ◽  
Aircraft Design ◽  
Aircraft Engine ◽  
Foreseeable Future ◽  
Complex Flows ◽  
Environmental Goals ◽  
Set Up

Most forecasts predict an annual airline traffic growth rate between 4.5 and 5% in the foreseeable future. To sustain that growth, the environmental impact of aircraft cannot be ignored. Future aircraft must have much better fuel economy, dramatically less greenhouse gas emissions and noise, in addition to better performance. Many technical breakthroughs must take place to achieve the aggressive environmental goals set up by governments in North America and Europe. One of these breakthroughs will be physics-based, highly accurate and efficient computational fluid dynamics and aeroacoustics tools capable of predicting complex flows over the entire flight envelope and through an aircraft engine, and computing aircraft noise. Some of these flows are dominated by unsteady vortices of disparate scales, often highly turbulent, and they call for higher-order methods. As these tools will be integral components of a multi-disciplinary optimization environment, they must be efficient to impact design. Ultimately, the accuracy, efficiency, robustness, scalability and geometric flexibility will determine which methods will be adopted in the design process. This article explores these aspects and identifies pacing items.

Numerical Study of Internal Fire Whirls in a Kitchen With Ceiling Vents

2013 ◽  
Author(s):  
W. K. Chow ◽  
N. Cai ◽  
Y. Gao
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Study ◽  
Air Flow ◽  
Ventilation System ◽  
Necessary Condition ◽  
Temperature Distributions ◽  
Computational Fluid Dynamics Cfd ◽  
Fire Whirl ◽  
Set Up

The characteristics of flame rotation induced by a fire at the top of kitchen stove were studied numerically with Computational Fluid Dynamics (CFD). Four cases with different locations of fire sources and vents were set up; simulations of swirling air flow and temperature distributions in the kitchen room were carried out. Ventilation by ceiling vents was identified as the necessary condition for internal fire whirl. Recommendations on the design of kitchen ventilation system were made.

Research of 3D-CFD Simulation on a Large Sized Pit Type Carburizing Furnace

2006 ◽  
Vol 118 ◽  
pp. 337-342
Author(s):  
Wei Min Zhang ◽  
Ye Ma ◽  
Lin Lin Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Cfd Simulations ◽  
3 Dimensional ◽  
Set Up ◽  
Carburizing Process

A fluid dynamic model was set up to describe the flow field of gas in a large sized pit type carburizing furnace when large sized gears were being carburized. The commercial software Fluent was adopted to carry out 3 dimensional computational fluid dynamics (3D-CFD) simulations of the gas flow field under different, actually four kinds of , furnace designs in this article. The flow fields of the carburizing gas around the part were analyzed. According to the simulations and analysis, it was shown that the number of fans on gear’s carburizing is not a primary factor, using a air inducting tub can improve the carburizing process significantly and proper loading tray design can also be positive. The results indicate that the simulation provides a reference to the furnace’s design optimization.

scholarly journals FIRE SAFETY ASPECTS OF REFUGE FLOORS IN SUPERTALL BUILDINGS WITH COMPUTATIONAL FLUID DYNAMICS

2009 ◽  
Vol 15 (3) ◽  
pp. 225-236 ◽  
Author(s):  
Cheuk Lun Chow ◽  
Wan Ki Chow
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fire Safety ◽  
Emergency Services ◽  
Far East ◽  
Large Area ◽  
Water Curtain ◽  
High Rise ◽  
The Far East ◽  
Fire Codes

High-rise buildings in many big cities in the Far East, including Hong Kong, call for refuge floors as a matter of both practicality and compliance with regulations. Even though many countries’ fire codes are not clear in spelling out the necessity for refuge floors, it is accepted within construction that such floors are essential in resisting fire, allowing users a means of escape and allowing emergency services a means of access to stricken buildings. This paper discusses the reasons behind providing refuge floors, while also considering related fire safety provisions, such as their enclosure behind fire‐resistant construction or the protection of their openings behind a water curtain. Our discussion takes a tall building with balconies as a test example of refuge floors, running a hazard assessment based on Computational Fluid Dynamics assuming a fire of the broadly accepted level of 2 MW. The paper concludes that the design of the building's façade finally determines whether or not a refuge floor and associated fire safety provisions, such as a water curtain, can be waived. As the flat modelled used to store a high amount of combustibles up to 1135 MJm−2, the breaking of large area of glass window could lead to a major conflagration. The consequences of a scenario with a fire of 25 MW are also discussed. Santrauka Daugelio Tolimųjų Rytų didžiųjų miestų aukštuminiuose pastatuose, taip pat ir Honkongo, reikalingi saugos aukštai, paisant praktiškumo ir atitikimo reikalavimus. Netgi jei daugelio šalių gaisrinės saugos normos aiškiai nereglamentuoja būtinybės įrengti saugos aukštų, konstrukciniu požiūriu tokie aukštai yra būtini gaisrinei saugai, užtikrinant pastato naudotojams evakuacijos galimybę ir avarinėms tarnyboms patekimą į pastatą. Straipsnyje aptariamos saugos aukštų įrengimo priežastys, taip pat įvertinamos susijusios tokios gaisrinės saugos priemonės, kaip atsparių ugniai konstrukcijų įrengimas arba angų apsauga vandens užuolaida. Nagrinėjamas aukštuminis pastatas su balkonais, kaip eksperimentinis saugos aukštų pavyzdys, įvertinant pavojų. Tai daroma naudojant skysčių dinamikos modeliavimą ir plačiai pripažintą 2 MW galios gaisrą. Straipsnyje daromos išvados, kad pastato fasado projektiniai sprendiniai daro įtaką, ar saugos aukštai ir susijusios tokios gaisrinės saugos priemonės, kaip vandens užuolaida, gali būti nenumatomi. Jei pastate numatoma saugoti daug degiųjų medžiagų viršijant 1135 MJm–2 gaisro apkrovą, didelio ploto langų išdužimas gali veikti visuminį užsidegimą. Aptariami ir 25 MW galios gaisro scenarijaus padariniai.

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