BY : Dr S V Zhubrin, CHAM Ltd
DATE : November, 2000
FOR : Demonstration case for V3.3.1
A Simple Chemical Reaction System, SCRS, model application is presented aimed at the demonstration of the method for the simulation of the fire in a 3D building structure exposed to the cross wind when the external air flow over a structure and the convection followed by chemical reactions inside it have to be considered simultaneously.
The demonstration case considered consists of rectangular building structure having two window openings and near-ceiling slot exposed to the 30 degree external wind.
It is supposed that a fuel (methane) leak from the communication system enters the building structure through an internal aperture.
The fuel is ignited on entry and steady combustion is in progress producing the high temperarture combustion products. Their movement is influenced by buoyancy and the air coming in from outside.
The task is to calculate the temperatures and composition of combustion gases along with all related field distributions.
The independent variables of the problem are the three components of cartesian coordinate system, namely X, Y and Z.
The main dependent (solved for) variables are:
The K-epsilon model, KEMODL, closed by wall functions is used to calculate the distribution of turbulence energy and its dissipation rate from which the turbulence viscosity is deduced.
Combustion is treated as a single-step irreversible diffusion-controlled chemical reaction with a infinitely fast rate between fuel and oxygen. The gas composition and its enthalpy are related to the mixture fraction according to the Simple Chemical Reaction Scheme, SCRS, concept.
The gas density is computed from the local pressures, gas temperatures and local mixture molecular masses.
The specific enthalpies are related to gas temperatures, fuel mass fraction and the heat of combustion.
The plots show the distribution of temperatures, velocities and other related fields within and outside the building structure.
Pictures are as follows :
All model settings have been made in VR-Editor of PHOENICS 3.3.1
The relevant Q1 file can be inspected by clicking here.