Tutorials

Fundamentals

Learn the basics in PyroSim Fundamentals
Learn the basics in PyroSim Fundamentals

How-To

Creating and Importing Geometry

Create Stairs
This brief tutorial demonstrates how to quickly create stairs using the Copy/Move action and editing multiple obstructions at the same time.
Importing FDS Validation Examples into PyroSim
The FDS validation suite compares FDS (Fire Dynamic Simulator) results with experimental data. These examples cover most of the features of available in FDS. When you want to use a new feature in FDS, you can speed your learning by reviewing how the feature was used in a validation example. This post shows how you can quickly import the FDS model into PyroSim.
PyroSim Geometry from SketchUp
This screen cast covers a method that can be used to build a 3D model in SketchUp Make, and then export the geometry for use in PyroSim.
Mesh ToolsPyroSim Mesh Tools
This quick tip goes over a few of the available features in PyroSim for Meshes.
Ramps in PyroSim/FDS
This post shows how to draw a ramp in PyroSim, using triangular slabs to approximate the geometry. Ramps are useful when modeling parking garages or pedestrian walkways.

Configuring Devices

Create CO Sampling Device
This video demonstrates how to add a carbon monoxide detector and view its output.
Freezing HRR in PyroSim
A common strategy when modelling a fire with sprinklers is to assume the fire will be held at a constant heat release rate (HRR) when the first sprinkler activates. This post shows how to do this by automatically "freezing" the HRR at a constant value when a sprinkler activates.
Smoke Visibility and Obscuration in PyroSim
Smoke visibility and obscuration are critical outputs of a fire simulation. This post reviews how visibility is calculated in FDS, compares the calculation to experimental data, and discusses how smoke is visualized in the new PyroSim Results Viewer and in Smokeview. The comparison of VTT experimental images with predicted smoke visualization using PyroSim/FDS shows remarkably good correlation. 

Defining Reactions & Materials

Complex Stoichiometry in PyroSim
PyroSim version 2018.2 will support complex stoichiometry in the user interface. Previously, PyroSim supported the FDS single-fuel, "simple chemistry" combustion model but complex stoichiometry required some manual input by the user. This post demonstrates how the new user interface capability can be used to represent multiple fuels and other complex reactions. If you would like to test this beta version, contact support@thunderheadeng.com.
Heat Conduction in PyroSim/FDS
FDS assumes one-dimensional heat conduction into the surfaces of solid obstructions. With proper modeling, you can couple the front and back face temperatures of an obstruction so that heat flows through the obstruction. This post demonstrates heat transfer through obstructions, including radiative and convective fluxes on the surface.
Heat Release Rates of Burning Items in Fires
A paper by Hyeong-Jin Kim and David Lilley (Heat Release Rates of Burning Items in Fires, AIAA 2000-0722, January 2000) summarizes experimentally measured heat release rates for more than 60 different items that could be involved in fires. The data sets used by Kim and Lilley include FASTLite, HAZARD, and the Building and Fire Research Laboratory data sets. As part of preparing PyroSim examples, we developed a spreadsheet that calculates the heat release rates using the data and method described in the paper.
Updated FDS Combustion and Fuel Composition Calculators
This post describes updated combustion product and fuel composition spreadsheet calculators for use with FDS (the Fire Dynamics Simulator from NIST).

Processing and Analyzing Results

Add Slice Output
Adding Slice output to a model is quick and easy with the Slice Tool. This video demonstrates how to add a slice and to change the slice output options with the Slice tool properties dialog.
Mesh Record Advanced TabAssign FDS Meshes to Specific MPI Processes
This feature allows additional MPI and OpenMP parameters to be added to each MESH line in PyroSim, without the need to export and edit the file by hand and run from the command line.
Using PyroSim for Parallel Processing of Multiple Meshes
This video shows reasons to use multiple meshes, rules and guidelines for defining multiple meshes, how to use the multiple mesh tools, and how to run a parallel processor solution.
VR in Pathfinder and PyroSim
The next releases of Pathfinder and PyroSim will include the capability to display results using the Oculus Rift virtual reality (VR) headset. This post gives a preview of how to use this capability.

Applications

Comparing FDS results to fire spill-plume calculations in BRE Annex D
The BRE guide Design methodologies for smoke and heat exhaust ventilation summarizes the advice available from the BRE Fire Research Station (UK)  to designers of atria and other buildings. Annex D of the BRE document compares different fire spill-plume calculation methods applied to a multistorey shopping mall. We compare Fire Dynamics Simulator (FDS) results to the calculations in Annex D.
Coupling PyroSim Fire Results with Pathfinder Movement
We have begun coupling PyroSim fire results with Pathfinder movement. The first major task was to create a Results Viewer that could merge and display PyroSim and Pathfinder results simultaneously. That has largely been completed. We have also completed limited capability to calculate the Fractional Effective Dose (FED) as occupants move through changing CO, CO2, and O2 concentrations. Future development will use PyroSim results to alter occupant movement and decision making within the Pathfinder simulation. In this post, we demonstrate the capability currently available in Pathfinder 2018.1 and PyroSim 2017.2. See the post Manually Coupling FDS and Pathfinder to Respond to Smoke for instructions on how to link fire simulation output with evacuation simulation movement
Create a t-squared Fire
In PyroSim, there is not a direct way to enter the alpha value for a t-squared fire. This short video will show you how you can determine the time to peak HRRPUA.
Critical Velocity in Tunnel Fires
Merve Altay contacted us with a tunnel model that was experiencing a numerical instability. He was simulating a set of experiments performed to evaluate the critical velocity in a tunnel fire. Answering his question eventually led to improvements in FDS and a better understanding of user applications of PyroSim/FDS.
HVAC Pressure Drop Verification
In this model, there are three HVAC nodes and two HVAC ducts. The calculation for the expected pressure loss in the duct without a fan was done in a spreadsheet that you can download.
Leakage Modelling using Pressure Zones – Updated 2018-06
Leakage refers to the air that escapes through small gaps as a compartment is pressurized by a fire. Pressure zones can be used to model this effect.
Manually Coupling FDS and Pathfinder to Respond to Smoke
A long-term development goal has been to fully couple the PyroSim/FDS fire results with Pathfinder evacuation. A first step toward this goal is the capability to display both fire and evacuation results in the same results viewer. However, full coupling of the two simulations has not been completed. In the interim, it is possible to run the fire simulation, monitor the reduced visibility due to smoke, and then manually use that information to slow and re-direct occupants in response to the fire. This provides an example.
Model a Long Tunnel
This video covers topics such as importing 3D dxf files, mesh strategies, and gravity vector ramps for a long tunnel in PyroSim.
Modeling a Pressure Relief Vent
This post analyzes a pressure relief vent, where air is injected into a room, the pressure in the room is monitored, and a vent is opened when a set pressure is reached. The key is to include at least two pressure zones in your model.
Modeling Fire, Part 1 – Reactions
All PyroSim (FDS) models that include combustion must define a gas phase reaction that converts fuel to combustion products. We review the "simple chemistry" approach in FDS.
Modeling Fire, Part 2 – Heat Release Rate
When we specify a Heat Release Rate, we are really specifying the rate at which fuel is released into the fire simulation. The fuel mass flow rate is calculated so that combustion will release heat at the desired rate.
Modeling Fire, Part 3 – Combustion using HRR
FDS can be a useful tool for both a fire protection engineer and a fire researcher. The challenge is that this can result in a bewildering array of options with respect to modeling the combustion process.
Modeling Fire, Part 4 – Combustion with HRR, Ignition, and Burn Away
In this video we show how to model a fire using a specified heat release rate per unit area (HRRPUA), an ignition temperature, and burn away. This is about as complicated as models can be made without also simulating pyrolysis.
Modeling Fire, Part 4 Addendum – Re-Analysis using HRRPUA Curve
This is an addendum to the Part 4 video on fire modeling. We re-analyzed the problem, changing the Heat Release Rate Per Unit Area (HRRPUA) from a constant value to a function (or curve).
Modeling Jet Fans, Part 1: Background and Convergence Study
This post discusses modeling jet fans using FDS/PyroSim, with the eventual goal of modeling parking garages. It starts with some background information that was useful to me in helping me understand the problem.
Modeling Jet Fans, Part 2: Validation using Experimental Data
It is not feasible to simulate full scale parking garages with such a fine mesh, even if multiple meshes are used. This post discusses ways it may be possible to use a larger mesh size and still obtain meaningful results.
Modeling Jet Fans, Part 3: Car Park Simulation
In this post, we explore modeling jet fans to extract smoke from a car park using FDS. The jet fans are modeled using HVAC ducts with shrouds.
Radiation and Convection on Surfaces
Every solid surface in an FDS model defines convective and radiative flux thermal boundary conditions. Each of the terms are always being calculated, sometimes using default parameters that may not have been explicitly set.
Figure 3Radiative Fraction and Q_RADI Output
The heat released as a fire burns is distributed to the environment primarily through convection and radiation. But, when you check the FDS output files you may see a different fractional amount of radiation in the Q_RADI column.
Smoke Visibility and Obscuration in PyroSim
Smoke visibility and obscuration are critical outputs of a fire simulation. This post reviews how visibility is calculated in FDS, compares the calculation to experimental data, and discusses how smoke is visualized in the new PyroSim Results Viewer and in Smokeview. The comparison of VTT experimental images with predicted smoke visualization using PyroSim/FDS shows remarkably good correlation. 
Using PyroSim/FDS to Maximize Solar Panel Convective Cooling
Solar panels are most efficient if they operate at lower temperatures. We are installing solar panels on a workshop roof and the question arose, "What is the best solar panel spacing to maximize solar panel convective cooling?" This post uses PyroSim and FDS to evaluate some different solar panel mounting options to maximize solar panel convective cooling.
Velocity Patch in FDS
It is not feasible to simulate full scale parking garages with such a fine mesh, even if multiple meshes are used. This post discusses ways it may be possible to use a larger mesh size and still obtain meaningful results.
WIND in PyroSim
FDS version 6.6.0 added a new WIND namelist to describe wind and atmospheric conditions. Support for WIND was included in PyroSim 2018.1. This post demonstrates this feature.

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