Engineering Simulation in Built Environment and Civil Engineering Projects

Fires and Smoke Movement ANSYS CFD is used by many companies for smoke movement assessment Characterised by complex geometries Large atria, underground stations (Crossrail) Pre-fire ventilation CFD analysis Jet fans and other fire/smoke mitigating devices required in the analysis Transient change in topology and other complex behaviour Window breaking as heat from a fire spreads through a double skin façade 2010 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary

Fires and Smoke Movement ANSYS CFD has two methods Inert simulation Add a source of heat and smoke to a 3D volume representing the fire Efficient Assumes flame shape Reacting simulation Add a source of fuel vapour over a 2D surface Equations for reactants and products Predicts the flame shape Required if strong interaction with ventilation flow Can easily switch between techniques as required 2010 ANSYS, Inc. All rights reserved. 3 ANSYS, Inc. Proprietary

Smoke Management Fire scenario with smoke penetrating many occupied areas of a building with a complex atrium Fire scenario with a smoke management system that segregates the atrium In RWDI s experience, providing a code specified quantity of exhaust at the top of the atrium is not always sufficient for a safe atrium design. Other design strategies are necessary to help keep smoke out of the occupied zones, and RWDI uses a number of these to improve smoke management systems. For example, an atrium can be segregated into smaller and simpler atria when a fire erupts. Segregation in this particular atrium led to measurable reductions in undesired smoke propagation, used less than half the exhaust air, and saved the owner both capital and operating costs. Courtesy of RWDI Inc, Canada 2010 ANSYS, Inc. All rights reserved. 4 ANSYS, Inc. Proprietary

Fire Suppression Machinery space aboard a typical vessel Part of a work program funded by the MOD Identify an alternative to Halon Simulation of water mist Liquid and vapour phase Particle transport of evaporating droplets Nozzle locations indicated by orange spheres Fire region Combustion Reacting fuel, radiation Fuel evaporation determined by radiative and covective heat transfer Imported CAD model Interflam 2007, Vol. 1, pp 323 333 British Crown Copyright 2007/MOD. Published with the permission of the Controller of Her Britannic Majesty's Stationery Office 2010 ANSYS, Inc. All rights reserved. 6 ANSYS, Inc. Proprietary

Fire Suppression Droplet modeling in complex geometry can be simulated in order to optimize the location and the effectiveness of fire suppression equipment Temperature iso-surfaces and droplet trajectories before extinction, in a ship s machinery space. British Crown Copyright 2007/MOD. Published with the permission of the Controller of Her Britannic Majesty's Stationery Office 2010 ANSYS, Inc. All rights reserved. 7 ANSYS, Inc. Proprietary

Hydraulics Free Surface Spillway Controlled release of flood water Profile designed to minimise adverse effects such as downstream erosion Reduce kinetic energy of the flow Hydraulic jump, Ski jump/ flip bucket, Plunge pool, Stepped Can employ roughness elements Designed probable maximum flood levels can be revised upwards CFD for impact assessment Discharge capacity Velocity profiles Free surface animation coloured by velocity Burdekin - hydraulic Itaipu ski, plunge Yeoman Hay - stepped 2010 ANSYS, Inc. All rights reserved. 8 ANSYS, Inc. Proprietary

Spillway Example CFD analysis of an Energy Dissipation Chamber (EDC) Reduce kinetic energy to prevent erosion of river/pond CFD used to supplement 1D design rules to determine whether off design operation poses risks to equipment 2010 ANSYS, Inc. All rights reserved. 9 ANSYS, Inc. Proprietary

Spillway Example CFD analysis of water free surface Identified region where water contacting spillway ceiling Potential for erosion damage under high level operation Hydraulic jump at base of spillway as fast moving water contacts hold-up 2010 ANSYS, Inc. All rights reserved. 10 ANSYS, Inc. Proprietary

Hydraulics Waves Tsunami Large gravity waves Impact Forces Sea wall design Free surface animation of a 5m wave. Surface coloured by height above see level Free surface animation of a 5m wave. Buildings coloured by pressure loading 2010 ANSYS, Inc. All rights reserved. 12 ANSYS, Inc. Proprietary

Sand Build Up Dust storms relatively common in arid regions Snow an equivalent problem in northern cities Increased urban sprawl Dust/sand ingress needs to be understood to minimise disruption Reduce maintenance and servicing costs 2010 ANSYS, Inc. All rights reserved. 13 ANSYS, Inc. Proprietary

Sand Build Up Demonstration Predict formation trends over time Build up on upstream faces Downstream shadowing Later build up behind downstream face Animation demonstrating sand build up 2010 ANSYS, Inc. All rights reserved. 14 ANSYS, Inc. Proprietary

Sand Build Up Urban environment Can see correlation for sand deposition with high velocity gradients and low flow Not simply a function of low velocity regions as sand has to be transported to the location first 2010 ANSYS, Inc. All rights reserved. 15 ANSYS, Inc. Proprietary

Sand Build Up Urban environment Thus, deposition occurs Against buildings Leeward calm zones where access is possible Low flow regions Open spaces Ongoing work to understand Compaction effects where dunes become more resistant to being blown away once formed Surface saltation effects Sand surface coloured by height 2010 ANSYS, Inc. All rights reserved. 16 ANSYS, Inc. Proprietary

Summary ANSYS CFD provides powerful tools to look at Urban wind flow aerodynamics Internal ventilation, solar loading and occupancy comfort Advanced glazing analysis Pollutant dispersion, smoke movement and fire modelling Hydraulics and free-surface modelling Thank you to guest speakers Karl Else, Hurley Palmer Flatt Dan Jestico, Hilson Moran Partnership 2010 ANSYS, Inc. All rights reserved. 17 ANSYS, Inc. Proprietary