Introduction To Computational Fluid Dynamics (cfd)

Introduction to Computational Fluid Dynamics (CFD) CFD for simulation of dispersion, fire and explosion in industrial plants

User Conference 2018

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SAFER, SMARTER, GREENER

Agenda

Agenda

What is CFD?

Challenges that CFD can help address

Introduction to KFX™ - History - Key Capabilities - Validation

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01

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CFD vs Other approaches

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CFD Fire simulation – Case Study

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Conclusions and summary

What is Computational Fluid Dynamics (CFD)?

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What is CFD? CFD – “Computational Fluid Dynamics” Use numerical methods and algorithms to solve and analyse problems that involve fluid flows – By the use of computers – Used for a wide range of problems and applications Goal: Accurate representation of the actual scenario in space and time

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CFD – An example CFD

User input

Results Smoke

Fuel type

Geometry/ congestion

Dispersion Combustion model

Release conditions

Weather and ventilation

Levels

Heavy oil or light gas

Rich or lean mixture

Flow conditions/ mixing

Fire Shape Location Heat loads

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CFD – Pros/Cons

Based on «fundamental» models - wide range of validity

High degree of complexity and difficult to use

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Interaction between release (e.g. fire) and surroundings - Weather conditions - Geometry

Long simulation times

Time development - e.g. reduction in release flow due to blowdown

“IT DEPENDS”

CFD vs other approaches

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CFD and other approaches

Detailed

Specific/Novel major accident hazards

Quantitative

All Major Accident Hazards

Semi-quantitative

Qualitative

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• CFD • Experimentation

• Quantified Fault & Event Trees • Consequence Analysis • GAMES • FRA & QRA

Critical Site Items

• Lookups • FMECA • Screening cons and risk analyses • LOPA

Site

• Hazard Identification, risk matrix • Bow Tie • FMEA • Fault and Event Trees

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Challenges that CFD can help address

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Understand how fires interact with their physical surroundings

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Understand spatial distribution of heat loads from a fire

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Understand spatial distribution of blast loads from an explosion

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Understanding the impact of an accidental release of Liquefied Natural Gas (LNG) (1)

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Understanding the impact of an accidental release of Liquefied Natural Gas (LNG) (2)

Heat flux to equipment during fire 14

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Understand how structures react when exposed to a fire load

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Understand the development of a dense gas release Flammable gas cloud 1 min. after start of release

Flammable gas cloud 10 min. after start of release DNV GL © 2018

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CFD Fire Simulation Case Study using KFX™

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Introduction to Case Study

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Introduction to KFX™

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Introduction to KFX™ “KFX™ is a three dimensional transient CFD tool for gas dispersion, gas explosion, fire development, fire mitigation and fire extinction”. Further research work at NTNU resulted in the KFX™ CFD simulator.

1970’s

1980’s/90’s

First attempts of numerical modelling of combustion at the Norwegian University of Science and Technology (NTNU).

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1999

The EXSIM CFD explosion software was acquired by ComputIT from Shell and integrated as a module in KFX™

2000’s

Commercialized in 1999 by the founding of ComputIT.

CompuIT offers KFX™ commercially together with consultancy.

2015

2017

ComputIT and KFX™ acquired by DNV GL

Further development of KFX™ supported by major oil and gas companies.

KFX™ - Key Capabilities

Optimized for simulating releases in complex geometries and for large domains

Incorporates an efficient porosity technique for optimal calculations

Includes a spray model for fire mitigation and extinction by water systems and liquid releases

Includes dedicated explosion module (EXSIM)

Integrated with Finite Element Models for structural Response Analysis

CAD Support (Multiple formats)

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KFX™ - Validation KFX™ and its sub models are extensively validated, and the validation work is a continuously ongoing and very important activity in the further development of the KFX™ CFD simulation tool – Current validation work is ongoing for LNG dispersion in the US (PHMSA) – EXSIM explosion code with new experimental data

KFX™ is validated on many different levels – against analytical solutions, scientific experiments and realistic full-scale tests – both sub-model tests and integrated tests – against small-scale, medium-scale and large-scale experiments – against various test configurations (obstruction types and layouts, venting, ignition locations, fuels and more) – blind tests and “full-information” test

Validation is documented in the KFX™ Validation handbook which is supplied with the software

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Validation Example - How well can we model an actual fire ?

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Conclusions and Summary

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Conclusions and Summary CFD has many diverse useful applications

Key criticisms of time/complexity etc. need to be understood in context – Not all CFD scenarios are time/resource intensive

KFX™ is a CFD tool that can simulate a large variety of release scenarios/hazards – Gas jet fires, liquid pool fires, liquid spray fires, two-phase fires and explosions – Transient development – Accurate calculation of heat loads and smoke dispersion – Detailed representation of geometry – fire interaction

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Q&A

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