BPS5234A CFD Applications in the Built Environment

How BPS5234A is assessed

The four weighted components total 100%. Every other row in the component table, including laboratory tests and a mid-term test, is set at 0%, and there is no final exam weighting. No hurdle, minimum-mark or attendance condition is stated for any component in the materials reviewed here, and the assignment pages show a placeholder rubric rather than published criteria; confirm both on Canvas. Two details differ between documents: the component remarks on the course page say students work on any two academic examples, while the assignment pages allocate one example per student for each assignment; and the course page and the revised syllabus document arrange weeks 3, 4, 12 and 13 differently. This guide follows the assignment pages and the revised document, which an announcement identifies as the current schedule.

Current BPS5234A dates

Dates are as published in the course page, the assignment pages and the revised syllabus document published for this offering. Confirm exact deadlines and submission settings in the live LMS.

What BPS5234A covers

Twelve chapters move from the conservation equations and turbulence closures, through geometry, meshing, boundary conditions and the evidence that makes a result trustworthy, to the academic working examples and the industry group project.

The course description sets out the arc: fundamental principles and governing equations, grid generation and numerical techniques, then academic and industry case studies on natural ventilation, wind-driven rain, indoor air quality, vegetation cooling, and fire or pollutant dispersion.

Students build geometry, mesh domains, apply boundary conditions and validate results using commercial and open-source software, and the work is aligned with Singapore’s Green Mark CFD criteria for performance-based, climate-resilient design.

How the semester builds

The opening weeks assemble a toolkit in the order a real study uses it.

The conservation equations come first, with the turbulence closures that make them solvable and the particle and rain models that extend them. Then come the ten fundamental principles of a CFD study, geometry preparation, grid generation and mesh quality, boundary conditions and solver settings, post-processing, and verification and validation.

The later weeks apply that toolkit to academic working examples such as flow past a square cylinder, a heated cube, single and paired buildings, urban arrays, street canyons and urban morphologies, before turning to industry applications, green building certification and the future of the field.

What is assessed

Assessment is entirely coursework and in-class work.

Two individual assignments carry 45 per cent between them, each built on one allocated academic working example with its lab-manual requirements and three tutorial questions. A group project carries 40 per cent, split evenly between a presentation and a report on an industry working example applied to a real building. Two hands-on quizzes carry 5 per cent each, and class participation carries 5 per cent.

There is no final exam weighting in this course, since the published component table sets that row at 0 per cent.

Where the course documents differ

The course page and the revised syllabus document list the same thirteen weeks with two differences: the revised document attaches the first academic working examples to weeks 3 and 4, and it moves the group presentation into week 13 by combining the green building and future-of-CFD topics in week 12. The ten principles that guide the quizzes are also worded differently on the course page from the lecture slide.

This guide follows the revised document for dates and shows both wordings of the principles.

How this guide is organised

Each chapter states the method in the course’s own terms, works a complete example with numbers you can check, and closes with practice prompts shaped like the tutorial questions.

The working-example chapters are grouped by the physics they share, because separation, wakes and recirculation run through all of them.

Worked example · free

Turning a facade pressure into a pressure coefficient

Key terms

Computational Domain

The region of air enclosed for a simulation, sized so that its boundaries do not distort the flow being studied.

Boussinesq Approximation

A simplification that keeps density variation only in the gravity term, so warm air rises while continuity stays incompressible.

Reynolds Stress

The momentum carried by turbulent velocity fluctuations, which averaging leaves as an unknown that a turbulence model must supply.

Wall Function

A near-wall law that supplies shear and heat transfer for the first cell so the thin viscous layer need not be resolved.

Equiangle Skewness

A cell-quality measure from 0 for an ideal shape to 1 for a degenerate one, based on how far its angles depart from the ideal.

Numerical Viscosity

Artificial smoothing introduced by discretisation, which smears gradients and shortens wakes on coarse or poorly aligned grids.

Pressure Coefficient

Surface pressure relative to the free stream divided by the dynamic pressure, used to compare wind loading and ventilation potential.

Velocity Amplification Factor

Local wind speed at pedestrian height divided by a reference speed, used to judge comfort and ventilation.

Catch Ratio

Rain flux arriving on a facade divided by the horizontal rainfall intensity, used to compare wetting across storms.

Grid Independence

The condition reached when further mesh refinement no longer changes the quantity of interest by more than a stated tolerance.

BPS5234A FAQ

Questions students ask in each BPS5234A chapter

Why does a building simulation treat air as incompressible when its density changes with temperature?

The density changes in rooms and streets are only a few per cent, too small to alter mass conservation noticeably. They are kept where they matter, in the gravity term of momentum, through the Boussinesq approximation, so buoyant plumes and stratification still appear while the continuity equation stays simple. Chapter 01 · Governing Equations for Building Airflow

Which turbulence model should a building study use by default?

For mean-flow design and compliance work, a realizable or RNG k-epsilon model is the usual starting point and is what most of the course labs use. Move to SST when separating and reattaching flow or wall heat transfer decide the answer, and reserve Reynolds stress models and LES for anisotropic flows, transient phenomena or research. Chapter 02 · Turbulence Models and Near-Wall Treatment

Why are particles tracked individually instead of being solved on the grid like air?

Because the dispersed phase is dilute in most building problems and each particle responds to drag, gravity and evaporation according to its own size and history. Tracking them as individuals keeps that information, while the air remains a continuum solved on the mesh. Chapter 03 · Particle Transport and Wind-Driven Rain

Why do the principles start with the objective rather than the geometry?

Because the objective decides everything downstream: which geometry features matter, where the mesh must be fine, which equations are solved and what counts as a result. A study that starts by building geometry tends to model too much in some places and too little where the answer is decided. Chapter 04 · The Ten Fundamental Principles of a CFD Study

Why not import the BIM model directly into the solver?

Because it carries construction-level detail, template gaps and clashing parts that either break meshing or create huge numbers of tiny cells. The course’s best practice is to start from the simplest geometry, add complexity incrementally, replace thin objects with surfaces or porous models, and verify watertightness before meshing. Chapter 05 · Geometry Modelling and Clean-Up

Why is the hybrid mesh standard practice for buildings?

It combines thin prism layers that resolve boundary layers on walls and ground with flexible tetrahedral or polyhedral cells that fit complex architecture. Real building and urban models value fast set-up and adaptability over the small efficiency advantage of a fully structured mesh. Chapter 06 · Grid Generation and Mesh Quality Control

Why is a pressure outlet preferred to a velocity condition at an exhaust?

A velocity at an exhaust forces how much air leaves before the simulation has decided, which constrains the solution. A pressure outlet fixes only the pressure and allows the computed flow field to determine the outflow, which is usually the realistic situation. Chapter 07 · Boundary Conditions and Solver Settings

Why compare design options on a fixed colour scale?

Automatic scales stretch each legend to its own minimum and maximum, so the same colour can mean different values in two plots. A fixed scale makes visual differences real differences and stops a worse option looking similar to a better one. Chapter 08 · Interpreting and Validating CFD Results

Why is the square cylinder run as a transient case?

Vortex shedding is periodic, so a steady solution would average away the phenomenon the example is about. The course advises a long run with a 0.002 s time step and 20 iterations per step up to 16 s to capture full shedding and compute the Strouhal number. Chapter 09 · Flow Around Bluff Bodies and Single Buildings

How does a smaller upstream building change the wind on a taller one?

Its wake shelters the lower part of the tall building, lowering wind speed and pressure coefficient there, while the flow deflected over it is accelerated toward the upper facade, increasing suction and downwash. The recirculation length behind the small building depends on the height ratio and plan dimensions. Chapter 10 · Wind Between Buildings and Across Urban Arrays

Why does a deeper canyon ventilate worse?

As the canyon deepens the wind stops descending into it and skims over a shear layer at roof level. The trapped vortex beneath exchanges air with the flow above only weakly, so pollutant released at street level is retained rather than removed. Chapter 11 · Street Canyons and Urban Morphology

How is the group project weighted and delivered?

It carries 40 per cent of the course mark, split equally between a presentation in week 13 on 11 November 2026, twenty minutes per group plus questions, and a report due on 15 November 2026 at 23:59. Chapter 12 · Industry CFD Projects and Green Building Practice

How to prepare for the assessments

Pick the academic working example you are allocated in the first weeks and carry it through every chapter. Write down its objective, domain, mesh, boundary conditions and the one number it should produce, then test each chapter’s method on that case. By the assignment deadline the report is largely a record of decisions you have already made and checked.