computer fluid dynamics (cfd) in civil engineering … - cfd in civil engineering.pdfcomputer fluid...

MetNet MeetingPoznań, 11th October 2010

Computer Fluid Dynamics (CFD)In Civil Engineering

Fabian Cybichowski, Ph. D. Eng.


Presentation TOC:

1) Introduction: what is CFD?

2) Example 1: air flow in a room.

3) Example 2: flow and heat transfer in a duct.

4) Conclusions.


”Computational fluid dynamics (CFD) is one of the branches of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows”

(Wikipedia)

Popular techniques:- RANS (Reynolds Averaged Navier-Stokes)- LES (Large Eddy Simulations)- DNS (Direct Numerical Simulations)

Most common discretization methods:- FVM (Finite Volume Method)- FEM (Finite Element Method)


CFD – aeronautics & car industry


CFD – urban planning


CFD – fire simulations


CFD – HVAC, IAQ


Example 1

Ventilation in a room


Example 1: geometry


Example 1: geometry & mesh


Example 1: boundary conditions

- Steady, viscous flow- Uniform temperature (without

heat exchange)- Non-slip condition on the walls,

standard wall functions- Standard k-ε model- Air enters the room through the

vent just under the ceiling and leaves through the opening under the doors


Example 1: results(stream lines)

- The ventilation efficiency is not satisfactory, most of the air goes directly from air vent to the opening under the doors

- Problems with IAQ can be expected


Example 1: modified model(stream lines)

- Air vent moved to the short wall

- Now the fresh (clean) air sweeps entire room

- The comfort of a person working at the desk should be improved


Example 2

Air flow through a duct, with heat exchange


Example 2: geometry

- Roof panel with embedded air ducts for free-cooling & solar energy absorption


Example 2: geometry & mesh


Example 2: boundary conditions

- Steady, viscous flow- Constant temperature of air entering the duct- Constant temperature of three upper walls (exposed to the sun)- No heat exchange on the bottom plane (thermal insulation)- No slip condition on the walls, standard wall functions- Standard k-e model


Example 2: results (animation)


Example 2: results


Conclusion

CFD modeling in civil engineering: - is very convenient in terms of geometry and boundary conditions, offers

much more flexibility then laboratory experiments –some quantities are simply impossible to measure,

- gives a great amount of data about the simulated process and offers high data resolution,

- require vast knowledge of both the phenomena and numerical simulations,- can easily yield poor results – hence the need for careful validation

of every simulation.

It is great when it works, but not easy to perform: still rather research than engineering tool.


Conclusion

CFD modeling in civil engineering: - is very convenient in terms of geometry and boundary conditions, offers

much more flexibility then laboratory experiments –some quantities are simply impossible to measure,

- gives a great amount of data about the simulated process, also very high data resolution,

- require vast knowledge of both the phenomena and numerical simulations,- can easily yield poor results – hence the need for careful validation

of every simulation.

It is great when it works, but not easy: still rather research than engineering tool.

Thank you for

your attention

computer fluid dynamics (cfd) in civil engineering … - cfd in civil engineering.pdfcomputer fluid...

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