Computational Fluid Dynamics (CFD)

CFD

CFD is a process that assists designers in optimizing the design configuration of a Tensile Membrane structure. The Light Weight Structures Architectural Solutions optimizes Tensile Membrane design with the use of CFD linked to FEA. Using this combination of technologies the design professional is able to construct a geometric model within 3D modeling software while taking into consideration surrounding buildings and landscape. When the simulation has run and the results reviewed, the 3-D model can be adjusted and the simulation rerun until the optimized tensile profile is achieved resulting in a tensile membrane structure with maximum aesthetic appeal and minimal support structure.
CFD is an alternative to wind tunnel tests. In the main small to medium creative tensile projects are not feasible to wind tunnel test due to both time deadlines and financial constraints.

Coupled CFD with FEA provides the user a cost effective solution in determining the anticipated wind action and pressures on canopy profiles. CFD has been shown to be a reasonable prediction of wind pressure distributions. It conceivably could replace some wind tunnel tests (Susila I G 2000).

Why use CFD

Tensile membrane design can be optimized with the use of CFD linked to FEA. Using this combination of technologies the design professional is able to construct a geometric model within 3D modeling software while taking into consideration surrounding buildings and landscape. When the simulation has run and the results reviewed, the 3-D model can be adjusted and the simulation rerun until the optimized tensile profile is achieved resulting in a tensile membrane structure with maximum aesthetic appeal and minimal support structure.


How is Computational Fluid Dynamics (CFD) defined,

  • Computational – having to do with mathematics, computing
  • Fluid Dynamics – the dynamics of things that flow

CFD software

CFD is a sophisticated computationally-based design and analysis technique. CFD software gives the user the power to simulate flows of wind through computer modeling. Using CFD software, the user can build a ‘virtual prototype’ of the system or device that is to be analyzed and then apply real-world physics to the model. The software will provide the user with images and data, which will predict the performance of the design.
(http://www.fluent.com/solutions/whatcfd.htm 7/10/2009)

Alternative to wind tunnel tests

In the main small to medium creative tensile projects are not feasible to wind tunnel test due to both time deadlines and financial constraints. Coupled CFD with FEA provides the user a cost effective solution in determining the anticipated wind action and pressures on canopy profiles. CFD has been shown to be a reasonable prediction of wind pressure distributions. It conceivably could replace some wind tunnel tests (Susila I G 2000).

Various international codes of practice including AS1170.2002 (Australia) ASCE7-05 (United States), BS6399 (British) Euro Code 1 EN-1991 (European) identify canopy profiles including Barrel Vaults, Hypars, Mono Pitch and Duo Pitch and may be used as a guide enabling the designer to determine the wind action on the abovementioned canopy profiles.

Tensile Structures are unique in their design.

Within certain constraints the design of Tensioned Structures are only limited by the designer’s imagination. Often the free form design of tensioned roof structures results in canopy profiles that do not fall within the guidelines of international codes. This is particularly evident when a designer is utilizing the conic profile which is not referenced. Conic profiles are commonly used due to the structures stability and aesthetic appeal; however, even small changes in the profile of a conic canopy can significantly alter the loading on the roof canopy, and the zonal distribution of that loading (Burton J 2004).

If you want to learn more about CFD, have a look at Trevor Scott’s Presentation on CFDn to the Lightweight Structures Association of Australasia