Flow Design

Fluid dynamics simulations

Introduction

In the previous workshops we made a design based on program, functionality, concept, location and architectural formal and spatial qualities. These criteria and constraints are only a few of the factors which are integrated in the design process. Because the design is made in a digital environment it can use a wide range of different software programs which can add additional support to the design process to further enhance the quality of the design. Due to the exponential development of computer power and fast development of more efficient software the range of capabilities which are available for the designer are increasing rapidly. Interesting is that simulation and analysis software is entering the realm of the concept design phase. This enables the designer to simulate and analyze in various ranges of accuracy physical properties of the design. Like loads within the structure, lighting conditions in spaces, energy analysis and wind simulations. Because this capability is available from the early stages of the design their data can be used to enhance the quality of the design decisions made in these early stages of the design process, thereby having a fundamental impact on the design. This is a part of performative design.

Fluid Dynamics

Fluid Dynamic simulations are the latest member in a wide range of simulation and analysis tools which came available for the designer in the concept architectural design phase. The reason for this late entry is the complexity of the simulations. New development in the mathematics behind the calculations and increased computing power makes it now possible to simulate wind flow around object like buildings. Although the accuracy is still limited in the tools used in the concept design phase, the data generated from the simulations can give useful insight of positive or negative effects of air moving around or in the designed building. For more accurate analysis, calculations are made with advanced wind simulation software often in combination with a wind tunnel to verify the data generated by the software.

The Fluid Dynamics simulation uses a special type of geometry to make the fluid calculations possible, called voxels (volume pixels). These are 3 dimensional pixels, basically a set of cubes nicely stacked into a container. Every cube will contain the mathematically defined properties of a fluid and therefore behave like a particle of fluid. A cube (voxel) will behave like one mathematically defined object, calculating the forces, pressure and temperature placed on the cube and then emitting the result to its neighboring cubes. Transmitting effects of heat, pressure and movement throughout the container holding all the cubes. The container is used because it limits the volume which is calculated. This speeds the calculations up and it will define at its boundary the speed, pressure and heat of the fluid set by the user. The result from these settings will then cascade from the boundary layer through the cubes which will recognize if there are any objects within the container which will influence the calculations.

The size of the container and the size of the cubes(voxels) will determine the effort it will take to calculate the result. If the container remains the same and the voxel size decreases by half its length,width and height then the calculation time will increase 8 fold. 2 times 2 times 2. An option could be to use the same amount of voxels but decrease the size of the container. This has however its limits because fluids are effected by its surrounding and by their neighbor voxels, the less information is integrated from its surrounding and neighboring voxel the less accurate the result will be. This limitation at this moment is a result of the computing power it takes to calculate the simulation.

The Fluid Dynamic simulation can, for example, give information about:

• Potential for natural ventilation through various wind speed and pressures in and outside the building.
• Energy generation by optimizing the form of the building to focus the wind in an area where energy is extracted from it.
• Hindrance due to wind, where wind speeds are to high at certain areas around the building.

Flow Design

For this course we use Flow Design. It is relatively simple to use Fluid Dynamic simulator which can help to determine how the wind moves around the designed building.