Aerodynamics

PowerFLOW is the simulation tool that provides a true Digital Wind Tunnel™ solution for aerodynamic optimization. PowerFLOW’s unique advantages for the simulation of external and internal aerodynamics has made Exa the clear leader in this application. It is the dominant solution worldwide for accurate aerodynamic simulation of even the most complex models.

PowerFLOW’s key features – fast turnaround, full geometric detail, and transient analysis – have transformed fluid flow simulation into a truly productive design tool and changed the way aerodynamic development is performed. For example, in the automotive industry, insight gained from PowerFLOW simulations has led to significant design optimizations resulting in improved fuel consumption (due to lower drag coefficients), improved stability (due to lower lift coefficients) and a host of other benefits ranging from increased passenger comfort to a reduction in parts cost.

Dealing with real-world models, design iterations made easy...

The geometry for PowerFLOW simulations can be created from the CAD models, styling concept tools or a scan of a physical prototype, without any need to simplify or idealize the geometry. This greatly reduces the time required to build the simulation model and preserves all geometric details, which is a key advantage in aerodynamics where small geometric details often have a significant impact on the aerodynamic characteristics of a vehicle. It typically takes mere days to create an aerodynamic model of a passenger vehicle including complete underbody and underhood detail – far less time than required to build a comparable wind tunnel model (and at a significant cost savings).

Complex geometry handling, like that of this BMW motorcycle, is key to accurate aerodynamic simulation results.

In addition, Exa’s unique morphing tool, PowerCLAY, allows you to quickly create high quality geometric variations based on of the initial simulation model, thus allowing a thorough exploration of the design space and the determination of the optimal shape of the vehicle through Design of Experiment and other optimization techniques.

Exa PowerCLAY allows for quick part creation for quick and easy aerodynamic design optimization.

A wealth of data

The true value of PowerFLOW simulations is most evident in the extensive data analysis methods that allow you to visualize flow features at all points around the model. This allows you to detect aerodynamic problem areas, such as regions of separated flow or areas with high surface pressures, and see a complete picture of the opportunities for drag and lift reduction for a vehicle. In a physical wind tunnel, most of this information is not available because the techniques to collect experimental data are so limited.

The aerodynamic analysis techniques available in PowerFLOW include:

• Surface pressure images and surface streamlines to identify areas of flow separation and detect undesirable regions of high pressure or low pressure
• Detailed flow structures through isosurfaces of quantities such as total pressure or the depiction of the flow properties on arbitrarily positioned slice planes in the flow domain.
• Animations: PowerFLOW simulations are always unsteady, and the transient development of all flow phenomena can be depicted through a number of powerful animation techniques.
• Transient drag and lift analysis for vehicles, including the ability to identify the contribution to overall forces from every single component. Exa’s unique drag development charts show how each area of the vehicle contributes to drag and lift along each of the axes of the geometry.

External aerodynamic simulation of Tatuus motorsports racecar. Collaborative engineering is made easier PowerFLOW data is easily visualized with PowerVIZ on surface of model as well as slices across vehicle wake. Image courtesy of Tatuus.

The Digital Wind Tunnel™

PowerFLOW includes a full Digital Wind Tunnel – an extensive template for aerodynamic simulations that dramatically reduces the time required for simulation setup. The user simply imports all geometry components of the model, defines areas of higher resolution, sets boundary conditions, and defines measurement regions – and then is ready to start the simulation, including the fully automatic mesh generation process.

During the concept and design selection phase early in the vehicle development process, many of Exa’s customers have replaced the traditional experimental process based on scaled-down windtunnel models with a process based entirely on PowerFLOW's Digital Wind Tunnel.

The Digital Wind Tunnel also has the ability to perform full road simulations, i.e., simulations with rotating wheels and moving ground (another advantage of a PowerFLOW-based process as these features are typically not available in scale wind tunnels).

One of the key advantages of this digital process is the ability to carry out all simulations beginning in the initial stages of the development process with fully detailed models, including full underhood and underbody detail. In this way, cooling airflow requirements are taken into account concurrently with the aerodynamic development – avoiding the difficult and costly changes often required in the traditional process where cooling airflow requirements are only considered after the external shape of the vehicle is fixed.

Validation

PowerFLOW’s ability to accurately capture the true aerodynamic characteristics of a vehicle has been validated in a multitude of real world cases provided by our customers as well as a variety of academic cases. Extensive experimental measurements – surface oilflow images, surface pressure measurements, and velocity and pressure measurements in the flow field – are available for most of these cases and have been compared extensively to PowerFLOW simulation results. Complete documentation of these comparisons is available to our customers at the Exa User Center.

Extensive papers on Exa's technology, aerodynamic approach and real world applications, please click here.