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It’s no secret that the automotive industry is undergoing one of the biggest disruptions in history. In the race for efficient, sustainable, yet attractive individual mobility solutions, vehicle aerodynamics CFD is an important factor already today. And it will become even more relevant in the future.

Reducing energy consumption requires analyzing all aerodynamically relevant components for the World harmonized Light-duty vehicles Test Procedure (WLTP). Moreover, the electrification of vehicles comes with a need for further reduced aerodynamic resistance to extend driving ranges and recuperation efficiency due to lower drag. This implies the development of active aerodynamic devices to adjust for different driving conditions. Likewise, with less noise stemming from the powertrain, aeroacoustics will play a major role in cabin noise and passenger comfort. And with the continuous establishment of autonomous drive systems,s it is a mandatory safety requirement to keep sensors and cameras clear from soiling under all weather conditions—a topic directly related to water management coupled to aerodynamics. In consequence, all this adds up to a further significant increase in vehicle development complexity.

Therefore, the key for any automotive company is to turn this complexity into a competitive advantage. Something that can only be done by leveraging digital product development.

Accelerate innovation with fast and accurate vehicle aerodynamics CFD simulations

Without a doubt, physical wind tunnel tests remain a viable tool for any vehicle assessment. It is crucial as the ultimate validation tool late in the development cycle and relevant for early singular prototype assessments. However, with high operating costs on the one hand and the need to assess thousands of aerodynamics variants and conditions, it needs to be complemented by virtual development methods.

The digital wind tunnel is a key development tool for efficient vehicle aerodynamics.

Computational fluid dynamics CFD simulation is the key technology to predict and understand real-world aerodynamics behavior. Based on that, engineers can explore many design variants in search of optimum solutions in the most cost-efficient manner. However, the precondition for such virtual aerodynamics engineering is an accurate prediction of drag and lift forces. This includes the precise quantification of the performance impact of components such as wheels, mirrors, spoilers, etc. Furthermore, relevant aerodynamics CFD must allow for the assessment of innovative aerodynamic concepts early in development. Based on that, CFD has to report the aerodynamic impact of optional equipment, which is a requirement for WLTP certification.

Simcenter STAR-CCM+ is a multiphysics computational fluid dynamics (CFD) simulation software that allows users to build a high-fidelity, comprehensive digital twin. The latter allows to assessment and optimize the aerodynamic performance of a vehicle before building any physical prototype. It uniquely integrates every step of the simulation process, from geometry preparation to volume meshing, solving, and postprocessing. It thereby enables engineers to quickly assess the impact of configuration or design changes on aerodynamic performance.

Quickly prepare complex geometries for vehicle aerodynamics CFD simulations.

Simcenter STAR-CCM+ offers the ability to handle even the most complex geometries, including complete vehicle assemblies of thousands of parts with minimum user effort. CFD engineers can leverage a tight link to CAD programs for bi-directional data transfer including parameters and meta-data. Alternatively you can use a high-quality neutral or native CAD import.

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Fast and easy geometry preparation is a key for efficient vehicle aerodynamics CFD simulations.

You can further reduce the preprocessing time for an aerodynamic CFD simulation using a fully automated meshing pipeline. Surface wrapping is a robust and fast surface preparation approach that converts complex input geometries into a clean, ready-to-volume-mesh, watertight surface.

The trimmed cell meshes offer great scalability even on high core counts and low memory consumption. In conjunction with the prism layer meshes that are easy to use and robust to generate low y+ meshes on exterior surfaces,  are the first choice external aerodynamics simulations are the first choice. You can easily refine the volume mesh in critical areas such as wakes with user-defined shapes for further fidelity. Parallel meshing for all cell topologies (poly, trim, prism) helps to generate meshes quickly.

All this results in reducing preparation time for a vehicle aerodynamics CFD simulation from weeks to hours, freeing up the time of the CAE aerodynamicist to the thing that really matters: Engineering superior aerodynamics solutions.

Increase throughput with fast and accurate vehicle aerodynamic CFD simulations

Even the fastest process is of no value if the results are not accurate enough to drive valuable engineering decisions. CFD Simcenter STAR-CCM+ offers industry-relevant validated physics models for external vehicle aerodynamics, getting consistent and accurate results. A full suite of turbulence models allows engineers to capture skin friction accurately and separated flow dynamics and turbulent structures in the vehicle wake. Density-based coupled solutions of mass, momentum and energy equations ensure robust convergence. Low y+ meshes on crucial surfaces accurately capture boundary layer phenomena and enable the prediction of flow separation.

Simcenter STAR-CCM+ offers two simulation approaches: A steady-state Reynolds-averaged Navier- Stokes (RANS) allows for the faster running simulation used for design studies.

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Steady-state Reynolds-Averaged Navier- Stokes (RANS) aerodynamics CFD simulation for quick insights. A precondition to explore 1000s of design variants on a competitive time-scale

While more computationally expensive, you can use unsteady Detached Eddy Simulations DES when detailed insight is needed about transient flow phenomena. This enables engineers to run high-fidelity, transient vehicle aerodynamics CFD simulations.

Detached Eddy Simulations including wheel rotation to gather detailed insights into transient vehicle aerodynamics

Ultimately the tool offers all required capabilities to create a validated digital wind tunnel for your vehicle aerodynamics development work.

Maximize your throughput through proven scaling and automated solver adjustment

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Vehicle aerodynamics CFD simulation in Simcenter STAR-CCM+ 13

To speed-up aerodynamics CFD simulations Simcenter STAR-CCM+ offers parallel volume meshing and excellent solver scalability on computational clusters up to very high core-counts, ready to leverage CFD in the cloud. The built-in solution acceleration features make the coupled solver robust and yet fast without any user intervention or tuning. On top grid sequencing initialization provides more accurate initial conditions to further boost the time to results.

Speed is everything in racing and aerodynamics engineering.

Save engineering time by automating vehicle aerodynamics

Built for process automation, Simcenter STAR-CCM+ reduces setup time with an end-to-end workflow within a single environment. Based on this, aerodynamic engineers benefit from using a dedicated vehicle aerodynamics workflow or macro-based automation. This enables you to generate aerodynamic databases without requiring any user customization easily.

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Simcenter STAR-CCM+ is built upon the philosophy of fully integrated CAD-to-results automation.

Explore the possibilities through integrated Design exploration and surface sensitivities for drag

Based on a fully automated CAD-to-result end-to-end solution, the – again fully integrated – intelligent design exploration tools make it easy to run automated design exploration studies. Leveraging an unbeaten hybrid and adaptive search algorithm, aerodynamics CFD engineers can explore designs that minimize drag while maintaining constraints on aerodynamic balance. All this without being an expert in optimization and without the need for any external software tools.

Design exploration study on the aerodynamic impact of the rear wing design

On top, based on the adjoint technology, aerodynamicists get immediate detailed insight into surface sensitivities concerning drag coefficients for a given design variant. Those insights could be used to identify areas of high relevance to the aerodynamic performance that could then undergo design exploration studies or be directly used for local design refinements.

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Go beyond aerodynamics in one integrated CFD software

Today’s vehicle aerodynamics can no longer be taken out of the context of various other engineering challenges associated with it. When designing a vehicle, engineers need to balance aerodynamic performance in lift and drag, the impact of wind loads on structural mechanics, thermal management, water management, and aeroacoustics.

And even if these disciplines might be tackled by various expert teams due to their respective complexity, it is key for any automotive company to ensure the best possible software platform for this cross-domain collaboration. As a multiphysics computational fluid dynamics (CFD) simulation software, Simcenter STAR-CCM+ offers a unified solution that allows capturing the whole range of associated engineering challenges.

Assess structural impacts with fluid-structure-interaction FSI

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Execute fluid-structure-interaction (FSI) simulations to calculate the deformation of components due to pressure loads

Improve vehicle safety through water management

Multiphase CFD simulation-based design exploration to assess side mirror sensor soiling for various designs

With a huge range of multiphase models, Simcenter STAR-CCM+ allows extending aerodynamics simulations to complex multiphase scenarios to investigate water management, including soiling, wading, wipers, etc.

Balance and optimize cooling performance and aerodynamics

Adjoint-based topology optimization of a brake-cooling-duct.

Within the same tool, engineers can not only assess single-phase fluid dynamics or multiphase water management: Simcenter STAR-CCM+ also handles solid components for any Conjugate Heat transfer problem. This includes cabin comfort, powertrain thermal management, or any other cooling problem, like the brake cooling problem above.

Increase passenger comfort through aero-acoustic simulations

Side mirror aeroacoustics CFD simulation

Based on high-fidelity aerodynamics CFD simulations, engineers can take it even further to analyze aeroacoustics phenomena such as side mirror noise.

Learn more about Simcenter STAR-CCM+ vehicle aerodynamics CFD simulation in this Webinar series

Disclaimer: I am the author at PLM ECOSYSTEM, focusing on developing digital-thread platforms with capabilities across CAD, CAM, CAE, PLM, ERP, and IT systems to manage the product data lifecycle and connect various industry networks. My opinions may be biased. Articles and thoughts on PLMES represent solely the author's views and not necessarily those of the company. Reviews and mentions do not imply endorsement or recommendations for purchase.

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