Unlocking the secrets of fluid flow, the Ahmed Body benchmark is a cornerstone in automotive aerodynamics. Discover how Ansys Discovery revolutionizes this crucial analysis.
Challenges
One of the primary challenges in external aerodynamics is accurately capturing the complex flow structures around simplified automotive shapes like the Ahmed Body. Variations in turbulence, separation points, and wake formation can significantly impact the accuracy of simulations.
Additionally, ensuring that computational resources are efficiently utilized without compromising the fidelity of the results is a persistent challenge. Balancing computational cost with the need for high-resolution data demands sophisticated simulation tools and methodologies.
Understanding the Ahmed Body Benchmark
The Ahmed Body benchmark is a critical test case in the study of automotive aerodynamics. It provides a simplified yet realistic representation of a car's shape, allowing researchers and engineers to study the effects of aerodynamic forces and flow patterns (Figure 1).
Figure 1. Ahmed Body Benchmark
Developed by S.R. Ahmed in 1984, the Ahmed Body has become a standard for validating computational fluid dynamics (CFD) codes and comparing experimental data. Its straightforward geometry makes it an ideal candidate for understanding flow separation, vortices, and wake behavior behind vehicles.
Engineering Solution
Ansys Discovery offers a robust solution for tackling the challenges associated with the Ahmed Body benchmark. By leveraging its advanced simulation capabilities, engineers can perform high-fidelity aerodynamic analyses with ease.
The use of Ansys Discovery allows for the integration of parametric studies, enabling the optimization of aerodynamic performance by adjusting design variables. This leads to a more efficient and streamlined engineering process, ultimately resulting in better-performing automotive designs.
Ansys Discovery has two distinct modes of simulation; explore mode and refine mode. The former one is designed for rapid design exploration and uses GPU power to provide real-time simulation results. The latter one, on the other hand is used for high-fidelity simulations and leverages CPU-based solvers, such as those found in ANSYS Mechanical or Fluent.
We used both simulation modes on this application. The explore mode is the focus of the current blog.
The fluid regions and the corresponding measures are shown in Figure 2. Note that, a half of the body is utilized, and there are two fluid regions as near field and the far field.
Figure 2. Model Geometry
The symmetry boundary condition was applied to the side walls of the fluid regions where the body was cut into half. Velocity inlet, and zero pressure outlet conditions were imposed. The bottom and the body walls were set to non-slip condition. The rest of the outer flow field walls were set to free-slip condition.
Explore Mode:
The local regions within the near field were set to fine mesh (Figure 3).
Figure 3. Local Fidelity Adjustments
Four different inlet velocities were considered as a parameter. The above local high fidelity adjustments were complimented with about 15% overall solution fidelity (Figure 4).
Figure 4. The Parametric Inlet Conditions, and Overall Fidelity Adjustment (Slider)
The mesh in the explore mode is shown in Figure 5.
Figure 5. Generated Mesh in Explore Mode
The explore mode drag coefficient predictions are compared to the reference1 below:
The range of error is from 1 to 10% which indicates that, the explore mode shows a good correlation with the reference data.
The characteristic "horseshoe vortex system" in the wake region was captured for all inlet conditions (Figure 6).
Figure 6. The Streamlines over the Ahmed Body for all Inlet Velocity Conditions
The calculations were performed in Dell - Precision 5680 laptop computer with i7 processor and NVIDIA RTX 3500 graphics card. The simulations for all of the velocity conditions took about 27 minutes to complete.
Benefits
Utilizing Ansys Discovery for aerodynamic analysis of the Ahmed Body provides several key benefits. It enhances the accuracy of simulations, ensuring that the results are reliable and can be confidently used for design decisions.
The software's intuitive interface and powerful solvers reduce the time required to set up and run simulations, leading to faster turnaround times for projects. This efficiency is crucial in a competitive industry where time-to-market can be a decisive factor.
Ozen Engineering Expertise
Ozen Engineering Inc. leverages it's extensive consulting expertise in CFD, FEA, thermal, optics, photonics, and electromagnetic simulations to achieve exceptional results across various engineering projects, addressing complex challenges like multiphase flows, erosion modeling, and channel flows using Ansys software.
We offer support, mentoring, and consulting services to enhance the performance and reliability of your hydraulic systems. Trust our proven track record to accelerate projects, optimize performance, and deliver high-quality, cost-effective results for both new and existing water control systems. For more information, please visit https://ozeninc.com.
The following video walks through the details of the model, settings, and simulation results
The video can be reached from Ozen Engineering YouTube Channel: External Aerodynamics over Ahmed Body Benchmark with Ansys Discovery-Explore