Upgrade to Ansys Fluent with a Native GPU Solver?

September 20, 2023 Alex Lefebvre

Is it time to upgrade?

Since Ansys released the latest multi-GPU solver in its Fluent CFD software in January 2023, there has been a lot of talk about how much it speeds up calculation times. As an Ansys Elite Channel Partner at the forefront of simulation-driven design, we wanted to run comparison tests ourselves, so we could make recommendations via first-hand experience.

Based on our tests, companies that switch from running CFD simulations on CPU solvers to Ansys Fluent with a Native GPU solver can expect to see a significant increase in simulation throughput for a minimal financial investment.

Here are highlights of the tests and results. For details, watch this recorded webinar.

About the tests

Test Setup

Simulations were run for a variety of mesh sizes, cell types, solver settings, and physics using the new native Ansys Fluent GPU solver. Comparison runs were performed using Rand Simulation’s high-performance CPU cluster.

We ran our CPU simulations on Rand SIM’s CFD cluster:

  • CPU: Xeon® Gold 6242
  • MSRP: $3000 + RAM + Motherboard
  • CPU Drivers: N/A

We ran our GPU simulations on prep/post machines:

  • GPU: Quadro RTX8000 and RTX4000
  • MSRP: $5,000 and $1,800 respectively
  • GPU Drivers: Release 5/11/23, Version 30-0-14-7444

We recorded all times after convergence was achieved.

Case studies (*Simulation imagery below)

Type:
External Flow
Over Passenger Vehicle
Internal Flow
in Mixing
Tank
Compressible Flow in Generic Combustor
Vehicle
Exhaust
Model
Size:
2M cells
4M cells
24M cells
33M cells
Cell Type:
Projected Octree
Polyhedral
Poly-hex
Mixed
Solver:
Pressure-based segregated solver, Least Square cell-based, steady
Pressure-based segregated solver, Least Square cell-based, steady
Pressure-based segregated solver, Least Square cell-based, steady
Pressure-based coupled solver, Least Squares cell based, steady
Models:
GEKO k-omega Turbulence
GEKO k-omega Turbulence, MRF
GEKO k-omega Turbulence, Ideal gas compressible
SST k-omega Turbulence


Our findings

Test 1 – External Flow Over Passenger Vehicle: GPU solver, about as fast as 25 CPU cores

Test 2 – Internal Flow in Mixing Tank: GPU solver, about as fast as 32 CPU cores

Test 3 – Compressible Flow in Generic Combustor: GPU solver was roughly as fast as 90 CPU cores

Test 4 – Vehicle Exhaust Model: GPU solver was as fast as 70 CPU cores

Limitations

As an Ansys Elite Channel Partner, our goal is to support our customers’ growth. By sharing a clear picture of software advancements and limitations, we hope to educate current and prospective customers, so they can make more informed decisions.

A summary of our findings:

  • Coupled solver is coming in a future release, only segregated solver available currently

    • This will allow for more stable simulations, at the cost of a small reduction in speed and memory usage

  • Not all reports are accessible at runtime

  • Hybrid initialization was somewhat unstable

  • No pressure far-field boundary condition

  • Slightly slower to initialize (by roughly a minute)

  • Multiple users on a machine was detrimental to GPU performance

Recommendations

Teams that prefer working with state-of-the-art technology, need faster simulations, and can live with the additional limitations of using the GPU solver, should take a serious look at the Ansys Fluent native GPU solver.

For an investment of less than $10,000 (the GPU at $1,800 and upgrade from Premium to Enterprise at $7,000), first-year paid-up costs, companies will greatly improve their productivity, innovation, and ability to answer questions in minutes or hours instead of days.

Ready to discuss your specific situation? Contact us today.

*Sample simulation imagery

External Flow Over Passenger Vehicle


Internal Flow in Mixing Tank

Compressible Flow in Generic Combustor


Vehicle Exhaust Model

About the Author

Alex Lefebvre

CFD Simulation Specialist<br><br>Alex collaborates with clients to find solutions that meet their needs, whether it be new software, technical training, or consulting services. He completed his Ph.D. in Mechanical and Aerospace Engineering at the University of Miami, with a focus on aircraft design. After the completion of his Ph.D., Alex worked in Formula 1 as a CFD expert where he helped the team produce a car that finished 5th in the world's championship.

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