When to Use 1D Vs. 3D Simulation

Today’s simulation and analysis (S&A) tools allow engineers to study and verify system/machine properties and visualize the aerodynamic, thermodynamic, structural, and other physical properties without having to build a physical prototype. We can perform cooling secondary flow systems analysis in a gas turbine; a detailed performance study for a supercritical CO2 turbine/compressor; predict cavitation for industry a water pump/rocket turbopump; and so many more. Products and machines are becoming more and more complex. Unfortunately, engineers only run a handful of designs through the S&A process, due to the cost associated with limited computer resources and the time required to run simulations and to create complex 3D models of designs. Furthermore, verification and certification of system designs are often done using actual hardware—a costly and time-consuming endeavor. Considering these aspects, 1D and 3D simulations are significantly important. However, engineers need to determine the trade-off between 1D and 3D simulation.

Figure 1 AxSTREAM Platform with Modules from 0D to 3D including seamless geometry import into STAR-CCM+

1D Simulation

Imagine what’s required to generate one 3D design for a gas turbine secondary cooling flow system, and multiply it by 1,000 design alternatives. Even if we were to only use conceptual CAD models, this project would require extraordinary computing power and data storage—not to mention simulation and design expertise.

And so, even with the movement to bring more cloud-based S&A tools to market, resources required for 3D modeling will still result in very few designs being extensively explored, thanks to their complexity. Detailed low-dimensional models of system behavior can provide valuable insights into system performance and function thus guiding the design process.

1D simulations aim to increase system efficiency, by helping engineers understand the interaction of the different components within the system. The process of building a model for a system consists of a few steps:

  1. Input the correct components and link them together;
  2. Assign the correct physical models to the different components (e.g. simplified turbomachines/heat-exchangers, pipelines, chambers, resistance etc.);
  3. Enter the correct parameters for the physical models; and
  4. Run the simulation.

Each component is simulated separately with its own input and parameters. This means that the model gives an accurate display of the performance of the system, because it takes the interactions of the different components with each other into account as well.

Gas Turbine Secondary Cooling Flow System 1D Simulation in AxSTREAM NET
Figure 2 Gas Turbine Secondary Cooling Flow System 1D Simulation in AxSTREAM NET
Figure 3 Complete Gas Turbine Cycle 1D Simulation in AxCYCLE
Figure 3 Complete Gas Turbine Cycle 1D Simulation in AxCYCLE

3D Simulation

So what makes a 1D simulation different from a 3D simulation and why should you consider it? The main difference here is that 3D simulations show the interaction of individual components with their surroundings, whereas 1D simulations show the entire design of a system and the interactions of the different components of this larger system. This makes a 1D simulation excellent for optimizing the design of an entire system, while a 3D simulation is great for determining the optimum design characteristics of individual components like flow pattern around a blade or heat transfer with internal cooling air and external hot gas. Also, a 3D simulation can be used to validate 1D simulation results, for example: pump cavitation prediction on a NPSH map.

Figure 4 Blade Cooling 3D Simulation in STAR-CCM+
Figure 5 Water Pump 1D NPSHr Map in AxSTREAM (left) and 3D Cavitation Simulation in STAR-CCM (right)
Figure 5 Water Pump 1D NPSHr Map in AxSTREAM (left) and 3D Cavitation Simulation in STAR-CCM+ (right)

A 3D CFD model would be the most detailed model of the aero/thermal characteristics of the turbomachines. A typical CFD model of the turbomachine would divide the fluid region into a 3D mesh, and then use a set of equations and turbulence models to evolve the temperature and velocity in each segment of the mesh. To produce meaningful results, the CFD model requires knowledge of the precise geometry of the blade or flow path.

Regarding 3D models, AxSTREAM can generate designs from scratch for various types of all turbomachines and export 3D models in different formats for engineers to use in different tools they use. This gives engineers more time to spend diving into design space exploration instead of sketching models in CAD.

System-level simulation is a tool that can be used across the entire development cycle, from initial design to testing or optimization. This means that information can be transferred across one platform and the risk of miscommunication is reduced. Simulation allows you to thoroughly prototype your product digitally, reducing the extent and costs of physical testing without compromising quality. These are just some of the benefits that make 1D simulation, a great tool for engineers.

It’s also true that 1D models do not have the same level of fidelity as 3D models, and it’s often not possible to study all pertinent behaviors using a 1D model alone. A 3D simulation would be the best choice when the goal of space exploration design is to study the interaction of individual components with their surroundings.

SoftInWay provide turbomachinery solutions with AxSTREAM and STAR-CCM+ including 0D to 3D modules for different kinds of simulation. If you want to learn about more details,  email us at Info@softinway.com or request a trial here!