Loading the Starting Simulation File

You start this tutorial by loading a simulation file that includes the geometry of the HVAC duct, mesh operations that create the flow domain and generate a trimmed mesh, physics continua for a steady RANS and an unsteady LES simulation, and regions including boundary types. Two-sequences of simulation operations are set up to automate the processes of running a RANS simulation followed by an LES acoustics simulation.

Due to the large number of cells and the time it takes the solver to run, you are advised to launch Simcenter STAR-CCM+ on a multi-core machine with 6 cores or more.
To load the starting simulation file:
  1. Start a double-precision version of Simcenter STAR-CCM+ and select File > Open.
  2. In the Load a File dialog:
    1. Select an appropriate parallel option and set Compute Processes to at least 6.
      For more information on parallel options, see Process Options.
    2. Click Browse.
    3. In the Open dialog, navigate to the aeroacoustics folder of the downloaded tutorial files and select simplifiedHVACduct_start.sim.
    4. Click Open, then OK.
  3. Save the simulation as simplifiedHVACduct_run.sim
Expand the following nodes and review some of the pre-defined settings:
Geometry


The following parts are available:

  • Closures & Refinements—a composite of supporting parts that are required for the creation of the flow domain and for the definition of mesh refinement zones.
  • Geometry—a composite that contains the geometry of the HVAC duct, the intake plenum, and the test chamber.
  • Working Parts - do not modify—a composite that contains the output parts of the geometry operations.

Geometry operations use these parts to automatically create the flow domain for the RANS simulation (Air RANS) and a duplicate for the LES simulation (Air LES).

Automated mesh operations (Mesh RANS and Mesh LES) are set up to remesh the surface of these flow domains and to generate trimmed volume meshes with prism layers on the walls.

Continua


The simulation requires two physics continua:

  • RANS—contains the necessary models for computing a steady RANS solution for incompressible fluid flow.
  • LES—contains the models for running an unsteady LES simulation. You add the acoustics models later in this tutorial.
Regions


The starting file contains two regions:

  • RANS—represents the fluid domain including the intake plenum, the internal volume of the HVAC duct, and the test chamber. The following boundaries are available:
    • Inlet—a mass flow inlet boundary with a mass flow rate of 0.0075 kg/s.
    • Outlet—a pressure outlet boundary with a pressure of 0.0 Pa.
    • Intake Wall—a wall boundary with slip condition.
    • Walls—a wall boundary with non-slip condition.
  • LES—a duplicate of the RANS region for the subsequent LES acoustics simulation.
Automation > Simulation Operations


Two sequences of simulation operations automate the simulation process:

  • 01_RANS—this sequence automates the steady RANS simulation using the following operations:
    Simulation Operation Description
    Clear Clears all data fields from the solution.

    This operation is typically applied at the start of a sequence.
    Set Base Size RANS Sets the value of the scalar global parameter BaseSize_RANS, which is defined within the Automation > Parameters node.

    This parameter is used to set the base size in the mesh operation Mesh RANS.
    Set Base Size LES Sets the value of the scalar global parameter BaseSize_LES, which is used to set the base size in the mesh operation Mesh LES.

    This operation is required for running the subsequent mesh operation Mesh, which runs the complete meshing pipeline including the Mesh LES operation.
    Mesh Launches the volume mesh generation.
    Solve RANS Runs the solvers associated with the time scale Steady Time Scale, which is defined within the Automation > Time Scales node.

    This time scale applies to the RANS continuum and runs the simulation for 1000 iterations.
    Store RANS data Executes the data mapper RANS Storage, which is defined within the Tools > Data Mappers node.

    This data mapper maps the computed pressure and velocity fields from the RANS region onto itself. This way, the computed data fields are stored in mapped data fields, which remain available even when the solution is cleared.

  • 02_LES—this sequence automates the unsteady LES simulation using the following operations:
    Simulation Operation Description
    Clear As for 01_RANS.
    Set Base Size LES
    Mesh
    Map stored RANS data to LES Executes the data mapper RANS to LES Mapper.

    This data mapper maps the previously stored pressure and velocity fields from the RANS region to the LES region.

    The mapped values are used for initialization of the LES simulation.
    Solve LES Runs the solvers associated with the time scale Implicit Unsteady Time Scale.

    This time scale applies to the LES continuum and runs the simulation for 0.09 s physical time using 10 iterations per time-step.

For convenience, you are also provided with several pre-defined derived parts, reports, and scenes.