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Physics Simulation
Simcenter STAR-CCM+ can model a wide range of physics phenomena including fluid mechanics, solid mechanics, heat transfer, electromagnetism, and chemical reactions. Scenarios with multiple time scales can be solved within the same simulation.
Time
The primary function of the time models in Simcenter STAR-CCM+ is to provide solvers that control the iteration and/or unsteady time-stepping.
Adaptive Time-Stepping
Adaptive time-stepping adjusts the time-step automatically during the run to attain a specified temporal resolution, and can improve the stability and run-time of your simulation and the accuracy of the results. This adjustment is particularly useful for cases with large variations of flow topology, large varying time scales of the physics, or when the mesh is dynamically adapted using Adaptive Mesh Refinement.
Adaptive Time-Step Model Reference
The Adaptive Time-Step model automatically controls the time-step size to improve the quality and run-time of your simulation results. This adjustment is particularly useful for cases with large variations of flow topology, large varying time scales of the physics, or when the mesh is dynamically adapted using Adaptive Mesh Refinement.
LSI Smoothed CFL Reference
The LSI Smoothed CFL is a time-step provider that operates on the Large Scale Interface (LSI) for multiphase simulations. This time-step provider is only accessible when the Adaptive Interface Sharpening (ADIS) scheme is selected under the Volume Fraction Convection.

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Physics Simulation
Simcenter STAR-CCM+ can model a wide range of physics phenomena including fluid mechanics, solid mechanics, heat transfer, electromagnetism, and chemical reactions. Scenarios with multiple time scales can be solved within the same simulation.
- Defining Physics Workflow
  Simcenter STAR-CCM+ contains a wide range of physics models and methods for the simulation of single- and multi-phase fluid flow, heat transfer, turbulence, solid stress, dynamic fluid body interaction, aeroacoustics, and related phenomena. These physics models are all selected using a physics continuum.
- Setting Up Physics
  This section provides information on how to set up physics models in STAR-CCM+.
- Running Physics Simulations
  This part of the documentation describes preparation and procedures for running a Simcenter STAR-CCM+ simulation.
- Motion
  In general, motion can be defined as the change in position of a body with respect to a certain reference frame.
- Space
  The primary function of the Space models in Simcenter STAR-CCM+ is to provide methods for computing and accessing mesh metrics. Examples of mesh metrics include cell volume and centroid, face area and centroid, cell and face indexes, and skewness angle.
- Time
  The primary function of the time models in Simcenter STAR-CCM+ is to provide solvers that control the iteration and/or unsteady time-stepping.
  - Setting High-Accuracy Temporal Discretization
    High-accuracy temporal discretization provides the option of doing 2nd-order time discretization with four or five time levels.
  - Adaptive Time-Stepping
    Adaptive time-stepping adjusts the time-step automatically during the run to attain a specified temporal resolution, and can improve the stability and run-time of your simulation and the accuracy of the results. This adjustment is particularly useful for cases with large variations of flow topology, large varying time scales of the physics, or when the mesh is dynamically adapted using Adaptive Mesh Refinement.
    - Setting Up Adaptive Time-Stepping
      The Adaptive Time-Step model automates the determination of time-step sizes. You define time-step providers that specify the criteria to achieve suitable time-steps for your particular application, and set the appropriate limits, such as minimum and maximum time-step values. The Adaptive Time-Step model uses the specified criteria to determine the appropriate time-step sizes at each stage of the simulation.
    - Adaptive Time-Step Model Reference
      The Adaptive Time-Step model automatically controls the time-step size to improve the quality and run-time of your simulation results. This adjustment is particularly useful for cases with large variations of flow topology, large varying time scales of the physics, or when the mesh is dynamically adapted using Adaptive Mesh Refinement.
      - CFL Reference
        Limits the time-step size to meet the specified target criteria for the Convective Courant Number. This time-step provider is appropriate for transient flow problems.
      - Max Particle Packing Reference
        The Max Particle Packing is a time-step provider within the adaptive time-step framework that reduces the simulation time-step whenever the frictional solid pressure of the dispersed phase exceeds a user-specified threshold value. This time-step provider is valid for granular Eulerian multiphase flow simulations.
      - Free Surface CFL Reference
        Limits the time-step size to allow for a sharp interface. This time-step provider is appropriate for free surface flows when the VOF interface crosses meshes that have different CFL numbers, such as from coarse mesh to fine mesh, or has a changing velocity field.
      - Free Surface Explicit Multi-Step Reference
        Limits the time-step size to allow for a sharp interface when using the VOF Explicit Multi-Step (Deprecated) solver. This time-step provider is appropriate for free surface flows when the VOF interface crosses meshes that have different CFL numbers, such as from coarse mesh to fine mesh, or has a rapidly-changing velocity field.
      - Free Surface Implicit Multi-Step Reference
        Limits the time-step size to allow for a sharp interface when using VOF Implicit Multi-Stepping. This time-step provider is appropriate for free surface flows when the VOF interface crosses meshes that have different CFL numbers, such as from coarse mesh to fine mesh, or has a rapidly-changing velocity field.
      - In-Cylinder Reference
        Limits the time-step size suitable for transient STAR-ICE applications. This time-step provider is used for STAR-ICE applications.
      - Melting-Solidification Reference
        Limits the time-step size to allow for an accurate prediction of the melting/solidification progress.
      - Smoothed CFL Reference
        The Smoothed CFL time-step provider is similar to the CFL time-step provider, but adds smoothing in space. This smoothing is to reduce the potentially detrimental effect of isolated and strongly locally-varying mesh length scales on the overall use of the Courant Number as the time-step size driver.
      - SPH Adaptive Time-Step Providers Reference
        Convective CFL, Gravity CFL, Surface Tension CFL, and Viscous CFL time-step providers limit the time-step size to meet the specified target criteria on Courant number conditions. You use these time-step providers to simulate free surface flows using Smoothed Particle Hydrodynamics (SPH).
      - LSI Smoothed CFL Reference
        The LSI Smoothed CFL is a time-step provider that operates on the Large Scale Interface (LSI) for multiphase simulations. This time-step provider is only accessible when the Adaptive Interface Sharpening (ADIS) scheme is selected under the Volume Fraction Convection.
      - Thermal Diffusivity Reference
        Limits the time-step size to meet the specified target criteria for the Von Neumann number of thermal diffusivity. This time-step provider is appropriate for problems with dominant thermal diffusion with varying magnitude, and also for supporting solid materials.
      - Solid Stress Reference
        The Solid Stress time-step provider optimizes the time-step with respect to a chosen monitor value or calculated displacement change. This time-step provider is suitable for nonlinear solid stress problems such as buckling or impact phenomena.
      - Volumetric Source Reference
        The Volumetric Source time-step provider is appropriate for phase mass transfer from Volume of Fluid (VOF) or Mixture Multiphase (MMP) simulations. This time-step provider adjusts the simulation time-step size based on the phase mass transfer contributions to the source terms of the continuity equation.
  - Choosing Between Steady and Unsteady
    In most situations, the physics being simulated indicates the choice between the Steady and Unsteady (Implicit or Explicit) models.
  - Choosing a Time-Step
    The choice of time-step is an engineering judgment (just like grid refinement). Be sure to understand the time scales of the physical phenomenon.
  - Multiple Time Scales
    Time Scales provide a method for grouping multiple continua together and specifying stopping criteria (and time-step size in case of unsteady modeling) for each continua group. Time scales provide greater granularity for solving problems with multiple time scales where multiple groups of continua must share the same time solver (steady, implicit unsteady, PISO unsteady, and so on) but still require different sets of stopping criteria and time-step size.
- Mesh Motion and Adaption
  Many simulations that involve motion or geometry change require you to move or deform the mesh. Other simulations require localized mesh adaption in order to achieve an accurate solution.
- Materials
  Material models simulate substances, including various mixtures.
- Fluid Flow
  Many engineering design projects require you to predict the effect of flowing fluids on containing structures or immersed objects. While you can analyse simple scenarios with hand calculations, complex scenarios require you to apply numerical methods for accurate solutions.
- Viscous Flow
  Viscous Flow is a finite element approach for use with viscoelastic materials and other highly viscous non-Newtonian fluids, such as liquid plastics and rubber, dough and similar foodstuffs, molten glass, and mud. Viscoelastic materials resemble elastic materials, but also exhibit viscous effects, rebounding slowly from deformations.
- Passive Scalars
  Passive scalars are user-defined variables of arbitrary value, assigned to fluid phases or individual particles. They are passive because they do not affect the physical properties of the simulation. An intuitive way to think of passive scalars is as tracer dye in a fluid, but with numerical values instead of colors, and with no appreciable mass or volume.
- Heat Transfer
  Heat transfer is the study of energy in transit due to a temperature difference in a medium or between media. Heat transfer extends thermodynamic analysis through the study of the modes of energy transfer and through development of relations to calculate energy transfer rates.
- Species
  This chapter provides information about the chemical species models in Simcenter STAR-CCM+. A species model is activated whenever a multi-component liquid or multi-component gas is chosen from the Material model section of the Physics Model Selection dialog.
- Porous Media
  Simcenter STAR-CCM+ allows you to simulate the transport of a fluid or energy (e.g. heat, electrical charge) through porous materials using the concept that the action of the porous media can be represented using appropriate loss (or 'diffusion') coefficients.
- Adjoint
  The adjoint method is an efficient means to predict the influence of many design parameters and physical inputs on some engineering quantity of interest, that is, on the engineering objective of the simulation. In other words, it provides the sensitivity of the objective (output) with respect to the design variables (input).
- Fans and Blowers
  Simcenter STAR-CCM+ provides models for axial and radial fans where classical fan laws apply.
- Virtual Disk Model
  The virtual disk model is based upon the principle of representing propellers, turbines, rotors, fans, and so on, as an actuator disk. The actuator disk treatment is practical when you are concerned about the influence of the rotor/propeller behavior on the flow rather than knowing about the detailed interactions between the flow and the blades of the rotating device.
- Turbulence
  Most fluid flows of engineering interest are characterized by irregularly fluctuating flow quantities.
- Transition
  The term transition refers to the phenomenon of laminar to turbulence transition in boundary layers. A transition model in combination with a turbulence model predicts the onset of transition in a turbulent boundary layer.
- Wall Distance
  Wall distance is a parameter that represents the distance from a cell centroid to the nearest wall face with a non-slip boundary condition. Various physical models require this parameter to account for near-wall effects.
- Radiation
  The Radiation Model is the gateway, or entry point to all of the radiation modeling capabilities of Simcenter STAR-CCM+. This section describes Simcenter STAR-CCM+’s radiation modeling.
- Aeroacoustics
  Aeroacoustics investigates the aerodynamic generation of sound.
- Reacting Flow
  Simcenter STAR-CCM+ provides a selection of models that you can use to simulate a wide range of reacting flow applications.
- Internal Combustion Engines
  In an internal combustion engine (ICE), for example a gasoline engine, the process of combustion takes place in a cylinder (or cylinders) within the engine. The working fluid is a fuel and oxidizer mixture (usually air), which reacts to form combustion products.
- Multiphase Flow
  Multiphase flow is a term which refers to the flow and interaction of several phases within the same system where distinct interfaces exist between the phases. Simcenter STAR-CCM+ considers flow options where phases coexist as: gas bubbles in liquid, liquid droplets in gas, and/or solid particles in gas or liquid, and/or (large scale) free surface flows.
- Dynamic Fluid Body Interaction
  Dynamic Fluid Body Interaction (DFBI) in Simcenter STAR-CCM+ allows you to simulate the motion of a 6-DOF body with the displacement and rotation resulting from the defined mechanical and multiphysics interaction (flow, DEM, solid stress, EMAG).
- Harmonic Balance
  Some unsteady flows have a regularly repeating flow pattern, that is, they are time-periodic. Consider the flow from a fan blade passing across the entrance to a duct. Measurements of the instantaneous flow just within the duct would show a regularly repeating pattern. If the flow disturbances are sufficiently large, and propagate to the end of the duct, measurements of the unsteady flow at any point within the duct show repeating patterns. Such time-periodic patterns can be expressed using Fourier series.
- Solid Stress
  Simcenter STAR-CCM+ allows you to model the response of a solid continuum to applied loads, including mechanical loads and thermal loads that result from changes in the solid temperature.
- Electromagnetism
  Simcenter STAR-CCM+ allows you to model engineering applications involving electromagnetic phenomena. Example applications are electric motors, electric switches, and transformers, which can be modeled based on the classical theory of Electromagnetism.
- Electrochemistry
  Electrochemistry is the study of chemical reactions which occur due to an imposed electrical charge, or a difference in electrical potential at a boundary between a conductor–such as a metal–and an electrolyte. Simcenter STAR-CCM+ provides models that allow you to simulate batteries, corrosion, etching, and other electrochemical reactions.
- Electric Circuits
  Electrical circuits are conducting loops of interconnected electrical components, such as batteries, power sources, resistors, and inductors.
- Plasma
  Plasma is a state of matter similar to a gas that is composed partially or completely of charged particles such as ions and electrons which are not bound to each other.
- Batteries
  You can simulate batteries in Simcenter STAR-CCM+ using battery cells and battery cycling procedures that are defined either directly in Simcenter STAR-CCM+, or in the external software package Simcenter Battery Design Studio.
- Casting
  Casting simulations are performed using transient multiphase simulations using the VOF model with solidification. Conjugate heat transfer is applied between the solidifying melt and the solid mold.
- Region Sources
  This section provides some guidelines on how to use region sources for some common problems.
- Cell Quality Remediation
  The Cell Quality Remediation model helps you get solutions on a poor-quality mesh. This model identifies poor-quality cells, using a set of predefined criteria, such as Skewness Angle exceeding a certain threshold. Once these cells and their neighbors have been marked, the computed gradients in these cells are modified in such a way as to improve the robustness of the solution.
- Guidelines for Applying Simcenter STAR-CCM+
  This part of the documentation provides guidelines on applying Simcenter STAR-CCM+ models to your applications.
- Common Solvers Reference
  In Simcenter STAR-CCM+, solvers compute the solution during the simulation run.

LSI Smoothed CFL Reference

The LSI Smoothed CFL is a time-step provider that operates on the Large Scale Interface (LSI) for multiphase simulations. This time-step provider is only accessible when the Adaptive Interface Sharpening (ADIS) scheme is selected under the Volume Fraction Convection.

The LSI Smoothed CFL facilitates the adaptive lowering of the time-step throughout the simulation by following accuracy constraint of the ADIS scheme. This time-step provider uses the Large Interface Marker Band property as guidance to define the cell layers of the large interface where the time-step is adjusted.

This time-step provider is available when the Eulerian Multiphase (EMP) model is activated in the physics continuum.

Table 1. LSI Smoothed CFL Reference
Provided By	Right-click Continua > Physics 1 > Models > Adaptive Time-Step > Time-Step Providers and select New > LSI Smoothed CFL
Example Node Path	Continua > Physics 1 > Models > Adaptive Time-Step > Time-Step Providers > LSI Smoothed CFL
Requires	Time: Implicit Unsteady Material: Multiphase. Multiphase Models: Eulerian Multiphase (EMP).
Properties	Max Condition Limit, Smoothing Steps, CFL_u Calibration Factor. See LSI Smoother CFL Properties.
Activates	Field Functions	LSI Smoothed CFL Proposal See Field Functions.

LSI Smoothed CFL Properties

Max Condition Limit: The maximum value of the time-step condition. This value is $Φ_{m a x, l i m i t}$ that is used in Eqn. (95). The default value is 0.8.
Smoothing Steps: The number of smoothing steps. This value specifies the number of times that the volume-weighted smoothing operation (Eqn. (94)) is performed. The default value is 1.
CFL_u Calibration Factor: The CFL_u calibration factor is multiplied with the upper CFL limit to obtain the desired maximum CFL number in the Large Interface Marker Band. The default value is 0.8.

Field Functions

The following field function is available when the LSI Smoothed CFL time-step provider is activated.

LSI Smoothed CFL Proposal: The local LSI Smoothed CFL time-step proposal.