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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.
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.
Solid Stress and Energy Reference
Solid Stress Model Reference
The Solid Stress model allows you to compute the displacement of solid structures under loads, using the finite element approach. This model is the prerequisite for all types of stress analysis.
Rayleigh Damping Model Reference
The Rayleigh Damping model introduces physical damping of a structure. The damping is frequency dependent. Simcenter STAR-CCM+ provides two damping coefficients: one to damp low frequencies ( $f_{M}$ ), and one to damp high frequencies ( $τ_{K}$ ).

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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.
- 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.
  - General Workflow for Stress Analysis
    The following steps outline the recommended workflow for stress analysis in Simcenter STAR-CCM+. These steps assume that you are already familiar with general Simcenter STAR-CCM+ tasks, such as creating parts, assigning parts to regions, or creating reports and scenes.
  - Analyzing Normal Modes
    In solid mechanics, the normal modes of a solid structure describe the free vibrational motion of the structure at its natural (or resonant) frequencies. The free modes of vibrations of a structure govern its dynamic response to external forces and have an impact on its stress characteristics.
  - Fluid-Structure Interaction (FSI)
  - Deformable DFBI Bodies
    In Simcenter STAR-CCM+, the DFBI framework allows you to simulate the motion of a rigid body in response to external forces. In FSI simulations, you can use DFBI in conjuction with the solid stress solver to model deformable or partially deformable DFBI bodies. The DFBI module calculates the overall rigid body motion, while the solid stress solver computes the local deformations.
  - Solid Stress and Energy Reference
    - Solid Stress Model Reference
      The Solid Stress model allows you to compute the displacement of solid structures under loads, using the finite element approach. This model is the prerequisite for all types of stress analysis.
      - Solid Stress Solver Reference
        The Solid Stress Solver node allows you to access computation parameters, such as the Sparse Direct Solver settings, the update method for the stiffness matrix in nonlinear applications, and the Static Analysis option for quasi-static analysis with the Implicit Unsteady model. The Solid Stress Solver node also allows you to estimate the simulation memory requirements.
      - Solid Stress Load Step Solver Reference
        In simulations with nonlinear geometry or nonlinear materials, you can improve convergence using the Solid Stress Load Step solver. This solver applies external loads incrementally over several iteration steps in steady simulations, or over several time-steps in unsteady simulations.
      - Material Law Models Reference
        The Material Law Models define the relationship between stress and strain in the solid material. Simcenter STAR-CCM+ supports linear elastic materials and elastoplastic materials with either isotropic, orthotropic, or anisotropic properties, and isotropic hyperelastic materials.
      - Nearly Incompressible Material Model Reference
        By default, Simcenter STAR-CCM+ treats solid materials as compressible. This approach is suitable for linear elastic materials with Poisson's ratio $ν \leq 0.45$ and some hyperelastic materials such as highly compressible foams. To account for nearly incompressible solids, whose volume does not change significantly with increasing stress, Simcenter STAR-CCM+ provides the Nearly Incompressible Material model.
      - Rayleigh Damping Model Reference
        The Rayleigh Damping model introduces physical damping of a structure. The damping is frequency dependent. Simcenter STAR-CCM+ provides two damping coefficients: one to damp low frequencies ( $f_{M}$ ), and one to damp high frequencies ( $τ_{K}$ ).
      - Flexible DFBI Motion Model Reference
        The Flexible DFBI Motion model allows you to combine the solid stress solver with the DFBI module to model deformable DFBI bodies in FSI simulations.
      - Specified Temperature Model Reference
        The Specified Temperature model allows you to apply temperature profiles on solid regions.
      - Nonlinear Geometry Model Reference
        The Nonlinear Geometry model allows you to model nonlinear phenomena, such as large displacements and rotations, and loads applied on slender parts in either tension or compression.
      - Coriolis - Solid Displacement Velocity Effect Model Reference
        The Coriolis - Solid Displacement Velocity Effect model adds the Coriolis acceleration component (the acceleration due to the simultaneous rotational and translational motion and deformation of the body) to the acceleration of the body due to inertial loads and rigid body motions.
      - Segments (Loads and Constraints) Reference
        A segment represents either a load or a constraint on a collection of part surfaces, curves, or points. All segments appear under the [Solid Region] > Segments node.
      - Solid Stress Normal Modes Reference
        The Solid Stress Normal Modes model and solver allow you to perform a normal mode analysis on a solid structure.
      - Normal Modes View Reference
        The Normal Modes View node controls the properties of a normal mode solution view for the selected eigenmode.
    - Finite Element Solid Energy Model Reference
      The Finite Element Solid Energy model allows you to solve for the solid temperature using the finite element approach. This model supports mapped contact interfaces with finite volume fluid regions for conjugate heat transfer analysis. This model is designed to work with the Solid Stress model, which can calculate the solid displacement due to thermal expansion.
  - Mesh Requirements and Guidelines
    Finite element stress analyses in Simcenter STAR-CCM+ require a mesh of 3D solid elements generated using parts-based mesh operations, or imported as a CAE model. Simcenter STAR-CCM+ supports hexahedral, tetrahedral, wedge, and pyramid element types. Each type is available without mid-side nodes (linear element), or with mid-side nodes (quadratic element).
  - Solution Analysis Guidelines
    Simcenter STAR-CCM+ offers various field functions and tools that you can use to visualize the solution and monitor the relevant quantities. For example, you can visualize the deformed geometry and the stress and strain distribution throughout the solid structure.
  - Bibliography
- 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.

Rayleigh Damping Model Reference

The Rayleigh Damping model introduces physical damping of a structure. The damping is frequency dependent. Simcenter STAR-CCM+ provides two damping coefficients: one to damp low frequencies ( $f_{M}$ ), and one to damp high frequencies ( $τ_{K}$ ).

Where modal data is available, you can calculate the Rayleigh coefficients [132] based on the most significant modes of oscillation, using Eqn. (4586). This damping is an approximate fit to the asymptotic behavior at the high frequency prescribed by the stiffness proportional damping, and the asymptotic behavior at the low frequency prescribed by the mass proportional damping. So if you determine the damping at two different frequencies, you can calculate the damping coefficients. This fit is only an approximation of the real damping in the structure.


Theory	See Rayleigh Damping.
Provided by	[physics continuum] > Models > Optional Models
Example Node Path	Continua > [Solid Continuum] > Models > Rayleigh Damping
Requires	Physics models: Implicit Unsteady Solid Stress
Properties	Key properties are: Mass Damping Coefficient and Stiffness Damping Coefficient. See Rayleigh Damping Model Properties.

Rayleigh Damping Model Properties

Mass Damping Coefficient: Specifies the low frequency damping coefficient $f_{M}$ in Eqn. (4586), which is often used to prescribe damping due to an external fluid.
Stiffness Damping Coefficient: Specifies the high frequency damping coefficient $τ_{K}$ in Eqn. (4586), which is often used to damp both shear and dilation waves.

For large deformations, adding the stiffness damping coefficient can destabilize the solution. For stability, you are advised to add the mass damping coefficient or use a Newmark parameter $γ$ (as defined in Eqn. (4603)) greater than 0.5.

Note

Setting both damping coefficients to zero is equivalent to running the simulation without the Rayleigh Damping model selected. The default values are rarely applicable. To damp high frequency transients that are introduced in dynamic problems, it is useful to apply a condition with no mass proportional damping, and a stiffness proportional damping equal to the time-step. This ensures quick damping of the transient modes with natural frequencies smaller than the time-step.