PDEModels Overview

This partial differential equation (PDE) model overview provides a starting point for setting up PDE models in various fields of physics. The PDE models presented here are based on a high-level PDE modeling language expressed through PDEComponent functions and boundary Conditions and Values. It is important to realize that in case your field of interest is not presented here, that does not mean that the Wolfram Language cannot solve that field's equations. It just only means that these differential equations need to be expressed in a more mathematical notation, detailed in the guide pages for Differential Operators, Differential Equations and Partial Differential Equations.

This tutorial, in contrast, focuses fields of physics which have a high-level representation in the Wolfram Language. The various fields presented here are becoming more complete with each version as we continue to expand upon them.

Typically, a field of physics that is considered complete consists of a guide page specific to that area and one or more monographs explaining the theory behind the functions provided. In some cases, verification notebooks are provided. A collection of models provides extended examples that showcase a specific application. The application models are typically more extensive than what one would normally find in the reference documentation. The example collection points to examples from the reference documentation that show a feature of particular interest.

The PDEs and boundary conditions guide page of a specific field of physics will link to a guide page that provides a listing of all available PDE functions and boundary conditions that are useful for creating PDE models in that area. A short description of the various PDE models can also be found on the guide page, and a more detailed overview of which model makes use of which functionality is provided last.

Introduction

The Boiling an Egg model is a good first application example to look at.

Acoustics

Acoustic PDEs and Boundary Conditions Guide

Acoustics in the Frequency Domain

Contents

Introduction

Time-Harmonic Analysis

Eigenfrequency Analysis

Helmholtz Equation

Introduction to Helmholtz Equation

Derivation of the Frequency Acoustics Model from the Time Domain Model

Model Parameter Setup

Source Types

Monopole Sources
Dipole Sources

Sound Propagation in Lossy Media

A Comparison of Time-Domain and Frequency-Domain Modeling

Wave Equation: Time-Domain Modeling
Helmholtz Equation: Frequency-Domain Modeling
Accuracy Comparison

Acoustic Boundary Conditions

Impedance Boundary Conditions

Formulation
Derivation
Impedance Boundary Conditions in Time-Harmonic Analysis

Absorbing Boundary Conditions

Formulation
Derivation
Absorbing Boundary Conditions in Time-Harmonic Analysis

Sound Hard Boundary Conditions—Walls

Formulation
Derivation
Sound Hard Boundary Conditions in Time-Harmonic Analysis
Sound Hard Boundary Conditions in Eigenfrequency Analysis

Normal Velocity Boundary Conditions

Formulation
Derivation
Normal Velocity Boundary Conditions in Time-Harmonic Analysis

Sound Soft Boundary Conditions

Formulation
Derivation
Sound Soft Boundary Conditions in Time-Harmonic Analysis
Sound Soft Boundary Conditions in Eigenfrequency Analysis

Pressure Source Boundary Conditions

Formulation
Derivation
Pressure Source Boundary Conditions in Time-Harmonic Analysis

Radiation Boundary Conditions

Formulation
Derivation
Radiation Boundary Conditions in Time-Harmonic Analysis

Floquet Periodic Boundary Conditions

Formulation
Derivation
Floquet Periodic Boundary Conditions in Time-Harmonic Analysis

Perfectly Matched Layer

Perfectly Matched Layer in Time-Harmonic Analysis

Nomenclature

References

Acoustics in the Time Domain

Contents

Introduction

Wave Equation

Introduction to the Wave Equation

Model Parameter Setup

Wave Types

Time-Harmonic Waves
Time-Inharmonic Waves

Source Types

Monopole Sources
Dipole Sources

The Wave Equation as a System of First-Order Equations

Sound Propagation in Lossy Media

Acoustic Boundary Conditions

Impedance Boundary Conditions

Formulation
Derivation

Absorbing Boundary Conditions

Formulation
Derivation

Sound Hard Boundary Conditions—Walls

Formulation
Derivation

Normal Velocity Boundary Conditions

Formulation
Derivation

Sound Soft Boundary Conditions

Formulation
Derivation

Pressure Source Boundary Conditions

Formulation
Derivation

Radiation Boundary Conditions

Formulation
Derivation

Periodic Boundary Conditions

Formulation
Derivation

Perfectly Matched Layer

Appendix

Perfectly Matched Layer Derivation

Attenuation Using an Artificial Complex Dimension
PML Coordinate Transformations on the Coupled First-Order Wave Equation

NeumannValues on Time Derivatives

Radiated Sound Waves with Oblique Incidence

Nomenclature

References

Acoustics Models

Acoustic Cloak

Acoustic Horn

Acoustic Mirror

Acoustic Muffler

Acoustic Wave Diffraction

Electric Motor Noise Analysis

Helmholtz Resonator

Room Eigenfrequencies

Acoustics Examples

Acoustic Eigenmodes in a Car

Electromagnetics

Electromagnetic PDEs and Boundary Conditions Guide

Electromagnetics Overview

Introduction

Maxwell's Equations

Constitutive Relations

Linear Constitutive Relations

Constitutive Relations Summary

Types of Electromagnetics Modeling

Dependent Variables

Electromagnetics Decision Diagram

Statics

Electric field
Magnetic field

Transient

Frequency regime
Low-frequency regime—Quasistatic
High-frequency regime—Electromagnetic waves

Skin Depth

Frequency versus Time Domain

Phasors

Nomenclature

References

Electrostatics

Introduction

Overview Example

Geometry

Material Parameters

Units

Boundary Conditions

Mesh Generation

Electrostatic Analysis

Post-processing

Electrostatic Equation

Model setup

Electrostatics

Dielectric materials and the constitutive equation
Linear dielectric materials
Multiple materials
Anisotropic dielectric materials
Nonlinear dielectric materials
Axisymmetric models
Source types

Secondary Quantities

Electrostatic Energy

Capacitance

Energy method

Electrostatic Force

Coulomb force
Maxwell stress tensor
Forces on a dielectric

Boundary Conditions in Electrostatics

Electric Potential Boundary Condition

Electric Flux Density Boundary Condition

Symmetry Boundary Condition

Periodic Boundary Condition

Nomenclature

References

Electric Currents

Introduction

Overview Example

Geometry

Material Parameters

Units

Boundary Conditions

Mesh Generation

Stationary Current Analysis

Post-processing

Time-Dependent Analysis

Frequency Response Analysis

Conduction and displacement currents
From frequency domain solution to time domain solution

Parametric Analysis

Equations

From Maxwell's Equations to the Current Continuity Equation

Ohm's Law

Stationary Currents or Direct Currents

Dynamic Currents

General time-dependent currents
Alternating currents (AC)

Electric Currents Model Setup

Static electric currents model setup
Dynamic electric currents model setup
2D models
1D models

Axisymmetric Electric Currents Models

2D axisymmetric
1D axisymmetric

Anisotropic Materials

Multiple Materials

Source Types

Volume current source
Point current source
Line current source

Secondary Quantities

Resistance and Impedance

Electric Power and Resistive Loss

Boundary Conditions in Electric Currents

Electric Potential Boundary Condition

Current Density Boundary Condition

Symmetry Boundary Condition

Periodic Boundary Condition

Material Interface Conditions

Nomenclature

References

Magnetostatics for Permanent Magnets

Introduction

Overview Example

Geometry

Mesh Generation

Material Parameters

Units

Boundary Conditions

Magnetostatic Analysis

Post-processing

Equations

Overview

From Maxwell's Equations to the Scalar Potential Magnetostatic Equation

Magnetic Materials

Scalar potential formulation
Linear magnetic materials
Anisotropic materials
Classification of Magnetic Materials

Model Setup

2D models
2D axisymmetric

Modeling Magnetic Materials

Soft magnetic materials
Hard ferromagnetic materials: Permanent magnets

Modeling Anisotropic Materials

Multiple Materials

Secondary Quantities

Fields

Energy

Magnetostatic Forces

Maxwell stress tensor

Convergence of Magnetostatics Models

Boundary Conditions

Magnetic Potential Boundary Condition

MagneticPotentialCondition example

Magnetic Flux Density Boundary Condition

MagneticFluxDensityValue example

Symmetry Boundary Condition

MagneticSymmetryValue example

Antisymmetry Boundary Condition

Antisymmetry boundary condition example

Periodic Boundary Condition

Conditions at Material Interfaces

Nomenclature

References

Quasistatic Magnetic Fields

Introduction

Overview Example

Geometry

Material Parameters

Units

Mesh Generation

Boundary Conditions

Magnetostatic Analysis

Post-processing

Frequency Response Analysis

Parametric Analysis

Time-Dependent Analysis

Equations

Maxwell–Ampere's law
Magnetic and electric potentials
Constitutive equations—Material models
Quasistatic formulation equation

Maxwell–Ampere's Law

Quasistatic approximation

Magnetic and Electric Potentials

On the uniqueness of the solutions
Gauge transformation for
Coulomb's gauge for A

Constitutive Equations

Ohm's law
Linear magnetic materials
Anisotropic materials

Classification of Magnetic Materials

Quasistatic formulation Equation

Quasistatic time-dependent equation setup

Quasistatic Harmonic formulation

Frequency-dependent equation setup

Steady-State formulation

Magnetostatic equation setup

2D Out-of-Plane Models

2D out-of-plane models example

2D Out-of-Plane Axisymmetric Models

3D Models

3D model example
Special case: Magnetostatics in free space

Modeling Magnetic Materials

Soft magnetic materials
Hard ferromagnetic materials: Permanent magnets

Modeling Anisotropic Materials

Modeling Multiple Materials

Secondary Quantities

Fields

Energy

Inductance

Magnetostatic Forces

Lorentz force
Maxwell stress tensor
Example: Force between a current-carrying wire and a magnetic cylinder

Convergence of Magnetic Models

Boundary Conditions

Magnetic Vector Potential Condition

2D out-of-plane
2D axisymmetric out-of-plane
3D
Magnetic flux
Magnetic insulation boundary condition
Magnetic symmetry condition
MagneticPotentialCondition example

Conditions at Material Interfaces

Edge/Vector Elements

Nomenclature

References

Electromagnetics Models

Joule Heating

Electrostatically Actuated MEMS

Inductive Heating

Single Aperture Scalar Diffraction

Schrödinger-Poisson Quantum Well

Multiple Aperture Vector Diffraction

Spherical Capacitor

Electromagnetics Examples

Shielded Micro Strip

Motor

Fluid Dynamics

Fluid Dynamics PDEs and Boundary Conditions Guide

Laminar Flow

Contents

Introduction

Overview Example and Analysis Types

Stationary Analysis

Post-processing

Common visualization techniques

Parametric Analysis

Time-Dependent Analysis

Equations

Newtonian versus non-Newtonian Flow

Power Law

Power law example

Carreau

Cross

Bingham–Papanastasiou

Herschel–Bulkley–Papanastasiou

Custom Apparent Viscosity Model

Custom Viscous Stress Tensor

Computing viscosity and stress

Viscoelastic Flow

Energy Transport—Nonisothermal Flow

Boussinesq Approximation

Rayleigh–Bénard Convection

Flow Boundary Conditions

Inflow Conditions

Outflow Conditions

Wall Conditions

No-slip
No-slip example
Slip

Traction

Traction example

Initial Conditions

Convergence of Fluid Flow Models

Initial Seeding

Iterative stepping

Equation Modification

Stokes equation

Fluid Dynamics Model Verification Tests

Fluid Dynamics Models

Buoyancy-Driven Flow

Cerebral Aneurysm

Heat Exchanger

Passive Dew Condenser

Thermal Decomposition

Fluid Dynamics Examples

Stokes Flow

Navier-Stokes Equation

Time dependent Navier-Stokes Equation

Fluid Dynamics with Heat Transfer

Taylor-Couette Flow

Heat Transfer

Heat Transfer PDEs and Boundary Conditions Guide

Heat Transfer

Contents

Introduction

Heat Equation

Introduction to Heat Equation

Heat Equation Derivation

Heat Transfer Model Setup

Model Parameter Setup

Basic Heat Transfer Example

Source Types

Volumetric Heat Source
Point Heat Source
Layer Heat Source

Anisotropic and Orthotropic Heat Transfer

Nonlinear Heat Transfer

Temperature-Dependent Heat Capacity

Heat Transfer with Events

Heat Transfer in Porous Media

Heat Transfer Model with Mixed Dimensions

Heat Transfer in Multi-material Media

Heat Transfer with Phase Change

Ice-to-Water Solidification
Freezing of Liquid in a Pipe

Heat Transfer with Model Order Reduction

Multiphysics Heat Transfer

Boundary Conditions in Heat Transfer

Surface Temperature Boundary Condition

Purpose
Formulation
Derivation

Heat Flux Boundary Condition

Purpose
Formulation
Derivation

Thermally Insulated Boundary Condition

Purpose
Formulation
Derivation

Symmetry Boundary Condition

Purpose
Formulation
Derivation

Outflow Boundary Condition

Purpose
Formulation
Derivation

Convective Boundary Condition

Purpose
Formulation
Derivation

Thermal Radiation Boundary Condition

Purpose
Formulation
Derivation

Periodic Boundary Condition

Purpose
Formulation
Derivation

Appendix

Special Cases of the Heat Equation

Stationary Case
Heat Equation in Cylindrical Coordinates
Heat Equation in Spherical Coordinates

The Smoothing Characteristic of the Diffusion Equation

Modeling Heat Sources Using Element Markers

Conservation Laws with Discontinuous PDE coefficients

Possible Issues and Workarounds for Modeling Heat Pulses

Method 1—Reduce MaxStepFraction
Method 2—Using WhenEvent

Nomenclature

References

Heat Transfer Model Verification Tests

Heat Transfer Models

Anemometer

Buoyancy Driven Flow

Disc Brake

Egg Boiling

Heat Exchanger

Hygroscopic Swelling

Inductive Heating

Joule Heating

Laser Welding

Multilayer Sphere

Passive Dew Condenser

Room Heating

Shrink Fitting

Thermal Contact

Thermal Decomposition

Thermal Load

Tubular Reactor

Heat Transfer Examples

Heat Transfer with Events - Thermostat

Heat Transfer with Fluid Dynamics - Energy Transport

Heat Transfer with Model Order Reduction - Fast Time Integration

Nonlinear Heat Transfer Verification Test 1

Nonlinear Heat Transfer Verification Test 2

Mass Transport

Mass Transport PDEs and Boundary Conditions Guide

Mass Transport

Contents

Introduction

Mass Balance Equation

Mass Balance Equation Introduction

Mass Balance Equation Derivation

Mass Transport Model Setup

Initial Mass Transport Example

Mass Transport with a Chemical Reaction

Anisotropic and Orthotropic Mass Diffusion

Variable Mass Diffusion Coefficient

Temperature dependence of the diffusion coefficient
Concentration dependence of the diffusion coefficient

Interphase Mass Transfer

Mass Source Types

Multiphysics Mass Transport

Boundary Conditions in Mass Transport

Neumann Values for Conservative and Non-conservative Models

Model Parameter Setup

Concentration Boundary Condition

Purpose
Formulation
Derivation
Example
Visualization

Outflow Boundary Condition

Purpose
Formulation
Derivation
Example
Visualization of an Outflow Boundary Condition

Mass Flux Boundary Condition

Purpose
Formulation
Derivation
Example
Visualization of a Mass Flux Boundary Condition

Impermeable Boundary Condition

Purpose
Formulation
Derivation
Example
Visualization of an Impermeable Boundary Condition

Surrounding Flux Boundary Condition

Purpose
Formulation
Derivation
Example
Visualization of a surrounding flux boundary condition

Symmetry Boundary Condition

Purpose
Formulation
Derivation
Example

Periodic Boundary Condition

Purpose
Formulation
Derivation
Example
Visualization of a periodic boundary condition

Appendix

Special Cases of the Mass Balance Equation

Stationary case
Mass transport by diffusion only
Mass transport by convection only
Mass balance equation in cylindrical coordinates
Mass balance in spherical coordinates

Nomenclature

References

Mass Transport Models

Catalyst Deactivation

Catalytic Converter

Gas Absorption

Hygroscopic Swelling

Thermal Decomposition

Tubular Reactor

Mass Transport Examples

Boundary Conditions at Infinity

Cyclic Voltammetry

Fokker-Planck equation

Lamm equation

Reaction diffusion equation

Smoluchowski diffusion equation

Species diffusion under a dam

Solute centrifugation

Multiphysics

Multiphysics Models

Electromagnetics - Heat Transfer

Joule Heating

Inductive Heating

Electromagnetics - Structural Mechanics

Electrostatically Actuated MEMS

Electromagnetics - Quantum Physics

Schrödinger-Poisson Quantum Well

Fluid Dynamics - Heat Transfer

Buoyancy-Driven Flow

Heat Exchanger

Passive Dew Condenser

Thermal Decomposition

Fluid Dynamics - Mass Transport

Thermal Decomposition

Fluid Dynamics - System Physics

Cooling a Room with HVAC

Heat Transfer - Electromagnetics

Joule Heating

Inductive Heating

Heat Transfer - Fluid Dynamics

Buoyancy-Driven Flow

Heat Exchanger

Passive Dew Condenser

Thermal Decomposition

Buoyancy Driven Flow

Heat Transfer - Mass Transport

Hygroscopic Swelling

Thermal Decomposition

Tubular Reactor

Heat Transfer - Structural Mechanics

Disc Brake

Hygroscopic Swelling

Thermal Load

Heat Transfer - System Physics

Room Heating

Mass Transport - Fluid Dynamics

Thermal Decomposition

Mass Transport - Heat Transfer

Hygroscopic Swelling

Thermal Decomposition

Tubular Reactor

Mass Transport - Structural Mechanics

Hygroscopic Swelling

Quantum Physics - Electromagnetics

Schrödinger-Poisson Quantum Well

System Physics - Fluid Dynamics

Cooling a Room with HVAC

System Physics - Heat Transfer

Room Heating

Structural Mechanics - Electromagnetics

Electrostatically Actuated MEMS

Structural Mechanics - Heat Transfer

Disc Brake

Hygroscopic Swelling

Thermal Load

Structural Mechanics - Mass Transport

Hygroscopic Swelling

Structural Mechanics - System Physics

Beam Spring-Mass

Physics

Physics Models

Axisymmetric Conical Quantum Dot

Multiple Aperture Vector Diffraction

Schrödinger-Newton Gravitation

Schrödinger-Poisson Quantum Well

Single Aperture Scalar Diffraction

Quantum Ring

Physics Examples

Avoided Crossing

Eigenfunction clustering

System Physics

System Physics Models

Beam Spring-Mass

Cooling a Room with HVAC

Room Heating

Solid Mechanics

Solid Mechanics PDEs and Boundary Conditions Guide

Solid Mechanics

Contents

Introduction

Overview Example and Analysis Types

Geometry

Material Parameters

Units

Boundary Conditions

Mesh Generation

Stationary Analysis

Post-processing

Deformations
Strains
Stresses
Safety factor
Reaction forces

Time-Dependent Analysis

Eigenmode Analysis

Parametric Analysis

Force displacement plot
Parametric material laws

Frequency Response Analysis

Equations

Overview

Equilibrium equations
Kinematic equations
Constitutive equations

Equilibrium Equations

Body load

Kinematic Equations

Displacement versus deformation
Strain
Poisson's ratio

Constitutive Equations

Stress
Stress-strain relation
True stress and strain

Linear Elastic Material Models

Isotropic linear elastic materials
Orthotropic linear elastic materials
Transversely isotropic linear elastic materials
Anisotropic linear elastic materials
Non-axes-aligned material
Linear elastic materials
Generalization of the linear elastic constitutive equation
Initial strains
Thermoelasticity
Initial stresses
Plane strain, plane stress and axisymmetric models
Plane strain
Extended plane strain
Plane stress
Extended plane stress
Axisymmetric models
Limits of linear elasticity
The equation form of SolidMechanicsPDEComponent

Solid Mechanics in a Nutshell

Nonlinear Elastic Material Models—Hypoelastic Models

Hyperelasticity

Failure Theory

Multiple Materials

Damping

Rayleigh damping

Solid Mechanics Boundary Conditions

Displacement Constraints

Prescribed displacement
Roller constraints
Number of constraints needed

Boundary Load

Boundary load: Compression
Boundary load: Tension
Boundary load: Shear
Boundary load: Torsion
Boundary load: Bending
Boundary load: Spring
Boundary load: Damper

Symmetry Conditions

Appendix

Model Parameters

Boundary Condition Predicates

Stress Singularities

Verification

Large-Scale Finite Element Models

Nomenclature

References

Hyperelasticity

Contents

Introduction

St. Venant–Kirchhoff Model

Adding a New Material Model

Neo-Hookean Model

Strain and Stress Invariants

Compressibility

Hyperelastic Model Collection

Mooney–Rivlin Models

The incompressible Mooney–Rivlin model
The nearly incompressible Mooney–Rivlin model

Yeoh Model

The incompressible Yeoh model
The nearly incompressible Yeoh model

Neo-Hookean Model

The incompressible neo-Hookean model
Nearly incompressible neo-Hookean model

Arruda-Boyce Model

The incompressible Arruda–Boyce model
The nearly incompressible Arruda–Boyce model

Gent Model

The incompressible Gent model
The nearly incompressible Gent model

Plane Strain and Plane Stress Models

Plane strain
Plane stress
Plane strain and plane stress comparison

Hyperelastic Model Calibration

Uniaxial Test Data Fitting

Multiplicative Decomposition

Multiphysics Coupling

Thermoelasticity

Coupling approaches
Sequential coupling approach
Fully coupled approach
Total strain
Inelastic strain
Elastic strain
Isochoric and volumetric strain split
Stress

Multiple Material Constitutive Models

Transversely Isotropic Hyperelastic Materials

Standard Reinforcing Material Model

Fiber-Reinforced Materials

Curved Fibers

Inextensible Fibers

Materials with Two Families of Fibers

References

Plasticity

Introduction

An introductory example

Theory of Small Strain Plasticity

Yield function

von Mises yield criterion
Tresca yield criterion
Mohr-Coulomb yield criterion
Drucker-Prager yield criterion

Flow rule

Isotropic plasticity
Small strain plastic flow

Hardening

Isotropic hardening

Perfect plasticity
Linear isotropic hardening
Linear isotropic hardening example

Load history

Permanent deformation

Load history

References

Solid Mechanics Model Verification Tests

Solid Mechanics Models

3D Printed Mechanical Design

Biaxial Tensile Test of Hyperelastic Tissue

Biomechanics of the Human Tendon

Disc Brake

Electrostatically Actuated MEMS

Hygroscopic Swelling

Hyperelastic Model Comparison

Slope Stability

Spine Surgery Rod

Thermal Load

Vascular Vessel

Solid Mechanics Examples

Plane Stress

Plane Stress Eigenmodes

Plane Strain

Rayleigh damping

3D Stress

The Finite Element Method

The finite element method is a solution method for partial differential equations and the main method to solve the PDE models presented here. More information on the finite element method is found in the following guide and overview pages.

Finite Element Method Guide

Finite Element Method Overview

NDSolve options for Finite Elements