Proper Generalized Decomposition (PGD) is a mathematical technique that can be used to approximate the solution of partial differential equations (PDEs) by expanding it in a basis of simple functions. It’s a generalization of the Proper Orthogonal Decomposition (POD) method, which can be used when the solution of the PDE is not linear. PGD is a powerful technique that can be used to reduce the dimensionality of a system, by identifying the most important modes and can be used for non-linear problems and for problems with high-dimensional parametric space. It consists of expressing the solution in terms of a linear combination of simple functions (basis functions), which can be chosen depending on the problem under consideration, and determining the coefficients of this linear combination by projecting the PDE onto the chosen basis functions. PGD can be used to approximate the solution and to study the effect of different parameters and boundary conditions on the solution.

Introduction to Proper Generalized Decomposition

Proper Generalized Decomposition (PGD) is a mathematical technique used to approximate the solution of partial differential equations (PDEs). It is a generalization of the Proper Orthogonal Decomposition (POD) method, which can be used when the solution of the PDE is not linear.

The main idea behind PGD is to express the solution of the PDE in terms of a linear combination of simple functions (basis functions). These functions are chosen depending on the problem under consideration, e.g. trigonometric functions, polynomials, etc.

The next step is to determine the coefficients of the linear combination by projecting the PDE onto the chosen basis functions, this can be done by using Galerkin method. Once the coefficients are determined, the solution of the PDE can be approximated by the PGD expansion.

PGD can be used to reduce the dimensionality of a problem, by identifying the most important modes and can be used for non-linear problems and for problems with high-dimensional parametric space. It can be applied to a wide range of problems, such as fluid dynamics, heat transfer, structural analysis and many others.

The PGD method can be used to study the effect of different parameters and boundary conditions on the solution, and it can be used to analyze the system behavior and reduce the computational cost. However, it’s important to have a good understanding of the underlying mechanics of the problem and the assumptions made in the analysis.

PGD Analysis Procedure

he procedure for performing Proper Generalized Decomposition (PGD) analysis can be broken down into several steps:

1. Formulate the problem: The first step is to formulate the problem and write it in the form of a partial differential equation (PDE). The PDE should be defined on a domain and with appropriate initial and boundary conditions.
2. Choose basis functions: The next step is to choose a set of basis functions that are able to capture the behavior of the solution. These functions can be chosen depending on the problem under consideration, e.g. trigonometric functions, polynomials, etc.
3. Determine the PGD expansion: The solution of the PDE is expressed in terms of the chosen basis functions by using a linear combination of them. The coefficients of the basis functions are determined by projecting the PDE onto the chosen basis functions, this can be done by using Galerkin method.
4. Determine the PGD coefficients: To determine the coefficients of the PGD expansion, the PDE is projected onto the chosen basis functions. This step can be done using the Galerkin method, which consists of multiplying the PDE by the basis functions and integrating over the domain.
5. Approximate the solution: Once the coefficients of the PGD expansion are determined, the solution of the PDE can be approximated by the PGD expansion.
6. Study the effect of different parameters and boundary conditions: The PGD method can be used to study the effect of different parameters and boundary conditions on the solution. By changing the parameters and boundary conditions and repeating the analysis, it is possible to study the system behavior and reduce the computational cost.

It’s important to note that the accuracy of the PGD solution depends on the choice of basis functions and the number of terms in the expansion, as well as the quality of the data used. Also, the choice of the solver and the time step in the PDE solver will affect the accuracy of the PGD analysis as well.

PGD Available Softwares

There are several open-source software packages available that can be used to perform Proper Generalized Decomposition (PGD) analysis. Some of the more popular ones include:

1. PyPGD: PyPGD is a Python-based software package that can be used to perform PGD analysis on a wide range of problems. It includes a variety of features such as PGD mode visualization, modal analysis, and error analysis.
2. ROMtoolbox: ROMtoolbox is a MATLAB-based software package that can be used to perform PGD analysis on a wide range of problems. It includes a variety of features such as PGD mode visualization, modal analysis, and error analysis.
3. FEniCS-PGD: FEniCS-PGD is a Python-based software package that can be used to perform PGD analysis on heat transfer and fluid dynamics problems using the FEniCS library. It is open-source and it allows to handle non-linear problems and can be used with different mesh generators.
4. OpenFOAM: OpenFOAM is a widely-used open-source software package for computational fluid dynamics (CFD). It includes a PGD module that can be used to perform PGD analysis on fluid dynamics problems.
5. ROMlib: ROMlib is a C++ library that can be used to perform PGD analysis on a wide range of problems. It includes a variety of features such as PGD mode visualization, modal analysis, and error analysis.

These are just a few examples of the PGD software available. There are many other PGD software packages available, and the choice of which one to use will depend on the specific problem and the desired level of accuracy. It’s important to note that these software packages are usually focused on a specific field such as fluid dynamics, heat transfer, or combustion. They also may have different functionalities and interfaces, so it’s important to consider your needs and the specific problem you want to solve before choosing a software package.