Functions System

Overview

Functions are used to define functions depending only on time and spatial position: . These objects can serve a wide variety of purposes, including (but not limited to) the following:

• defining initial conditions,

• defining residual contributions (sources, boundary conditions, etc.), and

• defining post-processing quantities.

Moose Functions should override the following member functions:

• Real value(Real, Point) - the value of the function at a point in space and time

• Real value(ADReal, ADPoint) - the AD enabled version of the above function

• Real timeDerivative(Real, Point) - the derivative of the function with respect to the first argument (time)

• RealVectorValue gradient(Real, Point) - the spatial derivative with respect to the second argument

and may optionally override the following member functions, which is only needed for some particular functionality:

• Real timeIntegral(Real t1, Real t1, const Point & p), which computes the time integral of the function at the spatial point p between the time values t1 and t2.

For vector valued functions

• RealVectorValue vectorValue(Real, Point) - returning a vector value at a point in space and time

• RealVectorValue curl(Real, Point) - returning the curl of the function at a point in space and time

• Real div(Real, Point) - returning the divergence of the function at a point in space and time

can be overridden. The optional Real integral() and Real average() methods can also be overridden. Note that two overloads exist for the value() member function. This enables evaluation of functions with dual numbers. As most legacy function do not implement an AD overload of the value() function, the Function base class automatically provides one that uses the non-AD value(), timeDerivative(), and gradient() member functions to construct an AD result. Check out PiecewiseBilinear to see how to update a function to support AD by using a templated valueInternal() function with virtual value() forwarders.

Available Objects

• Moose App
• ADParsedFunctionFunction created by parsing a string
• ADPiecewiseLinearLinearly interpolates between pairs of x-y data
• Axisymmetric2D3DSolutionFunctionFunction for reading a 2D axisymmetric solution from file and mapping it to a 3D Cartesian model
• BicubicSplineFunctionDefine a bicubic spline function from interpolated data defined by input parameters.
• CoarsenedPiecewiseLinearPerform a point reduction of the tabulated data upon initialization, then evaluate using a linear interpolation.
• CompositeFunctionMultiplies an arbitrary set of functions together
• ConstantFunctionA function that returns a constant value as defined by an input parameter.
• ImageFunctionFunction with values sampled from an image or image stack.
• LinearCombinationFunctionReturns the linear combination of the functions
• ParsedFunctionFunction created by parsing a string
• ParsedGradFunctionDefines a function and its gradient using input file parameters.
• ParsedVectorFunctionReturns a vector function based on string descriptions for each component.
• PeriodicFunctionProvides a periodic function by repeating a user-supplied base function in time and/or any of the three Cartesian coordinate directions
• PiecewiseBilinearInterpolates values from a csv file
• PiecewiseConstantDefines data using a set of x-y data pairs
• PiecewiseConstantFromCSVUses data read from CSV to assign values
• PiecewiseLinearLinearly interpolates between pairs of x-y data
• PiecewiseLinearFromVectorPostprocessorProvides piecewise linear interpolation of from two columns of a VectorPostprocessor
• PiecewiseMulticonstantPiecewiseMulticonstant performs constant interpolation on 1D, 2D, 3D or 4D data. The data_file specifies the axes directions and the function values. If a point lies outside the data range, the appropriate end value is used.
• PiecewiseMultilinearPiecewiseMultilinear performs linear interpolation on 1D, 2D, 3D or 4D data. The data_file specifies the axes directions and the function values. If a point lies outside the data range, the appropriate end value is used.
• SolutionFunctionFunction for reading a solution from file.
• SplineFunctionDefine a spline function from interpolated data defined by input parameters.
• VectorPostprocessorFunctionProvides piecewise linear interpolation of from two columns of a VectorPostprocessor

Available Actions

• Moose App
• AddFunctionActionAdd a Function object to the simulation.