File shiftedmetricinterp.hxx

class ShiftedMetricInterp : public ParallelTransform

#include <shiftedmetricinterp.hxx>

Shifted metric method Each Y location is shifted in Z with respect to its neighbours so that the grid is orthogonal in X-Z, but requires interpolation to calculate the values of points along field-lines.

In this implementation the interpolation is done using ZInterpolation objects

Public Functions

ShiftedMetricInterp() = delete

ShiftedMetricInterp(Mesh &mesh, CELL_LOC location_in, Field2D zShift_in, BoutReal zlength_in, Options *opt = nullptr)

virtual void calcParallelSlices(Field3D &f) override

Calculates the yup() and ydown() fields of f by interpolating f through a toroidal shift angle

Calculate the Y up and down fields

virtual Field3D toFieldAligned(const Field3D &f, const std::string &region = "RGN_ALL") override

Uses interpolation of f through a toroidal shift angle to align the grid points with the y coordinate (along magnetic field usually).

Note that the returned field will no longer be orthogonal in X-Z, and the metric tensor will need to be changed if X derivatives are used.

Shift the field so that X-Z is not orthogonal, and Y is then field aligned.

inline virtual FieldPerp toFieldAligned(const FieldPerp &f, const std::string &region = "RGN_ALL") override

virtual Field3D fromFieldAligned(const Field3D &f, const std::string &region = "RGN_ALL") override

Converts a field back to X-Z orthogonal coordinates from field aligned coordinates.

Shift back, so that X-Z is orthogonal, but Y is not field aligned.

inline virtual FieldPerp fromFieldAligned(const FieldPerp &f, const std::string &region = "RGN_ALL") override

inline virtual bool canToFromFieldAligned() const override

inline virtual std::vector<ParallelTransform::PositionsAndWeights> getWeightsForYApproximation(int i, int j, int k, int y_offset) override

inline virtual bool requiresTwistShift(bool twist_shift_enabled, YDirectionType ytype) override

If twist_shift_enabled is true, does a Field3D with Y direction ytype require a twist-shift at branch cuts on closed field lines?

Protected Functions

virtual void checkInputGrid() override

This method should be called in the constructor to check that if the grid has a ‘parallel_transform’ variable, it has the correct value

Private Members

CELL_LOC location = {CELL_CENTRE}

Field2D zShift

This is the shift in toroidal angle (z) which takes a point from X-Z orthogonal to field-aligned along Y.

BoutReal zlength = {0.}

Length of the z-domain in radians.

std::vector<std::unique_ptr<ZInterpolation>> parallel_slice_interpolators

Cache of interpolators for the parallel slices. Slices are stored in the following order: {+1, …, +n, -1, …, -n} parallel_slice_interpolator[i] stores interpolator for slice i+1 parallel_slice_interpolator[n + i] stores offset -(i+1) where i goes from 0 to (n-1), with n the number of y guard cells

std::unique_ptr<ZInterpolation> interp_to_aligned

ZInterpolation objects for shifting to and from field-aligned coordinates.

std::unique_ptr<ZInterpolation> interp_from_aligned

const std::size_t ydown_index

Private Static Attributes

static constexpr std::size_t yup_index = 0