7. Grid file¶
If you are using the GUI, grid file is written when the ‘Write Grid’ button is pressed.
7.1. Scalar parameters¶
Grid size and topology¶
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Number of radial grid points in the global grid, including boundary cells. |
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Number of poloidal grid points in the global grid, not including boundary cells. |
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Number of poloidal boundary cells included in the grid at each divertor target. |
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Radial grid indices of the separatrices. These give the index of the first
grid point radially outside the separatrix. A single null grid has
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Poloidal grid indices of the X-points. These give the index of the last
grid point poloidally before the poloidal position of the X-point is
reached. For single null grids |
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For double null grids, gives the number of poloidal grid points before the upper target is reached, not including boundary cells. |
Equilibrium parameters¶
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Other options¶
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7.2. 1D arrays¶
Poloidal coordinates¶
BoutMesh writes three poloidal coordinates to the grid file:
Note
These coordinates are defined/created in BoutMesh because they require a global mesh, which is not required in Mesh where everything is defined only in terms of MeshRegions.
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Increments by |
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Increments by |
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Is a straight-field line poloidal coordinate proportional to the toroidal angle (i.e. to zShift). It goes from 0 to 2pi in the core, and is undefined on open field lines. |
1D integral quantities¶
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The total poloidal distance around a closed flux surface in the core. Not calculated on open flux surfaces. |
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The total toroidal angular displacement when following a field line one full poloidal turn around a closed flux surface. Not calculated on open flux surfaces. |
Wall location¶
If a wall is defined in the equilibrium then the coordinates of the closed wall is saved:
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Major radius locations [in meters] of points on the wall. This array forms a closed loop so the last element is the same as the first. |
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Height locations [in meters] of points on the wall, the same
number of points as |
7.3. 2D arrays¶
All 2D arrays are saved at the cell centre position, named with no suffix, e.g.
Rxy
. For use with staggered grid codes, they are also saved at the ‘lower’
cell face locations, with suffix _xlow
, e.g. Rxy_xlow
for the
\(x\)-direction cell faces and with suffix _ylow
, e.g. Rxy_ylow
,
for the \(y\)-direction cell faces.
Spatial positions¶
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Major radius. |
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Height. |
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Major radius and height of the lower-left corner of each grid cell. Not needed by BOUT++, but may be useful for post-processing. |
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Major radius and height of the other three corners of each grid cell.
Mostly redundant information with |
Grid spacings¶
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Coordinate spacing in the radial \(x\) direction. |
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Coordinate spacing in the poloidal \(y\) direction. |
Magnetic field quantities¶
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Poloidal magnetic flux function, which is the poloidal magnetic flux divided by \(2\pi\). |
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Components of the magnetic field in the major-radial and vertical directions. |
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Components of the magnetic field in the poloidal and toroidal directions. |
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Total magnetic field. |
Boundary quantities¶
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A 2D mask indicating whether a cell is inside or outside the wall. It’s value is 1 for cells entirely outside the wall; 0 for cells entirely inside the wall. Cells that cross the wall are given a penalty proportional to the fraction of the cell poloidal length that is inside the wall. |
Integral quantities¶
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Poloidal distance (in metres) from the lower divertor target of each flux surface to the grid point (on open field lines), or from the poloidal location of the lower X-point (on closed field lines). |
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Toroidal displacement of a field line followed from some reference position to the poloidal location of the grid point. |
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\(d^2\zeta/dxdy\), where \(zeta\) is the toroidal angle. Only
used in BOUT++ for the |
Metric coefficients¶
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Contravariant components of the metric tensor. Note |
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Covariant components of the metric tensor. Note |
Jacobian¶
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The Jacobian of the locally field aligned BOUT++ coordinate system. |
Curvature¶
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Contravariant components (despite the slightly misleading variable names) of \(\nabla\times(\mathbf{b}/B)\), i.e. \(\nabla\times(\mathbf{b}/B)^x\), \(\nabla\times(\mathbf{b}/B)^y\), and \(\nabla\times(\mathbf{b}/B)^z\). |
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Contravariant components of the vector
\(\frac{B}{2}\nabla\times\left(\frac{\mathbf{b}}{B}\right)\). Other
forms (e.g. \(\mathbf{b}\times\mathbf{\kappa}\)) could be
implemented, for different settings of |
Equilibrium plama parameters¶
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Pressure profile read from the geqdsk input file (if there was one). |
7.4. Provenance tracking¶
See Provenance tracking.