Langley Research Center Turbulence Modeling Resource

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TURBULENCE MODEL NUMERICAL ANALYSIS

Grids - 3D Hemisphere Cylinder

The methodology to create a series of grids is provided. Both structured and unstructured grids are provided (unlike most others on the Turbulence Modeling Resource website, they are completely independent of one another). The coordinate system is defined with x streamwise, y horizontal, and z vertical.

STRUCTURED VERSIONS OF GRIDS

For the structured grids, each grid is a PLOT3D unformatted file of size ni x nj x nk, where ni is the number of points along the body, nj is the number of points in the normal direction, and nk is the number of points in the circumferential direction. The grids range from 161 x 289 x 129 (finest half-plane grid) to 6 x 10 x 5 (coarsest half-plane grid). The constructed grids are not necessarily nested grids but coarser grids can be constructed by extracting every-other-point in all directions (i.e., regular refinement). The farfield boundaries are located approximately 20 unit lengths from the body.

The figure below shows a view of the level 4 structured half-plane grid of size ni=21 x nj=37 x nk=17 in the streamwise x normal x circumferential directions.

Note: be sure to use double precision when reading (or writing) the grids!

PLOT3D Files

A FORTRAN program for structured grids is provided that can be used to generate the structured grids in PLOT3D format. All information has been hardwired into the program except three integer inputs.

The first input is integer, between 1 and 6 indicating the level of the grid to be generated (finest to coarsest).

The second input is integer, between 0 and 2 and indicates the type of grid to be generated (0 is inviscid, 1 is laminar, and 2 is turbulent). Use "2".

The third input is integer, between 1 and 2 and indicates the type of grid to be generated (1 is 2D, 2 is 3D with symmetry in y, 3 (which does not work correctly) is 3D without symmetry in y). Use "2" to create a 3-D half-plane grid like that shown in the first figure above.

The half-plane grid sizes are as follows:

• 161 x 289 x 129... 5,898,240 cells (or 11,796,480 cells in the equivalent 360 degree grid)
• 81 x 145 x 65... 737,280 cells (or 1,474,560 cells in the equivalent 360 degree grid)
• 41 x 73 x 33... 92,160 cells (or 184,320 cells in the equivalent 360 degree grid)
• 21 x 37 x 17... 11,520 cells (or 23,040 cells in the equivalent 360 degree grid)
• 11 x 19 x 9... 1,440 cells (or 2,880 cells in the equivalent 360 degree grid)
• 6 x 10 x 5... 180 cells (or 360 cells in the equivalent 360 degree grid)

Neutral Map Files associated with each grid are also generated by the above program (these files specify grid indices associated with each boundary condition - see The Neutral Map File). The following is an example neutral map file:

• Neutral Map File for (3-D with symmetry) 21 x 37 x 17

 

UNSTRUCTURED VERSIONS OF GRIDS

The unstructured grids are created independently of the structured grids. In these grids, the farfield boundaries are located approximately 10 unilt lengths from the body. A picture of the unstructured mixed-element prisms/hexes grid is shown in the figure below.

UGRID Files

A FORTRAN program for unstructured grids (modified on 10/07/2015, only a minor bug compared to V24 from 10/02) is provided that can be used to generate unstructured grids in UGRID format. All information has been hardwired into the program except 8 inputs. The input values to generate the finest mixed prisms/hexes grid are given in hemisphere_cylinder_finest.inp. Below is a description of input parameters with the finest-grid value in parenthesis:

• 1. Positive double, target Reynolds number: (3.5E5)
• 2. Positive double, target y_plus: (0.5)
• 3. Integer, 1,2,3, or 4, grid type: 1 - prisms, 2 - tetrahedral, 3- mixed, prisms/tets, 4 - mixed, prism/hexes (4)
• 4. Logical, output format: T -.b8.ugrid format, F - ASCII format (T)
• 5. Positive double, distance to the outer boundary: (10.0)
• 6. Integer, number of nodes along the cylinder: (800)
• 7. Positive double, length of the hemisphere-cylinder: (10.0)
• 8. Integer, division of the generating sector: (160)

Return to: Numerical Analysis of 3D Hemisphere Cylinder Validation Case Intro Page

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Recent significant updates:
01/27/2017 - removed link to coarser versions of UGRID files

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Last Updated: 05/13/2019