AFLR3 Tutorial – BL Cases
The following tutorial example cases demonstrate various capabilities within AFLR3 for controlling the point spacing within both the BL and isotropic grid regions. SolidMesh is used in the following sections to run the cases. A basic proficiency with SolidMesh is assumed. The data files for these cases are minim.SM.gz and minim2.SM.gz (right click to save/download each file). Alternatively, each of these cases can be run from a terminal window using the aflr3 script command. The surface grid files for these cases are minim2_BL.surf.gz and minim_BL.surf.gz.
The minim and minim2 cases are two versions of a missile like configuration. The missile itself has three zero thickness fins (that are off by default in the minim2 case) and an internal nozzle and motor exit. In the minim case there is a large far-field, near-field embedded surface to control near-body spacing, and an embedded surface to control plume spacing. The minim case is shown below with the far-field and without the far-field.
In the minim2 case the far-field is very close and the plume is treated as a solid surface. The minim2 case is shown below.
1. BL GRID - NORMAL SPACING DISTRIBUTION CONTROL (AUTO MODE)
1.1. Default BL grid
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 -blcheck -w
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 –w
- Terminal Window
o run SolidMesh for case minim2
sm –case minim2.SM.gz
- SGen Panel
o generate surface grid
- VGen Panel
o generate volume grid
- Terminal Window
o display BL parameters
./minim2.script -blcheck
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
1.2. Limit maximum BL growth rate
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 -blrm 1.3 –w
- SGen Panel
o generate surface grid
- VGen Panel
o set maximum BL growth rate to 1.3
o generate volume grid
o set maximum BL growth rate to 2 (reset to default value)
o enter return in y+, Re, or Ref Length field to update BL growth rate display
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
1.3. Increase BL thickness to increase extent of BL region
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 -bldel 5 –w
- SGen Panel
o generate surface grid
- VGen Panel
o select specify BL thickness toggle
o set BL thickness to 5
o generate volume grid
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
1.4. Decrease BL thickness to decrease extent of BL region
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 -bldel 0.5 –w
- SGen Panel
o generate surface grid
- VGen Panel
o set BL thickness to 0.5 to decrease transition
o generate volume grid
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
1.5. Increase initial y+ normal spacing
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 2 –w
- SGen Panel
o generate surface grid
- VGen Panel
o set maximum BL growth rate to 3 (to allow it to be reset in the next step)
o set y+ to 2 (enter return in the field to set)
o generate volume grid
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
1.6. Increase initial y+ normal spacing and limit maximum BL growth rate
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 2 -blrm 1.5 –w
- SGen Panel
o generate surface grid
- VGen Panel
o set maximum BL growth rate to 1.5
o generate volume grid
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
2. BL GRID - NORMAL SPACING DISTRIBUTION CONTROL (MANUAL MODE)
2.1. Manual mode BL parameters equivalent to default auto mode
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 -blrm 1.5 -blr 1 –bli 5 –w
- Terminal Window
o run SolidMesh for case minim2
sm –case minim2.SM.gz
- SGen Panel
o generate surface grid
- VGen Panel
o select manual BL growth rates toggle
o set maximum BL growth rate to 1.5
o set initial BL growth rate to 1
o set number of constant layers to 5
o generate volume grid
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
2.2. Increase BL thickness to increase extent of BL region
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 -blrm 1.5 -blr 1 –bli 5 -bldel 5 –w
- SGen Panel
o generate surface grid
- VGen Panel
o select specify BL thickness toggle
o set BL thickness to 5
o generate volume grid
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
2.3. Increase BL thickness to increase extent of BL region and also increase maximum allowable BL growth rate
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 -blrm 2 -blr 1 –bli 5 -bldel 5 –w
- SGen Panel
o generate surface grid
- VGen Panel
o set maximum BL growth rate to 2
o generate volume grid
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
3. BL GRID - ISOTROPIC SPACING CONTROL (element size factor)
3.1. Increase BL thickness to increase extent of BL region
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 -bldel 8 –w
- Terminal Window
o run SolidMesh for case minim2
sm –case minim2.SM.gz
- SGen Panel
o generate surface grid
- VGen Panel
o set BL thickness to 8 to increase transition distance
o generate volume grid
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
3.2. Decrease BL interface element size multiplier to decrease isotropic point spacing at edge of BL
Alternative Terminal Window AFLR3 Script Command
aflr3 minim2_BL.surf.gz -bl -blc refx=100 -y+ 1 -bldel 8 cdf2=0.9 –w
- SGen Panel
o generate surface grid
- VOpt Panel
o scroll to parameter named cdf2
o set cdf2 to 0.9 (enter return in field to set)
- VGen Panel
o generate volume grid
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
4. BL GRID - EMBEDDED/TRANSPARENT SURFACES
4.1. Example case that includes embedded/transparent surfaces for isotropic spacing control and embedded/transparent surfaces with attached BL regions
Alternative Terminal Window AFLR3 Script Command
aflr3 minim_BL.surf.gz -bl -blc refx=100 -y+ 1 –w
- Terminal Window
o run SolidMesh for case minim2
sm –case minim.SM.gz
- SGen Panel
o generate surface grid
o note that fins and plume surface groups must have a surface grid BC for split corners set to force
- VGen Panel
o generate volume grid
- SGen Panel
o de-activate surface groups for near-field and plume (avoid current graphics issue when volume grid is displayed later)
o generate surface grid (avoid current graphics issue when volume grid is displayed later)
- Viz Panel
o read-in volume grid
o generate X-Y cutting plane
.
- Viz Panel
o generate X-Z cutting plane at Y=70
