Surface Area Convergence Data

About

The surface area calculations have come under scrutiny when examining the burn rate, and the lack of convergance therein. The point of this page, and the data presented within is to first determine whether the surface area calculations do converge over a set of reasonable resolutions. If not, it will hopefully provide insight into a solution.
The current setup is to test several different geometries including: cylinders, holes, cubic shapes, triangular shapes. Results can be seen below.

Surface Area Plots

Hole Case

This run contains 16 holes in a block of PBX with radii 16mm and 32mm (for different cases). The Burn Rate was set to 0 within Steady_Burn.cc for this simulation in order to test only surface area.The gas surrounding the cylinders was set to a temperature of 600K in order to set off the Burning Cells flag within Steady Burn. The results of this run are as follows:

1.6 cm radii, 12.8x12.8 cm domain, 4x4 array

Plot of Error vs. Resolution (with # burning cells)
There appears to be a logarithmic trend verified by: Logarithmic Plot
Trend follows: 0.0012929*resolution^0.28523
Input files can be found here.

3.2 cm radii, 25.6x25.6 cm domain, 4x4 array

Plot of Error vs. Resolution (with # burning cells)
There appears to be a logarithmic trend verified by: Logarithmic Plot
Trend follows: 0.0021528*resolution^0.23761
Input files can be found here.

Box Case

This run contains one box of PBX with varying dimentions. The Burn Rate was set to 0 within Steady_Burn.cc for this simulation in order to test only surface area.The gas surrounding the cylinders was set to a temperature of 600K in order to set off the Burning Cells flag within Steady Burn. The results of this run are as follows:

Surface Area Error
There appears to be a linear dependence with a factor of 9.6503958e-6 m^2/mm(resolution).
Burning Cells

here

Cylinder Case

This run contains 16 cylinders of PBX with radii 16mm and 32mm (for different cases). The Burn Rate was set to 0 within Steady_Burn.cc for this simulation in order to test only surface area.The gas surrounding the cylinders was set to a temperature of 600K in order to set off the Burning Cells flag within Steady Burn. The results of this run are as follows:

Plot of Error vs. Resolution (with # of burning cells)
There appears to be a logarithmic trends verified by: Logarithmic Plot
Trend follows: 0.0012671*resolution^0.22119

here

Misc.

All file linked to by this page can be found in this directory.
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Contact: josuf dot the dot uf at gmail

Updated: 03/06/09
Created: 02/23/09