This page uses extracted PDF text. Text can misread numbers, dates or table columns. Check the PDF before quoting or interpreting it. Redacted areas remain redacted.
19
results for SSE and WNW, similar or higher escape percentages would be expected for PM2.5 under those
directions.
-fence baseline,
with 96% escaping the terminal boundary under SW winds. The ¾-wrap fence at both 80 ft and 100 ft
reduces escape to 61% — a meaningful 37% reduction, though PM2.5’s extremely low settling velocity
means a greater fraction remains airborne and is subject to continued transport beyond the fence
shadow. This underscores the importance of maximizing fence coverage and height selection for the
finest particle fractions. See Appendix F for dispersion model images.
Key Important Factors:
1. 100 ft fences often perform worse than 80 ft (higher % leaving)
o
SW ½-
o
WNW ½-
o
WNW ¾-
o
Similar pattern in most other rows (SSE is only marginally worse or equal). Taller is not
automatically better here.
2. Full wrap often worse than ¾-wrap (especially SW)
o
o
o
WNW actually improves with full wrap, but SW is dramatically worse. More coverage is
not always better.
3.
o
Only in SW direction with 80 ft partial wraps:
SW ½-
SW ¾-wrap 80 ft: 29% vs 26%
o
-fence baseline shows the correct
trend (smaller particles escape more easily).
Modeling Explanations of the Results Above
Why 100 ft can be worse than 80 ft Taller fences create a larger recirculation zone (eddy) on
the leeward side and stronger upward deflection of the 15 mph wind. Particles can be lifted over
the top of a 100 ft fence more easily than they would be blocked by an 80 ft one. At exactly 15
mph, the 100 ft height may push the flow regime into more turbulent shedding.
Why full wrap can be worse than ¾-wrap A full 360° enclosure traps wind inside the terminal,
building pressure and generating strong internal vortices or channeling. Particles get recirculated
and eventually exit through the leeward gaps or over the top. A ¾-wrap leaves an intentional
Jump to an indexed page (88 of 88)