FIELD TESTING AND EVALUATION OF DUST DEPOSITION AND ...

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When a vehicle passes over a road, the plume generated behind the vehicle has a discrete depth in the vertical direction. This depth is a measure of the initial breadth of the plume and is different from the plume release height. To account for the fact that the dust plume is initially dispersed by the turbulent wake of the vehicle, a “virtual” distance is added to the value of x in Equation 4-15. For example, the virtual distance x 0 is calculated by solving the equation for the initial value σ z0 . Since σ z is the standard deviation of the concentration in the vertical direction assuming a gaussian (Normal) distribution, then 95% of the plume is initially below the height 2×σ z0 . Therefore, we may approximately define σ z0 as one half the “injection height” or the height of the influence of turbulence generated in the wake of a vehicle. The concept of the “injection height” is discussed in detail in Chapter 5. 4.1.3 The Gillette Box Model This section of the text was provided by Dr. Dale Gillette (NOAA) with some minor adjustments by DRI 4.1.3.1 Formulation and solution A “lumped control volume” approach was used by Gillette to gain understanding of fugitive dust sources. This case considers dust generated from a road surface. By letting the road be directed into and out of the page while wind is directed from right to left, two-dimensionality or symmetry in the direction into the page was invoked. That is, fluxes are equal into and out of the direction into the page. Figure 4-1 shows the geometry of the control volume. A dirt road exists at the right side of the control volume. To the left of the road is a surface that is grass or shrub-covered and does not emit particles. The ceiling of the control volume is the surface of primary interest as to vertical flux. dm/dt up Wind dm/dt ceil dm/dt ambout dm/dt ambin dm/dt road X X=X o dm/dt depos dm/dt ceil dm/dt ambin dm/dt out dm/dt road ∆Z Z=0 ∆L=1 Figure 4-1. Control Volume for Fugitive Dust Model Depicting Vertical and Horizontal Fluxes. The quantities shown in the figure are as follows: 4-6
oad. M is the mass of particles in the control volume (CV), dm up /dt is the mass per unit time passing out vertically at the top of the CV, dm depos /dt is the mass per unit time depositing to the floor of the CV, dm ambout /dt is the mass per unit time passing out of the CV through the left wall, dm ambin /dt is the mass per unit time passing into the CV from the right wall, dm road /dt is the mass per unit time emitted from the road, and dm ceil /dt is the mass per unit time passing out of the ceiling directly above the A conservation of mass equation can be written for the control volume shown in the figure as: dM/dt + dm up /dt + dm depos /dt + dm ambout /dt - dm ambin /dt - dm road /dt + dm ceil /dt = 0 Equation 4-16 where, M is the mass of particles in the control volume (CV), dm up /dt is the mass per unit time passing out vertically at the top of the CV, dm depos /dt is the mass per unit time depositing to the floor of the CV, dm ambout /dt is the mass per unit time passing out of the CV through the left wall, dm ambin /dt is the mass per unit time passing into the CV from the right wall, dm road /dt is the mass per unit time emitted from the road, and dm ceil /dt is the mass per unit time passing out of the ceiling directly above the road. A simplifying assumption is that of steady state emissions, that is, dM/dt = 0. For this case: dm up /dt = - dm depos /dt - dm ambout /dt + dm ambin /dt + dm road /dt - dm ceil /dt 4.1.3.1a road Equation 4-17 Relationship of mass per unit time to the horizontal mass flux from the A subvolume of the control volume is shown in Figure 4-1 as that part that contains the road but no area downwind of the road. The left wall of this part of the control volume is the surface through which all of the dust emitted from the road passes. That is, we specify that none of the road dust is part of the ceiling flux (dm ceil /dt). For the condition of steady state, a description of the conservation of mass for this part of the control volume is: dm road /dt = dm out /dt - dm ambin /dt + dm ceil /dt Equation 4-18 where dm out /dt is the horizontal mass per unit time passing out through an imaginary wall just left of the left edge of the road reaching from the surface to the top of the control 4-7
Page 1:
FIELD TESTING AND EVALUATION OF DUS
Page 5 and 6:
EXECUTIVE SUMMARY The Western State
Page 7 and 8: models. Countess (2001) summarized
Page 9 and 10: TABLE OF CONTENTS 1. INTRODUCTION 1
Page 11 and 12: TABLE OF FIGURES Figure 2-1. Develo
Page 13 and 14: Figure 4-6. The fraction of particl
Page 15 and 16: Figure 5-16. Comparison of fraction
Page 17 and 18: LIST OF TABLES Table 2-1. Parameter
Page 19 and 20: 1. INTRODUCTION 1.1 Background The
Page 21 and 22: 2.BACKGROUND Fugitive dust is emitt
Page 23 and 24: Planetary Boundary Layer (PBL) F =
Page 25 and 26: C D u* = ur The overall drag c
Page 27 and 28: St a vg u g = cA L * Equation 2
Page 29 and 30: Table 2-1. Parameters used in the S
Page 31 and 32: 1E+01 1E+00 z0 = 4.4 cm z0 = 6.4 cm
Page 33 and 34: pathway for deposition for particle
Page 35 and 36: An alternative method for modeling
Page 37 and 38: 3. MEASUREMENT OF DEPOSTION VELOCIT
Page 39 and 40: Department at the University of Uta
Page 41 and 42: In the laboratory, the deposited ma
Page 43 and 44: Table 3-2. Log of all flat substrat
Page 45 and 46: 16 Normalized Deposition Velocity 1
Page 47 and 48: 1.E+05 Deposition Velocity - cm/s 1
Page 49 and 50: are deposition from a horizontally
Page 51 and 52: single element that is intended to
Page 53 and 54: 4. MODELS USED TO STUDY PARTICLE RE
Page 55 and 56: κu ( ) * z 8 fz K zz = exp −
Page 57: C = −6 ( 1× 10 ) QV 2π u s σ
Page 61 and 62: By making the approximation that dm
Page 63 and 64: diameters less than 10 microns. Dis
Page 65 and 66: of such a height is somewhat arbitr
Page 67 and 68: 1 0.9 0.8 1 0.9 0.8 Fraction remain
Page 69 and 70: Fraction of Particles Remaining in
Page 71 and 72: gravitational settling. Stable cond
Page 73 and 74: though it is expected to improve at
Page 75 and 76: 5. DETERMINATION OF PARTICLE REMOVA
Page 77 and 78: PM 10 measured by the DustTrak must
Page 79 and 80: 100% 90% 80% Relative Frequency (pr
Page 81 and 82: average wind speed measured at 12 m
Page 83 and 84: where the subscript i indicates tha
Page 85 and 86: k C int = peakend k C peeakstart d
Page 87 and 88: Height z (m) 14 12 10 8 6 T1_data T
Page 89 and 90: Horizontal fluxes of PM 10 measured
Page 92 and 93: Table 5-2 enumerates the speed-depe
Page 94 and 95: 6 Ratio of AP-42 Emission Factor to
Page 96 and 97: to the ground) giving an approximat
Page 98 and 99: models analyzed in this study is su
Page 100 and 101: Table 6-1. Screen analysis of test
Page 102 and 103: value which was used up to the midp
Page 104 and 105: measured at 3,1. Downwind the dust
Page 106 and 107: trips, the average readings for the
Page 108 and 109:
Fraction of particles of stated siz
Page 110 and 111:
the ground, where particles have a
Page 112 and 113:
particles through the top of the bo
Page 114 and 115:
deposition. Much of the decrease in
Page 116 and 117:
7-8
Page 118 and 119:
Gifford, F.A. (1961). Use of Routin
Page 120:
Venkatram, A. (1993). The Parametri
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