Downwind cell

Figure 2.60 Pictorial representation of the SLIC scheme showing the updating scheme for an upwind and a downwind cell. Cells filled with fluid 1 are indicated in gray, those with fluid 2 in white. Cells containing a mixture of both fluids are represented by hatched areas. In the right column the configuration at the new time step is shown, with interface positions depicted explicitly.

The spreadsheet should also have cells providing the downwind distance, the total area of the plume, and the maximum width of the plume, all based on the isopleth values. 

Differential sensory sensitivity. The insect s perception of plant odours differs essentially from their discrimination of non-volatile taste substances, as phytophagous insects may already perceive the odour at some distance from the plant. In adult phytophagous insects the antennae bear a large number of olfactory sensilla in order to detect the minute concentrations of the leaf odour components in the air downwind from a plant. The overall sensitivity of the antennal olfactory receptor system can be measured by making use of the electroantennogram technique (17). An electroantennogram (EAG) is the change in potential between the tip of an antenna and its base, in response to stimulation by an odour component. Such an EAG reflects the receptor potentials of the olfactory receptor cell population in the antenna. 

The authors have used this intermediate approach to treat power plants in the Los Angeles Basin modeling study (50). Some of these plants are situated along the coastline, and their emissions are advected across the Basin under prevailing wind conditions. Typically emissions from these plants travel a horizontal distance of 2-5 miles before they are considered well-mixed in the vertical. Since an individual cell is 2 miles by 2 miles and horizontal dispersion of the plume under low winds extends about 2 miles after a 2-5 mile traverse, the assumption of approximately uniform distribution immediately downwind of the source is reasonable. A computational scheme for apportioning emissions among cells downwind of the source under these circumstances is described by Roberts et al. (50). 

The functional relationship of the HRIC scheme is also function of the angle 6 between the normal to the interface and the normal to the cell face (Fig. 8). For an interface aligned with the cell face (9 = 0), the bounded downwind scheme is used, while for an interface perpendicular to the cell face, the upwind scheme is used. For an interface with 6 between these two limits,/(0) is chosen to be V cos 6 and the blending formula is given by... 

The dispersal pan was mounted on load cells that allowed determination of total amount of chemical released into the pan. Heat flux sensors were placed at locations downwind and crosswind from the pan containing the released material. These were evidently to measure the amount of radiant heat. These locations had two heights at which measurements were recorded, 3 and 6 ft above ground level. In addition, temperatures were recorded at three locations (1) the air temperature approximately 3 ft above the pan bottom, (2) the reaction temperature approximately 3 in above the chemical level, and (3) the chemical temperature approximately 2 in above the pan bottom. 

Compute x, the downwind distance, at each cell in grid. 

The computational domain extended 170 m in the X direction (from 20 m upwind to 150 m downwind from the release point), 30 m in the Y direction (symmetric crosswind plan from the release point) and 10 m in the Z direction the cells were initially represented by 1 m x 1 m x 0.5 m cuboids (forming the macro grid). 

During our thrust chamber programs, we have taken a number of samples from the atmosphere in areas downwind of the test site, and in no case has a concentration of more than a few parts per million been detectable several thousand feet from the test site. A test cell and the surrounding area can be entered within three minutes of the completion of a test firing, with only a trace of an odor prevailing. 

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