Two-fluid Model Approach Research Articles

Experimental and theoretical porosity profiles in a two-dimensional gas-fluidized bed with a central jet

A light transmission technique has been developed for measurement of the local porosity in two-dimensional gas-fluidized beds. The principles of liquid-solid fluidization and vibrofluidization were employed to perform the necessary calibration. Time-averaged porosity profiles have been measured in a thin two-dimensional gas-fluidized bed with a central rectangular jet. These profiles were predicted satisfactorily with a previously developed first principles hydrodynamic model, without the use of any fitted parameters. The hydrodynamic model is based on a two-fluid model approach in which both phases are considered to be continuous and fully interpenetrating.

Trip time-stop time studies of extreme driver behaviors

The focus of the present study has been to investigate the extent to which drivers with “extreme” modes of behavior deviate from the “normal” (chase-car) trend in a given city. The experiment consisted of collecting trip time-stop time data in the Central Business District (CBD) of Roanoke, Virginia, using three vehicles circulating simultaneously in the area. While one of the three vehicles was engaged in the chase-car mode, the other two vehicles were driven aggressively or conservatively. Similar data were also collected in the Austin, Texas, CBD. Using the data for each driver type, three two-fluid trends are established for the Roanoke CBD: an aggressive, a normal (chase-car), and a conservative trend. On a trip time-stop time diagram, while the conservative and aggressive trends are essentially parallel, the conservative trend approaches the normal trend at off-peak periods. The aggressive trend, on the other hand, approaches the normal trend at peak periods. The differences among the trends, however, are by and large statistically significant. Similar results have been obtained in Austin—despite uncertainties at high levels of demand, where the normal trend may cross the aggressive trend. The results also underline the importance of common data collection techniques when comparing the quality of traffic service of various cities using the two-fluid model approach. In assessing the statistical significance of differences among the two-fluid trends of various city networks, the potential impact of driver behavioral variations must be considered.