Search Results

Driving stability can be an issue for heavy vehicles. In a side wind, a side force and rolling moment will develop, and they both affect driving stability, from which the vehicle may overturn. It is important to understand the flow structure in order to prevent a truck from rolling over. The main purpose of this study is to investigate the flow around a heavy vehicle that causes it to overturn. A 1/8 scaled, simplified tractor/trailer configuration called the Ground Transportation System (GTS) with Reynolds number (based on the GTS width) equal to 1.6 × 106 was used for this study. A side wind was modeled by turning the GTS model with respect to its moment reference point. A triangular mesh was used for the truck and the computational domain surfaces, while hybrid meshes filled the computational domain volume. The Ansys® CFX code based on the k-ω shear stress transport (SST) turbulence model was used to solve the governing equations numerically for an incompressible fluid.

A voltage was applied between the nozzle unit and fine needles, rods, and screens inserted at various axial and radial positions into atomizing full-cone water sprays and the corresponding electrical resistance was measured in an attempt to determine the shape and length of the intact liquid core. The parameters of the experiment were: room temperature; air compressed at 0.1, 1.0, and 2.9 MPa; injection Δp = 13.7 MPa; and five straight-hole nozzles with diameters of 127, 178, 305, 343, and 508 µm, and the same length-to-diameter ratio of 4. The results show that current is carried not only by intact liquid cores but also by atomized unconnected sprays and even across such sprays. Thus the shape of the intact core could be deduced only in the vicinity of the nozzle exit. In the atomization regime, the length of the intact core is found to be proportional to the nozzle diameter and to increase as the square root of the liquid-to-gas density ratio, i.e. xl = Cd(ρℓ /ρg)1/2 where C≈7.