A wind tunnel experimenta research program was conducted on a heavily instrumented Ground Transportation System (GTS) vehicle. The GTS baseline model represented a generic 1:8 scale Class-8 van-type tractor trailer geometry. Five base drag reduction add-on devices, instrumented with surface pressure ports, were also tested. These add-on devices included two ogive boattail shapes and three slant geometry devices.Six component force and moment data, surface pressure contours, and wake velocity surveys are presented for each configuration along with qualitative insights gained from flow visualization.This wind tunnel program was designed to complement a parallel research effort in computational fluid dynamics (CFD) which modeled many of these same vehicle geometries. The wind tunnel data are documented and archived in ASCII format on floppy discs and available to researchers interested in further analysis or comparison to other CFD solutions.
The focus of the research was to investigate the fundamental aerodynamics of the base flow of a tractor trailer that would prove useful in fluid flow management. Initially, industry design needs and constraints were defined. This was followed by an evaluation of state-of-the-art Navier-Stokes based computational fluid dynamics tools. Analytical methods were then used in combination with computational tools in a design process. Several geometries were tested at 1:8 scale in a low speed wind tunnel. In addition to the baseline geometry, base add-on devices of the class of ogival boattails and slants were analyzed.
The use of shear-stress-sensitive (SSS) liquid crystals (LCs) has been evaluated as a boundary-layer transition detection technique for hypersonic flows. Experiments were conducted at Mach 8 in the Sandia National Laboratories Hypersonic Wind lunnel using a flat-plate model at near-0-deg angle of attack over the freestream unit-Reynolds-number range (1.2-5.8) x!0 6 /ft. Standard 35-mm color photography and Super VHS color video were used to record LC color changes due to varying surface shear stress during the transition process for a range of commercial SSS liquid crystals. Visual transition data were compared with an established method using calorimetric surface heat-transfer measurements to evaluate the LC technique. It is concluded that the use of SSS LCs can be an inexpensive, safe, and easy-to-use boundary-layer transition detection method for hypersonic flows. However, a valid interpretation of the visual records requires careful attention to illumination intensity levels and uniformity and to lighting and viewing angles, some prior understanding of the general character of the flow, and the selection of the appropriate liquid crystal for the particular flow conditions. Nomenclature M = Mach number P = pressure, psia q = heat transfer rate, Btu/ft 2 • s Re = unit Reynolds number, ft" 1 T -temperature, °R t = time, s X = distance from leading edge, in. a = angle of attack, deg r = shear stress, lbf/ft 2 Subscripts c = calculated cw = cold wall i = initial conditions, t = 0 m = measured r = recovery 0 = stagnation conditions oo = freestream conditions
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