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In the present work computational fluid dynamics (CFD) simulations of the flow field around a generic tractor-trailer truck are presented and compared with corresponding experimental measurements. A generic truck model was considered which is a detailed 1/8th scale replica of a Class-8 tractor-trailer truck. It contained a number of details such as bumpers, underbody, tractor chassis, wheels, and axles. CFD simulations were conducted with wind incident on the vehicle at 0 and 6 degree yaw. Two different meshing strategies (tet-dominant and hex-dominant) and three different turbulence models (Realizable k-ε, RNG k-ε, and DES) are considered. In the first meshing strategy an unstructured tetrahedral mesh was created over a large region surrounding the vehicle and in its wake. In the second strategy the mesh was predominantly hexahedral except for a few narrow regions around the front end and the underbody which were meshed with tetrahedral cells owing to complex topology.

A numerical method of predicting aeroacoustic performance of HVAC ducts is presented here. The method comprises of two steps. First, the steady state flow structure inside a duct is simulated using computational fluid dynamics (CFD). A k-epsilon based turbulence model is used. In the second step broadband noise source models are used to estimate the sound power generation within the duct. In particular, models estimating dipole and quadrupole sound source strengths are studied. A baseline generic duct geometry was studied with 3 additional design variations. The loudness rankings of these three designs were determined numerically. Simultaneously, the sound generated by these three designs was measured on a flow bench with a microphone kept downstream of the duct outlet. The numerically predicted loudness rankings were compared with experimentally determined rankings and the two are found to be in agreement, thus validating the numerical method.

Minor geometric features in the intake manifold airflow path with side-branch cavities are often responsible for unusual noise due to the complex air flow structure and its interaction with the internal acoustic field. Although airflow bench tests are faster to evaluate various alternate design geometries, understanding the mechanism of such noise generation is necessary for developing an effective design. A 2D computational fluid dynamics (CFD) simulation was performed on a baseline geometry, which produced a distinct whistle, and on a modified geometry, which suppressed the whistle. These 2D models were able to simulate the flow-acoustic coupling responsible for the whistle generation and hence clearly predicted the presence or the absence of a distinct whistle peak as observed in the experimental measurements.

The present study is aimed at studying the use of Detached Eddy Simulation (DES) in simulating truck aerodynamics. A computational procedure based on DES implemented within the Finite Volume Method (FVM) framework is developed. Detailed descriptions of various aspects of the procedure are provided here including mesh generation, solution procedure and post-processing guidelines. The computational procedure is applied to study aerodynamics of a generic Ground Transportation System (GTS) at 0° yaw. This is a largely simplified ⅛th scale model of a tractor-trailer truck. Time-average and transient surface pressures, skin friction coefficients, and wake velocity structures are reported. To assess the accuracy of the present procedure, these are compared with corresponding experimental data reported in literature. Such comparison shows that the present procedure predicts drag coefficient accurately well within the bounds of experimental uncertainty.

A numerical simulation of the flow structure around an idealized automotive A-pillar rain-gutter and the sound radiated from it is reported. The idealized rain-gutter is an infinitesimally thin backward facing elbow mounted on a flat plate. It is kept in a virtual wind-tunnel with rectangular cross-section. The transient flow structure around the rain-gutter is described and time-averaged pressure distribution along the base plate is provided. Time-varying static pressure was recorded on every grid point on the base-plate as well as the rain-gutter surfaces and used to calculate sound pressure signal at a microphone held above the rain-gutter using the Ffowcs-Williams-Hawkings (FWH) integral method was used for calculating sound propagation. Both the transient flow simulation as well as the FWH sound calculation were performed using the commercial CFD code FLUENT6.1.22.