Browsing by Subject "Automobiles -- Aerodynamics"
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Item Buoyancy effects on automotive engine compartment airflow(Texas Tech University, 1987-12) Sullivan, Paul ThomasThis thesis presents a computational investigation of a two-dimensional, automotive engine compartment. Three primary objectives were considered in this investigation. The first objective was to develop an insight of buoyancy effects on the airflow in an engine compartment of an automobile. The second objective was to develop a general understanding of the basic flow through an engine compartment. The last objective was to study the effects of repositioning the engine in its compartment on the underhood airflow. The computational procedure utilized was tested by comparing predictions with experimental measurements. This comparison indicated that the computational procedure was capable of predicting the overall flow field in a simplified engine compartment reasonably well. This study showed that buoyancy forces, due to temperature gradients present, do not significantly affect the overall airflow in an automotive engine compartment. However, localized areas of flow can be affected by buoyancy, especially hot, stagnant areas.Item Characterization of on-road, automotive wind conditions(Texas Tech University, 1990-05) Duncan, Rod AllenVehicle sensitivity to transient side wind gusts has gained interest in the recent past. Documentation of actual on-road wind conditions is currently lacking. A 1983 Ford Thunderbird has been instrumented to provide information in this area. Collection of naturally occurring wind data measured at a stationary site and on a traveling vehicle on the open road has been performed. Statistical analysis has been performed on collected data in an attempt to characterize on-road wind conditions. A transformation process from moving to stationary coordinates has been developed. A reverse transformation may be utilized using the extensive set of existing stationary wind data to provide information on wind that a vehicle encounters on the open road.Item Coherent structure characterization in the wake of a ground vehicle with a large height to width ratio(Texas Tech University, 1988-12) Williams, Michael TThe turbulent wakes of ground vehicles are as unique as the vehicles themselves. Their complex shapes and close proximity to the ground surface serve only to complicate the structure of the flow fields behind them. As a result of the random and chaotic nature of wake turbulence, researchers must utilize statistical measures such as averages of variables, correlations, and joint probabilities to identify the repeatable coherent structures which are now known to exist. The physical interpretation of statistical results generally requires an intuition based upon companion flow visualization results. The wakes of three simply shaped van models were characterized with a flow visualization study in a water-filled tow tank. The effects of model width and ground clearance on the vortex shedding frequency and statistical properties such as those mentioned above were evaluated. The vortex shedding frequencies from the flow visualization results and auto-correlation results were compared. Mean velocity and turbulence intensity profiles at the lateral and vertical centerlines were produced and qualitatively analyzed.Item Determination of ram coefficients based on front end pressure distributions(Texas Tech University, 2004-12) Pritchard, Rochelle CThe objective of this experiment was to determine a relationship between the pressure distribution on the generic front fascia shape of a new vehicle and the corresponding ram correlation coefficients. For this purpose, a simple theoretical model is presented which establishes the expected relationships between the pressure distribution and ram correlation coefficients. An aspirated cylinder in cross flow was taken as an idealized representation of a vehicle front end and the experimental investigation was carried out in the Texas Tech University Wind Tunnel. Results of the measurements are in agreement with the theoretical expectations for openings which are located at or near the stagnation point or at the location of a pressure coefficient equal to one on the front of the model. For openings significantly further from the stagnation point or close to the location of a zero pressure coefficient on the model, the experimentally determined ram correlation coefficients exhibit less agreement with the theoretical expectationsItem Experimental and computational investigation of the flow field around 2- and 3-dimensional automotive shapes(Texas Tech University, 1988-05) Kudav, Ganesh VOne of the major objectives of automotive aerodynamics research is the reduction of vehicle drag. In addition to the traditional force balance measurements, a detailed investigation of the flow field is important for further reduction of drag in the future cars and for better airflow management within and around them. In the present work, the flow fields around 2- and 3-D Mercury Cougar and Ford Thunderbird scale models were investigated in a wind tunnel flow. Smoke visualization was employed for qualitative investigation. Center plane velocities and turbulence intensities near the surface and wake regions of the models were measured by Laser Doppler Velocimetry (LDV). Surface pressures and wind tunnel floor pressures were also measured at the center plane. An experimental data base for the measured quantities was thus established which will be useful to qualify the present and future computational fluid dynamics (CFD) codes. Two CFD codes: FORDC-2 and FLUENT were used to simulate and compute the flow quantities for the flow around the 2-D models. The computed results are tabulated and compared graphically with the experimental results. The flow fields around the 3-D models are also compared with those around the 2-D models. The visualization studies showed a marked difference in the separation characteristics of flow around the 2- and 3-D models. The LDV technique is very effective in the determination of velocities and turbulence levels. In the model wake, the data rate, however, was very low. The uncertainty in the measured quantities is high compared to those in regions prior to separation. Poor signal to noise ratio of the LDV signal in the wake region is the cause for large measurement uncertainties. The measured turbulence intensities were higher than expected at several locations due the inherent phase noise in the LDV signal. The CFD methods predicted the flow parameters reasonably well up to the separation region. There were significant deviations between the predicted and experimental values of turbulence intensities in the wake region. In addition, the predicted surface pressures and the near-surface velocities were in disagreement with the experimental values. This is attributed to the inadequacy of the "near-wall" model and the K — e turbulence model incorporated in the two codes that were tested.