Effects of Rear Angle on the Turbulent Wake Flow between Two in-Line Ahmed Bodies

Understanding the wake characteristics between two in-line vehicles is essential for improving and developing new strategies for reducing in-cabin air pollution. In this study, Ahmed bodies are used to investigate the effects of the rear slant angle of a leading vehicle on the mean flow and turbulent statistics between two vehicles. The experiments were conducted with a particle image velocimetry at a fixed Reynolds number, R e H = 1.7 × 10 4 , and inter-vehicle spacing distance of 0.75 L , where H and L are the height and length of the model. The rear slant angles investigated were a reference square back, high-drag angle ( α = 25 ° ) and low-drag angle ( α = 35 ° ). The mean velocities, Reynolds stresses, production of turbulent kinetic energy and instantaneous swirling strength are used to provide physical insight into the wake dynamics between the two bodies. The results indicate that the recirculation region behind the square back Ahmed body increases while those behind the slant rear-end bodies decreases in the presence of a follower. For the square back models, the dominant motion in the wake region is a strong upwash of jet-like flow away from the road but increasing the rear slant angle induces a stronger downwash flow that suppresses the upwash and dominates the wake region.

Numerical analyses for improved terminal velocity of deep water torpedo anchor

Purpose This research aims to investigate the effects of manipulation of a torpedo’s geometries to attain higher terminal velocity. The parameters of interest include geometric changes of the original design, as well as sea water properties that reflect water depth in South China Sea. Design/methodology/approach The research make use of computational fluid dynamics (CFD) software, FLUENT, to solve viscous incompressible Navier–Stokes equations with two equations k-epsilon turbulent model. The calculated drag coefficient is subsequently used to calculate the maximum attainable terminal velocity of the torpedo. Findings It was found that the terminal velocity can be improved by sharper tip angle, greater aspect ratio, greater diameter ratio and optimum rear angle at 30°. Sensitivity of drag coefficient toward each of the parameters is established in this paper. Originality/value The paper, in addition to verifying the importance of aspect ratio, has also established the tip angle, diameter ratio and rear angle of the torpedo as important geometric aspects that could be tuned to improve its terminal velocity.

An Attempt to Distinguish between Two Reversal Processing Strategies for Learning Modeled Motor Skill

The first purpose was to examine the effects of reversal processing strategy of visual information on recognition and acquisition of a sequential gross movement task. The second purpose was to examine the relationship between a measure of reversal processing strategy and movements during eye fixation. 24 undergraduates were assigned into one of three conditions, a Reversal-emphasized condition in which subjects were instructed to recognize the movement correctly from a reversed angle, a Recognition-emphasized condition in which subjects were instructed to recognize the movement correctly, and a Recall-emphasized condition in which subjects were instructed to reproduce the movement correctly. Subjects observed stimuli with the model facing them. Following observation, the subjects' recognition of stimuli was tested with model facing towards (Facing Angle) and facing away (Rear Angle). Recall tests were carried out after the two recognition tests. Analysis indicated that accuracy and response time on recognition tests improved under each condition, but there were no other effects. The Reversal-emphasized condition showed significantly greater modeling effect than the other conditions. Movements during eye fixation were very similar among conditions.