Controlling unsteady cavity flows using internal structures

We report experimental measurements and preliminary analysis on a series of geometric modifications to a rectangular cavity, aimed at alleviating the severity of the aeroacoustic environment. The cavity had a length-to-depth ratio of 5 and a width-to-depth ratio of 1, and featured a simplified representation of a generic missile on the centre line. The modifications consisted of full width and depth ribs or “collars” with a cutout for the missile. Collars could be fitted at various combinations of locations in the cavity and were either straight (i.e. perpendicular to the cavity centre line), leaned or yawed. The cavity flowfield was characterised by surface pressure measurements along the ceiling. Judging from the available measurements the presence of collars modified the mean pressure distribution, and appeared to reduce the acoustic tones and generally lower the broadband noise

AN UNPUBLISHED COIN OF PONTIUS PILATEAND SOME SPECULATIONS ABOUT HIS CAREER

Some years ago Professor Ursula Vogel's husband was given a coin of Pontius Pilate at a congress in Israel. Although a specimen of a well-known type, it may be of interest to publish it here

On the near wake of a Formula One front wheel

Velocity measurements were made in the near wake of the front wheel of a Formula One car using a laser Doppler anemometer. Tests were carried out on a 50% scale in a closed-return three-quarter open-jet wind tunnel. Three configurations were investigated to determine the effect of both the car and an external wheel support strut on the wheel wake. In each of the configurations the test Reynolds number, based on the wheel diameter, was 6.8 × 105. Three components of the velocity were measured at two planes less than than 1.0D(whereDis the wheel diameter) downstream of the wheel axis. These data were used to visualise the extent of the wake, the flow structures present and also the streamwise turbulence intensity. The presence of the car was found to alter significantly the structure of the wheel wake when compared with an isolated wheel. In addition, the external support strut was found to have less impact in the presence of the car than previous isolated wheel studies have suggested. No previous such studies appear to have been published in the open literature

Planar visualization of vortical flows

This article presents two over-looked post-processing techniques which provide the investigator with additional tools for data analysis and visualization. Both techniques exploit the trend for planar experimental data collection and are implemented in two-dimensions. Critically, both techniques are suitable for use on computational and experimental datasets, require no a-priori knowledge of the flow-field, and minimal user interaction during processing. Firstly, line integral convolution will be introduced as an alternative to streamline or in- plane velocity vector visualization. Secondly, a feature identification procedure will be outlined that can be used to reduce datasets for clearer visualization and provide quantitative information about topological flow features

Laser doppler anemometry measurements in the near-wake of an isolated formula one wheel

An experimental investigation was conducted to identify the main structures in the near wake of an isolated Formula One wheel rotating in ground contact. A 50 percent-scale isolated wheel assembly, geometrically similar to the configuration mounted on a Formula One racing car, was tested in a closed-return three-quarter open-jet wind tunnel. The test Reynolds number, based on wheel diameter was 6.8 × 105. Using laser doppler anemometry, three velocity components were measured with a total of 1966 data points across four planes and within one diameter downstream of the wheel axis. Based on analysis of these data, the main characteristics of the near-wake of an isolated wheel rotating in ground contact are presented. A revised model of the trailing vortex system induced in the wake of such a wheel is proposed, which clarifies the contradictory ones published in the literature to dat

Effects of Varying Noise Levels and Lighting Levels on Multimodal Speech and Visual Gesture Interaction with Aerobots

This paper investigated the effects of varying noise levels and varying lighting levels on speech and gesture control command interfaces for aerobots. The aim was to determine the practical suitability of the multimodal combination of speech and visual gesture in human aerobotic interaction, by investigating the limits and feasibility of use of the individual components. In order to determine this, a custom multimodal speech and visual gesture interface was developed using CMU (Carnegie Mellon University) sphinx and OpenCV (Open source Computer Vision) libraries, respectively. An experiment study was designed to measure the individual effects of each of the two main components of speech and gesture, and 37 participants were recruited to participate in the experiment. The ambient noise level was varied from 55 dB to 85 dB. The ambient lighting level was varied from 10 Lux to 1400 Lux, under different lighting colour temperature mixtures of yellow (3500 K) and white (5500 K), and different background for capturing the finger gestures. The results of the experiment, which consisted of around 3108 speech utterance and 999 gesture quality observations, were presented and discussed. It was observed that speech recognition accuracy/success rate falls as noise levels rise, with 75 dB noise level being the aerobot’s practical application limit, as the speech control interaction becomes very unreliable due to poor recognition beyond this. It was concluded that multi-word speech commands were considered more reliable and effective than single-word speech commands. In addition, some speech command words (e.g., land) were more noise resistant than others (e.g., hover) at higher noise levels, due to their articulation. From the results of the gesture-lighting experiment, the effects of both lighting conditions and the environment background on the quality of gesture recognition, was almost insignificant, less than 0.5%. The implication of this is that other factors such as the gesture capture system design and technology (camera and computer hardware), type of gesture being captured (upper body, whole body, hand, fingers, or facial gestures), and the image processing technique (gesture classification algorithms), are more important in developing a successful gesture recognition system. Some further works were suggested based on the conclusions drawn from this findings which included using alternative ASR (Automatic Speech Recognition) speech models and developing more robust gesture recognition algorithm