Browsing by Author "Knowles, R. D."

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    Laser doppler anemometry measurements in the near-wake of an isolated formula one wheel
    (Springer Science Business Media, 2007-05-01T00:00:00Z) Saddington, Alistair J.; Knowles, R. D.; Knowles, Kevin
    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 date
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    Monoposto racecar wheel aerodynamics: investigation of near-wake structure and support-sting interference
    (Cranfield University, 2007-12-12T15:43:06Z) Knowles, R. D.; Knowles, Kevin; Saddington, Alistair J.
    Monoposto racecar development is routinely carried out using wheels supported not by the car suspension but by individual, externally-mounted stings. The interference effect of these stings was acknowledged but unquantified in the existing literature. Appraisal of the literature has found that the structure of a wheel wake was not understood, rendering it difficult to assess the support sting interference. These two issues were thus jointly addressed using experimental and computational methods. The two phases of this project each tested a different industrially-representative racecar wheel model. Phase One investigated a single wheel and sting combination, whilst Phase Two extended the work to include two further stings and a model racecar. Non-intrusive velocity measurements were made in the near wakes of the various combinations to extract vertical planes, perpendicular to the tunnel freestream. The measurements made behind the isolated wheels were used to investigate the main flow features of the wake. The flow surrounding an unsupported wheel was established computationally and used to evaluate the interference effects of the support sting. Different wheel support methods (three stings and the car suspension) were used to provide further insight into the sting interference effects and also the impact of sting design on those effects. Testing with and without the model racecar allowed evaluation of its effect on the wheel wake and sting interference. The main characteristics of the near-wake of an isolated wheel rotating in ground contact are proposed from analysis of the data generated in this study. A simplified model of the trailingvortex system induced in the wake of such a wheel is proposed to clarify contradictory literature. The specific interference effects of a wheel support sting are proposed with reference to the main characteristics of the wake. The mechanisms behind these effects are, where possible, identified and presented. The main impact of the support sting, and thus the root of several of the observed effects, is the modification of the axial flow through the wheel. The main effects of the presence of the car on the near-wake are proposed alongside the observation that the wake structure is not fundamentally different to that of an isolated wheel. The proposed sting interference effects are also observed in the presence of the car, albeit at a reduced level.
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    On the near wake of a Formula One front wheel
    (Professional Engineering Publishing, 2013-12-31T00:00:00Z) Knowles, R. D.; Saddington, Alistair J.; Knowles, Kevin
    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.
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    Planar visualization of vortical flows
    (SAGE Publications, 2006-06-01T00:00:00Z) Knowles, R. D.; Finnis, Mark V.; Saddington, Alistair J.; Knowles, Kevin
    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.