Loading...
6 results
Search Results
Now showing 1 - 6 of 6
- Numerical Study of a Central Downwash Generating WingPublication . Correia, João P. S.; Silva, André; Barata, Jorge M MIn October 2005, FIA (International Automobile Federation) proposed a set of rules, for the 2008/9 Formula 1 Championship, with the objective of decreasing the difficulties for overtaking due to the wake generated by the leading car. The proposal is based on the utilization of a new concept of a double rear wing "CDG-wing" (Central Downwash Generating Wing). The objectives of this work is to analyze the aerodynamic characteristics of the CDG wing proposed by FIA, and to investigate its better positioning relative to the rear wheel. The study was performed using three different geometries of the wing, and three different speeds, to reproduce three different curves of some race tracks used in Formula 1. The computational tests have shown that the location of the wings behind the rear tire increases the downforce.
- Numerical Optimization of the Location of F1 CDG WingsPublication . Barata, Jorge M M; Correia, João P. S.; Silva, AndréIn October 2005, FIA (International Automobile Federation) proposed a set of rules, for the 2008/9 Formula 1 Championship, with the objective of decreasing the difficulties for overtaking due to the wake generated by the leading car. The proposal is based on the utilization of a new concept of a double rear wing "CDG-wing" (Central Downwash Generating Wing). The objectives of this work is to analyze the aerodynamic characteristics of the CDG wing proposed by FIA, and to investigate its better positioning relative to the rear wheel. The study was performed using three different geometries of the wing, and three different speeds, to reproduce three different curves of some race tracks used in Formula 1. The computational tests have shown that the location of the wings behind the rear tire increases the downforce.
- Numerical study of spray dispersion in a premixing chamber for Low-NOx enginesPublication . Barata, Jorge M M; Silva, AndréThe present work describes a numerical study of a confined two-phase flow under high-pressure conditions, typical of gas turbine combustors. An Eulerian frame was used for the gas phase together with a Lagrangian approach to describe the dispersed phase. The computational method was extended to high-pressure environments, which are more representative of the practical gas turbine operating conditions. The results are compared with experimental data, and revealed the ability of the model to increase the knowledge of the turbulent dispersion phenomena for this type of practical conditions (high pressure and confined flow).
- Laser-Doppler Analysis of the Separation Zone of the Ground Vortex FlowPublication . Silva, André; Durão, Diamantino; Barata, Jorge M M; Santos, Pedro José da Costa Teixeira; Ribeiro, SamuelLaser Doppler measurements are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The experiments were performed for a wall jet-to-boundary layer velocity ratio of 2, and include mean and turbulent velocity characteristics along the two normal directions contained in planes parallel to the nozzle axis. The results, which have relevance to flows encountered by powered-lift aircraft operating in ground effect, quantify the structure of the complex ground vortex flow resulting from the collision of a wall jet with a boundary layer. The results revealed the existence of a very low-frequency instability. The source of this low frequency unsteadiness is probably associated with a small vortex located near the separation point. In the central zone of the upwash flow where the maximum values of the vertical velocity component occurs, additional distinct high frequency peaks were also identified.
- Numerical Study of Cryogenic Jets Under Supercritical ConditionsPublication . Barata, Jorge M M; Gokalp, Iskender; Silva, AndréThe present work is devoted to the study of cryogenic nitrogen jets in sub- and supercritical conditions. A general trend to operate under increasingly higher combustor pressures is observed in rockets, gas turbines, and diesel engines, primarily as a result of enhanced effects on thrust, power, or efficiency. In these conditions the injected fluid(s) can experience ambient pressures exceeding the critical pressure(s) of the propellants, and recent experimental work of Chehroudi et al. showed a quantitative similarity to gas-jet-like behavior (Chehroudi, B., Conn, R., and Talley, D.. "Spray/Gas Behaviour of Cryogenic Fluids under Sub- and Supercritical Conditions," Paper. July 2000; Chehroudi. B., Cohn, R., and Talley, D.. "Initial Growth Rate and Visual Characteristics of a Round Jet into a Sub- to Supercritical Environment of Relevance to Rocket, Gas Turbine, and Diesel Engines," AIA A Paper 99-0206, Jan. 1999). This conclusion suggested that it would be expected that the mathematical models and numerical methods used for gaseous flows could also be used for supercritical flows. This paper reports an investigation, exploring this hypothesis, and aims to evaluate the capabilities and limitations of a computational method developed for incompressible but variable density flows when applied to supercritical conditions. The predicted initial jet growth rate was compared with available experimental data for liquid/gaseous jets and mixing layers and showed a good agreement for different supercritical density ratios. For subcritical conditions, when the flow deviates from the gaseous-like behavior, and approaches a more spray-like behavior the incompressible gaseous flow formulation was found inadequate.
- Experimental Study of a Ground VortexPublication . Barata, Jorge M M; Ribeiro, Samuel; Santos, Pedro José da Costa Teixeira; Silva, AndréLaser-Doppler measurements of the mean and turbulent components of the velocity flowfield resulting from the frontal collision of a wall jet with a boundary layer are presented and discussed, together with the visualization of the flow with direct photography and digital film imaging. The experiments were carried out for boundary-layer-to-wall- jet velocity ratios of 0.5 and 0.58. The results revealed the existence of a small counter-rotating recirculating zone located upstream (in the sense of the wall-jet flow) of the separation point, not reported before for this type of flow. This secondary vortex has an oscillating behavior observed in other ground-vortex flows, similar to that which can be observed, namely, through the bimodal histogram of the horizontal velocity (parallel to the wall) measurements, although the power spectra measurements do not exhibit any particular peaks.