1,746,959 research outputs found
Large-eddy simulation of the interaction of a jet with a wing
No full textThis paper presents progresses made on aircraft installation effects using numerical methods under WP 3.2 of SYMPHONY, a project supported by Technology Strategy Board, UK. Large-eddy simulations (LES) were performed for turbulent flow around a wing under the influence from engine jet flow by solving the compressible Navier-Stokes equations using an in-horse high-order finite difference code. Simulations were performed for jet under both a clean wing and the wing at high-lift configuration. Installation effects on both the jet and the wing are analysed by comparing with LES results performed for three baseline cases: jet along, clean wing along and the wing in high-lift configuration. It is found that the flow is two-dimensional near the leading edge of the wing. Further down-stream three-dimensional flow features are developed. Interaction with vortical jet stream accelerates developments of the flow underneath the wing. Stronger turbulent structures are seen within the jet shear layer near the wing and their interaction with the wing causes surface pressure fluctuations, which results in increased radiated noise. Interaction with the jet causes a reduction in lift for the clean wing, however the contribution from the flap is increased when the wing is in high-lift configuration. For the current geometry the jet stream does not hit the clean wing, and it is shifted towards the wing by a small angle (one degree) due to low pressure region under the wing. When the ap is deployed, jet stream hits the flap and is deflected away from the wing
Sound radiation from a generic bypass duct with bifurcations
No full textThe influence of bifurcations in an aero-engine bypass duct on noise radiation was investigated through high-order accurate three-dimensional numerical simulations. The physical process was described by a set of acoustic perturbation equations (APE), with a background mean flow. Four bifurcation arrangements, with an airfoil cross-section, were regularly placed in circumferential direction. Results of the simulations were compared with those of a clean duct case. A circumferential mode of m=12 with radial mode of n=1 and multi-n modes at a source frequency of 1547 Hz were set as acoustic inputs. Acoustic modes
interfered with the bifurcations resulting in a doubled circumferential mode pattern in the near field acoustic pressure distribution and slightly stronger sound
pressure level behind the bifurcations. Far field noise computations indicated 3.2 dB and 2.0 dB sound pressure level increases for radial mode of n=1 and multi-n
modes respectively. The bifurcations did not alter the radiation angle. A comparison was also made between APE and linearlised Euler equations (LEE). Results showed that the APE simulation produced almost identical far field sound
prediction to the LEE, with a small difference (< 0.8dB) at the main radiation peak angle
The evolution of edge vortices underneath a diffuser equipped bluff body
No full textThe edge vortices generated by a diffuser equipped bluff body in ground effect were experimentally studied using a range of methods including particle image velocimetry (PIV), oil flow visualisation andforces. Two edge vortices were observed originating from each side of the diffuser caused by the flow separating off the side off the model and swirling underneath the model. The edge vortices were foundto enhance the downforce generated by the model as the ride height was decreased. At low values of ride height the edge vortices broke down due to the streamwise pressure gradient within the diffuser becoming too severe. This impacted on the forces such that a reduction in downforce and increase in drag was observed. The vortices were generated close the diffuser inlet, evolving from regions of weak recirculation into concentrated vortices which moved inboard and vertically up as the location moved downstream
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