120 research outputs found
Aeroacoustics of isolated and installed jets under static and in-flight conditions
No full textIn modern aircraft configurations, the interaction between the exhausted jet with the wing and high-lift devices is set to increase substantially the total aircraft noise generated during take-off. Regarding ultra-high bypass ratio turbofan engines mounted underneath the wing, the jet plume is expected to interact strongly with rigid surfaces. The interaction between the high-speed flow and aircraft structures modifies the ‘pure’ jet mixing noise and enhance the scattered hydrodynamic field. Thus, understanding the changes to the jet turbulence flow field caused by the presence of a solid boundary is vital to predict and mitigate the engine noise produced by commercial aircraft which will be introduced imminently.In this thesis, the statistics of the streamwise component of the velocity of subsonic jets is investigated in detail. In close-coupled installed jet configurations, the interaction between the jet and a rigid surface leads to a local flow acceleration and to lower turbulence levels near the solid boundary. These effects are consistent with the conservation of momentum and the ‘beak-down’ of the eddies in that region. The characteristic length scales of these installed jet configurations are smaller than the isolated jet scales. The effects of forward flight upon the turbulence field is also considered. A stretching factor with flight velocity is obtained by considering the jet virtual origin. Models for the coherence decay, time and length scales are proposed based on experimental evidence and the assumption of frozen turbulence in the region of maximum turbulence kinetic energy. For the first time, two-point statistic models are proposed for high-subsonic and installed jet configurations. Finally, analysis of the far field of installed jets show that a strong interaction between the jet turbulence field and a solid boundary generates an additional high-frequency noise. Thus, the existence of a noise source mechanism related to the flow-structure interplay is demonstrated. It is hoped that the experimental data and analysis presented in this work provide feedback for jet noise source modelling and also future numerical and large-scale laboratory experiments
Blockage effects on the pressure field of 3D-printed small-scale jet nozzles
No full textThis paper presents a preliminary investigation into the pressure fields of jets exhausting from partially blocked nozzles. Measurements are performed for a series of asymmetric, smallscale, single stream nozzles mimicking the bypass flow from an engine-pylon-wing configuration. The hydrodynamic and acoustic pressure fields of the pylon nozzles are compared to data from an axisymmetric, annular jet baseline nozzle. For the good aerodynamic pylon designs, the isolated jet mixing noise source is slightly modified at azimuthal angles near the blockage. The blockage effects on the installed jet-wing interaction noise source are also small, even when corrections for thrust are applied. In-flight data suggest that a significant increase in the pressure levels exist at relatively high flight-to-jet-velocity ratios for the blocked configurations. For the poorly aerodynamically designed blockages, flow separation occurs close to the nozzle exit. This flow separation induces an augmentation of the jet noise sources. The near-field pressure data shows that the main effects of the pylon are, firstly, an increase in the strength of the hydrodynamic pressure field perpendicular to the pylon surface due to vortex shedding and, secondly, a fast recovery of symmetry downstream of the pylon trailing edge
Investigation into the turbulence statistics of installed jets using hot-wire anemometry
No full textThis work presents a detailed study of theturbulence flow statistics of a jet mounted with its axisparallel to a rigid flat plate. Hot-wire constant tem-perature anemometry has been used to measure thesingle-point and two-point statistics of the axial velocitycomponent at several locations within the jet flow field.Results show that the jet mean flow near the plate sur-face is subjected to a local acceleration and redirectiondue to a Coand ̆a-type effect. The propagation of theseeffects downstream of the plate trailing edge are stronglydependent on the plate position. Regarding the velocityfluctuations, the mean turbulence intensity levels areseen to decrease as the radial distance between the jetand surface decreases. Analysis of the single-point powerspectral density data on the shear layer close to the plateshows that the reduction in magnitude of the low fre-quency content of the energy spectrum is responsiblefor the decrease in turbulence intensity. Additionally,the characteristic time and length-scales computed fromtwo-point measurements reduce as the plate is mountedcloser to the jet centre-line. The axial eddy convectionvelocity is seen to increase in the region of high turbulentkinetic energy in the shear layer adjacent to the surface.Empirical models for turbulence characteristic scalesand eddy convection velocity are presented. These find-ings suggest that both the amplitude and distributionof the jet mixing noise sources are affected when closelyinstalled next to a surface. This paper is a continuationof a recent investigation on the turbulence statistics ofisolated jets presented in Proen ̧ca et al. (2019
Experimental study on the aerodynamics of a high subsonic jet interacting with a flat plate
No full textUnderstanding the turbulent structures and noise source mechanisms resulting from the interaction between the exhausted jet with wing and high-lift devices is essential for both aerodynamic efficiency and noise reduction of the modern aircraft. This work presents an experimental investigation of the mean velocity and turbulence intensity (TI) profiles from an isolated jet and a jet installed beneath a flat plate. Both campaigns are performed in static ambient flow condition and at low and high subsonic velocity. A hot-wire anemometer was used to evaluate the mean velocity and TI for radial and axial profiles. From analysis of the mean velocity, it is evident that a Coandă effect exists in the installed jet case downstream of the trailing edge of the flat plate. The jet is seen to bend towards the plate. A comparison between isolated and installed configurations shows that the presence of the plate also serves to convect the jet asymmetrically downstream (similar to an ejector). Values of mean TI are lower along the shielded lip-line (closest to the plate) than along the unshielded lip-line. Directly after the trailing edge, there is an increase in TI. This fact supports the theory that an additional turbulent structure or wake is created
The effects of internal nozzle blockage in a single stream jet on far-field jet mixing noise
No full textOver the last half century, major reductions in jet mixing noise from aircraft engines have been possible from the study of isolated, axisymmetric jets. However, the impact on noise due to asymmetric effects, like the presence of a pylon connecting the wing to the engine, is not yet fully understood. In this study, the authors seek to establish whether azimuthal changes to the far-field jet noise introduced by the pylon can be predicted using a method called Lighthill's analogy with Ray Tracing (LRT) which is based on a k-ε RANS CFD model. One baseline annular and three increasingly internally blocked single-stream jets are studied and compared to model-scale experimental data. The k-ε RANS model is observed to sufficiently capture the deficit in the axial velocity and turbulent intensity, to within 1 and 0.5%, respectively, from the wake that forms immediately behind the blockage. The RANS CFD does, however, slightly under-predict the TI after 5 effective diameters compared to the experiment data. The increase in pylon thickness is seen to increase the mixing noise present at a polar angle of ninety degrees. At this polar angle, the high frequency modifications to the far field sound pressure level as a function of percentage blockage are captured to within 1 dB of the experimental data. The largest blockage is seen to introduce an additional vortex noise source at mid-Strouhal numbers, which is not modelled by LRT. This blockage is also observed to locally increase the turbulence levels and, therefore, the strength of the fine-scale acoustic sources at St≥2. The authors believe this to be due to the additional mixing of counter-rotating axial vortices. RANS-based noise predictions, using LRT, are shown to be capable of both indicating and diagnosing potentially noisy geometries quickly within an industrial context at the preliminary engine design stage
Dataset DrivAer hp-F: Force Measurements in Yaw Conditions
No full textDataset for the aerodynamic force measurements conducted on the 35% scale DrivAer hp-F model at various yaw angles in the 8x6 wind Tunnel at Cranfield University. The dataset includes aerodynamic force coefficients results from measurement on the following vehicle configurations: - DrivAer hp-F standard configuration (no spoiler or rear wing) - DrivAer hp-F spoiler configuration - DrivAer hp-F rear wing configuration The measurements on the DrivAer hp-F rear wing configuration have been conducted three times for repeability. In reference to the publication: Steven Rijns, Tom-Robin Teschner, Kim Blackburn, Anderson Ramos Proenca, James Brighton; Experimental and numerical investigation of the aerodynamic characteristics of high-performance vehicle configurations under yaw conditions. Physics of Fluids 1 April 2024; 36 (4): 045112. https://doi.org/10.1063/5.0196979 CAD files for the DrivAer hp-F configurations are available at: Rijns, Steven; Teschner, Tom-Robin; Blackburn, Kim; Ramos Proenca, Anderson; Brighton, James (2024). DrivAer hp-F: Spoiler & Rear Wing Configurations Geometry Pack. Cranfield Online Research Data (CORD). Dataset. https://doi.org/10.17862/cranfield.rd.2571520
Dataset DrivAer hp-F: Surface Pressure Measurements in Yaw Conditions
No full textDataset for the surface pressure measurements conducted on the 35% scale DrivAer hp-F model at various yaw angles in the 8x6 Wind Tunnel at Cranfield University.
The dataset includes the surface pressure coefficient results from measurements on the slant of the following vehicle configurations:
- DrivAer hp-F standard configuration (no spoiler or rear wing)
- DrivAer hp-F spoiler configuration
- DrivAer hp-F rear wing configuration
The measurements on the DrivAer hp-F rear wing configuration have been conducted three times for repeatability. The dataset also includes a log file of the data structure and wind tunnel conditions for each experiment.
In reference to the publication: Steven Rijns, Tom-Robin Teschner, Kim Blackburn, Anderson Ramos Proenca, James Brighton; Experimental and numerical investigation of the aerodynamic characteristics of high-performance vehicle configurations under yaw conditions. Physics of Fluids 1 April 2024; 36 (4): 045112. https://doi.org/10.1063/5.0196979
CAD files for the DrivAer hp-F configurations are available at: Rijns, Steven; Teschner, Tom-Robin; Blackburn, Kim; Ramos Proenca, Anderson; Brighton, James (2024). DrivAer hp-F: Spoiler & Rear Wing Configurations Geometry Pack. Cranfield Online Research Data (CORD). Dataset. https://doi.org/10.17862/cranfield.rd.25715202
Note: The updated datasets retain all original data while adding calibrated data to provide (new) users with an additional reference option
Dataset DrivAer hp-F: Wake Total Pressure Measurements in Yaw Conditions
No full textDataset for the wake total pressure measurements conducted on the 35% scale DrivAer hp-F model at various yaw angles in the 8x6 Wind Tunnel at Cranfield University. The measurements are performed on the DrivAer hp-F rear wing configuration with an angle of attack of 15°. The dataset includes the total pressure coefficient results from measurements on the P1, P2, and P3 wake planes, which are located 400 mm, 700 mm, and 1000 mm downstream of the vehicle model respectively. Additionally, the horizontal and vertical measurements positions (in mm) are provided for each wake plane. A horizontal sweep on the P3 wake plane has been conducted three times for repeatability.
In reference to the publication: Steven Rijns, Tom-Robin Teschner, Kim Blackburn, Anderson Ramos Proenca, James Brighton; Experimental and numerical investigation of the aerodynamic characteristics of high-performance vehicle configurations under yaw conditions. Physics of Fluids 1 April 2024; 36 (4): 045112. https://doi.org/10.1063/5.0196979
CAD files for the DrivAer hp-F rear wing configuration are available at: Rijns, Steven; Teschner, Tom-Robin; Blackburn, Kim; Ramos Proenca, Anderson; Brighton, James (2024). DrivAer hp-F: Spoiler & Rear Wing Configurations Geometry Pack. Cranfield Online Research Data (CORD). Dataset. https://doi.org/10.17862/cranfield.rd.25715202
Note: The updated dataset retains all original data while adding calibrated data to provide (new) users with an additional reference option
Dataset DrivAer hp-F: Wake Total Pressure Measurements in Yaw Conditions
No full textDataset for the wake total pressure measurements conducted on the 35% scale DrivAer hp-F model at various yaw angles in the 8x6 Wind Tunnel at Cranfield University.
The measurements are performed on the DrivAer hp-F rear wing configuration with an angle of attack of 15°.
The dataset includes the total pressure coefficient results from measurements on the P1, P2, and P3 wake planes, which are located 400 mm, 700 mm, and 1000 mm downstream of the vehicle model respectively. Additionally, the horizontal and vertical measurements positions (in mm) are provided for each wake plane.
A horizontal sweep on the P3 wake plane has been conducted three times for repeatability.
In reference to the publication:
Steven Rijns, Tom-Robin Teschner, Kim Blackburn, Anderson Ramos Proenca, James Brighton; Experimental and numerical investigation of the aerodynamic characteristics of high-performance vehicle configurations under yaw conditions. Physics of Fluids 1 April 2024; 36 (4): 045112. https://doi.org/10.1063/5.0196979
CAD files for the DrivAer hp-F rear wing configuration are available at:
Rijns, Steven; Teschner, Tom-Robin; Blackburn, Kim; Ramos Proenca, Anderson; Brighton, James (2024). DrivAer hp-F: Spoiler & Rear Wing Configurations Geometry Pack. Cranfield Online Research Data (CORD). Dataset. https://doi.org/10.17862/cranfield.rd.25715202
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Dataset DrivAer hp-F: Surface Pressure Measurements in Yaw Conditions
No full textDataset for the surface pressure measurements conducted on the 35% scale DrivAer hp-F model at various yaw angles in the 8x6 Wind Tunnel at Cranfield University.
The dataset includes the surface pressure coefficient results from measurements on the slant of the following vehicle configurations:
- DrivAer hp-F standard configuration (no spoiler or rear wing)
- DrivAer hp-F spoiler configuration
- DrivAer hp-F rear wing configuration
The measurements on the DrivAer hp-F rear wing configuration have been conducted three times for repeatability.
The dataset also includes a log file of the data structure and wind tunnel conditions for each experiment.
In reference to the publication:
Steven Rijns, Tom-Robin Teschner, Kim Blackburn, Anderson Ramos Proenca, James Brighton; Experimental and numerical investigation of the aerodynamic characteristics of high-performance vehicle configurations under yaw conditions. Physics of Fluids 1 April 2024; 36 (4): 045112. https://doi.org/10.1063/5.0196979
CAD files for the DrivAer hp-F configurations are available at:
Rijns, Steven; Teschner, Tom-Robin; Blackburn, Kim; Ramos Proenca, Anderson; Brighton, James (2024). DrivAer hp-F: Spoiler & Rear Wing Configurations Geometry Pack. Cranfield Online Research Data (CORD). Dataset. https://doi.org/10.17862/cranfield.rd.25715202
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