2 edition of Prediction of rotor noise in non-uniform flow. found in the catalog.
Prediction of rotor noise in non-uniform flow.
M. V. Lowson
by Loughborough University of Technology, Department of Transport Technology in Loughborough
Written in English
|Contributions||Loughborough University of Technology. Department of Transport Technology.|
Open rotor interaction noise reduction through front rotor wake modification. Tonal Noise Prediction of a Turbofan with Heterogeneous Stator and Bifurcations. Sound Generation of a Turbine Stage Due to Non-uniform Mean Flow Temperatures. Zhongqiang Mu. A blade vortex interaction (BVI) is an unsteady phenomenon of three-dimensional nature, which occurs when a rotor blade passes within a close proximity of the shed tip vortices from a previous blade. The aerodynamic interactions represent an important topic of investigation in rotorcraft research field due to the adverse influence produced on rotor noise, particularly in low speed descending.
Also, the Kirchhoff integration will be improved to account for non-uniform flow through the Kirchhoff surface. Related Publications: Strawn, R. C., Biswas, R., and Lyrintzis, A. S., "Helicopter Noise Predictions Using Kirchhoff Methods," presented at the 51st Annual Forum of the American Helicopter Society, May , (see also Journal of. This paper presents the acoustic performance of a novel approach for the passive adaptive control of tonal noise radiated from subsonic fans. Tonal noise originates from non-uniform flow that causes circumferentially varying blade forces and gives rise to a considerably larger radiated dipolar sound at the blade passage frequency (BPF) and its harmonics compared to the tonal noise generated by.
Rosenberg, A, Selvaraj, S and Sharma, A () A Novel Dual-Rotor Turbine for Increased Wind Energy Capture. Journal of Physics: Conference Series, (1) ().(Han, F, Sharma, A, Paliath, U and Shieh, C () Multiple pure tone noise prediction. Journal of Sound and Vibration, (25) ().(Takle, ES, Rajewski, DA, Lundquist, JK, Gallus Jr, WA and Sharma, A ( Far field computations were performed for a large wind turbine to evaluate the effects of non-uniform aerodynamic loading over the rotor disk. A modified version of the Farassat/Nystrom propeller noise prediction program was applied to account for the variations in loading due to inflow interruption by the upstream support tower. The computations indicate that for the uniform inflow case.
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A benchmark dedicated to RANS-informed analytical methods for the prediction of turbofan rotor–stator interaction broadband noise was organised within the framework of the European project TurboNoiseBB.
The second part of this benchmark focuses on the impact of the acoustic models. Twelve different approaches implemented in seven different acoustic solvers are compared.
Noise prediction results are presented for single propeller and ducted propeller in non-uniform flow conditions similar to real situation. The investigation reveals that the effect of a duct on the acoustic performance propeller is small in the far field under non-cavitating situations since the noise directivities of single and ducted Cited by: The proposed procedure for open rotor noise prediction does remarkably well in predicting the speed scaling of the rotor–rotor interaction tones, as is evident from Fig.
9, Fig. 10, even though the absolute noise levels are slightly over-predicted. Linear curve fits (on a log–log scale) are plotted in the by: Both inlets delivered flow to the same NASA/GE R4 fan rotor at equal corrected mass flow rates.
Although the source strength at the fan is increased by 45 dB in sound power level due to the non-uniform inflow, far-field noise for the serpentine inlet duct is increased on average by only dBA overall sound pressure level in the forward : J. Defoe, Z. Spakovszky. The unsteady loading noise is mainly governed by irregularities—the fluctuation of surface pressure, while the thickness noise is dominated by the periodicity of propeller rotation.
Since the noise prediction is highly affected by inflow conditions, the directivity of the noise generated by propeller in non-uniform flow is by: NASA Langley Research Center, Hampton, VA K.
Brentner 6 Available Methods for Rotor Noise Prediction Acoustic Analogy treats real flow effects by fictitious sources; exact in principle for rotor blades: Ffowcs Williams–Hawkings equation () most developed, widely used in the helicopter industry Kirchhoff Formula originally suggested by Hawkings (); (Farassat and Myers ).
Try the new Google Books Get print book Lieblein loading loss machines mass flow mass flow rate measurements meridional meridional flow Mikolajczak multistage compressors noise non-uniform normal outlet flow overall performance prediction pressure gradient pressure ratio radius relative Reynolds number rotating stall rotor secondary flow.
A prediction method is developed for the self-generated noise of an airfoil blade encountering smooth flow. The prediction methods for the individual self-noise mechanisms are semiempirical and are based on previous theoretical studies and data obtained from tests of two- and three-dimensional airfoil blade sections.
The self-noise mechanisms are due to specific boundary-layer phenomena, that. A numerical study on the acoustic radiation of a propeller interacting with non-uniform inflow has been conducted. Real geometry of a marine propeller DTMB is used in the calculation, and sliding mesh technique is adopted to deal with the rotational motion of the propeller.
The performance of the DES (Detached Eddy Simulation) approach at capturing the unsteady forces and. American Institute of Aeronautics and Astronautics Sunrise Valley Drive, Suite Reston, VA The sources of noise are split into propulsive (§ ) and non-propulsive components (§ ).
We include a discussion of the APU noise as a separate item (§ ). The propeller-noise model (§ ) is discussed in isolation from airframe and engines. Chapter 17 deals with propagation effects.
Chapter 18 deals with noise trajectories. Aeroacoustics of Low Mach Number Flows: Fundamentals, Analysis, and Measurement provides a comprehensive treatment of sound radiation from subsonic flow over moving surfaces, which is the most widespread cause of flow noise in engineering systems.
This includes fan noise, rotor noise, wind turbine noise, boundary layer noise, and aircraft noise. The unsteady flow, especially the potential effects created by the stator vanes, is then investigated, showing that the stator potential field is responsible for a major secondary tonal noise source on the rotor blades.
The rotor wake velocity and turbulent content correspond to the excitations for tonal and broadband noise, respectively. A major source of contra-rotating open rotor (CROR) tonal noise is caused by the interaction of the front-rotor (FR) wakes with the aft-rotor blades.
Inspired by chevron nozzles, which increase the mixing process in jet shear layers, serrations are implemented at the FR trailing-edge in order to increase the wake mixing and thus reduce the tones. A previously-developed body-force-based fan modeling approach was used to assess the change in fan rotor shock noise generation and propagation in a boundary-layer-ingesting, serpentine inlet.
This approach is employed here in a parametric study to assess the effects of inlet geometry parameters (offset-to-diameter ratio and downstream-to. Prediction of helicopter rotor discrete frequency noise: A computer program incorporating realistic blade motions and advanced acoustic formulation A computer program has been developed at the Langley Research Center to predict the discrete frequency noise of conventional and advanced helicopter rotors.
The program, called WOPWOP, uses the most advanced subsonic. A Refinement of Asymptotic Predictions and Full Numerical Solution of Helicopter Rotor Noise in the Far Field 1 September | International Journal of Aeroacoustics, Vol. 11, No. On Sound Generation by Moving Surfaces and Convected Sources in a Flow.
An analytically based model for the prediction of upstream-radiated rotor–stator interaction noise is described, and includes the important effect of mean swirling flow on both the rotor wake evolution and the acoustic response.
Frequency Domain Prediction Methods for Tone Noise Broadband Noise from Rotors Haystacking of Broadband Noise Blade Vortex Interactions Duct Acoustics Introduction Sound Waves in Cylindrical Ducts Duct Liners The Greens Function for a Cylindrical Duct with Flow Sound Power in Ducts Non Uniform.
• Noise Sources: Flow Nonuniformities: Inlet Turbulence, Boundary Layers, Tip and Hub Vortices,Wakes etc. • Mechanism: Interaction with Rotating Components (rotor noise), Scattering by Sharp Edges (trailing edge noise), Impingement of Unsteady Nonuniformities on Guide Vanes (rotor.
Evaluation of Semi-Empirical Methods for the Prediction of Helicopter Rotor Noise,” NASA TMComputational Methods Integral methods Acoustic Analogy Kirchhoff Method Direction computations Practical Approaches to Noise Prediction.non-uniform velocity distributions upstream of the fan.
(3) Time fluctuation of pressure distributions on the blade surface by the potential interaction with engine components downstream of the fan. Thus, for BPF noise prediction, the use of a simulation method which can represent the three items above will be required. Fig. 1 Overview of.Accurate prediction of HSI noise for hovering helicopter rotors proves the ability of the proposed formulation for noise computation from rotating sources.
The capability of explicitly accounting for the influence of inflow on the radiated noise is displayed by the forward flight helicopter rotor case.