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Article
Publication date: 19 June 2019

Seyed Hamid Delbari, Amir Nejat, Mohammad H. Ahmadi, Ali Khaleghi and Marjan Goodarzi

This study aims to carry out numerical modeling to predict aerodynamic noise radiation from four different Savonius rotor blade profile.

Abstract

Purpose

This study aims to carry out numerical modeling to predict aerodynamic noise radiation from four different Savonius rotor blade profile.

Design/methodology/approach

Incompressible unsteady reynolds-averaged navier-stokes (URANS) approach using gamma–theta turbulence model is conducted to obtain the time accurate turbulent flow field. The Ffowcs Williams and Hawkings (FW-H) acoustic analogy formulation is used for noise predictions at optimal tip speed ratio (TSR).

Findings

The mean torque and power coefficients are compared with the experimental data and acceptable agreement is observed. The total and Mono+Dipole noise graphs are presented. A discrete tonal component at low frequencies in all graphs is attributed to the blade passing frequency at the given TSR. According to the noise prediction results, Bach type rotor has the lowest level of noise emission. The effect of TSR on the noise level from the Bach rotor is investigated. A direct relation between angular velocity and the noise emission is found.

Practical implications

The savonius rotor is a type of vertical axis wind turbines suited for mounting in the vicinity of residential areas. Also, wind turbines wherein operation are efficient sources of tonal and broadband noises and affect the inhabitable environment adversely. Therefore, the acoustic pollution assessment is essential for the installation of wind turbines in residential areas.

Originality/value

This study aims to investigate the radiated noise level of four common Savonius rotor blade profiles, namely, Bach type, Benesh type, semi-elliptic and conventional. As stated above, numbers of studies exploit the URANS method coupled with the FW-H analogy to predict the aeroacoustics behavior of wind turbines. Therefore, this approach is chosen in this research to deal with the aeroacoustics and aerodynamic calculation of the flow field around the aforementioned Savonius blade profiles. The effect of optimal TSR on the emitted noise and the contribution of thickness, loading and quadrupole sources are of interest in this study.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 6
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 July 2021

Zi Kan, Daochun Li, Shiwei Zhao, Jinwu Xiang and Enlai Sha

This paper aims to assess the aeroacoustic and aerodynamic performance of a morphing airfoil with a flexible trailing edge (FTE). The objective is to make a comparison of…

Abstract

Purpose

This paper aims to assess the aeroacoustic and aerodynamic performance of a morphing airfoil with a flexible trailing edge (FTE). The objective is to make a comparison of the aerodynamic noise characteristics between the conventional airfoil with a flap and morphing airfoil and analyse the noise reduction mechanisms of the morphing airfoil.

Design/methodology/approach

The computational fluid dynamic method was used to calculate the aerodynamic coefficients of morphing airfoil and the Ffowcs-Williams and Hawking’s acoustic analogy methods were performed to predict the far-field noise of different airfoils.

Findings

Results show that compared with the conventional airfoil, the morphing airfoil can generate higher lift and lower noise, but a greater drag. Additionally, the noise caused by the one-unit lift of the morphing airfoil is significantly lower than that of the conventional airfoil. For the morphing airfoil, the shedding vortex in the trailing edge was the main noise resource. As the angle of attack (AoA) increases, the overall sound pressure level of the morphing airfoil increases significantly. With the increase of the trailing edge deflection angle, the amplitude and the period of sound pressure of the morning airfoil fluctuation increase.

Practical implications

Presented results could be very useful during designing the morphing airfoil with FTE, which has significant advantages in aerodynamic efficiency and aeroacoustic performance.

Originality/value

This paper presents the aerodynamic and aeroacoustic characteristics of the morphing airfoil. The effect of trailing edge deflection angle and AoA on morphing airfoil was investigated. In the future, using a morphing airfoil instead of a traditional flap can reduce the aircraft`s fuel consumption and noise pollution.

Details

Aircraft Engineering and Aerospace Technology, vol. 93 no. 5
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 5 September 2016

Lyaysan Ildusovna Garipova, Andrei Sergeevich Batrakov, Alexander Nikolaevich Kusyumov, Sergey Anatolievich Mikhaylov and George Barakos

The design of main rotor blade tips is of interest to helicopter manufactures since the tip details affect the performance and acoustics of the rotor. The paper aims to…

Abstract

Purpose

The design of main rotor blade tips is of interest to helicopter manufactures since the tip details affect the performance and acoustics of the rotor. The paper aims to discuss this issue.

Design/methodology/approach

In this paper, computation fluid dynamics is used to simulate the flow around hovering helicopter blades with different tip designs. For each type of blade tip a parametric study on the shape is also conducted for comparison calculations were performed the constant rotor thrust condition. The collective pitch and the cone angles of the blades were determined by at an iterative trimming process.

Findings

Analysis of the distributed blade loads shows that the tip geometry has a significant influence on aerodynamics and aeroacoustics especially for stations where blade loading is high.

Originality/value

The aeroacoustic characteristics of the rotors were obtained using Ffowcs Williams-Hawkings equations.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 7
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 2 January 2018

Hasan Kamliya Jawahar, Yujing Lin and Mark Savill

The purpose of this paper is to investigate airfoil self-noise generation and propagation by using a hybrid method based on the large-eddy simulation (LES) approach and…

Abstract

Purpose

The purpose of this paper is to investigate airfoil self-noise generation and propagation by using a hybrid method based on the large-eddy simulation (LES) approach and Curle’s acoustic analogy as implemented in OpenFOAM.

Design/methodology/approach

Large-eddy simulation of near-field flow over a NACA6512-63 airfoil at zero angle of attack with a boundary layer trip at Rec = 1.9 × 105 has been carried out using the OpenFOAM® computational fluid dynamics (CFD) code. Calculated flow results are compared with published experimental data. The LES includes the wind tunnel installation effects by using appropriate inflow boundary conditions obtained from a RANS κω SST model computation of the whole wind tunnel domain. Far-field noise prediction was achieved by an integral method based on Curle’s acoustic analogy. The predicted sound pressure levels are validated against the experimental data at various frequency ranges.

Findings

The numerical results presented in this paper show that the flow features around a NACA6512-63 airfoil have been correctly captured in OpenFOAM LES calculations. The mean surface pressure distributions and the local pressure peaks for the step trip setup agree very well with the experimental measurements. Aeroacoustic prediction using Curle’s analogy shows an overall agreement with the experimental data. The sound pressure level-frequency spectral analysis produces very similar data at low to medium frequency, whereas the experimentally observed levels are slightly over predicted at a higher frequency range.

Practical implications

This study has achieved and evaluated an alternative aeroacoustic simulation method based on the combination of LES with a simple Smagorinsky SGS model and Curle’s analogy, as implemented in the OpenFOAM CFD code. The unsteady velocity/pressure source data produced can be used for any simpler analytically based far-field noise prediction scheme.

Originality/value

A complete integration of the LES and Curle’s acoustic analogy for aeroacoustic simulations has been achieved in OpenFOAM. The capability and accuracy of the hybrid method are fully evaluated for high-camber airfoil self-noise predictions. Wind tunnel installation effects have been incorporated properly into the LES.

Details

Aircraft Engineering and Aerospace Technology, vol. 90 no. 1
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 31 May 2011

Marie de Rochambeau, Mohamed Ichchou and Bernard Troclet

The purpose of this paper is to extend statistical energy analysis (SEA)‐like modeling to fluid‐structure coupled systems.

Abstract

Purpose

The purpose of this paper is to extend statistical energy analysis (SEA)‐like modeling to fluid‐structure coupled systems.

Design/methodology/approach

An equivalent approach of aerodynamic loads is applied to a SEA‐like modeling of a panel‐cavity coupled system with rain‐on‐the‐roof excitation. Two aerodynamic excitations are presented: turbulent boundary layer (TBL) and diffuse field excitation. The energetic description of the coupled system is studied with both aerodynamic excitations, taking in account the coincidence effects. In order to extent the approach to more general systems, some parameters of the coupled system are also modified and the accuracy of the coupled system modeling is investigated.

Findings

The boundary conditions of the panel and the coupling strength between the panel and the cavity have been modified. As it was expected, the accuracy of equivalent approach is shown to be independent of such modifications. The interest of such calculation is thus highlighted: modelings of systems and aerodynamic excitations are independent, and can be treated separately.

Originality/value

This result is interesting in the space industry, for launch vehicles are excited by different types of random excitations. Those excitations can be modeled by SEA‐like with low calculation time and memory and applied to a unique system modeling.

Details

Engineering Computations, vol. 28 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 11 October 2021

Guangyuan Huang, Ka Him Seid, Zhigang Yang and Randolph Chi Kin Leung

For flow around elongated bluff bodies, flow separations would occur over both leading and trailing edges. Interactions between these two separations can be established…

Abstract

Purpose

For flow around elongated bluff bodies, flow separations would occur over both leading and trailing edges. Interactions between these two separations can be established through acoustic perturbation. In this paper, the flow and the acoustic fields of a D-shaped bluff body (length-to-height ratio L/H = 3.64) are investigated at height-based Reynolds number Re = 23,000 by experimental and numerical methods. The purpose of this paper is to study the acoustic feedback in the interaction of these two separated flows.

Design/methodology/approach

The flow field is measured by particle image velocimetry, hotwire velocimetry and surface oil flow visualization. The acoustic field is modeled in two dimensions by direct aeroacoustic simulation, which solves the compressible Navier–Stokes equations. The simulation is validated against the experimental results.

Findings

Separations occur at both the leading and the trailing edges. The leading-edge separation point and the reattaching flow oscillate in accordance with the trailing-edge vortex shedding. Significant pressure waves are generated at the trailing edge by the vortex shedding rather than the leading-edge vortices. Pressure-based cross-correlation analysis is conducted to clarify the effect of the pressure waves on the leading-edge flow structures.

Practical implications

The understanding of interactions of separated flows over elongated bluff bodies helps to predict aerodynamic drag, structural vibration and noise in engineering applications, such as the aerodynamics of buildings, bridges and road vehicles.

Originality/value

This paper clarifies the influence of acoustic perturbations in the interaction of separated flows over a D-shaped bluff body. The contribution of the leading- and the trailing-edge vortex in generating acoustic perturbations is investigated as well.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 5 March 2018

Guo Zhong, Jun Huang and Mingxu Yi

The purpose of this paper is to reduce the acoustic noise of helicopter ducted tail rotor.

Abstract

Purpose

The purpose of this paper is to reduce the acoustic noise of helicopter ducted tail rotor.

Design/methodology/approach

To predict the noise accurately, a thin-body boundary element method (BEM)/Ffowcs Williams–Hawkings method is developed in this paper. It is a hybrid method combining the BEM with computational aeroacoustics and can be used efficiently to predict the propagation of sound wave in the duct.

Findings

Compared with the experimental results, the proposed method of acoustic noise is rather desirable.

Practical implications

Then several geometry parameters are modified to investigate the noise reduction of ducted tail rotor by using the numerical prediction method.

Originality/value

The aerodynamic and acoustic performance of different modification tasks is discussed. These results demonstrate the validity of design parameters modification of ducted tail rotor in acoustic noise reduction.

Details

Aircraft Engineering and Aerospace Technology, vol. 90 no. 2
Type: Research Article
ISSN: 1748-8842

Keywords

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Article
Publication date: 31 August 2021

Zbigniew Rarata

The purpose of this paper is to investigate airfoil’s tonal noise reduction mechanism when deploying surface irregularities, such as surface waviness by means of spatial…

Abstract

Purpose

The purpose of this paper is to investigate airfoil’s tonal noise reduction mechanism when deploying surface irregularities, such as surface waviness by means of spatial stability analyses.

Design/methodology/approach

Flow field calculations over smooth and wavy-surface NACA 0012 airfoils at 2° angle of attack and at Reynolds number of 200,000 are performed using the large eddy simulation (LES) approach. Three geometrical configurations are considered: a smooth NACA 0012 airfoil, wavy surface on the suction side (SS) and wavy surface on the pressure side (PS). The spatial stability analyses using the LES-generated flow fields are conducted and validated against the Orr-Sommerfeld stability analysis for the smooth airfoil configuration.

Findings

The spatial stability analyses show that inclusion of the wavy-type modification on the SS of the airfoil does not lead to altering of the acoustic feedback loop mechanism, with respect to the mechanism observed for the smooth airfoil configuration. In contrast, applying the surface modifications to the airfoil PS leads to a significant reduction of the amplification range of disturbances in the vicinity of the trailing edge for the frequency of the acoustic feedback loop mechanism.

Practical implications

The spatial analyses using, for example, LES-generated flow fields can be widely used to determine acoustic sources and associated distributions of amplifications for a wide range of applications in the aeroacoustics.

Originality/value

The spatial stability analysis approach based on flow fields computed a priori using the LES method has been introduced, validated and used to determine behaviour of the acoustic feedback loop when accurate reconstruction of geometry effects is required.

Details

Aircraft Engineering and Aerospace Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 21 March 2011

Jae S. Park, Sung N. Jung, Young H. You, Soo H. Park and Yung H. Yu

The purpose of this paper is to evaluate the prediction capability of comprehensive structural dynamics (CSD) analysis codes for the higher harmonic control aeroacoustic

Abstract

Purpose

The purpose of this paper is to evaluate the prediction capability of comprehensive structural dynamics (CSD) analysis codes for the higher harmonic control aeroacoustic rotor test (HART) II data.

Design/methodology/approach

A nonlinear flexible multibody dynamics analysis code DYMORE, as well as the comprehensive analytical model of rotorcraft aerodynamics and dynamics (CAMRAD) II, are used to perform the task. The predicted results on rotating free vibration analysis, airloads, blade elastic motions, and structural moments are correlated with the measured data for the baseline, minimum noise, and minimum vibration cases.

Findings

The DYMORE analysis results with a free wake model show a good performance in capturing blade vortex interaction peaks in the prediction of section normal forces but apparently with a phase shift problem. The high‐frequency behavior in the airloads signal does not affect much on the aeroelastic response and structural moments of the rotor.

Originality/value

The present approach uses two separate CSD codes to systematically validate the HART II data. The accuracy of each code on structural dynamic aspects of HART II rotor is assessed using a consistent set of inputs. The effects of blade tip deflections on the interaction of blades and their trailed vortices leading to a reduced noise emission are also investigated.

Details

Aircraft Engineering and Aerospace Technology, vol. 83 no. 2
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 6 July 2010

A. Arun Kumar, S.R. Viswamurthy and R. Ganguli

This paper aims to validate a comprehensive aeroelastic analysis for a helicopter rotor with the higher harmonic control aeroacoustic rotor test (HART‐II) wind tunnel test data.

Abstract

Purpose

This paper aims to validate a comprehensive aeroelastic analysis for a helicopter rotor with the higher harmonic control aeroacoustic rotor test (HART‐II) wind tunnel test data.

Design/methodology/approach

Aeroelastic analysis of helicopter rotor with elastic blades based on finite element method in space and time and capable of considering higher harmonic control inputs is carried out. Moderate deflection and coriolis nonlinearities are included in the analysis. The rotor aerodynamics are represented using free wake and unsteady aerodynamic models.

Findings

Good correlation between analysis and HART‐II wind tunnel test data is obtained for blade natural frequencies across a range of rotating speeds. The basic physics of the blade mode shapes are also well captured. In particular, the fundamental flap, lag and torsion modes compare very well. The blade response compares well with HART‐II result and other high‐fidelity aeroelastic code predictions for flap and torsion mode. For the lead‐lag response, the present analysis prediction is somewhat better than other aeroelastic analyses.

Research limitations/implications

Predicted blade response trend with higher harmonic pitch control agreed well with the wind tunnel test data, but usually contained a constant offset in the mean values of lead‐lag and elastic torsion response. Improvements in the modeling of the aerodynamic environment around the rotor can help reduce this gap between the experimental and numerical results.

Practical implications

Correlation of predicted aeroelastic response with wind tunnel test data is a vital step towards validating any helicopter aeroelastic analysis. Such efforts lend confidence in using the numerical analysis to understand the actual physical behavior of the helicopter system. Also, validated numerical analyses can take the place of time‐consuming and expensive wind tunnel tests during the initial stage of the design process.

Originality/value

While the basic physics appears to be well captured by the aeroelastic analysis, there is need for improvement in the aerodynamic modeling which appears to be the source of the gap between numerical predictions and HART‐II wind tunnel experiments.

Details

Aircraft Engineering and Aerospace Technology, vol. 82 no. 4
Type: Research Article
ISSN: 0002-2667

Keywords

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