602 Discrete Frequency Noise Generated from Blade Tip Vortex Flow of a Propeller Fan

2013 ◽  
Vol 2013.66 (0) ◽  
pp. 165-166
Author(s):  
Ikki Torise ◽  
Soichi SASAKI ◽  
Hidechito HAYASHI ◽  
Hiroaki MURAKAMI
Keyword(s):  
Vortex Flow ◽  
Tip Vortex ◽  
Frequency Noise ◽  
Discrete Frequency ◽  
Blade Tip

Application of a RANS-Informed Analytical Model for Fast Noise Prediction of Contra Rotating Open Rotors

2017 ◽  
Author(s):  
Damiano Tormen ◽  
Pietro Giannattasio ◽  
Alessandro Zanon ◽  
Helmut Kühnelt ◽  
Michele De Gennaro
Keyword(s):  
Analytical Model ◽  
Vortex Flow ◽  
Domain Model ◽  
Tip Vortex ◽  
Acoustic Measurements ◽  
Open Rotor ◽  
Noise Measurements ◽  
Blade Tip ◽  
Fast Prediction ◽  
Analytical Frequency

The present work focuses on the fast prediction of the interaction noise (IN) components of a Contra Rotating Open Rotor (CROR) engine at take-off. The flow field past the CROR is computed using a steady RANS approach coupled with the concept of mixing plane between the rotors to remove the flow unsteadiness due to the propeller interaction. The effects of such interaction are then recovered applying the analytical model of Jaron et al. (2014), balanced with data extracted from the RANS solution, to extrapolate the information about the wake of the front rotor and the potential flow fields through the mixing plane. This RANS-informed approximation allows recovering the unsteadiness of the flow-blades interaction in terms of unsteady blade response. The tonal noise at the blade passing frequency and the interaction noise are then estimated using the analytical frequency domain model proposed by Hanson (1985). The present method for the fast prediction of CROR noise has been validated by comparison with the results of URANS simulations and noise measurements. CROR geometry UDF F7/A7 with both 8 × 8 and 11 × 9 blade counts has been considered. The flow velocity profiles extrapolated through the mixing plane agree well with the URANS results, except in the vicinity of the blade tip, where the analytical extrapolation method is not able to deal properly with the strongly 3D tip vortex flow. The comparison of the predicted interaction noise with acoustic measurements shows that the present fast RANS-informed approach is capable of estimating the directivity of the CROR noise with reasonable accuracy.

Investigation of Helicopter Rotor-Blade-Tip-Vortex Alleviation Using a Slotted Tip

AIAA Journal ◽  
2004 ◽  
Vol 42 (3) ◽  
pp. 524-535 ◽  
Author(s):  
Yong Oun Han ◽  
J. Gordon Leishman
Keyword(s):  
Rotor Blade ◽  
Tip Vortex ◽  
Helicopter Rotor ◽  
Helicopter Rotor Blade ◽  
Blade Tip

Investigation of the Blade Tip Clearance Effects on Performance and Stability of a Mixed-Flow Pump: High Speed Camera Recordings of the Flow Structures, Local Measurements and Numerical Simulation

2015 ◽  
Author(s):  
Alberto Serena ◽  
Lars E. Bakken
Keyword(s):  
High Speed ◽  
Detailed Comparison ◽  
Performance Comparison ◽  
Tip Clearance ◽  
Tip Vortex ◽  
High Speed Camera ◽  
Tip Leakage Flow ◽  
Quality Video ◽  
Local Measurements ◽  
Blade Tip

The tip leakage flow affects turbomachines performance generating losses and reducing the effective blading; in addition, unsteady phenomena arise, negatively influencing the machine stability. In this paper, an overview of the existing models is presented. Local measurements of the pressure pulsations, visual flow observations and high quality video recordings from a high speed camera are performed in a novel pump laboratory, which provides the desired visualization of the rotating channels, and allows to study the fluctuating and intermittent nature of this phenomenon, and detect any asymmetry among the channels. A detailed comparison of the vortex tip structure for various tip clearances and with a whole set of numerical simulations finally completes the analysis. The three main focus areas are: tip vortex location, structure and evolution, performance comparison between shrouded and open impeller, at different tip clearance sizes, and study of the rotating instabilities.

scholarly journals Numerical Investigation of Tip-Vortex Cavitation Noise of an Elliptic Wing Using Coupled Eulerian-Lagrangian Approaches

2020 ◽  
Vol 10 (17) ◽  
pp. 5897 ◽  
Author(s):  
Garam Ku ◽  
Cheolung Cheong ◽  
Hanshin Seol
Keyword(s):  
Flow Field ◽  
Numerical Method ◽  
Vortex Flow ◽  
Acoustic Pressure ◽  
Tip Vortex ◽  
Experimental Result ◽  
Cavitation Noise ◽  
Navier Stokes Equation ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception

In this study, a numerical methodology is developed to investigate the tip-vortex cavitation of NACA16-020 wings and their flow noise. The numerical method consists of a sequential one-way coupled application of Eulerian and Lagrangian approaches. First, the Eulerian method based on Reynolds-averaged Navier–Stokes equation is applied to predict the single-phase flow field around the wing, with particular emphasis on capturing high-resolution tip-vortex flow structures. Subsequently, the tip-vortex flow field is regenerated by applying the Scully vortex model. Secondly, the Lagrangian approach is applied to predict the tip-vortex cavitation inception and noise of the wing. The initial nuclei are distributed upstream of the wing. The subsequent time-varying size and position of each nucleus are traced by solving spherically symmetric bubble dynamics equations for the nuclei in combination with the flow field predicted from the Eulerian approach. The acoustic pressure at the observer position is computed by modelling each bubble as a point source. The numerical results of the acoustic pressure spectrum are best matched to the measured results when the nuclei number density of freshwater is used. Finally, the current numerical method is applied to the flows of various cavitation numbers. The results reveal that the cavitation inception determined by the predicted acoustic pressure spectrum well matched the experimental result.

Numerical Experiments for Flow Around a Ducted Tip Hydrofoil

2002 ◽  
Author(s):  
Hildur Ingvarsdo´ttir ◽  
Carl Ollivier-Gooch ◽  
Sheldon I. Green
Keyword(s):  
Turbulence Model ◽  
Vortex Core ◽  
Vortex Flow ◽  
Computational Study ◽  
Near Field ◽  
Vortex Formation ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Computational Studies ◽  
Tip Vortices

The performance and cavitation characteristics of marine propellers and hydrofoils are strongly affected by tip vortex behavior. A number of previous computational studies have been done on tip vortices, both in aerodynamic and marine applications. The focus, however, has primarily been on validating methods for prediction and advancing the understanding of tip-vortex formation in general, rather than showing effects of tip modifications on tip vortices. Studies of the most relevance to the current work include computational studies by Dacles-Mariani et al. (1995) and Hsiao and Pauley (1998, 1999). Daeles-Mariani et al. carried out interactively a computational and experimental study of the wingtip vortex in the near field using a full Navier-Stokes simulation, accompanied with the Baldwin-Barth turbulence model. Although they showed improvement over numerical results obtained by previous researchers, the tip vortex strength was underpredicted. Hsiao and Pauley (1998) studied the steady-state tip vortex flow over a finite-span hydrofoil, also using the Baldwin-Barth turbulence model. They were able to achieve good agreement in pressure distribution and oil flow pattern with experimental data and accurately predict vertical and axial velocities of the tip vortex core within the near-field region. Far downstream, however, the computed flow field was overly diffused within the tip vortex core. Hsiao and Pauley (1999) also carried out a computational study of the tip vortex flow generated by a marine propeller. The general characteristics of the flow were well predicted but the vortex core was again overly diffused.

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