scholarly journals Turbine Broadband Noise Predictions Using Linearised Frequency Domain Navier-Stokes Solvers

2021 ◽  
Vol 6 (4) ◽  
pp. 42
Author(s):  
Ricardo Blázquez-Navarro ◽  
Roque Corral
Keyword(s):  
Frequency Domain ◽  
Sound Pressure ◽  
State Of The Art ◽  
Broadband Noise ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Frequency Range ◽  
Low Pressure Turbine ◽  
The Third ◽  
Blade Thickness

A linear frequency domain Navier-Stokes solver is used to retain the influence of turning, thickness, and main geometric parameters on turbine broadband noise. The methodology has been applied to predict the broadband interaction noise produced by a representative low-speed low-pressure turbine section. The differences in the spectra with respect to those yielded by state-of-the-art flat plate based methodologies are up to 6 dB. The differences are caused by multiple effects that semi-analytical methodologies do not account for. The most important are blade thickness and turning, which have been studied separately to quantify their impact on the broadband noise footprint. The influence of changing the turbine operating conditions has been discussed as well. The outlet sound pressure level scales with the third and second power of the inlet and outlet Mach number, respectively, for constant turbulence intensity, within most of the frequency range considered.

scholarly journals ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction—Part I—Influence of the RANS Simulation

Acoustics ◽  
2020 ◽  
Vol 2 (3) ◽  
pp. 539-578
Author(s):  
Carolin Kissner ◽  
Sébastien Guérin ◽  
Pascal Seeler ◽  
Mattias Billson ◽  
Paruchuri Chaitanya ◽  
...  
Keyword(s):  
Turbulence Model ◽  
Analytical Methods ◽  
Companion Paper ◽  
Broadband Noise ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Data Set ◽  
The Past ◽  
Flow Turbulence ◽  
Diverse Data

A benchmark of Reynolds-Averaged Navier-Stokes (RANS)-informed analytical methods, which are attractive for predicting fan broadband noise, was conducted within the framework of the European project TurboNoiseBB. This paper discusses the first part of the benchmark, which investigates the influence of the RANS inputs. Its companion paper focuses on the influence of the applied acoustic models on predicted fan broadband noise levels. While similar benchmarking activities were conducted in the past, this benchmark is unique due to its large and diverse data set involving members from more than ten institutions. In this work, the authors analyze RANS solutions performed at approach conditions for the ACAT1 fan. The RANS solutions were obtained using different CFD codes, mesh resolutions, and computational settings. The flow, turbulence, and resulting fan broadband noise predictions are analyzed to pinpoint critical influencing parameters related to the RANS inputs. Experimental data are used for comparison. It is shown that when turbomachinery experts perform RANS simulations using the same geometry and the same operating conditions, the most crucial choices in terms of predicted fan broadband noise are the type of turbulence model and applied turbulence model extensions. Chosen mesh resolutions, CFD solvers, and other computational settings are less critical.

Quantification of the Influence of Unsteady Aerodynamic Loading on the Damping Characteristics of Airfoils Oscillating at Low Reduced Frequency—Part II: Numerical Verification

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Almudena Vega ◽  
Roque Corral
Keyword(s):  
Unsteady Aerodynamics ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Navier Stokes ◽  
Influence Coefficient ◽  
Numerical Verification ◽  
Low Pressure Turbine ◽  
Reduced Frequency ◽  
Unsteady Loading ◽  
Loading Parameter

This paper numerically investigates the correlation between the so-called unsteady loading parameter (ULP), derived in Part I of the corresponding paper, and the unsteady aerodynamics of oscillating airfoils at low reduced frequency with special emphasis on the work-per-cycle curves. Simulations using a frequency-domain linearized Navier–Stokes solver have been carried out on rows of a low-pressure turbine airfoil section, the NACA65 section, and a flat plate, to show the correlation between the actual value of the ULP and the flutter characteristics, for different airfoils, operating conditions, and mode shapes. Both the traveling wave and influence coefficient formulations of the problem are used in combination to increase the understanding of the ULP influence in different aspects of the unsteady flow field. It is concluded that, for a blade vibrating in a prescribed motion at design conditions, the ULP can quantitatively predict the effect of unsteady loading variations due to changes in both the incidence and the mode shape on the work-per-cycle curves. It is also proved that the unsteady loading parameter can be used to qualitatively compare the flutter characteristics of different airfoils.

The Low Reduced Frequency Limit of Vibrating Airfoils: Part IIIB — Numerical Quantification and Influence of Unsteady Loading

2016 ◽  
Author(s):  
Almudena Vega ◽  
Roque Corral
Keyword(s):  
Unsteady Aerodynamics ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Navier Stokes ◽  
Influence Coefficient ◽  
Low Pressure Turbine ◽  
Reduced Frequency ◽  
Frequency Regime ◽  
Unsteady Loading ◽  
Loading Parameter

This paper studies the unsteady aerodynamics of vibrating airfoils in the low reduced frequency regime with special emphasis on its impact on the work per cycle curves. Simulations using a frequency domain linearized Navier-Stokes solver have been carried out on rows of a low-pressure turbine airfoil section, the NACA65 section and a flat plate, to show the correlation between the actual value of the unsteady loading parameter (ULP), theoretically derived in Part IIIa, and the flutter characteristics, for different airfoils, operating conditions and mode-shapes. Both, the traveling-wave and influence coefficient formulations of the problem are used in combination to increase the understanding of the ULP influence in different aspects of the unsteady flowfield. It is concluded that, for a blade vibrating in a prescribed motion at design conditions, the ULP can quantitatively predict the effect of loading variations due to changes in the incidence, and also in the mode shape. It is also proved that the unsteady loading parameter can be used to compare the flutter characteristics of different airfoils.

A frequency domain blind identification method for operational modal analysis using a limited number of sensors

2020 ◽  
Vol 26 (17-18) ◽  
pp. 1383-1398
Author(s):  
Xinhui Li ◽  
Jerome Antoni ◽  
Michael J Brennan ◽  
Tiejun Yang ◽  
Zhigang Liu
Keyword(s):  
Modal Analysis ◽  
Frequency Domain ◽  
Blind Source Separation ◽  
Source Separation ◽  
Operating Conditions ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Frequency Range ◽  
Vibration Data ◽  
Spatial Aliasing

Operational modal analysis is an experimental modal analysis approach, which uses vibration data collected when the structure is under operating conditions. Amongst the methods for operational modal analysis, blind source separation–based methods have been shown to be efficient and powerful. The existing blind source separation modal identification methods, however, require the number of sensors to be at least equal to the number of modes in the frequency range of interest to avoid spatial aliasing. In this article, a frequency domain algorithm that overcomes this problem is proposed, which is based on the joint diagonalization of a set of weighted covariance matrices. In the proposed approach, the frequency range of interest is partitioned into several frequency ranges in which the number of active modes in each band is less than the number of sensors. Numerical simulations and an experimental example demonstrate the efficacy of the method.

Health Informatics Education in the Third World

1989 ◽  
Vol 28 (04) ◽  
pp. 270-272 ◽  
Author(s):  
O. Rienhoff
Keyword(s):  
Developing Countries ◽  
Health Informatics ◽  
Third World ◽  
State Of The Art ◽  
The State ◽  
Collaboration Network ◽  
Educational Tools ◽  
The Third ◽  
The Third World

Abstract:The state of the art is summarized showing many efforts but only few results which can serve as demonstration examples for developing countries. Education in health informatics in developing countries is still mainly dealing with the type of health informatics known from the industrialized world. Educational tools or curricula geared to the matter of development are rarely to be found. Some WHO activities suggest that it is time for a collaboration network to derive tools and curricula within the next decade.

The influence of external conditions on sound pressure in the pistonphone at the infrasound frequency range

2020 ◽  
pp. 67-72
Author(s):  
A. V. Konkov ◽  
D. V. Golovin
Keyword(s):  
Environmental Conditions ◽  
Sound Pressure ◽  
Primary Method ◽  
Frequency Range ◽  
External Conditions ◽  
Numerical Estimations

The influence of environmental conditions on a sound pressure reproduced by the primary method in the measuring chambers of the Pistonphone in the frequency range from 1 mHz to 250 Hz is estimated. Numerical estimations of influence of environmental conditions on sound pressure in pistonphone measuring chambers are given and special requirements to system of maintenance of required external conditions are specified.

Characterisation of the Humming-Type Noise and Vibration of the Automotive HVAC System

2019 ◽  
Vol 16 (2) ◽  
pp. 6634-6648
Author(s):  
A. Z. A. Mazlan ◽  
M. H. A. Satar ◽  
M. H. Hamdan ◽  
M. S. Md. Isa ◽  
S. Man ◽  
...  
Keyword(s):  
Vibration Characteristics ◽  
Operating Conditions ◽  
Hvac System ◽  
Frequency Range ◽  
Noise And Vibration ◽  
Power Steering ◽  
Pump Compressor

The automotive heating and ventilating air condition (HVAC) system, when vibrating, can generate various types of noises such as humming, hissing, clicking and air-rushes. These noises can be characterised to determine their root causes. In this study, the humming-type noise is taken into consideration whereby the noise and vibration characteristics are measured from various HVAC components such as power steering pump, compressor and air conditional pipe. Four types of measurement sensors were used in this study - tachometer for rpm tracking; accelerometer for the vibration microphone for the noise; and sound camera for the visualization measurement. Two types of operating conditions were taken into consideration - they were “idle” (850 rpm) and “running” (850-1400 rpm) conditions. A constant blower speed was applied for both conditions. The result shows that the humming noises can be determined at the frequency range of 300-350 Hz and 150-250 Hz for both idle and running conditions, respectively. The vibration of the power steering pump shows the worst acceleration of 1.8 m/s2 at the frequency range of 150-250 Hz, compared to the compressor and air conditional pipe. This result was validated with the 3D colour order and sound camera analyses, in which the humming noise colour mapping shows dominance in this frequency range.  

A Multiple Harmonic Open-Loop Controller for Hydro/Aerodynamic Force Measurements in Rotating Machinery Using Magnetic Bearings

2002 ◽  
Vol 124 (4) ◽  
pp. 827-834 ◽  
Author(s):  
D. O. Baun ◽  
E. H. Maslen ◽  
C. R. Knospe ◽  
R. D. Flack
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Open Loop ◽  
Rotating Machinery ◽  
Operating Conditions ◽  
Rotor Vibration ◽  
Aerodynamic Forces ◽  
Analog Input ◽  
Input And Output ◽  
The Time Domain

Inherent in the construction of many experimental apparatus designed to measure the hydro/aerodynamic forces of rotating machinery are features that contribute undesirable parasitic forces to the measured or test forces. Typically, these parasitic forces are due to seals, drive couplings, and hydraulic and/or inertial unbalance. To obtain accurate and sensitive measurement of the hydro/aerodynamic forces in these situations, it is necessary to subtract the parasitic forces from the test forces. In general, both the test forces and the parasitic forces will be dependent on the system operating conditions including the specific motion of the rotor. Therefore, to properly remove the parasitic forces the vibration orbits and operating conditions must be the same in tests for determining the hydro/aerodynamic forces and tests for determining the parasitic forces. This, in turn, necessitates a means by which the test rotor’s motion can be accurately controlled to an arbitrarily defined trajectory. Here in, an interrupt-driven multiple harmonic open-loop controller was developed and implemented on a laboratory centrifugal pump rotor supported in magnetic bearings (active load cells) for this purpose. This allowed the simultaneous control of subharmonic, synchronous, and superharmonic rotor vibration frequencies with each frequency independently forced to some user defined orbital path. The open-loop controller was implemented on a standard PC using commercially available analog input and output cards. All analog input and output functions, transformation of the position signals from the time domain to the frequency domain, and transformation of the open-loop control signals from the frequency domain to the time domain were performed in an interrupt service routine. Rotor vibration was attenuated to the noise floor, vibration amplitude ≈0.2 μm, or forced to a user specified orbital trajectory. Between the whirl frequencies of 14 and 2 times running speed, the orbit semi-major and semi-minor axis magnitudes were controlled to within 0.5% of the requested axis magnitudes. The ellipse angles and amplitude phase angles of the imposed orbits were within 0.3 deg and 1.0 deg, respectively, of their requested counterparts.

A State-of-the-art Elliptic Curve Cryptographic Processor Operating in the Frequency Domain

2007 ◽  
Vol 12 (4) ◽  
pp. 259-270 ◽  
Author(s):  
Selçuk Baktır ◽  
Sandeep Kumar ◽  
Christof Paar ◽  
Berk Sunar
Keyword(s):  
Elliptic Curve ◽  
Frequency Domain ◽  
State Of The Art

Numerical Investigation of the Solidity Effect on Linear Compressor Cascades

2014 ◽  
Author(s):  
J. Sans ◽  
M. Resmini ◽  
J.-F. Brouckaert ◽  
S. Hiernaux
Keyword(s):  
Numerical Investigation ◽  
State Of The Art ◽  
Leading Edge ◽  
Operating Conditions ◽  
Compressor Cascade ◽  
Minimum Loss ◽  
Low Speed ◽  
High Mach ◽  
The Stability ◽  
The Impact

Solidity in compressors is defined as the ratio of the aerodynamic chord over the peripheral distance between two adjacent blades, the pitch. This parameter is simply the inverse of the pitch-to-chord ratio generally used in turbines. Solidity must be selected at the earliest design phase, i.e. at the level of the meridional design and represents a crucial step in the whole design process. Most of the existing studies on this topic rely on low-speed compressor cascade correlations from Carter or Lieblein. The aim of this work is to update those correlations for state-of-the-art controlled diffusion blades, and extend their application to high Mach number flow regimes more typical of modern compressors. Another objective is also to improve the physical understanding of the solidity effect on compressor performance and stability. A numerical investigation has been performed using the commercial software FINE/Turbo. Two different blade profiles were selected and investigated in the compressible flow regime as an extension to the low-speed data on which the correlations are based. The first cascade uses a standard double circular arc profile, extensively referenced in the literature, while the second configuration uses a state-of-the-art CDB, representative of low pressure compressor stator mid-span profile. Both profiles have been designed with the same inlet and outlet metal angles and the same maximum thickness but the camber and thickness distributions, the stagger angle and the leading edge geometry of the CDB have been optimized. The determination of minimum loss, optimum incidence and deviation is addressed and compared with existing correlations for both configurations and various Mach numbers that have been selected in order to match typical booster stall and choke operating conditions. The emphasis is set on the minimum loss performance at mid-span. The impact of the solidity on the operating range and the stability of the cascade are also studied.

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