scholarly journals Comparison of techniques for the estimation of flow parameters of fan inflow turbulence from noisy hot-wire data

2021 ◽  
Author(s):  
Luciano Caldas ◽  
Carolin A. Kissner ◽  
Maximilian Behn ◽  
Ulf Tapken ◽  
Robert Meyer
Keyword(s):  
Hot Wire ◽  
Flow Parameters ◽  
Inflow Turbulence ◽  
Comparison Of Techniques

Wake measurements of oscillating supercritical airfoil in compressible flow

2019 ◽  
Vol 43 (1) ◽  
pp. 112-121
Author(s):  
Behnaz Beheshti Boroumand ◽  
Mahmoud Mani
Keyword(s):  
Mach Number ◽  
Angle Of Attack ◽  
Time History ◽  
Mean Value ◽  
Hot Wire ◽  
Dynamic Tests ◽  
Flow Parameters ◽  
Free Stream Mach Number ◽  
Static And Dynamic Tests ◽  
Wake Characteristics

Boundary layer and wake behaviors are strongly affected by airfoil motion. Moreover, parameters like body oscillation frequency, oscillation type, Mach number, and angle of attack play main roles in wake characteristics. In this research, both static and dynamic tests were carried out in a tri-sonic wind tunnel to study wake profiles experimentally by hot wire anemometry. All data were recorded at a free stream Mach number of 0.4. Quarter-length and half-length of chord were also considered as downstream distances from the trailing edge in pitching motions of mean angle of attack of −0.4°. Frequencies of 3 Hz and 6 Hz with amplitude of 3° were chosen as oscillation parameters. Voltages at hot wire outputs were measured and analyzed qualitatively and statistically with root-mean-square, correlation, mean value distribution, time history, and frequency. Flow parameters were obtained by computational studies under similar experimental test conditions. The wake characteristics obtained from numerical and experimental methods were compared.

scholarly journals Comparison of Techniques for the Estimation of Flow Parameters of Fan Inflow Turbulence from Noisy Hot-Wire Data

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 372
Author(s):  
Luciano Caldas ◽  
Carolin Kissner ◽  
Maximilian Behn ◽  
Ulf Tapken ◽  
Robert Meyer
Keyword(s):  
Signal Processing ◽  
Parameter Estimation ◽  
High Speed ◽  
Window Size ◽  
Measured Data ◽  
Frequency Resolution ◽  
Hot Wire ◽  
Turbulence Parameter ◽  
Estimation Techniques ◽  
Inflow Turbulence

Turbulence parameters, in particular integral length scale (ILS) and turbulence intensity (Tu), are key input parameters for various applications in aerodynamics and aeroacoustics. The estimation of these parameters is typically performed using data obtained via hot-wire measurements. On the one hand, hot-wire measurements are affected by external disturbances resulting in increased measurement noise. On the other hand, commonly applied turbulence parameter estimators lack in robustness. If not addressed correctly, both issues may impede the accuracy of the turbulence parameter estimation. In this article, a procedure consisting of several signal processing steps is presented to filter non-turbulence related disturbances from the unsteady velocity data. The signal processing techniques comprise time- and frequency-domain approaches. For the turbulence parameter estimation, two different models of the turbulence spectra—the von Kármán model and the Bullen model—are fitted to match the spectrum of the measured data. The results of several parameter estimation techniques are compared. Computational Fluid Dynamics (CFD) data are used to validate the estimation techniques and also to assess the influence of the variation in window size on the estimated parameters. Additionally, hot-wire data from a high-speed fan rig are analyzed. ILS and Tu are assessed at several radial positions for two fan speeds. It is found that most techniques yield similar values for ILS and Tu. The comparison of the fitted spectra with the spectra of the measured data shows a good agreement in most cases provided that a sufficiently fine frequency resolution is applied. The ratio of ILS and Tu of the velocity components in longitudinal and transverse direction allows the assessment of flow-isotropy. Results indicate that the turbulence is anisotropic for the investigated flow fields.

The Control Method with Energy Saving of the Inflow Turbulence for Router Cooling Fan

2014 ◽  
Vol 886 ◽  
pp. 394-397 ◽  
Author(s):  
Ying Bo Xu ◽  
Xiao Dong Li
Keyword(s):  
Flow Field ◽  
Energy Saving ◽  
Turbulence Intensity ◽  
Control Method ◽  
Hot Wire ◽  
Mean Flow ◽  
Cooling Fan ◽  
Inflow Turbulence ◽  
The Mean

In this paper, the characteristics of the inflow turbulence intensity of a router cooling fan are studied experimentally. Screens with different parameters are designed to control the inflow turbulence intensity. The flow field is measured by hot-wire anemometer. The results show that the inflow turbulence intensity is closely connected with the parameters of the control screens. The inflow turbulence intensity can be significantly reduced when the screen with small meshes is used, while the mean flow is barely affected by the screen.

The Effect of Flow Coefficient on the Self Noise Generated by a Ducted Rotor

2008 ◽  
Author(s):  
David B. Stephens ◽  
Scott C. Morris ◽  
William K. Blake
Keyword(s):  
Flow Field ◽  
The Self ◽  
Flow Coefficient ◽  
Hot Wire ◽  
Fluid Forces ◽  
Inflow Turbulence ◽  
Order Change ◽  
Ducted Rotor ◽  
Unsteady Fluid ◽  
Rigid Surfaces

Sound generation in low Mach number turbomachines is typically dominated by unsteady fluid forces on rigid surfaces. As a result, the radiated sound is closely related to the unsteady flow field. The present study focused on the self noise that is generated by a ducted rotor separate from the effect of noise due to inflow turbulence. The flow rate through the rotor was independently varied in order change the mean lift on the blades. Measurements of the flow field around a ducted rotor were found to provide insight to the various mechanisms of sound that are present at different mean loading conditions. At lower flow rates the blades were partially stalled, resulting in significantly increased noise levels. The measurements included rotor wake measurements using hot-wire anemometry and far field sound. A simple model to predict the radiated self noise based on the hot-wire measurements is presented.

Tip Clearance Flow in a Compressor Rotor Passage at Design and Off-Design Conditions

1984 ◽  
Vol 106 (3) ◽  
pp. 570-577 ◽  
Author(s):  
B. Lakshminarayana ◽  
A. Pandya
Keyword(s):  
Tip Clearance ◽  
Velocity Data ◽  
Hot Wire ◽  
Pressure Data ◽  
Ensemble Averaging ◽  
Blade Loading ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Flow Parameters ◽  
Clearance Flow

The flow field in the tip clearance region of a compressor rotor at an off-design condition is reported in this paper. The earlier data at the design condition have also been reinterpreted and correlated with the blade and the flow parameters. The measurements inside the rotor tip region are acquired using a miniature hot-wire sensor of “V” configuration. The instantaneous velocity data are analyzed by the ensemble-averaging technique to derive the blade-to-blade velocity field at various axial and radial locations between the rotor tip and the casing. The flow and the blade pressure data at the design condition are compared with the data at the off-design condition (lower blade loading). In addition to a reduction in the leakage velocities, its chordwise variation is also altered substantially at the lower blade loading.

scholarly journals Development of a Curled Wake of a Yawed Wind Turbine under Turbulent and Sheared Inflow

2021 ◽  
Author(s):  
Paul Hulsman ◽  
Martin Wosnik ◽  
Vlaho Petrović ◽  
Michael Hölling ◽  
Martin Kühn
Keyword(s):  
Energy Dissipation ◽  
Wind Turbine ◽  
Dissipation Rate ◽  
Vortex Pair ◽  
Turbine Rotor ◽  
Energy Dissipation Rate ◽  
Hot Wire ◽  
Inflow Condition ◽  
Inflow Turbulence ◽  
Inflow Conditions

Abstract. A potential technique to reduce the negative wake impact is to redirect it away from a downstream turbine by yawing the upstream turbine. The present research investigated the wake behaviour for three yaw angles [−30°, 0°, 30°] at different inflow turbulence levels and shear profiles under controlled conditions. Experiments were conducted using a model wind turbine with 0.6 m diameter (D) in a wind tunnel. A short-range dual-Doppler Lidar WindScanner facilitated mapping the wake with a high spatial and temporal resolution in vertical, cross-stream planes at different downstream locations and in a horizontal plane at hub height. This versatile equipment enabled the fast measurements at multiple locations in comparison to the well known hot-wire measurements. The flow structures and the energy dissipation rate of the wake were measured from 1D up to 10D, and for one inflow case up to 16D, downstream of the turbine rotor. A strong dependency of the wake characteristics on both the yaw angle and the inflow conditions was observed. In addition, the curled wake that develops under yaw misalignment due to the counter-rotating vortex pair was more pronounced with a boundary layer (sheared) inflow condition than for uniform inflow with different turbulence levels. Furthermore, the lidar velocity data and the energy dissipation rate compared favourably with hot-wire data from previous experiments with a similar inflow condition and wind turbine model in the same facility, lending credibility to the measurement technique and methodology used here. The measurement campaign provided a deeper understanding of the development of the wake at different inflow conditions, which will advance the process to improve existing wake models.

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