2020
DOI: 10.3390/app10186552
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Contactless Localization of Premature Laminar–Turbulent Flow Transitions on Wind Turbine Rotor Blades in Operation

Abstract: Thermographic flow visualization enables a noninvasive detection of the laminar–turbulent flow transition and allows a measurement of the impact of surface erosion and contamination due to insects, rain, dust, or hail by quantifying the amount of laminar flow reduction. The state-of-the-art image processing is designed to localize the natural flow transition as occurring on an undisturbed blade surface by use of a one-dimensional gradient evaluation. However, the occurrence of premature flow transitions leads … Show more

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Cited by 6 publications
(7 citation statements)
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References 27 publications
(29 reference statements)
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“…The validation of the algorithm for measured thermograms of wind turbine blades in operation follows in Section 4.3. Note that the results of the verification and the validation with the model-based algorithm (MBA) are compared with the state-of-the-art, gradient-based image processing algorithm (GBA) from [14].…”
Section: Resultsmentioning
confidence: 99%
See 2 more Smart Citations
“…The validation of the algorithm for measured thermograms of wind turbine blades in operation follows in Section 4.3. Note that the results of the verification and the validation with the model-based algorithm (MBA) are compared with the state-of-the-art, gradient-based image processing algorithm (GBA) from [14].…”
Section: Resultsmentioning
confidence: 99%
“…However, turbulence wedges were not detected reliably due to the low CNR between laminar and turbulent flow regions. Similarly, Gleichauf et al [14] used intensity gradients to also detect flow transitions in thermograms of a wind turbine in operation. Since chord-wise intensity gradients are not sufficient for the reliable detection of turbulence wedges, the thermogram was at first rotated to such a degree that the subsequently evaluated intensity gradient was perpendicular to the premature transition lines.…”
Section: State Of the Artmentioning
confidence: 99%
See 1 more Smart Citation
“…However for the PCA result (green line), the localization is able to locate the area between the two flow regimes. The remaining curvature form of the located flow transition might result from unsteady inflow conditions, transverse flow along the rotor blade or irregularities on the surface, resulting in premature flow transitions [8].…”
Section: Xlqsl[hovmentioning
confidence: 99%
“…In order to achieve this, different image processing methods have been proposed. The most frequently applied approach is to use either unprocessed raw images or the output of a simple image filtering such as averaging, and then to locate the maximum temperature gradient along the temperature profiles in the main flow direction [12,[18][19][20]. For a dynamically changing boundary layer flow, Wolf et al [21] used the computation of differential images to visualize the laminar-turbulent flow transition on a fast pitching airfoil.…”
Section: Introductionmentioning
confidence: 99%