Boundary layer diagnostics by means of an infrared scanning radiometer

Luca, Luigi De; Carlomagno, Giovanni Maria; Buresti, Guido

doi:10.1007/bf00187411

Cited by 57 publications

(22 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…de Luca et al (1990b) study the flow field over a Göttingen 797 airfoil (with a 180 mm chord) at several angles of attack. The wing model is made of a glass-epoxy skin (& 3 mm thick) over polyurethane foam.…”

Section: Airfoils Transition/separationmentioning

confidence: 99%

Infrared thermography for convective heat transfer measurements

2010

View full text Add to dashboard Cite

This paper deals with the evolution of infrared (IR) thermography into a powerful optical tool that can be used in complex fluid flows to either evaluate wall convective heat fluxes or investigate the surface flow field behavior. Measurement of convective heat fluxes must be performed by means of a thermal sensor, where temperatures have to be measured with proper transducers. By correctly choosing the thermal sensor, IR thermography can be successfully exploited to resolve convective heat flux distributions with both steady and transient techniques. When comparing it to standard transducers, the IR camera appears very valuable because it is non-intrusive, it has a high sensitivity (down to 20 mK), it has a low response time (down to 20 ls), it is fully two dimensional (from 80 k up to 1 M pixels, at 50 Hz) and, therefore, it allows for better evaluation of errors due to tangential conduction within the sensor. This paper analyses the capability of IR thermography to perform convective heat transfer measurements and surface visualizations in complex fluid flows. In particular, it includes the following: the necessary radiation theory background, a review of the main IR camera features, a description of the pertinent heat flux sensors, an analysis of the IR image processing methods and a report on some applications to complex fluid flows, ranging from natural convection to hypersonic regime.

show abstract

Section: Airfoils Transition/separationmentioning

confidence: 99%

Infrared thermography for convective heat transfer measurements

2010

View full text Add to dashboard Cite

show abstract

“…The local surface temperature of the rotor blade depends on the local flow-related heat transfer coefficient. [20,21]. This results in a thermal fingerprint that correlates with the friction coefficient of the different flow areas of the boundary layer.…”

Section: Thermographymentioning

confidence: 97%

Investigation of Laminar–Turbulent Transition on a Rotating Wind-Turbine Blade of Multimegawatt Class with Thermography and Microphone Array

et al. 2019

View full text Add to dashboard Cite

Knowledge about laminar–turbulent transition on operating multi megawatt wind turbine (WT) blades needs sophisticated equipment like hot films or microphone arrays. Contrarily, thermographic pictures can easily be taken from the ground, and temperature differences indicate different states of the boundary layer. Accuracy, however, is still an open question, so that an aerodynamic glove, known from experimental research on airplanes, was used to classify the boundary-layer state of a 2 megawatt WT blade operating in the northern part of Schleswig-Holstein, Germany. State-of-the-art equipment for measuring static surface pressure was used for monitoring lift distribution. To distinguish the laminar and turbulent parts of the boundary layer (suction side only), 48 microphones were applied together with ground-based thermographic cameras from two teams. Additionally, an optical camera mounted on the hub was used to survey vibrations. During start-up (SU) (from 0 to 9 rpm), extended but irregularly shaped regions of a laminar-boundary layer were observed that had the same extension measured both with microphones and thermography. When an approximately constant rotor rotation (9 rpm corresponding to approximately 6 m/s wind speed) was achieved, flow transition was visible at the expected position of 40% chord length on the rotor blade, which was fouled with dense turbulent wedges, and an almost complete turbulent state on the glove was detected. In all observations, quantitative determination of flow-transition positions from thermography and microphones agreed well within their accuracy of less than 1%.

show abstract

“…After thermal excitation, is constant and can be determined by the following expression where 1 Δt is the frame rate of the camera and m is the picture index, while the logarithm was approximated by its series expansion. For subsonic air flows with Prandtl number Pr ≈ 1, the Reynolds analogy factor is approximately equal to unity and constant (Incropera and De Witt 1985;Luca et al 1990). c f denotes the coefficient of friction while St is the Stanton number.…”

Section: Theory and Measurement Data Analysismentioning

confidence: 99%

Temperature decline thermography for laminar–turbulent transition detection in aerodynamics

et al. 2017

View full text Add to dashboard Cite

a post-processing method was developed and qualified to determine a quantity proportional to the heat transfer coefficient into the flow. By plotting this quantity for each pixel of the surface, a qualitative, two-dimensional heat transfer map was obtained. The results clearly depicted the areas of onset and end of transition over the full span of the model and agreed with the expected behavior based on the respective flow condition. To validate the approach, surface hotfilm measurements were conducted simultaneously on the same NACA profile. Both techniques showed excellent agreement. The temperature decline method allows to visualize laminarturbulent transitions on static or moving parts and can be applied on a very broad range of scales-from tiny airfoils up to large airplane wings.

show abstract

Boundary layer diagnostics by means of an infrared scanning radiometer

Cited by 57 publications

References 11 publications

Infrared thermography for convective heat transfer measurements

Infrared thermography for convective heat transfer measurements

Investigation of Laminar–Turbulent Transition on a Rotating Wind-Turbine Blade of Multimegawatt Class with Thermography and Microphone Array

Temperature decline thermography for laminar–turbulent transition detection in aerodynamics

Contact Info

Product

Resources

About