Multi-scale approach for analyzing convective heat transfer flow in background-oriented Schlieren technique

Gannavarpu, Rajshekhar; Ambrosini, Dario

doi:10.1016/j.optlaseng.2018.07.002

Cited by 12 publications

(7 citation statements)

References 24 publications

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“…Further, we also observe that the peak phase value changes with the frame number indicating the dynamic nature of heat transfer. The connection between phase values and temperature gradient is described in [22,50].…”

Section: Resultsmentioning

confidence: 99%

Quantitative flow visualization by hidden grid background oriented schlieren

Ramaiah

Rubeis

Gannavarpu

et al. 2023

Optics and Lasers in Engineering

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Section: Resultsmentioning

confidence: 99%

Quantitative flow visualization by hidden grid background oriented schlieren

Ramaiah

Rubeis

Gannavarpu

et al. 2023

Optics and Lasers in Engineering

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“…Considering the potential of the BOS technique, throughout the years, this optical method has been used for studies within different applications, including the analysis of the shock wave propagation from explosions [40], underwater shock waves [41,42], heat transfer processes [43][44][45], air leakage [46], and flame-induced flow [47,48], among others [49][50][51][52][53][54]. Recently, the BOS measurement technique began to be used for density field quantification of the DBD flow induced by plasma actuators.…”

Section: Introductionmentioning

confidence: 99%

Development of a Background-Oriented Schlieren (BOS) System for Thermal Characterization of Flow Induced by Plasma Actuators

et al. 2023

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Cold climate regions have great potential for wind power generation. The available wind energy in these regions is about 10% higher than in other regions due to higher wind speeds and increased air density. However, these regions usually have favorable icing conditions that lead to ice accumulation on the wind turbine blades, which in turn increases the weight of the blades and disrupts local airflow, resulting in a reduction in wind turbine performance. Considering this problem, plasma actuators have been proposed as devices for simultaneous flow control and deicing. These devices transfer momentum to the local airflow, improving the aerodynamic performances of the turbine blades while producing significant thermal effects that can be used to prevent ice formation. Considering the potential application of plasma actuators for simultaneous flow control and deicing, it is very important to investigate the thermal effects induced by these devices. However, due to the significant electromagnetic interference generated by the operation of these devices, there is a lack of experimental techniques that can be used to analyze them. In the current work, a background-oriented Schlieren system was developed and is presented as a new experimental technique for the thermal characterization of the plasma-induced flow. For the first time, the induced flow temperatures are characterized for plasma actuators with different dielectric materials and different dielectric thicknesses. The results demonstrate that, due to the plasma discharge, the temperature of the plasma-induced flow increases with the increase of the applied voltage and may achieve temperatures five times higher than the room temperature, which proves the potential of plasma actuators for deicing applications. The results are presented and discussed with respect to the potential application of plasma actuators for simultaneous flow control and deicing of wind turbine blades.

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“…Compared to conventional Schlieren imagin and optical interferometry, the measurement system is quite simple: it consists of only a background, camera, and light source. BOS technique has been applied to various density fields, such as gas flows [6,7,8,9,10], shock waves [4,5,11,12], flames [13,14,15,16,17], and liquid-gas interfaces [18,19]. Furthermore, it has also been applied to various length scales, from micrometers [2,11,12,20] to meters [5,21].…”

Section: Introductionmentioning

confidence: 99%

Background oriented schlieren technique with fast Fourier demodulation for measuring large density-gradient fields of fluids

Shimazaki,

Ichihara,

Tagawa

2022

Preprint

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In order to measure the large density-gradient fields of fluids such as underwater shock waves, we employed a fast Fourier demodulation called Fast Checkerboard Demodulation (FCD) method in Background Oriented Schlieren (BOS) technique. BOS is a simple image-based measurement technique that detects the apparent displacement (local distortion) of a background image caused by the density gradient of the fluid in front of the background. The cross-correlation particle image velocimetry (PIV) method, which is commonly employed in the BOS technique for detecting the apparent displacement, uses a random-dot background, whereas FCD uses a periodic pattern as the background (e.g., checkerboard pattern, lattice grid pattern (grid scale)) to detect the apparent displacement as the phase change of the pattern in the Fourier space. In this study, we measured the apparent displacement, which is proportional to density gradient of fluid, of an underwater shock wave using FCD and PIV. The results showed that FCD can measure a displacement gradient of up to 2.5 times larger than that which PIV can measure. Furthermore, we systematically investigated the measurement limit of FCD-BOS by changing several parameters of the periodic patterns, such as the grid size. Also, we explored the related parameters in the Fourier space to understand the limitations. It is worth noting that FCD-BOS with lattice grid pattern (grid scale) can measure the apparent displacement as accurately as that with a custom-made pattern, indicating that large density-gradient fields of fluids can be measured using a simple setup with a commercially available (inexpensive) pattern.

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Multi-scale approach for analyzing convective heat transfer flow in background-oriented Schlieren technique

Cited by 12 publications

References 24 publications

Quantitative flow visualization by hidden grid background oriented schlieren

Quantitative flow visualization by hidden grid background oriented schlieren

Development of a Background-Oriented Schlieren (BOS) System for Thermal Characterization of Flow Induced by Plasma Actuators

Background oriented schlieren technique with fast Fourier demodulation for measuring large density-gradient fields of fluids

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