Natural convection flows due to evaporation of heavier-than-air fluids: Flow direction and validity of using similarity of temperature and vapor density fields

Vinnichenko, Nikolay A.; Pushtaev, Alexey V.; Plaksina, Yulia Yu.; Uvarov, A. V.

doi:10.1016/j.expthermflusci.2019.04.019

Cited by 8 publications

(7 citation statements)

References 32 publications

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“…Here, n is an index whose value may depend upon some non-dimensional number calculated for the air-vapor mixture. It may be noted that for n = 1, and κ = 1 the temperature and concentration fields are self-similar as in [10], which is valid for a case where the Lewis number is unity (Le = 1). So, n is an empirical constant which captures the effect of the degree of non-similarity of mass and thermal diffusion process.…”

Section: ( )mentioning

confidence: 74%

“…The conversion from density to temperature field is simple where thermal buoyancy is the sole driving mechanism in natural convection. On the other hand, in an evaporative flow [7][8][9][10][11], the driving mechanism is a combination of thermal and solutal buoyancy. Hence, the refractive index and density are functions of both temperature and concentration.…”

Section: Introductionmentioning

confidence: 99%

“…Vinnichenko et al [10], in their study of natural convection driven by evaporation, presented another method for determining the temperature and concentration fields from the refractive index field obtained using the schlieren technique. A background oriented schlieren (BOS) method was used by them.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of temperature and concentration fields from refractive index field for evaporation-induced convective flow

Sabnis,

Anand,

Bakshi

2023

Phys. Scr.

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The present work relates to the simultaneous determination of concentration and temperature fields from a refractive index field, and is motivated by applications in evaporation. Several optical measurement techniques such as schlieren and interferometry can measure the refractive index field, which can then be converted to a density and temperature field for a single component system. The refractive index, however, is dependent on both temperature and concentration for a multi-component system involving combined heat and mass transfer. Hence, either the temperature or concentration field must be known to obtain the other. To circumvent this issue, several methods are evaluated in this study to extract concentration and temperature fields from a refractive index field. The evaluation is performed based on data from a coupled numerical solution of Navier-Stokes, energy and species conservation equations.The refractive index field can be obtained from this computed temperature and concentration field. This refractive index field is then separately used to obtain the combined temperature-concentration field using the method proposed in this work. This method is based on the premise that there is a relationship between temperature and concentration fields which can help to independently calculate both when the refractive index field is known. The temperature and concentration fields obtained using this approach are then compared with the originally computed field and the errors in them are estimated for a wide range of Lewis numbers. From the study, it is concluded that the proposed methods can be used to accurately determine the temperature and concentration fields from a given refractive index field.

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Section: ( )mentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

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Evaluation of temperature and concentration fields from refractive index field for evaporation-induced convective flow

Sabnis,

Anand,

Bakshi

2023

Phys. Scr.

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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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Natural convection flows due to evaporation of heavier-than-air fluids: Flow direction and validity of using similarity of temperature and vapor density fields

Cited by 8 publications

References 32 publications

Evaluation of temperature and concentration fields from refractive index field for evaporation-induced convective flow

Evaluation of temperature and concentration fields from refractive index field for evaporation-induced convective flow

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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