TY - JOUR

T1 - Experimental Study of the Convective Motions by the PIV Technique within an Evaporating Liquid Layer into the Gas Flow

AU - Lyulin, Yuriy

AU - Kreta, Aleksei

AU - Ouerdane, Henni

AU - Kabov, Oleg

PY - 2020/4/1

Y1 - 2020/4/1

N2 - We present the experimental study of convection in a horizontal liquid layer (ethanol, 3-mm deep), evaporating from a localized surface (10 × 10 mm2) into the gas flow (air). Visualization and measurements of the two-component velocity field in the liquid layer has been carried out with the Particle Image Velocimetry (PIV) technique. In our experiments we consider a novel configuration in which the gas-liquid interface is maintained in the flat position in the confined square area and the volatile liquid evaporates from the planar surface into the gas flowing along the surface. We also consider the effect of the gas velocity (0.0138–0.138 m/s) and the gas and the liquid temperature (20 °C - 50 °C) on the convective flow structure within the liquid layer. It is shown that the gas velocity and both, the gas and the liquid temperatures induce significant changes in the convective flow structure. We give the first experimental proof of the phenomenon that the motion of the gas-liquid interface goes along the counter-current direction to the gas flow as theoretically predicted. The analysis of the experimental data shows that the influence of the gas flow velocity on the Marangoni convection at the maximum temperature (50 °C) is significantly reduced owing to the growth of the diffusion resistance for the gas flow under a strong evaporation from the interface. As a result, it leads to the low surface temperature gradient, which decreases thermocapillary stresses and the circulation velocity of the first (thermocapillary) vortex within the fluid layer. Further, we observe that the disappearance of the second convective vortex circulating in the same direction with the gas flow. The governing factor, determining the structure of convective flows within the liquid is the thermocapillary effect due to the intensive evaporation provided that the cooling and the temperature distribution are uniform on the gas-liquid interface.

AB - We present the experimental study of convection in a horizontal liquid layer (ethanol, 3-mm deep), evaporating from a localized surface (10 × 10 mm2) into the gas flow (air). Visualization and measurements of the two-component velocity field in the liquid layer has been carried out with the Particle Image Velocimetry (PIV) technique. In our experiments we consider a novel configuration in which the gas-liquid interface is maintained in the flat position in the confined square area and the volatile liquid evaporates from the planar surface into the gas flowing along the surface. We also consider the effect of the gas velocity (0.0138–0.138 m/s) and the gas and the liquid temperature (20 °C - 50 °C) on the convective flow structure within the liquid layer. It is shown that the gas velocity and both, the gas and the liquid temperatures induce significant changes in the convective flow structure. We give the first experimental proof of the phenomenon that the motion of the gas-liquid interface goes along the counter-current direction to the gas flow as theoretically predicted. The analysis of the experimental data shows that the influence of the gas flow velocity on the Marangoni convection at the maximum temperature (50 °C) is significantly reduced owing to the growth of the diffusion resistance for the gas flow under a strong evaporation from the interface. As a result, it leads to the low surface temperature gradient, which decreases thermocapillary stresses and the circulation velocity of the first (thermocapillary) vortex within the fluid layer. Further, we observe that the disappearance of the second convective vortex circulating in the same direction with the gas flow. The governing factor, determining the structure of convective flows within the liquid is the thermocapillary effect due to the intensive evaporation provided that the cooling and the temperature distribution are uniform on the gas-liquid interface.

KW - Convection

KW - Evaporation

KW - Experiment

KW - Liquid layer

KW - PIV technique

KW - Shear flow

KW - VELOCITY

KW - STABILITY

KW - DRIVEN

KW - 2-LAYER SYSTEMS

KW - INSTABILITIES

KW - THERMAL PATTERNS

KW - INTERFACE

KW - SURFACE

KW - OSCILLATIONS

KW - STATIONARY

UR - http://www.scopus.com/inward/record.url?scp=85077359965&partnerID=8YFLogxK

U2 - 10.1007/s12217-019-09759-x

DO - 10.1007/s12217-019-09759-x

M3 - Article

AN - SCOPUS:85077359965

VL - 32

SP - 203

EP - 216

JO - Microgravity Science and Technology

JF - Microgravity Science and Technology

SN - 0938-0108

IS - 2

ER -