Study On Spreading And Instability Of Liquid On The Liquid-liquid Interface

Surface tension gradient due to concentration and temperature differences induces liquid convection,known as Marangoni effect.The Marangoni effect has been extensively studied to understand its fundamental underlying physics and its industrial applications.This paper study Marangoni effect of droplet in three-phase liquid system.In this system Silicone oil is chosen as a driving liquid,and N-hexadecane is chosen as a driven liquid,Using a high-speed camera to capture the spreading process of N-hexadecane driven by Silicon oil on the sodium dodecyl sulfate（SDS）solution.The experiment shows that,n-hexadecane driven by Silicone oil spreads from inside out,forms a ring structure.According to spreading dynamic behavior of internal and external boundaries of n-hexadecane ring,The paper study the spreading pattern of internal and external boundaries of N-hexadecane ring,and the influence of Silicone oil volume on the spreading process.Analysis shows that the spreading law of internal silicone oil conforms to single droplet spreading at the liquid interface.In the initial spreading stage,the spreading of four-phase contact line（internal boundary）between silicone oil,air,N-hexadecane and water is dominated by gravity,The scale law of spreading distance R of four-phase contact line and t is in the range of～^1/4～～^1/2.Due to gravity influence,the larger the volume of silicone oil,the faster four-phase contact line spreads.The volume of silicone oil has no effect on the scaling law of the whole spreading process.The next spreading stage,the spreading of the contact line is dominated by interfacial tension gradient.The scale law of spreading distance R and t conforms to～^3/4.Under silicone oil driven,the liquid thickness of N-hexadecane at the four-phase contact line（internal boundary）between air,silicone oil,N-hexadecane and water increases,changing the contact angle at three-phase contact line（external boundary）between air,N-hexadecane and water.The change of contact angle leads to produce the interfacial tension gradient.The interfacial tension gradient drives external boundary to spread.Because the spreading of the three-phase contact line is dominated by interfacial tension gradient,the scale law of spreading distance R of three-phase contact line and time t conforms to～^3/4.This paper not only research the spreading process of single droplet drivn by single droplet.In addition,this paper research the spreading process of two N-hexadecane droplets drivn simultaneously by two silicon oil droplets The experiment find that N-hexadecane liquid form“8”pattern.In two liquid ring’s collision position,liqui ring deforms to two parallel liquid column.The time of parallel liquid column arising Rayleigh-Plateau instability is faster than liquid ring.This paper also researchs the spreading process of complete N-hexadecane membrance simultaneously drivn by two silicon oil droplets.The experiment find that N-hexadecane liquid forms different pattern.After N-hexadecane ring completes Rayleigh-Plateau instability.The water surface arises two big droplet.After analysis,it is found that the big droplets are produced under the action of surface tension.