ALGORITHM FOR DETERMINATION OF DYNAMIC SURFACE TENSION BY PULSING MENISK METHOD
DOI:
https://doi.org/10.31471/1993-9981-2022-1(48)-36-43Keywords:
liquid meniscus, capillary surface, hysteresis, pulsation, surface tension, structure, algorithm, systemAbstract
By mathematical modeling of quasi-statics of capillary surfaces of the lying drop type, the methodological basis for the study of surfactants on the dynamics of surface tension by the method of pulsating meniscus was obtained. The essence of the method is that, by direct and reverse supply of gas to the meniscus, the process of pulsation of the meniscus in the vicinity of the maximum pressure in it, the value of which uniquely determines the surface tension on each cycle. The effect is that the meniscus, with each measurement cycle, does not close after reaching the maximum pressure in it, but goes into a new steady state of equilibrium, ie the process of adsorption of surfactants does not stop. Due to this, the proposed method corresponds to the accuracy of measuring the surface tension by the method of maximum pressure in the bubble and the efficiency of the lying drop method. The possibility of implementing the proposed method is theoretically justified by developing a mathematical model of the process of pulsation of the meniscus in the vicinity of the maximum pressure in the system closed relative to the amount of gas phase. Based on theoretical studies of the simulation results, a block diagram is proposed and an algorithm for the process of determining the dynamic characteristics of surface tension is developed.
The control process is controlled by a personal computer via an intermediate data acquisition device NI USB-6009. This necessitates the development of an algorithm for controlling the measurement process, as well as ensuring the correct processing of the obtained data according to the method described above. This condition was implemented in the software environment in the form of a virtual device. The virtual component of the device is made using the graphics software LabVIEW, then instead of code it uses visual components. Convenient control of the measurement process is achieved by the fact that the front panel of the program displays all the settings in the form of virtual buttons, switches, input windows and selection of input information that corresponds to the design of the installation. Any personal computer with a free USB port and LabVIEW software installed to ensure this operation will work effectively.
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References
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