THE GOAL OF THIS WORK IS INVESTIGATION OF MICRODROPLET FORMATION IN A T-JUNCTION SYSTEM. THESE SYSTEMS HAVE HIGH SPECIAL APPLICATION PARTICULARLY IN MEDICAL SCIENCE, SO THE MODELING AND STUDY OF SUCH SYSTEMS ARE HIGHLY APPLICABLE. THERE ARE SEVERAL METHODS FOR NUMERICAL STUDIES OF MICROFLUIDIC SYSTEMS OF WHICH THE LEVEL SET METHOD (SLM) WAS USED BECAUSE OF ITS APPLICATION FOR IMMISCIBLE LIQUID/LIQUID SYSTEM. THE CONDITIONS OF THE GENERATED DROPLET WHICH ARE THE SIZE AND THE NUMBER OF DROPLETS IN A PERIOD OF TIME, DEPENDS ON SOME PARAMETERS OF WHICH A VERY IMPORTANT AND EFFECTIVE IS REYNOLDS NUMBER. HENCE EFFECT OF THIS PARAMETER ON THE SIZE AND THE FREQUENCY OF DROPLET GENERATION INVESTIGATED. FOR PREDICTION OF THE SIZE OF DROPLETS, THE EFFECTIVE DROPLET DIAMETER OF EACH GENERATED DROPLET WAS EVALUATED AND A CURVE FOR EACH STUDY PLOTTED. THE DROPLET FORMATION WAS DEVELOPED IN THREE DIMENSIONS AND A MICROFLUIDIC T-JUNCTION USING COMSOL MULTIPHYSICS SOFTWARE.

DROPLET FORMATION IN MICRO-CHANNELS IS ONE OF THESE TOPICS WHICH ARE OF GREAT INTEREST WITHIN SCIENTISTS. IT IS IMPORTANT TO COMPREHENSIVELY UNDERSTAND THE DYNAMIC OF DROPLET IN MULTIPHASE SYSTEMS FROM THE POINT OF FORMATION TO THE TRANSPORT PROCESS ALONG THE MICRO-CHANNEL. IN THIS RESEARCH, THE LATTICE BOLTZMANN METHOD (LBM) IS EMPLOYED TO SIMULATE DIFFERENT MODE OF DROPLET FORMATION IN A CROSS-SHAPE MICRO-CHANNEL. IN THIS RESEARCH, INDEX FUNCTION MODEL WHICH IS A RELIABLE AND COMPROMISING TWO-PHASE LBM MODEL IS EMPLOYED TO TRACK THE INTERFACE BETWEEN DIFFERENT PHASES. FIRSTLY, ACCURACY OF THE MODEL IS EXAMINED BY TWO WELL-KNOWN BASIC ANALYTICAL MODELS INCLUDING LAPLACE LAW AND COALESCENCE OF TWO STATIC DROPLETS, AND AS A RESULT OUR RESULTS INDICATED GOOD AGREEMENT WITH ANALYTICAL OUTCOMES. THUS, OUR FINAL RESULTS QUALITY AND ACCURACY ARE CERTIFIED. BESIDES THAT, BUBBLE FORMATION STEPS IN CROSS JUNCTION MICRO-CHANNEL ARE SIMULATED AND ARE COMPARED TO EXPERIMENTAL RESULTS IN STAGES. ACCORDING TO THIS COMPARISON, OUR RESULTS PRECISELY MATCH WITH EXPERIMENTAL ONES. IN ORDER TO STUDY CROSS-SHAPE MICRO-CHANNEL DROPLET FORMATION, DIFFERENT PROPERTIES FOR FLUIDS AND ALSO DIFFERENT POSITION OF FORMATION ARE STUDIED. DROPLET FORMATION IS THOROUGHLY INVESTIGATED BY MENTIONED NUMBERS. THE CAPILLARY NUMBER CONCLUSIVELY, WHICH IS THE RATIO BETWEEN VISCOSITY AND SURFACE TENSION, IS ONE OF THE MOST IMPORTANT DIMENSIONLESS NUMBERS IN DETERMINATION OF FLUID FLOW CHARACTERISTIC IN MICRO-CHANNELS. AFTER ANALYSIS OF CAPTURED RESULTS, HIGH DEPENDENCE OF FORMATION DYNAMICS AND ITS FREQUENCY ON CAPILLARY NUMBER IS OBSERVED. ALSO VELOCITY RATIO AFFECTED UPON FORMATION SUBSTANTIALLY. IN FACT, FOR HIGHER VELOCITY RATIOS, FORMED DROPLETS ARE EFFECTIVELY SMALLER AND IN THIS SITUATION WEBER NUMBER IS DECISIVE PARAMETER. FURTHERMORE, RESULTS FOR VARIETY OF VALUES FOR DIMENSIONLESS NUMBERS ARE ANALYZED AND COMPARED WITH EACH OTHER AND THIS COMPARISON LEFT IMPORTANT BEHAVIOR OF FORMATION.

EMULSIONS CONSIST OF DROPLETS OF ONE LIQUID DISPERSED IN ANOTHER IMMISCIBLE LIQUID, IS ONE OF THE APPLICATIONS OF TWO PHASE FLOW IN MICRO CHANNELS. IN THIS WAY, CO-FLOWING DROPLET FORMATION IS INVESTIGATED IN THIS RESEARCH. IN THIS PAPER, THE INDEX FUNCTION MODEL OF LATTICE BOLTZMANN METHOD IS USED TO SIMULATE DROPLET FORMATION PROCESS IN MICRO-CHANNEL EMULSIFICATION (MCE) AT LOW CAPILLARY NUMBER IN A COW-FLOWING MICRO-CHANNEL. ACCURACY OF CODE IS ASSESSED BY THREE WELL-KNOWN ANALYTICAL MODELS. FURTHERMORE, IN THIS SIMULATION, VELOCITY RATIOS AND STREAMLINES IN DIFFERENT TIMES ARE INVESTIGATED AND THE RESULTS ARE IN GOOD AGREEMENT WITH LAST RESEARCHES. THIS INDICATES THAT INDEX FUNCTION MODEL HAS A GOOD ACCURACY AND HIGH STABILITY TO SIMULATE THIS KIND OF FLOW. MOREOVER NEW IDEA IS INTRODUCED TO RAISE QUALITY OF FORMED DROPLETS. AS MATTER OF FACT, DROPLET FORMATION IS OPTIMIZED BY OBSTACLES IN PASSAGE OF TWO-PHASES. GENERALLY, INSTEAD OF SIMPLE CO-FLOWING MICRO-CHANNEL, NEW ONE BY DIFFERENT GEOMETRY AT ENTRANCE OF PHASES IS STUDIED. IN OTHER WORDS, BY PRESENT OF OBSTACLES, INTERACTION OF TWO PHASES IS INTENSIFIED AND SHEAR FORCE IS MORE EFFICIENT ON DISPERSED PHASE. AS A RESULT, FORMATION QUALITY AND FREQUENCY CHANGE POSITIVELY. AFTER SIMULATION OF THIS PRESENTED MODEL, RESULTS ARE COMPARED WITH PREVIOUS SIMPLE MICRO-CHANNEL FOR SAME ENTRANCE PARAMETERS (VELOCITY RATIO, CAPILLARY NUMBER AND ENTRANCE GEOMETRY) AND THIS COMPARISON INDICATES EFFECTIVE ROLE OF OBSTACLE ON FORMATION OF DROPLETS WITH HIGHER QUALITY. BY INVESTIGATION ON OBSTACLE, THROUGH DIMENSIONLESS NUMBERS, DECISIVE PARAMETER FOR OPTIMIZED FORMATION IS DETERMINED. GEOMETRY OF OBSTACLE PARTICULARLY IS STUDIED AND BEHAVIOR OF DROPLET FORMATION IS REPORTED. ACCORDING TO THE RESULTS, DROPLET QUALITY IS DRAMATICALLY UNDER EFFECT OF SMALL GEOMETRY VARIATION. THIS SURVEY CAN BE GOOD SOURCE FOR DESIGN OF NEW MICRO-CHANNELS ESPECIALLY FOR EMULSION APPLICATION.