Optimization of trapezoidal labyrinth emitter channel based on MATLAB and COMSOL co-simulation

Abstract: Drip irrigation emitter which has the advantages of little evaporation loss, no surface runoff and almost no deep leakage, is the most important component in drip irrigation system. The conventional drip emitter channel was optimized by finite element analysis through orthogonal experimental design in combination with experimental verification. However, the disadvantage of it lies in high intensity and high cost of the experimental process. Moreover, the optimal results obtained by data analysis through orthogonal experimental design are only the combination of different levels of factors, so it is difficult to determine the law of data change. In this study， the swam intelligence algorism is combined with the finite element analysis to design the parameter optimization of drip irrigation emitter channels by means of MATLAB and COMSOL simulation software. Firstly, MATLAB was used to read the simulation results of the trapezoidal labyrinth emitter in COMSOL software, and the results were passed on to genetic algorithm. Secondly, the optimization was aimed at the flow parameters and viewing the angle of labyrinth, height of tooth, inter-tooth space, units number of labyrinth and tooth diversification index as design variables so as to solve the emitter channel parameters at normal pressure (100 kPa nominal working pressure). Using SPSS software regression analysis method, the multiple linear regression mathematical model between the five variables and the flow pattern index is established. The analysis results showed that the five variables in light of the incidence against the flow pattern index could be sorted as follows: tooth diversification index, tooth depth, units number of labyrinth, channel corner and tooth space. The standardized regression coefficient (beta) of the three parameters, namely, tooth diversification index, angle of labyrinth and inter-tooth space, was positive, which indicated that the flow pattern index can be increased by increasing them; the standardized regression coefficient (beta) of height of tooth and units number of labyrinth was negative, which indicated that the flow pattern index can be increased by reducing them. From the analysis results, it can be seen that under atmospheric pressure, the tooth diversification index in the channel structure parameters had a significant impact on the hydraulic performance of the emitter. The further analysis of the hydraulic characteristics inside the emitter channel showed that the flow velocity in the low velocity region in the dropper channel reached 0.1-1.2 m/s with a 75.1% flow area of the channel area, which had the risk of blockage. And the flow velocity in the high velocity region reached 2.8-3.8 m/s, and 1.5-2.5 m/s in the medium velocity region. The pressure in the channel changes in a linear fashion along the flow channel length. In order to verify the feasibility of the joint simulation calculation method, and to evaluate the actual performance of the emitter with trapezoidal labyrinth channel, a prototype test was carried out. The average error between the calculated value of emitter flow rate and the measured value was 6.1%, which indicated that the optimization result had high precision. The results can provide references for the optimization design of emitter channel parameters of trapezoidal labyrinth channel.