Evaluationof numerical simulation accuracy for two-ways mixed flow drip irrigation emitter based on CFD

Abstract

In order to evaluate the accuracy and applicability of the CFD numerical simulation method, we taken new two-ways mixed flow drip irrigation emitter as the research object, designed three kinds of emitter prototypes, and put forward the evaluation methods of the macroscopic flow rate index and the microscopic flow velocity index. According to the test results of flow rate and flow velocity by experiment and Particle Image Velocimetry (PIV)technology, analyzing the error ofthree kinds of wall function and seven classes physical models. The analysis results show that taking the macroscopic flow rate index as the evaluation standard, and numerical simulation accuracy of the enhanced wall function is higher and better. Comprehensive analysis of seven classes physical model by using the enhanced wall show that the average relative errorsof the Standard k-ϵmodel, RNG k-ϵ model, Standardk-ωmodel, SST k-ω modelare smaller, followed by 2.16%, 1.47%, 1.84% and 1.90%,but RNG k-ϵmodel has better simulation accuracy. Taking the microscopic flow velocity index as evaluation standard, the average relative errorsare 3.42%, 2.68%, 2.34% and 1.81%, while the SST k-ωmodel has better simulation accuracy. Comprehensive evaluating two indexes, when the weight coefficient were taken at 0.5, respectively, the average relative error of SST k-ωmodel iscalculated to be 1.85%, which is more suitable for the numerical simulation of emitter. The accuracy and applicability of various simulation method sare considered in the calculation of the flow rate and flow velocity, and the analysis of microscopic flow field.