Evaluation of 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 of three 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 errors of the Standard k-ε model, RNG k-ε model, Standard k-ω model, SST k-ω model are smaller, followed by 2.16%, 1.47%, 1.84% and 1.90%, but RNG k-ε model has better simulation accuracy. Taking the microscopic flow velocity index as evaluation standard, the average relative errors are 3.42%, 2.68%, 2.34% and 1.81%, while the SST k-ω model 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-ω model is calculated to be 1.85%, which is more suitable for the numerical simulation of emitter. The accuracy and applicability of various simulation methods are considered in the calculation of the flow rate and flow velocity, and the analysis of microscopic flow field.

Hydraulic Performance and Energy Dissipation Mechanism Analysis of the Tesla-Shaped Emitter

“…Guo. [14] conducted research on two-way counter flow emitters and believes that the closer the flow ratio of forward and reverse flow is to 1, the better the hydraulic performance of the emitter. The reason for the different conclusions is that the structural design of the two-way counter flow emitter makes the two water flows purely rely on the hedging effect to dissipate energy.…”

“…Li et al [12] proposed an improved bidirectional flow channel emitter, which consumed the energy of the water body mainly through the mutual mixing of positive and negative bidirectional flows and the contraction of the cross-sectional dimensions. Its minimum flow can be as low as 1.50 lph under the inlet pressure of 10 mH 2 O. Wang et al [13,14] researched a two-ways mixed flow emitter and showed that the special design of the channel could lead to the formation of rapid turning flow, forward and reverse bidirectional flow, and hedge mixing flow, etc., which increased the energy dissipation of the water movement. The turbulence intensity of the channel mostly ranged from 0.1 and 0.4, higher turbulence intensity indicated more energy consumption in the channel.…”

Effects of aeration on hydraulic and anti-clogging performance of subsurface drip irrigation emitters

“…The nite volume method was used to separate the governing equations, and the second-order upwind convection term was used to separate the pressure term. The SIMPLE algorithm was used to solve the coupling problem of velocity and pressure (Guo et al 2020). In the ow eld calculation, the inlet boundary condition was set to pressure-inlet, and the size setting is consistent with the physical test.…”

Research on Hydraulic Properties and Energy Dissipation Mechanism of the Novel Water-Retaining Labyrinth Channel Emitters

“…Zhangzhong et al [25] constructed 13 M-type fractal flow paths with different geometrical parameters based on fractal theory and analyzed the influence of different geometrical parameters on the variation of the internal flow field and hydraulic performance characteristics using the CFD and PIV methods. Guo et al [26] designed three kinds of two-way mixed flow drip irrigation emitter prototypes and established the evaluation method of the macroscopic flow rate index and microscopic flow velocity index. Xu et al [27] proposed a pit drip irrigation emitter based on the pit structure in the water transport tracheids of bionic plants and designed the four optimized labyrinth flow channels.…”