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首页> 外文期刊>Computers and Electronics in Agriculture >Numerical simulation of spray ejection from a nozzle for herbicide application: Comparison of drag coefficient expressions
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Numerical simulation of spray ejection from a nozzle for herbicide application: Comparison of drag coefficient expressions

机译：从除草剂应用中喷射喷射喷射的数值模拟：拖曳系数表达式的比较

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This paper compares the different expressions of drag coefficients using a Computational Fluid Dynamics (CFD) code. This code is a Large-eddy Simulation-Lagrangian Stochastic Model (LES-STO) to simulate liquid particle ejection from a HARDY (TM) ISO F110-03 nozzle. The results are compared to laboratory measurements of the vertical component of the liquid particle velocity. To do this, the physical process was segmented from the trajectory of the particles into the following two stages: a Transitional Stage and a Sedimentation Stage. At each of these stages, speeds, Reynolds numbers and drag coefficients were calculated independently for each particle during each time step. A model was used that allows for a 1:1 simulation with respect to the applied volume, using a time step of 2.10(-4) s, evaluating a total of 15,500,000 particles in 40 s of simulation. For the aerodynamic drag coefficient, six different expressions were compared with the laboratory tests; the one proposed by Turton and Levenspiel (1986) achieved the best agreement of the velocity values as shown in the Chi-square goodness of Fit and F-test variance. With these data, it was possible to validate what the Environmental Protection Agency (EPA) described in its pesticide specifications. Potential drift is significantly reduced when the nozzle is placed at a height of 0.75 m because particles larger than 300 gm do not reach sedimentation velocity before impacting the ground. For these drops, the inertia forces do not reach equilibrium with the traction forces, so the particles maintain the ejection inertia. Unfortunately, there is not presently a technology that guarantees the exclusive application of the diameters that are required on the product label.
机译：本文使用计算流体动力学（CFD）代码比较了拖曳系数的不同表达式。该代码是一个大涡模拟拉格朗日随机模型（LES-STO），用于模拟液体颗粒从硬质（TM）ISO F110-03喷嘴中喷射。将结果与液体颗粒速度的垂直分量的实验室测量进行比较。为此，将物理过程从颗粒的轨迹分段为以下两个阶段：过渡阶段和沉降阶段。在每次步骤期间，在每个阶段，为每个粒度独立地计算速度，雷诺数和拖曳系数。使用模型，其允许相对于施加的体积的1：1模拟，使用2.10（-4）S的时间步长，在模拟40秒中评估总共15,500,000个粒子。对于空气动力学阻力系数，将六种不同的表达与实验室测试进行比较; Tulton和Levenspiel（1986）提出的那个达到了速度值的最佳协议，如Chi-Square良好的拟合和F-Test方差所示。通过这些数据，可以验证其农药规格中描述的环境保护局（EPA）。当喷嘴放置在0.75米的高度时，潜在漂移显着降低，因为在撞击地面之前，大于300g的颗粒不会达到沉降速度。对于这些滴度，惯性力不会达到牵引力的平衡，因此颗粒保持喷射惯性。不幸的是，目前还没有保证产品标签所需的直径的独家应用。

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