Currently, because of military actions in Ukraine, the prices of mineral fertilizers have increased dramatically. Therefore, a large number of agricultural producers cannot afford to use them to increase productivity. One of the means to minimize this problem due to a relatively low price, is biofertilizers or inoculants that contain effective microorganisms. For their use, a model was developed on the basis of the Sumy National Agrarian University (SNAU), and then implemented in a full-scale version, a system of seed inoculation, which allows the operation to be carried out directly during sowing (Fig. 1).
Fig. 1. Sowing tube with a system of applying liquid to the seed
This article will describe the relationship between the movement of the liquid in the seed tube that surrounds the seeds of crops during sowing using the ANSYS software. In order to describe the relationship between the movement of liquid and grains, it is necessary to consider how the distribution of liquid velocity and turbulence in Fig. 2 reflect the process of enveloping grains with inoculant drops.
Fig. 2. Fluid movement along the seed tube
When the liquid exits the nozzle opening, the stream begins to break up into small drops. This phenomenon can be explained by the influence of external factors, such as air resistance and the internal interaction of liquid molecules. In Fig. 2., presented in ANSYS, you can see the gradual change in fluid velocity in the direction away from the object. This is indicated by gradients of blue color (from lighter to darker), indicating a decrease in flow speed with distance from the source. Over time, the flow of liquid coming out of the nozzle hole begins to lose its coherence due to air resistance and turbulent effects. In the image, this is evident in the lower velocity zone (dark blue areas), which may be related to the discontinuity of the flow. In these zones, the liquid can break up into individual drops.
In a real situation when processing grains, the nozzle injects liquid under high pressure, and through a small opening (0.4 mm) a powerful thin jet is formed. Initially, this jet may be uniform, but the further it moves, the more its shape changes due to turbulence. This is clearly visible in Fig. 2, where small vortex structures appear in the region of reduced velocity (dark blue circular zones). These eddies, similar to turbulent zones, show how the fluid flow becomes unstable, separates into droplets and undergoes changes due to air forces. In this case, these drops begin to surround the grains, covering them evenly. This is due to the internal interaction of liquid molecules, which also contributes to the disintegration of the flow into small drops. In the image, this can be seen in the smooth transitions of color that indicate the change in speed. In places where the speed decreases, the liquid loses its structure due to a decrease in pressure and a decrease in kinetic energy, which also contributes to the formation of small droplets. During further movement, these drops are evenly distributed over the grain surface, penetrating into all cavities and irregularities due to surface tension and capillary forces. This is depicted in the image as a flow that expands and becomes less focused, indicating a gradual loss of fluid energy and transition to a dispersed regime (droplet formation).
Turbulence is one of the important factors of uniform coverage of grains. Fig. 2. shows several turbulence zones marked by low-speed circular structures (dark blue vortex regions). In these zones, vortices are formed, which create turbulent flows, thanks to which the liquid drops change their direction and cover all parts of the grains. Turbulence is a key mechanism to ensure uniform distribution of liquid, especially in those parts of the grain that are not directly under the liquid flow. Thanks to swirls and chaotic movement of liquid particles, drops can reach even the most inaccessible areas of the surface.
Therefore, during grain processing, initially a strong flow of liquid under high pressure creates a main jet, but over time this jet becomes unstable due to turbulence and breaks up into droplets. These drops, with the help of turbulent movement and vortices, evenly envelop the grains, ensuring complete coverage.
Author: Mykola Shelest, assistant of the Department of Agroengineering, Sumy National Agrarian University
