# Pure Electric Sweeper Performance Analysis and Test Verification of Dust Extraction Port
## 2 Numerical Simulation and Experimental Research Methods
### Numerical Simulation  
The mesh schematic of the simulation model is given in Figure 2, which in this simulation is unstructured. The overall computational domain is divided into the external air domain and the internal flow field region. A tetrahedral mesh is used for the internal flow field of the dust extraction port, while a hexahedral mesh is used for the external air domain, with a mesh number of 638,587. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**S** & **D** & \(\beta\) & **Height of Ground Clearance** \\ \hline
1200 mm & 160 mm & 60\({}^{\circ}\) & 10 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The specific dimensions of the dust suction port. Figure 1: Internal flow field region and its structural parameters: (**a**) internal flow field region and the location of the measurement points; (**b**) internal flow field region structural parameters; (**c**) simulation model and external air domain structural parameters. The literature [18] gives the conditions for the determination of the flow field, and combined with the Reynolds number formula, it can be found that the Reynolds number in this model is greater than 4000, so the model should use the turbulence model. There are three types of turbulence models, as follows: Standard, RNG, and Realizable. In this paper, the Realizable turbulence model is chosen, which is better able to simulate moderately complex flows such as jets and cyclones than the other two models. The airflow in the suction port is the carrier of the dust particles and the airflow should be in continuous phase, so the Navier-Stokes equation should be used to solve for the gas phase flow. The gas-phase flow should be in accordance with the continuity equation, conservation of mass and conservation of momentum [19]. \[m=\int\limits_{\Omega}\rho dV \tag{1}\]  
\[\frac{\partial u_{a}}{\partial x_{a}}=0 \tag{2}\]  
\[\frac{\partial}{\partial x_{a}}(\rho u_{a}u_{b})=-\frac{\partial p}{\partial x _{a}}+\frac{\partial}{\partial x_{b}}\bigg{(}H_{1}\frac{\partial u_{a}}{ \partial x_{b}}+\tau_{ab}\bigg{)}+\rho g_{a} \tag{3}\]  
where \(m\) is the quality, \(\rho\) is the airflow density and \(\Omega\) is the volume. \(u_{a}\) and \(g_{a}\) are the velocity components in different coordinate directions, \(p\) is the pressure, \(\mu_{1}\) is the viscosity coefficient and \(\tau_{ab}\) is Reynolds stress. During the grit pick-up process, the discrete phase particle volume fraction is low compared to the continuous phase airflow volume fraction, so the gas-solid two-phase flow is a dilute phase flow [20]. The particle equation of motion is used to analyse the gas-solid flow process inside the suction port using the Euler-Lagrange method [21]. Particle equations of motion:  
\[m_{x}\frac{du_{x}}{dt}=F_{M}+G+F_{N} \tag{4}\]  
where \(x\) is the particle parameter, \(m\) is the dust particle mass, \(u\) is the dust particle velocity, \(F_{M}\) is the viscous force, \(G\) is the gravitational force and \(F_{N}\) is the lifting force. The viscous force is calculated as follow [22]:  
\[F_{M}=\frac{18\mu_{2}C_{D}\text{Re}_{x}}{24\rho_{x}d_{x}{}^{2}}m_{x}(u-u_{x}) \tag{5}\]  
Figure 2: Simulation model grid structure. where \(\mu_{2}\) is the viscosity coefficient, \(C_{D}\) is the drag coefficient, \(\rho_{x}\) and \(d_{x}\) are the density and diameter of particles, \(\text{Re}_{x}\) is the Reynolds number of particles and \(u\) is the air rate. The drag coefficient calculated as follow [23]:  
\[C_{D}=\left\{ \begin{array}{l}\dfrac{24}{\text{Re}_{p}},\text{Re}\leq 1\\ \dfrac{24\Big{(}1+0.15\text{Re}_{p}^{0.678}\Big{)}}{\text{Re}_{p}},1\leq\text{ Re}_{p}\leq 1000\\ 0.44,\text{Re}>1000\end{array} \right.