# Enhancing Flow Field Performance of a Small Circulating Water Channel Based on Porous Grid Plate
## 6 Conclusions  
A circulating water channel, which can reduce the turbulence by porous grid plates for the hydrodynamic characteristic analysis of a small device, is designed. In order to satisfy the requirements of obtaining the high-quality flow characteristics of the test section, the influences of the key parameters of the designed circulating water channel and the pump power on the flow characteristics of the test section are studied. The relationships between the porosity and the resistance coefficients (viscosity and resistance coefficient) are obtained. The influences of the thickness and porosity of the honeycomb; the layer number, porosity, and screen spacing of the screen; and the pumping flow rate on the velocity inhomogeneity and turbulence intensity of the test section are achieved. In this work, the turbulence intensity of the fluid field in the test section can be restrained to about 0.0491. With the increase of the thickness of the honeycomb and the spacing between the screens, the velocity inhomogeneity and the average turbulence intensity decrease first to the valley value and, then, increase. In order to obtain the uniform and low turbulence intensity flow characteristics of the test section, intermediate values of the thickness of the honeycomb and the spacing between the screens should be selected. Similarly, with the increase of the porosity of the honeycomb or screen, the velocity inhomogeneity and average turbulence intensity of the test section first decrease and, then, increase--that is to say, too much or little porosity of the porous grid plate will weaken the rectification performance. The increase of the screen layer number will lead to the decrease  
Figure 21: The velocities of the experiment and simulation at different pumping flow rates. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Pumping Flow Rate** & **2.5 kg/s** & **5 kg/s** & **7.5 kg/s** & **10 kg/s** & **12 kg/s** \\ \hline \multirow{6}{*}{Axial distance x/m} & 0 & 8.08\% & 11.80\% & 9.37\% & 19.27\% & 9.73\% \\  & 0.1 & 11.53\% & 14.58\% & 13.09\% & 7.81\% & 17.81\% \\  & 0.2 & 22.73\% & 16.39\% & 10.68\% & 6.81\% & 21.85\% \\  & 0.3 & 16.66\% & 13.24\% & 13.69\% & 13.08\% & 12.43\% \\  & 0.4 & 15.80\% & 9.39\% & 20.78\% & 14.79\% & 10.66\% \\  & 0.5 & 10.48\% & 13.12\% & 12.15\% & 21.66\% & 11.13\% \\ \hline \multirow{6}{*}{Lateral distance y/m} & \(-\)0.04 & 19.33\% & 10.09\% & 8.05\% & 11.48\% & 11.38\% \\  & \(-\)0.02 & 17.99\% & 22.77\% & 13.43\% & 17.05\% & 18.03\% \\ \cline{1-1}  & 0 & 20.18\% & 18.21\% & 10.75\% & 19.75\% & 16.45\% \\ \cline{1-1}  & 0.02 & 10.64\% & 17.55\% & 16.24\% & 12.93\% & 20.33\% \\ \cline{1-1}  & 0.04 & 9.57\% & 19.23\% & 11.27\% & 14.29\% & 13.68\% \\ \hline \hline \end{tabular}
\end{table} 
Table 8: The relative errors between the experimental and simulation results. of the velocity inhomogeneity and the average turbulence intensity in the test section. However, too many layers of the screen will reduce the velocity of the test section. The analysis results show that the three-layer screen can satisfy the requirements of turbulence suppression. When studying the hydrodynamic characteristics along the axial direction of the tested device, the tested device should be arranged near the outlet area of the test section; when analyzing the hydrodynamic characteristics along the lateral direction of the tested device, the pumping flow rate should be appropriately reduced to improve the uniformity of the turbulence intensity. Based on the obtained optimization results, a small circulating water channel is built. Experiments are carried out, and the experimental results are consistent with the obtained analysis results, which prove the validity of the obtained results. This work can provide important references for the designing of a circulating water channel that is applied to test the hydrodynamic characteristics of a small underwater device. Methodology, L.Z. ; validation, L.Z. ; resources, L.Z. ; data curation, L.Z. ; writing--original draft preparation, L.Z.