用 PIV 和 LBM 法检验灌水器设计中连续介质假设的适用性.

The characteristics of microfluidic devices are different from those of ordinary fluid devices. One of the most important features of microfluidic devices is the decrease of their characteristic scale. This feature leads to a lot of differences in microfluidic device. Two major differences are included. There are the flow law of the fluid and the physical properties of fluid. The flow law of the fluid in a microfluidic device is different from that in an ordinary fluid device. The physical properties of the fluid in a microfluidic device also differ from that in an ordinary fluid device. The emitter channel is small in size from the point view of its width. As a result, the emitter belongs to the microfluidic device. Therefore, the applicability of Navier-Stokes (NS) equations has been controversial in the analysis of the flow characteristics in the emitter channel. In order to verify the suitability of the continuity medium hypothesis in design of the emitter, the lattice Boltzmann method (LBM) was used to study the flow characteristics of the emitter in this paper. The flow rate field on a specific plane obtained by different numerical methods was analyzed. The numerical methods were LBM and the computational fluid dynamics (CFD) method which was based on the finite volume method. The flow rate field obtained by using the two numerical methods was also compared with the experimental results. The flow rate with larger flow rate gradient of the straight line on the specific plane was also compared and analyzed. Firstly, the mesh independent analysis was made in order to guarantee the numerical accuracy of numerical results. Secondly, the numerical results were compared with those obtained by the finite volume method (FVM) based on the assumption of continuous medium. The numerical results were also made a comparison with the particle image velocimetry (PIV) experimental results. The average relative deviations of the results of the LBM calculation from the experimental values of PIV were analyzed. In addition, the average relative errors of the results of the FVM calculation from the experimental values of the PIV were also analyzed. By comparing flow rate contours, the results showed that the overall flow rate field calculated by the LBM in the specified cross section was in good agreement with the flow rate field measurement by the experiment, and the results also showed that the flow rate field calculated by the CFD method in the specified cross section was in good agreement with the flow rate field measurement by the experiment. The flow rate contour which was calculated by the LBM or CFD showed a large flow rate gradient at the corner of the contraction section. Comparing the flow rate on the specified measurement line, CFD reached its maximum flow rate on the measurement line where the distance was 0.482 mm, and the flow rate obtained by using the computational fluid dynamics method which was based on the finite volume method was 1.176 m/s. The flow rate of PIV experimental results was 1.09 m/s. The flow rate obtained by using the LBM reached its maximum value, and the result of the flow rate obtained by using the LBM was 1.06 m/s. Therefore, the relative error of flow rate obtained by using the CFD from the experimental result at 0.482 mm was 7.8%, which was larger than that of LBM which had the relative error of 2.7%. In view of the arithmetic mean of the relative deviation, the results showed that the arithmetic mean of the relative deviation of the CFD deviation from the PIV experiment was 0.139%, while the arithmetic mean of the relative deviation of LBM deviation was 0.115%. The results were very close. Therefore, the computational fluid dynamics method based on the assumption of continuous medium is applicable for analysis of the flow field in the emitter which has the characteristic size of 1 mm. [ABSTRACT FROM AUTHOR]