Flume Experiment And Numerical Simulation On Pollutant Concentration Field In The Water Body

As for the environmental pollution problems, what people concern about most isthe pollutant spacial distribution. While pollutant concentration field is one of theimportant indicators to measure the water polluted extent, thus becoming hot topic ofthe current environmental workers. Combining physical experiment in the flume andnumerical simulation, the characteristics of the water pollutant concentration fielddiffusion will be studied.In physics experiment, tracer particles are used to simulate the diffusion featuresof pollutant in the water, concentration field under different working conditions areobtained by PIV. After the PIV images are processed with MATLAB technology,particle concentration measurement is achieved. Adding the synchronous measuredvelocity information of PIV, hydrodynamics analysis for concentration is made. Theresult can provide one method for the study of the pollutant concentration fielddiffusion regularity and its mechanism.First of all, the liquid of different actual concentration were configured, andrelation curve of the actual particle concentration and image particle concentration wasobtained. Considering the effect of constant flow pump on the concentration of flowingthrough, its actual concentration was measured.Then, several physical experiments under different water level and water tankinlet flow conditions are designed, to study the influence of water dynamics conditionon concentration field diffusion from the three aspects of PIV images, averageconcentration and concentration contour. Results showed that,â‘ keeping the tankwater level unchanged, increasing the water tank inlet flow can increase the flowvelocity, strengthen the dispersed effect of hydrodynamic force on particles, makingthe particle distribution widen, average concentration decreased and the values ofconcentration contour bigger.â‘¡keeping the water tank inlet flow unchanged, theraising of water level can decrease flow velocity, weaken the dispersed effect of hydrodynamic force on particles, making the particle distribution narrow, averageconcentration increased and the values of concentration contour smaller. At the sametime, the result of the contrast of concentration contour and velocity contour in thesame profile shows that as the flow velocity increases, particle concentrationreduces,and vice versa.Afterwards, particle diameter is deduced from its area. By comparing the result ofthe different threshold value, the consequence is obtained that using differentbinarization threshold not only leads to different particle size ranges, but also causesdifference in the corresponding particle size range, proving the importance ofbinarization threshold once again. Statistics of frequency and Dv0.5as well as Dv0.9of different concentration liquid shows that with the increase of concentration, particlediameter range becomes narrower, particles are more concentrated in small size range.Finally, using hydrodynamic and water quality module of MIKE3, waterpollutants is simulated. And the verification result of flume experimental results andthe simulation results, shows a good fit. On this basis, the concentration distributionalong the longitudinal section under different working conditions are simulatedrespectively. Conclusion is obtained that increasing hydrodynamic force can causepollutant diffusion widen, at the same time, concentration decreases.