CFD Simulation And Experimental Investigation On The Siphonage-pipeline's Inner Flow Field

Siphonage-pipeline is the hardcore structure of toilet, whose inner flow has direct influence on toilet's working performance and is a considered problem by the designers. With the phenomena of dropping flow, backflow and secondary flow effected by syphon centrifugal force and inner surface curvature, the siphonage- pipeline's inner flow is very complicated 3D flow. Therefore, the siphonage-pipeline inner flow is one of the difficult problems in hydro-engineering.At present, there are few research work about siphonage-pipeline have been carried out in China, so we performed an experimental and numerical study to investigate the siphonage-pipeline's inner flow field. The main research work in this thesis is as follows:(1)A mathematic model for the water-rinsing process of siphonage-toilet is established based on classical hydrodynamic theory. The variation of hydraulic characteristic parameters with rinsing time are calculated and the key toilet structure parameters which have effect on the rinsing function are also analyzed.A mathematic method is given evaluate the rinsing effect and sewage-venting function.(2)According to the national standards and statistical results of pipeline's geometrical characteristics, a model test device with a scale of 1:1 has been designed based on the theory of similarity-criteria and dimensional method. This device can easily alter pipeline's shape and cross section area, especially the position of hydraulic packing control point. The numerical simulation of the 3D turbulent flow in archetype and model siphonage-pipeline is done by ANSYS/FLOTRAN, and then the feasibility of model test device is validated.(3)A 2-D PIV (Particle Image Velocimetry) system is used to measure the inner flow field of siphonage-pipeline, and reasonable results have been achieved. This thesis has solved some difficulties of the PIV application in measurement, such as the selection of seed, removal of background noise and the setup of PIV system parameters.(4)Based on the Reynolds N-S average equation and RNG k ?εturbulent model, the numerical simulation of the 2D turbulent flow in siphonage-pipeline is done by Fluent, and then the pipeline's inner flow field of fore-and-aft alteration is achieved. It is more propitious to siphon since alteration through comparison. The simulation results are verifiable with the results measured by PIV. It is feasible to alter pipeline based on experimental pipeline's shape by model test device.