The Research Of Pressure Fluctuation In Main Horizontal Drainage Pipe

With the rapid development of urbanization in our country and the continuous improvement of living standards, the requirement of living environment for people is increasingly higher. The safety of the building drainage system is directly related to people’s living environment. Therefore, attention to the building drainage system is also increasing. At present, people generally consider that the pressure fluctuation of the drainage stack has an influence on the safety of the drainage system, but daily experience tells us that the pressure fluctuation of the main horizontal drainage pipe has the direct correlation with the safety of drainage system. With regards to this, this study conducted a research on the influence factors of the pressure in the main horizontal drainage pipe.The first part of this paper, based on the case of the steady flow, the interactive relationship between the drainage system and four elements (i.e. the drainage load, theventilatory capacity, the height of water ingress and the state of outflow) is studied. The second part, based on the case of unsteady flow, we looks into the interactive relationship between the pressure fluctuation of the drainage system and five elements (i.e. the drainage load, the ventilation method, the height of water ingress, the rotation angle of main horizontal pipe and the length of main horizontal pipe).The experiment reveals that the pressure fluctuation inside the main horizontal drainage pipe increases when the drainage load increases, which is roughly thought to be a positive correlation relationship; different kinds of venting ways result in different ventilatory capacity. In other words, ventilating with completely open leads to the largest ventilatory capacity, relevantly, using non-ventilating way leads to the smallest one. In the case of the unsteady inflow, the pressure fluctuation inside the horizontal pipe is involved in a negative correlation relationship, while in the case of the steady inflow, the fluctuation increases when the ventilatory capacity increases. As the height of inflow changes, flushing from a higher place causes greater pressure fluctuation; the bigger that the rotation angle is, the more seriously obstruction will be caused and the greater pressure fluctuation of the main horizontal pipe will occur. The longer that the pipes is, relatively it will cause bigger intramural friction drag, and the greater inhibition to the drainage pipe will be caused, accordingly, thepressure fluctuation of the main horizontal pipe increases. With the state of submerged discharge, the pressure fluctuation of the horizontal pipe increases tempestuously. The submerged discharge should be avoided in order to keep that the outflow is free flow.The3D numerical simulation is done based on the experiment with the steady flow ingress. The results showed that we can better simulate the actual situation of intramural pressure fluctuation in the drainage system by using the Fluent software,which offers anew method to study building drainage system.