Experimental Investigation And Numerical Simulation Of Three Dimensional Turbulent Swirling Flow Locally Generated In Circular Pipe

Swirling flow (or spiral flow) can be decomposed axial flow and compulsive whirling current. Swirling flow is a sort of special flows matching together vortex line with flow line. Swirling flow is widely used in industry, such as in jet technology, combustion technology, pneumatic transportation, cyclone separator, hydraulic flotation and so on. Swirling flow is a general phenomenon in all kinds of separators, cyclones, agitators, vortex pipes and many piping systems. Today, swirling flow technology is also applied in daily life, such as in cooking gas stove, vacuum sweeper, etc. On the other hand, swirling flow can be seen frequently in nature, such as tornado. Therefore, it is significant for studying efficient and practical generating swirling device that we obtain the law of development of swirling pipe flow.In general, swirling flows in pipe are generated by three ways: tangenlially inletting medium, guiding fluid by vanes with a certain angel and axially rotating pipe. By means of theoretical analyses, experimental measures and numerical calculations, law of development and decay of theswirling Hows generated by certain vanes with a certain angel in pipe were studied in this dissertation.In theoretical analyses, based on the characteristic of the axisymmelric swirling How, exponentiallly decay of laminar swilling How and performance of turbulent flow in pipe by simplifying N-S equation and mathematic knowledge were obtained. Through analyzing momentum equation of infinitesimal swirling flow, pressure distribution with the radial difference was demonstrated. Moreover, the author was trying to deseript the development of swirling in form of equations in the thesis.Through a large number of experimental studies, the velocity and pressure distributions of three-dimensional swirling flow were measured by five-hole exploring tube and characteristic of flow was basically discovered.In numerical calculation, various turbulence models were generalized. To simulate the swirling flow flied, three-dimensional axisymmetric form of the continuity and the time-averaged Navier-Stokes equations were considered. The set of differential equations was solved with the help of the Semi-Implicit Method for Pressure-Linked Equations and logarithmic law of the wall numerically in a finite volume technique and standard k- e module. During the calculation procedure, underrelaxation technique was used to obtain steady solutions. Calculation results showed that crossing tangential velocity has the characteristic of forced vortex and the area of free vortex almost disperses, while axial velocity and pressure distributions were coincidence with experimental conclusions.The study is extended to include experimental research with numerical simulation. By means of calculation, it is effective and convenient to predictthese variable properties while it is significant for the experimental study and practical designing utility.