Numerical Simulation and Optimization of Elbow Pipe with Baffle Structure
|Keywords||Elbow Pipe Fluid-Structure Interaction Baffle Flow Characteristics Numerical Simulation|
Due to the wide application of elbow pipe and the problems caused by the vibration of elbow pipe, the research for the baffle structure in elbow pipe is beneficial for people to solve the problems for the safety of the application of elbow pipe.In this thesis, the theoretical models were summed up for: i) the conveying fluid in a straight pipe with two ends pinned; ii) the conveying fluid in cantilever straight pipe, and iii) the conveying fluid in arc-shaped curved pipe. Then, their equilibrium differential equations of motions were derived via element balance method respectively. And finally, the equilibrium differential equations were discretized with Galerkin method for the case of i) and ii), and the differential equations with the format of the differential quadrature method were derived for the cases of ii) and iii).The distribution of the pressure and the flow velocity in an original elbow pipe was analyzed with Fluent code with RNG k-εmodel and the irregularity of the flow in elbow pipe was observed. Furthermore, for the purpose to reduce the vibration of the elbow pipe caused by such kind of irregularity, embedded baffle structure was considered. The distributions of pressure and flow velocity in the elbow pipes with one, two or three-piece baffles, arranged by proportional rule, were numerically analyzed. The comparison between the results shows that, among the three schemes, the scheme of the three-piece baffles (Fluid-1124) could improve the irregularities of fluid flow most effectively. With the reference of the results for the proportionally arranged baffles scheme, the irregularity of the flow in the elbow pipe with embedded baffles arranged by golden cut rule was numerically simulated. It was found that one can see that the scheme“Fluid-nn”can further reduce the maximum velocity, maximum pressure and pressure difference in the flow.Some minor changes at local positions of the baffle were also made to further minimize irregularity, such as, translation, curvature variation, incomplete and extension of the baffle. The computation with scheme Fluid-215 showed that: a) The first three changes could not optimize remarkably the flow characteristics; b) 15mm-extension of the second baffle in the outlet-direction could further improve the flow characteristics, where the low flow-velocity zone at the outlet section was eliminated, and the secondary and return flow were avoided.Elbow pipe with flowing fluid inside is a typical problem of Fluid-Structure Interaction (FSI). In order to achieve actual response characteristics of pipe and flow field, both Fluent and Abaqus codes are adopted to compute respectively the flow in the original elbow pipe and that in the optimized elbow pipe (Scheme Fluid-215), taking into account FSI. The results showed that: 1) The flow field considering FSI is similar with that without considering it; 2) 1mm of thickness of the embedded baffle could meet the requirement strength; 3) The elbow pipe possesses sufficient strength and stiffness; and 4) With the scheme Pipe-e, the stress distribution in the elbow pipe could be distinctly modified after optimization.Based on the numerical simulation of the embedded baffle structure in elbow pipe, the flow characteristics within the elbow pipe were discussed, an optimization approach was suggested and a favourable baffle structure was obtained, which is significant for the design and the application of raffle structure in elbow pipe.