The Experimental Study In The Reconstruction And Convective Heat Transfer Of The Flow Boundary Layer

At present, as the recyclable and clean energy, the urban and sea water has beenwidely used in many fields. Among them, the most effective way is applied to the heatexchanger as the cold or heat source. However, there are a lot of debris in the urbanand sea water, which will form the microscale slime and microorganisms attached tothe wall on the heat transfer surface. And the heat transfer coefficient will be smallerwith the flow rate higher. When the viscous fluid flows through the heated surface, theexistence of the boundary layer at the wall will reduce the heat transfer coefficient. Atthe same time, the performance of the heat exchanger will also been seriouslyaffected.Lattice Boltzmann Method (LBM) is a new mesoscopic numerical method,which is originated from Lattice Gas Automata. It is based on the statistical mechanicsand microscopic dynamics theory. In this method the fluid is abstract for a lot numberof microscopic particles. Then, by constructing a certain physical rules of theevolution mechanisms and statistical calculations, the macro motion characteristic offluids obtained. LBM is suitable for parallel computing for that particle distributionfunction is only concerned with its neighboring node information. LBM is easy toprogram for that the evolution equation of particle distribution function is linear. Itcan be used in complex problems and moving boundaries because of the simpleboundary treatment.The first three chapters of this paper introduce the principle of the latticeBoltzmann method and the application in the moving boundaries problem. And thentrying to use an simulation example to verify the feasibility and reliability of the method. The existence of the spoiler column has effect on the reconstruction andconvective heat transfer of the flow boundary layer. This paper studies conductedalong the following steps:（1）Firstly, the spoiler column models with different shapes are established toanalyze the effect of the shape to the flow characteristics and boundary layer. Thenselect the best shape. The results showed that: despite the existence of the spoilercolumn can thinning the boundary layer on the surface, but the fluid flow slowly inthe recirculation zone.（2）Based on this, the fifth chapter propose that the bottom boundary layer canbe destroyed by the moving spoiler column which driven by the motors and othermechanical. Such disturbances can enhance the entire flow area, thus improving theheat transfer effect of the heat exchanger. As can be seen from the simulation processthat with the spoiler column moving away, the impact on the wall in distancegradually weakened, so that the boundary layer will gradually thickened andrestitution, and then the boundary layer complete the reconstruction.（3）Through the phenomenon of the boundary layer reconstruction, this articleis considering to set up another spoiler column to destroy the boundary layer again inorder to lengthen the weakened layer and form a virtuous cycle. The location of thevirtuous cycle is the boundary layer re-establishment area. thus lengthen the boundarylayer weakened area to form a virtuous cycle. Then, the optimal spacing is obtainedthrough the numerical simulation.