Research On The Combined Effect Of Cavitation And Sand Abrasion Under The Turbulent Coherent Structure

Sediment content in many rivers of our country is considerably high. Fluid machinery in these areas is damaged due to cavitation and sand abrasion, which has threaten directly the safety operation of hydraulic and hydroelectric engineering, causing huge economic losses. The research, therefore, on the combined effect of cavitation and sand abrasion is of great significance.The researchers at home and abroad have done a lot of work on this issue. Due to its complexity of the problem, the theories and experiment results obtained are discrepant, and some of them are even contrary one another.Started from the influence by movement rules of small cavities and solid particles, the mechanisms of combined effect of cavitation and sand abrasion are study in this thesis from the aspect of the turbulent coherent structure near the wall. First, a dynamic equation is established for a single spherical bubble and single spherical sand under the non-turbulent coherent structure near the wall, and then a dynamic equation established under the turbulent coherent structure near the wall. Through comparison, it can be seen that the turbulent coherent structure near the wall influences directly the striking effect of the bubble and sand.A new proposal is put forward at the end of the thesis that the destruction caused by the combination of cavitation and sand abrasion can be mitigated by means of controlling the turbulent coherent structure near the wall.