Physical Model And Numerical Simulation On The Movement Rules Of Submerged Ice Blocks In Water Conveyance Canal

The water conveyance canals in cold regions will suffer different ice damagesduring water delivery in winter, such as ice jam and ice dam. They will significantlyreduce the water flow and raise the water level. Meanwhile the ice jam burst willcause more serious disaster at downstream. Submerged ice blocks are the floating iceblocks which submerge under the ice cover at the leading edge. The submergence andstagnation of ice blocks are the foundation of ice jam formation and development.Base on the critical condition of ice submergence, this paper future studied the criticalcondition of submerged ice blocks movement which is significant to prevent the icedamages.This paper adopted the combination of physical model and numerical simulationmethod to acquire the critical condition of submerged ice blocks stagnation and start.We carried out the model ice physical experiment on the basis of the gravity similaritycriterion; established the3-D numerical model and performed fine simulation aboutthe hydrodynamic characteristic. Then the critical condition computational formula ofsubmerged ice blocks stagnation and start could be acquired. The main researchachievements included:(1) This paper chose the polyethylene whose density is closely to the natural iceas the model material for submerged ice blocks and ice cover. Then we carried out theexperiment on the basis of the gravity similarity criterion. By changing the flowvelocity V under the ice cover, depth of water h and shape (thickness t，length l，widthb) of blocks, the experiment not only verified that the longitudinal start velocities ofblocks were larger than the transverse velocities, but also got the influence factors oncritical state: Along with the increase of relative shape t/l，relative water depth t/h andrelative width b/B, the critical width froude numberFt reduced accordingly. Usingthe regression analysis to the experimental data, we obtained the critical conditionequation of submerged ice blocks start which is more accurate.(2) In order to further study the critical state of submerged ice blocks, we tookadvantage of numerical modeling to research the bottom hydrodynamic forces. Byapplying Realizable-turbulence model and Wall Functions, numericalsimulation was made to the Venturi effect and the leading-edge effect beneath ice blocks. The comparison between Larsen’s physical model experimental results andnumerical simulation results was conducted, and they were in good agreement, whichproved that the simulation results were reasonable and reliable. By analyzing theeffect factors which involved the flow velocity V under the ice cover, relative waterdepth t/h and relative width b/B, the computational formula of the Venturi effect andthe leading-edge effect were achieved. On the basis of the equations, the pressurecomputational formula at bottom of submerged ice blocks could be approximatelycalculated.(3) On the strength of hydrodynamic force, drag force, stress force, validbuoyancy and frictional force, through the force balance, the critical conditioncomputational formula of submerged ice blocks stagnation and start could be acquired.Compared to the experimental results, the formula was in good agreement, whichproved its veracity.