| The erosion around bridge-pier is the main factor cause of bridge failure.Therefore,the estimation of the scour depth at bridge-pier is significantly to ensure the safe operation of bridges.Based on the Flow-3D software,two types of the turbulence model,namely the Renormalized Group(RNG k-?)and the Large Eddy Simulation(LES)model,combined with Meyer-Peter and van Rijn bedload transport rate formula were used to simulation the flow field and the maximum scour depth around the single and double column pier.The threedimensional numerical simulation of the scouring process was carried out and compared with the Melville experimental results.The simulation results are as follows:(1)A three-dimensional numerical model of local scour of bridge piers was established and substituted into Meyer-peter formula.And the applicability of RNG k-? and LES model were evaluated.According to the flow around the single pier and the double pier,the scour pit results of LES model are more accurate than RNG k-ε model.According to the simulation of the maximum local scour depth for a single pier,the maximum scour depth calculated by the RNG k-ε and LES model are 23.5% and 15.4% different from the result of Melville’s experimental,respectively.The above results show that the numerical simulation proposed LES model is more suitable to be used in three-dimensional numerical model of bridge pier scour.(2)The applicability of Meyer-peter and van Rijn formula was evaluated.The results calculated by Meyer-Peter formula show that the shape,range,scour time are in good agreement with the results of Melville experiment.However,by substituting van Rijn formula into the simulation,it can be seen that the calculation results within 17 minutes after the calculation started are in good agreement with Melville experiment results.After the balance of scour and silting,parameters such as the shape of the scour pit are significantly different from the experimental results.The maximum scour pit depth is 0.28 cm,which is 30% different from the experimental value of 0.4cm.The above results show that Meyer-peter formula is better than van Rijn formula in the three-dimensional numerical model of pier scour.(3)Based on the evaluation results of the applicability of the turbulence model and the formula of bedload sediment transport rate in the three-dimensional numerical model of bridge pier scour.In this thesis,LES model was used to establish a three-dimensional numerical model,and the influence of different flow rates on local scour of bridge piers was further studied by substituting Meyer-Peter formula.The results show that when the flow velocity is 0.20m/s,0.25m/s and 0.30m/s respectively,the maximum scour depth increases with the increase of flow velocity. |
