Experimental Study On Local Scour Protection Of Bridge Piers Based On Air Flow Regulation Structure

Local scouring of bridge piers is an important cause of bridge damage and wreckage,scouring protection measures are an important part of local scouring research,existing protection measures are mainly based on riverbed anti-scouring proposed,and changing the water flow structure to reduce scouring hazards should be a feasible idea,but the current research results are less,using airflow to change the water flow structure is not seen research results.The paper intends to carry out experimental research on local scouring of bridge piers based on airflow-regulated water flow structure based on bubble plume related research results,which should have certain theoretical significance and engineering practice value.Translated with www.Deep L.com/Translator(free version)Based on the mechanism of local scouring of bridge piers,the flow characteristics of bubble plume and the current situation of practical application of engineering,this paper proposes a theory of passing a certain pressure of gas from the river bed facing the river water to change the water flow structure around the bridge piers,impede the scouring of the river bed by the downward flow of water in front of the bridge piers or the turbulent vortex around the bridge piers,so as to reduce the impact of water flow on the bridge foundation and ensure the stability of the bridge foundation.A blast aeration device was designed and model-controlled tests were conducted to investigate the relationship between the proximity flow rate,airflow rate and aeration position on the local scour evolution and scour depth morphology of bridge piers based on airflow-regulated water flow structures.Taking the maximum scour depth and width as indexes,the anti-scour effect of blast aeration device was quantitatively analyzed.The test results mainly include: compared with no air flow,the local maximum scour depth of pier with aeration device is significantly reduced;when the aeration device is installed to make the air flow out of the water 0D before the pier,the anti-scour effect is the most obvious;with the increase of air flow,the regulation effect of air flow on water flow structure is increased,and the scour protection effect is more obvious.The three-dimensional turbulent field around the pier based on the flow structure of air flow regulation is measured and compared with the pier without air flow regulation,and the mechanism of the flow structure of air flow regulation is analyzed.FLOW-3D software is used to establish three-dimensional flow and air three-phase flow model,based on RNG k-ε turbulence model is discretized by using the local nested grid and the special Favor grid method of the software.The flow characteristics of the flow field around the pier with or without air flow and the change characteristics of local scour hole are analyzed.The comparison with the experimental results shows that the numerical simulation is in good agreement with the experimental results.