Experimental Study On Hydrodynamic Response Of Submerged Tube In Wave Flow Field

Submerged floating tunnel is a new underwater structure,which has irreplaceable advantages for traffic engineering in deep water(100m and above)or in some special geomorphological underwater conditions.As the construction of it is very challenging.So far,there is no underwater levitation tunnel was built.In the past 10 years,scholars at home and abroad have carried out a lot of exploratory research on the floating tunnel,but the hydrodynamic response law of the floating tunnel,which is the most important part,has not made a breakthrough yet.At present,the research is still limited to the two-dimensional physical model test and mathematical model construction of rigid cross-section.the former one ignores the complex constraints of suspended tunnel structure and the elastic characteristics of slender structure,while the latter one lacks the basis for selecting key parameters.Due to that circumstance,the development of three-dimensional physical model test will play an important role in solving the problem of hydrodynamic response of floating tunnel.By using the method of physical model test,this paper makes a tentative study on the dynamic response of three-dimensional elastic levitation tunnel in flow and wave flow field,I use different axial forces to measure the acceleration of the tube and the tension of the restrained cable,and after analyzing the laws with hydrodynamic factors(current velocity,wave elements),the experimental results show that:(1)Axial force loading changes the vibration characteristics of the structure,which greatly affects the dynamic response of the structure.When the axial force changes within the range of F = 20 KN ~ 80 KN,it can effectively limit the range of motion of the tube in water,but excessive axial force can cause the tube vibration to increase.(2)Under the action of water flow,the movement of the tube can be divided into two categories: when the reduced velocity Ur≤1.0,the amplitude of the tube acceleration response is very small,the change in cable tension increases with the increase of the flow velocity,and the tube has stable displacement but no vibration under the action of flow;when the reduced velocity is ≥1.1,the acceleration amplitude of the tube increases significantly with the increase of the flow velocity,and the tube will vibrate horizontally.(3)When the axial force changes in the range of F = 20 KN ~ 80 KN,when the reduced speed Ur≤1.0,the axial force can limit the displacement of the tube and the change range of the cable tension;when the reduced velocity ≥1.1,the response amplitude of horizontal acceleration and the variation range of the cable tension increases with the increase of axial force,which indicates that the axial force increases the vibration of the tube under the action of flow.(4)When the wave and current act together,when the reduced velocity Ur= 0.40 ~ 0.56,the acceleration response of tube is dominated by the wave frequency;when Ur = 0.79 ~ 1.11,there are three frequencies in the acceleration response,which are wave frequency and double wave frequency and triple wave frequency;the main frequency of horizontal acceleration response is wave frequency or double wave frequency,and the main frequency of vertical acceleration is wave frequency or triple wave frequency.The axial force has a greater influence on the tension of the inclined cable but no obvious influence on the tension of the vertical cable.Under the same axial force and wave condition,the amplitude of cable tension increases with the increase of flow velocity.