A genuine technological issue–the thermal convection of liquid in a rotating cavity–is investigated experimentally.The experiments are conducted within a horizontal annulus with isothermal boundaries. The inner boun...A genuine technological issue–the thermal convection of liquid in a rotating cavity–is investigated experimentally.The experiments are conducted within a horizontal annulus with isothermal boundaries. The inner boundaryof the annulus has a higher temperature, thus exerting a stabilising influence on the system. It is shown that whenthe layer rotation velocity diminishes, two-dimensional azimuthally periodic convective rolls, rotating togetherwith the cavity, emerge in a threshold manner. The development of convection is accompanied by a significantintensification of heat transfer through the layer. It is shown that the averaged thermal convection excitation inthe form of a system of two-dimensional rolls occurs against the background of oscillations of a non-isothermalfluid in the cavity reference frame caused by the gravity field. The excitation threshold and the structure ofconvective rolls are consistent with the results of the earlier theoretical studies by the authors performed usingthe equations of “vibrational” convection obtained by the averaging method. Furthermore, the experiments haverevealed a new type of averaged flow in the form of a spatially periodic system of toroidal vortices. It is shown thata steady streaming, excited by the inertial oscillations of the fluid, is responsible for the generation of the toroidalvortices. These flows develop in a non-threshold manner and are most clearly manifested in a case of resonantexcitation of one of the inertial modes.展开更多
It is of important significance to study the evolution law of the riverbed near underwater crossing line pipes for ensuring the safe operation of oil and gas pipelines and reducing the risk of damage by waterflood disa...It is of important significance to study the evolution law of the riverbed near underwater crossing line pipes for ensuring the safe operation of oil and gas pipelines and reducing the risk of damage by waterflood disasters.In order to clarify the evolution law of the riverbed near un-derwater crossing line pipes and its negative effects,this paper conductedflume model experiments on underwater crossing line pipes.The physical process of riverbed evolution near pipes was observed and the effect of hydrodynamic conditions on the local pipe scour was studied.What's more,the formation mechanism of local scour at underwater crossing line pipes was revealed.And the following research results were obtained.First,when the waterflow is slow,the riverbed evolution process near underwater crossing line pipes is mainly divided into six stages,including riverbed undercutting,pipe exposure,micro-pore formation,scour hole propagation,pipe suspension and scour equilibrium.Second,vortex and seepageflow are the reasons for the local scour of underwater crossing line pipes.Before pipes are exposed,the silt around the pipes is reduced by vortex.After pipes are exposed,micro-pores occur at the pipe bottom under the joint action of vortex and seepageflow.And thus,local scour is formed.Third,flow velocity and water depth jointly influence the riverbed scour duration of each stage and the maximum scour depth at the pipe bottom.When the Froude number(Fr)is in the range of 0.306e0.808,with the increase of Fr,waterflow gets fast,the maximum scour depth at the pipe bottom increases,the duration for scour equilibrium decreases,the riverbed undercutting depth increases and the riverbed topographically getsflatter.The maximum scour depth at the pipe bottom is 0.9e1.6 times the pipe diameter,and the duration for scour equilibrium is between 1650 min and 2620 min.In conclusion,the experimental results provide important reference for predicting the burial depth of underwater crossing line pipes and ensuring their safe operation.展开更多
基金supported by the Ministry of Education of the Russian Federation(Project KPZU-2023-0002).
文摘A genuine technological issue–the thermal convection of liquid in a rotating cavity–is investigated experimentally.The experiments are conducted within a horizontal annulus with isothermal boundaries. The inner boundaryof the annulus has a higher temperature, thus exerting a stabilising influence on the system. It is shown that whenthe layer rotation velocity diminishes, two-dimensional azimuthally periodic convective rolls, rotating togetherwith the cavity, emerge in a threshold manner. The development of convection is accompanied by a significantintensification of heat transfer through the layer. It is shown that the averaged thermal convection excitation inthe form of a system of two-dimensional rolls occurs against the background of oscillations of a non-isothermalfluid in the cavity reference frame caused by the gravity field. The excitation threshold and the structure ofconvective rolls are consistent with the results of the earlier theoretical studies by the authors performed usingthe equations of “vibrational” convection obtained by the averaging method. Furthermore, the experiments haverevealed a new type of averaged flow in the form of a spatially periodic system of toroidal vortices. It is shown thata steady streaming, excited by the inertial oscillations of the fluid, is responsible for the generation of the toroidalvortices. These flows develop in a non-threshold manner and are most clearly manifested in a case of resonantexcitation of one of the inertial modes.
基金supported by the National Natural Science Foundation of China"Soil-pipe-water coupling effect and seismic damage mechanism of buried water pipeline"(No.:51478403)PetroChina Major Science&Technology Project"Sudy and application of key technology for maintaining 30 billion cubic meters of production in Southwest Oil and Gas Field(No:2016E-0610).
文摘It is of important significance to study the evolution law of the riverbed near underwater crossing line pipes for ensuring the safe operation of oil and gas pipelines and reducing the risk of damage by waterflood disasters.In order to clarify the evolution law of the riverbed near un-derwater crossing line pipes and its negative effects,this paper conductedflume model experiments on underwater crossing line pipes.The physical process of riverbed evolution near pipes was observed and the effect of hydrodynamic conditions on the local pipe scour was studied.What's more,the formation mechanism of local scour at underwater crossing line pipes was revealed.And the following research results were obtained.First,when the waterflow is slow,the riverbed evolution process near underwater crossing line pipes is mainly divided into six stages,including riverbed undercutting,pipe exposure,micro-pore formation,scour hole propagation,pipe suspension and scour equilibrium.Second,vortex and seepageflow are the reasons for the local scour of underwater crossing line pipes.Before pipes are exposed,the silt around the pipes is reduced by vortex.After pipes are exposed,micro-pores occur at the pipe bottom under the joint action of vortex and seepageflow.And thus,local scour is formed.Third,flow velocity and water depth jointly influence the riverbed scour duration of each stage and the maximum scour depth at the pipe bottom.When the Froude number(Fr)is in the range of 0.306e0.808,with the increase of Fr,waterflow gets fast,the maximum scour depth at the pipe bottom increases,the duration for scour equilibrium decreases,the riverbed undercutting depth increases and the riverbed topographically getsflatter.The maximum scour depth at the pipe bottom is 0.9e1.6 times the pipe diameter,and the duration for scour equilibrium is between 1650 min and 2620 min.In conclusion,the experimental results provide important reference for predicting the burial depth of underwater crossing line pipes and ensuring their safe operation.
