In practical engineering,only pressure sensors are allowed to install to detect leakage in most of oil transportation pipelines,while flowmeters are only installed at the toll ports.For incompressible fluid,the leakag...In practical engineering,only pressure sensors are allowed to install to detect leakage in most of oil transportation pipelines,while flowmeters are only installed at the toll ports.For incompressible fluid,the leakage rate and amount cannot be accurately calculated through critical pressure conditions.In this paper,a micro-element body of the pipeline was intercepted for calculation.The relationship between radial displacement and pressure of pipe wall was studied based on the stress-strain equation.Then,the strain response of pipeline volume with pipeline pressure was obtained.The change in volume expansion of pipeline was used to characterize leakage of incompressible fluid.Finally,the calculation model of leakage amount of incompressible fluid was obtained.To verify the above theory,the pipeline expansion model under pressure was established by COMSOL software for simulation.Both simulation results and deduction equations show that the volumetric change has a quadratic parabolic relationship with the change of pipeline pressure.However,the relationship between them can be approximately linear when the pressure change is not too large.In addition,the leakage of incompressible fluid under the pressure of 0 MPa-0.8 MPa was obtained by experiments.The experimental results verify the linear relationship between leakage of incompressible fluid and the change of pipeline pressure.The theoretical and experimental results provide a basis for the calculation of leakage of incompressible fluid in the pipeline.展开更多
Flow around two rotating side-by-side circular cylinders of equal diameter D is numerically studied at the Rey- nolds number 40〈 Re 〈200 and various rotation rate 8i. The incoming flow is assumed to be two-dimension...Flow around two rotating side-by-side circular cylinders of equal diameter D is numerically studied at the Rey- nolds number 40〈 Re 〈200 and various rotation rate 8i. The incoming flow is assumed to be two-dimensional laminar flow. The governing equations are the incompressible Navier-Stokes equations and solved by the finite volume method （FVM）. The ratio of the center-to-center spacing to the cylinder diameter is T/D=2. The objective of the present work is to investigate the effect of rotational speed and Reynolds number on the stability of the flow. The simulation results are compared with the experimental data and a good agreement is achieved. The stability of the flow is analyzed by using the energy gradient theory, which produces the energy gradient function K to identify the region where the flow is the most prone to be destabilized and the degree of the destabilization. Numerical results reveal that K is the most significant at the separated shear layers of the cylinder pair. With Re in- creases, the length of the wake is shorter and the vortex shedding generally exhibits a symmetrical distribution for θi〈θcrit. It is also shown that the unsteady vortex shedding can be suppressed by rotating the cylinders in the counter-rotating mode.展开更多
This paper presents a novel numerical model using a fully three-dimensional(3D),incompressible,two-phase flow NavierStokes(NS)solver,which are discretized by the finite volume method.A high-resolution STACS-VOF method...This paper presents a novel numerical model using a fully three-dimensional(3D),incompressible,two-phase flow NavierStokes(NS)solver,which are discretized by the finite volume method.A high-resolution STACS-VOF method is used to capture the interface between the air and water phases.The validity of the simulation following this model is examined through3D shear flow and collapsing cylinder of water.Then,this proposed model is adopted to simulate the dynamics of flow involved with surge bore propagating over a slope in the swash zone.The computed uprush shoreline motion and the tip of runup water surface agreed well with experimental data,which indicates that this model can describe the aerated flow accurately.Numerical analyses are also applied to the spatial and temporal distributions of free-surface,instantaneous flow field,and maximal bed shear stress in the bore collapse,uprush and backwash processes.The results from the analyses reveal that the flow dynamics is complicated after the bore breaks,and the proposed model can well capture the structure characteristics of sheet flow,which are better than the previous results.All these findings are of help to understand the pattern of sediment transport and coastal evolution in the swash zone.展开更多
文摘In practical engineering,only pressure sensors are allowed to install to detect leakage in most of oil transportation pipelines,while flowmeters are only installed at the toll ports.For incompressible fluid,the leakage rate and amount cannot be accurately calculated through critical pressure conditions.In this paper,a micro-element body of the pipeline was intercepted for calculation.The relationship between radial displacement and pressure of pipe wall was studied based on the stress-strain equation.Then,the strain response of pipeline volume with pipeline pressure was obtained.The change in volume expansion of pipeline was used to characterize leakage of incompressible fluid.Finally,the calculation model of leakage amount of incompressible fluid was obtained.To verify the above theory,the pipeline expansion model under pressure was established by COMSOL software for simulation.Both simulation results and deduction equations show that the volumetric change has a quadratic parabolic relationship with the change of pipeline pressure.However,the relationship between them can be approximately linear when the pressure change is not too large.In addition,the leakage of incompressible fluid under the pressure of 0 MPa-0.8 MPa was obtained by experiments.The experimental results verify the linear relationship between leakage of incompressible fluid and the change of pipeline pressure.The theoretical and experimental results provide a basis for the calculation of leakage of incompressible fluid in the pipeline.
基金supported by National Natural Science Foundation of China(51579224)Zhejiang Province Key Science and Technology Innovation Team Project(2013TD18)Zhejiang Province Science and Technology Plan Project(2017C34007)
文摘Flow around two rotating side-by-side circular cylinders of equal diameter D is numerically studied at the Rey- nolds number 40〈 Re 〈200 and various rotation rate 8i. The incoming flow is assumed to be two-dimensional laminar flow. The governing equations are the incompressible Navier-Stokes equations and solved by the finite volume method （FVM）. The ratio of the center-to-center spacing to the cylinder diameter is T/D=2. The objective of the present work is to investigate the effect of rotational speed and Reynolds number on the stability of the flow. The simulation results are compared with the experimental data and a good agreement is achieved. The stability of the flow is analyzed by using the energy gradient theory, which produces the energy gradient function K to identify the region where the flow is the most prone to be destabilized and the degree of the destabilization. Numerical results reveal that K is the most significant at the separated shear layers of the cylinder pair. With Re in- creases, the length of the wake is shorter and the vortex shedding generally exhibits a symmetrical distribution for θi〈θcrit. It is also shown that the unsteady vortex shedding can be suppressed by rotating the cylinders in the counter-rotating mode.
基金supported by the National Natural Science Foundation of China(Grant Nos.51239001,51179015,41176072)
文摘This paper presents a novel numerical model using a fully three-dimensional(3D),incompressible,two-phase flow NavierStokes(NS)solver,which are discretized by the finite volume method.A high-resolution STACS-VOF method is used to capture the interface between the air and water phases.The validity of the simulation following this model is examined through3D shear flow and collapsing cylinder of water.Then,this proposed model is adopted to simulate the dynamics of flow involved with surge bore propagating over a slope in the swash zone.The computed uprush shoreline motion and the tip of runup water surface agreed well with experimental data,which indicates that this model can describe the aerated flow accurately.Numerical analyses are also applied to the spatial and temporal distributions of free-surface,instantaneous flow field,and maximal bed shear stress in the bore collapse,uprush and backwash processes.The results from the analyses reveal that the flow dynamics is complicated after the bore breaks,and the proposed model can well capture the structure characteristics of sheet flow,which are better than the previous results.All these findings are of help to understand the pattern of sediment transport and coastal evolution in the swash zone.
