Problems involving fluid flexible-structure interactions(FFSI)are ubiquitous in engineering and sciences.Peskin’s immersed boundary(IB)method is the first framework for modeling and simulation of such problems.This p...Problems involving fluid flexible-structure interactions(FFSI)are ubiquitous in engineering and sciences.Peskin’s immersed boundary(IB)method is the first framework for modeling and simulation of such problems.This paper addresses a three-dimensional extension of the IB framework for non-Newtonian fluids which include power-law fluid,Oldroyd-B fluid,and FENE-P fluid.The motion of the non-Newtonian fluids are modelled by the lattice Boltzmann equations(D3Q19 model).The differential constitutive equations of Oldroyd-B and FENE-P fluids are solved by the D3Q7 model.Numerical results indicate that the new method is first-order accurate and conditionally stable.To show the capability of the new method,it is tested on three FFSI toy problems:a power-law fluid past a flexible sheet fixed at its midline,a flexible sheet being flapped periodically at its midline in an Oldroyd-B fluid,and a flexible sheet being rotated at one edge in a FENE-P fluid.展开更多
Fluid-structure-interaction （FSI） phenomenon is common in science and engineering. The fluidinvolved in an FSI problem may be non-Newtonian such as blood. A popular framework for FSIproblems is Peskin’s imm...Fluid-structure-interaction （FSI） phenomenon is common in science and engineering. The fluidinvolved in an FSI problem may be non-Newtonian such as blood. A popular framework for FSIproblems is Peskin’s immersed boundary （IB） method. However, most of the IB formulations arebased on Newtonian fluids. In this letter, we report an extension of the IB framework to FSIinvolving Oldroyd-B and FENE-P fluids in three dimensions using the lattice Boltzmann approach.The new method is tested on two FSI model problems. Numerical experiments show that themethod is conditionally stable and convergent with the first order of accuracy.展开更多
This paper aims to study the numerical features of a coupling scheme between the immersed boundary(IB)method and the lattice Boltzmann BGK(LBGK)model by four typical test problems:the relaxation of a circular membrane...This paper aims to study the numerical features of a coupling scheme between the immersed boundary(IB)method and the lattice Boltzmann BGK(LBGK)model by four typical test problems:the relaxation of a circular membrane,the shearing flow induced by a moving fiber in the middle of a channel,the shearing flow near a non-slip rigid wall,and the circular Couette flow between two inversely rotating cylinders.The accuracy and robustness of the IB-LBGK coupling scheme,the performances of different discrete Dirac delta functions,the effect of iteration on the coupling scheme,the importance of the external forcing term treatment,the sensitivity of the coupling scheme to flow and boundary parameters,the velocity slip near non-slip rigid wall,and the origination of numerical instabilities are investigated in detail via the four test cases.It is found that the iteration in the coupling cycle can effectively improve stability,the introduction of a second-order forcing term in LBGK model is crucial,the discrete fiber segment length and the orientation of the fiber boundary obviously affect accuracy and stability,and the emergence of both temporal and spatial fluctuations of boundary parameters seems to be the indication of numerical instability.These elaborate results shed light on the nature of the coupling scheme and may benefit those who wish to use or improve the method.展开更多
Fluid-structure-interaction problems are ubiquitous,complicated,and not yet well understood.In this paper we investigate the interaction of a leading rigid circular cylinder and a trailing compliant filament and analy...Fluid-structure-interaction problems are ubiquitous,complicated,and not yet well understood.In this paper we investigate the interaction of a leading rigid circular cylinder and a trailing compliant filament and analyze the dynamic responses of the filament in the wake of the cylinder.It is revealed that there exist two flapping states of the filament depending on the cylinder-filament separation distance and the relevant critical distance distinguishing the two states is associated with the Reynolds number and the filament length.It is also found that the drag coefficient of the cylinder is reduced but that of the filament may be increased or decreased depending on its length.Compared with a single filament in a uniform flow,the filament of the same mechanical properties flapping in the wake of the cylinder has a lower frequency and a greater amplitude.展开更多
基金The work is supported by the US National Science Foundation(NSF)through the research grant DMS-1522554We thank the unknown Reviewers for their helpful suggestions and comments which have helped us.
文摘Problems involving fluid flexible-structure interactions(FFSI)are ubiquitous in engineering and sciences.Peskin’s immersed boundary(IB)method is the first framework for modeling and simulation of such problems.This paper addresses a three-dimensional extension of the IB framework for non-Newtonian fluids which include power-law fluid,Oldroyd-B fluid,and FENE-P fluid.The motion of the non-Newtonian fluids are modelled by the lattice Boltzmann equations(D3Q19 model).The differential constitutive equations of Oldroyd-B and FENE-P fluids are solved by the D3Q7 model.Numerical results indicate that the new method is first-order accurate and conditionally stable.To show the capability of the new method,it is tested on three FFSI toy problems:a power-law fluid past a flexible sheet fixed at its midline,a flexible sheet being flapped periodically at its midline in an Oldroyd-B fluid,and a flexible sheet being rotated at one edge in a FENE-P fluid.
基金the US National Science Foundation (DMS-1522554) for the support
文摘Fluid-structure-interaction （FSI） phenomenon is common in science and engineering. The fluidinvolved in an FSI problem may be non-Newtonian such as blood. A popular framework for FSIproblems is Peskin’s immersed boundary （IB） method. However, most of the IB formulations arebased on Newtonian fluids. In this letter, we report an extension of the IB framework to FSIinvolving Oldroyd-B and FENE-P fluids in three dimensions using the lattice Boltzmann approach.The new method is tested on two FSI model problems. Numerical experiments show that themethod is conditionally stable and convergent with the first order of accuracy.
基金the National Natural Science Foundation of China(NSFC,Grant numbers 10572106,10872153 and 11172219)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130141110013)。
文摘This paper aims to study the numerical features of a coupling scheme between the immersed boundary(IB)method and the lattice Boltzmann BGK(LBGK)model by four typical test problems:the relaxation of a circular membrane,the shearing flow induced by a moving fiber in the middle of a channel,the shearing flow near a non-slip rigid wall,and the circular Couette flow between two inversely rotating cylinders.The accuracy and robustness of the IB-LBGK coupling scheme,the performances of different discrete Dirac delta functions,the effect of iteration on the coupling scheme,the importance of the external forcing term treatment,the sensitivity of the coupling scheme to flow and boundary parameters,the velocity slip near non-slip rigid wall,and the origination of numerical instabilities are investigated in detail via the four test cases.It is found that the iteration in the coupling cycle can effectively improve stability,the introduction of a second-order forcing term in LBGK model is crucial,the discrete fiber segment length and the orientation of the fiber boundary obviously affect accuracy and stability,and the emergence of both temporal and spatial fluctuations of boundary parameters seems to be the indication of numerical instability.These elaborate results shed light on the nature of the coupling scheme and may benefit those who wish to use or improve the method.
基金the National Natural Science Foundation of China(Grant No.11372304)and the 111 Project(Grant No.B07033)。
文摘Fluid-structure-interaction problems are ubiquitous,complicated,and not yet well understood.In this paper we investigate the interaction of a leading rigid circular cylinder and a trailing compliant filament and analyze the dynamic responses of the filament in the wake of the cylinder.It is revealed that there exist two flapping states of the filament depending on the cylinder-filament separation distance and the relevant critical distance distinguishing the two states is associated with the Reynolds number and the filament length.It is also found that the drag coefficient of the cylinder is reduced but that of the filament may be increased or decreased depending on its length.Compared with a single filament in a uniform flow,the filament of the same mechanical properties flapping in the wake of the cylinder has a lower frequency and a greater amplitude.
