A coupled immersed boundary-lattice Boltzmann method and its simulation for biomimetic problems

A coupled immersed boundary-lattice Boltzmann method （IB-LBM） is introduced to solve biomimetic problems. Compared to the conventional IB-LBM, the strict satisfaction of no-slip boundary condition is implemented in the current method. Consequently, the phenomenon of flow penetration that is frequently observed in the conventional IB-LBM is fully prevented, and subsequently the force on the boundary can be calculated more accurately. This feature is of importance for the simulation of biomimetic problems. Moreover, by applying the relationship between the velocity correction and forcing term, the boundary force can be calculated easily. Several biomimetic problems are then simulated. Based on the good agreement between the current results and those in the literature, it may be concluded that the present IB-LBM has the capabilitv to handle various biomimetic oroblems.

An Immersed Boundary-Lattice Boltzmann Prediction for Particle Hydrodynamic Focusing in Annular Microchannels

We numerically study the dynamics of particle crystals in annular microchannels by the immersed-boundary（IB）lattice Boltzmann（LB） coupled model, analyze the fluid-particle interactions during the migration of particles,and reveal the underlying mechanism of a particle focusing on the presence of fluid flows. The results show that the Reynolds and Dean numbers are key factors influencing the hydrodynamics of particles. The particles migrate onto their equilibrium tracks by adjusting the Reynolds and Dean numbers. Elliptical tracks of particles during hydrodynamic focusing can be predicted by the IB-LB model. Both the small Dean number and the small particle can lead to a small size of the focusing track. This work would possibly facilitate the utilization of annular microchannel flows to obtain microfluidic flowing crystals for advanced applications in biomedicine and materials synthesis.

A Robust Immersed Boundary-Lattice Boltzmann Method for Simulation of Fluid-Structure Interaction Problems

A robust immersed boundary-lattice Boltzmann method(IB-LBM)is proposed to simulate fluid-structure interaction(FSI)problems in this work.Compared with the conventional IB-LBM,the current method employs the fractional step technique to solve the lattice Boltzmann equation(LBE)with a forcing term.Consequently,the non-physical oscillation of body force calculation,which is frequently encountered in the traditional IB-LBM,is suppressed greatly.It is of importance for the simulation of FSI problems.In the meanwhile,the no-slip boundary condition is strictly satisfied by using the velocity correction scheme.Moreover,based on the relationship between the velocity correction and forcing term,the boundary force can be calculated accurately and easily.A few test cases are first performed to validate the current method.Subsequently,a series of FSI problems,including the vortex-induced vibration of a circular cylinder,an elastic filament flapping in the wake of a fixed cylinder and sedimentation of particles,are simulated.Based on the good agreement between the current results and those in the literature,it is demonstrated that the proposed IB-LBMhas the capability to handle various FSI problems effectively.

Hydrodynamic Characteristics of Square Heaving Plates with Opening Under Forced Oscillation

The existence of the heaving plates can improve the heaving motion performance of an offshore structure significantly by providing both extra added mass and damping.In the current research,numerical investigation is carried out on the hydrodynamic characteristics of both isolated square heaving plate and double square heaving plates with opening by an immersed boundary-lattice Boltzmann method.The effects on hydrodynamic performance of plates due to Keulegan-Carpenter(KC)number,frequency number,opening ratio,opening distribution and spacing of plates are examined.It is found that the heaving plates with optimized opening ratio can provide additional damping compared with the plates without opening.Better hydrodynamic characteristics of double plates can be obtained with the increase of plate spacing.

NUMERICAL ANALYSIS OF THE GROUND EFFECT ON INSECT HOVERING

The ground effect on insect hovering is investigated using an immersed boundary-lattice Boltzmann method to solve the two-dimensional incompressible Navier-Stokes equations. A virtual model of an elliptic foil with oscillating translation and rotation near a ground is used. The objective of this study is to deal with the ground effect on the unsteady forces and vortical structures and to get the physical insights in the relevant mechanisms. Two typical insect hovering modes, i.e., normal and dragonfly hovering mode, are examined. Systematic computations have been carried out for some parameters, and the ground effect on the unsteady forces and vortical structures is analyzed.

Numerical Investigation of the Dynamics of a Flexible Filament in the Wake of Cylinder

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.