Locomotion of a self-propulsive pitching plate in a quiescent viscous fluid

2020 ◽  
pp. 095440622090333
Author(s):  
Li Wang
Keyword(s):  
Viscous Fluid ◽  
Leading Edge ◽  
Immersed Boundary ◽  
Flexible Plate ◽  
Bending Rigidity ◽  
Pitching Motion ◽  
Fluid Mass ◽  
Boltzmann Method ◽  
Ib Method ◽  
Insight Into

The locomotion of a flexible plate pitching in a quiescent viscous fluid is numerically studied by using the lattice Boltzmann method (LBM) for the fluid and a finite element method (FEM) for the plate, with an immersed boundary (IB) method for the fluid–structure interaction (FSI). In the simulation, the leading edge of the plate undergoes a prescribed pitching motion, and the entire plate moves freely due to the fluid–plate interaction. The effects of the pitching amplitude, bending rigidity, plate-to-fluid mass ratio and Reynolds number on the propulsive performance of the flexible plate are examined in a range of parameters. The numerical results show that a certain flexibility can remarkably improve the propulsive speed and efficiency. The optimal parameters for the pitching plate are obtained, i.e. [Formula: see text] ([Formula: see text] is a non-dimensional frequency, with [Formula: see text] means rigid plate and larger [Formula: see text] means more flexible) and 20° ≤  α0 ≤ 25° ( α0 is the pitching amplitude). The comparisons of three plate-to-fluid mass ratios (1.0, 2.5 and 5.0) show that the mass of the plate decreases the propulsive speed, but contrarily increases the efficiency. The results obtained in the present study provide an insight into the understanding of the performance of self-propulsive plate in pitching motion and can further guide the engineering design of micro aerial vehicles.

Benchmark numerical solutions for two-dimensional fluid–structure interaction involving large displacements with the deforming-spatial-domain/stabilized space–time and immersed boundary–lattice Boltzmann methods

2017 ◽  
Vol 232 (14) ◽  
pp. 2500-2514 ◽  
Author(s):  
Yuan-Qing Xu ◽  
Yan-Qun Jiang ◽  
Jie Wu ◽  
Yi Sui ◽  
Fang-Bao Tian
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Fluid Structure Interaction ◽  
Spatial Domain ◽  
Space Time ◽  
Immersed Boundary ◽  
Flexible Plate ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Boltzmann Method

Body-fitted and Cartesian grid methods are two typical types of numerical approaches used for modelling fluid–structure interaction problems. Despite their extensive applications, there is a lack of comparing the performance of these two types of approaches. In order to do this, the present paper presents benchmark numerical solutions for two two-dimensional fluid–structure interaction problems: flow-induced vibration of a highly flexible plate in an axial flow and a pitching flexible plate. The solutions are obtained by using two partitioned fluid–structure interaction methods including the deforming-spatial-domain/stabilized space–time fluid–structure interaction solver and the immersed boundary–lattice Boltzmann method. The deforming-spatial-domain/stabilized space–time fluid–structure interaction solver employs the body-fitted-grid deforming-spatial-domain/stabilized space–time method for the fluid motions and the finite-difference method for the structure vibrations. A new mesh update strategy is developed to prevent severe mesh distortion in cases where the boundary does not oscillate periodically or needs a long time to establish a periodic motion. The immersed boundary–lattice Boltzmann method uses lattice Boltzmann method as fluid solver and the same finite-difference method as structure solver. In addition, immersed boundary method is used in the immersed boundary–lattice Boltzmann solver to handle the fluid–structure interaction coupling. Results for the characteristic force coefficients, tail position, plate deformation pattern and the vorticity fields are presented and discussed. The present results will be useful for evaluating the performance and accuracy of existing and new numerical methodologies for fluid–structure interaction.

EFFECT OF MEMBRANE BENDING STIFFNESS ON THE DEFORMATION OF ELASTIC CAPSULES IN EXTENSIONAL FLOW: A LATTICE BOLTZMANN STUDY

2007 ◽  
Vol 18 (08) ◽  
pp. 1277-1291 ◽  
Author(s):  
Y. SUI ◽  
Y. T. CHEW ◽  
P. ROY ◽  
H. T. LOW
Keyword(s):  
Lattice Boltzmann ◽  
Present Model ◽  
Extensional Flow ◽  
Bending Stiffness ◽  
Immersed Boundary ◽  
Two Dimensional ◽  
Bending Rigidity ◽  
Elastic Membranes ◽  
Membrane Bending ◽  
Boltzmann Method

The transient deformation of liquid capsules enclosed by elastic membranes in two-dimensional extensional flow is studied numerically, using an improved immersed boundary-lattice Boltzmann method. The purpose of the present study is to investigate the effect of interfacial bending stiffness on the deformation of such capsules, under the subcritical elasticity capillary number conditions. The present model can simulate flow-induced deformation of capsules with arbitrary resting shapes (concerning the in-plane tension) and bending-free configurations. The deformation of capsules with initially circular, elliptical, and biconcave resting shapes was investigated in the present study; the capsules' bending-free configurations were considered as either circular shapes or their initially resting shapes. The results show that for capsules with bending-free configuration as circles, membrane bending rigidity has significant rounding effect on the steady deformed profiles. For elliptical and biconcave capsules with resting shapes as the bending-free configurations, it is found that with the bending stiffness increasing, the capsules' steady shapes are more akin to their initial shapes.

Locomotion of a passively flapping flat plate

2010 ◽  
Vol 659 ◽  
pp. 43-68 ◽  
Author(s):  
JIE ZHANG ◽  
NAN-SHENG LIU ◽  
XI-YUN LU
Keyword(s):  
Flat Plate ◽  
Vortical Structure ◽  
Leading Edge ◽  
Periodic Flow ◽  
Flexible Plate ◽  
Forward Movement ◽  
Propulsion Systems ◽  
Near Wake ◽  
Boltzmann Method ◽  
Flow States

Locomotion of a passively flapping flat plate has been studied numerically by means of a multiblock lattice Boltzmann method. A flexible plate is modelled by a rigid plate with a torsion spring acting about the pivot at the leading edge of the plate. A dynamic model of this kind is called a lumped-torsional-flexibility model. When the leading edge is forced to heave sinusoidally, the plate pitches passively and propels itself in the horizontal direction as a result of the fluid–plate interaction. We have investigated various aspects of the mechanics behind the behaviour of the flapping plate, including the periodic- and non-periodic-flow states, the spontaneous motion of the plate, vortical structure and how they compare to similar propulsion systems in animals. In the periodic-flow regime, two dynamical responses of the passively pitching plate (forward and backward movements) are observed. Which movement will occur depends only on the frequency ratio F of the natural frequency of the system and the heaving frequency associated with the lumped torsional flexibility. It is found that the plate will select the forward movement when F > 1 and the backward movement when F ≤ 1. In the forward-movement regime, analysis of the dynamical behaviours and propulsive properties of the passively pitching plate indicates that the torsional flexibility can remarkably improve the propulsive performance. In addition, four kinds of vortex structures in the near wake are identified, which mainly depend on the forward speed of the plate. Finally the forward movement is compared to the flapping-based locomotion of swimming and flying animals. The results obtained in this study are consistent with the observations and measurements of swimming and flying animals; thus, they may provide physical insights into understanding of the propulsive mechanisms of the flapping wings and fins of animals.

Interaction of two tandem deformable bodies in a viscous incompressible flow

2009 ◽  
Vol 635 ◽  
pp. 455-475 ◽  
Author(s):  
LUODING ZHU
Keyword(s):  
Mass Density ◽  
Reynolds Numbers ◽  
Separation Distance ◽  
Rigid Bodies ◽  
Immersed Boundary ◽  
Bending Rigidity ◽  
Static State ◽  
Mainstream Flow ◽  
Deformable Bodies ◽  
Ib Method

Previous laboratory measurements on drag of tandem rigid bodies moving in viscous incompressible fluids found that a following body experienced less drag than a leading one. Very recently a laboratory experiment (Ristroph & Zhang, Phys. Rev. Lett., vol. 101, 2008) with deformable bodies (rubble threads) revealed just the opposite – the leading body had less drag than the following one. The Reynolds numbers in the experiment were around 104. To find out how this qualitatively different phenomenon may depend on the Reynolds number, a series of numerical simulations are designed and performed on the interaction of a pair of tandem flexible flags separated by a dimensionless vertical distance (0 ≤ D ≤ 5.5) in a flowing viscous incompressible fluid at lower Reynolds numbers (40 ≤ Re ≤ 220) using the immersed boundary (IB) method. The dimensionless bending rigidity b and dimensionless flag mass density used in our work are as follows: 8.6 × 10−5 ≤ b ≤ 1.8 × 10−3, 0.8 ≤ ≤ 1.0. We obtain an interesting result within these ranges of dimensionless parameters: when Re is large enough so that the flapping of the two flags is self-sustained, the leading flag has less drag than the following one; when Re is small enough so that the flags maintain two nearly static line segments aligned with the mainstream flow, the following flag has less drag than the leading one. The transitional range of Re separating the two differing phenomena depends on the value of b. With Re in this range, both the flapping and static states are observed depending on the separation distance D. When D is small enough, the flags are in the static state and the following flag has less drag; when D is large enough the flags are in the constant flapping state and the leading flag has less drag. The critical value of D depends on b.

Dynamics of fluid flow over a circular flexible plate

2014 ◽  
Vol 759 ◽  
pp. 56-72 ◽  
Author(s):  
Ru-Nan Hua ◽  
Luoding Zhu ◽  
Xi-Yun Lu
Keyword(s):  
Fluid Flow ◽  
Plate Motion ◽  
Immersed Boundary ◽  
Flexible Plate ◽  
Fluid Structure ◽  
Structure System ◽  
Elastic Potential Energy ◽  
Boltzmann Method ◽  
Deformation Patterns ◽  
Deformation Modes

AbstractThe dynamics of viscous fluid flow over a circular flexible plate are studied numerically by an immersed boundary–lattice Boltzmann method for the fluid flow and a finite-element method for the plate motion. When the plate is clamped at its centre and placed in a uniform flow, it deforms by the flow-induced forces exerted on its surface. A series of distinct deformation modes of the plate are found in terms of the azimuthal fold number from axial symmetry to multifold deformation patterns. The developing process of deformation modes is analysed and both steady and unsteady states of the fluid–structure system are identified. The drag reduction due to the plate deformation and the elastic potential energy of the flexible plate are investigated. Theoretical analysis is performed to elucidate the deformation characteristics. The results obtained in this study provide physical insight into the understanding of the mechanisms on the dynamics of the fluid–structure system.

scholarly journals A numerical study of fish adaption behaviors in complex environments with a deep reinforcement learning and immersed boundary–lattice Boltzmann method

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yi Zhu ◽  
Fang-Bao Tian ◽  
John Young ◽  
James C. Liao ◽  
Joseph C. S. Lai
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Prey Capture ◽  
Numerical Study ◽  
Benchmark Problems ◽  
Immersed Boundary ◽  
Complex Environments ◽  
Fish Model ◽  
Point To Point ◽  
Boltzmann Method

AbstractFish adaption behaviors in complex environments are of great importance in improving the performance of underwater vehicles. This work presents a numerical study of the adaption behaviors of self-propelled fish in complex environments by developing a numerical framework of deep learning and immersed boundary–lattice Boltzmann method (IB–LBM). In this framework, the fish swimming in a viscous incompressible flow is simulated with an IB–LBM which is validated by conducting two benchmark problems including a uniform flow over a stationary cylinder and a self-propelled anguilliform swimming in a quiescent flow. Furthermore, a deep recurrent Q-network (DRQN) is incorporated with the IB–LBM to train the fish model to adapt its motion to optimally achieve a specific task, such as prey capture, rheotaxis and Kármán gaiting. Compared to existing learning models for fish, this work incorporates the fish position, velocity and acceleration into the state space in the DRQN; and it considers the amplitude and frequency action spaces as well as the historical effects. This framework makes use of the high computational efficiency of the IB–LBM which is of crucial importance for the effective coupling with learning algorithms. Applications of the proposed numerical framework in point-to-point swimming in quiescent flow and position holding both in a uniform stream and a Kármán vortex street demonstrate the strategies used to adapt to different situations.

scholarly journals Research on Human Erythrocyte’s Threshold Free Energy for Hemolysis and Damage from Coupling Effect of Shear and Impact Based on Immersed Boundary-Lattice Boltzmann Method

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Zhong Yun ◽  
Chuang Xiang ◽  
Liang Wang
Keyword(s):  
Free Energy ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Coupling Effect ◽  
Threshold Value ◽  
Blood Pump ◽  
Immersed Boundary ◽  
Threshold Limit ◽  
Spring Network Model ◽  
Boltzmann Method

Researches on the principle of human red blood cell’s (RBC) injuring and judgment basis play an important role in decreasing the hemolysis in a blood pump. In the current study, the judgment of hemolysis in a blood pump study was through some experiment data and empirical formula. The paper forms a criterion of RBC’s mechanical injury in the aspect of RBC’s free energy. First, the paper introduces the nonlinear spring network model of RBC in the frame of immersed boundary-lattice Boltzmann method (IB-LBM). Then, the shape, free energy, and time needed for erythrocyte to be shorn in different shear flow and impacted in different impact flow are simulated. Combining existing research on RBC’s threshold limit for hemolysis in shear and impact flow with this paper’s, the RBC’s free energy of the threshold limit for hemolysis is found to be 3.46 × 10 − 15  J. The threshold impact velocity of RBC for hemolysis is 8.68 m/s. The threshold value of RBC can be used for judgment of RBC’s damage when the RBC is having a complicated flow of blood pumps such as coupling effect of shear and impact flow. According to the change law of RBC’s free energy in the process of being shorn and impacted, this paper proposed a judging criterion for hemolysis when the RBC is under the coupling effect of shear and impact based on the increased free energy of RBC.

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