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ALAPATI SURESH 한국기계기술학회 2014 한국기계기술학회지 Vol.16 No.1
The flow between two rotating concentric cylinders, also known as Taylor-Couette flow system, is one ofthe most widely studied systems in the classical fluid dynamics. In this work, a two-dimensionalTaylor-Couette flow system is simulated using the lattice Boltzmann method combined with the smoothedprofile method. The fluid flow between the rotating cylinders is solved by lattice Boltzmann equation whilethe curved boundaries of the cylinders are treated with a smoothed profile function. To assess the validity ofthe present simulation technique, three different cases of rotation of the cylinders were considered: ⅰ) innercylinder is only rotating, ⅱ) outer cylinder is only rotating, and ⅲ) both inner and outer cylinders arerotating. For all the three cases, the numerical results of the flow velocity in azimuthal direction and thehydrodynamic torque acting on the cylinders are in good agreement with the corresponding analytical solutionresults.
Suresh Alapati,제우성,서용권 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5
The main objective of this work is to explore the effect of defect location on the swimming speed of a microscopic artificial swimmer. The swimmer consists of an artificial filament composed of super-paramagnetic beads connected by elastic linkers and is modeled with aworm-like-chain configuration. To simulate the swimming motion of the filament, a load particle is attached at one end of the filament. The Rotne-Prager approximation is used to evaluate the hydrodynamic interactions between the filament and the fluid. To validate thenumerical code, we first simulated the swimming motion of the filament without defect (‘without defect’ means the bending stiffness ofthe filament is uniform along its length). Next, we simulated the swimming motion of defective filament by setting zero for the bendingstiffness value at a particular bead location. We observed that when the location of defect is on the load side of the filament, the swimmingvelocity is less than that of the defect-less filament, and vice versa. The effect of defect is more significant when it is located on theload side of the filament (The difference between the swimming velocity of defective and defect-less filament amounts to 38%) thanwhen it is on the free end side (The difference is only 7% ). We also observed that at a certain sperm number the swimming direction isreversed when the defect is located very close to the load particle.
Suresh Alapati(수레수알라파티),Sangmo Kang(강상모),Yong Kweon Suh(서용권) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.11
Translocation of biopolymers such as DNA and RNA through a nano-pore is an important process in biotechnology applications. The translocation process of a biopolymer through an artificial nano-pore in the presence of a fluid solvent is simulated. The polymer motion is simulated by Langevin molecular dynamics (MD) techniques while the solvent dynamics are taken into account by lattice-Boltzmann method (LBM). The hydrodynamic interactions are considered explicitly by coupling the polymer and solvent through the frictional and the random forces. From simulation results we found that the hydrodynamic interactions between polymer and solvent speed-up the translocation process. The translocation time τ<SUB>T</SUB> scales with the chain length N as τ<SUB>T</SUB><SUP>∝</SUP> N<SUP>α</SUP>. The value oj scaling exponents(α) obtained from our simulations are 1.29 ± 0.03 and 1.41 ± 0.03, with and without hydrodynamic interactions, respectively. Our simulation results are in good agreement with the experimentally observed value of α, which is equal to 1.27 ± 0.03, particularly when hydrodynamic interaction effects are taken into account.
Parallel computation of two-phase flow in a microchannel using the lattice Boltzmann method
Suresh Alapati,강상모,Yong Kweon Suh 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.9
We present a numerical simulation of two-phase flow in a three-dimensional cross-junction microchannel by using the lattice Boltzmann method (LBM). At first, we validated our LBM code with the velocity profile in a 3-dimensional rectangular channel. Then, we developed a lattice Boltzmann code based on the free energy model to simulate the immiscible binary fluid flow. The parallelization of the developed code is implemented on a PC cluster using the MPI program. The numerical results of two-phase flow in the microchannel reveal droplet formation process, which compares well with corresponding experimental results. The size of droplet decreases with increase of the flow-rate ratio and the capillary number. The movement of a droplet through the microchannel induces three-dimensional circulating flow inside the droplet. This complex flow is thought to enhance the mixing and reaction of reagents.
Effect of Defect Location on the Swimming Speed of a Microscopic Artificial Swimmer
Suresh Alapati,Woo Seong Che,Yong Kweon Suh 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.10
The main objective of this work is to know the effect of defect location on the swimming speed of a microscopic artificial swimmer. The swimmer consists of an artificial filament composed of super-paramagnetic beads connected by elastic linkers and is modeled with a worm-like-chain configuration. The Rotne-Prager approximation is used to evaluate the hydrodynamic interactions between the filament and the fluid. To validate our numerical code, at first, we simulated the swimming motion of the filament without defect (without defect means the bending stiffness of the filament is uniform along its length). Next, we simulated the swimming motion of defective filament by setting the bending stiffness value at a particular bead location is equal to zero. We observed that when the defect location is on the load side of the filament, the swimming velocity is less than that of the filament without defect and vice versa. We also observed that at certain sperm numbers the swimming direction is reversed when the defect location is on the load side of the filament.
Lattice Boltzmann Method과 Smoothed Profile Method을 이용한 동심원의 자연대류 시뮬레이션
Suresh Alapati 한국기계기술학회 2017 한국기계기술학회지 Vol.19 No.2
In this work, the natural convection in an annulus between two concentric cylinders is studied numerically. The fluid flow between the cylinders is solved by the lattice Boltzmann method (LBM) while a separate finite difference method (FDM) is used to solve the heat transfer. No-slip and constant boundary conditions at curved boundaries of the cylinders are treated with a smoothed profile method (SPM). At first, the velocity and temperature profiles obtained from the present LBM-SPM and FDM-SPM are validated with the corresponding theoretical results. Later, natural convection simulations inside the annulus are performed using coupled scheme of LBM-FDM-SPM by varying Ra in the range Ra=1000, Ra=10000, Ra=50000, and Ra=100000. From the temperature and fluid flow patterns obtained at different Ra, it is found that the heat transfer is mainly dominated by conduction process when Ra is low and by convection process when Ra is high.
Suresh Alapati,제우성,Madhusoodanan Mannoor,Yong Kweon Suh 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.11
In this paper, we present the results obtained from the simulation of particle motion induced by the fluid flow driven by an array of beating artificial cilia inside a micro-channel. A worm-like-chain model is used to simulate the elastic cilia, and the lattice Boltzmann equation is used to compute the fluid flow. We employ a harmonic force at the extreme tip of each cilium to actuate it. Our simulation methods are first validated by applying them to the motion of a single cilium and a freely falling sphere. After validation, we simulate the fluid flow generated by an array of beating cilia and find that a maximum flow rate is achieved at an optimum sperm number. Next, we simulate the motion of a neutrally buoyant spherical particle at this optimum sperm number by tracking the particle motion with a smoothed profile method. We address the effect of the following parameters on the particle velocity: the gap between cilia and particle, the particle size, the cilia density, and the presence of an array of intermediate particles.
Alapati, Suresh,Fernandes, Dolfred Vijay,Suh, Yong-Kweon 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.6
This paper presents a numerical study on the enhancement of mixing within a micro cavity by use of transient induced-charge electro-osmotic flows created by a periodic on-off-switching of the electric field applied across a pair of electrodes. For the first time, we demonstrate that the electro-osmotic flows observed during the charging and decharging stages are not symmetric with respect to each other and can lead to a chaotic mixing. Lyapunov exponents and particle scattering patterns are obtained for the symptom of the chaotic advection at various external fields.