• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.97-102
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• 2009

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 ${\tao}_T$ scales with the chain length N as ${{\tau}_T}^{\propto}N^{\alpha}$. The value of scaling exponents($\alpha$) obtained from our simulations are $1.29{\pm}0.03$ and $1.41{\pm}0.03$, with and without hydrodynamic interactions, respectively. Our simulation results are in good agreement with the experimentally observed value of $\alpha$, which is equal to $1.27{\pm}0.03$, particularly when hydrodynamic interaction effects are taken into account.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권1호
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• pp.1-8
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• 2012

The hydrodynamic interaction between ship and bank can't be neglected when a vessel is app- roached toward the tip of a wedge-shaped bank in restricted waterways, such as in a harbor, near some fixed obstacles, or in a narrow channel. In this paper, the characteristic features of the hydrodynamic interaction acting on a slowly moving vessel in the proximity of a wedge-shaped bank are described and illustrated, and the effects of water depth and the spacing between ship and wedge-shaped bank are summarized and discussed based on the slender body theory. From the theoretical results, it indicated that the hydrodynamic interactions decrease as wedge-shaped bank of angle ${\beta}$ in-creases. For water depth to draft ratio less than about 2.0, the hydrodynamic interactions between ship and bank in-crease sharply as h/d decreases, regardless of the wedge-shaped bank of angle ${\beta}$. Also, for lateral separation more than about 0.2L between ship and wedge-shaped bank, it can be concluded that the bank effects decrease largely as the separation increases.

• 대한조선학회지
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• 제24권1호
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• pp.29-34
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• 1987

In this paper, a three dimensional singularity distribution method is applied to investigate the hydrodynamic interactions between two barges floating on a free surface of a deep water. The results show that the hydrodynamic interaction forces are important in the calculation responses of two barges floating in each other's vicinity. Furthermore the trends of hydrodynamic forces due to the motion of body itself are different from those of a single barged, and the motions of the seaward barge can sometimes exceed those of the seaward barged.

• Korea-Australia Rheology Journal
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• 제20권3호
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• pp.143-152
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• 2008

Simulations of solutions of flexible polymer molecules during flow in simple or complex confined geometries are performed. Concentrations from ultradilute up to near the overlap concentration are considered. As concentration increases, the hydrodynamic migration effects observed in dilute solution unidirectional flows (Couette flow, Poiseuille flow) become less prominent, virtually vanishing as the overlap concentration is approached. In a grooved channel geometry, the groove is almost completely depleted of polymer chains at high Weissenberg number in the dilute limit, but at finite concentration this depletion effect is dramatically reduced. Only upon inclusion of hydrodynamic interactions can these phenomena be properly captured.

• 한국해양공학회지
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• 제35권2호
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• pp.99-112
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• 2021

The prediction of maneuverability is very important in the design process of an underwater vehicle. In this study, we predicted the steady turning ability of a symmetrical underwater vehicle while considering interactions between the yaw rate and drift/rudder angle through a simulation-based methodology. First, the hydrodynamic force and moment, including coupled derivatives, were obtained by computational fluid dynamics (CFD) simulations. The feasibility of CFD results were verified by comparing static drift/rudder simulations to vertical planar motion mechanism (VPMM) tests. Turning motion simulations were then performed by solving 2-degree-of-freedom (DOF) equations with CFD data. The turning radius, drift angle, advance, and tactical diameter were calculated. The results show good agreement with sea trial data and the effects on the turning characteristics of coupled interaction terms, especially between the yaw rate and drift angle.

• 천문학회지
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• 제54권2호
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• pp.71-88
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• 2021

We use N-body/hydrodynamic simulations to study the evolution of the spin of a Milky Way-like galaxy through interactions. We perform a controlled experiment of co-planar galaxy-galaxy encounters and study the evolution of disk spins of interacting galaxies. Specifically, we consider cases where the late-type target galaxy encounters an equally massive companion galaxy, which has either a late or an early-type morphology, with a closest approach distance of about 50 kpc, in prograde or retrograde sense. By examining the time change of the circular velocity of the disk material of the target galaxy from each case, we find that the target galaxy tends to lose the spin through prograde collisions but hardly through retrograde collisions, regardless of the companion galaxy type. The decrease of the spin results mainly from the deflection of the orbit of the disk material by tidal disruption. Although there is some disk material which gains the circular velocity through hydrodynamic as well as gravitational interactions or by transferring material from the companion galaxy, it turns out that the amount of the material is generally insufficient to increase the overall galactic spin under the conditions we set. We find that the spin angular momentum of the target galaxy disk decreases by 15-20% after a prograde collision. We conclude that the accumulated effects of galaxy-galaxy interactions will play an important role in determining the total angular momentum of late-type galaxies.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권1호
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• pp.77-99
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• 2017

Offshore oscillating water columns (OWC) represent one of the most promising forms of wave energy converters. The hydrodynamic performance of such converters heavily depends on their interactions with ocean waves; therefore, understanding these interactions is essential. In this paper, a fully nonlinear 2D computational fluid dynamics (CFD) model based on RANS equations and VOF surface capturing scheme is implemented to carry out wave energy balance analyses for an offshore OWC. The numerical model is well validated against published physical measurements including; chamber differential air pressure, chamber water level oscillation and vertical velocity, overall wave energy extraction efficiency, reflected and transmitted waves, velocity and vorticity fields (PIV measurements). Following the successful validation work, an extensive campaign of numerical tests is performed to quantify the relevance of three design parameters, namely incoming wavelength, wave height and turbine damping to the device hydrodynamic performance and wave energy conversion process. All of the three investigated parameters show important effects on the wave-pneumatic energy conversion chain. In addition, the flow field around the chamber's front wall indicates areas of energy losses by stronger vortices generation than the rear wall.

• Korea-Australia Rheology Journal
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• 제21권4호
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• pp.245-268
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• 2009

Recent developments in dilute polymer solution rheology are reviewed, and placed within the context of the general goals of predicting the complex flow of complex fluids. In particular, the interplay between the use of polymer kinetic theory and continuum mechanics to advance the microscopic and the macroscopic description, respectively, of dilute polymer solution rheology is delineated. The insight that can be gained into the origins of the high Weissenberg number problem through an analysis of the configurational changes undergone by a single molecule at various locations in the flow domain is discussed in the context of flow around a cylinder confined between flat plates. The significant role played by hydrodynamic interactions as the source of much of the richness of the observed rheological behaviour of dilute polymer solutions is highlighted, and the methods by which this phenomenon can be incorporated into a macroscopic description through the use of closure approximations and multi scale simulations is discussed.

• 한국식품과학회지
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• 제25권3호
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• pp.277-281
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• 1993

콜로이드 식품에서의 단백질의 구조적 안정성을 연구하기 위하여 7개의 BSA structural intermediates, succinylated ${\beta}-lactoglobulin$을 만든 후 CD, 이황화물 결합함량, hydrodynamic radius 등을 측정하여 그 구조적 특성을 규명했다. Refolding time이 길수록 BSA intermediates들은 native BSA 구조에 근접하는 것을 나타냈고 succinylation은 ${\beta}-lactoglobulin$의 순 음전하를 변화시켜 보다 aperiodic structure를 갖게하였다. Perchlorate 존재하 ${\beta}-casein$의 구조는 소수성 상호작용에 크게 영향 받는 것으로 나타났다.

• Ocean Systems Engineering
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• 제3권4호
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• pp.275-294
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• 2013

Side-by-side offloading operations are widely utilized in engineering practice. The hydrodynamic interactions between two vessels play a crucial role in safe operation. This study focuses on the coupled effects between two floating bodies positioned side-by-side as a shuttle tanker-FPSO (floating production, storage and offloading) system. Several wave directions with different side-by-side distances are studied in order to obtain the variation tendency of the horizontal hydrodynamic coefficients, motion responses and mean drift forces. It is obtained that the coupled hydrodynamics between two vessels is evidently distinguished from the single body case with shielding and exaggerating effects, especially for sway and yaw directions. The resonance frequency and the peak amplitude are closely related with side-by-side separation distance. In addition, the horizontal hydrodynamics of the shuttle tanker is more susceptible to coupled effects in beam waves. It is suggested to expand the gap distance reasonably in order to reduce the coupled drift forces effectively. Attention should also be paid to the second peaks caused by hydrodynamic coupling. Since the horizontal mean drift forces are the most mainly concerned forces to be counteracted in dynamic positioning (DP) system and mooring system, prudent prediction is beneficial in saving consumed power of DP system and reducing tension of mooring lines.