• 항공우주시스템공학회지
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• 제1권2호
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• pp.37-42
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• 2007

This paper proposes a numerical modeling approach to simulate the hybrid combustion phenomena. From the physical understandings of hybrid combustion, the computational domain was separated into three regions: the solid fuel, gas phase reactive flow, and the interface between solid and fluid. Moreover, for the accurate calculation, computational grids for these regions was generated at every time step considering the instantaneous moving interface which are governed by the balance equations using thermal pyrolysis. In the domain of reactive flow, by virtue of diffusion flame structure, turbulent combustion modeling was introduced using either mixture fraction approach or mean reaction rate approach.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권1호
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• pp.31-40
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• 2009

In the present work transformation of dimensionless heat diffusion equation for the solution of moving boundary problems have been formulated. The formulation is based on 1-D, 2-D and 3-D, unsteady heat diffusion equations. These equations are rst turned int dimensionless form by using dimensionless quantities and their transformation was formulated in liquid and solid phases. The salient feature of this work is that during the transformation of dimensionless heat diffusion equation there arises a convective term $\tilde{v}$ which is responsible for the motion of interface in liquid as well as solid phase. In the transformed heat equation, a correction factor $\beta$ also arises naturally which gives the correct transformed flux at interface.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.658-659
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• 2008

Numerical simulation is performed for a microdroplet deposition on the pre-patterned micro-structure. The liquid-air interface is tracked by level set method improved by incorporating the ghost fluid approach based on a sharp-interface representation. The method is further extended to treat the contact angle condition at an immersed solid surface. The present computation of a patterning process using microdroplet ejection demonstrates that the multiphase characteristics between the liquid-gas-solid phases can be used to overcome the patterning error.

• 설비공학논문집
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• 제1권1호
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• pp.64-72
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• 1989

Laminar natural convection heat transfer from a horizontal heat exchanger tube with one infinitely long vertical plate fin has been studied by a finite-difference numerical procedure. In predicting convective heat transfer from a circular tube, the thermal boundary condition at solid fluid interface is usually assumed to be isothermal. However, in reality, the thermal boundary condition is not isothermal, and the tube has the thickness and the conductivity. So the temperature at the interface is not known a priori to the calculation. This problem has the conjugate phenomena which occur between the tube conduction and external natural convection, and between the fin conduction and external natural convection. Numerical results are obtained to determine the effects of the conductivity of solid wall and the thickness of tube wall on heat transfer. It is found that the conduction causes significant influence on the natural convection heat transfer at low K and high ${\delta}$.

• Earthquakes and Structures
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• 제18권6호
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• pp.743-752
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• 2020

The phenomenon of reflection and transmission of plane waves at an interface between fluid half space and orthotropic piezothermoelastic solid half-space with two-temperature has been investigated. Energy ratios of various reflected and transmitted waves are computed with the use of amplitude ratios. The law of conservation of energy across the interface has been justified. It is found that the energy ratios are the functions of angle of incidence, frequency of independent wave and depend on the different piezothermoelastic material. A piezothermoelastic material has been considered which is in welded contact with water. Variations of energy ratios corresponding to the reflected waves and transmitted waves are computed and shown graphically for the two different models. A particular reduced case of interest is also discussed.

• Korean Journal of Mathematics
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• 제7권1호
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• pp.27-35
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• 1999

As seen from the ammonium chloride experiment (Chen & Chen [1], Roberts & Loper [11], the interface near chimneys has an up-rising shape and we observe thickening of mush next to chimney. We analyze the thermal boundary layer around chimney that forms as the mush is cooled locally by the fluid rising through the chimney. We obtain solutions of the temperature, the solid fraction, and the pressure in the chimney wall. Also, our expression of the pressure shows that the fluid flow can require a huge pressure in order to pass through the chimney wall if its permeability is very small. We present a simple analytic description of the up-rising shape near the exit of the chimney, due to the fact that the comparatively solute (i.e. $NH_4Cl$ in the case of the ammonium chloride experiment)-rich fluid near the chimney tends to crystallize as it is chilled by the rising jet of cold fluid in the chimney.

• 한국가시화정보학회지
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• 제12권2호
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• pp.18-22
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• 2014

Caenorhabditis elegans (C. elegans) is an undulatory nematode which exhibits two distinct locomotion types of swimming and crawling. Although in its natural habitat C. elegans lives in a non-Newtonian fluidic environment, our current understanding has been limited to the behavior of C. elegans in a simple Newtonian fluid. Here, we present some experimental results on the penetrating behavior of C. elegans at the interface from liquid to solid environment. Once C. elegans, which otherwise swims freely in a liquid, makes a contact to the solid gel boundary, it begins to penetrate vertically to the surface by changing its stroke motion characterized by a stiffer body shape and a slow stroke frequency. The particle image velocimetry (PIV) analysis reveals the flow streamlines produced by the stroke of worm. For the worm that crawls on a solid surface, we utilize a technique of traction force microscopy (TFM) to find that the crawling nematode forms localized force islands along the body where makes direct contacts to the gel surface.

• Computers and Concrete
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• 제25권2호
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• pp.145-154
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• 2020

For the influence of the propagation law of stress wave at the coal-rock interface during the pre-blasting of the top coal in top coal mining, the ANSYS-LS/DYNA fluid-solid coupling algorithm was used to numerical calculation and the life-death element method was used to simulate the propagation of explosion cracks. The equation of the crushing zone and the fracturing zone were derived. The results were calculated and showed that the crushing radius is 14.6 cm and the fracturing radius is 35.8 cm. With the increase of the angles between the borehole and the coal-rock interface, the vibration velocity of the coal particles and the rock particles at the interface decreases gradually, and the transmission coefficient of the stress wave from the coal mass into the rock mass decreases gradually. When the angle between the borehole and the coal-rock interface is 0°, the overall crushing degree is about 11% and up to the largest. With the increase of the distance from the charge to the coal-rock interface, the stress wave transmission coefficient and the crushing degree of the coal-rock are gradually decreased. At the distance of 50 cm, the crushing degree of the coal-rock reached the maximum of approximately 12.3%.

• 한국해안·해양공학회논문집
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• 제24권4호
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• pp.277-286
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• 2012

기체와 액체의 유동 및 고체의 변형을 동시에 고려할 수 있는 혼상류모델을 이용하여 파동장을 해석하는 경우, 서로 다른 비혼합의 유체 경계면의 시간변형을 고정도로 추적하는 것이 대단히 중요하다. 본 연구에서는 경계면의 추적에 있어서 VOF(Volume of Fluid)법으로 대표되는 경계면 형상의 재구축이 필요한 Geometrical-type의 경계추적법의 대신에 Algebraic-type의 경계추적법인 THINC(Tangent of Hyperbola for INterface-Capturing)법을 적용하였다. THINC법은 경계면에 대한 형상의 구축이 필요하지 않으므로 VOF법에 비해 비교적 간단한 알고리즘을 가지며, 기존의 Navier-Stokes solver에로 적용성이 용이한 장점을 갖는다. 본 연구에서는 THINC법의 기본적인 이류특성을 고찰하고, 혼상류수치모델인 TWOPM(one-field Model for immiscible TWO-Phase flows)과 결합한 수치모델을 파동장에 적용하여 비혼합 혼상류에서 경계면의 추적능을 검토하였다. 그 결과, 혼상류의 경계면 추적에 있어서 상대적으로 간단한 알고리즘의 THINC법이 기존의 VOF법과 유사한 정도를 갖는 해석법이라는 것을 확인할 수 있었고, 따라서 향후 기포의 연행을 동반하는 쇄파 및 쇄파력의 해석 등에 그의 적용성이 기대된다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권3호
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• pp.361-366
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• 2018

Ice crushing occurs in many situations that involve a sliding frictional component such as sports involving ice-contact, ice interaction with ship hulls, and ice-on-ice sliding/crushing within glaciers and between interacting sea ice floes. Ice crushing-friction tests were conducted in the lab at $-10^{\circ}C$ using a set of acrylic ice-crushing platens that included a flat smooth surface and a variety of high-roughness surfaces with regular arrays of small prominences. The experiments were part of Phase II tests of the Blade Runners technology for reducing ice-induced vibration. Ice was crushed against the platens where the ice movement had both a vertical and a horizontal component. High-speed imaging through the platens was used to observe the ice contact zone as it evolved during the tests. Vertical crushing rates were in the range 10-30 mm/s and the horizontal sliding rates were in the range 4.14-30 mm/s. Three types of freshwater ice were used. Friction coefficients were extraordinarily low and were proportional to the ratio of the tangential sliding rate and the normal crushing rate. For the rough surfaces all of the friction coefficient variation was determined by the fluid dynamics of a slurry that flowed through channels that developed between leeward-facing facets of the prominences and the moving ice. The slurry originated from a highly-lubricating self-generating squeeze film of ice particles and melt located between the encroaching intact ice and the surfaces.