• 대한기계학회논문집B
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• 제37권7호
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• pp.683-693
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• 2013

본 연구에서는 혼성 격자볼츠만 방법(HLBM)을 이용하여 상판이 일정한 속도로 움직이는 공동 형상 내부에서의 혼합 특성에 대하여 수치적으로 연구하였다. 먼저, 공동 형상에서 기존의 신뢰성 있는 유동장 결과와의 비교를 통해 LB-SRT 모델과 LB-MRT 모델의 신뢰성을 검토하였다. 두 모델 모두 기존의 연구결과와 유사한 결과를 보였으나, LB-MRT 모델이 LB-SRT 모델보다 높은 Re수에서는 수치적 안정성이 높은 것을 확인하였다. 수치적 안정성이 좋은 LB-MRT 모델을 토대로 유한차분법을 적용한 HLBM을 이용하여 공동 형상 내부에서의 농도장을 수치 해석하였다. Re수와 Pe수를 변화하여 공동 형상 내부의 혼합 특성과 물질 전달 형태에 대하여 파악하였다.

• Restorative Dentistry and Endodontics
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• 제19권2호
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• pp.345-371
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• 1994

Restorative procedures can lead to weakening tooth due to reduction and alteraton of tooth structure. It is essential to prevent fractures to conserve tooth. Among the several parameters in cavity designs, cavity isthmus and depth are very important. In this study, MO amalgam cavity was prepared on maxillary first premolar. Three dimensional. finite element models were made by serial photographic method and cavity depth(1.7mm, 2.4mm) and isthmus (11 4, 1/3, 1/2 of intercuspal distance) were varied. linear, eight and six-nodal, isoparametric brick elements were used for the three dimensional finite element model. The periodontal ligament and alveolar bone surrounding the tooth were excluded in these models. Three types model(B, G and R model) were developed. B model was assumed perfect bonding between the restoration and cavity wall. Both compressive and tensile forces were distributed directly to the adjacent regions. G model(Gap Distance: 0.000001mm) was assumed the possibility of play at the interface simulated the lack of real bonding between the amalgam and cavity wall (enamel and dentin). When compression occurred along the interface, the forces were transferred to the adjacent regions. However, tensile forces perpendicular to the interface were excluded. R model was assumed non-connection between the restoration and cavity wall. No force was transferred to the adjacent regions. A load of 500N was applied vertically at the first node from the lingual slope of the buccal cusp tip. This study analysed the displacement, von Mises stress, 1 and 2 direction normal stress and strain with FEM software ABAQUS Version 5.2 and hardware IRIS 4D/310 VGX Work-station. The results were as follows: 1. G model showed stress and strain patterns between Band R model. 2. B model and G model showed the bending phenomenon in the displacement. 3. R model showed the greatest amount of the displacement of the buccal cusp followed by G and B model in descending order. G model showed the greatest amount of the displacement of the lingual cusp followed by B and R model in descending order. 4. B model showed no change of the displacement as increasing depth and width of the cavity. G and R model showed greater displacement of the buccal cusp as increasing depth and width of the cavity, but no change in the displacement of the lingual cusp. 5. As increasing of the width of the cavity, stress and strain were not changed in B model. Stress and strain were increased on the distal marginal ridge and buccopulpal line angle in G and R model. The possibility of the tooth fracture was increased. 6. As increasing of the depth of the cavity, stress and strain were not changed in B and G model. Stress and strain were increased on the distal marginal ridge and buccopulpal line angle in R model. The possibility of the tooth fracture was increased.

• 한국가시화정보학회지
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• 제9권3호
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• pp.65-70
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• 2011

Three major physiological functions of nose can be described as air-conditioning, filtering and smelling. Detailed knowledge of airflow characteristics in nasal cavities is essential to understanding of the physiological and pathological aspects of nasal breathing. In our laboratory, a series of experimental investigations have been conducted on the airflows in normal and abnormal nasal cavity models by means of PIV under both constant and periodic flow conditions. In this work, more specifically experimental and numerical results on the surgically modified inferior turbinate model were presented. With the high resolution CT data and a careful treatment of the model surface under the ENT doctor's advice yielded quite sophisticated cavity models for the PIV experiment. Physiological nature of the airflow was discussed in terms of velocity distribution and vortical structure for constant inspirational flow. Since the inferior and middle turbinate are key determinants of nasal airflow, the turbinectomy obviously altered the main stream direction. This phenomenon may cause local changes in physiological function and the flow resistance.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1508-1515
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• 2022

In the present study, the cavity module of the MELCOR code is used for the simulation of molten corium concrete interaction (MCCI) during the late phase of postulated large break loss of coolant (LB-LOCA) accident in the APR1400 reactor design. Using the molten corium composition data from previous MELCOR Simulation of APR1400 under LB-LOCA accident, the ex-vessel phases of the accident sequences with long-term MCCI are recalculated with stand-alone cavity package of the MELCOR code to investigate the impact of water ingression and melt eruption models which were hitherto absent in MELCOR code. Significant changes in the MCCI behaviors in terms of the heat transfer rates, amount of gases released, and maximum cavity ablation depths are observed and reported in this study. Most especially, the incorporation of these models in the new release of MELCOR code has led to the reduction of the maximum ablation depth in radial and axial directions by ~38% and ~32%, respectively. These impacts are substantial enough to change the conclusions earlier reached by researchers who had used the older versions of the MELCOR code for their studies. and it could also impact the estimated cost of the severe accident mitigation system in the APR1400 reactor.

• Design & Manufacturing
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• 제6권2호
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• pp.74-78
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• 2012

A multi-cavity injection mold system of protein chip for point-of-care with cavity temperature and pressure sensors was proposed in this work. In advance of manufacturing for the multi-cavity injection mold system, a single cavity injection mold system to mold protein chip was considered. Injection molding analysis for the presented system was performed to optimize the process of the molding and suggest guides to design. On the basis of the results for the single cavity system, a multi-cavity injection mold system for protein chip was analyzed, designed and manufactured with cavity temperature and pressure sensors. Results of balanced filling for protein chip models were obtained from the presented mold system.

• 대한조선학회논문집
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• 제50권6호
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• pp.436-449
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• 2013

In this paper, a numerical analysis is carried out to study the characteristics of supercavitating flows and the drag of relatively simple two-dimensional and axisymmetric bodies which can be used for supercavity generation device, cavitator, of a high-speed underwater vehicle. In order to investigate the suitability of numerical models, cavity flows around the hemispherical head form and two-dimensional wedge are calculated with combinations of three turbulence models(standard $k-{\epsilon}$, realizable $k-{\epsilon}$, Reynolds stress) and two cavitation models(Schnerr-Sauer, Zwart-Gerber-Belamri). From the results, it is confirmed that the calculated cavity flow is more affected by the turbulence model than the cavitation model. For the calculation of steady state cavity flows, the convergence in case of the realizable $k-{\epsilon}$ model is better than the other turbulence models. The numerical result of the Schnerr-Sauer cavitation model is changed less by turbulence model and more robust than the Zwart-Gerber-Belamri model. Thus the realizable $k-{\epsilon}$ turbulence model and the Schnerr-Sauer cavitation model are applied to calculate supercavitating flows around disks, two dimensional $10^{\circ}$ and $30^{\circ}$ wedges. In case of the disk, the cavitation number dependences of the cavity size and the drag coefficient predicted are similar to either experimental data or Reichardt's semi-empirical equations, but the drag coefficient is overestimated about 3% higher than the Reichardt's equation. In case of the wedges, the cavitation number dependences of the cavity size are similar to experimental data and Newman's linear theory, and the agreement of the cavity length predicted and Newman's linear theory becomes better as decreasing cavitation number. However, the drag coefficients of wedges agree more with experimental data than those of Newman's analytic solution. The cavitation number dependences of the drag coefficients of both the disk and the wedge appear linear and simple formula for estimating the drag of supercavitating disks and wedges are suggested. Consequently, the CFD scheme of this study can be applied for numerical analysis of supercavitating flows of the cavitator and the cavitator design.

• 대한기계학회논문집
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• 제14권2호
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• pp.376-381
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• 1990

An interactive computer program to design a mold cavity with the proper rigging system has been developed. In addition to the pattern and the risers generated in part 1 of this work, the various components of the gating system are generated in complete three dimensional models by a rational approach. Then they are laid interactively by the user, and united together with the pattern and the risers to result in the three dimensional model of the mold assembly. Finally, the vents and the mold box are constructed following the user's interactive specification and then the mold cavity is completed in a three dimensional geometric model by subtraction the mold assembly and the vents from the mold box. The three dimensional model of a mold cavity is useful for many related applications such as the solidification simulation for mold evaluation and the NC tool path generation for mold production.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2302-2312
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• 2000

An active control of the transmission of noise through an aircraft fuselage is investigated numerically. A cylinder-cavity system was used as a model for this study. The fuselage is modeled as a fi nite, thin shel cylinder with constant thickness. The sound field generated by an exterior monopole source is transmitted into the cavity through the cylinder. Point force actuators on the cylinder are driven by error sensor that is placed in 3D cavity. Modal coupling theory is used to formulate the numerical models and describe the system behavior. Minimization of the acoustic potential energy in the fuselage is carried out as a performance index. Continuous parameter genetic algorithm is used to search the optimal actuator position and both results are compared.

• 한국가시화정보학회지
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• 제11권2호
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• pp.46-54
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• 2013

Study of the wave structure and shear layer in the vicinity of a wall mounted cavity is done by time averaged colour schlieren and time resolved instantaneous shadowgraph technique in an M=1.7 flowfield. Effect of change of cavity width on flow structure is investigated by using constant length to depth (L/D) ratio cavity models with varying length to width (L/W) ratio of 0.83 to 4. The time averaged shock wave structure was observed to change with change in cavity width. Dependence of the shock angle at the leading edge on the shear layer width is also evident from the images obtained. Unsteadiness in the flow field in terms of shear layer dynamics and quasi steady nature of shock waves was evident from the images obtained during instantaneous shadowgraph experiments. Apart from the leading and trailing edge shocks, several other waves and flow features were observed. These flow features and the associated physical phenomena are discussed in details and presented in the paper.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.13-14
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• 2003

Two different ${\kappa}-{\varepsilon}-\overline{{\nu}{\nu}}-f$ turbulence models together with the two-layer model are evaluated for natural convection in a rectangular cavity. The numerical problem and accuracy of the turbulence models are discussed. The original $\overline{{\nu}{\nu}}-f$ model suffers from the numerical stiffness problem when used with the segregate solution procedure like the SIMPLE algorithm, and a remedy for this problem is proposed. It is shown that original $\overline{{\nu}{\nu}}-f$ model best predicts the mean velocity, Reynolds stresses and the turbulent heat flux while the modified $\overline{{\nu}{\nu}}-f$ model (N=6) overpredicts the turbulent quantities.