전산유체해석을 활용한 미생물연료전지 산화전극부 유동해석

유재철 ( Jae-cheul Yu ),김홍석 ( Hong-suck Kim ),김병군 ( Byung-goon Kim ),김지연 ( Ji-yeon Kim ) 한국환경기술학회 2012 한국환경기술학회지 Vol.13 No.4

다양한 조건을 대상으로 직접 실험을 통해 최적화된 미생물연료전지(Microbial Fuel Cell; MFC)구조를 결정하고, 설계하기 위해서는 많은 시간과 노력이 소요된다. 따라서, 본 연구에서는 전산유체해석(Computational Fluid Dynamics; CFD)을 이용하여, 다양한 내부구조에 따른 산화전극부내 유동해석을 실시하였다. HRT 2시간 조건으로 전산 모사한 결과, 실험실 조건에서는 L4의 사공간 비율(16.8%)이 상대적으로 낮게 나타났으나, 파일럿 조건에서는 P1의 사공간 비율(39%)이 상대적으로 낮게 나타났다. 격막의 구조를 달리하여, 개수를 증가한 MP1(격막의 개수 18개)의 사공간 비율(20%)이 가장 적은 것으로(80%) 나타났다. 하지만, CFD 결과만으로 최적의 구조를 선정하는 것에는 한계가 있다. 따라서, 추가적인 연구를 통해서, 신뢰성 있는 자료를 확보한다면, 향후, MFC 설계 기초 자료로서 활용할 수 있을 것으로 기대된다. It is required a lot of time and effort to decide and design a optimum microbial fuel cell (MFC) configuration through various experiments. In this study, Fluid performance in anodic compartment was analyzed by computational fluid dynamics. At HRT of 2 h, L4 showed lower the ratio of dead space (16.8%) than the ratio of other configurations in lab-scale. However, P1 showed lower the ratio of dead space (39%) than the ratio of other configurations (53-81 %) in pilot-scale. MP1 with a different type of baffle (18 baffles) showed the lowest dead space of 2%. However, it is limited to select the MFC configuration with only CFD analysis. Thus, it would be used as fundamental data for MFC design, if we get relevant information through further studies.

Computational Fluid Dynamics Modeling Studies on Bacterial Flagellar Motion

Kumar, Manickam Siva,Philominathan, Pichai Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.3

The study of bacterial flagellar swimming motion remains an interesting and challenging research subject in the fields of hydrodynamics and bio-locomotion. This swimming motion is characterized by very low Reynolds numbers, which is unique and time reversible. In particular, the effect of rotation of helical flagella of bacterium on swimming motion requires detailed multi-disciplinary analysis. Clear understanding of such swimming motion will not only be beneficial for biologists but also to engineers interested in developing nanorobots mimicking bacterial swimming. In this paper, computational fluid dynamics (CFD) simulation of a three dimensional single flagellated bacteria has been developed and the fluid flow around the flagellum is investigated. CFD-based modeling studies were conducted to find the variables that affect the forward thrust experienced by the swimming bacterium. It is found that the propulsive force increases with increase in rotational velocity of flagellum and viscosity of surrounding fluid. It is also deduced from the study that the forward force depends on the geometry of helical flagella (directly proportional to square of the helical radius and inversely proportional to pitch).

A Computational Study of Wall Effects on the Aeroelastic Behavior of Spanwise Flexible Wings

Namhun Lee,이승수,조해성,신상준 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.3

In this paper, we present a computational aeroelastic analysis of flexible flapping wings in the vicinity of solid walls. The wall effects change the aerodynamic forces and moments of the wings, and thus the aeroelastic behavior. The numerical simulation is carried out using a fluid–structure interaction framework by coupling the computational fluid dynamics and computational structural dynamics. A preconditioned Navier–Stokes solver based on a finite volume method is used for the aerodynamic analysis. The structural analysis is performed using a nonlinear structural model based on a geometrically exact beam formulation. The method is validated using previous numerical and experimental results. The aeroelastic characteristics of the flexible wings with and without the walls are computed and compared.

Computational Fluid Dynamics를 이용한 부유식 새꼬막 채묘장치의 유동 특성에 관한 연구

편용범,이경훈,최환석,이인태,김형호,이창제,Yong-Beom PYEON,Kyung-Hoon LEE,Hwan-Seok CHOI,In-Tae LEE,Hyoung-Ho KIM,Chang-Je LEE 한국수산해양기술학회 2023 수산해양기술연구 Vol.59 No.2

This study analyzed the flow inside floating seedling equipment for Scapharca subcrenata. Due to the aging society of fishing villages, it is impossible to continuously input the labor force. Therefore, it is necessary to improve efficiency. Scapharca subcrenata has high per capita consumption. It serves as an important aquatic food resource. Scapharca subcrenata culture tends to be highly dependent on the natural environment. Production of Scapharca subcrenata is difficult to predict with low stability. In the past, manpower directly installed bamboo nets in mudflats. The seedling equipment devised in this study is a floating type and can be freely moved on the sea according to the prediction of Scapharca subcrenata generation. The flow around the floating seedling equipment was analyzed by numerical analysis. The physical phenomena of the flow around the net inside the floating seedling equipment were visualized. As a result, the space between the floating seedling equipment and the bottom net and the space between the net groups showed a lower flow rate than the inlet flow rate. It is expected that the low flow rate of the floating seedling equipment will have a positive effect on the attachment of Scapharca subcrenata.

A numerical study on the feasibility of predicting the resistance of a full-scale ship using a virtual fluid

김관우,백광준,이순현,이준희,권수연,오도한 대한조선학회 2024 International Journal of Naval Architecture and Oc Vol.16 No.-

In general, the resistance of a real ship is estimated using an extrapolation method after doing experimental tests or numerical simulations with a model scale ship. Since the only Froude similarity is applied in the model test and simulation, the flow characteristics between the model and real ships could be different due to the inconsistency of Reynolds number. However, in the Computational Fluid Dynamics (CFD), the Froude and Reynolds numbers can be satisfied simultaneously because a fluid with virtual properties can be applied. This study investigated the effect of turbulence models and scales for a flat plate. And then the hydrodynamic feasibility of using a virtual fluid was investigated through numerical analysis. The resistance performance and flow structure of the ship were analysed by applying the virtual fluid, and they were confirmed how well these values and flow characteristics simulate the full-scale with a real fluid. This study shows that the results of a full-scale can be obtained at model scale by applying a virtual fluid instead of full-scale numerical simulations that require more computational resources.

Physics-informed deep learning for data-driven solutions of computational fluid dynamics

최솔지,정익환,김하은,나종걸,이종민 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.3

Computational fluid dynamics (CFD) is an essential tool for solving engineering problems that involve fluid dynamics. Especially in chemical engineering, fluid motion usually has extensive effects on system states, such as temperature and component concentration. However, due to the critical issue of long computational times for simulating CFD, application of CFD is limited for many real-time problems, such as real-time optimization and process control. In this study, we developed a surrogate model of a continuous stirred tank reactor (CSTR) with van de Vusse reaction using physics-informed neural network (PINN), which can train the governing equations of the system. We propose a PINN architecture that can train every governing equation which a chemical reactor system follows and can train a multi-reference frame system. Also, we investigated that PINN can resolve the problem of neural network that needs a large number of training data, is easily overfitted and cannot contain physical meaning. Furthermore, we modified the original PINN suggested by Raissi to solve the memory error and divergence problem with two methods: Mini-batch training and weighted loss function. We also suggest a similarity-based sampling strategy where the accuracy can be improved up to five times over random sampling. This work can provide a guideline for developing a high performance surrogate model of the chemical process.

Computational Fluid Dynamics를 활용한 점/접착 생산 공정 내 Jacketed Vessel 설계 최적화

주종효 ( Chonghyo Joo ),박현도 ( Hyundo Park ),조형태 ( Hyungtae Cho ),김정환 ( Junghwan Kim ) 한국공업화학회 2020 공업화학 Vol.31 No.6

점/접착제 생산 공정은 배합 과정에서 mineral insulated (MI) cable을 통해 내부 용액을 76 ℃까지 가열 및 혼합 후 제품출하를 위해 30 ℃까지 상온 냉각을 진행한다. MI cable을 이용한 반응기의 경우, 냉각시간이 평균 10 h 소요되어 생산효율이 낮은 문제점이 있지만, jacketed vessel을 설치하면 위의 문제를 효과적으로 해결할 수 있다. 그러나 jacketedvessel의 종류가 다양해 jacket을 설치하기 전, 배합 공정조건에 적합한 종류를 찾아야 한다. 본 연구에서는 생산효율에 영향을 주는 냉각시간을 최소화하기 위해 computational fluid dynamics (CFD)를 이용하여 jacket 종류에 따른 냉각시간을 비교해 공정에 적합한 jacketed vessel 모델을 개발하고, 점/접착제 생산 공정에 최적화된 jacketed vessel을 설계하였다. 연구 결과, jacket의 높이가 같을 때, half-pipe coil jacket보다 plain jacket의 냉각 성능이 32.7% 더 우수하였고, plainjacket에 60% spiral baffle을 설치하여 냉각 공정에 이용할 경우 냉각시간을 80.4%, 작업시간을 25.1% 단축 가능하다. Blending process of adhesive production has a cooling process to cool down the temperature of the solution which was heated up to 76 ℃ with a mineral insulated (MI) cable by 30 ℃ at room temperature. Using a MI cable in the adhesive production process makes the production inefficient because it takes about 10 h for the cooling process. If a jacketed vessel is used instead of the MI cable, it would shorten the cooling downtime without any additional cooling system by using cold water. However, there are various types of jacketed vessels, and thus the most suitable type should be found before set up. In this study, we designed the optimized jacketed vessel for the adhesive production process by calculating the cooling downtime, which impacts production efficiency, as a function of the jacket types using computational fluid dynamics. As a result, the cooling performance of the plain jacket was 32.7% superior to that of the half-pipe coil jacket with the same height. In addition, the plain jacket with 60% spiral baffle reduced the cooling downtime and operating time by 80.4% and 25.1%, respectively.

Numerical simulation on fluid-structure interaction of wind around super-tall building at high reynolds number conditions

Huang, Shenghong,Li, Rong,Li, Q.S. Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.2

With more and more high-rise building being constructed in recent decades, bluff body flow with high Reynolds number and large scale dimensions has become an important topic in theoretical researches and engineering applications. In view of mechanics, the key problems in such flow are high Reynolds number turbulence and fluid-solid interaction. Aiming at such problems, a parallel fluid-structure interaction method based on socket parallel architecture was established and combined with the methods and models of large eddy simulation developed by authors recently. The new method is validated by the full two-way FSI simulations of 1:375 CAARC building model with Re = 70000 and a full scale Taipei101 high-rise building with Re = 1e8, The results obtained show that the proposed method and models is potential to perform high-Reynolds number LES and high-efficiency two-way coupling between detailed fluid dynamics computing and solid structure dynamics computing so that the detailed wind induced responses for high-rise buildings can be resolved practically.

Numerical study of fluid behavior on protruding shapes within the inlet part of pressurized membrane module using computational fluid dynamics

Changkyoo Choi,Chulmin Lee,No-Suk Park,In S. Kim 대한환경공학회 2020 Environmental Engineering Research Vol.25 No.4

This study analyzes the velocity and pressure incurred by protruding shapes installed within the inlet part of a pressurized membrane module during operation to determine the fluid flow distribution. In this paper, to find the flow distribution within a module, it investigates the velocity and pressure values at cross-sectional and outlet planes, and 9 sections classified on outlet plane using computational fluid dynamics. From the Reynolds number (Re), the fluid flow was estimated to be turbulent when the Re exceeded 4,000. In the vertical cross-sectional plane, shape 4 and 6 (round-type protrusion) showed the relatively high velocity of 0.535 m/s and 0.558 m/s, respectively, indicating a uniform flow distribution. From the velocity and pressure at the outlet, shape 4 also displayed a relatively uniform fluid velocity and pressure, indicating that fluid from the inlet rapidly and uniformly reached the outlet, however, from detailed data of velocity, pressure and flowrate obtained from 9 sections at the outlet, shape 6 revealed the low standard deviations for each section. Therefore, shape 6 was deemed to induce the ideal flow, since it maintained a uniform pressure, velocity and flowrate distribution.

Investigation of a fiber reinforced polymer composite tube by two way coupling fluid-structure interaction

Daricik, Fatih,Canbolat, Gokhan,Koru, Murat Techno-Press 2022 Coupled systems mechanics Vol.11 No.4

Fluid-Structure Interaction (FSI) modeling is highly effective to reveal deformations, fatigue failures, and stresses on a solid domain caused by the fluid flow. Mechanical properties of the solid structures and the thermophysical properties of fluids can change under different operating conditions. In this study, we investigated the interaction of [45/-45]₂ wounded composite tubes with the fluid flows suddenly pressurized to 5 Bar, 10 Bar, and 15 Bar at the ambient temperatures of 24℃, 66℃, and 82℃, respectively. Numerical analyzes were performed under each temperature and pressure condition and the results were compared depending on the time in a period and along the length of the tube. The main purpose of this study is to present the effects of the variations in fluid characteristics by temperature and pressure on the structural response. The variation of the thermophysical properties of the fluid directly affects the deformation and stress in the material due to the Wall Shear Stress (WSS) generated by the fluid flow. The increase or decrease in WSS directly affected the deformations. Results show that the increase in deformation is more than 50% between 5 Bar and 10 Bar for the same operating condition and it is more than 100% between 5 Bar and 15 Bar by the increase in pressure, as expected in terms of the solid mechanics. In the case of the increase in the temperature of fluid and ambient, the WSS and Von Mises stress decrease while the slight increases of deformations take place on the tube. On the other hand, two-way FSI modeling is needed to observe the effects of hydraulic shock and developing flow on the structural response of composite tubes.