• Title/Summary/Keyword: Medium Foam

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The Influence of Meshing Strategies on the Propeller Simulation by CFD

  • Bahatmaka, Aldias;Kim, Dong-Joon
    • Journal of Advanced Research in Ocean Engineering
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    • v.4 no.2
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    • pp.78-85
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    • 2018
  • This paper presents a study of the effects of the free surface to marine propeller including the mesh effect of the models. In the present study, we conduct the numerical simulation for propeller performance employing the openwater test. The numerical simulations compare the meshing strategies for the propeller and show the effects on both thrust and torque. OpenFOAM is applied to solve the propeller problem and then open water performances of KCS propeller (KP505) are estimated using a Reynold-averaged Navier-Stokes equations (RANS) solver and the turbulence of the $K-{\omega}$ SST model. Unstructured meshes are used in the numerical simulation employing hexahedral meshing for mesh generation. The arbitrary mesh interfacing (AMI) and multiple rotating frame (MRF) are compared to define the best meshing strategy. The meshing strategies are evaluated through 3 classifications, i.e., coarse, medium, and fine mesh. Thus, the propeller can be performed utilizing the best mesh strategy. The computational results are validated by comparison with the experimental results. The $K_T$, $K_Q$, and efficiency of the propeller are compared to an experimental result and for all of the meshing strategies. Thus, the simulations show the influence of meshing in order to perform the propeller performances.

Mesh size refining for a simulation of flow around a generic train model

  • Ishak, Izuan Amin;Alia, Mohamed Sukri Mat;Salim, Sheikh Ahmad Zaki Shaikh
    • Wind and Structures
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    • v.24 no.3
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    • pp.223-247
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    • 2017
  • By using numerical simulation, vast and detailed information and observation of the physics of flow over a train model can be obtained. However, the accuracy of the numerical results is questionable as it is affected by grid convergence error. This paper describes a systematic method of computational grid refinement for the Unsteady Reynolds Navier-Stokes (URANS) of flow around a generic model of trains using the OpenFOAM software. The sensitivity of the computed flow field on different mesh resolutions is investigated in this paper. This involves solutions on three different grid refinements, namely fine, medium, and coarse grids to investigate the effect of grid dependency. The level of grid independence is evaluated using a form of Richardson extrapolation and Grid Convergence Index (GCI). This is done by comparing the GCI results of various parameters between different levels of mesh resolutions. In this study, monotonic convergence criteria were achieved, indicating that the grid convergence error was progressively reduced. The fine grid resolution's GCI value was less than 1%. The results from a simulation of the finest grid resolution, which includes pressure coefficient, drag coefficient and flow visualization, are presented and compared to previous available data.

Hydrogen Production in Polyvinyl-Immobilized Anabaena azollae Cells (Polyvinyl에 고정화된 Anabaena azollae에서의 수소생성)

  • 박인호;송종호
    • KSBB Journal
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    • v.6 no.2
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    • pp.181-187
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    • 1991
  • Physiological and morphological characteristics of Anabaena azollae cells immobilized in a synthetic polymer, polyvinyl(PV), were investigated. The cell density of the non-immersed PV foam reached 4.4mg Chl/g dry wt. PV foam. This is 8 times higher than that of PV-immobiliz action in immersed batch system. And MSX-induced ammonia productivity and the photosynthectic oxygen evolution activity are higher than that of free cells after short-term dark storage. Nitrogenase activity and thermostability of photosynthetic activity are also higher than that of free Anabaena cells after immobilization. Total hydrogen production reached to 1.6ml $H_2$ per reactor (total 4mg Chl) after 6 days.

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In Vitro Performance Assessment of a Bioartificial Liver Packed with Polyurethane Foam (다공성 폴리우레탄 충진형 생인공간의 체외 성능 평가)

  • 이두훈;이지현;김성구;박정극
    • KSBB Journal
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    • v.16 no.1
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    • pp.24-29
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    • 2001
  • Recently hepatocyte-based bioartificial liver (BAL) and hepatocyte transplantation have been actively investigated to treat acute hepatic failure. The BAL acts as a bridge to provide patients with more time until a donor organ becomes available for transplantation or until their own liver can be regenerated. In this study, we manufactured a polyurethane foam (PUF) using 15% NCO-prepolymer with a pore opening that allows it to be used as a hepatocyte immobilizing material. Cubes of PUF (3 mm dim.) were seeded with rat primary hepatocytes at a density of 5.5$\pm$1.1$\times$ $10^6$ cells/$cm^3$ PUF by centrifuging them together. The cell laden PUF cubes were packed into a prototype reactor and perfused with a hormonally defined medium for a week. Hepatocytes in the pores of the PUF formed spheroids that showed stable ammonia removal and urea synthesis activities. The albumin production level was comparable to other BAL systems. The PUF packed hepatocyte bioreactor has the potential to be used as a BAL.

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Continuous Foam Separation of Yeast Cells (효모의 연속 포말 분리)

  • 서근학;심현과윤종원
    • KSBB Journal
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    • v.11 no.1
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    • pp.46-51
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    • 1996
  • Cell separation by means of continuous foam separation of Saccharomyes formosensis without additive was investigated. The yeast separation ratio was improved at low feed rates, high nitrogen rates, optimum pH and temperature for ethanol production, dilution of cultivation medium and addition of 0.5g/$\ell$ $CaCl_2$. Percentage of yeast removal and yeast separation ratio were more than 85 when continuous foam separation was operated in optimum condition..

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Continuous Nitrate Reduction by Gel and Foam Matrix (GFM) Immobilized Cells (겔-스폰지 혼용 시스템에 고정화된 세포를 통한 질산염의 연속적 분해)

  • Cho, Yang-Hee;Hahm, Tae-Shik
    • Korean Journal of Food Science and Technology
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    • v.30 no.4
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    • pp.902-907
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    • 1998
  • In this study the anaerobic degradation of nitrate by in GFM (gel and foam matrix) and bead gel immobilized Paracoccus denitrificans DSM 65 in continous culture was conducted. A novel GFM immobilization system was developed in order to improve conventional system (bead). With increasing nitrate concentration in water, the nitrate reduction rate was increased. The observed maximum denitrification rate by in GFM immobilized cells was 177 mg/L h in buffered water, while that was 33 mg/L h in tap water. In comparison with bead system the reduction activity by GFM system showed $1.2{\sim}2.1$ times better. The denitrification activity was not changed after 16 days storage at $5^{\circ}C$ and also showed better activity than that of free cells or even bead immobilized cells.

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Use of CGF and CCW as Medium Components for Commercial Production of Plug Seedlings of Seogun Tomato (토마토 공정묘의 상업적 생산을 위한 배지구성물질로서 발포유리와 탄화 밤나무 칩의 이용)

  • 황승재;정병룡
    • Journal of Bio-Environment Control
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    • v.13 no.2
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    • pp.81-89
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    • 2004
  • This study was conducted in a commercial plug glasshouse in Sacheon to examine the possibility of producing tomato plug seedlings using various growing media containing cellular glass foam (CGF)and carbonized chestnut woodchips (CCW) as medium components. Plug seedlings of 'Seogun' tomato were grown in media containing 50% CCW+50% peatmoss, 33% CGF+67% peatmoss, and 50% peatmoss+50% granular rockwool. A commercial plug medium (Tosilee) was used as the control. All seeds were sown in 200 cell plug trays on November 28, 2001. Seedling growth was measured at 31 days after sowing. Each treatment showed a similar growth result as compared to the control. Plant height, root grade, fresh weight, and air space and bulk density of the medium were significantly greater in the 33% CGF+67% peatmoss treatment than those in the other media. However, growth was slightly suppressed in the 50% CCW+50% peatmoss. pH and EC of the media were the highest in the control treatment, although no toxicity symptoms had been observed. The results suggest that perlite can be replaced with a new material such as CGF in the commercial scale production of plug seedlings of 'Seogun' tomato.

Variation of Atmospheric Concentrations of Organochlorine Pesticides (OCPs) and Polychlorinated Biphenyls (PCBs) at Different Height (대기 중 유기염소계 살충제(OCPs)와 PCBs의 높이별 농도 변화)

  • Chun, Man-Young;Choi, Min-Kyu;Yeo, Hyun-Gu
    • Environmental Analysis Health and Toxicology
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    • v.23 no.3
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    • pp.201-211
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    • 2008
  • This study was performed to find the atmospheric concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) at four different heights (l0, 50, 150 and 1,500 cm) using low volume polyurethane foam (PUF) plug air sampler in semi-rural area. ${\alpha}-/{\beta}-/{\gamma}-HCH$ with low molecular weights and Koa (octanol-air partitioning coefficient) in OCPs were similarly high concentrations at all heights, but the other OCPs (p,p'-DDE, p,p'-DDD, p,p'-DDT, Heptachlor epoxide, ${\gamma}$-CHL, ${\alpha}$-CHL, Trans-nonachlor) with high molecular weights and Koa decreased with increasing heights. However, the concentrations of PCBs increased with increasing height.

Optimized Conditions for High Erythritol Production by Penicillium sp. KJ-UV29, Mutant of Penicillium sp. KJ81

  • Lee, Kwang-Jun;Lim, Jai-Yun
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.8 no.3
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    • pp.173-178
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    • 2003
  • To improve the erythritol productivity of Penicillium sp. KJ81, mutants were obtained using UV irradiation and NTG treatment Among these mutants, Penicillium sp. KJ-UV29 revealed no morphological changes, yet was superior to the wild strain in the following three points: (1) Penicillium sp. KJ-UV29 produced more erythritol than the wild strain under the same conditions, (2) no foam was produced during cultivation, unlike the wild strain, and (3) the mutant produced a Significantly lower amount of glycerol. Penirillium sp. KJ-UV29 produced as much as 15.1 g/L of erythritol, whereas the wild-type Penirillium sp. KJ81 only produced 11.7 g/L. Penicillium sp. KJ-UV29 only generated 6.1 g/L of glycerol, compared to 19.4 g/L produced by the wild strain. When investigating the optimal culture conditions for erythritol production by the mutant strain Penicillium sp. KJ-UV89, sucrose was identified as the most effective carbon source, and the mutant was even able to produce erythritol in a 70% sucrose-containing medium, although a 30% sucrose medium exhibited the highest productivity. The production of erythritol by Penirillium sp. KJ-UV29 was also significantly increased by the addition of ammonium carbonate, potassium nitrate, and sodium nitrate. Accordingly, under optimal conditions, Penicillium sp. KJ-UV29 produced 45.2 g/L of erythritol in a medium containing 30% sucrose, 0.5% yeast extract, 0.5% (NH$_4$)$_2$C$_2$O$_4$, 0.1% KNO$_3$, 0.1% NaNO$_3$, and 0.01% FeSO$_4$ with 1 vvm aeration and 200 rpm agitation at 37$^{\circ}C$ for 7 days in a 5-L jar fermentor.

Selection and Characterization of a High Erythritol Producing Mutant of Moniliella suaveolens var. nigra (에리스리톨 고생산성 변이주인 Moniliella suaveolens var. nigra의 선별과 배양특성)

  • 박홍우;이금숙
    • KSBB Journal
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    • v.17 no.3
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    • pp.290-294
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    • 2002
  • The present work describes the improvement of an erythritol-producing strain to lower the formation of glycerol, which is a characteristic by-product of the strain and could cause difficulties in the recovery and purification of the final product. The yeast-like fungi Moniliella suaveolens var. nigra, isolated previously in the same laboratory from beehives, was mutated by exposing it to a 4 g/L NTG solution. From a total of 2000 mutated strains, Em6j30-14 was selected as the one having the most desirable properties. Cultivating the strain for seven days in 300 mL flasks containing 30 mL of a 400 g/L glucose medium resulted in an erythritol yield of 43%. The glycerol yield was 5%, which is a value 50% lower as compared with the wild type. However, attempts to reproduce the above results in a 5L-fermenter failed, resulting in a similar erythritol concentration but a much higher formation of glycerol. Possible reasons for such a different behaviour could be oxygen limitation or the aggregation of cells, but the exact mechanism could not yet be identified. Foam formation, which is another major problem in large-scale fermentation, tended to be much lower for the mutant strain.