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A multiphase flow modeling of gravity currents in a rectangular channel (사각형 수로에서 중력류의 다상흐름 수치모의)

  • Kim, Byungjoo;Paik, Joongcheol
    • Journal of Korea Water Resources Association
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    • v.52 no.10
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    • pp.697-706
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    • 2019
  • A multiphase flow modeling approach equipped with a hybrid turbulence modeling method is applied to compute the gravity currents in a rectangular channel. The present multiphase solver considers the dense fluid, the less-dense ambient fluid and the air above free surface as three phases with separate flow equations for each phase. The turbulent effect is simulated by the IDDES (improved delayed detach eddy simulation), a hybrid RANS/LES, approach which resolves the turbulent flow away from the wall in the LES mode and models the near wall flow in RANS mode on moderately fine computational meshes. The numerical results show that the present model can successfully reproduce the gravity currents in terms of the propagation speed of the current heads and the emergence of large-scale Kelvin-Helmholtz type interfacial billows and their three dimensional break down into smaller turbulent structures, even on the relatively coarse mesh for wall-modeled RANS computation with low-Reynolds number turbulence model. The present solutions reveal that the modeling approach can capture the large-scale three dimensional behaviors of gravity current head accompanied by the lobe-and-cleft instability at affordable computational resources, which is comparable to the LES results obtained on much fine meshes. It demonstrates that the multiphase modeling method using the hybrid turbulence model can be a promising engineering solver for predicting the physical behaviors of gravity currents in natural environmental configurations.

Postharvest Handling and Marketing Management for Making High Salability of Sweetpotatoes (상품성 제고를 위한 고구마 수확 후 관리 및 출하기술)

  • Jeong, Byeong-Choon
    • Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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    • 2001.06a
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    • pp.51-64
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    • 2001
  • The qualities including taste of sweetpotato stored during the winter which can display in the spring market in Korea are affected by availability of storage for the roots. In order to make high storage availability of sweetpotato, the postharvest handlings should be done thoroughly from the moment of harvest until shipping them to the market. A lot of procedures that must be handled carefully for improving postharvest management are as follows; digging, trimming, gathering, putting in storage containers, carrying them from field to house, curing, storing, washing, drying, selecting marketable roots, packing and shipping to the market, etc.. Sweetpotatoes have a high moisture content, and a relatively thin and delicate skin, and are sensitive to chilling, so careless postharvest handling can lead to both quantitative and qualitative losses which may be extremely high in some circumstances. From now on research has concentrated on the improvement of postharvest conditions to increase yield and lower disease rates. Storage, which makes sweetpotatoes available through out the year, benefits both the producer and the consumer. Seven very important points must be needed in order to get the best quality marketable roots in the storing of sweetpotatos : $\circled1$The storage house must be clean and sanitary, $\circled2$The crop must be harvested before the first frost to avoid low-temperature injury, $\circled3$Particular care must be taken to avoid cutting, bruising, or other injuries of the sweetpotatoes during digging, picking up, grading, placing in containers, and moving to the storage house, $\circled4$Select sound, disease-free roots for storage $\circled5$Sweetpotatoes should be stored in properly stacked containers $\circled6$Cure immediately after harvest, preferably at 32∼33$^{\circ}C$ and 90 to 95 percent relative humidity for 4 to 7 days, After curing the temperature should be reduced to 13$^{\circ}C$ to 16$^{\circ}C$ by ventilating the storage with outside air. $\circled7$Store at 12$^{\circ}C$ to 14$^{\circ}C$ and a relative humidity of 80 to 85 percent. Storage houses should be located on suitable sites and should be tightly constructed and insulated so that temperature and humidity will be uniform. Sweetpotatoes are usually not washed and graded, and lately sometimes washed, graded, waxed, before being shipped to market. Consumer packaging of sweetpotatoes in paper boxes(10-15kg) or film bags is done mainly to aid marketing. The shelf life of washed roots in consumer packs in only 1 to 2 weeks. Weight loss of roots during marketing is much less in perforated film bags than in mesh and paper bags. Perforation of 0.8 to 1kg polyethylene bags with about six 6mm holes is essential ; to lower the internal relative humidity and avoid excessive sprouting, rooting, and dampness. Development and use of better postharvest handling with good storage facilities or marketing methods can minimize sweetpotate losses and has an effect of indirectly increasing productivity and farmer’s income.

Physicochemical Quality Characteristics of Traditional Kamju Using Extruded Rice Collet Powder (압출 쌀 콜렛 분말을 사용한 전통 감주의 제조 및 이화학적 품질 특성)

  • Je, Hae-Soo;Kang, Kyung-Hun;Park, Si-Young;Choi, Byeong-Dae;Kang, Young-Mi;Kim, Jeong-Gyun
    • Korean Journal of Food Science and Technology
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    • v.48 no.2
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    • pp.147-152
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    • 2016
  • This study was conducted to investigate the physicochemical quality properties and provide basic data for the activation of traditional Kamju of juice type product prepared by mixing malt and extruded rice collet powder. Malt extracts were prepared by extracting the mixture of malt and water at a weight ratio of 25:75 after soaking for 2 h at $45^{\circ}C$. Rice collet powder was prepared by adjusting the barrel temperature to $95^{\circ}C$, screw speed to $3.07{\times}g$, discharge port diameter to 7 mm and a raw material input to 50 kg/h, the powder was then ground to a particle size of 80 mesh. The physicochemical characteristics (pH, color, viscosity, reducing sugars, number of viable cells, free amino acids) and sensory evaluations were conducted at various time points during the saccharification and at different mixing ratios of the extruded rice collet powder to malt extract (5:95, 15:85, 25:75, 35:65, each at $55^{\circ}C$ for 9 h). As a result, with an increase in the proportion of the extruded rice collet powder and saccharification time, the physicochemical properties of traditional Kamju significantly improved (p<0.05). A mixing ratio of 35:65 rice collet powder to malt extract and a saccharification time of 9 h were found to be the most desirable conditions. However, based on the sensory evaluation, a mixing ratio of rice collet powder and malt extract of 25:75 and a saccharification time of 5 h resulted in the most preferable palatability of traditional Kamju (p<0.05). Therefore, the mixing ratio and saccharification time should be determined to provide a better choice with respect to the taste and economic aspects of traditional Kamju.

Processing of anchovy based powder for instant soup packed in tea bag and the taste compound of its extractives (Tea bag 포장한 멸치 복합 분말의 가공 및 그 추출물의 정미성분)

  • Lee, Ho-Yeon;Chung, Bu-Gil;Lee, Jung-Suck;Kim, Poong-Ho;Kim, Jin-Soo;Lee, Eung-Ho
    • Applied Biological Chemistry
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    • v.36 no.4
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    • pp.271-276
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    • 1993
  • This study was carried out to prepare anchovy based powder for instant soup packed in tea bag which can be used handily as a extractives, and to determine the taste compounds of extractives of anchovy based powder for instant soup. The anchovy based powder for instant soup was made by adding of 72% in the redried anchovy, 14% in the sea tangle, 7% in the mushroom and 7% in the katsuobushi to the total mixtures. And the anchovy based powder for instant soup was packed in tea bag. The desirable extraction time are 5 min in package in tea bag with air permeability $100\;m^3/m^2/min$ and over 20 min in package in tea bag with air permeability $65\;m^3/m^2/min$, respectively. Judging from the result of extraction rate of total nitrogen, color and sensory evaluation in extractives of anchovy based powder for instant soup extracted by optimal extraction time, the quality in extractives of instant soup packed in tea bag with air permeability $100\;m^3/m^2/min$ was superior to those of instant soup unpacked in tea bag and of instant soup packed in tea bag of air permeability $65\;m^3/m^2/min$. The principal taste compounds of extractives of anchovy based powder for instant soup packed in tea bag with air permeability $100\;m^3/m^2/min$ were IMP (9.26 mg/100ml in 5% solution) and free amino acids (24.30 mg/100 ml in 5% solution) such as histidine, proline, lysine and taurine. Total creatinine, betaine and TMAO were seemed to act an auxiliary role in taste of extracives of anchovy based powder for instant soup packed in tea bag with air permeability $100\;m^3/m^2/min$.

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