• Title, Summary, Keyword: flow behavior index

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Useful Guide to Solve Herschel-Bulkley Model in a Flow Mode Damper (유동 모드 댐퍼에서의 Herschel-Bulkley 모델의 유용한 해법)

  • 이덕영;박성태
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.784-787
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    • 2003
  • Electrorheological(ER) and magnetorheological(MR) fluid-based dampers are typically analyzed using Bingham-plastic shear model under quasi-steady fully developed flow conditions. A Herschel-Bulkley constitutive shear flow relationship is that the linear shear stress vs. strain rate behavior of Bingham model is replaced by a shear stress that is assumed to be proportional to a power law of shear rate. This power is called the flow behavior index. Depending on the value of the flow behavior index number, varying degrees of post-yield shear thickening or thinning behavior can be analyzed. But it is not practical to analyze the damping force in a flow mode damper using Herschel-Bulkley model because it is needed to solve a polynomial equation. A useful guide is suggested to analyze the damping force in a damper using the Herschel-Bulkley model.

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Changes in the Rheological Characteristics by Various Concentrations and Temperatures of Korean white Gruel (농도와 온도에 따른 흰죽의 리올로지 특성 변화)

  • Lee, Chang-Ho;Han, Ouk
    • Korean journal of food and cookery science
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    • v.11 no.5
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    • pp.552-556
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    • 1995
  • The rheological properties of Korean white gruel at various concentrations (4-7%) and temperatures (30-60$^{\circ}C$) were investigated. The rheological behavior of Korean white gruel was evaluated by Herschel-Bulkley equation and showed typical Bingham psedoplastic behavior with yield stress. Flow behavior index was increased at over 5% of rice content. Consistency index was increased by the increase of concentration of rice. But, measuring temperature was not effected in the flow behavior index and consistency index. Yield stress was increased by the incerase of concentration of rice and the decrease of measuring temperature. The activation energy of flow of Korean gruel increased from 7.646 to 32.949${\times}$10/Sup 6/ J/Kg$.$ mole by increasing concentration from 4% to 7%. As the temperature increased from 30$^{\circ}C$ to 60$^{\circ}C$, B-value decresed from 1.214 to 0.947 Flow behavior index and consistency index was reduced during storage.

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Rheological Properties of Mycelial Broth in Submerged Culture of Aspergillus niger No. PFST-38

  • Oh, Sung-Hoon;O, Pyong-Su
    • Journal of Microbiology and Biotechnology
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    • v.3 no.3
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    • pp.209-213
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    • 1993
  • The flow behavior of the mycelial broth of glucoamylase hyperproducer Asp. niger No. PFST-38 for the production of glucoamylase were studied. The mycelial broth followed Bingham-pseudoplastic flow model described by Herschel-Bulkley equation. The yield stress increased with the increase in mycelial concentration. The dependency of the consistency index and the flow behavior index on the mycelial concentration could be expressed by a linear relationship. The consistency index increased proportionally with the mycelial concentration while the flow behavior index decreased with the increase in mycelial concentration. The flow property of the broth was related to the morphological data obtain in the previous study. The changes in apparent viscosity of the broth could be expressed as a function of the hyphal thickness as shown below.

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A Study on the Effect of the Inclined Structure on the Hydraulic Behavior Index within Sedimentation basin (경사 구조물이 침전지내 수리거동 Index에 미치는 영향)

  • Lim, Seong-Ho;Hwang, Jun-Sik;Park, No-Suk;Kim, Seong-Su;Lim, Kyung-Ho
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.5
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    • pp.517-526
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    • 2009
  • This research has been conducted to investigate the characteristics of hydraulic behavior within the PAC contactor, the rectangular shape sedimentation basin without inclined tube and the other one with inclined tube those are parts of demonstration plants(capacity : $2,000m^3/d$) in Korea Institute of Water and Environment. As results of tracer tests, the flow within PAC contactor was evaluated to divided into plug flow and dead space distinctly, and characteristics of dead space was close to that of CSTR(Complete/continuous Stirred Tank Reactor). Also, considering Reynolds number, Froude number, Morill, Modal, NCSTR Inex and plug flow/mixed flow fraction, in the case of the rectangular shape sedimentation basin without inclined tube, the characteristics of flow pattern was close to CSTR. On the other hand, in the case of the basin with inclined tube, the region of CSTR decreased precisely compared with the case of no-tube. Until now we have recognized that the inclined hydraulic structure just reduces the surface loading rate within a sedimentation basin. Actually besides, the inclined structure have an important effect on the hydraulic behavior within the basin.

Studies on the Flow Properties of Semi-Solid Dosage Forms (I) : Steady Shear Flow Behavior of Toothpastes (반고형제제의 유동특성에 관한 연구 (제1보) : 치약의 정상전단 유동거동)

  • Kim, Jeong-Hwa;Song, Ki-Won;Lee, Jang-Oo;Lee, Chi-Ho
    • Journal of Pharmaceutical Investigation
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    • v.25 no.3
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    • pp.213-221
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    • 1995
  • The steady shear flow properties of six kinds of commercial toothpastes were measured using a concentric cylinder type rheometer. In this paper, the shear rate and temperature dependencies of their flow behavior were investigated and the validity of the Casson and Herschel-Bulkley models was examined. Further, the flow properties over a wide temperature range were quantitatively evaluated by calculating the various material parameters. Main results obtained from this study can be summarized as follows: (1) Toothpastes are plastic fluids with a yield stress and their flow behavior shows shear-thinning characteristics. (2) With increasing temperature, the degree of shear-thinning becomes weaker and the Newtonian flow behavior occurs at a lower shear rate range. (3) The Herschel-Bulkley model is more effective than the Casson model in predicting their flow behavior. (4) As the temperature increases, the yield stress, plastic viscosity and consistency index become smaller, on the contrary, the flow behavior index becomes larger.

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Flow Properties of Doenjang (시판된장의 리올로지(Rheology) 특성에 관한 연구)

  • 양신철;김선화
    • Journal of Applied Tourism Food and Beverage Management and Research
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    • v.13 no.1
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    • pp.55-68
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    • 2002
  • Flow properties of doenjang samples at various total solid contents (30, 32, 34, 36, 38, 40%) were evaluated in this study. Flow properties of doenjang samples was determined by using Haake concentric cylinderical viscometer and Instron testing machine with capillary extrusion viscometer, and consistency index(K), and flow behavior index(n) was also determined from power models, and yield stress was derived form Casson models and vanes methods. Doenjang samples showed shear-thinning (pseudoplastic) fluid with small magnitude of flow behavior index(n) (n=0.30-0.55). Casson yield stress was from 2.11 to 64.02(Pa). Vane yield stress was more effective than casson yield stress in property of reactivation. Apparent viscosity was decreased with the increase in temperature and activation energy was in the range of 6.58 to 10.70 kJ/mole. From the capillary extrusion method, K and n was increased with the increase in solid content with good correlation with. The result revealed that capillary extrusion method is useful for measuring the flow properties of doenjang.

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Rheological Properties of Freeze Dried $\alpha$-Rice Powder (동결건조 $\alpha$-미분의 물성에 관하여)

  • 김관유
    • The Korean Journal of Food And Nutrition
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    • v.4 no.2
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    • pp.199-206
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    • 1991
  • Rheological properties of $\alpha$-rice powder were investigated in comparison with those of polished rice powder. Flow behavior for cooked solutions of two powdered samples(5~11%) were Binghampseudo plastic. Consistency index and yield stress of cooked solution of powdered a-rice were much lower than those of polished rice powder while flow behavior index was nearly similar. 9% cooked solution of powdered $\alpha$ -rice showed slightly weaker thixotrophic behavior and more ease tendency to relax under the steady shear than those of polished rice powder.

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Effect of Rice Lipid and Protein on Rheological Characteristics of Gelatinized Rice Flour Solutions (쌀의 지방과 단백질이 쌀가루 호화액의 리올리지 특성에 미치는 영향)

  • 이영순;김인호;김현정;이상효;이현유;박광희
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.28 no.6
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    • pp.1293-1297
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    • 1999
  • Effect of rice protein and lipid on rheological properties of gelatinized rice flour solutions(4%) with three rice varieties(Dongjin, Jinmi, Tamjin) known for varying taste of cooked rice was investigated with Haake viscometer. The rheological behaviors of all rice flour solutions were illustrated by Herschel Bulkley equation and exhibited pseudoplastic behavior with yield stress. When rice flour solutions treated with protease and dithiothreitol, there was decreased in flow behavior index value. Flow behavior index was decreased by dealbumin and deglutelin rice flour solutions among deprotein groups. The Jinmi rice flour solutions exhibited slightly lower consistency index than Dongjin and Tamjin. Defatted rice flour solutions exhibited lower consistency index than rice flour solutions, while dealbumin, deglutelin rice flour solutions exhibited high consistency index. Protease treated rice flour solutions exhibited increase in Dongjin and Tamjin. The yield stress was increased in sequence eating quality. Yield stress of defatted rice flour solutions was decreased, while deglutelin and rice starch flour solutions was increased. The time dependent charac teristics of all rice flour solutions appeared forming hysteresis loop and thixotropic behavior showed. The time dependent characteristics was appeared in sequence eating quality. Rice starch and deglutelin flour solutions appeared greatly time dependent characteristics, but defatted rice flour solutions appeared very little.

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CFD Simulation of the Effects of Inlet Flow rate on Hydraulic Behavior in Continuous Stirred-Tank Reactor (CSTR) (CFD 모사 기법을 이용한 유입 유량에 의한 연속 완전혼화 반응조 수리거동 고찰에 관한 연구)

  • Lee, Young Joo;Oh, Jeong Ik;Yoon, Sukmin;Kim, Jong-Oh;Park, No-Suk
    • Journal of Korean Society of Environmental Engineers
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    • v.38 no.1
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    • pp.25-33
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    • 2016
  • This paper describes three-dimensional computational fluid dynamics (CFD) simulation of liquid-liquid flow and transient tracer tests in a full-scale continuous stirred-tank reactor (CSTR) used for drinking water treatment. To evaluate the effects of inlet flow rate on hydrodynamic behavior in the selected CSTR, inlet flow rate was changed from 10% to 100% of the design flow rate. From the results of CFD simulation and analysis, as the inlet flow rate increases, Modal index and ${\beta}$ value are increased. Also, Morrill index shows local minimal points in relation to the inlet flow rate, which are observed at 20% and 40% of the design flow. As inlet flow Increases more than 40%, it is shown that Morrill index re-increases to close to ideal CSTR.

Rheological Behavior of Semi-Solid Ointment Base (Vaseline) in Steady Shear Flow Fields (정상전단유동장에서 반고형 연고기제(바셀린)의 레올로지 거동)

  • Song, Ki-Won;Kim, Yoon-Jeong;Lee, Chi-Ho
    • Journal of Pharmaceutical Investigation
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    • v.37 no.3
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    • pp.137-148
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    • 2007
  • Using a strain-controlled rheometer [Rheometrics Dynamic Analyzer (RDA II)], the steady shear flow properties of a semi-solid ointment base (vaseline) have been measured over a wide range of shear rates at temperature range of $25{\sim}60^{\circ}C$. In this article, the steady shear flow properties (shear stress, steady shear viscosity and yield stress) were reported from the experimentally obtained data and the effects of shear rate as well as temperature on these properties were discussed in detail. In addition, several inelastic-viscoplastic flow models including a yield stress parameter were employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models was examined by calculating the various material parameters (yield stress, consistency index and flow behavior index). Main findings obtained from this study can be summarized as follows : (1) At temperature range lower than $40^{\circ}C$, vaseline is regarded as a viscoplastic material having a finite magnitude of yield stress and its flow behavior beyond a yield stress shows a shear-thinning (or pseudo-plastic) feature, indicating a decrease in steady shear viscosity as an increase in shear rate. At this temperature range, the flow curve of vaseline has two inflection points and the first inflection point occurring at relatively lower shear rate corresponds to a static yield stress. The static yield stress of vaseline is decreased with increasing temperature and takes place at a lower shear rate, due to a progressive breakdown of three dimensional network structure. (2) At temperature range higher than $45^{\circ}C$, vaseline becomes a viscous liquid with no yield stress and its flow character exhibits a Newtonian behavior, demonstrating a constant steady shear viscosity regardless of an increase in shear rate. With increasing temperature, vaseline begins to show a Newtonian behavior at a lower shear rate range, indicating that the microcrystalline structure is completely destroyed due to a synergic effect of high temperature and shear deformation. (3) Over a whole range of temperatures tested, the Herschel-Bulkley, Mizrahi-Berk, and Heinz-Casson models are all applicable and have an almostly equivalent ability to quantitatively describe the steady shear flow behavior of vaseline, whereas the Bingham, Casson,and Vocadlo models do not give a good ability.