Yoshihito Kato

Experimental study on miscible viscous fingering involving viscosity changes induced by variations in chemical species concentrations due to chemical reactions

When a reactive and miscible less-viscous liquid displaces a more-viscous liquid in a Hele-Shaw cell, reactive miscible viscous fingering takes place. We succeed in showing experimentally how a reactive miscible viscous fingering pattern in a radial Hele-Shaw cell changes when the viscosity of the more-viscous liquid is varied owing to variation in chemical species concentration induced by an instantaneous chemical reaction. This is done by making use of a polymer solutions dependence of viscosity on pH. When the viscosity is increased by the chemical reaction, the shielding effect is suppressed and the fingers are widened. As a result, the ratio of the area occupied by the fingering pattern in a circle whose radius is the length of the longest finger is larger in the reactive case than in the non-reactive case. When the viscosity is decreased by the chemical reaction, in contrast, the shielding effect is enhanced and the fingers are narrowed. These lead to the area ratio being smaller in the reactive case than in the non-reactive case. A physical model to explain this change in the fingering pattern caused by the chemical reaction is proposed.

Power Consumption and Mixing Time in an Agitated Vessel with Double Impeller

Power consumption in a non-baffled agitated vessel with a double impeller was measured over a wide range of Reynolds number from laminar to turbulent flow regions. The power correlation for the double impeller was derived from the modification of the power correlation for a single impeller proposed by the authors. The power consumption in a baffled vessel was only measured in the turbulent flow region. The power consumption for the double impeller has the maximum value, which was almost twice the power consumption for the single impeller at larger ratio of impeller clearance to liquid depth than 0.35, and it took the minimum value at the impeller clearance ratio of 0.18–0.25. Mixing time in a baffled vessel with some types of double impeller was measured in the turbulent flow region using the decolorization method of sodium thiosulfate and iodine reaction. The minimum mixing time was observed at 0.1–0.2 of the ratio of impeller clearance to liquid depth for the two-stage paddle system, and 0.5–0.7 for the double impellers constructed with the pitched blade paddle. The relationship of mixing time to power consumption for the double impeller system coincided with that for a single impeller at the impeller clearance taking the minimum mixing time.

Effects of moderate Damköhler number on miscible viscous fingering involving viscosity decrease due to a chemical reaction

We have succeeded in experimentally investigating the effects of a moderate Damkohler number, Da (defined as the ratio between a characteristic time of fluid motion and that of a chemical reaction), for various Peclet numbers, Pe , on miscible viscous fingering involving a decrease in the viscosity of the displaced liquid due to a chemical reaction in Hele-Shaw cells. We achieved this by using a chemical reaction between a polymer solution and metal ions. Main analysis has been done for the radial fingering. In the range of Pe employed here, the fingering patterns without the reaction ( Da = 0) were independent of Pe . The fingering patterns with the reaction depended on the single parameter, Da , and the area occupied by the fingering pattern near the injection hole increased with Da in the range of Da employed here. The ratio of the area occupied by the fingering pattern within the circle radius of which is the length of longest finger to the area of the circle increased with Da in the range of Da employed here. This result is opposite to that of Nagatsu et al . ( J. Fluid Mech ., vol. 571, 2007, p. 475), in which the area was decreased by the reaction decreasing the viscosity involving significantly high Da . Experiments in the linear geometry show that the shape of a single finger also depended on the single parameter, Da , and the finger width increased near the base with Da . This result is also opposite to that in the previous case in which the width of a single finger was considered to be decreased by the reaction. These results, interestingly, show that the effects of the decrease in the displaced liquids viscosity due to chemical reaction on the fingering pattern for moderate Da are opposite to those for significantly high Da . A mechanism for the opposite effects on the fingering pattern depending on Da is discussed.

Correlation of Power Consumption for Several Kinds of Mixing Impellers

The authors reviewed the correlations of power consumption in unbaffled and baffled agitated vessels with several kinds of impellers, which were developed in a wide range of Reynolds numbers from laminar to turbulent flow regions. The power correlations were based on Kamei and Hiraokas expressions for paddle and pitched paddle impellers. The calculated correlation values agreed well with experimental ones, and the correlations will be developed the other types of impellers.

Enhanced anthocyanin production from grape callus in an air-lift type bioreactor using a viscous additive-supplemented medium.

An N-medium containing carboxymethyl cellulose (CMC) was applied to an air-lift type bioreactor culture of grape (Vitis vinifera cv. Bailey alicant A.) callus, and anthocyanin production was investigated. Grape callus grew well at an air flow rate of 80 ml/min and anthocyanin production was significantly increased in the N-medium, reaching 17 mg/l after 7 d of culture. The anthocyanin content of the N-medium was about two times higher than that of the conventional medium without CMC. The effect of air flow rate was also investigated within the range from 40 to 160 ml/min. A twofold increase in anthocyanin content was obtained at all the air flow rates tested in the N-medium. The distribution of grape callus size obtained after 7 d of the bioreactor culture was investigated. The average callus size was 490 mum which was 1.6 times larger than that obtained in the conventional medium. It was found that large calli with a relatively high anthocyanin pigment content were formed in the bioreactor culture using the N-medium. The fluid dynamics in the bioreactor was also investigated at three points (top, middle and bottom) in the bioreactor by laser doppler velocimetry. The average axial velocity of the circulated medium was 0.4 times lower than that of the conventional medium while their average radial velocities were almost the same (zero). The standard deviation of radial velocity fluctuation in the N-medium was also 0.4 times less than that in the conventional medium. These results suggest that turbulent flow occurred in the bioreactor culture using the conventional medium and the degree of turbulent flow decreased significantly when 0.8% CMC was added to the medium to prepare the N-medium. A change of the flow pattern is considered to be the cause of the decrease in hydrodynamic stress, resulting in enhanced pigment production due to the enlargement of the callus.

Performance of a shaking vessel-type bioreactor with a current pole

The performance of a shaking vessel-type bioreactor with a current pole at its central axis was examined experimentally with respect to particle dispersion, power consumption, and solid-liquid mass transfer coefficient. The current pole improved the particle dispersion without an increase in power consumption and reduced the critical circulating frequency for complete suspension. The mass transfer coefficient with a current pole had the same value as that without a current pole above the critical circulating frequency for complete suspension. The shaking vessel-type bioreactor with a current pole was thus very suitable for the mass production of regenerated plantlets from fragmented horseradish hairy roots.

Miscible viscous fingering involving viscosity changes of the displacing fluid by chemical reactions

In our previous study, we experimentally studied the effects of changes in the viscosity of the displaced more-viscous liquid by instantaneous reactions on miscible viscous fingering pattern [Y. Nagatsu, K. Matsuda, Y. Kato, and Y. Tada, “Experimental study on miscible viscous fingering involving viscosity changes induced by variations in chemical species concentrations due to chemical reactions,” J. Fluid Mech. 571, 475 (2007)]. In the present study, experiments have been performed on the miscible viscous fingering involving changes in the viscosity of the displacing less-viscous liquid by instantaneous reactions in a radial Hele-Shaw cell. We have found that the shielding effect is suppressed and the fingers are widened when the viscosity is increased. As a result, the reaction makes the fingering pattern denser. In contrast, the shielding effect is enhanced, and the fingers are narrowed when the viscosity is decreased. As a result, the reaction makes the fingering pattern less dense. These results are ...

Miscible viscous fingering involving viscosity increase by a chemical reaction with moderate Damköhler number

In our previous study, we experimentally studied the effects of increased or decreased viscosity of the more-viscous liquid caused by chemical reactions at a very high Damkohler number, Da (defined as the ratio between a characteristic time of fluid motion and that of a chemical reaction), on miscible viscous fingering [Y. Nagatsu et al., “Experimental study on miscible viscous fingering involving viscosity changes induced by variations in chemical species concentrations due to chemical reactions,” J. Fluid Mech. 571, 475 (2007)]. In another study, we experimentally studied the effects of decreased viscosity caused by chemical reaction at a moderate Da on the fingering [Y. Nagatsu et al., “Effects of moderate Damkohler number on miscible viscous fingering involving viscosity decrease due to a chemical reaction,” J. Fluid Mech. 625, 97 (2009)]. In the present study, we investigated the effects of increased viscosity caused by chemical reaction at a moderate Da on the fingering in a radial Hele-Shaw cell. W...

Effect of ketanserin on lipoproteins in patients with essential hypertension.

Although antihypertensive drug therapy has decreased the incidence of cerebral accident, no apparent decrease in coronary artery disease has been achieved (Veterans Administration Cooperative Study Group 1970). The reason for this remains unknown, but unfavourable metabolic effects of some antihypertensive drugs, particularly thiazides and ~-blocking agents, are considered to be a contributing factor at least in part (Weidmann et al. 1985). Ketanserin is a newly developed antihypertensive drug which is a serotonin antagonist that binds primarily to Sz-serotonergic receptors (Hedner et al. 1983; Leyson et al. 1981). The antihypertensive effect ofketanserin has been established (Omvik & Lund-Johansen 1983; Wenting et al. 1982), but its effect on lipid metabolism is not well understood. This study was designed to evaluate the effect of ketanserin on lipids, lipoprotein lipids, high density lipoprotein (HDL) subfractions, HDL profile and apolipoproteins, as well as its antihypertensive efficacy in patients with mild to moderate essential hypertension. 1. Patients and Methods

Development of a Mixing Process Using an HB-Type Impeller to Easily Achieve Scale-Up by Maintaining Geometrical Similarity

In recent years, a novel home base-type (HB-type) impeller was developed to be based on observation of the streak line pattern. An HB impeller must be simple, speedy, and stable (3S). When an HB impeller is used on the laboratory beaker scale, the mixing performance of the HB impeller is better than that of a normal cylindrical stirring bar. In addition, an industrial-scale HB impeller has been constructed based on the observation of the streak line and isolated mixing regions in the vessel. The present authors believe that scale-up of the mixing process is very easy because the geometrical shape of the impeller can be kept consistent when scaling up from the laboratory scale to the industrial scale.