• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.515-521
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• 1998

In this study the mixing process of two-phase flow which makes two jets existing vlocity difference are analyzed. The primary jet is jetted on the condition of the state mixed pulverized solid pariticle with air and the velocity in the secondary jet is changed into three kinds velocities(0.60, 75m/s) The velocity vector field concentration field and turbulent properties of solid particles are measured by using 3-Dimensional Particles Dynamics Analyzer. As the velocity of secondary jet increases the solid particle recirculation zone becomes larger. Also solid particle concentration gets dense due to velocity decrement of particles.

• Journal of Welding and Joining
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• v.33 no.5
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• pp.14-19
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• 2015

This study has been performed to investigate the adhesive slag at GTAW weld zone after FCAW multi-pass welding. The cause of adhesive slag formation was examined using optical microscope, field emission scanning electron microscope(FE-SEM) and XRD analysis. The results obtained in this experiment are summarized as follows. Slag of GTAW weld zone surface during welding were formed by mixing the presence of slag in FCAW weld zone. While the slag cools, Cr-spinel phase were formed due to reactions in slag/metal interface. Also, a Cr moves form the weld metal to the slag to strong affinity between oxide atoms and Cr atoms. Hence, detachability of slag was exacerbated by decreasing the interfacial tensions between slag and weld metal.

• Journal of the Korean Society of Safety
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• v.8 no.3
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• pp.19-25
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• 1993

This paper deals with the experimental study of the turbulent characteristics in the swirling coaxial Jets. In this research, the experimental study has been carried out to investigate the effects of swirl number and equivalence ratio on the flow characteristics in nonreacting flow field of the model combustor which symplifys the continuous type combustor for the practical use. Author particularly Intends to find out the fuel-air mixing In the recirculation zone In order to make sure the effects of swirl number and equivalence ratio on the stabilization of flame.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.3
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• pp.386-397
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• 2012

The stability and structure of bluff-body stabilized hydrogen flames were investigated numerically and experimentally. The velocity of coflowing air was varied from subsonic velocity to a supersonic velocity of Mach 1.8. OH PLIF images and Schlieren images were used for analysis. Flame regimes were used to classify the characteristic flame modes according to the variation of the fuel-air velocity ratio, into jet-like flame, central-jet-dominated flame, and recirculation zone flame. Stability curves were drawn to find the blowout regimes and to show the improvement in flame stability with increasing lip thickness of the fuel tube, which acts as a bluff-body. These curves collapse to a single line when the blowout curves are normalized by the size of the bluff-body. The variation of flame length with the increase in air flow rate was also investigated. In the subsonic coflow condition, the flame length decreased significantly, but in the supersonic coflow condition, the flame length increased slowly and finally reached a near-constant value. This phenomenon is attributed to the air-entrainment of subsonic flow and the compressibility effect of supersonic flow. The closed-tip recirculation zone flames in supersonic coflow had a reacting core in the partially premixed zone, where the fuel jet lost its momentum due to the high-pressure zone and followed the recirculation zone; this behavior resulted in the long characteristic time for the fuel-air mixing.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.1
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• pp.69-75
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• 2009

This paper studies the aerodynamic performance that the vent mixer-new conceptual supersonic mixer-showed with its geometric characteristics. The hole is 2 mm with 2 mm's distance from the wall in case 1 and with no distance in case 2. In case 3 die hole is 1 mm. Case 1 and case 2 showed the same total pressure recovery ratio, of which the case 3 was lower than that. While cases 1-3 had the same reattachment length, the shear layer was thicker in cases 1 and 2 than in case 3. Within the recirculation zone, cases 1 and 2 had lower pressure loss and higher velocity gradient difference than case 3-they enhance mixing between air and fuel. Separation bubble which is developed by the inflow into the recirculation zone has a significant effect on the total pressure recovery ratio in the combustor. Also separation bubble influences pressure distributions and recirculation flows in the recirculation zone. Therefore, inflow rate of air into the recirculation zone mainly affects the performance of vent mixer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1671-1678
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• 1996

In external chemical vapor deposition processes including VAD and OVD the distribution of flame-synthesized silica particles is determined by heat and mass transfer limitations to particle formation. Combustion gas flow velocities are such that the particle diffusion time scale is longer than that of gas flow convection in the zone of particle formation. The consequence of these effects is that the particles formed tend to remain along straight smooth flow stream lines. Silica particles are formed due to oxidation and hydrolysis. In the hydrolysis, the particles are formed in diffuse bands and particle formation thus requires the diffusion of SiCl$\_$4/ toward CH$\_$4//O$\_$2/ combustion zone to react with H$\_$2/O diffusing away from these same zones on the torch face. The conversion kinetics of hydrolysis is fast compared to diffusion and the rate of conversion is thus diffusion-limited. In the language of combustion, the hydrolysis occurs as a Burke-Schumann process. In selected conditions, reaction zone shape and temperature distributions predicted by the Burke-Schumann analysis are introduced and compared with experimental data available. The calculated centerline temperatures inside the reaction zone agree well with the data, but the calculated values outside the reaction zone are a little higher than the data since the analysis does not consider diffusion in the axial direction and mixing of the combustion products with ambient air. The temperatures along the radial direction agree with the data near the centerline, but gradually diverge from the data as the distance is away from the centerline. This is caused by the convection in the radial direction, which is not considered in the analysis. Spatial distribution of silica particles are affected by convection and diffusion, resulting in a Gaussian form in the radial direction.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.993-1000
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• 2023

Recently, enviromentally friendly natural substances derived from plants have been attracting attention as cosmetic materials, and research on various physiological activities of natural substances is being actively conducted. This study investigated the antioxidant, anti-inflammatory, moisturizing, and antibacterial effects of three types of extracts of mixtures containing different mixing ratios, Polygala tenuifolia, Angelica dahurica, and Elsholtzia splendens, known to have various physiological activities. The mixing ratio is 7 conditions (M1, 1:1:1; M2, 0.5:1.5:1; M3, 1.5:0.5:1; M4, 0.1:0.95:0.95; M5, 0.5:0.5:2; M6, 0.95 :1.95:0.1; M7, 1.45:0.1:1.45), and the optimal mixing ratio was confirmed for use as a cosmetic material. DPPH and ABTS radical scavenging activities showed scavenging abilities of 75.37% and 99.19%, respectively, at 1,000 ㎍/mL of M6. At a concentration of 200 ㎍/mL of M6, it showed 50% of nitric oxide production inhibition compared to the lipopolysaccharide-treated that induced an inflammatory response. It was confirmed that M3 and M6 produced hyaluronic acid 1.47 and 1.49 times higher than the control at a concentration of 50 ㎍/mL, respectively. Through the disc diffiusion test, the clear zone was 9.75 mm at 8 ㎍/mL of M6, confirming the inhibition of growth of staplylococcus aureus strain. Based on the above results, it is believed that the mixed extract of Polygala tenuifolia, Angelica dahurica, and Elsholtzia splendens can be used as a functional natural material for cosmetics.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.5
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• pp.359-367
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• 2011

The Process of Pressurized water diffusion is mixing process by pressurized water injection with coagulate and chlorine water in the water treatment system. The objectives of this research were to evaluate the mixing length and diameter of diffusion plate and distance from injection pipe for complete mixing by using computational fluid dynamics. From the results of CFD simulation, when diameter of injection pipe is 50 mm, 100 mm and injection pressure is $5kg/cm^2$ and the diameter of inlet pipe is 2,200 mm, the complete mixing length is 4D (D: Length as diameter of inlet pipe). When diameter of injection pipe is 50 mm, the diameter of the diffusion plate in o.1D and distance from injection pipe is 0.2D, the complete mixing length is 3D that is the most short mixing length. But when diameter of injection pipe is 100 mm and mutually related the diameter, distance of diffusion plate, the complete mixing length is 4D over. Therefore, as the diameter of inlet pipe is 2,200 mm, the injection pipe 50 mm is more efficient than 100 mm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.683-693
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• 2013

In this study, the mixing characteristics in lid-driven cavity flows were studied numerically by using a hybrid lattice Boltzmann method (HLBM). First, we compared the numerical results from single-relaxation-time (LB-SRT) and multi-relaxation-time (LB-MRT) models to examine their reliability. In most of the cavity flow, the results from both the LB-SRT and the LB-MRT models were in good agreement with those using a Navier-Stokes solver for Re=100-5000. However, the LB-MRT model was superior to the LB-SRT model for the simulation of higher Reynolds number flows having a geometrical singularity with much lesser spatial oscillations. For this reason, the LB-MRT model was selected to study the mass transport in lid-driven cavity flows, and it was demonstrated that mass transport in the fluid was activated by a recirculation zone in the cavity, which is connected from the top to the bottom surfaces through two boundary layers. Various mixing characteristics such as the concentration profiles, mean Sherwood (Sh) numbers, and velocity were computed. Finally, the detailed transport mechanism and solutions for the concentration profile in the cavity were presented.

• The Journal of Engineering Geology
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• v.13 no.1
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• pp.17-27
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• 2003

In this study, a phenomenon of saltwater intrusion was monitored under various conditions regarding recharge and pumping rate using time domain reflectometry for a laboratory scale unconfined aquifer to verify the basic theory behind seawater intrusion and to investigate movement of salt-freshwater interface in accordance with the ratio of pumping and recharge rate. Results showed that a thick mixing zone was formed at the boundary instead of a sharp salt-freshwater interface that was assumed by Ghyben and Herzberg who derived an equation relating the water table depth $(H_f)$ to the depth to the interface $(H_s)$. Therefore our experimental results did not agree with the calculated values obtained from the Ghyben and Herzberg equation. Position of interface which was adopted as 0.5 g/L isochlor moved rapidly as the Pumping rate $(Q_p)$ increased for a given recharge rate $(Q_r)$. In addition, interface movement was found to be about 7 times the ratio of $Q_p/Q_r$ in our experimental condition. This indicates that Pumping rate becomes an important factor controlling the seawater intrusion in coastal aquifer.