• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.895-905
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• 2001

This paper presents vector fields, three dimensional mean velocities, turbulent intensities, turbulent kinetic energy and Reynolds shear stresses measured in the X-Y plane of the gas swirl burner with a cone type baffle plate by using an X-type hot-wire probe. This experiment is carried out at the flow rates of 350 and 450ℓ/min which are equivalent to the combustion air flow rate necessary to release 15,000 kcal/hr in a gas furnace. The results show that the maximum axial mean velocity component exists around the narrow slits situated radially on the edge of a burner. Therefore, there is some entrainment of ambient air in the outer region of a burner. The maximum values of turbulent intensities occur around the narrow slits and in front of a burner up to X/R=1.5. Moreover, the turbulent intensity components show a relatively large value in the inner region due to the flow diffusion and mixing processes between the inclined baffle plate and the swirl vane. Consequently, the combustion reaction is expected to occur actively near these regions.

• Tribology and Lubricants
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• 제33권6호
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• pp.251-255
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• 2017

In this study, we aimed to clarify the wettability and anisotropic flow characteristics of rice leaves as a basic study for engineering applications of anisotropic flow characteristics of rice leaf surface. To investigate the surface structure of rice leaf, the micro grooves and asperities of rice leaves were analyzed and quantified by scanning electron microscope, Confocal laser scanning microscopy, and stylus profilometer. The analysis of the structure of rice leaf surface confirmed that asymmetrical cone - like protrusions in leaf veins were inclined toward the leaf tip. The static contact angle test showed that the contact angle at the midline vein or leaf vein location where the micropapilla is concentrated is about $20^{\circ}$ higher than the leaf blade position. The contact angles of fresh and dried rice leave were also compared. The dried rice leaves showed a contact angle of about $5^{\circ}$ to $15^{\circ}$ higher than that of fresh leaves, suggesting that the volume of the protrusions decreased as the water was removed, thus reducing the contact area with the droplet. In the contact angle history test the hysteresis in the leaf tip direction was found to be much lower than that in the leaf petiole direction. This results can be explained that asymmetrical cone - like protrusions had a significant effect on the droplet flow characteristics through contact angle hysteresis experiment.

• 상하수도학회지
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• 제21권1호
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• pp.57-63
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• 2007

In this study, the cone type baffle (CTB) was developed to improve the flow distribution in an upflow bioreactor. It was composed of two different zones (anoxic and oxic) by inserting the CTB in the middle of the bioreactor. Based on the results of the dye tracer tests, hydraulic retention time (HRT) for the anoxic, oxic and total volume of the bioreactor was found to be 0.998, 1.996 and 2.994 hr, respectively. And the theoretical HRT for each volume was 1.0, 2.0 and 3.0 hr, respectively. The values of HRT obtained from the tests coincide with theoretical values. Therefore, the flow pattern for each zone inside the bioreactor, which was divided by the CTB, was dominated by complete mix flow rather than plug flow. Based on the results of the transection measurements, the DO concentration for each zone inside the bioreactor was clearly distinguished. Consequently, the CTB played an important role in the separation of anoxic and oxic zones. Also, the each pollutans were reduced gradually along the height in the oxic zone. The reason is that the biomass in the media layer (Port 4 and 5) was higher than that in the mixed liquor layer without the media (Port 2 and 3).

• 한국전산유체공학회지
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• 제13권2호
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• pp.8-13
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• 2008

A supersonic viscous flow over a five-degree half-angle cone is studied computationally with three-dimensional Navier-Stokes equations. Steady asymmetric solutions show that the asymmetric flow separation is caused by convective instability. The effects of angle of attacks, Reynolds numbers, and Mach numbers have been investigated and it is found that those factors affect the generation of the side force. The side force has the maximum value at ${\alpha}=22^{\circ}$, while over ${\alpha}=22^{\circ}$, asymmetric vortex becomes transient, which results in the unsteady shedding. At the angle of attack of 22 degrees, the side force increases with Reynolds number and decreases with Mach number. The increase of the side force stops over the critical Reynolds number for the present configuration.

• 한국항공운항학회지
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• 제14권1호
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• pp.43-48
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• 2006

The present study was carried out in order to develope a seven-hole pressure probe which is able to measure high flow angles. The seven-hole pressure probe is a non-nulling, directional velocity probe used for measuring three dimensional flow that having high flow angles. A 4 mm diameter seven-hole conical pressure probe was manufactured with a cone angle of 70$^{\circ}$. The probe was comprised of seven 1 mm diameter stainless steel tubes packed close together and fitted into an outer stainless steel sleeve. The calibration procedure is based on the use of the Callington's polynomial curve-fit method. The validity of the seven-hole conical pressure probe is demonstrated by comparisons with hot-wire data.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.414-417
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• 2004

A cone cylinder is used to obtain variable operation conditions for the sonic ejector-diffuser system. The cone cylinder is designed to be shifted upstream and downstream to change the ejector throat area ratio, thus obtaining variable mass flow rates. The present study investigates the effects of ejector throat area ratio and operating pressure ratio on the entrainment of secondary stream for the variable sonic ejector system. The study is carried out experimentally. The ejector throat area is varied at the range from Ψ= 11.88 to 66.69, and the operating pressure ratio is changed from $P_{op}$ / $P_{a}$=1.25 to 9.0. The results show that the variable sonic ejector system can be operated to obtain specific entrainment ratio of secondary stream by altering the ejector throat area ratio and operating pressure ratio.o.

• 한국분무공학회지
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• 제27권1호
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• pp.26-35
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• 2022

Electrospray is a method of atomizing fluid using high voltage supply and capable of generating continuous flow and coherent size of droplets. Electrical system and properties of fluids has enabled electrospray to have various spray modes. However, its studies have been confined only in Cone jet, which is more stable and easier to manipulate droplets' size than other spraying modes. Therefore, it is necessary to investigate and compare other spraying modes based on experimental parameters and physical properties of fluids. This research paper identified nine different spray modes. It was found out that Sauter Mean Diameter (SMD) is proportional to flow rate of fluids and maximum difference among spray modes was 1.7 times. On the other hand, SMD standard deviation had low variations on specific flow rates of fluids. Pulsed jet mode recorded the largest SMD standard deviation, while Spindle recorded the lowest.

• Computers and Concrete
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• 제2권2호
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• pp.97-110
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• 2005

Rheological behaviour of fresh concrete is an important factor in controlling concrete quality. It is recognized that the measurement of the slump is not a sufficient test method to adequately characterize the rheology of fresh concrete. To further understand the slump measurement and its relationship to the rheological properties, an elasto-viscoplastic, 2-D axisymmetric finite element (FE) model is developed. The FE model employs the Bingham material model to simulate the flow of a slump test. An experimental program is carried out using the Slump Rate Machine (SLRM_II) to evaluate the finite element simulation results. The simulated slump-versus-time curves are found to be in good agreement with the measured data. A sensitivity study is performed to evaluate the effects of yield stress, plastic viscosity and cone withdrawal rate on the measured flow curve using the FE model. The results demonstrate that the computed yield stress compares well with reported experimental data. The flow behaviour is shown to be influenced by the yield stress, plastic viscosity and the cone withdrawal rate. Further, it is found that the value of the apparent plastic viscosity is different from the true viscosity, with the difference depending on the cone withdrawal rate. It is also confirmed that the value of the final slump is most influenced by the yield stress.

• 한국전산유체공학회지
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• 제17권3호
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• pp.18-24
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• 2012

The aerodynamic performance of the pantograph on a high speed train was compared for different pantograph covers which are designed to block the aero-acoustic noise from the pantograph. For the study, two types of cover are designed: wedge and cone types. The lift force of pantograph with cover was compared with the force of pantograph only. The comparison clarified that the cone type cover increases the sideslip angle of the flow and decreases the lift force considerably. However, the wedge type cover changes the flow direction upward and increases the lift force of the pan head. This increment of lift force compensates the decrement of lift force caused by the blocking of the flow into the pantograph lower frame due to cover. Therefore, in case of the wedge type cover, the overall lift force changes slightly compared with the cone type cover.

• 설비공학논문집
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• 제9권1호
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• pp.55-63
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• 1997

A numerical investigation has been made for flows in an axisymmetric circular cylinder with an impulsively rotating cone located at the bottom of the container. The axisymmetric container is completely filled with a viscous fluid. Major parameter for the present research is only the vertex angle of the cone, otherwise Reynolds number and aspect ratio of the vessel are fixed. Main interest concerns on the vortex breakdown of meridional circulation by impulsive rotation of the cone with respect to the longitudinal axis of the cylinder. Numerical method has been used to integrate momentum and continuity equations on a generalized body-fitted grid system. The pattern of vortex breakdown is quite different from that in a right circular cylinder with flat endwall disks. The flow visualization photograph of the preceeding work by Escudier is compared with the present numerical results and the two results are in good agreements. Also flow data are plotted to gain a deep understanding for the present phenomena of the vortex breakdown. The conclusions of this work are clearly explained by the classical theory of the vortex flows in a finite geometry.