• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.937-944
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• 1999

The near-wall flow structures of turbulent boundary layer over riblets having semi-circular grooves were investigated experimentally for the drag decreasing ($s^+=25.2$) and drag increasing ($s^+=40.6$) cases. The field of view used for tho velocity field measurement was $6.75{\times}6.75mm^2$ in physical dimension, containing two grooves. One thousand instantaneous velocity fields over the riblets were extracted for each case of drag increase and decrease. For comparison, five hundreds instantaneous velocity fields over a smooth flat plate were also obtained under the same flow conditions. To see the global flow structure qualitatively, the flow visualization was also performed using the synchronized smoke-wire technique. For the drag decreasing case ($s^+=25.2$), most of the streamwise vortices stay above the riblets, interacting with the riblet tips. The high-speed in-rush flow toward the riblet surface rarely influences the flow inside tho riblet valleys submerged in the viscous sublayer. The riblet tips seem to impede the spanwise movement of the longitudinal vortices and induce secondary vortices. The turbulent kinetic energy in the riblet valley is sufficiently small to compensate the increased wetted area of the riblets. In addition, in the logarithmic region, the turbulent kinetic energy are small or almost equal to that of a smooth flat plato. For the drag increasing case ($s^+=40.6$), however, the streamwise vortices move into the riblet valley freely, interacting directly with the riblet inner surface. The penetration of the high-speed in-rush flow on the riblets increases tho skin-friction. The turbulent kinetic energy is increased in the riblet valleys and even in the outer region compared to that over a flat plate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.10
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• pp.914-921
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• 2005

In this study, the 1/20 reduced-scale experiment using Froude scaling were conducted to investigate the effect of longitudinal ventilation velocity on the burning rate in tunnel fires. The methanol pool fires with heat release rate ranging from 2.02 kW to 6.15 kW and the n-heptane pool fires with heat release rate ranging from 2.23 kW to 15.6 kW were used. The burning rate of fuel was obtained by measuring the fuel mass at the load cell. The temperature distributions were observed by K-type thermocouples in order to investigate smoke movement. The ventilation velocity in the tested tunnel was controlled by inverter of the wind tunnel. In methanol pool fire, the increase in ventilation velocity reduces the burning rate. On the contrary in n-heptane pool fire, the increase in ventilation velocity induces large burning rate. The reason for above conflicting phenomena lies on the difference of burning rate. In methanol pool fire, the cooling effect outweighs the supply effect of oxygen to fire plume, and in n-heptane pool vice versa.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.809-822
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• 2018

A quantitative risk assessment has been introduced to quantitatively evaluate fire risk as a means of performance based fire protection design in the design of railway tunnel disaster prevention facilities. However, there are insufficient studies to examine the effect of various risk factors on the risk. Therefore, in this study, the risk assessment was conducted on the model tunnel in order to examine the effects of the evacuation start time delay and the fire growth curve on the quantitative risk assessment. As a result of the analysis of the scenario, the fatalities occurred mainly when escapes in the same direction as the direction of the fire smoke movement. In addition, after the FED exceeded 0.3, the maximum fatalities occurred within 10 minutes. In the range of relatively low risk, distance between cross passages, evacuation delay time and fire growth curve were found to affect the risk, but they were found to have little effect on the condition that the risk reached the limit. Especially, in this study, it was evaluated that the evacuation delay time reduction, fire intensity and duration reduction effect were not observed when the distance between cross passages was more than 1500 m.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.1
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• pp.43-49
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• 2010

The escape connecting gallery in a tunnel on a road is one of emergency equipment to ensure safety for passer in the tunnel against the tunnel fire. Government stipulate over 500m tunnel has the cross passage at intervals of less then 250 m. However, this lump estimated interval is generated the concerns of exaggeration and under construction because peculiarity of the tunnel ex. The velocity of the tunnel airflow, an incline, degree of a fire, and innering area are not considered. The study indicate the way to estimate of the cross passage considered an incline and the velocity of the tunnel airflow for efficient application of cross passage on the tunnel design. As a result, in 0.0 m/s and 1.0 m/s of the velocity of the tunnel airflow case, the movement of smoke is influenced by the incline however, in 20 m/s case, it isn't influenced by incline much. According to the velocity of tunnel airflow and the incline, optimum interval of cross passage is not corresponded. Therefore established lump estimate that has 250 m intervals would be changed to estimate of optimum interval of cross passage that considered about the properties of tunnel, the velocity of the tunnel airflow, incline, degree of a fire and innering area of the tunnel.

• Journal of Korean Theatre Studies Association
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• no.53
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• pp.31-56
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• 2014

If we define theatre as an infinite tower piled up by smoke, the strata of the organic composition of an actor's/actress' body-mind-spirit, may not only be complicatedly worked out, but it seems to belong to a non-scientific realm. However and at the same time, it is also true that the audience is eager to witness a certain kind of specific vitality from the actor/actress on stage. Of course the vitality is hard to be prescribed. Simply we call it a texture of energy, nuance of existence, or much simpler, an actor's/actress' 'aura'. That is, the existential nuance of the actor/actress. The nuance, which is surging from the actor's/actress' authentic presence, ultimately comes out of, not the circumstantial interpretation of the production but the power of its integration. We can find from the works of Meyerhold, Grotowsky and Barba the theatrical fact that the actor's aura can be obtained by a kind of artificiality rather than innate characteristics of existence. These directors commonly regard theatre as the actor's/actress' theatre. Respectively choosing his own specific methods of expression, they unexpectedly meet in a same spot in which actor's/actress' theatre can be realized by the rediscovery of the actor's/actress's body-form. In other words, their approaching methods to theatre look alike, at least in that abandoning reserving any natural, unconscious, economic body-form of an actor/actress, they rather try to discover a certain kind of 'technical' body-form. The form which is totally non/un-conscious, unfamiliar and non-economical. Their research process explores an ideal body-form, and this thesis focuses on this point. For this work, I bring the notion of 'liminality' that connotes the praxis for essential presence of the actor/actress as well as the incubating time and space nacessary for his/her rebirth. And for developing this work, I ask: Could not the actor's/actress' consciousness and the spatiotemporal dimensions (s)he meets, be possibly defined as the core of liminality, only in case that (s)he requires them in the process of, either exploring the unfamiliar body or familiarising with the unfamiliar body-form? As I mentioned above, the three frontiers' theatrical journey is similar in part. For example, three all start from the actor's/actress' consciousness and then go through the body enlarged with it. Then they continue their journey, but different from one another. Meyerhold still uses the conscious body. But now he transforms it into a kind of mobilized sculptures. In comparison with Meyerhold's use of the consciousness, Grotowsky puts his emphasis on an autonomous body which, if necessary, cast away even the innate consciousness. Likewise, to Barba, theatre always starts from the actor/actress who has already taken off all kinds of conventions. (Conventions should be re-designed!) The actor/actress therefore recreates him/herself as his/her body-mind wears a new, unfamiliar, readjusted form and vitality. And then this restructured body-mind may unceasingly aim at exploring its vitalized 'positive organism', that is the waves of self-centering energy, an existential nuance, and an authentic (or maybe behavioral) expressiveness. Now it seems clear that the liminal process for the frontiers' theatrical journey could be equalized as a profound process of self-penetration, self-transformation, and self-realization. This thesis explores the mystic realm of liminality.