• 한국해안해양공학회지
• /
• 제1권1호
• /
• pp.8-14
• /
• 1989

파랑과 해류의 합성류에 의한 해저면 마찰력을 계산하기 위한 모델을 프란틀의 혼합거리이론을 이용하여 개발하였다. 본 모델은 여러 수치적인 적분값들을 약산식으로 구할 수 있게 만들었으므로 모든 해들을 양해법으로 바로 얻을 수 있다. 계산 결과를 현장 관측자료와 비교, 검토하였으며, 그 결과는 대체적으로 만족할만한 일치를 보였다.

• 한국해안해양공학회:학술대회논문집
• /
• 한국해안해양공학회 1991년도 정기학술강연회 발표논문 초록집
• /
• pp.6-10
• /
• 1991

The bottom friction model of combined wave-current flow developed by Bijker, Yoo and O'Conner (hereafter it is called BYO model) is fully based on the Prandtl's mixing length theory. Although the Prandtl's theory is dependant on some rationalism, it is widely recognized that the theory is generally acceptable for the description of any turbulent flow.(omitted)

• Korean Journal of Hydrosciences
• /
• 제8권
• /
• pp.1-17
• /
• 1997

Prandtl's mixing length theory was modified to obtain a power velocity distribution in which the coefficient and the exponent are variable over a range from : $$ A simple suspended-sediment concentration distribution was developed from the modified velocity distribytion : $ With nominal values of $\beta$=1.0, $\kappa$=0.4 and visual accumulation tube values of the fall velocity, the comparison between the theory and field measurements by the USGS on the Rio Grande is fair. Doubling the value of the exponent results in a good comparison. Further researches are needed for choosing the values of $\beta$, $\kappa$, and fall velocity values, and consideration on the effects of large-scale turbulence and secondary flows are necessary for them. In a pragmatic sense, on any gaging sites the close analysis of very detailed measurements can establish its specific coefficient and exponent.

• Korean Chemical Engineering Research
• /
• 제55권5호
• /
• pp.668-678
• /
• 2017

Intermolecular interactions were studied for binary mixtures of 2-propanol + cyclohexane, n-hexane, benzene, toluene, o-, m- and p-xylenes by measuring ultrasonic speeds (u) over the entire range of composition at 298.15 K and 308.15 K. From these results the deviation in ultrasonic speed was calculated. These results were fitted to the Redlich-Kister equation to derive the binary coefficients along with standard deviations between the experimental and calculated data. Acoustic parameters such as excess isentropic compressibility ($K_s^E$), intermolecular free length ($L_f$) and available volume ($V_a$) were also derived from ultrasonic speed data and Jacobson's free length theory. The ultrasonic speed data were correlated by Nomoto's relation, Van Dael's mixing relation, impedance dependence relation, and Schaaff's collision factor theory. Van Dael's relation gives the best prediction of u in the binary mixtures containing aliphatic hydrocarbons. The ultrasonic speed data and isentropic compressibility were further analyzed in terms of Jacobson's free length theory.

• 한국습지학회지
• /
• 제13권3호
• /
• pp.395-409
• /
• 2011

본 연구의 목적은 개수로에서 난류모의를 위한 2차원 모형을 개발하는데 있다. 연구모델은 Streamline Upwind / Petrov-Galerkin 유한요소법과 Boussinesq의 와점성이론을 기초로 하였는데, 수심적분을 취한 혼합거리 모형과 난류의 이방성과 국부평형의 조건을 적용하였다. 모형의 보정과 검증을 위해서 해석해와 관측자료를 활용하였다. 몇 가지 수치모의를 수행함으로써 난류모형의 민감도와 계산수행 능력을 확인할 수 있었다. 본 연구모형은 자연하천에서의 모형 적용성 확인을 위해서 한강유역에 적용하였고 모의치는 실측자료와 비교하였다. 개발된 모형은 자연하천에서의 관측자료와 비교적 잘 일치하는 것으로 나타났다. 결론적으로 본 연구의 2차원 유한요소모형은 개수로에서의 난류모의에 기초한 흐름분포에 있어 신뢰할만한 결과를 제공하는 것으로 나타났다.

• 대한기계학회논문집
• /
• 제6권4호
• /
• pp.331-340
• /
• 1982

Numerical analysis is made on the turbulent heat transfer with suspension of solid particles in circular tube with constant heat flux. The mean motion of suspending particles in mixture is treated as the secondary gas flow with virtual density and viscosity. Our modeling of turbulent transport phenomena of suspension flow is based on this assumption and conventional mixing length theory. This paper gives the evidence that the mixing length models can be extended to close the governing equations for two phase turbulent flow with solid boundary at a first order level. Results on Nusselt numbers obtained by analytical treatments are compared with available experimental data and discussed. They suggest that the most important parameters of two phase turbulent heat transfer phenomena are relative particle diameter to pipe diameter, gas-solid loading ratio, and specific heat of suspending material.

• 대한기계학회논문집
• /
• 제18권12호
• /
• pp.3377-3385
• /
• 1994

This paper introduces empirical correlations to obtain the gas/liquid flow rates and the spray drop size of low viscosity liquid injected by Y-jet twin-fluid atomizers. The gas flow rate is well correlated with the gas injection pressure and the mixing point pressure, based on the compressible flow theory. Similarly, the liquid flow rate is determined by the liquid injection pressure and the mixing point pressure, and a simple correlation for the liquid discharge coefficient at the liquid port was deduced from the experimental results. The mixing point pressure, which is one of the essential parameters, was expressed in terms of the gas/liquid flow rate ratio and the mixing port length. Disintegration and atomization mechanisms both within the mixing port and outside the atomizer were carefully re-examined, and a "basic" correlation form representing the mean diameter of drops was proposed. The "basic" correlation was expressed in terms of the mean gas density within the mixing port, gas/liquid mass flow rate ratio and the Weber number. Though the correlation is somewhat complicated, it represents the experimental data within an accuracy of ${\pm}15%$.EX>${\pm}15%$.

• 전기의세계
• /
• 제25권6호
• /
• pp.74-80
• /
• 1976

The temperature rise of the mortars while are being irradiated by ultrasonic waves and immersed in a liquid medium, are measured. The mixing ratios of sand to cement are varied for the different mortars. The results of the experiment are as follows, 1. The temperature rise of the mortar is decreased as themixing ration (S/C) is increased. 2. Thd temperature rise of the specimen is increased as its length is increased. 3. The surface conditions, either smooth or rough, may not have much influence on the temperature rise of the mortar. 4. The initial slope of temperature rise may not have much effect of the viscosity of liquid. The results, describes above, appear well coincide with the theory that the temperature rise is attributed mainly to the absorption heating. Since the absorption heating of the mortars varies with the mixing ratios of sand to cement, the strength of them would be estimated by means of irradiation of ultrasonic waves on the specimen.

• Bulletin of the Korean Chemical Society
• /
• 제8권1호
• /
• pp.19-26
• /
• 1987

A statistical thermodynamical treatment for polymer adsorption from solution is presented. The canonical partition function for the polymer solution in the presence of a surface or an impermeable interface is formulated on the basis of usual quasi-crystalline lattice model, Bragg-Williams approximation of random mixing, and Pak's simple treatment of liquid. The present theory gives the surface excess ${\Gamma}_{exc}$ and the surface coverage ${\phi}^s_2$ of the polymer as a function of the chain length x, the Flory-Huggins parameter x, the adsorption energy parameter $x_s$, and polymer concentration $v_2$. Present theory is also applicable to the calculation of interfacial tension of polymer solution against water. For the idealized flexible polymer, interfacial tensions according to our theory fit good to the experimental data to the agreeable degrees.

• 한국해안해양공학회지
• /
• 제12권3호
• /
• pp.130-138
• /
• 2000

일방향흐름에 의한 해류의 마찰력 계산을 위하여 Prandtl의 혼합길이 이론을 수심 전구간에 적용하고 난류의 세기와 수리조건에 따라 완난류와 전난류로 분류하여 마찰계수를 산정하는 개수로 마찰계수 산정방법을 제시하였다. 파랑과 해류의 합성류에 의한 해저마찰력을 계산하기 위하여 두 유속의 연직분포를 고려한 BYO 모형을 이러한 흐름특성을 반영하여 개선하였다. BYO 모형은 모든 유속의 연직분포가 해저면으로부터의 직선과 접선으로 만나는 점(Bijker point)을 도출하여 파운동 유속과 해류유속의 합성을 이 점에서 시행하여 일주기의 평균갑을 구하는 모형이다. 일방향흐름의 해류나 천해파에 의한 파운동이나 해저면 가까이 경계층흐름은 완난류, 천이난류, 전난류 등 세가지 종류로 대별된다. 그 중 완난류로 대별하여 두 경우에 대한 합성류 마찰력 산정방법을 제시하였다.