K. Kuratani, Yasunari Hashimoto, Kinji Oda et al. · JAXA Repository (JAXA) · 1984
Flow coefficient of injector elements having almost the same dimension with the injectors used for the test firing of full scale liquid hydrogen-oxygen rocket engines was studied. In these flow tests, water is used in place of liquid oxygen and the flow coefficient is derived from Bernoulli's equation. However, the value obtained by this procedure is not an universal constant and affected considerably by the experimental conditions. So that, in the liquid flow system, pressure difference at the injector DPOi was normalized by the down-stream pressure PC and the non-dimensional ratio of DPOi/PC was introduced as an useful parameter to describe the change of the flow coefficient reflecting the flow experimental conditions. In the gaseous flow, Fanno's equation was applied to derive the flow coefficient and the experimental results was described as the function of Mach number. In the liquid flow, the flow coefficient Cd shows a maximum at the low ratio DPOi/PC and the variation of Cd against DPOi/PC near the maximum was characterized by the injector designes. The other remarkable point of the liquid flow is indicated by the abrupt change induced by the cavitating flow. Therefore, it is important to carry out the flow test at the high down-stream pressure and to keep appropriate DPOi/PC value to presume the actual flow observed in the engine firing. In the gaseous flow system, the flow coefficient Cf is obtained as the function of Mach number M, and Cf starts from the low value and reaches to the constant high value as the increase of M. The coefficient Cf to be observed in the engine firing is able to estimate from the flow tests carried out at the ordinary ambient pressure using room temperature guseous nitrogen in place of cold hydrogen gas so far as the matching of M is realized in both cases. That is, there is no substantial change with the variation of fluid temperature in the range from 100 to 300 K. The possibility of the interference between the simultaneous flows of oxidant and fuel, in other words, the acceleration or deceleration of flow by the flow of the another component is denied within the flow conditions encountered in the firing tests of full scale engines.
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Yuelong Zhang · 2010
The calculation of flow plays an important role in the calculation of the turbine part.The flow coefficient is the very critical parameters,it has an important impact on the precision of flow According to inaccuracy of the flow coefficient and the velocity coefficient in the flow formula,the article amends the two coefficients,so that the flow coefficient and the velocity coefficients can be more precise.It improves the relationship of the two coefficients through accessing a correct amendment coefficient,while it makes the value of flow more accurate.
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Wayne J. Board, S. C. Spalding · AIChE Journal · 1966
Abstract The viewpoint is taken that bulk flow terms in the general equation of molecular diffusion must be measured in apparatus which offers no constraint to the molecular flux in either direction. It is proposed to carry this out in a miniaturized experiment operating with one side of the diffusion gradient as an infinite sink. Dimethyl acetamide–water diffusivities computed from such an experiment were found to be 7.02 × 10 −6 sq.cm./sec. over a wide range of compositions. These are compared with values showing considerably wider variation with composition, namely, 2.45 to 7.00 × 10 −6 sq.cm./sec. by estimating methods and 11.45 to 14.05 × 10 −6 sq.cm./sec. by large cell experiments. Arguments are presented in support of the values obtained by the proposed method operating on a nonideal binary N , N ‐dimethyl acetamide and water.
Cited by 4
Nagahiko Aikawa, Junji Kanazumi · Transactions of the Society of Instrument and Control Engineers · 1979
Flow coefficient measured by an area-type flowmeter can be represented as a function of the Reynolds number through a series of experiments. From the experimental results obtained in this study, it was clarified that the characteristic curve can be divied into three ranges, that is, the viscous flow range, the intermediate flow range and the nonviscous flow range depending on the value of the Reynolds number.At first, in the viscous flow range, laminar flow theory can be adoped suitably to the flow at the clearance between the taper-tube and float. Secondary, in the intermediate flow range, the values of the two sorts of coefficient, that is, one is that for geometry of the clearance between the taper-tube and the float and the other is that for the distribution of flow rate, were obtained as a function of the Reynolds number experimentally.And then, it was observed that the float with sharp edge was useful for the measurement of viscous flow.Furthermore, the nonviscous flow range seems to be a special case of the intermediate flow range because the nonviscous flow range corresponds to the case of an extremely, large Reynolds number in the intermediate flow range.From the discussions on the value of α done above, the following experimental equations were derived.Those equations are well representing the experimental results with a high degree of approximation.α=α0(Re/Re0)1/2for the viscous flow rangeα=α0(1-K/√Re)(-1N/√Re)for the intermediate flow rangewhere α; flow coefficientα0; flow coefficient of nonviscous flow rangeRe, Reθ; Roynalds number (Re0 is obtained through the experiment)K; coefficient of rate distribution depending on Reynold numberN; coefficient geometrical condition depending on Reynolds number
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V. P. Sokhan, N. Quirke · Physical Review E · 2008
The hydrodynamic solutions based on Maxwell's boundary conditions include an empirical slip coefficient (SC), which depends on properties of the adsorbate and adsorbent. Existing kinetic theory derivations of the SC are usually formulated for half-space flow and do not include finite-size effects, which dominate the flow in nanopores. We present an expression for the SC applicable to flow in nanoscale pores, which has been verified by nonequilibrium molecular-dynamics simulation. Our results show that the slip coefficient depends strongly on the pore width for small pores tending to a constant value for pores of width >20 molecular diameters for our systems, in contrast to the linear scaling predicted by Maxwell's theory of slip.
Cited by 39Open access
N. I. Khruslov · Measurement Techniques · 1982
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David C. Stone, Julian F. Tyson · Analytica Chimica Acta · 1986
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Nora Brambilla, Viljami Leino, Julian Mayer-Steudte et al. · Physical review. D/Physical review. D. · 2023
We calculate chromoelectric and chromomagnetic correlators in quenched QCD at $1.5{T}_{c}$ and ${10}^{4}{T}_{c}$, with the aim to estimate the heavy quark diffusion coefficient at leading order in the inverse heavy quark mass expansion, ${\ensuremath{\kappa}}_{\mathrm{E}}$, as well as the coefficient of the first mass-suppressed correction, ${\ensuremath{\kappa}}_{\mathrm{B}}$. We use gradient flow for noise reduction. At $1.5{T}_{c}$ we obtain $1.70\ensuremath{\le}{\ensuremath{\kappa}}_{\mathrm{E}}/{T}^{3}\ensuremath{\le}3.12$ and $1.03<{\ensuremath{\kappa}}_{\mathrm{B}}/{T}^{3}<2.61$. The latter implies that the mass-suppressed effects in the heavy quark diffusion coefficient are 20% for bottom quarks and 34% for charm quarks at this temperature.
Cited by 31Open access
Nora Brambilla, Viljami Leino, Julian Mayer-Steudte et al. · arXiv (Cornell University) · 2022
We calculate chromo-electric and chromo-magnetic correlators in quenched QCD at $1.5T_c$ and $10^4 T_c$ with the aim to estimate the heavy quark diffusion coefficient at leading order in the inverse heavy quark mass expansion, $κ_E$, as well as the coefficient of first mass suppressed correction, $κ_B$. We use gradient flow for noise reduction. At $1.5T_c$ we obtain: $1.70 \le κ_E/T^3 \le 3.12$ and $1.03< κ_B/T^3 < 2.61$. The latter implies that the mass suppressed effects in the heavy quark diffusion coefficient are 20% for bottom quarks and 34% for charm quark at this temperature.
Cited by 1Open access
Dragoljub Ivkovic, Slaven Zivkovic · Glasnik Sumarskog fakulteta · 2005
The delivery on time is not possible without the good-quality planning of deadlines, i.e. planning of the manufacturing process duration. The study of flow coefficient enables the realistic forecasting of the manufacturing process duration. This paper points to the significance of the study of flow coefficient on scientific basis so as to determine the terms of the end of the manufacture of chairs made of sawn timber. Chairs are the products of complex construction, often almost completely made of sawn timber as the basic material. They belong to the group of export products, so it is especially significant to analyze the duration of the production cycle, and the type and the degree of stoppages in this type of production. Parallel method of production is applied in chair manufacture. The study shows that the value of flow coefficient is close to one or higher, in most cases. The results indicate that the percentage of interoperational stoppage is unjustifiably high, so it is proposed how to decrease the percentage of stoppages in the manufacturing process.
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Andrey Zuev, A A Arngold, В А Левко et al. · IOP Conference Series Materials Science and Engineering · 2020
Abstract A model of the distribution of laminar temperature and dynamic boundary layers is considered. An integral relation is derived for the energy equation of the temperature spatial boundary layer, that allows integration over the surface of any shape, which is necessary for determining the thickness of the energy loss., The expressions for the thickness of the energy loss of the temperature spatial boundary layer are defined for the laminar flow. The expressions for the thickness of the energy loss are necessary to determine the local heat transfer coefficients for the characteristic cases of flow, taking into account heat transfer. Analytically, expressions are obtained for determining the local heat transfer coefficient in the form of the Stanton criterion for the rotational flow according to the law of a solid and the rotational flow of a free vortex. Local heat transfer coefficients are determined for laminar rotational flows.
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K. A. Pchelyakov, E. N. Leshin · Glass and Ceramics · 1984
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E.V. Glinyanaya · Journal of Stochastic Analysis · 2020
In this paper we give an upper bound for -mixing coefficient for a one-dimensional discrete-time stochastic flow with respect to the spatial parameter.
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Han‐Joon Kim, Kyung Soo Jun · Journal of Korea Water Resources Association · 2004
공간적 위치 및 유량 값에 따라 각 계산점마다 조도계수의 값이 달리 주어질 수 있도록 하는 가변 조도변수 부정류 계산모형을 수립하였다. 유량과 조도계수의 관계식으로는 계단함수 또는 멱함수를 적용할 수 있도록 하였다. 수립된 모형을 충주댐부터 팔당댐까지의 남한강 구간에 적용하여 최적화에 의한 매개변수의 추정을 수행하였다. 가변 매개변수 모형의 보정 결과, 계단함수 도형 및 멱함수 모형 모두 유량이 커질수록 조도계수가 감소하는 경향이 일관되게 나타났다. 이러한 경향은 여주 지점 상류구간의 경우에 더욱 현저한 것으로 나타났다. 가변 조도계수 모형의 매개변수 추정에 따른 오차가 고정 조도계수 모형의 경우보다 작아짐을 알 수 있었다. An unsteady flow model is developed that allows variable roughness coefficient for each computational point according to its spatial position and the discharge. A step function or a power function can be used for functional relation between the discharge and the Manning's roughness coefficient. The model is applied to the reach of the South Han River between the Chungju Dam and Paldang Dam, and model parameters are estimated by optimization. Estimated parameters of both the step function model and the Power function model show that Manning's roughness coefficient decreases as the discharge increases. This tendency is more noticeable for the upstream reach of Yeoju compared to the downstream reach. It turns out that the stages calculated by the variable roughness coefficient model agree better with the observed ones than those by the conventional fixed parameter model.
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Sang-Eun Jeon, Kook-Han Kim, Jin‐Keun Kim et al. · Journal of the Korea Concrete Institute · 2003
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Viljami Leino, Nora Brambilla, Julian Mayer-Steudte et al. · Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022) · 2023
The heavy quark diffusion coefficient is encoded in the spectral functions of the chromo-electric and the chromo-magnetic correlators, of which the latter describes the T/M contribution. We study these correlators at two different temperatures $T=1.5 T_c$ and $T=10^4 T_c$ in the deconfined phase of SU(3) gauge theory. We use gradient flow for noise reduction. We perform both continuum and zero flow time limits to extract the heavy quark diffusion coefficient. Our results imply that the mass suppressed effects in the heavy quark diffusion coefficient are 20% for bottom quarks and 34% for charm quark at $T=1.5T_c$.
Cited by 5Open access
Zhan Hu, M.J.F. Stive, T.J. Zitman et al. · Coastal Engineering Proceedings · 2012
Flow through vegetation has a significant impact on sediment transport and ecosystem robustness in the coastal and fluvial environment. Numerical models (Nepf and Vivoni, 2000; Uittenbogaaard, 2003) have been developed to simulate this type of flow. The success of these models depends on proper characterization of the main processes and appropriate setting of pre-defined empirical coefficients. Among others, the drag coefficient CD is one of the most important coefficients, which influences the mean velocity and the turbulence characteristics (Nepf and Ghisalberti, 2008).
 Tanino and Nepf (2008) and Cheng (2011) have derived empirical relationships of CD for flow through emerged rigid vegetation. Both studies confirm that CD is related to canopy properties (plants density, diameter, etc.) as well as flow conditions. However, in both studies CD is estimated by simply equating the vegetation drag force to the water level gradient. Bed shear stress and Reynolds stress were ignored. More importantly, the CD provided by these expressions is depth averaged, which is not suitable for modelling flow and canopy that both vary in vertical (Nepf and Vivoni, 2000). In this study, the CD relation proposed by Cheng (2011) is modified. This new relation depends on the local flow conditions and canopy properties in the vertical. Further, this relation is implemented in an iterative scheme of a 1DV flow model. The modelling results are compared with experiment data of flow through emerged and submerged rigid vegetation. Our results show that when special defined Reynolds number is small, this relation performs less well compare to that when it is larger.
Cited by 4Open access
Wawan Rauf, Rustan Tarakka, Jalaluddin Jalaluddin et al. · Universal Journal of Mechanical Engineering · 2020
Flow separation is expected to have the effect of increasing aerodynamic drag due to decreased pressure distribution at the rear of the vehicle. The faster the flow separation occurs, the lower the pressure distribution is in the area, thereby reducing vehicle performance. Therefore, flow modification is needed with expected effects on the separation delay and the reduction in wake and vortex formation. This modification can be done through the application of suction active control in the separation area. The research is intended to analyze the effect of suction active control on flow characteristics, pressure distribution and aerodynamic drag on vehicle models with suction velocity variations. The test model used is an Ahmed model modified by changing the orientation of the flow. The study used a numerical computational approach with a standard k-epsilon turbulence model at 19.4 m/s upstream velocity. Results revealed that the use of flow active control was able to reduce wake and vortex formation through separation delay and to increase the minimum pressure coefficient by 73% on the model with Usc<sub>2</sub> suction velocity of 0.5 m/s, gaining the highest drag coefficient reduction of 10.897% in the same model.
Cited by 9Open access
C.P. Wong, M.B. Vincent, Sheng Shi · IEEE Transactions on Components Packaging and Manufacturing Technology Part A · 1998
In the flip-chip on board assembly method, an underfill encapsulant material is applied in the gap between the integrated circuit (IC) chip and substrate to distribute the shear stresses at the solder interconnects. These shear stresses are imposed on the solder interconnects due to a coefficient of thermal expansion (CTE) mismatch between the IC chip and substrate. Different technologies such as fast-flow, no-flow, and reworkable underfills are currently being studied for flip-chip underfill encapsulant materials. This paper looks at the underfill encapsulant used in the fast-flow method of underfilling the IC chip/substrate gap. The effect of filler loading, particle size, and particle size distribution on the flow rate and CTE of the fast-flow underfill material are discussed in this work. The material used for the experiments is an epoxy resin with added silica filler to decrease the CTE. This study focuses on what effect different filler characteristics have on the underfill encapsulant. Also, an underfill encapsulant that can compete with one of industry's faster fast-flow underfills was developed as a result of this work.
Cited by 46
Hamid Hazby, M. V. Casey, Ryusuke Numakura et al. · Elsevier eBooks · 2014
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