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101.
Flow measurement around a model ship with propeller and rudder 总被引:1,自引:0,他引:1
For the design of hull forms with better resistance and propulsive performance, it is essential to understand flow characteristics, such as wave and wake development, around a ship. Experimental data detailing the local flow characteristics are invaluable for the validation of the physical and numerical modeling of computational fluid dynamics (CFD) codes, which are recently gaining attention as efficient tools for hull form evaluation. This paper describes velocity and wave profiles measured in the towing tank for the KRISO 138,000 m3 LNG carrier model with propeller and rudder. The effects of propeller and rudder on the wake and wave profiles in the stern region are clearly identified. The results contained in this paper can provide an opportunity to explore integrated flow phenomena around a model ship in the self-propelled condition, and can be added to the International Towing Tank Conference benchmark data for CFD validation as the previous KCS and KVLCC cases. 相似文献
102.
Coiled strip can be directly produced through the twin-roll strip casting process from the melt by incorporating casting and hot rolling together into a single step. In this unique process, the strip formation from the molten metal critically relies upon the casting rolls. Thus, the design of the rolls is extremely essential. The coupled heat transfer and deformation analysis of the casting roll is carried out in a two-dimensional numerical model, using a finite element program (MARC) to examine the thermal stress and displacement. The effects of several factors such as the nickel overlay thickness on the roll surface, the casting speed, and the roll diameter on thermal characteristics are investigated. 相似文献
103.
Yongfang Zhong Arindom Joardar Zhongping Gu Young-Gil Park Anthony M. Jacobi 《Experimental Thermal and Fluid Science》2005,29(8):957-970
A new method to assess the condensate drainage behavior of the air-side surface of compact heat exchangers—dynamic dip testing—is introduced. The new method is shown to provide highly repeatable data for real-time drainage. Results from experiments with more than 20 flat-tube and round-tube-and-fin heat exchangers are presented, and the data clearly show geometrical effects such as the impact of the tube type on condensate drainage. By comparing the results from dip testing to wind-tunnel experiments for the same heat exchangers, we find dip testing can serve as a powerful tool for assessing the condensate retention behavior. The coils retaining the most and the least condensate in a steady-state wind-tunnel test, likewise held the most and the least in a dip test. However, different amounts of water are retained on the air-side surface during dip tests and wind-tunnel tests. A model based on gravity, surface tension and drag effects is developed to help understand and predict the drainage behavior of heat exchangers. The new model and experimental approach are useful in screening heat exchangers for condensate retention and for assessing off-cycle drainage behavior. 相似文献
104.
The onset of convective instability in an initially quiescent, stably stratified fluid layer between two horizontal plates
is analyzed with linear theory. The bottom boundary is heated suddenly from below, subjected to a step change in surface temperature.
The critical time t
c to mark the onset of Rayleigh-Bénard convection is predicted by propagation theory. This theory uses the length scaled by
, where α denotes thermal diffusivity. Under the normal mode analysis the dimensionless disturbance equations are obtained
as a function of τ(=αt/d
2) and ζ(=Z/), where d is the fluid layer depth and Z is the vertical distance. The resulting equations are transformed to self-similar ones by using scaling and finally fixing
τ as τc under the frame of coordinates τ and ζ. For a given γ, Pr and τc, the minimum value of Ra is obtained from the marginal stability curve. Here γ denotes the temperature ratio to represent the degree of stabilizing
effect, Pr is the Prandtl number and Ra is the Rayleigh number. With γ=0, the minimum Ra value approaches the well-known value of 1708 as τc increases. However, it is inversely proportional to τc
3/2 as τc decreases. With increasing γ, the system becomes more stable. It is interesting that in the present system, propagation theory
produces the stability criteria to bound the available experimental data over the whole domain of time.
Received 5 November 2001 and accepted 29 March 2002 Published online: 2 October 2002
RID="*"
ID="*" This work has been supported by both SK Chemicals Co. Ltd. and LG Chemical Ltd., Seoul under the Brain Korea 21 Project
of the Ministry of Education.
Communicated by H.J.S. Fernando 相似文献
105.
Ki Byung Sunwoo Seung Joon Park Seong Jae Lee Kyung Hyun Ahn Seung Jong Lee 《Rheologica Acta》2002,41(1-2):144-153
Three-dimensional numerical simulation of viscoelastic coextrusion process has been performed and numerical results were
compared with the experimental data of Karagiannis et al. (1990). By varying the magnitude of the second normal stress difference
and its ratio of Fluid I and Fluid II, we were able to control the interface profile and the degree of encapsulation along
the downstream direction. By increasing the parameter α (αFluid I=αFluid II) from 0.1 to 0.4 in the Giesekus model and increasing the α ratio (αFluid IαFluid II) between Fluid I and Fluid II from 2.0 to 4.0 in the permissible range of realistic polymeric systems, the interface profile
and the degree of encapsulation along the downstream direction were fitted with the experimental results. There was little
difference between the numerical results and the experimental data in the interface profile and the degree of encapsulation
along the downstream direction when the α ratio was set to 3.0 (0.3:0.1). Fluid I with larger magnitude of the second normal
stress difference protrudes into Fluid II with smaller magnitude of the second normal stress difference around the symmetric
plane, while Fluid II wraps around Fluid I near the side walls. As the ξ
1
ratio (ξ
1
,Fluid Iξ
1
,Fluid II) increases from 1.0 to 3.0 for the two-mode Phan-Thien and Tanner model, it was found that the curvature of the interface
profile increased, and the difference between the numerical results and the experimental data in the interface profile and
the degree of encapsulation along the downstream direction was almost negligible when the ξ
1
ratio was set to 3.0 (0.54:0.18). Although the parameters of viscoelastic models were fitted by using the shear viscosity
data only, quantitative agreements between the numerical results and the experimental coextrusion data were quite satisfactory.
Received: 24 April 2001 Accepted: 5 June 2001 相似文献
106.
Ik Hyun Kwon Hye Ryoung Park Young Youp Song 《Russian Journal of Electrochemistry》2013,49(3):221-227
LiNi1 ? y Ti y O2 (0.000 ≤ y ≤ 0.100) and LiNi0.990M0.010O2 (M = Zn, Al, and Ti) were synthesized by the combustion method. The effects of Zn, Al and Ti substitution for Ni of LiNiO2 on the electrochemical properties of LiNiO2 were investigated. LiNi0.995Ti0.005O2 has the largest first discharge capacity (188.1 mA h/g) among the Ti-substituted samples. LiNi0.990Ti0.010O2 has a relatively large first discharge capacity (185.5 mA h/g) and a relatively good cycling performance. Among LiNi0.990M0.010O2 (M = Ni, Zn, Al, and Ti), LiNiO2 has the largest discharge capacities at a rate of 0.1 C from n = 1(189.3 mA h/g) to n = 10. LiNi0.990Al0.010O2 has the lowest discharge capacities from n = 1 to n = 10, but it has the best cycling performance. LiNi0.990Zn0.010O2 showed poor crystallinity, LiNi0.990Ti0.010O2 showed high cation mixing, and LiNi0.990Al0.010O2 had good crystallinity and showed low cation mixing. Fewer occurrence of phase transitions and the least change of the ?dx/|dV| vs. voltage curve at the second cycle from the curve at the first cycle of LiNi0.990Al0.010O2 suggest that Al substitution stabilizes the structure and leads to a good cycling performance. 相似文献
107.
Jinsoo Kim Jimin Park Young Ju Jung Eun Chol Kim Taek Ahn Jae-Won Ka 《Liquid crystals》2013,40(5):589-599
We have synthesised a series of new reactive mesogens with photopolymerisable di-acrylates and their corresponding non-reactive analogues based on the π-conjugated aromatic core, fluorene (F)-di-[thiophene (T)-benzene (B)], using the Stille and Suzuki coupling reaction. The effect of lateral alkyl chains on the 9-position of the central fluorene moiety as well as α, ω- side alkyl chains attached to the π-conjugated aromatic core on the mesomorphism was investigated by utilising differential scanning calorimetry (DSC) and polarising optical microscopy (POM). A wide angle X-ray scattering (WAXS) study at the various temperatures was also carried out to reveal phase structures. Photopolymerisable di-acrylates connected directly to the rigid aromatic core showed higher phase transition temperatures, probably due to the induced dipole moment in comparison with those of a non-reactive methyl–ether counterpart. 相似文献
108.
Polyimide‐silica (PI‐SiO2) hybrids were prepared from a novel polyimide (PI), derived from pyromellitic dianhydride (PMDA), 1,6‐bis(4‐aminophenoxy)hexane (synthesized) and 4,4′‐oxydianiline. SiO2 networks (5–30 wt%) were generated through sol–gel process using either tetraethylorthosilicate (TEOS) or a mixture of 3‐aminopropyltriethoxysilane‐PMDA‐based coupling oligomers (APA) and TEOS. Thin, free standing hybrid films were obtained from the respective mixtures by casting and curing processes. The hybrid films were characterized using Fourier transform infrared, 29Si nuclear magnetic resonance (NMR), field emission scanning electron microscopy (FE‐SEM), energy dispersive X‐ray spectrometry and atomic force microscopy (AFM) techniques. 29Si NMR results provide information about formation of organically modified silicate structures that were further substantiated by FE‐SEM and AFM micrographs. Contact angle measurements and thermogravimetric thermograms reveal that the addition of APA profoundly influences surface energy, interfacial tension, thermal stability and the residual char yield of modified hybrids in comparison to those obtained by mixing only TEOS. It was found that reduced particle size, efficient dispersion and improved interphase interactions were responsible for the eventual property enhancement. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
109.
Eun‐Ju Ha Bong‐Soo Kim Eun‐Kyoung Park Ki‐Won Song Sun‐Gu Lee Seong Soo A. An Hyun‐jong Paik 《先进技术聚合物》2013,24(1):75-80
Ni2+‐complexed poly(2‐acetamidoacrylic acid) (PAAA) hydrogel beads were developed for the site‐specific reversible immobilization and purification of the histidine‐tagged green fluorescent protein (His‐tagged GFP). PAAA hydrogel beads were prepared by photopolymerization, and significantly improved mechanical properties of PAAA hydrogel beads were observed in comparison with PAAA hydrogel from our previous study. Confocal laser scanning microscopy was used to determine the binding of His‐tagged GFP to the hydrogel beads in three‐dimensional space. Photoluminescence spectroscopy revealed 89% of binding efficiency of His‐tagged GFP to the Ni2+‐PAAA hydrogel beads, 51% of yielding recovery. The maximum binding capacity of His‐tagged GFP was estimated to be 0.45 µg/mg of Ni2+‐PAAA hydrogel beads. The recombinant His‐tagged GFP from the soluble fraction of E. coli BL21(DE3) cell lysates was purified with Ni2+‐PAAA hydrogel beads. The major advantage of the Ni2+‐PAAA hydrogel beads system was simple preparation procedures of producing the matrix, because PAAA hydrogel beads had relatively enhanced mechanical strength than soft hydrogels. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
110.
Branch length similarity (BLS) entropy is defined in a network consisting of a single node and branches. In this study, we mapped the binary time-series signal to the circumference of the time circle so that the BLS entropy can be calculated for the binary time-series. We obtained the BLS entropy values for “1” signals on the time circle. The set of values are the BLS entropy profile. We selected the local maximum (minimum) point, slope, and inflection point of the entropy profile as the characteristic features of the binary time-series and investigated and explored their significance. The local maximum (minimum) point indicates the time at which the rate of change in the signal density becomes zero. The slope and inflection points correspond to the degree of change in the signal density and the time at which the signal density changes occur, respectively. Moreover, we show that the characteristic features can be widely used in binary time-series analysis by characterizing the movement trajectory of Caenorhabditis elegans. We also mention the problems that need to be explored mathematically in relation to the features and propose candidates for additional features based on the BLS entropy profile. 相似文献