hydrodynamic effects
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Author(s):  
Pol Torres ◽  
Stephen Wu ◽  
Shenghong Ju ◽  
Chang Liu ◽  
Terumasa Tadano ◽  
...  

Abstract Machine learning techniques are used to explore the intrinsic origins of the hydrodynamic thermal transport and to find new materials interesting for science and engineering. The hydrodynamic thermal transport is governed intrinsically by the hydrodynamic scale and the thermal conductivity. The correlations between these intrinsic properties and harmonic and anharmonic properties, and a large number of compositional (290) and structural (1224) descriptors of 131 crystal compound materials are obtained, revealing some of the key descriptors that determines the magnitude of the intrinsic hydrodynamic effects, most of them related with the phonon relaxation times. Then, a trained black-box model is applied to screen more than 5000 materials. The results identify materials with potential technological applications. Understanding the properties correlated to hydrodynamic thermal transport can help to find new thermoelectric materials and on the design of new materials to ease the heat dissipation in electronic devices.to ease the heat dissipation in electronic devices.


Soft Matter ◽  
2022 ◽  
Author(s):  
Emmanuel Hitimana ◽  
Brittany K. Roopnarine ◽  
Svetlana Morozova

Hydrodynamic effects influence the dynamics of nanoparticles in confined geometries.


2021 ◽  
Vol 9 (12) ◽  
pp. 1459
Author(s):  
Qingze Gao ◽  
Lifei Song ◽  
Jianxi Yao

The wave-induced motions, and steady wave forces and moments for the oil tanker KVLCC2 in regular head and oblique waves are numerically predicted by using the expanded RANS solver based on OpenFOAM. New modules of wave boundary condition are programed into OpenFOAM for this purpose. In the present consideration, the steady wave forces and moments include not only the contribution of hydrodynamic effects but also the contribution of the inertial effects due to wave-induced ship motions. The computed results show that the contribution of the inertial effects due to heave and pitch in head waves is non-negligible when wave-induced motions are of large amplitude, for example, in long waves. The influence of wave amplitude on added resistance in head waves is also analyzed. The dimensionless added resistance becomes smaller with the increasing wave amplitude, indicating that added resistance is not proportional to the square of wave amplitude. However, wave amplitude seems not to affect the heave and pitch RAOs significantly. The steady wave surge force, sway force and yaw moment for the KVLCC2 with zero speed in oblique waves are computed as well. The present RANS results are compared with available experimental data, and very good agreements are found between them.


Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7522
Author(s):  
Linqing Bai ◽  
Pengcheng Zhang ◽  
Zulfiqar Ahmad Khan

Seal performance of a novel gas mechanical face seal with semi salix leaf textures was introduced and theoretically investigated with the purpose of enhancing hydrostatic and hydrodynamic opening performance. First, a theoretical model of a laser surface textured gas mechanical face seal with semi salix leaf textures was developed. Second, the impact of operating and texturing parameters on open force, leakage, and friction torque was numerically investigated and has been discussed based on gas lubrication theory. Numerical results demonstrate that the semi salix leaf textured gas face seal has larger hydrostatic and hydrodynamic effects than the semi ellipse textured seal because of the effect of the inlet groove. All semi salix leaf textured surfaces had better open performance than the semi ellipse textured surface, which means that the inlet groove plays an important role in improving open performance and consequently decreasing contact friction during the start-up stage. Texturing parameters also influenced the seal performance of thee semi salix leaf textured gas face seal. When the inclination angle was 50°, the radial proportion of the inlet groove was 0.8, the dimple number was 9, and the open force resulted in the maximum value. This research has demonstrated the positive effects of the applications of a semi salix leaf textured gas mechanical face seal that combines the excellent hydrostatic and hydrodynamic effects of groove texture and the excellent wear resistance of microporous textures.


2021 ◽  
pp. 142-148
Author(s):  
А.М. Резцова ◽  
П.Н. Звягин

Модельный эксперимент в ледовом бассейне позволяет выяснить ледовые качества проектируемого ледостойкого морского сооружения, в том числе – получить представление о возможных ледовых нагрузках путем измерений глобальных нагрузок многокомпонентным динамометром. Чувствительность применяемого оборудования приводит к появлению шумовых помех в измеренном сигнале, вызванных действиями людей, обслуживающих эксперимент, работой машин и механизмов, гидродинамическими эффектами, а также явлениями в электросети. Отделение шумовых помех от полезного сигнала на этапе обработки данных является важной задачей, успешное решение которой позволит повысить достоверность результатов испытаний в ледовом бассейне. В настоящей работе изложен подход к очистке от шума результатов измерений многокомпонентного динамометра, применяемого в ледовом бассейне Крыловского государственного научного центра (Санкт-Петербург), с использованием амплитудно-частотного анализа участков пробега модели по чистой воде в пределах технологического окна во льду. Предложенный метод показал свою эффективность, в особенности – для экспериментов с моделью больших размеров. A model experiment in an ice tank allows to examine ice qualities of a designed ice-resistant marine structure, namely possible ice loads by measuring global loads with a multicomponent dynamometer. The sensitivity of the equipment leads to the noise interference in the measured signal caused by people's actions carrying out the experiment, by the operation of machines and mechanisms, hydrodynamic effects, as well as the phenomenae in the electrical power grid. It is important to separate noise interference from the relevant signal at the data processing stage, which will increase the reliability of ice tank experiments. This paper describes a method for denoising measurement results of a multicomponent dynamometer used in the ice tank of the Krylov State Scientific Center (St. Petersburg); the approach implies an amplitude-frequency analysis of model run areas in ice-free water within the technological window in the ice. The proposed method has demonstrated its effectiveness, especially for experiments with large models.


2021 ◽  
Vol 9 (12) ◽  
pp. 1344
Author(s):  
Franck Schoefs ◽  
Michael O’Byrne ◽  
Vikram Pakrashi ◽  
Bidisha Ghosh ◽  
Mestapha Oumouni ◽  
...  

Hard marine growth is an important process that affects the design and maintenance of floating offshore wind turbines. A key parameter of hard biofouling is roughness since it considerably changes the level of drag forces. Assessment of roughness from on-site inspection is required to improve updating of hydrodynamic forces. Image processing is rapidly developing as a cost effective and easy to implement tool for observing the evolution of biofouling and related hydrodynamic effects over time. Despite such popularity; there is a paucity in literature to address robust features and methods of image processing. There also remains a significant difference between synthetic images of hard biofouling and their idealized laboratory approximations in scaled wave basin testing against those observed in real sites. Consequently; there is a need for such a feature and imaging protocol to be linked to both applications to cater to the lifetime demands of performance of these structures against the hydrodynamic effects of marine growth. This paper proposes the fractal dimension as a robust feature and demonstrates it in the context of a stereoscopic imaging protocol; in terms of lighting and distance to the subject. This is tested for synthetic images; laboratory tests; and real site conditions. Performance robustness is characterized through receiver operating characteristics; while the comparison provides a basis with which a common measure and protocol can be used consistently for a wide range of conditions. The work can be used for design stage as well as for lifetime monitoring and decisions for marine structures, especially in the context of offshore wind turbines.


Author(s):  
Serguei G. Kalmykov ◽  
Pavel S Butorin ◽  
Maxim E Sasin ◽  
Vasily Zakharov

Abstract Experiments on measuring absorption of an IR laser radiation in the laser-produced plasma of Xe are described. The absorbed fraction of up to 65% has been obtained when the gas-jet target was illuminated by a wide, defocused beam, whereas it barely reached 8.5% in the case of a sharply focused beam. The phenomenon is explained on the basis of a hypothesis of the plasma hydrodynamic expansion according to which the plasma leaves the illuminated area the faster, the smaller its size. Based on the experimental results, an attempt to estimate plasma parameters (N, T, <Z>) is undertaken, with the mean ion charge, <Z>, being calculated using ionization cross-sections for ions from +7Xe to +14Xe which were obtained by means of a quantum-mechanical numeric simulation especially for the present work. A similarity of the EUV output and the laser energy absorption as functions of the laser beam diameter needs an additional study in a future.


2021 ◽  
Vol 7 (1) ◽  
pp. 31
Author(s):  
Sergio Roget ◽  
Marcos Lema ◽  
Anne Gosset

The main objective of this work is the development of a Computational Fluid Dynamics model coupled with a structural code for the simulation and optimization of fishing gears. As fishing nets are highly deformable structures under the influence of incident water, the use of merely empirical correlations for hydrodynamic forces, such as those used in many structural codes, does not provide precise predictions for their behaviour. The coupling between the structural problem and the hydrodynamic effects makes it necessary to tackle the problem through a new “fluid–structure interaction” approach, which is described here. Preliminary results obtained with the CFD model are also presented.


2021 ◽  
Vol 880 (1) ◽  
pp. 012015
Author(s):  
Samera Samsuddin Sah ◽  
Khairul Nizam Abdul Maulud ◽  
Nurul A’idah Abd Rahim ◽  
Othman A. Karim ◽  
Suraya Sharil

Abstract Kuala Kedah is a coastal area where the majority of the community are paddy farmers and fishermen. Almost the entire coastal area is used as a paddy cultivation area. However, this area faces the threat of seawater intrusion into land due to climate change driven sea-level rise. The rising seawater has affected the surrounding area, not only in terms of crop yields but also property and livelihood to the locals. Therefore, this study is designed to detect and analyze the progress of seawater on land at the Kuala Kedah coastal area using a hydrodynamic approach. Mike 21 software was used to simulate the hydrodynamic effects on 2 segments (NA and SA) in this study area by considering two conditions namely Condition 1 (K1) and Condition 2 (K2) which are respectively with and without coastal protection structure. However, this structure was only built along the 2.5 km shoreline in the NA segment and not in the SA segment. The findings show that the coastal protection structure in K2 is effective in reducing 50 % of the impact of sea level rise in year 2100 at NA segment, while only 10 % at SA segment. Therefore, the construction of these structures permanently should be given consideration by local authorities in planning future development to ensure lowland areas are protected from coastal floods.


2021 ◽  
Vol 927 ◽  
Author(s):  
Yinuo Yao ◽  
Craig S. Criddle ◽  
Oliver B. Fringer

We study the effects of fluid–particle and particle–particle interactions in a three-dimensional monodispersed reactor with unstable fluidization. Simulations were conducted using the immersed boundary method for particle Reynolds numbers of 20–70 with an Archimedes number of 23 600. Two different flow regimes were identified as a function of the particle Reynolds number. For low particle Reynolds numbers ( $20 < Re_p < 40$ ), the porosity is relatively low and the particle dynamics are dominated by interparticle collisions that produce anisotropic particle velocity fluctuations. The relative importance of hydrodynamic effects increases with increasing particle Reynolds number, leading to a minimized anisotropy in the particle velocity fluctuations at an intermediate particle Reynolds number. For high particle Reynolds numbers ( $Re_p > 40$ ), the particle dynamics are dominated by hydrodynamic effects, leading to decreasing and more anisotropic particle velocity fluctuations. A sharp increase in the anisotropy occurs when the particle Reynolds number increases from 40 to 50, corresponding to a transition from a regime in which collision and hydrodynamic effects are equally important (regime 1) to a hydrodynamic-dominated regime (regime 2). The results imply an optimum particle Reynolds number of roughly 40 for the investigated Archimedes number of 23 600 at which mixing in the reactor is expected to peak, which is consistent with reactor studies showing peak performance at a similar particle Reynolds number and with a similar Archimedes number. Results also show that maximum effective collisions are attained at intermediate particle Reynolds number. Future work is required to relate optimum particle Reynolds number to Archimedes number.


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