Engineering and Informaticshttp://hdl.handle.net/10454/4132021-04-15T10:46:52Z2021-04-15T10:46:52ZGate-opening criterion for generating dam-break flow in non-rectangular wet bed channelsYang, S.Wang, B.Guo, YakunZhang, J.Chen, Y.http://hdl.handle.net/10454/184222021-04-10T01:19:04Z2020-11-01T00:00:00ZYang S, Wang B, Guo Y et al (2020) Gate-opening criterion for generating dam-break flow in non-rectangular wet bed channels. Energies. 13(23): 6280.
A sudden dam failure is usually simulated by the rapid removal of a gate in laboratory tests and numerical simulations. The gate-opening time is often determined according to the Lauber and Hager instantaneous collapse criterion (referred to as Lauber-Hager criterion) established for a rectangular open channel with a dry bed. However, this criterion is not suitable for non-rectangular channels or initial wet-bed conditions. In this study, the effect of the gate-opening time on the wave evolution is investigated by using the large eddy simulation (LES) model. The instantaneous dam break, namely the dam break without a gate, is simulated for comparison. A gate-opening criterion for generating dam-break flow in non-rectangular wet bed channel is proposed in this study, which can be used as an extension of the Lauber-Hager criterion and provides a more comprehensive and reasonable estimate of the gate opening time.
2020-11-01T00:00:00ZElement failure probability of soil slope under consideration of random groundwater levelLi, Z.Chen, Y.Guo, YakunZhang, X.Du, S.http://hdl.handle.net/10454/184212021-04-10T01:18:51Z2021-01-01T00:00:00ZLi Z, Chen Y, Guo Y et al (2021) Element failure probability of soil slope under consideration of random groundwater level. International Journal of Geomechanics. Accepted for Publication.
The instability of soil slopes is directly related to both the shear parameters of the soil material and the groundwater, which usually causes some uncertainty. In this study, a novel method, the element failure probability method (EFP), is proposed to analyse the failure of soil slopes. Based on the upper bound theory, finite element discretization, and the stochastic programming theory, an upper bound stochastic programming model is established by simultaneously considering the randomness of shear parameters and groundwater level to analyse the reliability of slopes. The model is then solved by using the Monte-Carlo method based on the random shear parameters and groundwater levels. Finally, a formula is derived for the element failure probability (EFP) based on the safety factors and velocity fields of the upper bound method. The probability of a slope failure can be calculated by using the safety factor, and the distribution of failure regions in space can be determined by using the location information of the element. The proposed method is validated by using a classic example. This study has theoretical value for further research attempting to advance the application of plastic limit analysis to analyse slope reliability.
2021-01-01T00:00:00ZThe fluid mechanics of tensioned web roll coatingBenkreira, HadjShibata, YusukeIto, K.http://hdl.handle.net/10454/184202021-04-15T08:18:43Z2021-01-01T00:00:00ZBenkreira H, Shibata, Y and Ito K (2021) The fluid mechanics of tensioned web roll coating. Chemical Engineering Science. 116612. Accepted for publication.
Tensioned web-roll coating is widely used but has surprisingly received little research attention. Here, a new semi-empirical model that predicts film transfer from applicator roller to web is developed and tested against data collected from a pilot coating line. The film transfer is found to vary linearly with web to applicator speed ratio S. Flow stability investigations revealed three types of defects: rivulets, air entrainment due to dynamic wetting failure and cascade, occurring at different values of S and capillary number Ca. Rivulets occurred at Ca< 0.4 and S> 0.71-0.81, air entrainment at Ca>0.4 and S>0.71-0.83 and cascades at S>1.1 for Ca up to 6. Web speeds at which dynamic wetting failure occurred were, for the same Ca, comparatively higher than those that occur in dip coating. The data show that such hydrodynamic assistance is due to the coating bead being confined, more so with increasing web wrap angle β.
2021-01-01T00:00:00ZTurbulence structure and momentum exchange in compound channel flows with shore ice covered on the floodplainsWang, F.Huai, W.Guo, YakunLiu, M.http://hdl.handle.net/10454/184192021-04-09T01:17:37Z2021-04-01T00:00:00ZWang F, Huai W, Guo Y et al (2021) Turbulence structure and momentum exchange in compound channel flows with shore ice covered on the floodplains. Water Resources Research. 57(4): e2020WR028621.
Ice cover formed on a river surface is a common natural phenomenon during winter season in cold high latitude northern regions. For the ice-covered river with compound cross-section, the interaction of the turbulence caused by the ice cover and the channel bed bottom affects the transverse mass and momentum exchange between the main channel and floodplains. In this study, laboratory experiments are performed to investigate the turbulent flow of a compound channel with shore ice covered on the floodplains. Results show that the shore ice resistance restricts the development of the water flow and creates a relatively strong shear layer near the edge of the ice-covered floodplain. The mean streamwise velocity in the main channel and on the ice-covered floodplains shows an opposite variation pattern along with the longitudinal distance and finally reaches the longitudinal uniformity. The mixing layer bounded by the velocity inflection point consists of two layers that evolve downstream to their respective fully developed states. The velocity inflection point and strong transverse shear near the interface in the fully developed profile generate the Kelvin-Helmholtz instability and horizontal coherent vortices. These coherent vortices induce quasi-periodic velocity oscillations, while the dominant frequency of the vortical energy is determined through the power spectral analysis. Subsequently, quadrant analysis is used in ascertaining the mechanism for the lateral momentum exchange, which exhibits the governing contributions of sweeps and ejections within the vortex center. Finally, an eddy viscosity model is presented to investigate the transverse momentum exchange. The presented model is well validated through comparison with measurements, whereas the constants α and β appeared in the model need to be further investigated.
2021-04-01T00:00:00ZAn improved distortion compensation approach for additive manufacturing using optically scanned dataAfazov, S.Semerdzhieva, E.Scrimieri, DanieleSerjouei, A.Kairoshev, B.Derguti, F.http://hdl.handle.net/10454/184252021-04-14T01:18:20Z2021-02-01T00:00:00ZAfazov S, Semerdzhieva E, Scrimieri D et al (2021) An improved distortion compensation approach for additive manufacturing using optically scanned data. Virtual and Physical Prototyping. 16(1): 1-13.
This paper presents an improved mathematical model for calculation of distortion vectors of two aligned surface meshes. The model shows better accuracy when benchmarked to an existing model with exceptional mathematical conditions, such as sharp corners and small radii. The model was implemented into a developed distortion compensation digital tool and applied to an industrial component. The component was made of Inconel 718 and produced by laser powder bed fusion 3D printing technology. The digital tool was utilised to compensate the original design geometry by pre-distortion of its original geometry using the developed mathematical model. The distortion of an industrial component was reduced from approximately ±400 µm to ±100 µm for a challenging thin structure subjected to buckling during the build process.
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