Experimental and CFD Simulation Studies on the Flow Approaching a Type-A Piano Key Weir

<p>Many dams around the world are ageing and require upgradation in terms of spillway capacity and other safety aspects. In recent times, challenges faced due to global warming, climate change and cloudburst events have grown not just in numbers but also in extremity. Consequently, several dams and diversion structures are being modified to cope up with the floods resulting from such events. Piano key weir (PKW) has effectively been used in many dam upgradation projects, especially in France and Vietnam, to enhance the discharge capacity of the existing ogee-crested weirs or labyrinth weirs. It has also been used in a diversion scheme in India (Sawra Kuddu). The flow field around a PKW is spatially varied, complex and three-dimensional in nature. The previous researches on PKWs were predominantly focused on the effect of different parameters on its discharging capacity and limited studies are available on the flow field, sediment movement and scouring at PKWs. Considering these gaps, this study was initiated to understand the flow pattern near PKW and its effect on the sediment transport over PKW. Presented here is the experimental work carried out at IIT Roorkee, India on a Type-A PKW flume model with two discharge values, the CFD simulations of those two flow conditions and a comparison between the results. The time-averaged velocity values were measured at different locations in the front of inlet and outlet keys (upto a distance of 0.1 m from the bed level) using a 3D Acoustic Doppler Velocimeter. The simulations were performed in Ansys (academic 19.1) CFX solver using finite volume method, standard k-ε turbulent model, (where k denotes the turbulent kinetic energy and ε is the rate of dissipation of k) and multiphase (volume of fluid) modelling. The experimental results showed an increase in the depth-averaged longitudinal flow velocity towards the inlet, but a decrease in that towards the outlet. A significant rise in the upward velocity (in the outer flow region) towards both the keys was observed experimentally and numerically. Both the approaches also indicated a significant increase in the lateral velocity near the inlet, especially in the inner flow region. CFD simulations clearly showed decelerating and accelerating flow zones in front of the outlet and inlet keys, respectively, and also revealed an accelerating flow over the inlet. However, the velocity profile inside the inlet key could not be measured experimentally, possibly due to flow unsteadiness, high turbulence and flow separation, and it demands further research. The CFD results generally underestimated the velocity values for the measured 0.1 m depth of flow and the mean absolute error values for the resultant velocity were 18.32% and 15.52% for the two discharges, respectively. The rise in the approaching flow velocity components towards the inlet and the sloping key enhance the opportunity of sediment passage over a PKW in comparison to other weirs. Extending this work, the study on the flow field near two-cycles and three-cycles PKW models is undergoing.</p>

MODERN PROBLEMS OF CHANGES MANAGEMENT IN HIGHER EDUCATION IN RUSSIA

The accelerating flow of changes in all spheres of society puts humanity in the face of the problem of determining its place and role in this flow. Should we follow the limits set by the parameters and conditions of the flow, or try to control it? The answer to this by no means idle question should be given first of all by university science – that part of science that produces not only new knowledge, but also the main resource for their practical implementation – competent people. Accordingly, universities should also be in the flow of changes and determine the goals, objectives and content of ongoing changes not only for society, but also for themselves. The basic contours of this personal identity process are already beginning to become clear. There is a consensus that the transformation of higher education should be managed. But many questions, both theoretical and practical, remain open. And the main among them is question of how and by whom this process should be managed. The article deals with the features of the current stage of development of management relations in higher education in Russia. The necessity of transforming university activities is shown. The conditions and approaches to making changes are described. The practical policy of implementing changes is analyzed. Suggestions for its improvement are put forward and justified.

Porosity Manipulation in Bottom-Enclosed Vertical Porous Structure to Improve Natural Convection Cooling Efficacy: A Computational Study

Flow acceleration by imposing flow channelization structures like chimneys and/or solid barriers to improve natural convection cooling in pure fluids, is a well-known technique and a thoroughly investigated topic in thermal engineering. However, accelerating flow through porous media, by using such a passive technique, is challenging due to restriction imposed by the solid matrix to the erection of such structures. This study is a unique investigation into a passive method to accelerate flow in natural convection cooling through a bottom-enclosed porous medium with a vertical heated structure at the center, a configuration that is commonly encountered in industry. The porous domain is divided into distinct zones varying in porosity while retaining the average porosity of the original system, to ensure enough structural stability to the vertical heating element. Employing computational fluid dynamics (CFD) analyses, the study shows that the method has the potential to significantly improve natural convection cooling by accelerating flow in tall porous structures while at the same time improves mechanical stability of such structures.

Impact of nonlinear radiative nanoparticles on an unsteady flow of a Williamson fluid toward a permeable convectively heated shrinking sheet

PurposeThe study aims to numerically examine the impact of nanoparticles on an unsteady flow of a Williamson fluid past a permeable convectively heated shrinking sheet.Design/methodology/approachIn sort of the solution of the governing differential equations, suitable transformation variables are used to get the system of ODEs. The converted equations are then numerically solved via the shooting technique.FindingsThe impacts of such parameters on the velocity profile, temperature distribution and the concentration of nanoparticles are examined through graphs and tables. The results point out that multiple solutions are achieved for certain values of the suction parameter and for decelerating flow, while for accelerating flow, the solution is unique. Further, the non-Newtonian parameter reduces the fluid velocity and boosts the temperature distribution and concentration of nanoparticles in the first solution, while the reverse drift is noticed in the second solution.Practical implicationsThe current results may be used in many applications such as biomedicine, industrial, electronics and solar energy.Originality/valueThe authors think that the current results are new and significant, which are used in many applications such as biomedicine, industrial, electronics and solar energy. The results have not been considered elsewhere.

A PIV-based method to measure spatial gradients in bedload transport over a dune

Traditional sediment transport equations calculate sediment flux from bed shear stress and the equations predict that transport increases nonlinearly with an increase in flow velocity. In a dune field, the dune geometry affects the flow velocity causing accelerating flow over the dune crest and de- and reattachment of the flow downstream of the dune crest. Sediment flux predicted from the reach-averaged bed shear stress gives fairly good results for dune fields, though their simplification is discordant for the complexity of the processes involved. Measurements of the displacement of sand particles over the dune bed were derived from highfrequency image capturing. The two main methods to measure particle velocities from images are particle tracking velocimetry (PTV) and particle image velocimetry (PIV). We compare individual particle tracking with a PIV-based correlation method. The PIV-based method promises to be a more efficient and effective approach to track particle motion. It is more suitable for the conditions of high bedload transport, as present in our experiments. The PIV-based method is based on using images of difference (IoD) and is fully automated and identifies spatial gradients at a support scale in the order of centimetres. Findings align with our general knowledge of accelerating flow over the dune crest. The mean streamwise particle velocity and activity over a dune stoss slope increase. At the scale of 0.026 m the observed particle velocity variability can be explained in the context of general onset and cessation of sediment transport, the effect of the reattachment zone and observed sweep/burst events. By decreasing the streamwise distance between cross-sections, the variations in mean particle velocity induced by superimposed bed defects are distinguished as well. The maximum particle velocity and activity occurred at the same location and consequently the location of the maximum transport over the dune crest was identified. The measurements bridge the gap between individual particle motion studies and (non-local) sediment transport flux measurements.