CONTROL AND METHODOLOGY OF MODELING HYDROLOGICAL PROCESSES IN THE DESIGN OF HYDRAULIC STRUCTURES IN THE ESTUARIES OF RIVERS

The article presents the methodology of hydrological modeling of water flows for constructing flow plans in the design of hydraulic structures. On the basis of these calculations, both the specific costs of bottom and suspended sediments in each flow stream and the deformation of the riverbed at various points in time can be determined. The results of experiments with spatial models of river sections are considered. The developed technique makes it possible to calculate the deformation of the bottom and shores and form a flow organization scheme, which, due to an increase in velocities in some section of the channel, ensures sediment transport to more remote areas of the seashore, up to the open sea.

Vane induced two phase flow mixing

Micromixers are used for mixing of multiphase fluids in microchannels. Passive micromixers help in mixing of fluids by having a designed periphery in their structure. In the current study, a Y micro-channel section of 25 mm length with an inlet diameter of 2 mm is considered. Vane shaped micromixers are placed inside the channel to mix fluids of two different concentrations. The vanes are positioned at specific places inside the channel to enhance mixing in the stratified flow stream. The presence of vanes during the flow induces mixing of the stratified fluids without requiring additional components. The study is carried out using COMSOL Multiphysics. The mixing index increases with increase in the number of vanes and no considerable change in velocity is observed downstream of the last vane. Further, when the thickness of the vane is increased, it is found that the mixing index also increases.

Experimental Study of the Sidewall Effect on Three Dimensional Turbulent Wall Jet

An experimental study on the effect of sidewalls on the flow characteristics of a three-dimensional turbulent square wall jet is carried out at a Reynolds number of 25,000. The sidewalls are defined as the two parallel plates along the vertical jet centerline. Four different sizes of sidewall enclosure (here after referred to as SWE) are placed at the lateral positions (z) of ±3.5h, ±4h, ±4.5h and ±5h from the vertical jet centerline plane, where h is the height of square jet. The mean characteristics of fluid flow in wall normal (y) and lateral (z) directions at different downstream locations (x/h = 0.2 - 45) are measured using a hotwire anemometer. The velocity measurements are also performed in the z ? y lateral plane at four downstream locations (x/h = 30, 35, 40 and 45). Results indicate that the mean velocity profile in lateral and wall normal directions behaves differently depending on the size of SWEs. The decay rate of mean velocity increases with decrease in size of SWEs after the downstream location (x/h ≥ 20). The decay rate of the maximum mean velocity increases about 5% in 140mm SWE as compared to 200mm SWE. It is noted that spread of the jet in wall normal and lateral directions increases with decrease in size of SWEs after the attachment of the flow stream on the sidewalls. In the present case, the smaller size of SWE (140mm SWE) has 14.3% and 26.2% higher spread rate as compared to larger size of SWE (200mm SWE) in wall-normal and lateral directions, respectively. It is also seen that the self similar profile gets delayed in wall normal direction as compared to lateral direction for all the cases. The wall normal self-similar profile is obtained early with increase in the size of SWEs and it is obtained at x/h = 30, 27, 24 and 20 for 140mm ,160mm,180mm and 200mm SWEs respectively. The flow stream seems to climb the sidewall and this tendency increases with increase in size of SWEs.

Inlet air and fuel flow pressure fluctuation effect on supersonic combustion

Purpose The purpose of this paper is to analyze the effect of pressure fluctuations on the combustion efficiency of the hydrogen fuel injected into the supersonic oxidizing cross flow. The pressure fluctuations are imposed on inlet air flow and also on the fuel flow stream. Two different situations are considered: the combustion chamber once without and again with the inlet standing oblique shock wave. Design/methodology/approach The pressure fluctuations are imposed on inlet air flow and also on the fuel flow stream. Two different situations are considered: the combustion chamber once without and again with the inlet standing oblique shock wave. The unsteady turbulent reacting flow solver is developed to simulate the supersonic flow field in the combustion chamber with detail chemical kinetics, to predict the time-variation of the combustion efficiency due to the imposed pressure fluctuations. Findings The results show that the response of the reacting flow field depends on both the frequency of fluctuations and the existence of the inlet shock wave. In addition, the inlet standing shock wave has some attenuating role, but the reacting flow shows an amplifying role on imposed oscillations which is also augmented by imposing anti-phase fluctuations on both inlet and fuel flow streams. Originality/value This study is performed to analyze the instabilities in the supersonic combustion which has not been considered before in this manner.

Torque Control of a Laboratory Scale Variable Speed Hydrokinetic Tidal Turbine: CFD Simulation and Validation

Hydrokinetic tidal turbines are a promising alternative for the generation of clean electrical energy. They are still far behind, with respect to their technological development, in comparison to offshore wind turbines, which are currently in the stage of commercial energy production. Thus, more studies and analyses of the behaviour of tidal devices and their interaction with the surrounding ocean space are required. How this interaction is interrelated to the power production system is also necessary to be further examined. In this paper, the development of a whole system, fully-coupled model of a laboratory-scale hydrokinetic tidal turbine, along with its interactions with the ocean environment and its electrical control system is described. The model was developed in fastFlume (SOWFA, NREL) coupled with an external torque control system. The control system is developed from the optimal torque speed curve based Maximum Power Point Tracking (MPPT) algorithm. The optimal torque speed curve of the turbine used in the model was obtained from experimental work in a test tank. The hydrokinetic tidal turbine and the control system models were implemented independently. They were coupled in order to reach an energy balance between the surrounding flow, the tidal turbine, and the control system. Three flow stream velocities were imposed in the inlet of the model domain, starting the rotor from zero rotational speed. After the optimal rotational speed is attained, the electrical power generated and the loads experienced by the turbine rotor were studied. In the simulations, the tidal device is controlled to keep the optimal power production for any flow stream velocity. The results of the modelling work were compared with experimental measurements taken from 1:15th scaled testing of a fully-instrumented and controllable tidal device at the Flowave Ocean Energy Research Facility, The University of Edinburgh, a combined wave and current test facility. The results show time series of turbine and generator variables like mechanical and electrical torque and power, as well as thrust and the optimal rotational speed for each of the tested cases. The validation shows good agreement between the numerical and experimental results which encourages futures studies using the coupled model, including the turbine working in more complex flow conditions and controlled by more complex control schemes.

Comparative Analysis of Shell and Tube Type Heat Exchanger Based on Bell Delaware, Flow Stream and Numerical Methods

An optimized heat exchanger design is always a challenge to designers. This study presents a simplified simulation study on thermal-hydraulic of a small heat exchanger. Both the heat transfer coefficient and pressure drop are simulated for a nine tube shell and tube heat exchanger. A detailed mesh sensitivity analysis is performed to arrive at numerically converged solution. The results of the study are compared with Bell Delaware (BD) and Flow Stream (FS) analytical methods. Results obtained using all three methods show similar trends. Heat transfer coefficient determined using Bell Delaware method is found to be in good agreement with that of ANSYS CFX, whereas pressure drop calculated using Flow stream method is within small percentage difference with CFX results. Overall, the simulation results are verified by the results obtained using analytical methods.