Instabilities of a sand layer subjected to an upward water flow by a 2D coupled discrete element - Lattice Boltzmann hydromechanical model

This work deals with the numerical simulation of the instabilities occurring in a sand layer subjected to an upward water flow. A coupled Discrete Elements - Lattice Boltzmann hydromechanical model is used for this end. After a brief presentation of the numerical model, simulations of an upward fluid flow through granular deposits are performed for two cases namely under controlled hydraulic gradients and under controlled volumetric flow rates. In the first case i.e. under controlled hydraulic gradient, the simulations show that the quicksand condition is actually reached for a hydraulic gradient very close to the critical hydraulic gradient calculated from the global analysis of classical soil mechanics. The simulations point out moreover that the quicksand phenomenon could be produced locally under slightly lower gradients. In the second case i.e. under controlled volumetric flow rates, the simulations show that there are three levels of flow ; low flow rates that allow infiltration without any destabilization, medium flow rates that cause expansion of the deposit to increase its permeability and high flow rates which may cause the formation continuous tunnel between the upstream and the downstream sides as well as sand boils. It is shown also that under the controlled flow rate condition the hydraulic gradient remains in all cases less than the average critical hydraulic gradient

Genetic algorithm optimized robust nonlinear observer for a wind turbine system based on permanent magnet synchronous generator

© 2022 ISA. Published by Elsevier Ltd. All rights reserved. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1016/j.isatra.2022.02.004This paper presents an optimal control scheme for a Permanent Magnet Synchronous Generator (PMSG) coupled to a wind turbine operating without a position sensor. This sensorless scheme includes two observers: The first observer uses the flux to estimate the speed. However, an increase in the temperature or a degradation of the permanent magnet characteristics will result in a demagnetization of the machine causing a drop in the flux. The second observer is therefore used to estimate these changes in the flux from the speed and guaranties the stability of the system. This structure leads to a better exchange of information between the two observers, eliminates the problem of encoder and compensates for the demagnetization problem. To improve the precision of the speed estimator, the gain of the non-linear observer is optimized using Genetic Algorithm (GA) and the speed is obtained from a modified Phase Locked Loop (PLL) method using an optimized Sliding Mode Controller (SMC). Furthermore, to enhance the convergence speed of this observer scheme and improve the performance of the system a Fast Super Twisting Sliding Mode Control (FSTSMC) is introduced to reinforce the SMC strategy. A series of simulations are presented to show the effectiveness and robustness of proposed observer scheme.Peer reviewe

New Hybrid Sensorless Speed of a Non-Salient Pole PMSG Coupled to Wind turbine Using a Modified Switching Algorithm

©2019 ISA. Published by Elsevier Ltd. All rights reserved. his manuscript is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence (CC BY-NC-ND 4.0). For further details please see: https://creativecommons.org/licenses/by-nc-nd/4.0/The paper focuses on the design of position and speed observers for the rotor of a non-salient pole permanent magnet synchronous generator (NSPPMSG) coupled to a wind turbine. With the random nature of wind speed this observer is required to provide a position and speed estimates over a wide speed range. The proposed hybrid structure combines two observers and a switching algorithm to select the appropriate observer based on a modified weighting coefficients method. The first observer is a higher-order sliding mode observer (HOSMO) based on modified super twisting algorithm (STA) with correction term and operates in the medium and nominal wind speed ranges. The second observer is used in the low speed range and is based on the rotor flux estimation and the control by injecting a direct reference current different to zero. The stability of each observer has been successfully assessed using an appropriate Lyapunov function. The simulation results obtained show the effectiveness and performance of the proposed observer and control scheme.Peer reviewe

Instabilities of a sand layer subjected to an upward water flow by a 2D coupled discrete element - Lattice Boltzmann hydromechanical model

This work deals with the numerical simulation of the instabilities occurring in a sand layer subjected to an upward water flow. A coupled Discrete Elements - Lattice Boltzmann hydromechanical model is used for this end. After a brief presentation of the numerical model, simulations of an upward fluid flow through granular deposits are performed for two cases namely under controlled hydraulic gradients and under controlled volumetric flow rates. In the first case i.e. under controlled hydraulic gradient, the simulations show that the quicksand condition is actually reached for a hydraulic gradient very close to the critical hydraulic gradient calculated from the global analysis of classical soil mechanics. The simulations point out moreover that the quicksand phenomenon could be produced locally under slightly lower gradients. In the second case i.e. under controlled volumetric flow rates, the simulations show that there are three levels of flow ; low flow rates that allow infiltration without any destabilization, medium flow rates that cause expansion of the deposit to increase its permeability and high flow rates which may cause the formation continuous tunnel between the upstream and the downstream sides as well as sand boils. It is shown also that under the controlled flow rate condition the hydraulic gradient remains in all cases less than the average critical hydraulic gradient

Numerical simulation of the quicksand phenomenon by a 3D coupled Discrete Element - Lattice Boltzmann hydromechanical model

International audienceThis paper deals with the numerical simulation of the quicksand phenomenon using a coupled Discrete Elements – Lattice Boltzmann hydromechanical model. After the presentation of the developed numerical model, simulations of ascending fluid flow through granular deposits are performed. The simulations show that the quicksand actually triggers for a hydraulic gradient very close to the critical hydraulic gradient calculated from the global analysis of classical soil mechanics, that is, when the resultant of the applied external pressure balances submerged weight of the deposit. Moreover, they point out that the quicksand phenomenon does not occur only for hydraulic gradients above the critical hydraulic gradient, but also in some cases with slightly lower gradients. In such cases, a more permeable zone is first gradually built at the bottom of the deposit through a grain rearrangement, which increases the hydraulic gradient in the upper zones and triggers the phenomenon

Online Temperature Control System

In this paper, a remote temperature control system has been proposed. The physical system is controlled in real time through the Internet network. For educational purpose, the students use only a web browser to tune and test a PID controller via shared user interface. The PID parameters are calculated using the basic experimental Ziegler—Nichols tuning rules. After hardware and software experiment description, the remote online experiment is tested and the results are given

A 3D DEM-LBM Approach for the Assessement of the Quick Condition for Sands

International audienc

Onset of immersed granular avalanches by DEM-LBM approach

International audienc

Solar PV power driven cold room storage for Saharan rural area

The use of renewable energy sources is usually a reliable alternative in rural areas and developing countries, where the gridline does not exist or is at a great distance. The present work is to study the possibility of feeding the tomatoes preservation cold room storage in the Sahara region driven by solar photovoltaic generator. An energy-efficient design has been achieved by analytical calculation. A PV field calculation approach yielded the following results: for a storage capacity of about 1 ton of tomatoes, the cooling capacity is 2.5 kW. The use of the design unit gave us in terms of electricity requirements 27 kWh/day by the GPV generator at Adrar province. Electrical power demands can be obtained using an alternative solution, which appears in Vapor Compression Cycles driven by PV modules. This technology considered as promoting concept for the south of Algeria investment