Fluid-Structure Interaction of NREL 5-MW Wind Turbine

Wind energy is considered one of the major sources of renewable energy. Nowadays, wind turbine blades could exceed 100 m to maximize the generated power and minimize produced energy cost. Due to the enormous size of the wind turbines, the blades are subjected to failure by aerodynamics loads or instability issues. Also, the gravitational and centrifugal loads affect the wind turbine design because of the huge mass of the blades. Accordingly, wind turbine simulation became efficient in blade design to reduce the cost of its manufacturing. The fluid-structure interaction (FSI) is considered an effective way to study the turbine\u27s behavior when the air and the blade are simulated as one system. In the present study, NREL 5 MW wind turbine with a blade length of 61.5m long is selected as a reference turbine to apply the FSI. The FSI is performed using three commercial software. ANSYS Fluent is used for the Computational Fluid Dynamics (CFD) model. The Finite Element (FE) model is simulated by Abaqus. In order to link both models together and transfer the data between them, MPCCI software is used. The blade is subjected to flap-wise deflection, edge-wise deflection, and torsion. So, a 2-way coupling simulation is implemented to optimize the blade deformation to protect it from hitting the tower, mitigate the effect of cyclic loading, and prevent the blade stall. This study introduced two passive optimization methods: material Bend Twist Coupling (BTC) and blade root fixation. One of the achievements of this study is that it is considered the first FSI research implemented at the AUC. Also, running the FSI model with three different codes and linking between them was another challenge. Moreover, it is concluded from this research that the 2-way coupling gives more accurate results than the 1-way coupling, although it is complicated. Although the centrifugal force reduces the flap-wise deflection, it significantly impacts the blade twist angle. The used material BTC optimization method improved the blade torsion stiffness while the root fixation improved the longitudinal stiffness. The improvement in the blade protects it from fatigue loading and stall by reducing the peak-to-peak amplitude and twisting the blade to feather

Minimisation du Content par une méthode d'active set pour les équations d'équilibrage hydraulique conduites par la pression

International audienceA new content-based, box-constrained, active-set projected Newton method is presented that solves for the heads, the pipe flows, and the nodal outflows of a water distribution system in which nodal outflows are pressure dependent. The new method is attractive because, by comparison with the previously published weighted least-squares energy and mass residuals (EMR) damped Newton method, (1) it typically takes fewer iterations, (2) it does not require damping, (3) it takes less wall-clock time, (4) it does not require the addition of any virtual elements, and (5) it is algorithmically easier to deal with. Various pressure-outflow relationships (PORs), which model nodal outflows, were considered and two new PORs are presented. The new method is shown, by application to eight previously published case study networks with up to about 20,000 pipes and 18,000 nodes, to be up to five times faster than the EMR method and to take between 34% and 70% fewer iterations than the EMR method

Closure to "Jacobian matrix for solving water distribution system equations with the Darcy-Weisbach head-loss model" by Angus Simpson and Sylvan Elhay

Angus R. Simpson and Sylvan Elha

A New Technique for Multidimensional Signal Compression

The problem of efficiently compressing a large number, L, of N dimensional signal vectors is considered. The approach suggested here achieves efficiencies over current pre-processing and Karhunen-Loeve techniques when both L and N are large

Formulating the water distribution system equations in terms of head and velocity

The set of equations for solving for pressures and flows in water distribution systems are non‐linear due to the head loss‐velocity relationship for each of the pipes. The solution of these non‐linear equations for the heads and flows is usually based on the Todini and Pilati method. The method is an elegant way of formulating the equations. A Newton solution method is used to solve the equations whereby the special structure of the Jacobian is exploited to minimize the computations and this leads to an extremely fast algorithm. Each iteration firstly solves for the heads and then solves for the flows. In the EPANET implementation of the Todini and Pilati algorithm an initial guess of the flows is based on an assumed velocity of 1.0 fps (0.305 m/s) in each pipe in the network. Each flow is then determined from the continuity equation by multiplying the assumed velocity by the area. Usually velocities in pipes are in the range of 0.5 to 1.5 m/s (and perhaps sometimes higher up to 3 or 4 m/s). Thus the velocities to be solved for are all of the same order of magnitude. In contrast, the range of discharges may be quite large in a system — ranging from below 10 L/s up to above 700 L/s — thus possibly three orders of magnitude of difference. As an alternative to the usual formulation of the Todini and Pilati method in terms of flows and heads, this paper recasts the Todini and Pilati formulation in terms of heads and velocities to attempt to improve the convergence properties. Results are compared for the two formulations for a range of networks from 553 to 10,354 pipes. Convergence criteria for stopping the iterative solution process are discussed. The impact of the initial guess of the velocities in each of the pipes in the network on the convergence behavior is also investigated. Statistics on mean flows and velocities in the network and the minimum and maximum velocities for each of the example networks are given and finally operation counts are also provided for these networks.Angus R. Simpson and Sylvan Elha

Closure to "Dealing with Zero Flows in Solving the Nonlinear Equations for Water Distribution Systems" by Sylvan Elhay and Angus R. Simpson

Sylvan Elhay and Angus R. Simpso

The Darcy-Weisbach Jacobian and avoiding zero flow failures in the global gradient algorithm for the water network equations

This paper considers two issues related to iteratively solving the non-linear equations governing the flows and heads in a water distribution system network. The first concerns the use of the correct Jacobian for the Global Gradient Algorithm (GGA) when the Darcy-Weisbach head loss model is used. The second relates to dealing with zero flows in the iterative solution process. A regularization procedure for the GGA with the Hazen{Williams model is demonstrated on an example network which has zero flows but for which the (full) Jacobian is invertible.Sylvan Elhay and Angus R. Simpso

Computing the Hessenberg matrix associated with a self-similar measure

We introduce in this paper a method to calculate the Hessenberg matrix of a sum of measures from the Hessenberg matrices of the component measures. Our method extends the spectral techniques used by G. Mantica to calculate the Jacobi matrix associated with a sum of measures from the Jacobi matrices of each of the measures. We apply this method to approximate the Hessenberg matrix associated with a self-similar measure and compare it with the result obtained by a former method for self-similar measures which uses a fixed point theorem for moment matrices. Results are given for a series of classical examples of self-similar measures. Finally, we also apply the method introduced in this paper to some examples of sums of (not self-similar) measures obtaining the exact value of the sections of the Hessenberg matrix

Dealing with zero flows in solving the nonlinear equations for water distribution systems

Three issues concerning the iterative solution of the nonlinear equations governing the flows and heads in a water distribution system network are considered. Zero flows cause a computation failure (division by zero) when the Global Gradient Algorithm of Todini and Pilati is used to solve for the steady state of a system in which the head loss is modeled by the Hazen-Williams formula. The proposed regularization technique overcomes this failure as a solution to this first issue. The second issue relates to zero flows in the Darcy-Weisbach formulation. This work explains for the first time why zero flows do not lead to a division by zero where the head loss is modeled by the Darcy-Weisbach formula. In this paper, the authors show how to handle the computation appropriately in the case of laminar flow (the only instance in which zero flows may occur). However, as is shown, a significant loss of accuracy can result if the Jacobian matrix, necessary for the solution process, becomes poorly conditioned, and so it is recommended that the regularization technique be used for the Darcy-Weisbach case also. Only a modest extra computational cost is incurred when the technique is applied. The third issue relates to a new convergence stopping criterion for the iterative process based on the infinity-norm of the vector of nodal head differences between one iteration and the next. This test is recommended because it has a more natural physical interpretation than the relative discharge stopping criterion that is currently used in standard software packages such as EPANET. In addition, it is recommended to check the infinity norms of the residuals once iteration has been stopped. The residuals test ensures that inaccurate solutions are not accepted. © 2011 American Society of Civil Engineers.Sylvan Elhay and Angus R. Simpso

Effect of CuO Nanoparticles on Performance and Emissions Behaviors of CI Engine Fueled with Biodiesel-Diesel Fuel Blends

Recently the world has a very important need for replacement fossil fuel with renewable sources of energy. Greenhouse effect is considered one of bad effects of fossil fuels. In this study diesel fuel will be replaced with blends of diesel and biodiesel produced from waste cooking oil(WCO) is created using a catalytic transesterification reaction (CTR). With the addition of a low concentration of alcohol over the period of an hour at a reaction temperature of 65 °C, (CTR) converts (WCO) to methyl esters. Blends consisting of (40 % diesel, 60 % biodiesel and CuO nano- martial with different concentration) will be prepared for fueling direct injection engine four-stroke. The engine will be run at 1400 rpm with natural aspiration under various loads. Using blends of (pure diesel, B40 [consist of 60 % biodiesel and 40 % diesel], 50b40 [consist of 60 % biodiesel, 40 % diesel and 50 mg CuO],100B40 [consist of 60 % biodiesel, 40 % diesel and 100 mg CuO], 150 [consist of 60 % biodiesel, 40 % diesel and 150 mg CuO] and pure diesel). On engine performance and emissions, the impact of using copper oxide has been studied. The results of the experiment demonstrate that diesel engines can run on various mixtures of fuel, biodiesel, and CuO nano-material under the same operating conditions. The obtained data indicates that a 10% increase in brake thermal efficiency was noted, decrease in exhaust temperature with 11.6 % and decrease in brake specific fuel consumption with 6.66