Generic Upscaling Methodology of a Floating Offshore Wind Turbine

This study presents a generic method to upscale a semi-submersible substructure and tower-nacelle-blade for a floating offshore wind turbine from 5 MW to 15 MW and beyond. The effects of upscaling the column radius and/or distance of the floating base are investigated, and a comparison is made with a 15 MW reference design. It is found that scaling column radius increases the mass of the platform and the heave natural period, while scaling column distance raises the center of gravity and metacentric height of the floating system and slightly decreases the heave natural period. The 15 MW reference design addresses these issues through design changes that increase the ballast mass to lower the center of gravity, and increase the added mass to raise the heave natural period. Finally, a method for estimating the scaling of platform parameters with different assumptions is proposed.

Application of genetic algorithms in optimization of SFR nuclear reactor design

This work presents a demonstrational application of genetic algorithms (GAs) to solve sample optimization problems in the generation IV nuclear reactor core design. The new software was developed implementing novel GAs, and it was applied to show their capabilities by presenting an example solution of two selected problems to check whether GAs can be used successfully in reactor engineering as an optimization tool. The 3600 MWth oxide core, which was based on the OECD/NEA sodium-cooled fast reactor (SFR) benchmark, was used a reference design [1]. The first problem was the optimization of the fuel isotopic inventory in terms of minimizing the volume share of long-lived actinides, while maximizing the effective neutron multiplication factor. The second task was the optimization of the boron shield distribution around the reactor core to minimize the sodium void reactivity effect (SVRE). Neutron transport and fuel depletion simulations were performed using Monte Carlo neutron transport code SERPENT2. The simulation resulted in an optimized fuel mixture composition for the selected parameters, which demonstrates the functionality of the algorithm. The results show the efficiency and universality of GAs in multidimensional optimization problems in nuclear engineering.

Detecting Multidimensional Pareto Fronts during the Optimization of a Return Channel within a Centrifugal Compressor

This paper explains the advantages of using big-data methods for evaluating numerical optimization. The investigation focuses on the performance potential of three-dimensional return channel vanes under realistic manufacturing constraints. Based on an analysis of an optimization database, the paper presents a systematic approach for analysis and setting up design guidelines. To this end, a validated numerical setup was developed on the basis of experiments, followed by a numerical optimization using genetic algorithms and artificial neural networks. The optimization database was analyzed with a dimension reduction method called t-SNE. This method enabled linking geometric design features with physical correlations and, finally, with the objective functions of the optimization. With the help of the detected correlations within the database, it has been possible to work out a method for deciding on the selection of a design on the Pareto front and to draw new relevant conclusions. The systematic use of big-data methods proposed enables a more penetrating insight to be gained into numerical optimization, which is more general and relevant than those gained by simply comparing a single optimized design with a reference design. An analysis of the Pareto front reveals that 0.6% efficiency can be exchanged for 20% more homogeneous outflow. The design of the vane profiles at hub and shroud works best using a front-loaded design for the hub side and an aft-loaded design for the shroud side, since this minimizes the blade-to-blade pressure gradient and, in turn, the secondary flow.

Changing the technical characteristics of conveyors with a suspended belt in case of failures in the power supply system of drive suspensions

The results of the research presented in the article relate to a fundamentally new type of continuous transport machines-conveyors with a suspended load-carrying belt and a distributed drive. The main advantages of which are due to the features of the kinematic scheme, in which the load-bearing conveyor belt is held by the sides by means of roller suspensions on rolling guides closed along the route and does not interact with its base with supporting supports, and the drive is implemented according to the distributed scheme by the equipment of individual suspensions with individual motor-gear drives. A feature of such a kinematic scheme is the nature of the failures associated with the operation of highly loaded drive suspensions, the influence of which affects the main technical characteristics of the conveyor with a sufficiently increased number. The paper presents a mathematical model designed to calculate the dynamic characteristics of a conveyor with a suspended belt and a distributed drive when the types of failures characteristic of this conveyor design occur, associated with a break in the supply electrical circuit of the motor-gear drive of the suspensions. Based on the developed mathematical model for the reference design of a conveyor with a suspended belt and a distributed drive, a series of numerical calculations of dynamic characteristics in the event of failures of drive suspensions is performed. The obtained results allowed us to establish that with a reduction in the number of groups of consistently failed drive suspensions located with an equal step along the route, the technical characteristics of the conveyor deteriorate: the speed of movement of the load-bearing belt and the total power of the drives are reduced, and the longitudinal tensile stresses in the belt are increased. With an increase in the number of consistently failed drive suspensions within one group, the power and speed of the conveyor decrease non-linearly, and the longitudinal stresses in the conveyor belt increase linearly. In general, the results of calculations of the technical characteristics of the reference idealized design demonstrated the possibility of the conveyor operation in case of failure of 90% of the drive suspensions. The actual performance indicators are determined by the technical characteristics of the used gear motor drives.

Virtualization of Programmable Forwarding Planes with P4VBox

Networking virtualization has shown to enable faster service provioning and server as a main driver of innovation, from Software-Defined Networking (SDN) to Network Function Virtualization (NFV) and Local Area Networks (VLAN). Recent investigations began assessing the feasibility of virtualization in Programmable Data Planes (PDP). Despite the progress achieved, much work remains to assess their effectiveness for programmable virtual switches. In a prior work, we introduced P4VBox, an architecture for virtualization of programmable switches written using the P4 language. P4VBox provides the execution of multiple P4 based switch instances running in parallel, with the ability of hot-swapping through full and partial reconfiguration. In this work, we build upon P4VBox to provide novel insights, substantiated by experimental evaluation on a real-world testbed, on the evaluation of the real power of switch virtualization in a NetFPGASUME board, deploying three use cases. We measured resource utilization and performance to observe the behavior of P4VBox when handling large flows. Our results demonstrate that P4VBox incurs a small overhead compared with the canonical NetFPGA reference design. Yet, it increases orders of magnitude considering the existing works.

Integrating Geometric Data into Topology Optimization via Neural Style Transfer

This research proposes a novel topology optimization method using neural style transfer to simultaneously optimize both structural performance for a given loading condition and geometric similarity for a reference design. For the neural style transfer, the convolutional layers of a pre-trained neural network extract and quantify characteristic features from the reference and input designs for optimization. The optimization analysis is evaluated as a single weighted objective function with the ability for the user to control the influence of the neural style transfer with the structural performance. As seen in architecture and consumer-facing products, the visual appeal of a design contributes to its overall value along with mechanical performance metrics. Using this method, a designer allows the tool to find the ideal compromise of these metrics. Three case studies are included to demonstrate the capabilities of this method with various loading conditions and reference designs. The structural performances of the novel designs are within 10% of the baseline without geometric reference, and the designs incorporate features in the given reference such as member size or meshed features. The performance of the proposed optimizer is compared against other optimizers without the geometric similarity constraint.

Alternative Absorber Materials for Control Rods in ALFRED

The next-generation reactors require improved safety performance and longer cycle length, which initiate the research on alternative absorber materials. In this context, potential absorber materials including borides (B4C, HfB2, and ZrB2), rare earth oxides (Eu2O3, Gd2O3, Sm2O3, and Dy2TiO5), metals/alloys (Hf and AIC), and metal hydride (HfHx) were compared in a large sodium fast reactor. The design of control rods for Generation-IV fast reactors strongly depends on the core characteristics. In this paper, some alternative absorbers are assessed in a lead fast reactor ALFRED using depletion capability in the Monte-Carlo particle transport code OpenMC. Results show that the ALFRED reference control rod design with B4C largely satisfies the shutdown and operation requirements. 60% 10B enriched HfB2 and HfH1.18 can replace the operation part of the reference design. In the future, the safe operating life of B4C and HfB2 should be assessed taking into account the irradiation-induced swelling, temperature margin, and gas release. HfH1.18 has a limited and local influence on the core power distribution. Eu2O3 has little loss on the absorption ability after 5 cycle irradiation. This oxide absorber satisfies the shutdown function even with only half control rod insertion, while its critical insertion depth at beginning of the cycle should be increased to realize reactivity compensation function.

The Prediction of the Performance of a Twisted Rudder

A new design approach using the concept of a twisted rudder to improve rudder performances has been proposed in the current paper. A correction step was introduced to obtain the accurate inflow angles induced by the propeller. Three twisted rudders were designed with different twist angle distributions and were tested both numerically and experimentally to estimate their hydrodynamic characteristics at a relatively high ship speed. The improvement in the twisted rudders compared to a reference flat rudder was assessed in terms of total cavitation amount, drag and lift forces, and moment for each twin rudder. The total amount of surface cavitation on the final optimized twin twisted rudder at a reference design rudder angle decreased by 43% and 34.4% in the experiment and numerical prediction, respectively. The total drag force slightly increased at zero rudder angle than that for the twin flat rudder but decreased at rudder angles higher than 4° and 6° in the experiment and numerical simulation, respectively. In the experimental measurements, the final designed twin twisted rudder gained a 5.5% increase in the total lift force and a 37% decrease in the maximum rudder moment. Regarding these two performances, the numerical results corresponded to an increase of 3% and a decrease of 66.5%, respectively. In final, the present numerical and experimental results of the estimation of the twisted rudder performances showed a good agreement with each other.