• Energy Research

In this paper, an enriched radial point interpolation method (e‐RPIM) is developed for the determination of crack tip fields. The conventional RBF interpolation is novelly augmented by the suitable trigonometric basis functions to reflect the properties of stresses for the crack tip fields. The performance of the enriched meshfree RBF shape functions is firstly investigated using the surface fitting. The surface fitting results have proven that, comparing with the conventional RBF, the enriched RBF interpolation has: 1) a similar accuracy to fit a polynomial surface; and 2) a much better accuracy to fit a trigonometric surface then the conventional RBF interpolation. It has proven that the enriched RBF shape function will not only possess all advantages of conventional RBF interpolation, but also can accurately reflect the properties of stresses for the crack tip fields. The system of equations for the crack analysis is then derived based on the enriched RBF shape function and the meshfree weak‐form. Crack problems are simulated using this newly developed e‐RPIM method. It has been demonstrated that the present e‐RPIM is very accurate and stable, and it has very good potential to develop a practical simulation tool for fracture mechanics problems.

The study of wind farm layout optimization considering the decisions of land owners has rarely been reported in literature. In this paper, the common situation of complex land divisions (e.g. unequally-spaced plots) is addressed for the first time. A new constraint handling and fitness evaluation technique is developed to address the more complex wind farm boundaries and integrated into two common wind farm optimization approaches: the grid based method and the unrestricted coordinate method. Enable by the new technique, a numerical optimization study is conducted with the goal of evaluating the impact of the participation of land owners on the economic performance of the wind farm. In particular, two scenarios are considered: 1) the varying land plot scenario, where the land plot availability is included in the decision variables of the optimization, and 2) the sequential land plot scenario, where the land plot availability is fixed prior to optimization. The study reveals that the unrestricted coordinate method under the sequential land plot scenario yields the best optimization results, with the smallest cost of energy and the largest wind farm efficiency.

Natural convection within an attic space under diurnal temperature condition on the sloping wall and a heat source located on the insulated bottom wall have been studied to show the basic flow features in the attic space over diurnal cycles. The finite volume numerical method has been employed to solve the governing equations. Effect of Rayleigh number (Ra), attic aspect ratio, heater location and its size are discussed on the transient flow pattern and heat transfer phenomenon after grid independency and time interval selection tests with a fixed prandtl number of 0.72 (air). Results are presented as a form of isotherms and streamlines. Also, heat transfer is presented as a form of Nusselt number. The numerical experiments show that, the flow in the attic space is stratified during the daytime heating stage; whereas the flow becomes unstable at the night-time cooling stage.

Numerical simulations are carried out to study the unsteady air flow and heat transfer in a partitioned triangular cavity of differentially heated from inclined walls and heat source placed at the bottom wall. The finite volume numerical method has been employed to solve the governing equations. The grid sensitivity test has been carried out and obtained results have been validated against experimental results. The dependency of several parameters on fluid flow and heat transfer is studied including Rayleigh number from 103 to 106, heater size from 0.2 to 0.6, heater position from 0.3 to 0.7 and aspect ratio from 0.2 to 1.0 with a fixed Prandtl number of 0.72 (air). A conductive partition of infinite conductivity is placed at the middle of the enclosure, which means that only heat can freely transfer between two fluid zones through the partition. Results are presented as a form of isotherms and streamlines. Also, heat transfer is presented as a form of Nusselt number. Both transient and steady states of solutions are presented in this study.

Manipulation of interlayer interaction in nanoscale can effectively modulate the electronic and optical properties of layered materials, which can find photovoltaic applications when it is coupled with the in-plane or out-of-plan polarization. Here, based on in-plane ferroelectric 2D GeSe/SnS heterobilayer, we found that the optoelectronic properties can be well modulated by the interlayer stacking patterns from the density functional theory (DFT) simulations, where the ferroelectric ground states, electronic bandgaps and optical adsorptions are highly dependent on the relative interlayer configurations. Comparing with the homogeneous counterparts, the modulations are more significant due to the presence of vertical polarization. As a result, the power conversion efficiency of the heterobilayer increases from 13.4% to 22.8% by interlayer sliding. These findings provide feasible strategies to optimize the photovoltaic performance of 2D nanomaterial-based solar cells.

For wind farm optimizations with lands belonging to different owners, the traditional penalty method is highly dependent on the type of wind farm land division. The application of the traditional method can be cumbersome if the divisions are complex. To overcome this disadvantage, a new method is proposed in this paper for the first time. Unlike the penalty method which requires the addition of penalizing term when evaluating the fitness function, it is achieved through repairing the infeasible solutions before fitness evaluation. To assess the effectiveness of the proposed method on the optimization of wind farm, the optimizing results of different methods are compared for three different types of wind farm division. Different wind scenarios are also incorporated during optimization which includes (i) constant wind speed and wind direction; (ii) various wind speed and wind direction, and; (iii) the more realisticWeibull distribution. Results show that the performance of the new method varies for different land plots in the tested cases. Nevertheless, it is found that optimum or at least close to optimum results can be obtained with sequential land plot study using the new method for all cases. It is concluded that satisfactory results can be achieved using the proposed method. In addition, it has the advantage of flexibility in managing the wind farm design, which not only frees users to define the penalty parameter but without limitations on the wind farm division.

Metal foams have gained popularity in the renewable energy industry due to their superior thermo-physical properties. In the present study, a coupled finite volume and discrete element numerical method is used to numerically investigate the mechanisms that govern particle-laden gas flows and particulate fouling in idealized metal foam air-cooled heat exchangers. This paper provides a systematic analysis of the foulant distribution and the pressure drop due to the metal foam structure and the presence of fouling. The idealized Weaire-Phelan metal foam geometry serves as a good approximation to a real metal foam geometry. The pressure drop and deposition fraction follows a linear relation for sandstone cases, whereas for the sawdust cases, the pressure drop is sensibly invariant with time although a noticeable increase in deposition fraction with time is realized. The foulant residence time in addition to the correlations between pressure drop, deposition fraction, and inlet velocity can be used to optimize metal foam heat exchanger designs. Optimum heat exchanger performance is achieved by keeping the same fiber thickness of 0.17 mm at a high porosity at 97.87%. An increase in fluid carrier velocity promotes particle transport by means of particle interception thereby reducing the deposition fraction irrespective of foam geometry.

Highlights • An optimized control strategy approach and different hub height turbines are studied. • Means of handling irregular boundaries and wind speed variations over non-flat terrain are developed. • Optimized control strategy yields 9 kW more power per turbine than self-optimum control strategy. • Optimized control strategy reduces cost of energy by 0.08 million dollars per megawatt. • Different hub height turbines are more able to alleviate wake interactions than constant hub height.

Road safety barriers are used to minimise the severity of road accidents and protect lives and property. There are several types of barrier in use today. This paper reports the initial phase of research carried out to study the impact response of portable water-filled barrier (PWFB) which has the potential to absorb impact energy and hence provide crash mitigation under low to moderate speeds. Current research on the impact and energy absorption capacity of water-filled road safety barriers is limited due to the complexity of fluid-structure interaction under dynamic impact. In this paper, a novel fluid-structure interaction method is developed based on the combination of Smooth Particle Hydrodynamics (SPH) and Finite Element Method (FEM). The sloshing phenomenon of water inside a PWFB is investigated to explore the energy absorption capacity of water under dynamic impact. It was found that water plays an important role in energy absorption. The coupling analysis developed in this paper will provide a platform to further the research in optimising the behaviour of the PWFB. The effect of the amount of water on its energy absorption capacity is investigated and the results have practical applications in the design of PWFBs.