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Longyan Wang
Institute of Fluid Engineering Equipment, JITRI, Jiangsu University, Zhenjiang 212013, China

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Journal article
Published: 09 February 2021 in Mathematics
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Pump-jet propulsion, a new propulsion technology, is primarily designed for underwater vehicles. Because of its concealment and excellent performance, it has been widely used, but due to its confidentiality and complexity, few studies have been published. To explore the relevant design theory of pump-jet propulsion with the aim of increasing its performance, in this study, we applied the direct and inverse design methods to construct a three-dimensional pump-jet model. The direct design method was carried out by comparing the lifting and lifting-line design methods, followed by further geometric optimization of the better model. In a numerical study using computational fluid dynamics (CFD) simulations, the Reynolds Averaged Naviere-Stokes (RANS) equations with SST k-ω turbulence model were solved in a cylindrical computational domain around the pump-jet propulsion device. A numerical investigation of the E779A propeller was carried out beforehand, using different advance ratios, in order to validate the accuracy of the numerical simulation method. The results show that for the direct method, although the model designed using the lifting-line method produced a greater thrust and the pump-jet designed using the lifting method was more efficient and stable, which is more suitable for small and medium underwater vehicles. When considering the inverse design method, the pump-jet propeller obviously accelerated the fluid, and the speed was obviously greater than that designed using the direct design method, while the turbulent kinetic energy in the flow field was higher, as well as the energy loss. Therefore, for small- and medium-sized underwater vehicles, if the priorities are high thrust and high efficiency, the inverse design method is the best option, whereas if stability and lower energy loss are preferred, the direct design method should be adopted.

ACS Style

Yunkai Zhou; Longyan Wang; Jianping Yuan; Wei Luo; Yanxia Fu; Yang Chen; Zilu Wang; Jian Xu; Rong Lu. Comparative Investigation on Hydrodynamic Performance of Pump-Jet Propulsion Designed by Direct and Inverse Design Methods. Mathematics 2021, 9, 343 .

AMA Style

Yunkai Zhou, Longyan Wang, Jianping Yuan, Wei Luo, Yanxia Fu, Yang Chen, Zilu Wang, Jian Xu, Rong Lu. Comparative Investigation on Hydrodynamic Performance of Pump-Jet Propulsion Designed by Direct and Inverse Design Methods. Mathematics. 2021; 9 (4):343.

Chicago/Turabian Style

Yunkai Zhou; Longyan Wang; Jianping Yuan; Wei Luo; Yanxia Fu; Yang Chen; Zilu Wang; Jian Xu; Rong Lu. 2021. "Comparative Investigation on Hydrodynamic Performance of Pump-Jet Propulsion Designed by Direct and Inverse Design Methods." Mathematics 9, no. 4: 343.

Journal article
Published: 05 October 2020 in Mathematics
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Rotor-stator interaction (RSI) in the centrifugal pump-as-turbine (PAT) is a significant source of high amplitude of the pressure pulsation and the flow-induced vibration, which is detrimental to the stable operation of PAT. It is therefore imperative to analyze the rotor-stator interaction, which can subsequently be used as a guideline for reducing the output of PAT noise, vibration and cavitation. In addition, it is important for a PAT to have a wide operating range preferably at maximum efficiency. In order to broaden the operating range, this work proposes a multi-condition optimization scheme based on numerical simulations to improve the performance of a centrifugal PAT. In this paper, the optimization of PAT impeller design variables (b2, β1, β2 and z) was investigated to shed light upon its influence on the output efficiency and its internal flow characteristics. Thus, the aim of the study is to examine the unsteady pressure pulsation distributions within the PAT flow zones as a result of the impeller geometric optimization. The numerical results of the baseline model are validated by the experimental test for numerical accuracy of the PAT. The optimized efficiencies based on three operating conditions (1.0Qd, 1.2Qd, and 1.4Qd) were maximally increased by 13.1%, 8.67% and 10.62%, respectively. The numerical results show that for the distribution of PAT pressure pulsations, the RSI is the main controlling factor where the dominant frequencies were the blade passing frequency (BPF) and its harmonics. In addition, among the three selected optimum cases, the optimized case C model exhibited the highest level of pressure pulsation amplitudes, while optimized case B reported the lowest level of pressure pulsation.

ACS Style

Jian Xu; Longyan Wang; Stephen Ntiri Asomani; Wei Luo; Rong Lu. Improvement of Internal Flow Performance of a Centrifugal Pump-As-Turbine (PAT) by Impeller Geometric Optimization. Mathematics 2020, 8, 1714 .

AMA Style

Jian Xu, Longyan Wang, Stephen Ntiri Asomani, Wei Luo, Rong Lu. Improvement of Internal Flow Performance of a Centrifugal Pump-As-Turbine (PAT) by Impeller Geometric Optimization. Mathematics. 2020; 8 (10):1714.

Chicago/Turabian Style

Jian Xu; Longyan Wang; Stephen Ntiri Asomani; Wei Luo; Rong Lu. 2020. "Improvement of Internal Flow Performance of a Centrifugal Pump-As-Turbine (PAT) by Impeller Geometric Optimization." Mathematics 8, no. 10: 1714.

Journal article
Published: 29 August 2020 in Applied Sciences
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When a pump-jet propeller rotates at high speeds, a tip vortex is usually generated in the tip clearance region. This vortex interacts with the main channel fluid flow leading to the main energy loss of the rotor system. Moreover, operating at a high rotational speed can cause cavitation near the blades which may jeopardize the propulsion efficiency and induce noise. In order to effectively improve the propulsion efficiency of the pump-jet propeller, it is mandatory to research more about the energy loss mechanism in the tip clearance area. Due to the complex turbulence characteristics of the blade tip vortex, the widely used Reynolds averaged Navier–Stokes (RANS) method may not be able to accurately predict the multi-scale turbulent flow in the tip clearance. In this paper, an unsteady numerical simulation was conducted on the three-dimensional full flow field of a pump-jet propeller based on the DES (detached-eddy-simulation) turbulence model and the Z-G-B (Zwart–Gerber–Belamri) cavitation model. The simulation yielded the vortex shape and dynamic characteristics of the vortex core and the surrounding flow field in the tip clearance area. After cavitation occurred, the influence of cavitation bubbles on tip vortices was also studied. The results revealed two kinds of vortices in the tip clearance area, namely tip leakage vortex (TLV) and tip separation vortex (TSV). Slight cavitation at J = 1.02 led to low-frequency and high-frequency pulsation in the TLV vortex core. This occurrence of cavitation promotes the expansion and contraction of the tip vortex. Further, when the advance ratio changes into J = 0.73, a third type of vortex located between TLV and TSV appeared at the trailing edge which runs through the entire rotational cycle. This study has presented the dynamic characteristics of tip vortex including the relationship between cavitation bubbles and TLV inside the pump-jet propeller, which may provide a reference for the optimal design of future pump-jet propellers.

ACS Style

Jianping Yuan; Yang Chen; Longyan Wang; Yanxia Fu; Yunkai Zhou; Jian Xu; Rong Lu. Dynamic Analysis of Cavitation Tip Vortex of Pump-Jet Propeller Based on DES. Applied Sciences 2020, 10, 5998 .

AMA Style

Jianping Yuan, Yang Chen, Longyan Wang, Yanxia Fu, Yunkai Zhou, Jian Xu, Rong Lu. Dynamic Analysis of Cavitation Tip Vortex of Pump-Jet Propeller Based on DES. Applied Sciences. 2020; 10 (17):5998.

Chicago/Turabian Style

Jianping Yuan; Yang Chen; Longyan Wang; Yanxia Fu; Yunkai Zhou; Jian Xu; Rong Lu. 2020. "Dynamic Analysis of Cavitation Tip Vortex of Pump-Jet Propeller Based on DES." Applied Sciences 10, no. 17: 5998.

Journal article
Published: 10 August 2020 in Energies
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This paper presents a multi-objective optimization strategy for pump-as-turbines (PAT), which relies on one-dimensional theory and analysis of geometrical parameters. In this strategy, a theoretical model, which considers all possible losses incurred (mainly by the components of pipe inlet, impeller and volute), has been put forward for performance prediction of centrifugal pumps operating as turbines (PAT). With the established mathematical relationship between the efficiency of PAT (both at pump and turbine mode) and the impeller controlling variables, the geometric optimization of the PAT impeller is performed with constant rotational speed. Specifically, the optimization data consist of 50 sets of impellers generated from Latin Hypercube Sampling method with its corresponding efficiencies calculated. Subsequently, the pareto-based genetic algorithm (PBGA) was adopted to optimize the geometic parameters of the impellers through the theoretical model. To validate the theoretical optimization results, the high-fidelity Computational Fluid Dynamics (CFD) simulation and the experimental data are employed for comparison of the PAT performance. The findings show that the efficiencies of both the pump and PAT optimized variables increased by 0.27% and 16.3% respectively under the design flow condition. Based on the one-dimensional theoretical optimization results, the geometry of the impeller is redesigned to suit both pump and PAT mode operations. It is concluded that the chosen design variables (b2, β1, β2, and z) have a significant impact on the PAT efficiency, which demonstrates that the optimization scheme proposed in this study is practicable.

ACS Style

Longyan Wang; Stephen Ntiri Asomani; Jianping Yuan; Desmond Appiah. Geometrical Optimization of Pump-As-Turbine (PAT) Impellers for Enhancing Energy Efficiency with 1-D Theory. Energies 2020, 13, 4120 .

AMA Style

Longyan Wang, Stephen Ntiri Asomani, Jianping Yuan, Desmond Appiah. Geometrical Optimization of Pump-As-Turbine (PAT) Impellers for Enhancing Energy Efficiency with 1-D Theory. Energies. 2020; 13 (16):4120.

Chicago/Turabian Style

Longyan Wang; Stephen Ntiri Asomani; Jianping Yuan; Desmond Appiah. 2020. "Geometrical Optimization of Pump-As-Turbine (PAT) Impellers for Enhancing Energy Efficiency with 1-D Theory." Energies 13, no. 16: 4120.

Journal article
Published: 04 May 2020 in Energies
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Pump-as-turbine (PAT) technology permits two operating states—as a pump or turbine, depending on the demand. Nevertheless, designing the geometrical components to suit these operating states has been an unending design issue, because of the multi-conditions for the PAT technology that must be attained to enhance the hydraulic performance. Also, PAT has been known to have a narrow operating range and operates poorly at off-design conditions, due to the lack of flow control device and poor geometrical designs. Therefore, for the PAT to have a wider operating range and operate effectively at off-design conditions, the geometric parameters need to be optimized. Since it is practically impossible to optimize more than one objective function at the same time, a suitable surrogate model is needed to mimic the objective functions for it to be solvable. In this study, the Latin hypercube sampling method was used to obtain the objective function values, the Adaptive Neuro-Fuzzy Inference System (ANFIS), Artificial Neural Network (ANN) and Generalized Regression Neural Network (GRNN) were used as surrogate models to approximate the objective functions in the design space. Then, a suitable surrogate model was chosen for the optimization. The Pareto-optimal solutions were obtained by using the Pareto-based genetic algorithm (PBGA). To evaluate the results of the optimization, three representative Pareto-optimal points were selected and analyzed. Compared to the baseline model, the Pareto-optimal points showed a great improvement in the objective functions. After optimization, the geometry of the impeller was redesigned to suit the operating conditions of PAT. The findings show that the efficiencies of the optimized design variables of PAT were enhanced by 23.7%, 11.5%, and 10.4% at part load, design point, and under overload flow conditions, respectively. Moreover, the results also indicated that the chosen design variables (b2, β2, β1, and z) had a substantial impact on the objective functions, justifying the feasibility of the optimization method employed in this study.

ACS Style

Stephen Ntiri Asomani; Jianping Yuan; Longyan Wang; Desmond Appiah; Kofi Asamoah Adu-Poku. The Impact of Surrogate Models on the Multi-Objective Optimization of Pump-As-Turbine (PAT). Energies 2020, 13, 2271 .

AMA Style

Stephen Ntiri Asomani, Jianping Yuan, Longyan Wang, Desmond Appiah, Kofi Asamoah Adu-Poku. The Impact of Surrogate Models on the Multi-Objective Optimization of Pump-As-Turbine (PAT). Energies. 2020; 13 (9):2271.

Chicago/Turabian Style

Stephen Ntiri Asomani; Jianping Yuan; Longyan Wang; Desmond Appiah; Kofi Asamoah Adu-Poku. 2020. "The Impact of Surrogate Models on the Multi-Objective Optimization of Pump-As-Turbine (PAT)." Energies 13, no. 9: 2271.

Review
Published: 10 April 2020 in Advances in Mechanical Engineering
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A pump-as-turbine is a hydraulic machine that can operate as a pump and turbine at the same time. Pump-as-turbine happens to be the most appropriate method for meeting the world’s energy demands, particularly in rural and isolated areas of a country. Furthermore, the operating cost of microhydropower systems is lower compared to conventional hydrodynamic turbines, but it requires high initial investment. Pump-as-turbine has been applied in many engineering fields such as irrigation, sewage, reverse osmosis, water distribution systems, farms, small pump storage power house, and pressure dropping valves. However, pump-as-turbine operates inefficiently at part-load due to lack of flow control device. In addition, the pump generates high flow instabilities in pump-as-turbine mode due to the shift of the best efficiency point toward higher head and discharge. This study extensively discusses the flow mechanism, modifications, and flow instabilities in the pump-as-turbine mode operation. First, the mechanism of the pump-as-turbine can be described as drawing out mechanical energy from the flow in the reverse mode. Since the energy drawn mainly depends on the major hydraulic components of the pump (impeller and volute), many studies have been conducted on the impeller and volute. It can be concluded that high amount of hydraulic losses is generated in pump-as-turbine mode operation. This can partly be attributed to the fixed geometrical parameters such as the stationary volute. To increase the usage of pump-as-turbine, it is very crucial to predict their performance in advance before manufacturing, which requires the understanding of the flow behavior as a result of geometrical parameters. In order to improve the energy conversion and understand the flow behavior in the centrifugal pump functioning as pump-as-turbine, the key geometrical parameters should be carefully designed. The designs of the main geometrical parameters do affect not only the hydraulic performance of pump-as-turbine but also the operational instability. The operational instability of hydraulic machines mainly depends on the pressure and the velocity fluctuation intensity generated within the flow passage as a result of the impeller–volute interaction. The magnitudes of the instabilities have the tendency to cause noise, vibration, harshness, and cavitation which reduces the life span of the hydraulic machine. Moreover, appropriate selection of the pump and unavailability of pump data contribute to the challenges faced. Finally, this review proposes specific solutions in terms of geometrical modifications and improvement of the computational design methods to handle the hydraulic losses faced during the pump operation; thus, this study can serve as a point of reference for a pump-as-turbine performance optimization.

ACS Style

Stephen Ntiri Asomani; Jianping Yuan; Longyan Wang; Desmond Appiah; Fan Zhang. Geometrical effects on performance and inner flow characteristics of a pump-as-turbine: A review. Advances in Mechanical Engineering 2020, 12, 1 .

AMA Style

Stephen Ntiri Asomani, Jianping Yuan, Longyan Wang, Desmond Appiah, Fan Zhang. Geometrical effects on performance and inner flow characteristics of a pump-as-turbine: A review. Advances in Mechanical Engineering. 2020; 12 (4):1.

Chicago/Turabian Style

Stephen Ntiri Asomani; Jianping Yuan; Longyan Wang; Desmond Appiah; Fan Zhang. 2020. "Geometrical effects on performance and inner flow characteristics of a pump-as-turbine: A review." Advances in Mechanical Engineering 12, no. 4: 1.

Journal article
Published: 14 February 2019 in Applied Sciences
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For the exploitation of wind energy, planning/designing a wind farm plays a crucial role in the development of wind farm project, which must be implemented at an early stage, and has a vast influence on the stages of operation and control for wind farm development. As a step of the wind farm planning/designing, optimizing the wind turbine placements is an effective tool in increasing the power production of a wind farm leading to an increased financial return. In this paper, the optimization of an offshore wind farm with an irregular boundary is carried out to investigate the effectiveness of grid and coordinate wind farm design methods. In the study of the grid method, the effect of grid density on the layout optimization results is explored with 20 × 30 and 40 × 60 grid cells, and the means of coping with the irregular wind farm boundary using different wind farm design methods are developed in this paper. The results show that, depending on the number of installed wind turbines, a power output increase from 1% to 1.5% is achieved by increasing the grid density from 20 × 30 to 40 × 60. However, the computational time is more than doubled, rising from 23 h to 47 h with 40 wind turbines being optimized from the coarse grid cells to the densified grid cells. In comparison, the coordinate method is the best option for achieving the largest power increase of 1.5% to 2% (relative to the coarse 20 × 30 grid method), while the least computational time (21 h with 40 wind turbines optimized) is spent.

ACS Style

Longyan Wang. Comparative Study of Wind Turbine Placement Methods for Flat Wind Farm Layout Optimization with Irregular Boundary. Applied Sciences 2019, 9, 639 .

AMA Style

Longyan Wang. Comparative Study of Wind Turbine Placement Methods for Flat Wind Farm Layout Optimization with Irregular Boundary. Applied Sciences. 2019; 9 (4):639.

Chicago/Turabian Style

Longyan Wang. 2019. "Comparative Study of Wind Turbine Placement Methods for Flat Wind Farm Layout Optimization with Irregular Boundary." Applied Sciences 9, no. 4: 639.

Journal article
Published: 18 December 2018 in Applied Sciences
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Optimal design of wind turbine placement in a wind farm is one of the most effective tools to reduce wake power losses by alleviating the wake effect in the wind farm. In comparison to the discrete grid-based wind farm design method, the continuous coordinate method has the property of continuously varying the placement of wind turbines, and hence, is far more capable of obtaining the global optimum solutions. In this paper, the coordinate method was applied to optimize the layout of a real offshore wind farm for both simplified and realistic wind conditions. A new analytical wake model (Jensen-Gaussian model) taking into account the wake velocity variation in the radial direction was employed for the optimization study. The means of handling the irregular real wind farm boundary were proposed to guarantee that the optimized wind turbine positions are feasible within the wind farm boundary, and the discretization method was applied for the evaluation of wind farm power output under Weibull distribution. By investigating the wind farm layout optimization under different wind conditions, it showed that the total wind farm power output increased linearly with an increasing number of wind turbines. Under some particular wind conditions (e.g., constant wind speed and wind direction, and Weibull distribution), almost the same power losses were obtained under the wake effect of some adjacent wind turbine numbers. A common feature of the wind turbine placements regardless of the wind conditions was that they were distributed along the wind farm boundary as much as possible in order to alleviate the wake effect.

ACS Style

Longyan Wang; Yunkai Zhou; Jian Xu. Optimal Irregular Wind Farm Design for Continuous Placement of Wind Turbines with a Two-Dimensional Jensen-Gaussian Wake Model. Applied Sciences 2018, 8, 2660 .

AMA Style

Longyan Wang, Yunkai Zhou, Jian Xu. Optimal Irregular Wind Farm Design for Continuous Placement of Wind Turbines with a Two-Dimensional Jensen-Gaussian Wake Model. Applied Sciences. 2018; 8 (12):2660.

Chicago/Turabian Style

Longyan Wang; Yunkai Zhou; Jian Xu. 2018. "Optimal Irregular Wind Farm Design for Continuous Placement of Wind Turbines with a Two-Dimensional Jensen-Gaussian Wake Model." Applied Sciences 8, no. 12: 2660.

Journal article
Published: 02 August 2018 in Journal of Wind Engineering and Industrial Aerodynamics
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The wind farm layout optimization is an effective tool to alleviate the wake power losses caused by wind turbine interactions in a wind farm. It is widely recognized that for a real wind farm site with abundant wind resources, wind speed variation of the wind condition can be approximated by the Weibull distribution, which therefore needs to be incorporated into the power evaluation of a real wind farm design. Current researchers have employed the discretization method by dividing the wind speed region into bins to calculate the power output of wind turbines under Weibull distribution, which has two main drawbacks including: 1) complicated discretization process with large computational cost and 2) dependency of calculation accuracy on the discretization resolution. This paper aims to propose a new Monte Carlo method to evaluate the wind farm power output under Weibull distribution, and verify the effectiveness and efficiency of the new method by comparison to the widely used discretization method. Through reducing the wind speed discretizing interval, it is found that when the discretized wind speed interval is smaller than 0.1 m/s, the improvement of optimization results is negligible while the computational cost significantly increases for the discretization method. By testing different sample numbers, it is found that selecting 100000 samples for the Monte Carlo method calculation is able to achieve accurate results with less computational cost than the discretization method especially when large number of turbines is installed in the wind farm. In conclusion, the Monte Carlo method greatly facilitates the power evaluation of wind farm layout optimization under Weibull distribution, with a balance between the calculation accuracy and the computational cost.

ACS Style

Longyan Wang; Jianping Yuan; Michael Cholette; Yanxia Fu; Yunkai Zhou; Andy C. Tan. Comparative study of discretization method and Monte Carlo method for wind farm layout optimization under Weibull distribution. Journal of Wind Engineering and Industrial Aerodynamics 2018, 180, 148 -155.

AMA Style

Longyan Wang, Jianping Yuan, Michael Cholette, Yanxia Fu, Yunkai Zhou, Andy C. Tan. Comparative study of discretization method and Monte Carlo method for wind farm layout optimization under Weibull distribution. Journal of Wind Engineering and Industrial Aerodynamics. 2018; 180 ():148-155.

Chicago/Turabian Style

Longyan Wang; Jianping Yuan; Michael Cholette; Yanxia Fu; Yunkai Zhou; Andy C. Tan. 2018. "Comparative study of discretization method and Monte Carlo method for wind farm layout optimization under Weibull distribution." Journal of Wind Engineering and Industrial Aerodynamics 180, no. : 148-155.

Journal article
Published: 31 July 2018 in Journal of Wind Engineering and Industrial Aerodynamics
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This paper aims to systematically study the wind farm optimization with the continuous selection of wind turbine placement (using Cartesian coordinates) and wind turbine hub height (restrained among a predefined range). Two case studies are performed. The first case involves an ideal two-dimensional (i.e., flat terrain) wind farm, and the other is a three-dimensional wind farm with real terrain altitudes. The schemes of simultaneously optimizing the wind farm layout and wind turbine hub heights applying the simplified and augmented PARK wake model are established for the ideal and real wind farm cases, respectively. The results show that applying different wind turbine hub heights for the wind farm layout optimization yields significant improvement: up to a 0.2 MW increase in total power and a 2% increase of the wind farm efficiency for the ideal wind farm. However, for the real wind farm the effectiveness of applying different wind turbine hub heights varies depending on the number of turbines installed. With less number of turbines installed, the impact of varying hub heights is small. However, significant improvements can be achieved as the number of turbines increases. With 39 wind turbines, the wind farm cost of energy can be reduced by $15000 per megawatt and the wind farm efficiency can increase by up to 0.2%. Given the nameplate capacity and the lifespan of wind farm project, the resulting effect on total energy production can be significant and thus improve the competitiveness of wind power exploitation.

ACS Style

Longyan Wang; Michael E. Cholette; Yanxia Fu; Jianping Yuan; Yunkai Zhou; Andy C.C. Tan. Combined optimization of continuous wind turbine placement and variable hub height. Journal of Wind Engineering and Industrial Aerodynamics 2018, 180, 136 -147.

AMA Style

Longyan Wang, Michael E. Cholette, Yanxia Fu, Jianping Yuan, Yunkai Zhou, Andy C.C. Tan. Combined optimization of continuous wind turbine placement and variable hub height. Journal of Wind Engineering and Industrial Aerodynamics. 2018; 180 ():136-147.

Chicago/Turabian Style

Longyan Wang; Michael E. Cholette; Yanxia Fu; Jianping Yuan; Yunkai Zhou; Andy C.C. Tan. 2018. "Combined optimization of continuous wind turbine placement and variable hub height." Journal of Wind Engineering and Industrial Aerodynamics 180, no. : 136-147.