The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Yiannis Constantinides - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Coefficient maps for riser interference analysis
ASME 2015 34th International Conference on Ocean Offshore and Arctic Engineering, 2015Co-Authors: Suneel Patel, Shankar Sundararaman, Pete Padelopoulos, Kamaldev Raghavan, Metin Karayaka, Paul R Hays, Yiannis ConstantinidesAbstract:Riser wake interference analysis is conducted based on analytical / semi-empirical models such as Blevins’ and Huse’s models. These models are used for modeling the reduction in particle flow velocity due to the presence of a cylindrical object upstream in the flow path. However, these models are often too conservative and accurate only for circular cylinders. Many top tensioned risers (TTRs) use vortex induced vibration (VIV) suppression devices such as strakes or fairings. There is a need for alternate methods to obtain drag and lift Coefficient datasets for circular cylinders with strakes and fairings. Two such approaches are to obtain data from Computational Fluid Dynamics (CFD) simulations or from experimental large-scale model test data. Interpolation and/or extrapolation methods are needed to obtain additional data points for global riser finite element analysis.This paper presents a methodology to obtain Hydrodynamic Coefficients for TTRs with VIV suppression devices. The proposed methodology uses a combination of empirical formulas based on Blevins’ model and numerical interpolation techniques along with experimental tow tank test data and CFD analysis. The resulting data is then input as user-defined drag/lift Coefficients into a global riser finite element analysis to obtain a more realistic riser system response.Copyright © 2015 by ASME
Tao Jiang - One of the best experts on this subject based on the ideXlab platform.
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estimation of the Hydrodynamic Coefficients of the complex shaped autonomous underwater vehicle tuna sand
Journal of Marine Science and Technology, 2009Co-Authors: Sulin Tang, Takeshi Nakatani, Blair Thornton, Tao JiangAbstract:Hydrodynamic Coefficients strongly affect the dynamic performance of autonomous underwater vehicles (AUVs). Thus it is important to have the true values of the Coefficients in order to simulate the AUV’s dynamic performance accurately. Although these Coefficients can be predicted by many methods, most are only applicable for AUVs with streamlined shapes. Computational fluid dynamics (CFD) can be applied to estimate the Hydrodynamic Coefficients of AUVs with complex shapes. In this study, CFD was applied to estimate the Hydrodynamic Coefficients of the AUV TUNA-SAND (which stands for terrain-based underwater navigable AUV for seafloor and natural resources development), which has a complex block-like structure. First, the validity of the CFD simulation was verified by comparison with experimental results. Second, the relationships between Hydrodynamic loads and motions for all six degrees of freedom were analyzed using the simulated results. Third, the importance of each Hydrodynamic Coefficient was investigated based on these relationships. There are 16 key damping Coefficients that relate to viscosity and 12 key inertial Coefficients that relate to the potential flow around TUNA-SAND. Finally, the values of all the key Coefficients were obtained and verified by comparing the solutions of the simulated dynamics with the experimental results.
K Chandrashekhara - One of the best experts on this subject based on the ideXlab platform.
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a neural network approach to enhance blade element momentum theory performance for horizontal axis hydrokinetic turbine application
Renewable Energy, 2019Co-Authors: A Abutunis, Rafid M Hussein, K ChandrashekharaAbstract:Abstract Blade element momentum (BEM) theory is a commonly used tool to predict the performance of horizontal axis conversion systems, such as wind and water turbines. Moreover, BEM theory can be easily integrated into many optimization techniques to improve the turbine structure and performance reliability. BEM theory though conceptually simple has different sources of convergence issues. The main focus of this work was to introduce a computational intelligence technique, namely, multilayer perceptron (MLP) neural networks (NNs) to overcome the convergence issues regardless of their sources. To improve the BEM accuracy, NNs were also employed as a multivariate interpolation tool to calculate the lift and drag Coefficients over an operational range of local Reynolds numbers. This technique was found to be easy to integrate into any modified BEM model such those account for blockage in channels. The BEM-NNs model was able to operate at a higher tip speed ratio, with no convergence problems, compared to other models. Integration of NNs as multivariate interpolation tool for Hydrodynamic Coefficient calculation further improved the power prediction compared to that when using a constant representative Reynolds number.
Suneel Patel - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Coefficient maps for riser interference analysis
ASME 2015 34th International Conference on Ocean Offshore and Arctic Engineering, 2015Co-Authors: Suneel Patel, Shankar Sundararaman, Pete Padelopoulos, Kamaldev Raghavan, Metin Karayaka, Paul R Hays, Yiannis ConstantinidesAbstract:Riser wake interference analysis is conducted based on analytical / semi-empirical models such as Blevins’ and Huse’s models. These models are used for modeling the reduction in particle flow velocity due to the presence of a cylindrical object upstream in the flow path. However, these models are often too conservative and accurate only for circular cylinders. Many top tensioned risers (TTRs) use vortex induced vibration (VIV) suppression devices such as strakes or fairings. There is a need for alternate methods to obtain drag and lift Coefficient datasets for circular cylinders with strakes and fairings. Two such approaches are to obtain data from Computational Fluid Dynamics (CFD) simulations or from experimental large-scale model test data. Interpolation and/or extrapolation methods are needed to obtain additional data points for global riser finite element analysis.This paper presents a methodology to obtain Hydrodynamic Coefficients for TTRs with VIV suppression devices. The proposed methodology uses a combination of empirical formulas based on Blevins’ model and numerical interpolation techniques along with experimental tow tank test data and CFD analysis. The resulting data is then input as user-defined drag/lift Coefficients into a global riser finite element analysis to obtain a more realistic riser system response.Copyright © 2015 by ASME
Jianhua Zhang - One of the best experts on this subject based on the ideXlab platform.
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Research of Hydrodynamic Coefficients Identification for Submarine in Vertical Motions Based on APSO
2020 IEEE International Conference on Mechatronics and Automation (ICMA), 2020Co-Authors: Ping Zhang, Changbo Liu, Jianhua ZhangAbstract:The identification of Hydrodynamic Coefficient is one of the difficulties in the study of mathematical motion model of submarine. Based on the traditional experimental equation, this paper proposes an identification method of Hydrodynamic Coefficients based on adaptive particle swarm optimization. 12 high-sensitivity Hydrodynamic Coefficients were obtained by the use of this method. Using these Coefficients, the submarine motion model was re-modeled, and the depth, trim, bow rudder and tail rudder angles in the vertical plane were simulated and compared with experimental values. The results show that it is useful to identify the Hydrodynamic Coefficients of the submarine in the vertical plane using the adaptive particle swarm optimization algorithm, and the obtained motion parameters in the vertical plane have a high degree of agreement with the experimental values.