scholarly journals Numerical model and hydrodynamic performance of tuna finlets

2022 ◽  
pp. 100322
Author(s):  
Jun-Duo Zhang ◽  
Wei-Xi Huang
Keyword(s):  
Numerical Model ◽  
Hydrodynamic Performance

scholarly journals Numerical Simulation and Hydrodynamic Performance Predicting of 2 Two-Dimensional Hydrofoils in Tandem Configuration

2021 ◽  
Vol 9 (5) ◽  
pp. 462
Author(s):  
Yuchen Shang ◽  
Juan J. Horrillo
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Resource Constraints ◽  
Lift Coefficient ◽  
Parametric Method ◽  
Experimental Results ◽  
Hydrodynamic Performance ◽  
Tandem Configuration ◽  
Artificial Neural Network Ann ◽  
Naca 0012

In this study we investigated the performance of NACA 0012 hydrofoils aligned in tandem using parametric method and Neural Networks. We use the 2D viscous numerical model (STAR-CCM+) to simulate the hydrofoil system. To validate the numerical model, we modeled a single NACA 0012 configuration and compared it to experimental results. Results are found in concordance with the published experimental results. Then two NACA 0012 hydrofoils in tandem configuration were studied in relation to 788 combinations of the following parameters: spacing between two hydrofoils, angle of attack (AOA) of upstream hydrofoil and AOA of downstream hydrofoil. The effects exerted by these three parameters on the hydrodynamic coefficients Lift coefficient (CL), Drag Coefficient (CD) and Lift-Drag Ratio (LDR), are consistent with the behavior of the system. To establish a control system for the hydrofoil craft, a timely analysis of the hydrodynamic system is needed due to the computational resource constraints, analysis of a large combination and time consuming of the three parameters established. To provide a broader and faster way to predict the hydrodynamic performance of two hydrofoils in tandem configuration, an optimal artificial neural network (ANN) was trained using the large combination of three parameters generated from the numerical simulations. Regression analysis of the output of ANN was performed, and the results are consistent with numerical simulation with a correlation coefficient greater than 99.99%. The optimized spacing of 6.6c are suggested where the system has the lowest CD while obtaining the highest CL and LDR. The formula of the ANN was then presented, providing a reliable predicting method of hydrofoils in tandem configuration.

scholarly journals Numerical Modeling and Dynamic Analysis of a Wave-Powered Reverse-Osmosis System

2018 ◽  
Vol 6 (4) ◽  
pp. 132
Author(s):  
Yi-Hsiang Yu ◽  
Dale Jenne
Keyword(s):  
Numerical Model ◽  
Reverse Osmosis ◽  
Flow Rate ◽  
Wave Energy ◽  
Energy Resource ◽  
Diffraction Method ◽  
Hydrodynamic Performance ◽  
Water Model ◽  
Hydraulic Pressure ◽  
Water Production

A wave energy converter (WEC) system has the potential to convert the wave energy resource directly into the high-pressure flow that is needed by the desalination system to pump saltwater to the reverse-osmosis membrane and provide the required pressure level to generate freshwater. In this study, a wave-to-water numerical model was developed to investigate the potential use of a wave-powered desalination system (WPDS) for water production. The model was developed by coupling a time-domain radiation-and-diffraction method-based numerical tool (WEC-Sim) for predicting the hydrodynamic performance of WECs with a solution-diffusion model that was used to simulate the reverse-osmosis (RO) process. The objective of this research is to evaluate the WPDS dynamics and the overall efficiency of the system. To evaluate the feasibility of the WPDS, the wave-to-water numerical model was applied to simulate a desalination system that used an oscillating surge WEC device to pump seawater through the system. The hydrodynamics WEC-Sim simulation results for the oscillating surge WEC device were validated against existing experimental data. The RO simulation was verified by comparing the results to those from the Dow Chemical Company’s reverse osmosis system analysis (ROSA) model, which has been widely used to design and simulate RO systems. The wave-to-water model was then used to analyze the WPDS under a range of wave conditions and for a two-WECs-coupled RO system to evaluate the influence of pressure and flow rate fluctuation on the WPDS performance. The results show that the instantaneous energy fluctuation from waves has a significant influence on the responding hydraulic pressure and flow rate, as well as the recovery ratio and, ultimately, the water-production quality. Nevertheless, it is possible to reduce the hydraulic fluctuation for different sea states while maintaining a certain level of freshwater production, and a WEC array that produces water can be a viable, near-term solution to the nation’s water supply. A discussion on the dynamic impact of hydraulic fluctuation on the WPDS performance and potential options to reduce the fluctuation and their trade-offs is also presented.

Marine Ducted Propeller Blade Fracture Fault Diagnosis Technology Based on CFD

2014 ◽  
Vol 488-489 ◽  
pp. 1219-1223
Author(s):  
Li Jian Ou ◽  
Feng Hong Wang ◽  
Wei Zhang
Keyword(s):  
Fault Diagnosis ◽  
Numerical Model ◽  
Flow Field ◽  
Unsteady Flow ◽  
Hydrodynamic Performance ◽  
Analysis Method ◽  
Fluctuating Pressure ◽  
Ducted Propeller ◽  
Pressure Time ◽  
Ducted Propellers

The numerical model of the unsteady flow field of ducted propellers is based on CFD (computational fluid dynamics). By applying the numerical model, the unsteady flow field of the ducted propeller with the fracture in different positions of a certain blade is simulated and its unsteady hydrodynamic performance is numerically analyzed. By extracting the fluctuating pressure data of the duct inner wall monitoring points,the fluctuating pressure-time oscillogram of ducted propellers is obtained, and then the spectrum is obtained by FFT transformation of the oscillogram. A blade fracture fault diagnosis technology of ducted propellers, which combines oscillogram analysis method with spectrum analysis method, is put forward by analyzing and studying the oscillogram and the spectrum.

Influence Analysis of Blade Fracture on Hydrodynamic Performance of Ducted Propellers Based on CFD

2013 ◽  
Vol 300-301 ◽  
pp. 1071-1076 ◽  
Author(s):  
Li Jian Ou ◽  
De Yu Li ◽  
Wei Zhang
Keyword(s):  
Numerical Model ◽  
Periodic Variation ◽  
Hydrodynamic Performance ◽  
Normal Variation ◽  
Current Field ◽  
Force Coefficient ◽  
Ducted Propeller ◽  
Bearing Force ◽  
Thrust And Torque ◽  
Ducted Propellers

The numerical model of the unsteady flow field of ducted propellers is based on CFD (computational fluid dynamics). By applying the numerical model, the unsteady hydrodynamic performance of the ducted propeller with the fracture at different positions of a certain blade is numerically analyzed under three different wake current fields. Based on regress analysis ,the relationships between the mean KQ、mean KT and the quantity of the blade fracture of ducted propellers are obtained; and the relationships between hydrodynamic coefficients Kp, KQ, KFy (Bearing force coefficient of the propeller) and wake current fields , the quantity of the blade fracture are respectively further analyzed. The results show that: (1) with the increase of the quantity of the blade fracture, the amplitude of bearing force periodic variation of propellers increases, while the thrust and torque reduce; (2) the bearing force of propellers is similarly sine-varying, and the frequency of its variation is unrelated to the normal variation frequency of the wake current field. The more non-uniform the wake current field is, the more the amplitude of its periodic variation is; (3) the thrust and torque of propeller are similarly sine-varying, and the frequencies of their variation are related to the normal variation frequency of the wake current field. And the frequencies equal the shaft frequency multiplied the normal variation frequency of the wake current field. The more non-uniform the wake current field is, the more the amplitude of their periodic variation is.

A STUDY OF FLUID-MEMBRANE INTERACTIONS THAT LIMIT THE OUTPUT OF PERISTALTIC MICROPUMPS

2011 ◽  
Vol 11 (02) ◽  
pp. 325-336 ◽  
Author(s):  
CHAN YOUNG PARK ◽  
MAIYA SHUR ◽  
C. FORBES DEWEY
Keyword(s):  
Fluid Flow ◽  
Numerical Model ◽  
Flow Rate ◽  
Middle Layer ◽  
Bottom Layer ◽  
Experimental Models ◽  
Hydrodynamic Performance ◽  
Fluid Membrane ◽  
Peristaltic Micropump ◽  
Relationship Of

In many microfluidic devices, fluid flow is generated using micropumps like peristaltic micropumps. However the hydrodynamic performance of peristaltic micropumps has not been fully understood and furthermore the effect of dynamic interaction of pumping membrane and fluid flow has not been studied yet. To fill this gap, we studied the hydrodynamic performance of a peristaltic micropump using a numerical model incorporating the fluid-solid interactions. The model consisted of 3 layers; the top layer was the flow channel of 10 μm high, the middle layer was the 5~30 μm thick pumping membrane and the bottom layer was the 3 or 5 pumping chambers. By applying a pumping sequence at a frequency between 16~166 Hz, we calculated flow rate for at least 4 cycles and used the fourth or fifth cycle to evaluate the flow rate per a cycle. We found that the numerical model closely replicated the frequency vs. flow rate relationship of a peristaltic micropump as shown earlier in experimental models. We further found that the flow rate of a peristaltic micropump could be improved by increasing the number of pumping chambers or the thickness of pumping membrane.

scholarly journals Analysis of a Wave-Powered, Reverse-Osmosis System and its Economic Availability in the United States

2017 ◽  
Author(s):  
Yi-Hsiang Yu ◽  
Dale Jenne
Keyword(s):  
United States ◽  
Numerical Model ◽  
Reverse Osmosis ◽  
Wave Energy ◽  
The United States ◽  
Hydrodynamic Performance ◽  
Clean Water ◽  
Water Production ◽  
Potential Cost ◽  
Pressurized Water

A wave energy converter (WEC) system has the potential to convert the wave energy resource directly into the high-pressure flow that is needed by the desalination system to permeate saltwater through the reverse-osmosis membrane to generate clean water. In this study, a wave-to-water numerical model was developed to investigate the potential use of a wave-powered desalination system (WPDS) for water production in the United States. The model was developed by coupling a time-domain radiation-and-diffraction-method-based numerical tool (WEC-Sim) for predicting the hydrodynamic performance of WECs with a solution-diffusion model that was used to simulate the reverse-osmosis process. To evaluate the feasibility of the WPDS, the wave-to-water numerical model was applied to simulate a desalination system that used an oscillating surge WEC device to pump seawater through the system. The annual water production was estimated based on the wave resource at a reference site on the coast of northern California to investigate the potential cost of water in that area, where the cost of water and electricity is high compared to other regions. In the scenario evaluated, for a 100-unit utility-scale array, the estimated levelized cost of energy for these WECs is about 3–6 times the U.S.’s current, unsubsidized electricity rates. However, with clean water as an end product and by directly producing pressurized water with WECs, rather than electricity as an intermediary, it is presently only 12% greater than typical water cost in California. This study suggests that a WEC array that produces water may be a viable, near-term solution to the nation’s water supply, and the niche application of the WPDS may also provide developers with new opportunities to further develop technologies that benefit both the electric and drinking water markets.

Seakeeping Behavior of an Innovative, Twin-Hull LNG-FPSO Design During Side by Side Offloading Operations: A Numerical and Experimental Investigation

2018 ◽  
Author(s):  
Georgios Gkikas
Keyword(s):  
Experimental Investigation ◽  
Numerical Model ◽  
Numerical Realization ◽  
Lessons Learned ◽  
Hydrodynamic Performance ◽  
Mooring System ◽  
Time Domain Simulation ◽  
Response Amplitude Operators ◽  
The Time Domain ◽  
Good Agreement

A numerical and experimental investigation is performed with respect to the seakeeping behavior of a prototype, twin-hull, LNG-FPSO and its hydromechanic interactions with the offtake (LNG) shuttle carrier during Side-by-Side offloading. The numerical model describing the SbS mooring system as well as the assumptions and calibration steps made towards the development of a robust numerical realization are presented herewith. Following calibration, the numerical model was tested against dedicated seakeeping experiments in order to assess the effectiveness of the proposed approach as well as the hydrodynamic performance of the overall offloading system. For a more realistic offloading-scenario case, three-component, i.e., wave, wind and current, offloading environments were used for validation purposes. For the time domain simulation, as far as the hydrodynamic (diffraction) database is concerned, the multibody response amplitude operators are implemented directly, instead of employing retardation functions, in order to observe whether such an approach can still yield robust results for such complicated hydromechanic system. Statistics of the relative motions between the LNG-FPSO and LNGC manifolds, fender loads and lines’ tensions are obtained and presented, illustrating the good agreement between numerical and experimental results. Lessons learned and further recommendations are subsequently summarized and stated.

Hydrodynamic analysis of wave interactions with a moored floating breakwater using the element-free Galerkin method

2003 ◽  
Vol 30 (4) ◽  
pp. 720-733 ◽  
Author(s):  
Jeongwoo Lee ◽  
Woncheol Cho
Keyword(s):  
Numerical Model ◽  
Galerkin Method ◽  
Hydrodynamic Performance ◽  
Mooring Line ◽  
Element Free Galerkin Method ◽  
Wave Interactions ◽  
Element Free Galerkin ◽  
Floating Breakwater ◽  
Element Free ◽  
Line Condition

This paper deals with a numerical investigation of incident wave interactions with a moored pontoon-type floating breakwater. The element-free Galerkin method, in which only nodal data are required to analyze the problem, is employed to solve the diffraction and radiation boundary value problems addressed by the modified Helmholtz equation. The numerical model includes the hydrodynamic and mooring analyses, and it is validated by previous numerical and experimental results. Using the numerical model, we are able to assess the hydrodynamic performance of a moored pontoon-type floating breakwater in regular waves. Numerical results are presented to show the effects of wave conditions and mooring system configuration. This paper also presents the simple forms of stiffness coefficients of a slack mooring line. The influence of mooring line condition on the performance of a floating breakwater is highlighted. Key words: moored floating breakwater, element-free Galerkin method, mooring line condition.

Gravity wave interaction with multiple submerged artificial reefs

2020 ◽  
pp. 147509022096084
Author(s):  
KG Vijay ◽  
S Neelamani ◽  
CS Nishad ◽  
T Sahoo
Keyword(s):  
Numerical Model ◽  
Pressure Drop ◽  
Gravity Wave ◽  
Wave Interaction ◽  
Hydrodynamic Performance ◽  
Artificial Reefs ◽  
Intermediate Water ◽  
Model Based ◽  
Rate Of Increase ◽  
Base Width

In the present study, gravity wave interaction with a series of submerged artificial permeable reefs is analysed within the framework of linearised water wave theory. For wave past porous walls of the artificial reefs, a quadratic pressure drop is assumed to account for the wave energy dissipation due to the changes in wave height. The physical problem is handled for a solution using a numerical model based on the iterative multi-domain boundary element method and the developed numerical model is validated with known results in the literature. The iterative model is compared with the numerical model based on linear pressure drop boundary condition (i.e., Darcy law). The study reveals that the wave transmission reduces with the increase in the number of reef units. It is demonstrated that the transmission coefficient can be reduced to less than 0.5 when the number of reef units is greater than or equal to three for a relative height greater than 0.7, reef porosities less than 20% and for 0.4<k0h<3.0. Bragg reflection is observed when the porosity is in the range of 0 to 10% and above which the recurrent nature of wave reflection gradually fades away due to dissipation effects. The number of peaks occurring in the shallow and intermediate water depths is equal to the number of reef units wherein the maxima occur at the first frequency. A relative increase in the base width improves the energy losses but the rate of increase in energy loss decreases. The scattering coefficient pattern is oscillatory when the relative spacing between the barriers is varied and their hydrodynamic performance is invariant for higher relative base width.

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