scholarly journals Computational Fluid Dynamics Model of Wells Turbine for Oscillating Water Column System: A Review

2021 ◽  
Vol 2053 (1) ◽  
pp. 012013
Author(s):  
N. Abdul Settar ◽  
S. Sarip ◽  
H.M. Kaidi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Water Column ◽  
Cfd Simulation ◽  
Oscillating Water Column ◽  
Wells Turbine ◽  
Flow Problems ◽  
Cfd Models ◽  
Column System ◽  
Cfd Method

Abstract Wells turbine is an important component in the oscillating water column (OWC) system. Thus, many researchers tend to improve the performance via experiment or computational fluid dynamics (CFD) simulation, which is cheaper. As the CFD method becomes more popular, the lack of evidence to support the parameters used during the CFD simulation becomes a big issue. This paper aims to review the CFD models applied to the Wells turbine for the OWC system. Journal papers from the past ten years were summarized in brief critique. As a summary, the FLUENT and CFX software are mostly used to simulate the Wells turbine flow problems while SST k-ω turbulence model is the widely used model. A grid independence test is essential when doing CFD simulation. In conclusion, this review paper can show the research gap for CFD simulation and can reduce the time in selecting suitable parameters when involving simulation in the Wells turbine.

Performance of a Shore Fixed Oscillating Water Column Device for Different Bottom Slopes and Front Wall Drafts: A Study Based on Computational Fluid Dynamics and BIEM

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Piyush Mohapatra ◽  
K. G. Vijay ◽  
Anirban Bhattacharyya ◽  
Trilochan Sahoo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Water Column ◽  
Wave Energy ◽  
High Efficiency ◽  
Boundary Integral ◽  
Hydrodynamic Performance ◽  
Chamber Pressure ◽  
Front Wall ◽  
Oscillating Water Column

Abstract Oscillating water column (OWC) wave energy converters are one of the most widely researched devices for ocean wave energy harvesting. This study investigates the hydrodynamic performance of a shore-fixed OWC device for different bottom slopes using two numerical approaches, namely, computational fluid dynamics (CFD) and boundary integral equation method (BIEM). In the BIEM method, the boundary value problem is solved in two-dimensional Cartesian coordinates using the linear water wave theory. The CFD model uses a numerical wave tank (NWT) built using the volume of fluid (VOF) method. Numerical computations are carried out for different sloped bottom geometries and front wall drafts to analyze the hydrodynamic efficiency. There is a general agreement between CFD and BIEM results in terms of resonating behavior of the device. It is observed that the front wall draft has a more significant effect, a lower draft leading to a wider frequency band for optimum conversion at high efficiency. While the BIEM-based analysis resulted in improved performance curve for few of the steeper slopes, the CFD study predicted a lower peak efficiency for the same slopes due to the consideration of real fluid characteristics. Detailed performance comparisons are presented using the time histories of free surface elevation, chamber pressure, and streamlines at different time instants within the OWC chamber.

A detailed analysis of the unsteady flow within a Wells turbine

2017 ◽  
Vol 231 (3) ◽  
pp. 197-214 ◽  
Author(s):  
Tiziano Ghisu ◽  
Pierpaolo Puddu ◽  
Francesco Cambuli
Keyword(s):  
Detailed Analysis ◽  
Water Column ◽  
Wave Energy ◽  
Oscillating Water Column ◽  
Renewable Energy Resources ◽  
Wells Turbine ◽  
Column System ◽  
Flow Parameters ◽  
Important Interaction ◽  
Acceleration And Deceleration

Sea wave energy is one of the main renewable energy resources. Its exploitation is relatively simple and determines a minimum impact on the environment. The system that is most often used for wave energy harvesting is composed of an oscillating water column device together with a Wells turbine. When designing the Wells turbine, its interaction with the oscillating water column system must be taken into account, if the energy collected is to be maximized. The most important interaction phenomenon is the so called hysteresis effect, i.e. the time delay between the piston-like motion of the air water interface and the torque developed by the turbine. This work presents a detailed analysis of the flow within an oscillating water column system, focusing on the differences in performance and in secondary flow structures between acceleration and deceleration, and between the inflow and outflow phases. This analysis demonstrates how the hysteresis between acceleration and deceleration is caused uniquely by compressibility effects within the oscillating water column system, while differences in the flow parameters and secondary structures near the rotor are negligible, if equivalent flow conditions are compared. The effects of the oscillating water column system configuration on the performance are also highlighted.

scholarly journals VERIFICATION OF SCHRENK METHOD FOR WING LOADING ANALYSIS OF SMALL UNMANNED AIRCRAFT USING NAVIERSTOKES BASED CFD SIMULATION

2018 ◽  
Vol 15 (2) ◽  
pp. 161 ◽  
Author(s):  
Arifin Rasyadi Soemaryanto ◽  
Nurhayyan Halim Rosid
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Approximation Method ◽  
Cfd Simulation ◽  
Unmanned Aircraft ◽  
Navier Stokes ◽  
Aerodynamic Load ◽  
Wing Loading ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

Prediction of an aerodynamic load acting on a wing or usually called wing loading becomes an important stage for structural analysis. Several methods have been used in estimating the wing loading. Schrenk approximation method is commonly used to achieve the fast estimation of lift distribution along wingspan, but in order to achieve a high level accuracy of aerodynamic prediction, computational fluid dynamics (CFD) with Navier Stokes-based equation can be used. LAPAN Surveillance UAV (LSU series) has been chosen to represent an aerodynamics analysis on generic small unmanned aircraft with twinboom vertical stabilizer configuration. This study was focused to verify the Schrenk approximation method using high accuracy numerical simulation (CFD). The goal of this study was to determine the lift distribution along wingspan and a number of errors between Schrenk approximation and CFD method. In this study, Schrenk approximation result showed similarity with the CFX simulation. So the two results have been verified in analysis of wing loading. ABSTRAKPrediksi dari beban aerodinamika yang terjadi pada sayap menjadi salah satu tahap yang penting dalam analisis struktur perancangan pesawat. Beberapa metode telah digunakan untuk mengestimasi besarnya beban aerodinamika pada sayap. Metode Schrenk umum digunakan untuk estimasi cepat perhitungan besar distribusi gaya angkat di sepanjang sayap. Guna mencapai tingkat akurasi yang tinggi dari prediksi aerodinamika, simulasi Computational Fluid Dynamics (CFD) dengan berbasis persamaan Navier-Stokes dapat digunakan. Pesawat nirawak LSU dipilih untuk merepresentasikan analisis aerodinamika pada pesawat nirawak dengan konfigurasi twin-tailboom pusher. Fokus dari studi yang dilakukan adalah untuk memverifikasi dari metode pendekatan dari Schrenk dengan menggunakan metode yang memiliki akurasi tinggi seperti simulasi CFD. Tujuan dari studi adalah untuk menghitung distribusi gaya angkat sepanjang sayap dan menentukan seberapa besar error dari kedua metode.

Analytical and Computational Fluid Dynamics Models of Wells Turbines for Oscillating Water Column Systems

2021 ◽  
Vol 144 (5) ◽  
Author(s):  
L. Ciappi ◽  
M. Stebel ◽  
J. Smolka ◽  
L. Cappietti ◽  
G. Manfrida
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Water Column ◽  
Analytical Model ◽  
Energy Resource ◽  
Computational Domain ◽  
Oscillating Water Column ◽  
Sea Waves ◽  
Hexahedral Elements ◽  
Dynamics Models

Abstract The sea is an important renewable energy resource for its extension and the power conveyed by waves, currents, tides, and thermal gradients. Amongst these physical phenomena, sea waves are the source with the highest energy density and may contribute to fulfilling the global increase of power demand. Despite the potential of sea waves, their harnessing is still a technological challenge. Oscillating water column systems operating with Wells turbines represent one of the most straightforward and reliable solutions for the optimal exploitation of this resource. An analytical model and computational fluid dynamics models were developed to evaluate the functioning of monoplane isolated Wells turbines. For the former modeling typology, a blade element momentum code relying on the actuator disk theory was applied, considering the rotor as a set of airfoils. For the latter modeling typology, a three-dimensional multi-block technique was implemented to create the computational domain with a fully mapped mesh composed of hexahedral elements. The employment of circumferential periodic boundary conditions allowed for the reduction of computational power and time. The models use Reynolds-averaged Navier-Stokes (RANS) or u-RANS schemes with a multiple reference frame approach or the u-RANS formulation with a sliding mesh approach. The achieved results were compared with analytical and experimental literature data for validation. All the developed models showed good agreement. The analytical model is suitable for a fast prediction of the turbine operation on a wide set of configurations during the first design stages, while the computational fluid dynamics (CFD) models are indicated for the further investigation of the selected configurations.

scholarly journals Hemodynamic analysis for stenosis microfluidic model of thrombosis with refined computational fluid dynamics simulation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yunduo Charles Zhao ◽  
Parham Vatankhah ◽  
Tiffany Goh ◽  
Rhys Michelis ◽  
Kiarash Kyanian ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Shear Rate ◽  
Cfd Simulation ◽  
Critical Role ◽  
Three Dimensions ◽  
Dynamics Simulation ◽  
Water Medium ◽  
Cfd Method

AbstractDisturbed blood flow has been increasingly recognized for its critical role in platelet aggregation and thrombosis. Microfluidics with hump shaped contractions have been developed to mimic microvascular stenosis and recapitulate the prothrombotic effect of flow disturbance. However the physical determinants of microfluidic hemodynamics are not completely defined. Here, we report a refined computational fluid dynamics (CFD) simulation approach to map the shear rate (γ) and wall shear stress (τ) distribution in the stenotic region at high accuracy. Using ultra-fine meshing with sensitivity verification, our CFD results show that the stenosis level (S) is dominant over the bulk shear rate (γ0) and contraction angle (α) in determining γ and τ distribution at stenosis. In contrast, α plays a significant role in governing the shear rate gradient (γ′) distribution while it exhibits subtle effects on the peak γ. To investigate the viscosity effect, we employ a Generalized Power-Law model to simulate blood flow as a non-Newtonian fluid, showing negligible difference in the γ distribution when compared with Newtonian simulation with water medium. Together, our refined CFD method represents a comprehensive approach to examine microfluidic hemodynamics in three dimensions and guide microfabrication designs. Combining this with hematological experiments promises to advance understandings of the rheological effect in thrombosis and platelet mechanobiology.

Validation of computational fluid dynamics simulation methods for venous pulsatile tinnitus

2021 ◽  
Author(s):  
Yue-Lin Hsieh ◽  
Dan Wang ◽  
Xiaobing Xu ◽  
Dengtao Yu ◽  
Yongzhen Wu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Doppler Ultrasound ◽  
Cfd Simulation ◽  
Computational Simulation ◽  
Case Series ◽  
Temporal Analysis ◽  
Dynamics Simulation ◽  
Pulsatile Tinnitus ◽  
Cfd Method

There has been a growing interest in the investigation of hydroacoustic characteristics of pulsatile tinnitus (PT). However, a proper technique for computational fluid dynamics (CFD) simulation has yet to be discussed. The primary goal of this paper was to investigate the intrasinus hydroacoustic characteristics of PT at the transverse-sigmoid junction (TSJ) using Doppler ultrasound and examine the validity of CFD techniques in simultaneity. The preoperative and intraoperative Doppler ultrasound were performed on a patient with PT at upper jugular vein and TSJ, respectively. Canonical CFD techniques were applied to solve the computational transverse-sigmoid sinus flow domain and compared with the Doppler’s measurements. In addition, the spectro-temporal analysis was performed for the sonification of PT. PT was associated with the recirculating flows at the TSJ according to ultrasonographic detection. This pathogenic region was characterized by a sudden deceleration of flow velocity and inverse increase of flow static pressure, which large eddy simulation (LES) resulted in the smallest 6% velocity difference compared to the measured Doppler data, albeit with little differences compared to other solvers. Therefore, based on this case study, the transient LES approach is an optimal CFD method for the computational simulation of the complex hemodynamics at the TSJ. Further numerical studies with large case series are warrranted.

An Axisymmetric Computational Fluid Dynamics Approach to the Analysis of the Working Process of a Solar Stirling Engine

2005 ◽  
Vol 128 (1) ◽  
pp. 45-53 ◽  
Author(s):  
K. Mahkamov
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cfd Simulation ◽  
Stirling Engine ◽  
Gas Temperature ◽  
Working Process ◽  
Cfd Models ◽  
Pressure Distributions ◽  
Operational Characteristics ◽  
Computational Fluid Dynamics Cfd

The use of computational fluid dynamics (CFD) models significantly extends the capabilities for the detailed analysis of the complex heat transfer and gas dynamic processes that occur in the internal gas circuit of a Stirling engine by more accurately predicting the engine’s performance. This accurate data on operational characteristics of the engine can then contribute to more precise calculations of the dimensions of a parabolic concentrator in a dish/Stirling engine installation. In this paper a successful axisymmetric CFD simulation of a solar “V”-type Stirling engine is described for the first time. The standard κ-ε turbulence model, with a moving mesh to reflect the reciprocating motion of the pistons, has been employed for the analysis of the engine’s working process. The gas temperature and pressure distributions and velocity fields in the internal gas circuit of the machine have been obtained and the pressure-volume diagrams have been calculated. Comparison of the numerical results produced from the axisymmetric CFD simulation of the engine’s working process with those computed with the use of second-order mathematical analysis shows that there are considerable differences. In particular, analysis of the data obtained indicates that the gas temperature in the compression space depends on the location in the cylinder for the given moment in the cycle and it may differ substantially from being harmonic in time.

scholarly journals Hydrodynamic performance analysis of a shore fixed oscillating water column wave energy converter in the presence of bottom variations

2019 ◽  
Vol 234 (1) ◽  
pp. 37-47
Author(s):  
Piyush Mohapatra ◽  
Trilochan Sahoo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Water Column ◽  
Boundary Integral ◽  
Hydrodynamic Performance ◽  
Design Stage ◽  
Pressure Jump ◽  
Front Wall ◽  
Oscillating Water Column ◽  
Sea Bed

In this study, the effect of the stepped sea bed on the hydrodynamic performance of an oscillating water column device is investigated using computational fluid dynamics . This investigation is performed in a numerical wave tank modeled using ANSYS Fluent, which incorporates a transient, multiphase volume of fluid method to track the air–water interface. The power take-off unit is modeled as a porous zone in the flow field to produce the pressure jump versus flow characteristics that of a real air turbine. The efficiency of the chamber with and without the stepped bottom is analyzed and compared with known results in the literature. The flow parameters such as the temporal evolution and distribution of the pressure field, velocity field and free surface are studied to understand the performance of the proposed model. The study reveals that there is an improvement in hydrodynamic efficiency with the inclusion of the stepped bottom beneath the oscillating water column chamber, which is in agreement with the previous studies carried out using analytical and boundary integral equation methods. Moreover, the computational fluid dynamics model helps to understand the flow dynamics inside the oscillating water column chamber in a more intricate manner compared to the potential flow-based studies pursued in the literature. The formation of vortices within the oscillating water column chamber, near the front wall and stepped bottom could be captured, which affects the chamber performance to a certain extent. Overall, the study could be useful in the initial design stage of shore fixed oscillating water column devices.

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