Computational Study of Multiple Hydrokinetic Turbines: The Effect of Wake

2015 ◽  
Author(s):  
Cosan Daskiran ◽  
Jacob Riglin ◽  
Alparslan Oztekin
Keyword(s):  
Computational Study ◽  
Relative Power ◽  
Cfd Simulations ◽  
Significant Drop ◽  
Hydrokinetic Turbines ◽  
Hydrokinetic Turbine ◽  
Wake Interactions ◽  
Sst Turbulence Model ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Design

Computational Fluid Dynamics (CFD) simulations have been conducted to investigate the performance of a predetermined propeller-based hydrokinetic turbine design in staggered and non-staggered placements for river applications. Actual turbine models were used instead of low fidelity actuator line or actuator disks for CFD simulations to achieve more reliable results. The k-ω Shear Stress Transport (SST) turbulence model was employed to resolve wall effects on turbine surface and to determine wake interactions behind the turbines. The wake interaction behind the upstream turbine causes significant drop on downstream turbine performance within non-staggered configuration. The upstream turbines in both staggered and non-staggered placement offers the same relative power of 0.96, while the relative power for downstream turbine is 0.98 for staggered installment and 0.16 for inline placement.

scholarly journals A Comparative Study on the Performance of a Horizontal Axis Ocean Current Turbine Considering Deflector and Operating Depths

2020 ◽  
Vol 12 (8) ◽  
pp. 3333
Author(s):  
Nauman Riyaz Maldar ◽  
Cheng Yee Ng ◽  
Lee Woen Ean ◽  
Elif Oguz ◽  
Ahmad Fitriadhy ◽  
...  
Keyword(s):  
Fluid Pressure ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Ocean Current ◽  
Power Coefficient ◽  
Cfd Simulations ◽  
Torque Coefficient ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Design ◽  
Current Turbine

Several different designs and prototypes of ocean current turbines have been tested over recent years. For every design test, emphasis is given to achieving an optimum power output from the flow. In this study, the performance of a Horizontal Axis Ocean Current Turbine (HAOCT) has been investigated using three-dimensional Computational Fluid Dynamics (CFD) simulations for three cases, namely, (1) a turbine without a deflector, (2) a turbine with a deflector, and (3) a turbine with a deflector operating at a higher fluid depth. The turbine design was modeled in DesignModeler software and simulations were carried out in commercial CFD software Flow-3D. The Torque Coefficient (Cm) and Power Coefficient (Cp) for the turbine have been investigated for a certain range of Tip-Speed Ratios (TSRs) in a flow velocity of 0.7 m/s. Furthermore, comparisons have been made to demonstrate the effect of the deflector on the performance of the turbine and the influence of a higher fluid pressure on the same. The results from the simulations indicate that the higher value of Cp was achieved for Case 2 as compared to the other two cases. The findings from the study indicate that the use of the deflector enhances the performance of the turbine. Furthermore, a higher fluid pressure acting on the turbine has a significant effect on its performance.

Impact of Blockage on the Hydrodynamic Performance of Oscillating-Foils Hydrokinetic Turbines

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Etienne Gauthier ◽  
Thomas Kinsey ◽  
Guy Dumas
Keyword(s):  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Blockage Ratio ◽  
Cfd Simulations ◽  
Hydrokinetic Turbines ◽  
Marine Energy ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Do So ◽  
Oscillating Foils

This paper describes a study of the impact of confinement on the hydrodynamic performance of oscillating-foils hydrokinetic turbines (OFHT). This work aims to contribute to the development of standards applying to marine energy converters. These blockage effects have indeed to be taken into account when comparing measurements obtained in flumes, towing tanks, and natural sites. This paper provides appropriate correction formula to do so for OFHT based on computational fluid dynamics (CFD) simulations performed at a Reynolds Number Re = 3 × 106 for reduced frequencies between f* = 0.08 and f* = 0.22 considering area-based blockage ratios ranging from ε = 0.2% to 60%. The need to discriminate between the vertical and horizontal confinement and the impact of the foil position in the channel are also investigated and are shown to be of second-order as compared to the overall blockage level. As expected, it is confirmed that the power extracted by the OFHT increases with the blockage level. It is further observed that for blockage ratio of less than ε = 40%, the power extracted scales linearly with ε. The approach proposed to correlate the performance of the OFHT in different blockage conditions uses the correction proposed by Barnsley and Wellicome and assumes a linear relation between the power extracted and the blockage. This technique is shown to be accurate for most of the practical operating conditions for blockage ratios up to 50%.

Numerical simulation of ramp induced shock wave/boundary-layer interaction in turbulent flow

2013 ◽  
Vol 117 (1192) ◽  
pp. 629-638 ◽  
Author(s):  
Asmelash H. A. ◽  
R. R. Martis ◽  
A. Singh
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Computational Study ◽  
Full Range ◽  
Layer Interaction ◽  
Surface Pressure Distribution ◽  
Boundary Layer Interaction ◽  
Sst Turbulence Model ◽  
Free Stream Mach Number ◽  
Computational Fluid Dynamics Cfd

Abstract A computational study has been carried out to analyse the shock wave turbulent boundary layer interaction in a two-dimensional compression ramp flow for a free stream Mach number of 2·94. Ramp angles ranging from 8° to 24° are used to produce the full range of possible flow fields, including flows with minor separation, moderate separation, and significant amount of separation. The model has been analysed using 2D numerical simulations based on a commercially available Computational Fluid Dynamics (CFD) Code, Fluent, that employs k-ω Shear Stress Transport (SST) turbulence model. The computed data for surface pressure distribution indicated a good agreement with experiment. Numerical results obtained through the present series of computations indicate an increased extent of separated zone, and thus show increased upstream influence when compared to experiment. Total pressure loss has shown to increase downstream of separation location and increase when corner angle increases. Secondary separation has been observed for higher angles.

CFD Simulations of an Axisymmetric Mixed-Compresssion Inlet With Bleed Through Discrete Holes

2003 ◽  
Author(s):  
David B. Benson ◽  
Tom I.-P. Shih ◽  
David O. Davis
Keyword(s):  
Computational Study ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Third Order ◽  
Time Stepping ◽  
Sst Turbulence Model ◽  
A Cell ◽  
Volume Method ◽  
Flux Difference ◽  
Bleed Through

CFD simulations were performed to investigate boundary-layer control through bleed patches in an axisymmetric mixed-compression inlet in which the bleed patches are modeled by two global bleed boundary conditions (BCs). In one bleed BC, the locations of the bleed holes are discerned. In the other bleed BC, each row of bleed holes is modeled as a porous surface, where the number of bleed holes in each row is accounted for by adjusting the discharge coefficient to give the correct bleed rate. Results are presented for the predicted bleed rates, pressure on the cowl and centerbody surfaces, and the flow field. Comparisons were made with available experimental data. Also presented is a method based on one-dimensional isentropic and normal shock solutions to get the flow “started” in CFD simulations of critical flow in mixed-compression inlets. This computational study is based on the ensemble-averaged conservation equations of mass (continuity), momentum (compressible Navier-Stokes), and total energy closed by shear-stress transport (SST) turbulence model, where integration is to the wall. Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids.

The Influence of the Total Pressure Profile on the Performance of Axial Gas Turbine Diffusers

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
A. Hirschmann ◽  
S. Volkmer ◽  
M. Schatz ◽  
C. Finzel ◽  
M. Casey ◽  
...  
Keyword(s):  
Flow Separation ◽  
Gas Turbines ◽  
Total Pressure ◽  
Pressure Profile ◽  
Cfd Simulations ◽  
Pressure Profiles ◽  
Industrial Gas Turbines ◽  
Sst Turbulence Model ◽  
Computational Fluid Dynamics Cfd ◽  
Highly Loaded

Large industrial gas turbines for combined heat and power generation normally have axial diffusers leading to the heat recovery steam generator. The diffusers operate with high inlet axial Mach number (0.6) and with a nonuniform inlet total pressure profile from the turbine. Tests have been carried out on a generic highly loaded axial diffuser in a scaled axial diffuser test rig, with different inlet total pressure profiles including those that might be met in practice. The results show that the inlet total pressure profile has a strong effect on the position of flow separation, whereby a hub-strong profile tends to separate at the casing and the tip-strong profile on the hub. Steady computational fluid dynamics (CFD) simulations using the shear stress transport (SST) turbulence model have been carried out based on extensive studies of the best way to model the inlet boundary conditions. These simulations provide good agreement with the prediction of separation in the diffuser but the separated regions often persist too long so that, in this highly loaded case with flow separation, the calculated diffuser pressure recovery can be in error by up to 30%.

Performance Characteristics of Vertical-Axis Off-Shore Savonius Wind and Savonius Hydrokinetic Turbines

2018 ◽  
Author(s):  
Parag K. Talukdar ◽  
Vinayak Kulkarni ◽  
Ujjwal K. Saha
Keyword(s):  
Energy Demand ◽  
Computational Study ◽  
Renewable Energy Sources ◽  
Electrical Power ◽  
Clean Energy ◽  
Vertical Axis ◽  
Input Power ◽  
Offshore Wind ◽  
Hydrokinetic Turbines ◽  
Hydrokinetic Turbine

The rise in energy demand, climate change and depletion of fossil fuel, encourages the researchers to find a solution to the scarcity of clean energy. Therefore, the extraction of energy from renewable energy sources has become a topic of interest in the past few decades across the globe. Thus, harvesting the offshore wind and hydro energy and converting it to electrical power using various electromechanical devices has been a challenge. In this context, the vertical-axis Savonius wind and Savonius hydrokinetic turbines appear to be promising concept for energy conversion because of their good self-starting capability and simplicity in design. The present study attempts to characterize the performances of a Savonius wind turbine (SWT) and a Savonius hydrokinetic turbine (SHT) under identical input flow conditions. In order to characterize their performances, the SWT is tested in a low-speed wind tunnel with closed test section whereas the SHT is tested in an open channel flume. In each case, the torque and power coefficients are estimated at different mechanical loading conditions. It is observed that the SWT and SHT demonstrate peak power coefficients of 0.25 and 0.28 respectively for the same input power. However, the SWT is found to operate over a slightly wider range of tip-speed ratios than the SHT before the onset of stall. Finally, the computational study using ANSYS 14.5 has been carried out to evaluate the flow physics of the turbine at various azimuthal positions.

Hydrokinetic turbine array modeling for performance analysis and deployment optimization

2018 ◽  
Vol 42 (4) ◽  
pp. 370-381 ◽  
Author(s):  
Sébastien Bourget ◽  
Olivier Gauvin-Tremblay ◽  
Guy Dumas
Keyword(s):  
Cfd Simulation ◽  
Three Dimensional ◽  
Free Surface Flows ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Power Extraction ◽  
Hydrokinetic Turbine ◽  
Wake Interactions ◽  
Array Optimization ◽  
Turbine Wake

The promising preliminary results of an ongoing investigation aimed at developing a turbine array optimization tool are presented. This tool uses three-dimensional Reynolds-averaged Navier–Stokes (3D RANS) CFD simulations of free-surface flows to capture blockage effects and turbine-wake interactions present in dense river arrays. Turbines are represented individually into the river model using actuating regions inside which momentum source terms are distributed non-uniformly and scaled with turbine force coefficients (defined with regards to a local velocity scale). These data are derived from a high-fidelity CFD simulation of the specific turbine operating near maximum power extraction.

Computational Study of Viscoelastic Flows in Microchannels

2021 ◽  
Author(s):  
Guanyang Xue ◽  
Xuanhong Cheng ◽  
Alparslan Oztekin
Keyword(s):  
Numerical Study ◽  
Computational Study ◽  
Viscoelastic Flows ◽  
Computational Domain ◽  
Cfd Simulations ◽  
First Normal Stress Difference ◽  
Computational Fluid Dynamics Cfd ◽  
Convergence Study ◽  
Cell Densities ◽  
Mesh Convergence

Abstract Computational Fluid Dynamics (CFD) simulations have been performed in a 2D cross-section of the microchannel to characterize the viscoelastic flow field using OpenFOAM with customized stabilizing methods. The continuity and momentum equations coupled with the Giesekus constitutive model are solved. The computational domain consists of a straight main channel that is 100 μm in width and a 1:4 square-shaped cavity in the middle of the channel. The mesh convergence study is performed with both structured and unstructured cells. Flow and stress fields are compared with different cell densities. The numerical study is carried out on various Deborah numbers (De). The first normal stress difference is computed to examine the elastic lift force for future studies for nanoparticle separations. The vortex on the expansion side shrinks while the contraction side expands as De is increased. A banded zone of stronger N1 in the bulk region of the cavity, observed at higher De, could be favorable in particle separation applications. As the simulation process being validated, this study can help with future improvements to achieve higher flow rates.

Computational Study on Noise of Urban Air Mobility Quadrotor Aircraft

2021 ◽  
Author(s):  
Zhongqi (Henry) Jia ◽  
Seongkyu Lee
Keyword(s):  
Sound Pressure ◽  
Computational Study ◽  
Urban Air ◽  
Noise Levels ◽  
Cfd Simulations ◽  
Community Noise ◽  
Cfd Models ◽  
Quadrotor Aircraft ◽  
Computational Fluid Dynamics Cfd ◽  
The One

This paper investigates the acoustics of a one-passenger and a six-passenger quadrotor urban air mobility (UAM) aircraft in level flight based on a high-fidelity computational fluid dynamics (CFD) approach. The CFD simulations are carried out using the HPCMP CREATETM-AV multidisciplinary rotorcraft analysis and simulation tool Helios. The acoustic simulations are performed using the acoustic prediction tool PSU-WOPWOP. A total of three CFD models are simulated: a one-passenger isolated rotor configuration, a one-passenger full configuration with a fuselage, and a six-passenger isolated rotor configuration. The noise comparison between the one-passenger isolated rotor case and the full configuration case shows that the vehicle fuselage increases the A-weighted sound pressure level (SPL) up to 5 dB. The acoustic comparison between the one-passenger and the six-passenger isolated rotor configuration shows that the maximum overall SPL difference is up to 14 dB. Furthermore, it is shown that the noise of the six-passenger configuration is approximately 11 dB lower than that of a similar-sized conventional helicopter in an overhead scenario. The community noise impact of UAM aircraft is also assessed and compared to various background noise levels. The results show that the one-passenger quadrotor noise can be fully masked by freeway noise at an altitude greater than or equal to 1000 ft, while the six-passenger quadrotor noise can only be partially masked by freeway noise even at an altitude of 1000 ft.

scholarly journals Radial Turbine Design for Solar Chimney Power Plants

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 674
Author(s):  
Paul Caicedo ◽  
David Wood ◽  
Craig Johansen
Keyword(s):  
Power Plants ◽  
Reference Frames ◽  
Three Dimensional ◽  
Discrete Ordinates ◽  
Large Area ◽  
Solar Chimney ◽  
Cfd Simulations ◽  
Radial Turbine ◽  
Design Changes ◽  
Turbine Design

Solar chimney power plants (SCPPs) collect air heated over a large area on the ground and exhaust it through a turbine or turbines located near the base of a tall chimney to produce renewable electricity. SCPP design in practice is likely to be specific to the site and of variable size, both of which require a purpose-built turbine. If SCPP turbines cannot be mass produced, unlike wind turbines, for example, they should be as cheap as possible to manufacture as their design changes. It is argued that a radial inflow turbine with blades made from metal sheets, or similar material, is likely to achieve this objective. This turbine type has not previously been considered for SCPPs. This article presents the design of a radial turbine to be placed hypothetically at the bottom of the Manzanares SCPP, the only large prototype to be built. Three-dimensional computational fluid dynamics (CFD) simulations were used to assess the turbine’s performance when installed in the SCPP. Multiple reference frames with the renormalization group k-ε turbulence model, and a discrete ordinates non-gray radiation model were used in the CFD simulations. Three radial turbines were designed and simulated. The largest power output was 77.7 kW at a shaft speed of 15 rpm for a solar radiation of 850 W/m2 which exceeds by more than 40 kW the original axial turbine used in Manzanares. Further, the efficiency of this turbine matches the highest efficiency of competing turbine designs in the literature.

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