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البحوث المنشورة
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البحث (1):
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فصل في كتاب بعنوان:
Alternative Energies
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عنوان البحث:
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Effect of Transitional Turbulence
Modelling on a Straight Blade Vertical Axis Wind Turbine
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رابط إلى البحث:
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تاريخ النشر:
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31/10/2013
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موجز عن البحث:
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The flow
around straight blade vertical axis wind turbines is typically complex at low
tip speed ratios (TSR<2). In this paper, the turbulence models which are
based on the assumption of fully developed turbulent flow, such as S-A, RNG
κ-ε and SST κ-ω have been investigated in comparison to the SST transitional
model (both with and without curvature correction) to account for the
laminar-turbulence transition. The investigation is based on the 2D unsteady
Reynolds averaged Navier-Stokes (URANS) equations using a sliding mesh
technique. It has been found that applying turbulence models based on the
assumption of fully developed flow shows significant differences in velocity
magnitude if the flow is under stall condition or wake effect compared to the
transitional model. Also, the predicted flow structure in the vicinity of the
stalled airfoils using different types of turbulence models is found to be
different compared to the un-stalled airfoils where no significant
differences in the flow field have been observed. In the wake region, the
flow varies less significantly compared to the stalled airfoils.
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البحث (2):
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عنوان البحث:
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Computational fluid
dynamics (CFD) mesh independency techniques for a straight blade vertical
axis wind turbine
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here
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تاريخ النشر:
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01/09/2013
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موجز عن البحث:
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This paper numerically investigates four
methods, namely mesh refinement, General Richardson Extrapolation (GRE), Grid
Convergence Index (GCI), and the fitting method, in order to obtain a mesh
independent solution for a straight blade vertical axis wind turbine
(SB-VAWT) power curve using computational fluid dynamics (CFD). The solution
is produced by employing the 2D Unsteady Navier–Stokes equations (URANS) with
two turbulence models (Shear Stress Transport (SST) Transitional and
ReNormalized Groups (RNG) κ − ɛ
models). The commonly applied mesh refinement is found to be computationally
expensive and not often practical even for a full 2D model of the turbine.
The mesh independent power coefficient produced using the General Richardson
Extrapolation method is found to be encouraging. However, the Grid
Convergence Index may not be applicable in mesh independency tests due to the
oscillatory behaviour of the convergence for the turbine power coefficient.
As an alternative, the fitting method shows a good potential for the
predicting of the mesh independent power coefficient without the necessity to
consider a massive number of meshes.
N.B: This
paper is considered of special interest to the Energy sector, therefore it is
featured in Renewable Energy Global Innovations Series as Key Wind Energy
Article and in SCIENCEDIRECT TOP 25 list of most downloaded articles ranked
23rd on the top 25.
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البحث (3):
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عنوان البحث:
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CFD
Sensitivity Analysis of a Straight-Blade Vertical Axis Wind Turbine
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رابط إلى البحث:
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تاريخ النشر:
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01/11/2012
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موجز عن البحث:
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This paper investigates the flow field features and the predicted
power coefficient of a straight blade vertical axis wind turbine (SB-VAWT)
using computational fluid dynamics modeling using 2D simulations. The
Unsteady Navier-Stokes equations are solved with the concept of Reynolds
averaging using the commercial software FLUENT and the sliding mesh technique
is applied. In the mesh phase, three parameters have been investigated,
namely the cell type, the cell aspect ratio on the airfoil surface, and the
total number of cells in the computational domain. In the simulation phase,
two parameters have been investigated, namely the time step/Courant number,
and the turbulence intensity. Significant differences have been observed in
the flow field features and on the predicted power coefficient for some of
these parameters which if not considered in details could lead to unreliable
predictions. The sensitivity of the parameters is not equally significant and
this paper suggests which parameters should be focused on in the modeling
process. The convergence behavior of the quadrilateral based mesh is found to
be more consistent compared to the triangular based mesh. In the mesh phase,
the cell aspect ratio on the airfoil surface was found to be a significant
factor, whereas the turbulence intensity was found to be a significant factor
in the simulation phase.
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البحث (4):
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عنوان البحث:
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Modeling dynamic stall of a straight blade vertical axis wind
turbine
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here
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تاريخ النشر:
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08/2015
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موجز البحث:
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This paper investigates the development of the dynamic stall of a
full straight blade vertical axis wind turbine (SB-VAWT) using computational
fluid dynamic modeling for solving the 2D Navier–Stokes equations. The 2D
unsteady Navier–Stokes equations are solved with the concept of Reynolds
averaging. A mesh independency test is analyzed using the General Richardson
Extrapolation technique. Two turbulence models are applied, namely the SST
k−ωk−ω and the Transition SST models. It has been found that the stall
development is extremely sensitive to the transitional modeling and small
laminar separation bubbles will only be accurately predicted by accounting
for the transition. However, the transition affects the overall turbine
performance by up to 20% and delays the peak of the predicted torque by about
11°, and therefore it is crucial to include laminar-turbulence transition in
the design and optimization process of SB-VAWTs
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البحث (5):
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عنوان البحث:
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2D-CFD analysis of the
effect of trailing edge shape on a straight-blade vertical axis wind turbine
performance
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رابط إلى البحث:
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here
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تاريخ النشر:
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24/11/2014
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ملخص المشاركة:
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This paper numerically investigates the effect of the trailing
edge profile on the performance of the straight blade vertical axis wind
turbine (SB-VAWT). In a 2D cross section of the SB-VAWT model, four trailing
edge profile are implanted, namely sharp, rounded, S-blunt and R-blunt. The
numerical investigation is based on the unsteady Reynolds averaged
Navier-Stokes (URANS) equations combined with the Transition SST model in
order to account for the transition in the boundary layer in the vicinity of
the airfoils. It has been found the trailing edge profile may play a
significant role in improving the turbine performance and should be accounted
for in the design process of the SB-VAWT.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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6th International conference on Advanced
Computational Engineering and Experimenting,
ACE-X2012
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تاريخ الإنعقاد:
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01/07/2012
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مكان
الإنعقاد:
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Istanbul, Turkey
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طبيعة المشاركة:
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Presentation of a paper
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عنوان المشاركة:
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Effect of Transitional Turbulence Modelling on a Straight Blade
Vertical Axis Wind Turbine
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ملخص المشاركة:
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The flow around straight blade vertical axis
wind turbines is typically complex at low tip speed ratios (TSR<2). In
this paper, the turbulence models which are based on the assumption of fully
developed turbulent flow, such as S-A, RNG κ-ε and SST κ-ω have been
investigated in comparison to the SST transitional model (both with and
without curvature correction) to account for the laminar-turbulence
transition. The investigation is based on the 2D unsteady Reynolds averaged
Navier-Stokes (URANS) equations using a sliding mesh technique. It has been
found that applying turbulence models based on the assumption of fully
developed flow shows significant differences in velocity magnitude if the
flow is under stall condition or wake effect compared to the transitional model. Also, the predicted flow structure in the vicinity of the
stalled airfoils using different types of turbulence models is found to be
different compared to the un-stalled airfoils where no significant
differences in the flow field have been observed. In the wake region, the
flow varies less significantly compared to the stalled airfoils.
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المؤتمر (2):
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عنوان المؤتمر:
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13th International Conference on Wind
Engineering (ICWE13)
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تاريخ الإنعقاد:
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10/07/2011
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مكان
الإنعقاد:
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Amsterdam, Netherland
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طبيعة المشاركة:
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Paper presentation
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عنوان المشاركة:
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CFD modelling investigation of a straight-blade vertical axis
wind turbine
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ملخص المشاركة:
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The aim of this paper was to investigate some
modelling aspects of computational fluid dynamics, in particular mesh
generation and simulation. Two cell types have been studied, namely
quadrilateral and triangular shapes. It has been found that the cell shape is
responsible of about 5% difference in the power predicted. However, the error
could be more due to the false diffusion, which is more enhanced when using
the quadrilateral cells. The numerical diffusion is significantly harmful to
the solution accuracy and the stability of the solver in modelling straight
blade vertical axis wind turbines. This problem could be reduced by
increasing the domain mesh size and applying higher discretization schemes.
Also, we have found that the aspect ratio on the airfoil surface is a
significant factor in modelling vertical axis wind turbines. It is crucial to
analyse how many computational points are required on the surface of the
airfoil in order to obtain good grid independent solution. The results
obtained using different domain mesh sizes of quadrilateral based meshes are
similar. However, the triangular based mesh results are found not to be
similar. Also, It is has been found that the estimation of the intensity
level could significantly affect the results obtained. However, the turbine
power coefficient value obtained is almost the same for different length
scale values.
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المؤتمر (3):
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عنوان المؤتمر:
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International conference on sustainable
energy & environmental protection )SEEP 2009)
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تاريخ الإنعقاد:
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12/08/2009
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مكان
الإنعقاد:
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Dublin, Ireland
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طبيعة المشاركة:
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Paper Presentation
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عنوان المشاركة:
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Analysis Of Three Selected Design Parameters Related To A
Fixed-Pitch Straight-Bladed Vertical Axis Wind Turbine
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ملخص المشاركة:
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The fixed-pitch straight-bladed vertical axis wind turbine
(SB-VAWT) is one of the simplest types of wind turbine. The overall cost of
the SB-VAWT will mainly depend on judicious choice of multiple design
parameters. An attempt has been made in this paper to analyze the influence
of three design parameters related to smaller-capacity fixed pitch SB-VAWT
with the help of a computational scheme. The three design parameters are: (i)
solidity, (ii) aspect ratio and (iii) blade pitching. Effect of these
parameters is analyzed for a SB-VAWT equipped with a special purpose airfoil
“MIVAWT1” which has been designed for a smaller-capacity
fixed-pitch SB-VAWT. It has been demonstrated in this paper that proper
selections of these three parameters are important for a cost effective
smaller-capacity SB-VAWT which can be considered as a candidate for urban and
offgrid rural applications.
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