CFD and experimental investigations of a novel vertical axis Omni-flow wind turbine shroud system operating at low Reynolds numbers, typical urban flow conditions - Abstract

Oct 22, 2026

This study examines the aerodynamic performance and flow characteristics of an innovative shrouded omnidirectional wind turbine system under low Reynolds numbers and typical urban flow conditions. Four turbulence models—SST k-ω (Menter), RST, IDDES SST k-ω, and LES WALE—are evaluated against experimental results to identify the most reliable predictions. LES WALE and IDDES SST k-ω best capture turbulent and uniform regions inside and outside the shroud, with IDDES SST k-ω providing the strongest balance of accuracy and computational efficiency.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages38

Reading Time1 h 36 min

AccessFree to download

Abstract

Keywords

Introduction

Background and motivation

CFD and experimental investigations ofa novel vertical axis Omni-flow wind turbine shroud system operating at low Reynolds numbers, typical urban flow conditions Micky Mike Ngouani Siewe1*, Yong Kang Chen2*, Rodney Day3, Opukuro David-West4 1,2,4School of Physics, Engineering and Computer Science, University of Hertfordshire, Hatfield, Herts AL10 9AB, UK 3Pro Vice-Chancellor (Research & Innovation), London South Bank University, Borough Rd, London SE1 0AA, UK *[Corresponding authors:](Corresponding authors: m.ngouani-siewe2@herts.ac.uk)[ ](Corresponding authors: m.ngouani-siewe2@herts.ac.uk)[m.ngouani-siewe2@herts.ac.uk](Corresponding authors: m.ngouani-siewe2@herts.ac.uk); [y.k.chen@herts.ac.uk](y.k.chen@herts.ac.uk) Abstract This study examined the aerodynamic performance and flow characteristics of an innovative shrouded omnidirectional wind turbine system at low Reynold numbers to tackle the SDG 7 of the UN. Four turbulence models, notably the Shear Stress Transport (SST Menter) k−ω, the Reynolds Stress Transport (RST), the Improved Delay Detached Eddies Simulation (IDDES) SST k−ω, and the Large Eddy Simulation (LES WALE), were tested to find the best model(s) for this new omni-flow wind turbine. Compared with experimental results, the LES WALE and the IDDES SST k−ω models best predicted turbulent and uniform flow regions inside and outside the shroud, including CFD parameters, with one being more accurate on specific parameters such as Cd and another on other parameters. The IDDES SST k−ω excelled in predicting velocity ratios, lift coefficient (Cl) and provided the best balance of accuracy and computational efficiency of this innovative omni-direction wind turbine shroud. The novel shroud design, with its unique ability to self-start and harness omnidirectional wind at any free stream velocity for electricity generation, was a key focus of this study. The airflow inside and around the innovative shroud system was meticulously characterised for potential optimisation. Findings demonstrated that the shroud effectively redirected airflow as low as 1.5 m/s into the turbine housing and with 1.5 maximum speed ratio the airflow flew towards the outlet and generated power, leading to superior self-starting capabilities. The power output increased non-linearly with the rotational speed, achieving optimal efficiency beyond 1000 rpm. It is evident that this new system has the potential for enhanced energy capture under varying wind conditions in urban areas. Keywords Omni-Flow shrouded vertical axis wind turbine, Low noise self-starting system, CFD turbulence models, Energy harvesting in urban areas, UN sustainable development goals. | Nomenclature | | | | | --- | --- | --- | --- | | D
L
ω
e°
N
P
Cpower
R
c
Cp
Dr
H
k
LIDDES
LLES
LRANSSij
t
uj
U∞
xj
y+
Greek symbols
α
β | Drag [N] Lift [N]
Rotational speed [RPM] Flow Entrance angle [°] Blades Number [−]
Power [W] Coefficient of power [−] Rotor Blade radius [m] chord length [m] Pressure coefficient [−] Rotor diameter [m] Shroud case height [m]
Turbulent kinetic energy [m2/s2 ] IDDES length scale [m]
LES length scale [m]
RANS length scale [m] mean strain rate[1/s]
Time [s]
Velocity components [m/s]
Free stream wind speed [m/s] Coordinate variables [m] Dimensionless wall distance [-]
Wing base angle of attack [°]
Rotor blade pitch [°] | λν
ρτij Ωij θ
Abbreviations
3D CFD
DDES
DES
HAWT
VAWT
IDDES
LES
N-SRANS
SST
TSR
TKE
WALE
Cyl
UN SDG
avg
max | tip speed ratio [−] kinematic viscosity [m2/s]
air density [kg/m3 ] tensor of stress [Pa] Vorticity [1/s] Wind direction angle[°]
Three-dimensional Computational Fluid Dynamics
Delayed Detached Eddy Simulation Detached Eddy Simulation Horizontal Axis Wind Turbine
Vertical Axis Wind Turbine Improved Delayed Detached Eddy Simulation
Large Eddy Simulation Navi

FAQs

Which turbulence models were tested for the omnidirectional shrouded wind turbine?

The study tested SST k-ω (Shear Stress Transport, Menter), RST (Reynolds Stress Transport), IDDES SST k-ω (Improved Delay Detached Eddies Simulation), and LES WALE (Large Eddy Simulation with WALE).

How did the best models compare with experimental results?

LES WALE and IDDES SST k-ω best predicted turbulent and uniform flow regions inside and outside the shroud, while different models excelled for different parameters such as Cd and other metrics.

What performance improvements did the novel shroud design enable?

The shroud supports self-starting and redirects low wind speeds (down to 1.5 m/s) into the turbine housing. With a maximum speed ratio of 1.5, the flow reaches the outlet to generate power, and efficiency peaks beyond 1000 rpm.

Oct 22, 2026

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