Considering the dynamic stall effects in engineering calculations is essential for correcting the aerodynamic loads acting on wind turbines, both during power production and stand-still cases, and impacts significantly the turbine aeroelastic stabili...
The complex unsteady aerodynamics of vertical axis wind turbines (VAWT) poses significant challenges to the simulation tools. Dynamic stall is one of the phenomena associated with the unsteady conditions for VAWTs, and it is in the focus of the study...
Present studies are specifically aimed at investigating the sensitivity of different dynamic stall models when exposed to various excitation frequencies. The investigations are targeted at blade edgewise vibrations. This is carried out on a modified...
To fulfill the objective of a predictive tool for rotorcraft, comprehensive analysis (CA) needs to be capable of providing both accurate and time-efficient predictions of rotor air loads and structural loads. The more recent methodology based on comp...
This article describes the development and testing of a modified, semi-empirical ONERA dynamic stall model for an airfoil with a trailing edge flap—a “smart airfoil”—pitching at reduced frequencies up to 0.1. The Reynolds number is
Compressors are an essential component of aircraft engines. Their design and operation must be extremely reliable as engine safety and performance depend greatly on these elements. Axial compressors exhibit instabilities, such as surge or rotating st...
A dynamic stall model for tower shadow effects is developed for downwind turbines. Although Munduate’s model shows good agreement with a 1.0 m wind tunnel test model, two problems exist: (1) it does not express load increase before the entrance...
Computational simulations of three-dimensional flow around a NACA 0018 wing with an aspect ratio of
Prediction of the unsteady aerodynamic flow phenomenon on wind turbines is challenging and still subject to considerable uncertainty. Under yawed rotor conditions, the wind turbine blades are subjected to unsteady flow conditions as a result of the b...
There has been a resurgence of interest in the development of vertical axis wind turbines which have several inherent attributes that offer some advantages for offshore operations, particularly their scalability and low over-turning moments with bett...
Model-inspired signal processing approaches with an enhanced detectability of flow separation on thermographic images are presented. Flow separation causes performance loss, structural loads and increasing acoustic emissions on wind turbine rotor bla...
Operational safety and fuel efficiency are critical, yet often conflicting, objectives in modern civil get engine designs. Optimal efficiency operating conditions are typically close to unsafe regions, such as compressor stalls, which can cause sever...
The current research focuses on modeling the lift response due to dynamic (time-varying) “burst-type” actuation on a stalled airfoil. Here, the “burst-type” actuation refers to the synthetic jet (generated from the actuator) that is used for flow sep...
The maneuverability of the Sukhoi Su-30 at very high angles of attack (AoA) was remarkably appealing. Canard angle, in cooperation with aircraft wing, created a flow pattern whereby, in that position, the fighter still had as much lifting force as po...
This paper presents an unsteady flow analysis of a 3D wing with a morphing trailing edge flap (TEF) and a seamless side-edge transition between the morphed and static parts of a wing by introducing an unsteady parametrization method. First, a 3D stea...
Vertical Axis Wind Turbines (VAWTs) are characterized by complex and unsteady flow patterns resulting in considerable challenges for both numerical simulations and measurements describing the phenomena involved. In this study, a 3D Actuator Line Mode...
Cyclic blade motion during operation of vertical axis wind turbines (VAWTs) imposes challenges on the simulations models of the aerodynamics of VAWTs. A two-dimensional vortex model is validated against the new experimental data on a 12-kW straight-b...
Rotational augmentation and dynamic stall have been extensively investigated on horizontal axis wind turbines (HAWTs), but usually as separate topics. Although these two aerodynamic phenomena mainly determine the unsteady loads and rotor performance,...
In this paper, a thorough 2D unsteady computational fluid dynamic analysis was performed on a pitching airfoil to properly comprehend the dynamic stall and aerodynamic forces. The computational software ANSYS Fluent was used to solve the unsteady Rey...
This study aims to assess the dynamic stall of the wind turbine blade undergoing pitch oscillation (PO) and oscillating freestream (OF), respectively. Firstly, a thin-airfoil theoretical analysis was performed to differentiate between these two dynam...
This paper investigates the effect of the Dynamically Morphing Leading Edge (DMLE) on the flow structure and the behavior of dynamic stall vortices around a pitching UAS-S45 airfoil with the objective of controlling the dynamic stall. An unsteady par...
Stall events in axial compressor systems have been a limiting factor for efficiency of such systems and a source of safety concerns. The detection of the onset of stall, and in many cases the precursor of the onset of stall, have been of interest in...
The objective of this article is to characterize an aeroelastic system in terms of its dynamical behavior, which could be either chaotic or periodic before, during, and after achieving the flutter velocity. The aeroelastic system shown here is a wing...
Airfoils are subjected to the ‘dynamic stall’ phenomenon in significant pitch oscillations during the actual operation process of wind turbines. Dynamic stall will result in aerodynamic fatigue loads and further cause a discrepancy in the...
The onset of rotating stall and surge in compressors limits the operating range of aero-engines. Accurately predicting the key features during these events is critical in the engine design process. In this paper, a three-dimensional computational mod...
The unsteady flow characteristics and responses of an NACA 0012 airfoil fitted with a bio-inspired morphing trailing edge flap (TEF) at near-stall angles of attack (AoA) undergoing downward deflections are investigated at a Reynolds number of 0.62 ×...
Airfoil blades can experience a significant change of angle of attack during operation cycles, which may lead to static or dynamic stall in various applications. It is unclear how elements distributed at the leading edge would affect the aerodynamic...
Comprehensive rotorcraft simulation codes are the workhorses for designing and simulating helicopters and their rotors under steady and unsteady operating conditions. These codes are also used to predict helicopters’ limits as they approach rot...
A numerical method for generating dynamic stall using ANSYS Fluent and a user-defined function (UDF), with the complete script shared for reference, is introduced and tested. The study draws inspiration from bird flight, exploring dynamic stall as a...
Distortion, such as total pressure distortion, is a common phenomenon at the inlet of an axial compressor. Nonuniform inflow can greatly affect the aerodynamic performance and the stability of the compressor. In this paper, a sinusoidal distortion mo...
The design of wind turbines requires a deep insight into their complex aerodynamics, such as dynamic stall of a single airfoil and flow vortices. The calculation of the aerodynamic forces on the wind turbine blade at different angles of attack (AOAs)...
An experimental investigation regarding the dynamic stall of various swept wing models with pitching motion was performed to analyze the effect of sweep on the dynamic stall. The experiments were performed on a wing with a NACA0012 airfoil section wi...
Canard configuration on fighter planes is essential for regulating flow and the occurrence of vortex interactions on the main wing, one of which is to delay stall. Stall delays are useful when the aircraft is making maneuvering or short-landing. This...
Stall flow patterns occur frequently in pump turbines under off-design operating conditions. These flow patterns may cause intensive pressure pulsations, sudden increases in the hydraulic forces of the runner, or other adverse consequences, and are s...
Focusing on the identification of dynamic system stability, a hybrid neural network model is proposed in this research for the rotating stall phenomenon in an axial compressor. Based on the data fusion of the amplitude of the spatial mode, the nonlin...
A series of wind tunnel tests were performed to investigate the effect of turbulent inflows on the aerodynamic characteristics of variously modified trough incident leading-edge-protuberanced (LEP) wing configurations at various turbulence intensitie...
In this study, stall flutter onset prediction in a transonic compressor is carried out using the (uncoupled) energy method with Fourier transform. As the study is conducted computationally using computational fluid dynamics (CFD)-based simulations, t...
Rotational stall is an unstable flow phenomenon that reduces the performance of centrifugal pumps, usually occurring under partial load conditions. It causes instability in the flow resulting in intense vibrations and noise under certain flow conditi...
This study investigates a dual-stage axial-flow fan within a specific power plant context. Numerical simulations encompassing both steady-state and stall conditions were conducted utilizing the Reynolds-averaged Navier–Stokes (RANS) equations c...
This paper presents the effect of the tip shape of a wind turbine blade on aerodynamic forces, including the effects of separation, transition and stall. A National Renewable Energy Laboratory (NREL) Phase-VI wind turbine blade was used, in which the...
Wind turbine blades experience excessive load due to inaccuracies in the prediction of aerodynamic loads by conventional methods during design, leading to structural failure. The blade element momentum (BEM) method is possibly the oldest and best-kno...
Stall, a complex phenomenon related to flow separation, is difficult to be predicted accurately. The motivation of the present study is to propose an approach to improve the simulation accuracy of Reynolds Averaged Navier–Stokes equations (RANS...
Natural ventilation is the most common passive cooling system in livestock buildings. The aim of this research is to assess airflow distribution inside a free-stall barn for dairy cows by computational fluid dynamics (CFD) modelling and simulation. T...
The frequent appearance of sandy and dusty weather in Northwest China impacts the wind turbine. Meanwhile, the non-constant phenomena, dynamic stall speed during the wind turbine operation, will lead to large load fluctuations and unsafe operation. H...
The offshore implementation of vertical-axis wind turbines (VAWTs) presents a promising new paradigm for advancing marine wind energy utilization, owing to their omnidirectional wind acceptance, compact structural design, and potential for lower main...
Hydraulic torque converter is widely used in transmission units as it is able to provide variable speed and torque ratio, isolate vibration, and absorb shock. The pursuit of a highly packed power unit requires a high capacity/speed torque converter,...
This paper introduces the realization and wind tunnel testing of a novel variable camber wing equipped with compliant morphing trailing edges. Based on the aerodynamic shape and compliant mechanisms that were optimized in advance, a wind tunnel model...
We present simulations of turbulent detached flows using the commercial lattice Boltzmann solver XFlow (by Dassault Systemes). XFlow’s lattice Boltzmann formulation together with an efficient octree mesh generator reduce substantially the cost...
Passive vortex generators (VGs) are widely used to suppress the flow separation of wind turbine blades, and hence, to improve rotor performance. VGs have been extensively investigated on stationary airfoils; however, their influence on unsteady airfo...
This study aims to experimentally investigate the effects of parallel blade–vortex interaction (BVI) on the aerodynamic performances of an airfoil, in particular as a possible cause of blade stall, since similar effects have been observed in li...
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