Andırın, Mert Ali
Wind tunnels are designed to operate at low turbulence intensities, which makes it unfeasible to study the turbulent and gusty flows that are observed in nature and in engineering applications. To conduct such studies number of unconventional methods are adopted in wind tunnels, one of which is the use of active grids. Active grids consist of motor-driven rods which accommodate flaps and they are generally placed at the inlet of wind tunnel test sections. By regulating the motion of the agitator wings, flows with high turbulence intensities and tunable properties can be achieved or atmospheric boundary layers or gusts can be generated. Active grids are usually used to generate three-dimensional flow structures. There are also more primitive devices compared to active grids to generate gust flows which are called gust generators or 2-D active grids. In this context, the main objective of this thesis is to design an active grid on an open-loop suction-type wind tunnel and investigate the gust flow characteristics of the flow field of the near wake of the active grid using experiments. For this purpose, a more primitive design, a 2D two-wing active grid, a gust generator, is used to examine the gust produced by the flapping wing in the wake region of the gust generator. Firstly, the reduced frequency values of the vanes are changed at fixed pitching amplitude and secondly, the pitching amplitude is changed at fixed reduced frequency to investigate the gust characteristics of the flow. Unlike most of the literature, in this study, instead of using hot-wire anemometry measurements in the test section, particle image velocimetry measurements are taken in the wake of the agitator wings, which allows for exploring the physical relation between the wake structures and downstream flow profile. By the helpf of observing the whole flow field behind the gust vanes it is observed that even well-defined sinusoidal profiles of the transverse and stream-wise gust ratio in a period can be obtained using in-phase and out-of phase motion of the gust vanes, the one should be careful of the drawback of flow separation and number of coherent vortices shed into the wake.


Hassanein, Abdelrahman Hisham Ahmed Sabri; Perçin, Mustafa; Department of Aerospace Engineering (2023-1-18)
The study investigates the effect of two inflow conditions on the wake of a model wind turbine, namely, homogenous isotropic turbulence intensity and streamwise gust. For the effect of the freestream turbulence intensity, the wake of a porous disc with a comparable thrust coefficient was used to further highlight the differences in their wakes and decay characteristics. Results show that the wake of a wind turbine model has a faster decay rate than porous discs under both freestream turbulence intensities. ...
Design and Experimental Investigation of a Wind Tunnel Gust Generator
Yığılı, İmge; Perçin, Mustafa; Department of Aerospace Engineering (2022-9-01)
In the design, certification and operation cycles of air vehicles, wind turbines, etc., it is critically important to quantitatively demonstrate the capability of the vehicle to withstand any environmental and meteorological condition. Of several atmospheric conditions, one very common and significant one is the atmospheric gust. Therefore, capacity to generate gust in a fully controlled manner is of utmost importance. In wind tunnels, gust generation is done by means of gust generators, which are devices p...
Experimental Investigation of the Effects of Winglets on the Tip Vortex Behavior of a Model Horizontal Axis Wind Turbine Using Particle Image Velocimetry
Ostovan, Yasar; Akpolat, M. Tugrul; Uzol, Oğuz (2019-02-01)
This study presents an experimental investigation on the effects of winglets on the near wake flow around the tip region and on the tip vortex characteristics downstream of a 0.94 m diameter three-bladed horizontal axis wind turbine (HAWT) rotor. Phase-locked 2D particle image velocimetry (PIV) measurements are performed with and without winglets covering 120 deg of azimuthal progression of the rotor. The impact of using winglets on the flow field near the wake boundary as well as on the tip vortex characte...
Flutter characteristics of plate like structures
Dalmış, Mevlüt Burak; Yazıcıoğlu, Yiğit; Durak, Burak; Department of Mechanical Engineering (2014)
In this study, flutter characteristics of plate like structures in incompressible flow are investigated by comparing the results of commercial flutter analysis program ZAERO© with wind tunnel tests conducted in Ankara Wind Tunnel (ART). Firstly, a rectangular polycarbonate (PC) plate, 5x125x1000 mm in dimensions, is investigated. In this case, analysis and test results are in good agreement with each other. Second test item is a 1/10 scaled F-16 wing like PC plate. In this case, the plate is capable of carr...
Experimental investigation of the effects of different helicopter rotor tip geometries on aerodynamic performance and tip vortex characteristics
Uluocak, Sinem; Hazaveh, Hooman Amiri; Perçin, Mustafa; Akpolat, M Tuğrul; Uzol, Oğuz (Netherlands Association of Aeronautical Engineers; 2018-09-05)
In this study, the effects of different tip geometries (rectangular, anhedral, swept-tapered and swept-tapered-anhedral) on the rotor hover performance and tip vortex characteristics are investigated experimentally. A scaled rotor model set-up, instrumented with thrust and torque sensors, is used for aerodynamic performance measurements in hover and a two-dimensional (2D) particle image velocimetry (PIV) is used to obtain the tip vortex characteristics such as vortex trajectory, maximum tangential velocity,...
Citation Formats
M. A. Andırın, “GENERATION AND EXPERIMENTAL INVESTIGATIONS OF GUSTY FLOWS IN WIND TUNNELS,” M.S. - Master of Science, Middle East Technical University, 2022.