In this work, a pair of sweeping jet actuators is installed underneath the endplate of a slanted-... more In this work, a pair of sweeping jet actuators is installed underneath the endplate of a slanted-base cylinder at ReD = 200 000. The sweeping jets form a 30° inclined angle with the endplate and are placed at different streamwise locations, and their strength is varied with a momentum coefficient, C μ, ranging from 3.8 × 10−3 to 6.0 × 10−2. For all the cases examined in this paper, it is found that while a higher C μ produces a higher drag reduction, the flow control energy efficiency decreases rapidly as C μ increases. A net energy saving is achieved when C μ is less than 0.01, and the highest energy efficiency obtained in the present study is 2.8% when the actuator pair is placed at the most upstream location tested. The drag reduction is attributed to the reaction force and an increase in the surface pressure force acting on the endplate produced by the jet pair. The contribution from the former constitutes an increasing proportion of the total drag reduction as C μ increases lea...
In this paper, a sweeping jet is applied to control the afterbody vortices behind a slanted-base ... more In this paper, a sweeping jet is applied to control the afterbody vortices behind a slanted-base cylinder for the first time at Reynolds numbers from 87 000 to 200 000. The control effects are examined using stereo particle image velocimetry and surface pressure measurements with the jet momentum coefficient (Cμ) varying from 0.056 to 0.893. It is found that the sweeping jet results in increasingly diffused and larger afterbody vortices as Cμ increases. While an increase in Cμ up to 0.167 leads to a reduction in the circulation of the afterbody vortices and their earlier detachment from the slanted base, a further increase in Cμ introduces additional vorticity into the afterbody vortices leading to higher vortex strength, which could be detrimental to the control purpose. The interaction mechanism of sweeping jets lies in that turbulence is injected into the afterbody vortices as the sweeping jet intersects with these vortices and this subsequently causes diffusion of velocity gradi...
In this study, a method called three-dimensional meshed infrared thermography (3D MIT) was develo... more In this study, a method called three-dimensional meshed infrared thermography (3D MIT) was developed to visualize the volumetric temperature of air using an infrared camera. The main operating principle of the proposed method is to image the spheres using an infrared camera and processing the images with computer software to obtain the volumetric temperature distribution. For the correct implementation of the method, an equation is proposed to
A method for volumetric visualization of temperature distribution: three-dimensional meshed infrared thermography
Experiments in Fluids, 2019
In this study, a method called three-dimensional meshed infrared thermography (3D MIT) was develo... more In this study, a method called three-dimensional meshed infrared thermography (3D MIT) was developed to visualize the volumetric temperature of air using an infrared camera. The main operating principle of the proposed method is to image the spheres using an infrared camera and processing the images with computer software to obtain the volumetric temperature distribution. For the correct implementation of the method, an equation is proposed to determine the distance between the thermal target and the measurement target placed in the flow to be examined. The proposed method was compared with conventional measurement screen methods, namely those using a plane target and a high-porosity target, via particle image velocimetry (PIV) in terms of flow effects. The temperature measurement capability of the proposed method is presented in comparison with the results of thermocouple and conventional measurement screen-based measurements recorded using a jet flow. In addition, the volumetric temperature isosurfaces obtained via the 3D MIT method of a jet flow were compared with the volumetric velocity isosurfaces obtained via the PIV method in terms of the flow structure.
Experimental visualization of the flow characteristics of the outflow of a split air conditioner indoor unit by meshed infrared thermography and stereo particle image velocimetry
Experimental Thermal and Fluid Science, 2013
ABSTRACT Three-dimensional (3D) flow structures due to the interaction between the device edges, ... more ABSTRACT Three-dimensional (3D) flow structures due to the interaction between the device edges, fan casing and cross flow fan (CFF) in the rectangular jet at the outflow of a split air conditioner (SAC) indoor unit were investigated by the stereo particle image velocimetry (SPIV) method. In addition, a novel application of infrared thermography called meshed infrared thermography (MIT), used to determine and visualize the temperature profile in an air flow field, was introduced for the first time and used to investigate the temperature distribution at the outflow section of the SAC indoor unit. The results of measurements that were made at different positions on the device were used to prepare three-dimensional reconstructions of the rectangular jet flow and temperature distribution at the outlet section.
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Papers by ozgun ozer
volumetric temperature of air using an infrared camera. The main operating principle of the proposed method is to image the
spheres using an infrared camera and processing the images with computer software to obtain the volumetric temperature
distribution. For the correct implementation of the method, an equation is proposed to determine the distance between the
thermal target and the measurement target placed in the flow to be examined. The proposed method was compared with
conventional measurement screen methods, namely those using a plane target and a high-porosity target, via particle image
velocimetry (PIV) in terms of flow effects. The temperature measurement capability of the proposed method is presented in
comparison with the results of thermocouple and conventional measurement screen-based measurements recorded using a
jet flow. In addition, the volumetric temperature isosurfaces obtained via the 3D MIT method of a jet flow were compared
with the volumetric velocity isosurfaces obtained via the PIV method in terms of the flow structure.