Active Control of Flow around NACA 0015 Airfoil by Using DBD Plasma Actuator

7th International Conference on Experimental Fluid Mechanics (EFM) -- NOV 20-23, 2012 -- Tech Univ Liberec (TU Liberec), Hradec Kralove, CZECH REPUBLICWOS: 000319932200008In this study, effect of plasma actuator on a flat plate and manipulation of flow separation on NACA0015 airfoil with plasma actuator at low Reynolds numbers were experimentally investigated. In the first section of the study, plasma actuator which consists of positive and grounded electrode couple and dielectric layer, located on a flat plate was actuated at different frequencies and peak to peak voltages in range of 3-5 kHz and 6-12 kV respectively. The induced air flow velocity on the surface of flat plate was measured by pitot tube at different locations behind the actuator. The influence of dielectric thickness and unsteady actuation with duty cycle was also examined. In the second section, the effect of plasma actuator on NACA0015 airfoil was studied at Reynolds number 15000 and 30000. Four plasma actuators were placed at x/C = 0.1, 0.3, 0.5 and 0.9, and different electrode combinations were activated by sinusoidal signal. Flow visualizations were done when the attack angles were 0 degrees, 5 degrees, 10 degrees, 15 degrees and 20 degrees. The results indicate that up to the 15 degrees attack angle, the separated flow was reattached by plasma actuator at 12kV peak to peak voltage and 4 kHz frequency. However, 12 kV(pp) voltage was insufficient to reattach the flow at 20 angle of attack. The separated flow could be reattached by increasing the voltage up to 13 kV. Lift coefficient was also increased by the manipulated flow over the airfoil. Results showed that even high attack angles, the actuators can control the flow separation and prevent the airfoil from stall at low Reynolds numbers.Dantec Dynam GmbH, Kamax Holding, LENAM s r o, MIT s r o, SPECION s r oScientific and Technological Research Council of Turkey (TUBITAK) [110M056]The authors would like to acknowledge the financial support of this work by the Scientific and Technological Research Council of Turkey (TUBITAK) under the Contract Number of 110M056

The Passive Flow Control Around a Truck-Trailer Model

In this study the aerodynamic characteristics of 1/32 scale truck and trailer model were examined in a wind tunnel. The acting drag force to model truck and trailer combination is calculated and aerodynamic drag coefficient is determined. The wind tunnel tests were carried out in the range of 159 000 - 453 000 Reynolds numbers. In order to improve the aerodynamics structure of truck- trailer, one spoiler, one passive air channel and three different redirector is produced in three dimensional printer. These aerodynamic parts respectively added to base truck-trailer model and obtaining aerodynamic improvement rates compared. According to wind tunnel test results, the aerodynamic improvement rates are respectively 14.78%, 18.06%, 23.15%and 20.70%. The lowest drag coefficient was determined as 0,584on model-3 of truck-trailer modelIn this study the aerodynamic characteristics of 1/32 scale truck and trailer model were examined in a wind tunnel. The acting drag force to model truck and trailer combination is calculated and aerodynamic drag coefficient is determined. The wind tunnel tests were carried out in the range of 159 000 - 453 000 Reynolds numbers. In order to improve the aerodynamics structure of truck- trailer, one spoiler, one passive air channel and three different redirector is produced in three dimensional printer. These aerodynamic parts respectively added to base truck-trailer model and obtaining aerodynamic improvement rates compared. According to wind tunnel test results, the aerodynamic improvement rates are respectively 14.78%, 18.06%, 23.15%and 20.70%. The lowest drag coefficient was determined as 0,584on model-3 of truck-trailer mode

The Numerical Investigation of Aerodynamic Structures of Truck and Trailer Combinations

In this study, aerodynamic structures of the heavy vehicle consisting of truck and trailer was investigated with computational fluid mechanics method. The force measurement were performed on the model car and aerodynamic drag coefficient (CD) were determined numerically in 4 different speeds on the Fluent® program. Numerical analysis of flow were made on the 59 000 - 844 000 Reynolds number. The effect of trailer additional to truck was determined to aerodynamic drag coefficient. The friction and pressure induced distributions were determined of total aerodynamic resistance. The images of flow structure were obtained around the truck trailer. The zones that was forming aerodynamic resistance were determinedIn this study, aerodynamic structures of the heavy vehicle consisting of truck and trailer was investigated with computational fluid mechanics method. The force measurement were performed on the model car and aerodynamic drag coefficient (CD) were determined numerically in 4 different speeds on the Fluent® program. Numerical analysis of flow were made on the 59 000 - 844 000 Reynolds number. The effect of trailer additional to truck was determined to aerodynamic drag coefficient. The friction and pressure induced distributions were determined of total aerodynamic resistance. The images of flow structure were obtained around the truck trailer. The zones that was forming aerodynamic resistance were determine

A New Method to Represent Speech Signals Via Predefined Signature and Envelope Sequences

A novel systematic procedure referred to as “SYMPES” to model speech signals is introduced. The structure of SYMPES is based on the creation of the so-called predefined “signature S={SR(n)} and envelope E={EK(n)}” sets. These sets are speaker and language independent. Once the speech signals are divided into frames with selected lengths, then each frame sequence Xi(n) is reconstructed by means of the mathematical form Xi(n)=CiEK(n)SR(n). In this representation, Ci is called the gain factor, SR(n) and EK(n) are properly assigned from the predefined signature and envelope sets, respectively. Examples are given to exhibit the implementation of SYMPES. It is shown that for the same compression ratio or better, SYMPES yields considerably better speech quality over the commercially available coders such as G.726 (ADPCM) at 16 kbps and voice excited LPC-10E (FS1015) at 2.4 kbps