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Numerical Simulation of DBD Plasma Actuator and Optimization with Differential Evolution Algorithm for Separation Control

Jafari, Sajjad | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49902 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Mazaheri, Karim
  7. Abstract:
  8. In the current study, first, the presence history of dielectric barrier discharge (DBD) plasma actuator in flow control usages has been investigated. After recognizing the importance of plasma actuator in this branch of engineering, this active controller was modeled relying on computational fluid dynamics (CFD) knowledge to control flow separation. In order to model this actuator, physics based model called spilt-potential model and modifications done to improve it, were used. Using this model and solving two elliptic equations, electrical field and plasma charge density distribution are obtained in range of solution domain and body force from plasma actuator modeling in all computational grid cells, as the source term, are added to the momentum equations solvable in the fluent software. In order to investigate the accuracy of the performed modeling, first of all, the effect of plasma actuator on the quiescent air in the vicinity of the flat plate was simulated. As was expected, the presence of plasma actuator in the quiescent air leads to ionization of its adjacent air and therefore creates a jet on the wall. The comparison of the obtained results of this modeling with laboratory measurements under similar conditions indicates the appropriate accuracy of the performed modeling of actuator. In the next step, the ability of the performed modeling of plasma actuator in controlling flow separation was investigated by putting it on the attack edge of NACA0015 airfoil at 140,000Reynolds number.As the position of plasma actuator has a significant effect on its ability to flow separation control and the number of geometrical and physical input parameters is high, it is not possible to predict the effect and the result of selecting a set of values for these parameters before solving the problem completely. To put it differently, selecting a set of these parameters with the aim to reach optimum aerodynamic conditions is not possible. Therefore, to reach optimum aerodynamic conditions for NACA0015 airfoil using flow control capability of plasma actuator, differential evolution optimization algorithm was used in the following. The cost function used for optimization has been defined as .This cost function includes the aim of the maximum increase of lift to drag force ratio by spending the minimum power and energy. Optimization has been done at two attack angles of 15 and 12 degree at 150,000 Reynolds. Results obtained by this optimization indicate a 300 and 250 percent increase in the lift to drag ratio in attack angles of 15 and 12 degree, respectively. The obtained optimum place is also located at a distance of 2 and 5 percent of chord length from attack edge. At the end, at high angles of attack and after stall of the airfoil at 200000 Reynolds number ,the effect of operating voltage, frequency and position of plasma actuator were investigated as the most important and effective parameters of plasma actuator. Results obtained at this part also show that by increasing angle of attack and increasing separation region size behind the airfoil, the appropriate situation to install plasma actuator gets closer to the attack edge. Increasing working voltage and frequency have approximately similar effects on increasing the maximum density of plasma charge distribution and plasma expansion length, and therefore, improving airfoil aerodynamic coefficients
  9. Keywords:
  10. Optimization ; Separation Control ; Differential Evolution Algorithm ; Dielectric-Barrier Discharge (DBD)Plasma Actuator ; Numerical Modeling

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