Large Eddy Simulation of the Elliptic Jets in Film Cooling Controlled by Dielectric Barrier Discharge Plasma Actuators With an Improved Model

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Jianyang Yu ◽  
Zhao Wang ◽  
Fu Chen ◽  
Guojun Yan ◽  
Cong Wang
Keyword(s):  
Large Eddy Simulation ◽  
Dielectric Barrier Discharge ◽  
Film Cooling ◽  
Barrier Discharge ◽  
Plasma Actuator ◽  
Streamwise Vortices ◽  
Dbd Plasma ◽  
Dielectric Barrier ◽  
Eddy Simulation ◽  
Large Eddy

The dielectric barrier discharge (DBD) plasma actuator, in which electrodes are asymmetric arranged, has already demonstrated its ability in flow control. In the present work, the configuration of DBD plasma actuator defined as DBD-vortex generator (VGs), which can induce streamwise vortices, has been employed in the flow control of the inclined jet in crossflow. The coherent turbulent structures around the cooling hole are examined by the large eddy simulation (LES) method with the improved plasma model. The mechanism of coherent structure controlled by the DBD-VGs is also elucidated in the processes of parametric study with the actuation conditions. The calculation results show that the DBD-VGs provides us an effective approach to further enhance the performance of the film cooling. When it is applied into the flow, symmetrical streamwise vortices are induced to break down the coherent vortex structure, leading to more coolant gathered on the surface, especially at the lateral area of the coolant jet. What is more, an overall improvement of the film cooling performance can be obtained when the actuation strength is strong enough.

scholarly journals Coherent structures induced by dielectric barrier discharge plasma actuator

2017 ◽  
Vol 31 (32) ◽  
pp. 1850038 ◽  
Author(s):  
Xin Zhang ◽  
Huaxing Li ◽  
Kwing So Choi ◽  
Longfei Song
Keyword(s):  
Flow Control ◽  
Dielectric Barrier Discharge ◽  
Coherent Structures ◽  
High Speed ◽  
Barrier Discharge ◽  
Plasma Actuator ◽  
Dbd Plasma ◽  
Peak Voltage ◽  
Dielectric Barrier ◽  
Piv Measurement

The structures of a flow field induced by a plasma actuator were investigated experimentally in quiescent air using high-speed Particle Image Velocimetry (PIV) technology. The motivation behind was to figure out the flow control mechanism of the plasma technique. A symmetrical Dielectric Barrier Discharge (DBD) plasma actuator was mounted on the suction side of the SC (2)-0714 supercritical airfoil. The results demonstrated that the plasma jet had some coherent structures in the separated shear layer and these structures were linked to a dominant frequency of [Formula: see text] = 39 Hz when the peak-to-peak voltage of plasma actuator was 9.8 kV. The high speed PIV measurement of the induced airflow suggested that the plasma actuator could excite the flow instabilities which lead to production of the roll-up vortex. Analysis of transient results indicated that the roll-up vortices had the process of formation, movement, merging and breakdown. This could promote the entrainment effect of plasma actuator between the outside airflow and boundary layer flow, which is very important for flow control applications.

Large eddy simulation of saw tooth plasma actuator for improving film cooling efficiency

2017 ◽  
Vol 231 (5) ◽  
pp. 357-370 ◽  
Author(s):  
Guozhan Li ◽  
Jianyang Yu ◽  
Fu Chen ◽  
Huaping Liu ◽  
Yanping Song ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Flat Plate ◽  
Film Cooling ◽  
Three Dimensional ◽  
Plasma Actuator ◽  
Cooling Efficiency ◽  
Flow Topology ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Film Cooling Efficiency

This paper presents results on a saw tooth plasma actuator for the inducement of flow topology and the improvement of flat plate film cooling efficiency. A phenomenological plasma model is constructed to generate the three-dimensional plasma force vectors of the saw tooth plasma actuator. The dynamics of airflow induced by the saw tooth plasma actuator on a flat plate in quiescent air are numerically investigated. The results show that the saw tooth plasma actuator pushes the fluids in all three directions and induces a three-dimensional jet flow with counter rotating streamwise oriented vortices that propagate downstream. The flow field characteristics of both cylindrical hole with and without the saw tooth plasma actuator are studied by large eddy simulation, and a comparison is made. The saw tooth plasma actuator improves the cold jet adherent performance and promotes the spanwise spreading rate of the coolant. Meanwhile, the streamwise vortices induced by the saw tooth plasma actuator suppress the development of counter-rotating vortex pair, thus delaying the diffusion of coolant in the crossflow. Accordingly, the centerline cooling efficiency and the spanwise-averaged cooling efficiency are improved by 36% and 144% at x/ d = 15, compared with the baseline case without the saw tooth plasma actuator.

scholarly journals Investigation of a Dielectric Barrier Discharge Plasma Actuator to Control Turbulent Boundary Layer Separation

2020 ◽  
Vol 10 (6) ◽  
pp. 1911 ◽  
Author(s):  
Mahdi Hasan ◽  
Michael Atkinson
Keyword(s):  
Dielectric Barrier Discharge ◽  
Barrier Discharge ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Separated Flow ◽  
Boundary Layer Separation ◽  
Plasma Actuator ◽  
Dbd Plasma ◽  
Dielectric Barrier ◽  
Baseline Case

A numerical investigation was carried out to explore the effects of a dielectric barrier discharge (DBD) plasma actuator on a three-dimensional incompressible, separated flow. The test article selected for the simulations was the National Aeronautical and Space Administration (NASA) wall-mounted hump model. The simulations were run at a Reynolds number of 936,000, based on hump chord length, and a freestream Mach number of 0.1. Hybrid partially averaged Navier–Stokes/large-eddy simulations (PANS/LES) were completed using CALC-LES, a well-validated computational fluid dynamics (CFD) code, developed by Chalmers University of Technology. The baseline code was modified to simulate the effects of the actuator, which were modeled as source terms in the momentum equation and were assumed to be steady and constant in the span-wise direction. The numerical simulations were carried out for a baseline (no control) case and five plasma control cases. To optimize the performance of the actuator, the variation of actuator location and voltage frequency was investigated. For the baseline case, a comparison of time-averaged skin friction, the coefficient of pressure, and velocity profiles was made of the available experimental results. The results of the baseline case showed good agreement for a hybrid turbulence model, thus strengthening the solver’s ability to predict a three-dimensional separated flow with reasonable accuracy. The results with the plasma actuator turned on showed improved flow characteristics compared to the baseline simulations by reducing the region of separated flow. The actuator placed just downstream of the separation point at an operational frequency of 5kHz completely eliminated the separated flow for our test conditions.

scholarly journals The starting vortex in quiescent air induced by dielectric-barrier-discharge plasma

2012 ◽  
Vol 703 ◽  
pp. 192-203 ◽  
Author(s):  
Richard D. Whalley ◽  
Kwing-So Choi
Keyword(s):  
Dielectric Barrier Discharge ◽  
Barrier Discharge ◽  
Maximum Velocity ◽  
Plasma Actuator ◽  
Dbd Plasma ◽  
Dielectric Barrier ◽  
Image Velocimetry ◽  
Barrier Discharge Plasma ◽  
Self Similar ◽  
Surrounding Fluid

AbstractThe flow field around an asymmetric dielectric-barrier-discharge (DBD) plasma actuator in quiescent air is studied using particle image velocimetry (PIV) and smoke-flow visualization. On initiation of DBD plasma a starting vortex is created, which rolls up to form a coherent structure. The starting vortex becomes self-similar when the maximum velocity induced by the DBD plasma actuator reaches a steady state. Here, the plasma jet momentum increases linearly with time, suggesting that the DBD plasma actuator entrains and accelerates the surrounding fluid with a constant force. The wall-parallel and wall-normal distances of the vortex core are observed to scale with ${t}^{2/ 3} $ as it travels at $3{1}^{\circ } $ to the wall. The velocity of the starting vortex is found to scale with ${t}^{- 1/ 3} $, while the circulation induced by the plasma actuator scales with ${t}^{1/ 3} $.

scholarly journals Large Eddy Simulation of Film Cooling Involving Compound Angle Holes: Comparative Study of LES and RANS

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 198
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Orientation Angle ◽  
Turbulence Models ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle

A large eddy simulation (LES) was performed for film cooling in the gas turbine blade involving spanwise injection angles (orientation angles). For a streamwise coolant injection angle (inclination angle) of 35°, the effects of the orientation angle were compared considering a simple angle of 0° and 30°. Two ratios of the coolant to main flow mass flux (blowing ratio) of 0.5 and 1.0 were considered and the experimental conditions of Jung and Lee (2000) were adopted for the geometry and flow conditions. Moreover, a Reynolds averaged Navier–Stokes simulation (RANS) was performed to understand the characteristics of the turbulence models compared to those in the LES and experiments. In the RANS, three turbulence models were compared, namely, the realizable k-ε, k-ω shear stress transport, and Reynolds stress models. The temperature field and flow fields predicted through the RANS were similar to those obtained through the experiment and LES. Nevertheless, at a simple angle, the point at which the counter-rotating vortex pair (CRVP) collided on the wall and rose was different from that in the experiment and LES. Under the compound angle, the point at which the CRVP changed to a single vortex was different from that in the LES. The adiabatic film cooling effectiveness could not be accurately determined through the RANS but was well reflected by the LES, even under the compound angle. The reattachment of the injectant at a blowing ratio of 1.0 was better predicted by the RANS at the compound angle than at the simple angle. The temperature fluctuation was predicted to decrease slightly when the injectant was supplied at a compound angle.

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