| Active flow control and heat transfer enhancement are the interested topics in the research areas of flow dynamics and engineering thermal physics. In the latest years, a synthetic jet with an important feature of zero-net-mass flux in nature has attracted many researchers'attentions. Experimental measurements and numerical simulation were performed in this paper to learn about the heat transfer characteristics of the synthetic jet driven by the piston actuator.In the numerical computations, the movement of the piston is modeled as a periodic sinusoid function. Based on Fluent- CFD commercial software, the user definition function (UDF) program was compiled to impose movement law on the underside of synthetic jet actuator, and the moving grids were used to simulate the boundary oscillation of computational region. The 3D unsteady computation coupling the actuator cavity region and the external region was realized to obtain the flow and temperature fields.A series of numerical studies were made to find out some influences of the actuator geometrical and actuating parameters on the synthetic jet. The results show that different frequency imported to the actuator has a great effect and it directly decide the capability of the synthetic jet flow field. Along with the increase of the frequency, the velocity of the synthetic jet was enhanced obviously.Studies on single synthetic jet and coupled synthetic jets for heat transfer applications were carried out, the heat transfer characteristics law of synthetic jets with different nozzle were obtained. At the same time, the interaction of coupled synthetic jets with the different method of array was analyzed. Along with the jet-to-surface spacing increment, the convective heat transfer coefficients at the target surface operated by the synthetic jet also take on up-down tendency, and the best jet-to-surface spacing is presence. Compare with the common jet impingement at the same impinging Reynolds number, the influence range of the synthetic jet is wider than the former, indicating that the synthetic jet introduces a stronger entrainment and more vigorous penetrating. For the coupled synthetic jets, according to analyzing the abundance of research data, the heat transfer effect of the coupled synthetic jets with the same sequence is better than that with the staggered sequence. The studies on the heat transfer characteristics of the synthetic jet together with the crossflow were also made and the interaction between the synthetic jet and the crossflow was analyzed. For one hand, the crossflow weakens the penetrating ability of the synthetic jet and induces the synthetic jet to deviate along crossflow direction. For the other hand, the mixing of the synthetic jet and the crossflow can strengthen the crossflow fluctuation. As a whole, the coupled heat transfer effect of the synthetic jet and crossflow is better than that of the separated synthetic jet or crossflow. |
