A comprehensive study on the effects of orifice diameter on power consumption and diagram vibration of an acoustic actuator and impingement heat transfer of a synthetic jet
This study focuses on the synthetic jet actuator,composed of a specific acoustic speaker and an annular actuator cavity.A series of experiments have been conducted to explore the overall impacts of orifice diameter(dc ranging from 2 to 10 mm)on various factors,including the input power,diagram vibration of the acoustic actuator,and the flow field and impingement heat transfer of the synthetic jet.We employed a laser displacement sensor,particle image velocimetry,and an infrared thermal imager.Our results indicate that the orifice diameter significantly influences synthetic jet performance.When the input power is constant,the vibration amplitude of the vibrating diaphragm in the acoustic actuator is attenuated with respect to that in the pure acoustic speaker,especially for small-diameter orifices at high excitation frequencies.We found that a synthetic jet generated from a 6 mm orifice produces the highest ejection velocity,shearing vorticity,and impingement heat transfer coefficient.Under the same vibration amplitude of the vibrating diaphragm,a synthetic jet generated from a small-diameter orifice possesses a stronger flow and heat transfer capacity than one created from a large-diameter orifice.However,this comes with a trade-off of requiring more input power to the acoustic actuator,especially at high excitation frequencies.The characteristic velocity of the synthetic jet increased linearly with the excitation frequency.Conversely,the input power of the acoustic actuator exhibited a non-monotonous change with the excitation frequency.With respect to the pure acoustic speaker,the excitation frequency corresponding to the minimum input power shifted toward the lower end of the acoustic actuator attached to a small-diameter orifice cavity.Considering comprehensive factors such as the power consumption of the acoustic actuator and flow and heat transfer characteristics of the synthetic jet,we recommend an excitation frequency f of 250 Hz,an orifice diameter dc of 6 mm,and a dimensionless impinging distance H/dc of 6 for the current synthetic jet.
synthetic jetacoustic actuatororifice diameter effectpower consumptiondiagram vibrationimpingement heat transfer
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