Comparison of synthetic jet actuators based on sharp-edged and round-edged nozzles

Axisymmetric synthetic jet actuators based on a loudspeaker and on two types of flanged nozzles were tested and compared experimentally. The first type of the nozzle was a sharp-edged circular hole. The second one had a special design with fillets at inner and outer nozzle exit and with a small step in the middle of the nozzle. The function of the step was to prevent the flow reattachment during the extrusion stroke. The actuators with the two types of nozzles were operated at resonance and were compared first qualitatively using a simple phase locked flow visualization. Then the hot-wire anemometer was used to measure velocity distributions along nozzle axis and velocity profiles at the nozzle exit. Comparison of the nozzles was based on evaluation of the characteristic velocity and integral quantities (volumetric, momentum, and kinetic energy fluxes). It was found out that these quantities, which were evaluated at the nozzle exit, differ substantially for both nozzles. On the other hand the velocity flow field in farther distances from the nozzle exit area did not exhibit such prominent differences

Impinging Synthetic Jet - Experiment

The paper deals with processing of an experimental data relating to an impinging synthetic jet. Impinging synthetic jet means a pulsating jet, spreading onto a wall (in this case naphthalene wall). The aim of the experiment is a quantification of mass transfer on the wall and a prediction of heat transfer by means of the heat/mass transfer analogy

Velocity Profiles of Synthetized and Continuum Jets

The synthetic jet and continuous jet velocity profiles were measured and compared. The report focuses especially the root mean square differences derived from the measured data. The formation criterion of the synthetic jet were also determined and compared with literature

Analysis of the synthetic jet at the actuator output

The paper focuses on a pulsatile axisymmetric flow in an outlet orifice of a zero-net-mass-flux actuator of a synthetic air jet. A simplified task (pulsatile pipe flow) is studied theoretically. Velocity profiles have been measured using hot-wire anemometry; the approximation of the experimental data is based on the theoretical solution. The results improve our knowledge of synthetic jets and provide data for their advanced numerical simulation.The paper focuses on a pulsatile axisymmetric flow in an outlet orifice of a zero-net-mass-flux actuator of a synthetic air jet. A simplified task (pulsatile pipe flow) is studied theoretically. Velocity profiles have been measured using hot-wire anemometry; the approximation of the experimental data is based on the theoretical solution. The results improve our knowledge of synthetic jets and provide data for their advanced numerical simulation

Comparison of synthetic jet actuators based on sharp-edged and round-edged nozzles

Axisymmetric synthetic jet actuators based on a loudspeaker and on two types of flanged nozzles were tested and compared experimentally. The first type of the nozzle was a sharp-edged circular hole. The second one had a special design with fillets at inner and outer nozzle exit and with a small step in the middle of the nozzle. The function of the step was to prevent the flow reattachment during the extrusion stroke. The actuators with the two types of nozzles were operated at resonance and were compared first qualitatively using a simple phase locked flow visualization. Then the hot-wire anemometer was used to measure velocity distributions along nozzle axis and velocity profiles at the nozzle exit. Comparison of the nozzles was based on evaluation of the characteristic velocity and integral quantities (volumetric, momentum, and kinetic energy fluxes). It was found out that these quantities, which were evaluated at the nozzle exit, differ substantially for both nozzles. On the other hand the velocity flow field in farther distances from the nozzle exit area did not exhibit such prominent differences

Maximization of integral outlet quantities of an axisymmetric synthetic jet actuator based on a loudspeaker

The goal of this paper is to find an optimal nozzle size of an axisymmetric synthetic jet actuator based on a loudspeaker. The desirable maximized output quantities are: volumetric flow, momentum flux, and kinetic energy flux. To evaluate these quantities velocity profiles were measured using a hot-wire probe at the actuator nozzle exit. Six different nozzle diameters and three supplied real power levels were tested to find the maxima of the quantities. The actuator operated always at resonance during experiments. It was found out that the momentum flux and the kinetic energy flux reach distinguishable local maxima at particular diameters of the nozzle. Besides, the maxima of the particular quantities do not coincide and the best nozzle size slightly increases with the supplied real power to the actuator

Flow control in axial fan inlet guide vanes by synthetic jets

Tested high pressure axial flow fan with hub/tip ratio of 0.70 and external diameter of 600 mm consisted of inlet guide vanes (IGV), rotor and stator blade rows. Fan peripheral velocity was 47 m/s. Air volume flow rate was changed by turning of rear part of the inlet guide vanes. At turning of 20 deg the flow was separated on the IGV profiles. The synthetic jets were introduced through radial holes in machine casing in the location before flow separation origin. Synthetic jet actuator was designed with the use of a speaker by UT AVCR. Its membrane had diameter of 63 mm. Excitation frequency was chosen in the range of 500 Hz – 700 Hz. Synthetic jets favourably influenced separated flow on the vane profiles in the distance of (5 – 12) mm from the casing surface. The reduction of flow separation area caused in the region near the casing the decrease of the profile loss coefficient approximately by 20%

Flow control in axial fan inlet guide vanes by synthetic jets

Tested high pressure axial flow fan with hub/tip ratio of 0.70 and external diameter of 600 mm consisted of inlet guide vanes (IGV), rotor and stator blade rows. Fan peripheral velocity was 47 m/s. Air volume flow rate was changed by turning of rear part of the inlet guide vanes. At turning of 20 deg the flow was separated on the IGV profiles. The synthetic jets were introduced through radial holes in machine casing in the location before flow separation origin. Synthetic jet actuator was designed with the use of a speaker by UT AVCR. Its membrane had diameter of 63 mm. Excitation frequency was chosen in the range of 500 Hz – 700 Hz. Synthetic jets favourably influenced separated flow on the vane profiles in the distance of (5 – 12) mm from the casing surface. The reduction of flow separation area caused in the region near the casing the decrease of the profile loss coefficient approximately by 20%