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Effect of orifice inner lip radius on synthetic jet efficiency
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Image of FIG. 1.
FIG. 1.

A schematic of the experiment test facility. Two loudspeakers are arranged in series and sealed in an aluminum enclosure to drive air through an interchangeable orifice (colored blue). Note that the interchangeable exit has a rounded inside edge and a sharp outside edge. Cooling to the speakers is supplied through an external source. A piezoresistive pressure sensor was threaded into the cavity wall.

Image of FIG. 2.
FIG. 2.

Radial velocity profiles for L 0/D = 15 and x/D = 0.1037 from the exit for several points in the non-dimensional time t/T, for (a) R/D = 0.3125 Case 25, and (b) R/D = 0 Case 54. Case numbers refer to those in Table II. Solid lines indicate the blowing phase (0 < t/T < 0.5) while dashed line indicate the suction phase (0.5 < t/T < 1).

Image of FIG. 3.
FIG. 3.

Definition of the control surface for the integration of velocity. Stream-wise flow occurs in the x-direction through surface 1.

Image of FIG. 4.
FIG. 4.

Volume flow rate as a function of time through surfaces 1 and 2 of the control surface (see Fig. 3) at progressive steps downstream of the exit for R/D = 0 and L 0/D = 15.

Image of FIG. 5.
FIG. 5.

Velocity averaged across the exit (solid lines) and cavity pressure (dashed lines) versus time for each orifice and L 0/D = 15.

Image of FIG. 6.
FIG. 6.

Acoustic power (a) and acoustic power normalized by U amp (b) as a function of orifice inner lip radius.

Image of FIG. 7.
FIG. 7.

Normalized acoustic power versus dimensionless displacement amplitude for each orifice investigated.

Image of FIG. 8.
FIG. 8.

Contours of vorticity for flow exiting the rounded edge of the orifice for R/D = 1.0 (a) and R/D = 0.5 (b) at the same instant in time. In both cases, L 0/D = 10. The contour increment is 0.12 s−1. While these data were acquired with the rounded exits facing upward to facilitate the optical PIV measurement, they are presented facing downward, which matches the configuration used in the remainder of the paper.

Image of FIG. 9.
FIG. 9.

Definition of component minor loss coefficients.

Image of FIG. 10.
FIG. 10.

The loss coefficient of the axisymmetric synthetic jet observed plotted against radius of curvature based on pressure and flow rate data and Eq. (7). The data labeled “Theoretical” are based on published minor loss coefficient data and Eq. (10).

Image of FIG. 11.
FIG. 11.

Momentum flux for two fixed locations downstream of the exit, x/D = 10 (solid marks), and x/D = 20 (open marks), plotted against displacement amplitude of each orifice studied. Momentum flux is normalized by the maximum outflow velocity squared averaged over the exit.


Generic image for table
Table I.

PIV measurement and processing details for near-field images.

Generic image for table
Table II.

Pressure and velocity harmonics from a DFT analysis and displacement amplitudes for each data set used in this study. The 2nd– 4th harmonics are presented as percentages of the fundamental of the velocity waveform, U amp. Pressure and velocity amplitudes are shown in units of pascals and meters per second, respectively. A case number is specified for organization.

Generic image for table
Table III.

Acoustic power per Eq. (4), compared to that of assuming sinusoidal waveforms (Eq. (5)), each in units of watts. The phase angle difference between the pressure and velocity waveforms is also shown in degrees. The case numbers are matched with those in Table II.

Generic image for table
Table IV.

Component minor loss estimates based on published data and the predicted total (cycle averaged) minor loss factor K total. Use of steady flow data from Ref. 20 is indicated by a *. Use of oscillatory flow data from Ref. 13 is indicated with **.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Effect of orifice inner lip radius on synthetic jet efficiency