Abstract
The mean flowfield of a linear array of multiple rectangular jets run through transversely with a two-dimensional jet, has been investigated, experimentally. The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The reason of the adoption of this nozzle exit shape was caused by the reports of authors in which the cruciform nozzle promoted the inward secondary flows strongly on both the two jet axes. Aspect ratio of the rectangular nozzle used in this experiment was 12.5. Reynolds number based on the nozzle width d and the exit mean velocity Ue (≅ 39 m / s) was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (lh = 3.1 μm in diameter, dh = 0.6 mm effective length : dh / lh = 194) operated by the linearized constant temperature anemometers (DANTEC), and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 60 seconds. From this experiment, it was revealed that the magnitude of the inward secondary flows on both the y and z axes in the upstream region of the present jet was promoted by a two-dimensional jet which run through transversely perpendicular to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet extended 2.3 times longer than that of the multiple rectangular jets, and the half-velocity width on the rectangular jet axis of the present jet was suppressed 41% shorter compared with that of the multiple rectangular jets.
Highlights
The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet.Many examples of multiple rectangular jets in industrial situations were found in the combustion equipment [1], the high lift devices [2] and the high thrust ejectors [3], they were applied to the rapid mixing and the operation of the mixing rate
It was revealed that the magnitude of the inward secondary flows on both the y and z axes in the upstream region of the present jet was promoted by a twodimensional jet which run through transversely perpendicular to the multiple rectangular jets, the potential core length on the x axis of the present jet extended 2.3 times longer than that of the multiple rectangular jets, and the half-velocity width on the rectangular jet axis of the present jet was suppressed 41% shorter compared with that of the multiple rectangular jets
The streamwise variation of the longitudinal mean velocity profiles on both the y and z axes of the present 3-D jet (Black) are shown in figure 3, and the results of the multiple rectangular jets (Red) by authors are shown for comparison in the region of 5 ≤ x / d ≤ 50
Summary
The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The present study adapted a new method of running through transversely with a two-dimensional jet to change the property of the multiple rectangular jets This adaption was obtained from the reports by authors [8, 9, 10] of which the cruciform shape nozzle jet produced the inward secondary flow toward the jet centre region on both nozzle axes. The object of the present study is to delay the decreasing rate of the velocity scale near the jet centre region and to repress the developing rate of the half velocity width of the multiple rectangular jets field using a two-dimensional jet which runs through transversely perpendicular to the multiple rectangular jets.
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