2014 年 80 巻 820 号 p. FE0359
The mean flowfield of a linear array of multiple rectangular jets run through transversely with a normal two-dimensional jet, has been investigated, experimentally. The purpose 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 jet promoted strongly the inward secondary flows 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 (≡39m/s) was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (3.1 μm in diameter, 0.6 mm effective length) 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 inward secondary flows on both the y and z axes in the upstream region were promoted by a two-dimensional jet which run through transversely to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet became 2.5 times longer than that of the supposed multiple rectangular jets, and the half-velocity width on the multiple rectangular jet axes of the present jet was suppressed 50% shorter compared with that of the supposed multiple rectangular jets.
