Turbulent rectangular jets

Abstract

Greek iii List of symbols iv List of figures v List of tables vi 3. Review 3.1 Literature review 4. Experimentation 4.1 Experimental Set-up 4.1.1 Nozzle exit 4.1.2 Settling chamber 4.1.3 Blower 4.1.4 Endplates and sidewalls 4.2 Hot wire anemometry 4.2.1 Constant temperature hot-wire anemometry (CTA) 4.2.1.1 Working principle 4.2.1.2 Noise 4.2.1.3 Advantages of hot wire anemometry technique 4.2.1.4 Disadvantages of hot wire anemometry technique 4.2.1.5 Selection of hot wire sensors 4.2.1.6 Calibration of hot wire anemometer 4.2.1.7 Measuring velocity components 4.2.1.8 Specifications of the hot wire anemometry system and experimental conditions of the present investigation 4.2.1.9 Experimental uncertainty 4.3 Experimental procedure 1. jet with no endplate and no sidewalls, NENS, 2. jet with endplate and no endplate, WENS, 3. jet without endplate and with sidewalls, NEWS and 4. jet with endplate and with sidewalls, WEWS,have been measured, with x-sensor hot wire anemometry, up to an axial distance of 35 D under identical inlet conditions. Centreline measurements for the four configurations have been collected for three Reynolds number, Re D =10,000, 20,000 and 30,000. For Re D =20,000 measurements in the transverse direction were collected at 13 different downstream locations in the range of x= (0, 1, 2, 2.5, 3, 4, 5, 10, 15, 20, 25, 30 and 35) nozzle widths.The jet with no endplate and no sidewalls (NENS) and the jet with endplate and no sidewalls (WENS) produce nearly similar mean and turbulent velocity profiles indicating insignificant effect of the endplates on their development in the absence of the sidewalls. At Re=20,000, larger mean streamwise velocity values were observed at the edges of the jets (NEWS or WEWS) at distances from nozzle in the range of x/D=3-30 whereas the presence of the endplate has an insignificant effect.The presence or absence of sidewalls is also key factor determining the distributions of the lateral mean velocity component. The presence of sidewalls is associated with lower outward velocities within the edges of the jets and higher inward ones outside the edges. The absence of sidewalls makes the presence of the endplate insignificant and the lateral velocity attains outside the edges low negative values of almost the same level in both cases (NENS, WENS) The presence of an endplate has again some significance only when the sidewalls are present alleviating their effect.