The effect of initial Re, by altering the nozzle diameter (Dj), on the far field development of t...

1. Material

1.1. A hexagonal mesh was built and multiple o-grids were applied to refine the part near the jet inlet.

1.2. The kiln is a stationary cylinder with a diameter Dkiln = 0.1 m.

1.3. A jet inlet with a diameter Dj = 1.5 mm.

1.4. Three grids with different refinement levels were prepared.

2. Methods

2.1. To study the effect of initial Re, four cases were simulated with Dj = 0.0012, 0.0015, 0.0018, and 0.0021 m corresponding to Re = 37240, 29792, 24827, and 21280.

2.2. With the commercial meshing software ANSYS 16.0 ICEMCFD.

3. Results

3.1. The instantaneous streamwise velocity fields (Figure 3) at the last time step show the major difference brought by altering the nozzle diameter Dj.

3.2. The high-velocity region where U/Ub > 5 can represent the jet length, and it increases with Re.

3.3. On the contrary, the length of the region where 1 < U/Ub < 5 significantly decreases with Re, indicating that the velocity decays faster in higher Re cases.

3.4. This low-velocity region orients the jet by pushing it downwards, restraining the jet from spreading upwards.

4. Conclusion

4.1. The standard k-ε model gave the closest prediction to the measurements in previous work.

4.2. The prediction of the spreading rate S of the streamwise velocity is quite accurate with an error of about 3%.

4.3. There is an overprediction of the centerline decay term B of the velocity by about 45% and of the spreading rate SΦ of the passive scalar by about 20%.

4.4. The model is capable of predicting a Re dependency of the jet development as the jet with higher initial Re is longer.