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ABSTRACT
Three-dimensional turbulent offset jets were investigated using a particle image velocimetry technique. Detailed measurements were performed for offset height ratios of 0, 2 and 4. The presence of backflow influenced the distribution of the mean velocity and Reynolds stresses. A two-point correlation analysis was used to investigate the spatial distribution of large-scale structures within the inner shear layer of the flow domain. The results revealed that large-scale structures dominate the inner layer of the self-similarity region. Proper orthogonal decomposition was performed on the fluctuating velocity field within the symmetry and lateral planes using the snapshot approach. Results from the reconstructed field provided insight into the contributions of the most energetic structures to the turbulence statistics. The energetic structures contributed more to the Reynolds shear stress and streamwise turbulence intensity, while contributing less to the wall-normal turbulence intensity.
Acknowledgement
Support for this work by the Natural Sciences and Engineering Research Council of Canada and Manitoba Hydro is gratefully acknowledged.
Notations
| bo | = | nozzle height (mm) |
| b | = | nozzle width (mm) |
| d | = | nozzle exit diameter (mm) |
| = | Froude number (–) | |
| g | = | acceleration due to gravity (m s–2) |
| h | = | offset height (mm) |
| Le | = | reattachment length (mm) |
| Lxuu | = | streamwise extent of Ruu (mm) |
| = | streamwise extent of | |
| Lyuu | = | wall-normal extent of Ruu (mm) |
| = | wall-normal extent of | |
| = | Reynolds number (–) | |
| Ruu | = | streamwise correlation function (–) |
| = | wall-normal correlation function (–) | |
| U | = | streamwise mean velocity (m s–1) |
| Uo | = | bulk velocity (m s–1) |
| Um | = | local streamwise maximum mean velocity (m s–1) |
| Uj | = | jet exit velocity (m s–1) |
| u | = | streamwise fluctuating velocity (m s–1) |
| u′ | = | streamwise turbulence intensity (m s–1) |
| = | Reynolds normal stresses (m2s–2) | |
| = | Reynolds shear stress (m2s–2) | |
| V | = | wall-normal mean velocity (m s–1) |
| = | wall-normal fluctuating velocity (m s–1) | |
| = | wall-normal turbulence intensity (m s–1) | |
| W | = | lateral mean velocity (m s–1) |
| w | = | lateral fluctuating velocity (m s–1) |
| xr | = | streamwise reference point for two-point correlation analysis (mm) |
| ym | = | wall-normal location of Um (mm) |
| yr | = | wall-normal reference point for two-point correlation analysis (mm) |
| y0.5 | = | wall-normal half width (mm) |
| yt | = | tailwater depth (mm) |
| z0.5 | = | lateral half width (mm) |
| Δx | = | streamwise spatial distance (mm) |
| Δy | = | wall-normal spatial distance (mm) |
| ν | = | kinematic viscosity (m2s–1) |