Measurements of an elliptic pipe jet
This study presents the findings of the mean velocity, Reynolds normal stresses and Reynolds shear stresses for a fully developed pipe jet emanating from a smooth, elliptic pipe of length 999 m and a nozzle exit of aspect ratio (AR) 2:1 (50 mm by 25 mm). The jet flow is fully developed and turbulent...
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| Format: | Final Year Project (FYP) |
| Language: | English |
| Published: |
2014
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| Online Access: | http://hdl.handle.net/10356/60270 |
| _version_ | 1826124047026487296 |
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| author | Vibhas Pahuja |
| author2 | Chua Leok Poh |
| author_facet | Chua Leok Poh Vibhas Pahuja |
| author_sort | Vibhas Pahuja |
| collection | NTU |
| description | This study presents the findings of the mean velocity, Reynolds normal stresses and Reynolds shear stresses for a fully developed pipe jet emanating from a smooth, elliptic pipe of length 999 m and a nozzle exit of aspect ratio (AR) 2:1 (50 mm by 25 mm). The jet flow is fully developed and turbulent in nature. The lack of published studies on the topic of elliptic pipe jets and the effects of initial conditions on non-circular jets provide the main motivation for undertaking this study.
The velocity and stress measurements were obtained using two kinds of probes:- single-wire and cross-wire, at stream-wise distances from the exit along both the major (y) and minor (z) axes. This stream-wise distance was normalized against the equivalent diameter of the elliptic nozzle, De which was 35.4 mm. The exit velocity of the jet used was 24.0 ± 0.5 ms-1, which gave a Reynolds No. of 54183.67.
The first part of the experiment was carried out using a single-wire probe to find the distribution of the stream-wise velocity component (u) along the lateral (y) and span-wise (z) axes at various stream-wise distances (x). Both the mean Um and root mean square (rms) u’ were measured at local points. The different spreading rates along the y and z axes can be attributed to the fact that momentum thickness was found to be higher in the y axis when compared with the z axis. Also, the elliptic pipe jet displayed greater momentum thickness as compared to the contraction jet. The potential core was found to end by x=4De distance downstream. The self-similarity feature was observed from x=6De for the major axis (y) while the minor axis (z) recorded this feature from x=5De. The different jet spreading rates along the two axes also led to an axis-switching phenomenon at x=15.5De.
The second part involved measuring two velocity components (u and v, u and w) along with the shear stress distributions at various stream-wise distances, again along the other two axes, using a cross-wire probe. 5 parameters, namely Um, u’, Vm (or Wm), v’ (or w’), (uv) ̅ and (uw) ̅ were measured in this part. Self-preservation of Um was achieved from x=6De in the major axis and from x=5De in the minor axis, thus mirroring the result of the single-wire probe experiment. However, the axis switching location occurred earlier in this case at a distance x=11.5De. It appears that the Reynolds normal stresses u’,v’ and w’ achieve self-similarity by x=20De, though more data at locations further downstream needs to be recorded to make a conclusive statement. For higher order turbulent magnitudes (Reynolds shear stresses), self-preservation was not reached within the maximum distance traversed x=38De.
Also, the comparisons of the 2:1 AR elliptic pipe jet were made with the contoured contraction elliptic nozzle jet with AR 2:1 (Zhang & Chua, 2012) to bring out the effect of the initial conditions. |
| first_indexed | 2024-10-01T06:14:17Z |
| format | Final Year Project (FYP) |
| id | ntu-10356/60270 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T06:14:17Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | ntu-10356/602702023-03-04T18:51:13Z Measurements of an elliptic pipe jet Vibhas Pahuja Chua Leok Poh School of Mechanical and Aerospace Engineering DRNTU::Engineering::Mechanical engineering::Fluid mechanics This study presents the findings of the mean velocity, Reynolds normal stresses and Reynolds shear stresses for a fully developed pipe jet emanating from a smooth, elliptic pipe of length 999 m and a nozzle exit of aspect ratio (AR) 2:1 (50 mm by 25 mm). The jet flow is fully developed and turbulent in nature. The lack of published studies on the topic of elliptic pipe jets and the effects of initial conditions on non-circular jets provide the main motivation for undertaking this study. The velocity and stress measurements were obtained using two kinds of probes:- single-wire and cross-wire, at stream-wise distances from the exit along both the major (y) and minor (z) axes. This stream-wise distance was normalized against the equivalent diameter of the elliptic nozzle, De which was 35.4 mm. The exit velocity of the jet used was 24.0 ± 0.5 ms-1, which gave a Reynolds No. of 54183.67. The first part of the experiment was carried out using a single-wire probe to find the distribution of the stream-wise velocity component (u) along the lateral (y) and span-wise (z) axes at various stream-wise distances (x). Both the mean Um and root mean square (rms) u’ were measured at local points. The different spreading rates along the y and z axes can be attributed to the fact that momentum thickness was found to be higher in the y axis when compared with the z axis. Also, the elliptic pipe jet displayed greater momentum thickness as compared to the contraction jet. The potential core was found to end by x=4De distance downstream. The self-similarity feature was observed from x=6De for the major axis (y) while the minor axis (z) recorded this feature from x=5De. The different jet spreading rates along the two axes also led to an axis-switching phenomenon at x=15.5De. The second part involved measuring two velocity components (u and v, u and w) along with the shear stress distributions at various stream-wise distances, again along the other two axes, using a cross-wire probe. 5 parameters, namely Um, u’, Vm (or Wm), v’ (or w’), (uv) ̅ and (uw) ̅ were measured in this part. Self-preservation of Um was achieved from x=6De in the major axis and from x=5De in the minor axis, thus mirroring the result of the single-wire probe experiment. However, the axis switching location occurred earlier in this case at a distance x=11.5De. It appears that the Reynolds normal stresses u’,v’ and w’ achieve self-similarity by x=20De, though more data at locations further downstream needs to be recorded to make a conclusive statement. For higher order turbulent magnitudes (Reynolds shear stresses), self-preservation was not reached within the maximum distance traversed x=38De. Also, the comparisons of the 2:1 AR elliptic pipe jet were made with the contoured contraction elliptic nozzle jet with AR 2:1 (Zhang & Chua, 2012) to bring out the effect of the initial conditions. Bachelor of Engineering (Mechanical Engineering) 2014-05-26T04:43:09Z 2014-05-26T04:43:09Z 2014 2014 Final Year Project (FYP) http://hdl.handle.net/10356/60270 en Nanyang Technological University 134 p. application/pdf |
| spellingShingle | DRNTU::Engineering::Mechanical engineering::Fluid mechanics Vibhas Pahuja Measurements of an elliptic pipe jet |
| title | Measurements of an elliptic pipe jet |
| title_full | Measurements of an elliptic pipe jet |
| title_fullStr | Measurements of an elliptic pipe jet |
| title_full_unstemmed | Measurements of an elliptic pipe jet |
| title_short | Measurements of an elliptic pipe jet |
| title_sort | measurements of an elliptic pipe jet |
| topic | DRNTU::Engineering::Mechanical engineering::Fluid mechanics |
| url | http://hdl.handle.net/10356/60270 |
| work_keys_str_mv | AT vibhaspahuja measurementsofanellipticpipejet |