Numerical assessment of the wake flow mechanism of spanwise expansion interference behind spire by smooth wall boundary turbulence
For decades wind tunnel has been utilized to generate a quasi-atmospheric boundary layer to observe the wake flow around objects submerged within the ABL. The quarter elliptic-wedge spire is the most commonly used as a vortex generator among other passive devices. However, despite numerous past stud...
Saved in:
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | en |
| Published: |
2024
|
| Subjects: | |
| Online Access: | https://umpir.ump.edu.my/id/eprint/46722/1/Numerical%20assessment%20of%20the%20wake%20flow%20mechanism%20of%20spanwise%20expansion%20interference%20behind%20spire%20by%20smooth%20wall%20boundary%20turbulence.pdf https://umpir.ump.edu.my/id/eprint/46722/ |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | For decades wind tunnel has been utilized to generate a quasi-atmospheric boundary layer to observe the wake flow around objects submerged within the ABL. The quarter elliptic-wedge spire is the most commonly used as a vortex generator among other passive devices. However, despite numerous past studies that utilize rows of spires to generate deep quasi-ABL, only a few researchers targeted spires as the main subject of their investigation. Moreover, the equation to design the spire dimension as well as to predict the depth of the ABL generated is not derived. Hence, the present work originally aims to investigate the wake flow structure behind a single quarter elliptic-wedge spire and its aerodynamic interaction with a smooth wall boundary layer. In addition, the equation to design the quarter elliptic-wedge spire type dimension as well as to predict the depth of the ABL generated is derived based on the literature review. Due to a limitation of the wind tunnel to predict the wake flow in the far wake region, a computational fluid dynamics (CFD) simulation, predicting the wake flow structure behind a single quarter elliptic-wedge spire, was conducted using the OpenFOAM® software. The computational domain consists a smooth flat plate, and a single quarter elliptic-wedge spire. A comparison of two Reynolds-Averaged Navier–Stokes (RANS) turbulence models, namely the standard k-ɛ model and the SST k-ω model, was conducted. Both SIMPLE and PISO algorithm was used as the solver and ParaFOAM® was used as the post-processing software. The wake flow behind a single spire was successfully observed. Based on the validation analysis, it was found that the simulation is in good agreement with the previous wind tunnel experiment data with absolute accuracy error (%E) less than 10% in most sampling point. Hence, the velocity profiles have similar feature compared to the wind tunnel experiment data. It was found that the wake flow is recovering in both vertical and streamwise direction. However, the rate or recovery is higher above the BLH because the turbulence, which is generated within the BLH, can sustain the wake flow and reduce the recovery rate in the streamwise direction. Moreover, based on the half wake width analysis, it was found that the wake flow required a streamwise distance of 49 time the spire height (x0=49S) to be fully recovered. Finally, the application of CFD can increase the understanding of the interaction mechanism between the wake flow generated by the spire and the background boundary layer. Some enhancement, preservation and recovery of velocity deficit can be observed in the far wake region based on the CFD result. On top of that, the distance required by the wake flow to be fully recovered also can be predicted based on the CFD result. |
|---|