Mechanical Engineering MS Thesis Defense by Ms. Farnaz Feyli
When: Tuesday,
August 15, 2023
2:00 PM
-
4:00 PM
Where: > See description for location
Description: Mechanical Engineering MS Thesis Defense by Ms. Farnaz Feyli
DATE:
August 15, 2023
TIME:
2:00 p.m. - 4:00 p.m.
LOCATION:
Science & Engineering (SENG), Room 110(Material Science Lab)
and
Zoom Meeting:
https://umassd.zoom.us/j/97877516298?pwd=R0F5ZzVZQThZWnJyRXAwWnlPUzJuQT09
Meeting ID:
978 7751 6298
Contact scunha@umassd.edu for Passcode
TOPIC:
Experimental Study of Asymmetry Effects on Vortex-Induced Vibration (VIV) in Curved Tapered Circular Cylinders
ABSTRACT:
This thesis presents an experimental study focused on investigating the vortex-induced vibration (VIV) response of a curved tapered circular cylinder under varying flow conditions. The primary objective was to examine the influence of introducing two different asymmetries, curvature, and tapering effects, into the conventional vortex-induced vibration study of a vertical circular cylinder. The study investigated fluid-structure interaction responses for two configurations of the curved cylinder, namely concave and convex, based on their orientation with respect to the oncoming flow. Various characteristics of the cylinder's response, including amplitudes, oscillation frequencies, hydrodynamic forces, and flow structures around the cylinder, were investigated.
Our results revealed that when the tapering was introduced to the system, in the concave orientation, the curved and tapered cylinder exhibited the lowest amplitude of oscillation. Both orientations demonstrated a wider lock-in range compared to the conventional VIV observed in the vertical cylinder, indicating a larger range of reduced velocities at which vortex-induced vibrations occur. Furthermore, the onset of the lock-in range was observed to be delayed in these configurations. The addition of tapering to the curved cylinder did not change the dominant frequency of oscillation.
To gain further insights, we utilized qualitative (Hydrogen bubble imaging) and quantitative (Time-resolved volumetric particle tracking velocimetry) flow visualization techniques to analyze the vortex-dominated wake of the cylinder. For non-oscillatory cases when the cylinder was held stationary, coherent vortex structures were observed, following the cylinder's geometry along its spanwise length in all configurations. However, when the cylinder was allowed to oscillate, the presence of a secondary vortex structure became evident, that was absent in the non-oscillatory cases. In these instances, the shedding patterns along the length of the cylinder varied, exhibiting either a "2P" or "2S" pattern, where "2P" and "2S" refer to two pairs and two single vortices being shed per one cycle of oscillation, respectively. Additionally, the flow field analysis demonstrated that the tapered cylinder exhibited weaker and less coherent vortex structures towards the tapered tip of the cylinder compared to the non-tapered cylinder. This finding suggests that the interaction between the structure and the fluid decreased for the tapered cylinder, resulting in a lower amplitude of oscillation, as observed in our study. Snapshots from the hydrogen bubble flow visualizations further supported the differences in shedding patterns and the stronger vortex shedding in the non-tapered case compared to the tapered case.
Overall, the findings of this study underscore the importance of considering system asymmetry in fluid-structure interactions. These results have significant implications for various engineering applications involving fluid-structure interactions, enabling improved design and optimization of structures exposed to fluid flows.
ADVISOR:
-Dr. Banafsheh Seyed-Aghazadeh, Assistant Professor of Mechanical Engineering, College of Engineering, UMassD
COMMITTEE MEMBERS:
- Dr. Hamed Samandari, Assistant Teaching Professor of Mechanical Engineering, College of Engineering, UMassD
- Dr.Hangjian Ling, Assistant Professor of Mechanical Engineering, College of Engineering, UMassD
Open to the public. All MNE students are encouraged to attend.
For more information, please contact Dr. Banafsheh Seyed-Aghazadeh (b.aghazadeh@umassd.edu).
DATE:
August 15, 2023
TIME:
2:00 p.m. - 4:00 p.m.
LOCATION:
Science & Engineering (SENG), Room 110(Material Science Lab)
and
Zoom Meeting:
https://umassd.zoom.us/j/97877516298?pwd=R0F5ZzVZQThZWnJyRXAwWnlPUzJuQT09
Meeting ID:
978 7751 6298
Contact scunha@umassd.edu for Passcode
TOPIC:
Experimental Study of Asymmetry Effects on Vortex-Induced Vibration (VIV) in Curved Tapered Circular Cylinders
ABSTRACT:
This thesis presents an experimental study focused on investigating the vortex-induced vibration (VIV) response of a curved tapered circular cylinder under varying flow conditions. The primary objective was to examine the influence of introducing two different asymmetries, curvature, and tapering effects, into the conventional vortex-induced vibration study of a vertical circular cylinder. The study investigated fluid-structure interaction responses for two configurations of the curved cylinder, namely concave and convex, based on their orientation with respect to the oncoming flow. Various characteristics of the cylinder's response, including amplitudes, oscillation frequencies, hydrodynamic forces, and flow structures around the cylinder, were investigated.
Our results revealed that when the tapering was introduced to the system, in the concave orientation, the curved and tapered cylinder exhibited the lowest amplitude of oscillation. Both orientations demonstrated a wider lock-in range compared to the conventional VIV observed in the vertical cylinder, indicating a larger range of reduced velocities at which vortex-induced vibrations occur. Furthermore, the onset of the lock-in range was observed to be delayed in these configurations. The addition of tapering to the curved cylinder did not change the dominant frequency of oscillation.
To gain further insights, we utilized qualitative (Hydrogen bubble imaging) and quantitative (Time-resolved volumetric particle tracking velocimetry) flow visualization techniques to analyze the vortex-dominated wake of the cylinder. For non-oscillatory cases when the cylinder was held stationary, coherent vortex structures were observed, following the cylinder's geometry along its spanwise length in all configurations. However, when the cylinder was allowed to oscillate, the presence of a secondary vortex structure became evident, that was absent in the non-oscillatory cases. In these instances, the shedding patterns along the length of the cylinder varied, exhibiting either a "2P" or "2S" pattern, where "2P" and "2S" refer to two pairs and two single vortices being shed per one cycle of oscillation, respectively. Additionally, the flow field analysis demonstrated that the tapered cylinder exhibited weaker and less coherent vortex structures towards the tapered tip of the cylinder compared to the non-tapered cylinder. This finding suggests that the interaction between the structure and the fluid decreased for the tapered cylinder, resulting in a lower amplitude of oscillation, as observed in our study. Snapshots from the hydrogen bubble flow visualizations further supported the differences in shedding patterns and the stronger vortex shedding in the non-tapered case compared to the tapered case.
Overall, the findings of this study underscore the importance of considering system asymmetry in fluid-structure interactions. These results have significant implications for various engineering applications involving fluid-structure interactions, enabling improved design and optimization of structures exposed to fluid flows.
ADVISOR:
-Dr. Banafsheh Seyed-Aghazadeh, Assistant Professor of Mechanical Engineering, College of Engineering, UMassD
COMMITTEE MEMBERS:
- Dr. Hamed Samandari, Assistant Teaching Professor of Mechanical Engineering, College of Engineering, UMassD
- Dr.Hangjian Ling, Assistant Professor of Mechanical Engineering, College of Engineering, UMassD
Open to the public. All MNE students are encouraged to attend.
For more information, please contact Dr. Banafsheh Seyed-Aghazadeh (b.aghazadeh@umassd.edu).
Topical Areas: Faculty, General Public, Students, Students, Graduate, Students, Undergraduate, University Community, College of Engineering, Mechanical Engineering, Lectures and Seminars