School of Mechanical Engineering Seminar
Wednesday 8.11.2023 at 14:00

ZOOM SEMINAR

Nanobubbles Transport in Porous Media:
Effect of Solution and Media Properties

Lina Borsky

M.Sc. student of Dr. Ines Zucker

School of Mechanical Engineering, Tel Aviv University, Tel Aviv, Israel

Nanobubbles have been increasingly used in various applications involving porous media such as groundwater remediation and irrigation. However, the fundamental scientific knowledge regarding the interactions between nanobubbles and the media is still limited. In this study, we investigated how changes in solution chemistry (pH, ionic strength, and valence) and media characteristics (size and wettability) affect size and concentration of nanobubble under dynamic conditions using column experiments. Quartz crystal microbalance with dissipation monitoring (QCM-D) provided a deeper understanding of nanobubbles’ interactions with solid phase. The irreversible formation of an elastic nanobubbles layer is observed on the solid surface, a phenomenon that increases with ionic strength. Our findings suggest that nanobubbles are less mobile in solutions of higher ionic strength and valence, lower pH and smaller porous media sizes, while wettability of porous media has negligible influence on retention of nanobubbles. Overall, our findings provide insights into the underlying mechanisms of nanobubble interactions and suggest potential strategies to optimize their performance in various applications.

https://tau-ac-il.zoom.us/j/86497933118

School of Mechanical Engineering Seminar
Monday June 26.6.2023 at 14:00

Wolfson Building of Mechanical Engineering, Room 206

Experimental and Computational Optimization of Axis-symmetric Shapes with Flow Control

Stav (Pinto) Jacob

M.Sc. research under the supervision of

Prof. Avraham (“Avi”) Seifert, Tel Aviv University, Department of Mechanical Engineering

Assoc. Prof. Oksana Stalnov, Technion, Faculty of Aerospace Engineering

In the field of aviation, it is necessary to design aerodynamic bodies with a large internal volume to transport people, cargo, systems, and more. However, "bluff" body geometry with a large volume produces a considerable drag force, thus compromising energy efficiency. This study, conducted as part of the KAMIN Innovation Authority project, aims to design an axisymmetric blunt body geometry by integrating computational and experimental methods to reach geometric optimization of the geometry with the inherent incorporation of Active Flow Control (AFC) technology.

This research is divided into three stages. The first stage involves defining and characterizing the body and the optimization problem. An axisymmetric body geometry was parametrically defined to promote flow separation at the body's rear. This design allows controlled flow reattachment through an AFC, incorporating steady suction from suction slots and steady blowing from the trailing edge, with energy input as a parameter. A decision space and an objective space were defined, and an evolutionary optimization algorithm was selected accordingly.

In the second stage of the study, an optimization procedure and computational fluid dynamics (CFD) calculations were conducted. Various elements were evaluated, including the optimal baseline configuration, optimization strategy, optimal blowing nozzle size, and the suction slot number. The optimization section concluded that using a multi-objective optimization strategy and flow control that includes two adjacent suction slots and a larger blowing nozzle opening significantly improves all optimization parameters - volume, drag, and suction coefficients. Furthermore, defining the decision space is a crucial step in the optimization process and substantially impacts the outcomes.

In the third and final stage, the results of the numerical calculations were verified, and wind tunnel tests were performed on the optimal configuration. Furthermore, a comparison was conducted with the model examined during the initial year of the KAMIN project. Based on the comparison, utilizing an evolutionary optimization process instead of a manual one led to the model's volume and energy efficiency enhancements.

In conclusion, computational optimization and active flow control made it possible to decrease the drag on the model by 34% at a speed of 25 meters per second. Additionally, the internal volume increased by 9%. This study suggests that future research and industrial applications could benefit from optimizing processes and implementing similar flow control systems to enhance performance and energy efficiency.

Join Zoom Meeting https://tau-ac-il.zoom.us/j/86497933118

Electrical Engineering Colloquium 

Speaker: Prof. Ram Zamir

Title: Engineer or Mathematician

Abstract 

My academic career took me from a practical EE path (as a teenager and a technical officer in IDF) to mathematically-oriented directions.  In my talk, I will try to give the flavor of the original research questions I dealt with, and how they turned into mathematical formulations and results. There are some pros and cons to this "EE-math transformation", and perhaps some moral for the young researchers...   
 

Light refreshments will be served before the lecture

This colloquium is not counted toward seminar credit.

ההרצאה לא מזכה בקרדיט שמיעת סמינרים.

יום הפרוייקטים של המחלקה להנדסה ביו-רפואית 2023 יוצא לדרך!

מיקום האירוע: מסדרון בניין כיתות הנדסה - 20/06/23 

09:00-13:00    בחינות פרוייקטים

13:00-14:00   התכנסות - יוגש כיבוד קל

14:00-16:00   יריד פוסטרים

16:00-16:10   פרופ' נתן שקד – דברי סיכום ראש המחלקה להנדסה ביו-רפואית

16:10-16:30   הצגת פרוייקטים מצטיינים

16:30             סיום משוער

נשמח לראותכם!

פרופ' נתן שקד ראש המחלקה

וצוות הקורס, פרופ׳ אורי נבו, ד"ר תמיר גבאי, ד״ר דותן קמבר ושיר בהירי אליצור