סמינר מחלקתי ביה"ס להנדסה מכאנית Roee Finkelshtain and Slava Burkin
School of Mechanical Engineering Seminar
Thursday, April 5, 2017 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
Application of diffusive interface method to thermocapillary - driven flow of two immiscible fluids.
Viacheslav Burkin
M.Sc. Student of Prof. Alexander Gelfgat
A diffusive interface method was used to solve a problem of flow of two immiscible fluids driven by a thermocapillary force in a closed rectangular cavity. The traditional approach to this problem considers boundary conditions along the interface between two fluids, similar to those applied at physical boundaries of the volume: continuity of the viscous stresses and the heat flux.
Since boundaries between two liquids are usually curved, an accurate calculation of normal and tangent derivatives, needed for a straight-forward implementation of the boundary conditions, becomes a very complicated task. An alternative approach, that noticeably simplifies numerical model, is the volumetric approximation of the thermocapillary force. This approach assumes that fluids properties across the liquid-liquid interface change as a smoothed Heaviside function, while thermocapillary force is defined by a smeared delta-function. In current work we provide further enhancement of this method, by comparing different Heaviside functions by their accuracy relative to the known analytical solution, and adopt this method for computation of steady flow and analysis of their stability.
School of Mechanical Engineering Seminar
Wednesday, April 5, 2017 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
Ultrasonic yield assessment
Roee Finkelshtain
G. Kósa1, Y. Yovel2, A. Bechar3
Israel
1School of Mechanical Engineering, Tel Aviv University (TAU), Israel
2Faculty of Life Sciences, TAU, Israel
3Institute of Agricultural Engineering, Agricultural Research Organization (ARO),
The spectrum of an ultrasonic return echo from plants has shown to contain information about them. This research focuses on developing an ultrasonic robotic sensing system, analyzing the ultrasonic classification features that would ultimately be used as the basis for a yield estimation robotic system, and developing an algorithm for prediction of fruit mass per plant based on the ultrasonic echoes returned from a plant. The ultrasonic sensor system was tested in a lab and pepper greenhouse environments and on single pepper plants, single leaves and fruit. The ultrasonic sensor system was integrated to a robotic platform and field experiments were conducted in a research pepper greenhouse. The results showed the potential of ultrasonic sensors for such a robot in classifying plants and greenhouse infrastructures, the ability to detect hidden plant rows and fruits as well as making an estimation of the fruit mass in single plants. A developed multi linear regression model for estimating the energy level was found to be highly significant with of and for to and to ranges respectively. The estimation accuracy is improved by mounting the sensing system on a monitoring robot and acquiring large plant-orientation sampling sets.