November 2024: Jet flows can be found all around us both in industrial applications (e.g. jet propulsion, impinging jet cooling), human health (e.g. drug delivery devices, virus spread through coughing), and environmental settings (e.g. volcano eruptions). Although particle-laden jets have been studied extensively during the last decades, still little is known about polydisperse particle-laden jets in the two-way coupling regime. This research will leverage combined inline digital holographic cinematography with high-speed stereoscopic particle image velocimetry (stereo-PIV) to resolve the spatio-temporal distributions of both the beads and the surrounding flow field. The focus of the research will be on polydisperse spherical beads in the two-way coupling regime for which hardly any data exists.

November 2024: For a research project funded by the Pazy Foundation in collaboration with Rafael – Advanced Defense Systems Ltd. and Assoc. Prof. B. Cukurel of the Faculty of Aerospace Engineering (Technion – IIT), we are looking for PhD, MSc students and PostDocs. The research topic is on the experimental investigation of flow field  and heat transfer characteristics of a co-axial impinging synthetic jet. In this research, state-of-the-art measurement techniques such as  stereoscopic particle image velocimetry (stereo-PIV) and high speed thermal IR – imaging are employed. Within this project, several positions are available, from final undergraduate projects (The Brakim or Raamim program) to MSc, PhD and PostDoc positions.

Since the earth’s surface is always heterogeneous to some extent, the topography plays a significant role in the surface fluxes of momentum, heat, humidity and other quantities including dust and pollen. The variation of these fluxes as a result of land-atmosphere interactions has important implications for the hydrological cycle. These processes become even more relevant in desert – like, arid environments, where water management is essential for agriculture.

From left to right, top to bottom:

Moti Raizner, Barak-Chaim Sabagh, Lior Eshbal, Rene van Hout

Sofia Kuperman, Daniel Kovalev, Vladislav Rinsky

Impinging jets are used extensively in many heat and mass transfer applications found in industrial processes such as electronic component cooling, aircraft de-icing and turbine blade cooling. Impinging jets exhibit complex flow physics that is difficult to numerically simulate.

In the present experiments, a round pulsating jet with uniform jet exit velocity was studied at small H/D (= 2.0) while limiting the effect of entrainment by partial confinement. Our results indicated local and overall heat transfer enhancement at Re = 4,606 and 8,024 while a slight reduction was observed for Re = 13,513. The heat transfer measurements were accompanied by detailed planar particle image velocimetry (PIV) measurements.

Recently, we have studied the three-dimensional orientation dynamics (“tumbling” rates) of rigid heavy nylon fibers in isotropic turbulence.

This research was performed by Mr. Adi Amir in collaboration with Rafael, Advanced Defense Systems LtD. A model was developed to evaluate the possibility of using nocturnal radiative cooling for stand-alone applications.

A tethered bluff body is a configuration commonly occurring in engineering applications (e.g. blimps, ocean buoys) as well as in nature (e.g. seed or pollen dispersal by plants). Here we study the vortex-induced vibrations of a tethered sphere using tomographic particle image velocimetry that allows us to measure the instantaneous 3D flow field in the wake of the sphere.

The research objectives: (i) Measurement of the 3D wake structure of a tethered sphere over a range of Reynolds numbers and mass parameters. (ii) Determination of the fluid forcing acting on the tethered sphere using the measured 3D flow fields. This will provide insight into the relevant energy transfer mechanisms between fluid and sphere and possible applications to green energy harvesting applications.

A sphere is a prototypical bluff body and although studied for over a century, the wake of a sphere still poses many questions. Recently, we have been using state-of-the-art tomographic particle image velocimetry to measure for the first time the instantaneous three-dimensional flow structure in the wake of a sphere. In particular we found evidence for the generation of so-called induced vortices whose legs (IVL) and head (IVH) can be observed.