Labs and Facilities

A Mach 6 Hypersonic Ludwieg Tunnel (HLT) test facility was commissioned and operating since October 2021 under the Technion Wind-tunnel Complex (TWTC). The facility is 3 m long and 22 mm in diameter (inner). The tube is arranged in a ‘U’-tube configuration to save some floor space. The tube is wrapped by heater pads which can maintain a surface temperature of up to 500 K. At one end of the tube, a commercial fast-acting valve. The tube is pressurized to the desired fill pressure ranging between 3 to 10 bar. A convergent-divergent(C-D) nozzle whose interior is mirror-polished to have a smooth wall surface with a roughness radius of about 0.1 μm. The nozzle expands freely into a closed chamber of volume 0.1 cubic meter and 0.5 m long, which is kept to a vacuum level of 0.05 mbar using a rotary vacuum pump.
A wide range of Reynolds numbers (4.75 million to 18 million) is achieved with flow test time of ~12.5 ms and the effective model diameter that can be used is found to be 40 mm.
A typical layout of the experimental facility along with the optical diagnostics (a. schlieren, and b. laser Rayleigh scattering) and photographic picture of the facility is shown in the figure below.

Click here for more details about the facility

Karthick, S.K., Nanda, S.R. & Cohen, J. Unsteadiness in hypersonic leading-edge separation. ExpFluids 64, 13 (2023). (https://doi.org/10.1007/s00348-022-03559-7)

The Large Ludwieg Tube at Technion will be designed according to the principles of the Rhorwindkanal/Tube Wind Tunnel, as implemented in the latest update to the University Hypersonic Tunnel facility. It will have a length of 27m, with test section length and diameter of 900 and 500mm respectively. At its present operational Mach number is planned to 6, the tunnel has runtime of 100ms, targeting characterization of hypersonic laminar flow instabilities in the frequency range of 50kHz < f < 500kHz. The design of a Mach 8 upgrade is currently considered.

The Turbulence and Complex Flows Lab studies both large-scale turbulent flows and micro-scale fluid transport phenomena, and explores the intersection of these two domains in areas as diverse as fluidic sensing and measurement and drag reduction and micro-scale control systems. The lab performs experimental work on the fundamental physics of turbulent wall-bounded flows, with particular emphasis on observing the coherent motions within turbulent flows in order to better exploit structure in the pursuit of modifying and controlling heat and momentum transfer. The lab also operates a high speed water tunnel facility for high resolution imaging of turbulent wall-bounded flows.

The Flow Physics Lab focuses on theoretical and computational investigations of flow physics, with specific emphasis on instability and transition to turbulence. A variety of flow regimes are considered – from incompressible to hypersonic, steady, unsteady, laminar and turbulent.

The common thread guiding our research is using a minimal number of elements to describe physical phenomena. Therefore, canonical settings, where the effects of various parameters can be isolated, are often analyzed.

Our tools include in-house and open-source solvers for solutions of incompressible and compressible Navier-Stokes equations. Fully nonlinear and linearized variants are available.

A tunnel for examining the ignition process in aerospace engines up to scramjet-relevant cold-start conditions has been in operation since 2020 in the Combustion and Diagnostics Laboratory at Technion. The tunnel is meant to simulate the conditions in the recirculation zone of a scramjet engine, but can also operate at conditions relevant to gas turbine engines. Fuel testing on methane, ethylene, and ammonia have been carried out, and a spray injection system is also available.
The cross section of the ignition tunnel is 5 cm by 5 cm. The fuel-air flow rate can reach up to 100 m/s, the initial temperature is from 290 – 1000 K, and gaseous or liquid fuels can be utilized. For electrical ignition testing, two 1.6 mm diameter lanthanide tungsten electrodes with variable gap distance between 0.5 to 5 mm are available as well as a standard wall-mounted spark plug. A custom-built nanosecond-pulsed discharge power supply is available, which produces pulses with approximately 5–6 ns full width at half maximum, up to 20 kV peak voltage, and a repetition rate up to 200 kHz.
The diagnostic tools consist of a high-speed schlieren system typically operated at 50 kHz with 141 μm/pixel resolution; a high-speed infrared camera (Telops FAST-IR M3K) operated at
9500 Hz with a resolution of 481 ± 42 μm/pixel and multiple spectral filters available, a planar laser-induced fluorescence system and a PIV system.

Ignition Wind Tunnel

Hypersonic and re-entry space vehicles are designed to operate under extreme conditions and environments, such as ultra-high temperatures, intense heat fluxes, high rates of thermal oxidation, and material ablation. Ultra-high temperature ceramics (UHTCs), such as zirconium carbide (ZrC), are among the most promising materials for these applications due to their high melting points (>3,000°C), excellent strength, and superior chemical and thermal stability.

A novel sintering approach utilizing ultra-fast heating has recently been developed. In this method, ceramic samples are placed within graphite felt, which serves as a heating element. Heating is achieved by passing an electric current through the felt, which minimizes heat loss to the material and ensures efficient energy transfer to the ceramic sample. Known as ultra-fast high-temperature sintering (UHS), this technique enables rapid heating to temperatures as high as ~3000°C within just a few seconds.

At the Israel Institute of Materials Manufacturing Technologies at the Technion, in collaboration with the Metal Ceramic Interfaces Lab (led by Prof. Wayne Kaplan), an ultra-high temperature furnace was constructed inside an existing vacuum chamber, utilizing a turbo-drag vacuum pump and an external power supply. Using this setup, near full-density ZrC was successfully sintered at 2400°C in just 21 seconds (see micrograph).