Research update

Go with the flow

Researchers from the University of Bari in Italy are using Ansys flow simulation software to model volcanic ash clouds. The work is to develop a better understanding of how ash clouds behave during an eruption. The software is being used to simulate as particles in a pyroclastic flow of a volcanic column of ash and smoke. To do this researchers have used multiphase modeling to look at the transfer of particles from a volcano’s crater and through the air. The system has built in flexibility for defining the size and distribution of the particles and modeling the breakup of particles in different flow conditions are represented by different colors in the software simulation. Fine ash particles are a focus of the work because they can be blown by the wind over long distances for long periods. Ash particles can be dispersed for hundreds of kilometers. The simulation has been created from experiments in which researchers created miniature ash clouds based on the Icelandic volcano eruption. The clouds created in the experiments were digitalized for simulation. Fluid dynamic solutions have been used for simulating flows of steam from cooling towers smoke from chimneys and the behavior of air in air conditioning and ventilation systems. The Italian government has shown an interest in using the technology to understand volcanic eruptions By knowing more about the behavior of ash clouds, the Bari researchers say it could also help reduce flying restrictions during a eruption.

Safe at work

Researchers at Exeter University are developing a smart material to use in blast curtains as a protection against a terrorist attack. Conventional blast curtains are little more than simple netting and are prone to stretching and tearing which stops them catching debris. The material being developed at Exeter University X-AT materials workshop however is auxetic meaning it expands when a force acts upon it getting after rather than thinner when stretched. Under tension a large number of pores open up across the surface of the material allowing the shock wave through but leaving the curtains intact to catch glass and other debris. For the purposes of the research project the textile is produced from a traditional wooden loom. Each yarn consists of an elastic fiber with a normal stiff fiber wound around it in a helical way. Researchers led by Patrick Hook have been working with auxetic yarn at Exeter University for 10 years. Hook went on to set up a spin out company Auxetix. The blast curtains could be used in government offices to protect occupants from injury from flying glass in the event of a terrorist attack. Mike Sloan main researcher for the project says it’s a very simple idea but sometimes those are the best ones. Our work is focused on what fiber we want and tailoring it for a particular application. The wrap angle is adjusted to adjust the auxetic properties. This has applications beyond blast curtains such as fiber reinforced composites medical applications or even dental floss. The three year project is halfway through an the first blast tests using TNT took place in March partners in the EPSRC- funded project include the Exeter spin out Auxetix the Home Office scientific development branch and the center for the Protection of National infrastructure .

Fine tuning

Silicon Sensing has developed a range of small precision micro-electromechanical systems (Memes) navigation and pointing gyros for automotive navigation applications. The tiny Pinpoint gyro measures just 6 x 5 x 1.2mm weighs less than 0.08 g and draws 4.2 mA on its 3V supply. Silicon Sensing says it is the only Mems gyro to use a fully balanced vibrating silicon ring; others use various forms of simple unbalanced open loop vibrating mass structures (e.g. tuning fork / comb type). The 3mm diameter balanced which resonates at 22kHz in a closed loop control system can be thought of as an infinite number of tuning forks integrated to create a fully balanced vibrating circular structure. This, it says providers excellent arte output stability over time, temperature vibration and shock for a Mems gyro at the lower end of the market. Other useful features include analogue and digital SPI output modes user selectable dynamic ranges between 75 and 9000 /s for optimum sensitivity user selectable band width up to 100Hz for noise performance optimization d internal temperature output enabling external thermal compensation. The gyro is aimed at next generation automotive in dash navigation applications for yaw rate sensing of the vehicle. The gyro is used in conjunction with the wheel speed sensor to enable the navigation system to perform dead reckoning navigation the gyro tells the system in which direction the car is pointing relative to the last known position fix, and the wheel speed sensor measures th distance traveled along that hading this can then be used to estimate the new position and compare it with the digital map. As the gyro and wheel speed sensor are producing outputs at 1,000 times a second the navigation system can be more responsive to the vehicle’s movements. By comparison, a GPS position is updated once a second. Eric Whitley business development executive at Silicon Sensing says Pin Point is major step forward in terms of precision. It has a very low noise output and base error allowing greater navigation precision and for longer periods where GPS is not available because of tunnels and tall buildings. It’s also a major step forward in terms of cost, size and power consumption for this application.

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