Mathematical engineers discover rigid 'hairpin' structures in centres of turbulence.

Anyone who has experienced a bumpy air journey will be familiar with the chaotic nature of turbulent flow, which results from the interaction of air masses moving at different speeds.  However, scientists unravelling the complex fluid dynamics of such systems have discovered that they are not as disorderly as they seem, raising the possibility that we could one day control turbulence and its effects.

Dr Tomoaki Itano, of Kansai University, Japan, and Dr Sotos Generalis, of Aston University in the UK, used thousands of computer-generated shear flow models to obtain a new solution for a particular flow configuration called 'Planar Couette Flow'.  This occurs between two planar boundaries which are moving relative to each other. Reporting in the journal Physical Review Letters, the researchers describe their new solution, in which the main component has the shape of a hairpin, as "a tapestry of knotted vortices".

Previously, only wall structures at the edge of turbulent flow had been discovered.  Although scientists had thought a 'wake' structure (one not extending to the walls) might be present, this is the first time its existence has been proved.

Explaining the wider relevance of the findings, Dr Generalis said: "The hairpins expose an all new 'view' of the transition to turbulence". The team now plan to investigate whether similar structures occur in other shear flow regimes, and envisage far-reaching applications of their research in fields including machinery, medicine and travel.

Scientists have found a way to predict wind speed using artificial neural networks.

With fossil fuels soon to be exhausted, there is much emphasis on moving to renewable and clean sources of energy. One of them is wind power which contributes to about 10% of total energy in Europe. One of the problems is forecasting accurately how much power will actually be generated on a daily basis. Hence the need for a short term wind dynamics and speed prediction model. Sancho Salcedo-Sanz et al from the Escuela Politecnica Superior, Spain have come up with a prediction system based on neural networks for this purpose.

 Artificial neural networks (ANN) are parallel and distributed information processing systems which are based on the model of a neuron. Firstly the authors supply it with past information like temperature, atmospheric pressure and wind speed data along with how much power did the aero-generators produce. This enables the system to 'learn' what happens. So once the training is over, the ANN can make predictions on what the power output will be, just given parameters apart from wind speed. This method has been used to forecast wind speed prediction of a wind park located at Albacete, Spain and was found to be better than its predecessor by 2%. Though 2% sounds small, it is a big value considering energy production runs in millions of Euros.

Research published by Nutrition and Metabolism shows that white tea extract from the Camellia Sinensis plant may have anti-obesity effects.

The finding shows that white tea extract decreases fat incorporation during the genesis of human fat cells (adipocytes). At the same time, the existing adipocytes are prompted to break down the fat that they contain, indicating the stimulation of lipolysis activity. Importantly, such fat reduction in adipocytes is not due to toxic side effects.

"The rising incidence of obesity-associated disorders including cardiovascular diseases and diabetes constitutes a growing problem in industrialised countries. White tea may be an ideal natural source of slimming substances," according to Marc Winnefeld, leader of the research team from Beiersdorf AG, Germany.

White tea is plucked from the buds or first leaves of the plant with minimal processing. The extract contains substances such as the antioxidant epigallocatechin-3-gallate (EGCG) and methylxanthines such as caffeine that could be responsible for the anti-adipocytes effects and stimulation of fat mobilization from mature cells.

The collapse of seabed in oil reservoirs has long been a problem. If this is solved, it could generate billions of additional income for the oil industry. A team of researchers from the International Research Institute of Stavanger has found that seawater could induce chemical processes that weaken the chalk reservoir.

"Until now, rock mechanics have not been too concerned about chemistry," said Dr. Hiorth. The research team discovered that the mineral properties of chalk changed when exposed to saline water. This could affect the way oil flows through the reservoir.

The researchers study the chalk's behaviour when exposed to temperatures and pressures typical of an oil reservoir's conditions. Seawater is injected from below to flood the cell as it is when oil is extracted. The breakthrough discovery by post doctor Hildebrand-Habel was the precipitation of minerals under the scanning electron microscope. This precipitation is thought to lead to the dissolution of a chalk structure that could cause the seabed to collapse when oil is extracted.

Experiments and mathematical models are currently being developed to predict how seawater dissolves the chalks. "The understanding of interaction between seawater and chalk will also improve our understanding of other surface-related processes such as wettability, precipitation of calcium sulphate and stability of production wells which are important to the oil industry." Added Kristiansen, Rock Mechanical Advisor with BP.

The oil in the reservoir is responsible for upholding the pressure from the layers above. However, when the oil depletes, the seabed will start to sink as the chalk has to withstand increased weight. The mechanical properties of the chalk change and scientists are unable to predict the rate of subsidence. At present, the measure taken to prevent further sinking is by water injection into the reservoir. This however, is not a long term solution as the oil wells remain unstable and sinking continues.

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