UniSA Research Archive

    Ultrasonic Streaming in incompressible fluids - modelling and measurements

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    Acoustic streaming is a fundamental nonlinear phenomenon resulting from high frequency vibration in fluids. Known and investigated by Rayleigh and contemporary scientists, it attracts renewed interest due to the availability of powerful computational tools, advanced photography and precise laser velocimetry instrumentation, which can produce accurate experimental results. Its physical mechanism however is still not clearly understood. The analysis appears limited by the traditional premises of harmonic analysis, radiation force and wave propagation and reflection with the focus on nonlinear terms of the inertial frame formulations. Following our earlier analysis of nonlinear effects on rigid particles in a streaming fluid using time domain (TD) finite element (FE) analysis with a moving mesh via Comsol™, we present the modelling of ultrasonic streaming alone. We use state of the art laser velocimetry instrumentation to measure the average velocity of 0.5μm latex tracer particles in a 0.3-4 mms-1 streaming water insonified in the 1MHz frequency range. We use LabView™ virtual instrument to analyse light scattered by a swarm of particles in the moving fringes of crossed laser beams and find the ensemble particle motion from the frequency spectrum of the signal. In order to verify the FE modelling results with respect to the streaming velocity, the electric power is monitored at the transducer terminals. Our FE simulation, based on the Navier-Stokes (NS) equation for viscous incompressible fluids, does not involve wave propagation and radiation but is capable of representing the transient development of streaming, effects of boundaries and effects of the character of the ultrasonic source. Our investigation shows that streaming is neither implied by a time-varying topology nor associated with the asymmetry or even with the movement of the source or the fluid surface. Surprisingly, the streaming velocity is increased by making the enclosure fully symmetrical

    Construction Challenges in Remote Australian Locations

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    The Australian construction industry has similar characteristics to many construction industries around the world. However, Australia's construction industry needs to service a country with a large percentage ofremote and isolated areas. These remote and isolated areas have recently seen major demand for construction works in a large part due to the current resources boom. Remote construction projects introduce many challenges not witnessed in urbanized locations. Therefore, this research aims to identify the main challenges facing Australian construction contractors in remote locations. Construction projects in general are complex and require a high degree of management. In remote areas this is seen as being intensified. Hence, this research sets out to highlight the contributing factors to the problem. It surveyed industry practitioners in relation to construction in remote areas. Likert and ranking scale methods were used in questionnaires with 75 returned. The results were analysed and discussed based on measuring collective participant response to the issues. The findings confirmed that there are major challenges associated with remote construction activity. Significant issues were found to reside within the areas of human resources, production, cost management, infrastructure and communications. Some reasoning of issues and courses of action were also offered. Remote construction activity within Australia is expected to further increase in coming years so it is hoped that the findings will be useful to industry practitioners. Whilst the research is based within the Australian construction industry the findings are thought to relate to other countries and industries facing similar challenges in the geographical context

    Modeling 100 year ARI floods in South Australian Catchments

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    This paper presents the results of a regional flood study undertaken for South Australia (SA). In the first part of the study suitability of the Generalized Extreme Value (GEV) distribution fitted by LH moments for characterising at-site flood behaviours is investigated. Visual assessments through probability plots as well as an objective assessment through Monte-Carlo simulations were conducted to identify the most appropriate order of LH moments from L, L2 and L4 for fitting the GEV distribution function to annual maximum series for the 23 selected catchments. In the second part, the selection of the most appropriate form of the least squares regression based on the estimated error covariance matrix and the development of the regional prediction model were undertaken. The GEV fitted by L4 moments was selected for at-site flood frequency analyses considering the bias and relative efficiency estimates of the quantile estimates. Based on the estimated error structure, the Generalized Least Squares (GLS) regression approach was identified as the best technique to develop the regional model. Reliability of the model predictions was demonstrated by using 3 randomly selected test catchments

    The African Wilderness with Dick Roughsey OBE

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    The African Wilderness with Dick Roughsey OBE

    Portraits from a Land without People

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    A pictorial anthology of indigenous Australia 1847-2008

    Living Aboriginal History of Victoria

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    Stories in the oral tradition

    Healing a Divided Nation

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    Land Rights - an Aboriginal Perspective
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