Hi,
I have 6 practicals, I uploaded 3 of them and I'll upload the rest later.
Important Information:
The main questions are in the files called (Answer Sheet). I have uploaded the (Question Sheet) for every practical just to let you know what's the practical is about. ALL the answers should be written on the answers sheet.
*The Answers are going to be checked on the TURNIT IN.
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Prac 2 - Volcanoes and Aviation
We may take aviation safety from volcanic ash for granted, but in fact aircraft are very susceptible to damage from airborne particulates. Abrasion of leading edges including cockpit windows, wings, and turbines can be expensive, and at its worst can cause "flame out", where the flame in the jet engines goes out. This has happened during a number of encounters with ash clouds over the last few decades. One of the more notorious was the British Airways 747 which suffered total engine failure after encountering ash from Indonesia's Mt Galunggung in 1982. Fortunately it restarted its engines before hitting the ocean. The 1989 Redoubt-KLM incident (see Webley et al. 2011 below) was similarly close to disaster and it reinforced notions of vulnerability of passenger aircraft to volcanic ash clouds.
The Eyjafjallajokull eruption in Iceland in 2010, and the Puyehue-Cordon Caulle eruption in Chile in 2011, caused a lot of disruption to global air travel and trade, and brought this problem to recent attention. A summary of volcanic ash encouters with aviation in the Australian region is in this Hot Topic as a poster and is also available online (www.bom.gov.au/info/vaac/publications/vapostermedium.jpg).
Volcano ash warnings are co-ordinated globally via the International Airways Volcano Watch (IAVW). Nine regions cover most of the world, and each region is overseen by a Volcanic Ash Advisory Center (VAAC). The VAAC liaise closely with meteorological offices, and they issue warnings on the presence and movement of ash clouds. National meteorological authorities then send Volcanic Ash Advisories directly to airlines. The regional VAAC for Australia is in Darwin, and its website is: http://www.bom.gov.au/info/vaac/index.shtml This website has a map showing the different regions (click on one for detail of that region). They also have an excellent set of articles available: http://www.bom.gov.au/info/vaac/publications.shtml and photographs of regional eruptions: http://www.bom.gov.au/info/vaac/images.shtml
The Darwin Volcanic Ash Advisory Centre falls under the umbrella of the Bureau of Meteorology, which in turn advises airlines of any warnings. The national carrier, QANTAS, has the QANTAS Aviation Meteorological Unit (QMET) which advises and provides operational support for aircraft scheduling and routing. The flow of information is two-way, with pilots advising of volcanic eruptions. This is an important aspect as volcanic ash clouds can reach aircraft cruising altitude within minutes, and pilots may be among the first to be able to report large eruption columns.
This Prac consists of this sheet, an answer sheet, the poster mentioned above, and four papers below. At the completion of this Prac you should understand;
(i) the importance of volcanic ash for aviation
(ii) how the process works for advising the aviation industry of volcanic activity
(iii) a scenario-based approach informing on volcanic ash hazard at Wellington, posed by an eruption in the Tongariro volcanic centre.
Activity
1. Settling rate of particles in a fluid
Stokes Law describes the settling rate of a sphere of known density in a static fluid of known density. It can be described as;
Vs = (2/9*gR2)(ds-df)/µ, where g=acceleration due to gravity (m/s), R=particle radius (m), ds=density of the sphere (kg/m3), df=density of the fluid (kg/m3) and µ=dynamic viscosity of the fluid (Ns/m2).
Fortunately, with a few assumptions this simplifies readily. Assumptions are;
Particles are pure quartz (density 2650 kg/m3), the air at -25C has a density of 1.423 kg/m3, and the dynamic viscosity of the air at that temperature=1.488 Ns/m2. The equation collapsed and simplified for these conditions is;
Vs=3876R2.
--> Produce a table of settling velocity for particles with radii of 0.002, 0.02, 0.2, 2, 5, 8, 9, 10, 20, 30, 40, 50 and 60 mm. Complete a third column for time for these particles to fall 10 km.
Describe one factor which might slow the rate of particle descent, and one factor which might increase the rate of particle descent.
2. Eruption of a volcanic centre
Tongariro erupted recently. Assume that the volcano's eruption was short-lived, producing an eruption column that reached 10 km altitude within 2 minutes, and then the volcano stopped. The bustling metropolis of Wellington, the nation's capital, lies ~300 km south of Tongariro. Assume that there is a 30 km breeze blowing to the south at an altitude of 10 km and that it will therefore take 10 hours for the leading edge of an ash plume to reach the airspace above Wellington.
--> What is the largest diameter particle that might fall on Wellington? Show any working.
3. Aviation alert
Would you issue an aviation alert 24 hours after the eruption? Justify your answer with reference to the location of the alert and the maximum size of the particles. Assume meteorological conditions remain the same.
References
1. Pieri et al (2002) describes the damage to an aircraft from the encounter with ash from Iceland's Hekla volcano.
2. Simpson et al. (2002) overviews an eruption of Mt Cleveland, Alaska, and how the combination of meteorology, remote sensing and modelling contribute to understanding this peril. The paper also outlines the local response and some of the problems managers face.
3. Tupper et al. (2004) describe a range of ash-aircraft interactions in the western Pacific. They present a good summary of how the international warning network (summarised above) works.
4. Webley et al. (2011) describes modelling of ash-aircraft encounters, focussing on the Redoubt-KLM incident where a 747 came very close to an unplanned encounter with terrain.
5. Volcanic ash poster. www.bom.gov.au/info/vaac/publications/vapostermedium.jpg