Forecasting of a zone of emergency flood of mineral oil |
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Procedure is intended for the simultaneous decision of two tasks: determination of volume of the mineral oil which have flowed out as a result of accident from the pipeline and construction of a zone of flood of mineral oil, corresponding to the flowed out volume. Forecasting of a spread zone of mineral oil is made on the basis of data on a land relief and volume of the flowed out oil. Thus, for functioning the task the presence of a matrix of heights of a relief in area of passage of an oil pipeline and data on characteristics of the pipeline and conditions of transportation of oil are necessary. For calculation and modelling it is necessary: - to prepare a map ; - to call onto execution an applied task «Forecasting of a zone of emergency flood of oil » (floodoil.dll); - to choose the pipeline on which there was an accident; - to specify a point of emergency break; - in dialogue to fill parameters missing for calculation ; - to press "Execute" button. According to a methodical manual of an estimation of risks on the main oil pipelines the amount of the oil which has poured out from the pipeline owing to accident, is defined from following expression: V = V1 + V2 + V3, Where, V - total amount of the flowed out oil; V1 - volume of the oil which has flowed out in a pressure mode, that is from the moment of damage up to a stop of downloading; V2 - volume of the oil which has flowed out in nonpressure mode, from the moment of a stop of downloading up to closing latches; V3 - volume of the oil which has flowed out from the moment of closing of latches up to the discontinuance of outflow (to the moment of arrival of emergency-reconstruction brigade or full unloading of cut off parts of the pipeline). For calculation of volume of the flowed out oil the characteristics of the pipeline, parameters of the pipeline work, time parameters of accident and a number of additional parameters are used. The part of parameters the program automatically reads out from a map from semantics of objects and from a matrix of heights of a relief. Modelling of a spread of a liquid is based on a principle of communicating vessels. Cells of a matrix of heights are served as elementary "vessels". The liquid is poured from one cell into another one and loses a part of volume due to an absorption and accumulation in local tanks (pits). When volume of the flowed liquid will be completely distributed on a surface the modelling of a zone stops. The result of modelling is saved in the matrix of qualities representing a volumetric body, corresponding to the liquid which was been distributed on a surface. Accuracy of modelling is defined by accuracy and quality of a matrix of heights. For modelling parameters are used: depth of a stream and thickness of a film of a spread (see parameters of procedure IDN_PARM). Depth of flood stream is specified in meters. The program uses the given parameter as wave height of a spreading stream of mineral oil. A real relief of land (as well as a matrix of heights) can have some unevenness of a surface ("protuberances" and "pits"). At modelling a spread some insignificant "protuberances" can become an absolute obstacle for a spreading liquid. However in a reality the spread has wavy character and can overswash through such "protuberances". Parameter - depth of a stream defines height of a wave (or the height of "protuberances" which can be ignored). Thickness of a spread film is specified in meters and defines thickness of an oil film remaining on surfaces. If to multiply the given parameter by area of the flooded region, we shall receive volume of the "absorbed" liquid. For example on fig.1, the volume of the "absorbed" liquid is equal to 0.001 m, the discreteness of an elementary cell is equal to 5 m, the "absorbed" volume is equal: 5 м * 5 м = 25 м2; 25 м2* 0,001 м = 0,025 м3 Thus, value of the liquid which have "absorbed" and accumulated in local "pits" is stored in cells of resulting matrixes of qualities.
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