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RESEARCH ON CONTINUOUS AND INSTANTANEOUS HEAVY GAS CLOUDS

Objective

TO INVESTIGATE, THE VARIABILITY IN INSTANTANEOUS RELEASES WHEN THE DISPERSION IS AFFECTED BY THE PRESENCE OF BUILDINGS AND OTHER OBSTACLES.

THE INTERCOMPARISON OF WIND TUNNELS IS INTENDEND TO VERIFY THE CONSISTENCY OF RESULTS BETWEEN THE DIFFERENT WIND TUNNELS TO BE ENGAGED IN THE PROJECT AND ALSO TO PROVIDE A VERIFICATION COMPARISON WITH FIELD EXPERIMENTS. IT WILL REQUIRE ALL THE WIND TUNNELS TO REPRODUCE THE SAME TWO CONTINUOUS RELEASES. THE MAIN PART OF THE EXPERIMENT WILL BE TO INVESTIGATE THE VARIABILITY BETWEEN REPEATS OF IDENTICAL INSTANTANEOUS RELEASES OF HEAVY GAS IN NOMINALLY SIMILAR ATMOSPHERIC CONDITIONS. THE SIGNIFICANT FEATURE OF THE EXPERIMENTS IS THAT A LARGE NUMBER, 50-100, OF REPEATS WILL BE MADE IN ORDER TO OBTAIN GOOD QUALITY STATISTICS. THIS IS PARTICULARLY IMPORTANT IN DETERMINING THE PROBABILITY OF OCCURENCE OF THE EXTREME VALUES OF THE POLLUTANT CONCENTRATION IN DIFFERENT PARTS OF THE GAS CLOUD, WHICH ARE A CRITICAL FEATURE OF HAZARD ANALYSIS. THE VARIABILITY CAN BE EXPEXTED TO DEPEND BOTH UPON THE RICHARDSON NUMBER OF THE RELEASED CLOUD, ITS INITIAL FORM AND THE DISPERSIVE INFLUENCES TO WHICH IT IS EXPOSED. THIS LATTER PARAMETER, THE DISPERSIVE INFLUENCE ACTING ON THE GAS CLOUD, CAN BE GREATLY AFFECTED BY THE PRESENCE OF WALLS, BUILDINGS AND OTHER OBSTACLES, ALL OF WHICH MAY BE PRESENT IN A REAL ACCIDENT. THE VARIABILITY EXPERIENCED OVER FLAT AND UNBROKEN TERRAIN WILL ALREADY HAVE BEEN THE SUBJECT OF AN EXPERIMENTAL STUDY. THE PRESENT EXPERIMENTAL PROGRAMME WILL THEREFORE EXAMINE THE EFFECTS OF WALLS, BUILDINGS AND OTHER OBSTACLES ON INSTANTANEOUSLY RELEASED GAS CLOUDS OVER A RANGE OF CLOUD RELEASE RICHARDSON NUMBERS.THE FIRST STAGE IN THE EXPERIMENTS WILL BE TO MODEL SOME OF THE THORNEY ISLAND FIELD TRIALS SO THAT SOME EVIDENCE OF THE REPRESENTATIVENESS OF INDIVIDUAL TRIALS WILL BE OBTAINED. THE SECOND STAGE WILL BE TO INVESTIGATE A WIDER RANGE OF CLOUD RELEASE RICHARDSON NUMBERS AND A GREATER VARIETY OF OBTRUCTIONS. IN PARTICULAR, CLOUD RELEASE RICHARDSON NUMBERS WILL BE EXTENDED TO COVER LOWER VALUES THAN WERE USED IN THE TRIALS SINCE IT IS AT THESE LOWER VALUES THAT THE HIGHEST DEGREES OF VARIABILITY CAN BE EXPECTED. THE PRECISE RANGE OF OBSTACLES AND BUILDING SHAPES TO BE USED WILL DEPEND UPON THE RESULTS OF THE INVESTIGATION IN PHASE 0 OF THE PROGRAMME, BUT THEY WILL INCLUDE A VARIETY OF TYPICAL BUILDING SHAPES AN BOTH STRAIGHT FENCES AND BUNDS.
BECAUSE OF THE LARGE NUMBER OF REPLICATE MEASUREMENTS THAT WILL BE TAKEN AT EACH SAMPLING STATION IN THE GAS CLOUD, THE TOTAL NUMBER OF SAMPLING STATIONS THAT CAN BE USED WILL HAVE TO BE LIMITED TO ABOUT FIVE OF SIX REPRESENTATIVE POINTS AT EACH TEST CONDITION.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Warren Spring Laboratory
Address
Gunnels Wood Road
SG1 2BX Stevenage
United Kingdom