1988 Fiscal Year Final Research Report Summary
Hydraulic Study on the Backwashing of Multi-Media Filter
| Project/Area Number |
62550394
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
都市工学・衛生工学
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| Research Institution | Hokkaido University |
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Principal Investigator |
TAKAKUWA Tetsuo Fac. of Engineering, Hokkaido University, 工学部, 教授 (60001153)
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| Co-Investigator(Kenkyū-buntansha) |
FUNAMIZU Naoyuki Fac. of Engineering, Hokkaido University, 工学部, 講師 (10113622)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Multi-media filter / Backwashing / Fluidized bed concentration formula / Fluidized mixed layer / Mixing starting-up velocity / 成層現象 |
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| Research Abstract |
The grains of multi-media water filters are cleansed by backwashing at a water rate sufficient to fluidize the entire bed without mixing one another, and thereafter settle to constitute the bed with keeping the same order of stratification as in backwashing. Regarding backwashing as a binary or ternary solid liquid fluidized bed, the superficial water velocity must be (1)greater than the minimum fluidizing velocity of grain,(2)less than the terminal velocity of grain,(3)less than the velocity at which bulk density of the heavier and smaller grain's layer is equal to that of the lighter and larger grain's layer and (4)less than the velocity at which mixing of different kinds of grains begins.
For the limits (1) and (2), the existing formulae are available.
In this project,calculation methods and equations for the critical velocities were developed to obtain grains satisfying the limits (3) and (4). Their validity was comfirmed experimentally.
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