1988 Fiscal Year Final Research Report Summary
Mixing Mechanism of Internal Hydraulic Jump
| Project/Area Number |
62550375
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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 |
Hydraulic engineering
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| Research Institution | Osaka University |
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Principal Investigator |
NAKATSUJI Keiji Osaka University, Associate Professor, 工学部, 助教授 (10029324)
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| Co-Investigator(Kenkyū-buntansha) |
MICHIOKU Kohji Kobe University, Associate Professor, 工学部, 助教授 (40127303)
MUROTA Akira Osaka University, Professor, 工学部, 教授 (50028924)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Internal Hydraulic Jump / Buoyant Surface Jet / Stratified Shear Flow / Turbulence Structure / Mixing / Turbulent Entrainment / 乱流モデル |
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| Research Abstract |
(1) Recirculating Roller Observed in Internal Hydraulic Jump
The hydraulic and turbulent mixing properties of an internal hydraulic jump were investigated in a two-layered flow system. Experimental results indicated that the internal jump was characterized by a recirculating roller flowed beneath the jump interface in the opposite direction to the internal jump flow. Although its origin was similar to the roller observed in an open channel hydraulic jump, the size and reverse flow rate of the recirculating roller were shown to be remarkably large. Besides, the roller made a large scale circulation form in connection with the jump flow because of the miscible density difference of two-layered fluids. Consequently, it directly prevented the internal jump from entraining ambient fluid. In spite of the existence of the characteristic recirculating roller, it had not been taken into consideration in analyzing an internal jump. A momentum principle model were presented in due consideration of
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the recirculating roller properties. This model was confirmed to predict the mixing properties of the internal jump as a function of the upstream densimetric Froude number reasonably, which had not been explained by any existing analytical model.
(2) Radial Internal Hydraulic Jump
The flow properties of a radial internal jump within a gradually expanding channel are examined treoretically and experimentally. The gradually expanding channel follows an example of an estuary geometry. The momentum principle is extended to the expanding sections of jump by assuming that the jump profile is parabolic in shape. Theoretical results are compared with experimental ones.
(3) Application of Algebraic Stress Model (ASM) to Plane Buoyant Surface Jet An algebraic stress model is developed to predict the behaviours of buoyant surface discharges for taking account of the damping effects of the gravitational field and the free surface on turbulence structure accurately. The ASM solution tested produces a good agreement with measurements on the flow development and turbulent entrainment of plane buoyant surface jets. Efforts to apply the ASM into an internal hydraulic jum are presently ongoing. Less
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