Local scour at isolated obstacles on river beds Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/j6731597d

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • Maximum equilibrium scour depths, equilibrium scour volumes, and induced equilibrium movements at isolated obstacles on river beds were investigated in clear-water scour. The research was achieved by a systematic flume study based on the results of dimensional analysis of local scour. The main tested obstacles for local scour were cubes. Local scour at a circular cylinder of aspect ratio 1 and a sphere were also examined for comparison with scour at cubes. Each obstacle was placed on a flat movable bed and oriented normal to the incident flow. Non-cohesive uniform medium sand and very fine gravel were used as movable beds. The tested flow conditions were controlled to give many combinations of the relevant dimensionless parameters for local scour: the flow Froude Number, relative obstacle size, and relative roughness of bed material. Water surface profiles and longitudinal velocity profiles along the plane of symmetry, as well as the horizontal velocities near the bed around isolated obstacles on a fixed bed were examined in several runs. For a slightly submerged cube, the path of maximum velocity downstream of the cube moves from the water surface into the lower part of the flow. At a greater distance downstream, the path of maximum velocity tends to move upward toward the water surface. An increase of flow Froude Number leads to a hydraulic jump behind the cube. The relative longitudinal velocity near the bed is increased in this region. The decrease of relative water depth or the increase of flow Froude Number can lead to increased average relative horizontal velocity (V/u) near a cube. The cube has the highest average V/u value, as compared to flow near a circular cylinder and a sphere. The local scour processes and equilibrium scour patterns at isolated cubes on movable beds were also examined. There is not a unique equilibrium scour pattern for clear-water scour at a cube on a movable bed. Equations were developed to predict the maximum equilibrium scour depth and scour volume and the critical condition for incipient motion of bed material at a cube in clear-water scour. As the water becomes relatively deep, the shape effect of the circular cylinder and the sphere become negligible. The major equilibrium movement of a cube on a movable bed due to scour involves longitudinal displacement, vertical settlement, and longitudinal inclination. Equations were developed to predict the equilibrium movement and the critical condition for incipient upstream movement of a cube in clear-water scour.
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Non-Academic Affiliation
Subject
Rights Statement
Peer Reviewed
Language
Digitization Specifications
  • File scanned at 300 ppi (Monochrome, 24-bit Color) using Capture Perfect 3.0 on a Canon DR-9050C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-02-19T22:04:36Z (GMT) No. of bitstreams: 1 HuangChengChang1991.pdf: 8254011 bytes, checksum: aa583f4786d7dbd78f9365d5584c2536 (MD5)
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-03-05T18:37:12Z (GMT) No. of bitstreams: 1 HuangChengChang1991.pdf: 8254011 bytes, checksum: aa583f4786d7dbd78f9365d5584c2536 (MD5)
  • description.provenance : Submitted by Kirsten Clark (kcscannerosu@gmail.com) on 2013-02-19T21:58:32Z No. of bitstreams: 1 HuangChengChang1991.pdf: 8254011 bytes, checksum: aa583f4786d7dbd78f9365d5584c2536 (MD5)
  • description.provenance : Made available in DSpace on 2013-03-05T18:37:12Z (GMT). No. of bitstreams: 1 HuangChengChang1991.pdf: 8254011 bytes, checksum: aa583f4786d7dbd78f9365d5584c2536 (MD5) Previous issue date: 1990-08-30

Relationships

In Administrative Set:
Last modified: 08/04/2017

Downloadable Content

Download PDF
Citations:

EndNote | Zotero | Mendeley

Items