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Experimental Investigation of Flow Pattern around Pile Groups (two piles)

Aslani-kordkandi, Abolfazl | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40621 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ataie-Ashtiani, Behzad
  7. Abstract:
  8. The occurrence and development of scour hole around bridge pier are the main causes of bridge destruction. To predict manner, occurrence, development and final situation of scour hole around pier is the most important in the hydraulic design of bridges. A large number of studies have been performed to estimate the scour depth around piers at simplified laboratory conditions. The available equations from these studies do partly not present acceptable solutions. This issue is especially of great importance to the pile groups. For accurate determination of scour depth, it is required to get a better understanding of the flow and governing mechanism around pier. Although the flow pattern investigations were performed a lot around a single pier, there are few studies around pile groups. It is difficult to analyze the flow around piers theoretically, therefore, the accurate measurements of the flow around these structures can aid to aforementioned issue. The present study contains results of the experiments on the flow pattern around two-circular piers situated in side-by-side and tandem arrangement in two conditions (rigid rough bed for both arrangements and equilibrium scour hole for side-by-side arrangement) measured by an acoustic Doppler velocimeter (ADV) under a clear-water scour condition. Scour hole was frozen by synthetic glue to facilitate performance of the experiments. Experiments were conducted for the approaching flows -depend on the experiment stages- having undisturbed flow depth (=0.26-0.325m) and depth-averaged approaching flow velocities )=0.33-0.359 m/s) about 95% of the critical velocity of the uniform bed sand that had a median diameter of 0.71 mm and piers diameter of 91 mm. The contours of the time-averaged velocities components, turbulence intensities, and Reynolds stresses at different horizontal and vertical planes are also presented. Furthermore, streamlines obtained from the velocity fields are used to show the interaction of horseshow and wake vortex structures of piers to each other are presented and the bed shear stress was estimated at some vertical sections. Additionally, the frequency and power of vortex shedding were calculated by spectral analysis. A complete study around single pier was performed for comparison with the results of aforesaid studies. These experiments were carried out approximately at flow-depth Reynolds number of 100000.
  9. Keywords:
  10. Flow Patterns ; Scour Hole ; Turbulent Flow ; Side-by-Side Pier ; Tandom Pier

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