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Title: Stability of oscillatory laminar flow along a wall
Authors: United States. Army. Office of the Chief of Engineers
University of California, Berkeley
Li, Huon
Keywords: Sedimentation and deposition
Water waves
Laminar flow
Turbulent flow
Publisher: United States, Beach Erosion Board
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical memorandum (United States. Beach Erosion Board) ; no. 47.
Description: Technical Memorandum
From the Introduction: In 1883 Osborne Reynolds (1) first demonstrated qualitatively the characteristics of a turbulent flow by the following experiment which is still being used today. He introduced dye into the water which was flowing in a glass tube with a smooth entry. At a small rate of flow the filament of the dye extended down the tube in a straight line. As the rate of flow increased up to a certain stage, the straight line motion began to break down. The straight line motion is termed laminar, and the motion after breakdown is called turbulent. These two different types of flow appear also in boundary layer flow, jet flow, and many other cases. Laminar and turbulent flow are essentially different in character. For instance, the pressure gradient is proportional to the first power of the velocity for a laminar pipe flow, but approximately to the second power of the velocity for turbulent flow. The velocity distribution in a pipe section is parabolic if the flow is laminar, but approximately logarithmic if the flow becomes turbulent. The skin-friction of ships and airplanes also are different when the flow along their surface is turbulent and when it is laminar. In laminar flow the fluid particles acting as units are of molecular size, and the particles are constrained to motion in parallel paths by viscosity. In turbulent flow much larger masses of fluid move together as units, breaking down in time and mixing with other masses of fluid. The motion becomes very complicated, and it is impossible to predict the detail of the instantaneous flow pattern. However, important relationships of turbulent flow may be obtained by a statistical analysis of turbulent flow records. It is the randomness of the motion that distinguishes the turbulence from secondary flows and periodical wave motions.... .... The purpose of this thesis is to study the transition from laminar to turbulent flow in an oscillatory boundary layer near the solid bottom caused by a surface wave. However, the observations were made at a plate oscillating in still water for the sake of experimental convenience. The relationships between these two flow conditions are discussed, and the experimental results including the observation on both smooth and rough surfaces are given.
Rights: Approved for Public Release, Distribution is Unlimited
Appears in Collections:Technical Memorandum

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