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Session A4- New turbulence parameter for fish passage habitat

Abstract
Turbulence is a complex subject that is often defined by various definitions dependent on topic of interest or application. In its basic form, turbulence describes velocity fluctuations within the velocity field. In fish passage and habitat applications, these fluctuating velocities can have a significant effect on fish. Turbulence can inhibit or prevent fish from swimming in certain areas and high intensity turbulence can cause disorientation. The size scale of turbulence is of critical importance. Small scale turbulence has little effect on fish but high shear flows can potentially damage fish. To quantify turbulence, three different categories of turbulence are defined as well as their respective effect on fish. Current methods of evaluating turbulence in fish passage include the energy dissipation factor (EDF), root mean square (RMS), and the turbulence intensity factor. Each method is described and their strengths and weaknesses outlined. A new turbulence parameter is developed termed the average-vector method. The average vector method incorporates velocity magnitude, acceleration and the change in flow direction into a single value at a given point in the flow. For field application, it is believed that the average-vector method coupled with standard statistical methods provides a better measure of turbulence in fish passage/habitat than the existing methods. The resulting dimensions of the average-vector method is L/T2; an acceleration. Potentially, there could be a correlation between Newton's second law (F = ma) and the average-vector method indicating that fish turbulence is related to a fluctuating force acting on the fish.
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Date
2011-06-28
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