Abstract
This paper presents the results of an experimental study on a pulsating turbulent flow through conical diffusers with total divergence angles (2θ) of 12, 16, and 24, whose inlet and exit were connected to long straight pipes. To examine the effects of the divergence angle and the nondimensional frequency on flow characteristics, experiments were systematically conducted using a hot-wire anemometry and a pressure transducer. Moreover, the pressure rise between the inlet and the exit of the diffuser was analyzed approximately under the assumption of a quasi-steady flow and expressed in the form of simple empirical equations in terms of the time-mean value, the amplitude, and the phase difference from the flow rate variation. The expressions are in good agreement with the experimental results and very useful in practice. With the increase in the Womersley number, α, and 2θ, the sinusoidal change in the phase-averaged velocity, W, with time becomes distorted, and the W distributions show a more complicated behavior. For the flow at α=10 in the diffusers with large 2θ, the distributions of W are depressed on the diffuser axis. In contrast, for the flow at α=20, W has a protruding distribution on the diffuser axis.
Highlights
The objective of this study is experimentally investigating the characteristics of an unsteady turbulent flow in diffusers
We examine the flow behaviors of the pressure and velocity distributions and clarify the effects of the divergence angle and the unsteady flow parameters on them
For steady flow, the kinetic energy of the flow converts into pressure, and the static pressure rises in the downstream direction
Summary
The objective of this study is experimentally investigating the characteristics of an unsteady turbulent flow in diffusers. To this end, we consider a volume-cycled pulsating flow as the subject of the flow problem and carry out pressure and velocity measurements for conical diffusers with divergence angles (2θ) of 12°, 16°, and 24°. The flow in diffusers is an important flow problem in fluid engineering. They have been actively studied for over half a century [1, 2]. In the studies performed until the 1980s, the recovery efficiency of the pressure, the flow loss in the diffuser geometries, and the effects of the inlet conditions on their characteristics were examined comprehensively. In the studies, the inlet flow to the diffusers was steady
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More From: International Journal of Fluid Mechanics & Thermal Sciences
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