[섬유] Simulating Cavitation and Hydraulic Flip Inside Hydroentangling Nozzles 출판일 : 2004.04.01 저자 : H. Vahedi Tafreshi, B. Pourdeyhimi 서지사항 : Textile Research Journal, Volume 74, Issue 4, 359 페이지 등록일 : 2012.02.13 I 조회수 : 72 작성자 : admin |
Hydroentangling owes its success to the peculiar properties of coherent water jets. For
hydroentangling to be feasible at higher pressures, it is extremely important that water jets
maintain their collimation for an appreciable distance downstream of the nozzle. How ever,
water-jet breakup accelerates at high pressures. Recent studies have shown that cavitation
severely affects the integrity of high-pressure water jets. Investigating cavita tion
experimentally is not trivial. Computational fluid dynamics simulations offer appro priate tools
as a first step. This paper discusses the results of an unsteady-state simulation, which
shows the inception and time-evolution of a cavitation cloud inside a hydroentan gling
nozzle. Under certain conditions, the cavity cloud extends to the nozzle outlet, resulting in
the so-called hydraulic flip. Once hydraulic flip occurs, cavitation suddenly vanishes
because the downstream air moves upward into the nozzle and fills the cavity. This air
envelops the water flow inside the nozzle, which results in the depletion of cavitation-
induced instabilities from the jet surface and elongates the jet breakup length. Moreover,
our simulations reveal the approximate time scales of cavity growth through the nozzle. This
information is highly relevant for experimental visualization of nozzle cavitation. The
discharge and velocity coefficient obtained from the simulation are in a good agreement with
published experimental data.
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