The response of backflow at the inlet of an inducer to the flow rate fluctuation is studied by using three-dimensional numerical calculations based on the turbulence model for the discussion of its effect on cavitation instabilities. It is first shown that the size of the backflow region can be correlated with the angular momentum in the upstream and the phase of the backflow significantly delays behind the quasi-steady response even at a very low frequency. It is then shown that the conservation relation of angular momentum is satisfied with minor effects of the shear stress on the boundary. The supply of the angular momentum by the negative flow is shown to be quasi-steady due to the fact that the pressure difference across the blade causing the backflow is quasi-steady at those frequencies examined. A response function of the angular momentum in the upstream to flow rate fluctuation is derived from the balance of the angular momentum and the results of the numerical calculations. This clearly shows that the backflow responds to the flow rate fluctuation as a first-order lag element. The effects of the backflow cavitation on cavitation instabilities are discussed assuming that the delay of cavity development is much smaller than the delay of the backflow. It was found that the backflow cavitation would destabilize low frequency disturbances due to the effects of the positive mass flow gain factor but stabilize high frequency disturbances due to the effect of the cavitation compliance.
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e-mail: horiguti@me.es.osaka-u.ac.jp
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March 2007
Technical Papers
Response of Backflow to Flow Rate Fluctuations
Xiangyu Qiao,
Xiangyu Qiao
Graduate School of Engineering Science,
Osaka University
, Toyonaka, Osaka 560-8531, Japan
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Hironori Horiguchi,
Hironori Horiguchi
Graduate School of Engineering Science,
e-mail: horiguti@me.es.osaka-u.ac.jp
Osaka University
, Toyonaka, Osaka 560-8531, Japan
Search for other works by this author on:
Yoshinobu Tsujimoto
Yoshinobu Tsujimoto
Graduate School of Engineering Science,
Osaka University
, Toyonaka, Osaka 560-8531, Japan
Search for other works by this author on:
Xiangyu Qiao
Graduate School of Engineering Science,
Osaka University
, Toyonaka, Osaka 560-8531, Japan
Hironori Horiguchi
Graduate School of Engineering Science,
Osaka University
, Toyonaka, Osaka 560-8531, Japane-mail: horiguti@me.es.osaka-u.ac.jp
Yoshinobu Tsujimoto
Graduate School of Engineering Science,
Osaka University
, Toyonaka, Osaka 560-8531, JapanJ. Fluids Eng. Mar 2007, 129(3): 350-358 (9 pages)
Published Online: August 31, 2006
Article history
Received:
November 7, 2005
Revised:
August 31, 2006
Citation
Qiao, X., Horiguchi, H., and Tsujimoto, Y. (August 31, 2006). "Response of Backflow to Flow Rate Fluctuations." ASME. J. Fluids Eng. March 2007; 129(3): 350–358. https://doi.org/10.1115/1.2427081
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