Investigation About Uncertain Metastable Conditions in Cavitating Flows

2016 ◽  
pp. 91-118
Author(s):  
Pietro Marco Congedo ◽  
Maria Giovanna Rodio ◽  
Gianluca Geraci ◽  
Gianluca Iaccarino ◽  
Remi Abgrall
Keyword(s):  
Cavitating Flows

A ROBUST NUMERICAL METHODOLOGY FOR STEADY-STATE CAVITATING FLOWS

2020 ◽  
Vol 32 (1) ◽  
pp. 61-79
Author(s):  
Vinay Kumar Gupta ◽  
Alok Khaware ◽  
K. V. S. S. Srikanth ◽  
Jay Sanyal
Keyword(s):  
Steady State ◽  
Cavitating Flows

scholarly journals Backflow effects on mass flow gain factor in a centrifugal pump

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042199886
Author(s):  
Wenzhe Kang ◽  
Lingjiu Zhou ◽  
Dianhai Liu ◽  
Zhengwei Wang
Keyword(s):  
Centrifugal Pump ◽  
Mass Flow ◽  
Flow Rate ◽  
Low Frequency ◽  
Gain Factor ◽  
Low Flow ◽  
Cavity Volume ◽  
Cavitating Flows ◽  
Inlet Tube ◽  
Low Flow Rate

Previous researches has shown that inlet backflow may occur in a centrifugal pump when running at low-flow-rate conditions and have nonnegligible effects on cavitation behaviors (e.g. mass flow gain factor) and cavitation stability (e.g. cavitation surge). To analyze the influences of backflow in impeller inlet, comparative studies of cavitating flows are carried out for two typical centrifugal pumps. A series of computational fluid dynamics (CFD) simulations were carried out for the cavitating flows in two pumps, based on the RANS (Reynolds-Averaged Naiver-Stokes) solver with the turbulence model of k- ω shear stress transport and homogeneous multiphase model. The cavity volume in Pump A (with less reversed flow in impeller inlet) decreases with the decreasing of flow rate, while the cavity volume in Pump B (with obvious inlet backflow) reach the minimum values at δ = 0.1285 and then increase as the flow rate decreases. For Pump A, the mass flow gain factors are negative and the absolute values increase with the decrease of cavitation number for all calculation conditions. For Pump B, the mass flow gain factors are negative for most conditions but positive for some conditions with low flow rate coefficients and low cavitation numbers, reaching the minimum value at condition of σ = 0.151 for most cases. The development of backflow in impeller inlet is found to be the essential reason for the great differences. For Pump B, the strong shearing between backflow and main flow lead to the cavitation in inlet tube. The cavity volume in the impeller decreases while that in the inlet tube increases with the decreasing of flow rate, which make the total cavity volume reaches the minimum value at δ = 0.1285 and then the mass flow gain factor become positive. Through the transient calculations for cavitating flows in two pumps, low-frequency fluctuations of pressure and flow rate are found in Pump B at some off-designed conditions (e.g. δ = 0.107, σ = 0.195). The relations among inlet pressure, inlet flow rate, cavity volume, and backflow are analyzed in detail to understand the periodic evolution of low-frequency fluctuations. Backflow is found to be the main reason which cause the positive value of mass flow gain factor at low-flow-rate conditions. Through the transient simulations of cavitating flow, backflow is considered as an important aspect closely related to the hydraulic stability of cavitating pumping system.

scholarly journals Energy Harvesting in Microscale with Cavitating Flows

ACS Omega ◽  
2017 ◽  
Vol 2 (10) ◽  
pp. 6870-6877 ◽  
Author(s):  
Morteza Ghorbani ◽  
Ali Mohammadi ◽  
Ahmad Reza Motezakker ◽  
Luis Guillermo Villanueva ◽  
Yusuf Leblebici ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Cavitating Flows

Transcritical Patterns of Cavitating Flow and Trends of Acoustic Level

2001 ◽  
Vol 123 (4) ◽  
pp. 850-856 ◽  
Author(s):  
Wei Gu ◽  
Yousheng He ◽  
Tianqun Hu
Keyword(s):  
Liquid Flow ◽  
High Speed ◽  
Cavity Flow ◽  
Periodic Flow ◽  
Cavitating Flows ◽  
Cavitation Noise ◽  
Cloud Cavitation ◽  
Three Stages ◽  
Cavity Shedding ◽  
Axisymmetric Bodies

Hydroacoustics of the transcritical cavitating flows on a NACA16012 hydrofoil at a 2/5/8-degree angle of attack and axisymmetric bodies with hemispherical and 45-degree conical headforms were studied, and the process of cloud cavitation shedding was observed by means of high-speed cinegraphy. By expressing the cavitation noise with partial acoustic level, it is found that the development of cavitation noise varies correspondingly with cavitation patterns. The instability of cavitation is a result of cavity-flow interaction, and is mainly affected by the liquid flow rather than by the cavitation bubbles. A periodic flow structure with a large cavitation vortex is observed and found to be responsible for inducing the reentrant-jet and consequent cavitation shedding, and explains the mechanism of periodic cavitation shedding from a new viewpoint. New terms for the three stages, growing, hatching and breaking, are used to describe the process of cavity shedding.

scholarly journals Simulation of Cavitating Flows in Diesel Injectors

1999 ◽  
Vol 54 (2) ◽  
pp. 223-226 ◽  
Author(s):  
M. Von Dirke ◽  
A. Krautter ◽  
J. Ostertag ◽  
M. Mennicken ◽  
C. Badock
Keyword(s):  
Cavitating Flows
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