Off-Design Performance Characteristics of Supercavitating Hydrofoils in Cascade

1970 ◽  
Vol 92 (4) ◽  
pp. 797-806
Author(s):  
R. Oba
Keyword(s):  
Lift Coefficient ◽  
Extreme Case ◽  
Flow Speed ◽  
Performance Characteristics ◽  
Inlet Flow ◽  
Design Performance ◽  
Kaplan Turbine ◽  
The Poor ◽  
Turbine Runner

The performance characteristics of supercavitating flapped foils in cascade, (such as the lift coefficient, the drag-lift ratio, and the limiting inlet flow speed) are calculated, for various cascade arrangements and flap angles, as well as flap-chord ratios, e. The extreme case when e = 1.0 corresponds simply to adjusting the cascade angle, such as in the Kaplan-turbine runner. It is found that the poor supercavitating cascade performance characteristics at conditions other than the designed condition, that is, the off-design performance characteristics, are noticeably improved with the use of flapped foils. The characteristics of cascaded foils without flaps, especially where there are no adjustments in cascade angle, make their use impractical in the off-design condition.

scholarly journals The Effect of Magnet-to-Coil Distance on the Performance Characteristics of EMATs

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5096
Author(s):  
Yutang Wu ◽  
Yunxin Wu
Keyword(s):  
Numerical Simulations ◽  
Conversion Efficiency ◽  
Performance Characteristics ◽  
Practical Application ◽  
Electromagnetic Acoustic Transducer ◽  
The Poor ◽  
Acoustic Transducer ◽  
Lift Off

The poor conversion efficiency and obvious lift-off effect of the electromagnetic acoustic transducer (EMAT) are commonly known to be problems for its practical application. For the purpose of enhancing the performance of EMATs, numerical simulations were performed in order to analyze the effect of various parameters. The results indicate that only the magnet-to-coil distance can effectively enhance the conversion efficiency and weaken the lift-off effect at the same time. When the magnet-to-coil distance is 2 mm, the lift-off effect will continue to be weakened as the magnet-to-coil distance increases, whereas the decrease of the lift-off effect is inconspicuous and the conversion efficiency starts to decline at this time. Therefore, to get the best performance of this specific EMAT, the suitable magnet-to-coil distance is 2 mm. The experiment effectively verifies the improvement of EMATs with a magnet-to-coil distance of 2 mm.

Unsteady multi-phase cavitation analysis on the effect of anti-cavity fin installed on a Kaplan turbine runner

2020 ◽  
Vol 162 ◽  
pp. 861-876
Author(s):  
Mohamed Murshid Shamsuddeen ◽  
Jungwan Park ◽  
Young-Seok Choi ◽  
Jin-Hyuk Kim
Keyword(s):  
Kaplan Turbine ◽  
Turbine Runner ◽  
Multi Phase

scholarly journals FEM MODELING OF FLUID FLOW FOR KAPLAN TURBINE RUNNER

2010 ◽  
Vol XIX (IX), 2010/3 (3) ◽  
Author(s):  
HORA Cristina ◽  
DUMITRESCU DănuÅ£ ◽  
HORA Horea
Keyword(s):  
Fluid Flow ◽  
Fem Modeling ◽  
Kaplan Turbine ◽  
Turbine Runner

scholarly journals Numerical Investigation of the Trailing Edge Shape on the Added Damping of a Kaplan Turbine Runner

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zhang Ming ◽  
P. A. Mbango-Ngoma ◽  
Du Xiao-zhen ◽  
Chen Qing-Guang
Keyword(s):  
Numerical Investigation ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Hydraulic Turbine ◽  
Vibration Level ◽  
High Excitation ◽  
Trailing Edge ◽  
Kaplan Turbine ◽  
Turbine Runner ◽  
The One

Hydraulic turbine runners experience high excitation forces in their daily operations, and these excitations may cause resonances to runners, which may induce high vibrations and shorten the runner's lifetimes. Increasing the added damping of runners in water can be helpful to reduce the vibration level during resonances. Some studies have shown that the modification of the trailing edge shape can be helpful to increase added damping of hydrofoils in water. However, the influence of blade trailing edge shape on the added damping of hydraulic turbine runners has been studied in a limited way before. Due to the difficulties to study this problem experimentally, the influence of blade trailing edge shape on a Kaplan turbine runner has been studied numerically in this paper and the one-way FSI method was implemented. The performances of three different turbulence models, including the k − ϵ , k − ω   SST , and transition SST models, in the added damping simulation of the NACA 0009 hydrofoil were evaluated by comparing with the available results of the two-way FSI simulation in the references. Results show that, unlike the significantly different performances in the two-way FSI method, the performances of all the turbulence models are very close in the one-way FSI method. Then, the k − ϵ turbulence model was applied to the added damping simulation of a Kaplan turbine runner, and results show that the modification of the blade trailing edge shape can be helpful to increase the added damping to some extent.

Biocultures: An Emerging Paradigm

PMLA ◽  
2009 ◽  
Vol 124 (3) ◽  
pp. 947-949 ◽  
Author(s):  
Jay Clayton
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Single Gene ◽  
Extreme Case ◽  
Emotional Control ◽  
Genetic Abnormality ◽  
Medical Experience ◽  
The Poor ◽  
Ian Mcewan ◽  
Single Sequence

Literature and Science Policy: A New Project for the HumanitiesThe misfortune lies with a single gene, in an excessive repeat of a single sequence—CAG. Here's biological determinism in its purest form. More than forty repeats of that one little codon, and you're doomed.—Ian McEwan, Saturday (94)Huntington's disease. Perowne, the neurosurgeon in Ian McEwan's novel Saturday (2005), readily diagnoses the genetic abnormality that afflicts a petty criminal who is assaulting him. It is like a tic with Perowne. He cannot stop himself from analyzing the biological causes of the poor emotional control, the violent temper, of the man who is mugging him. Perowne regards himself as a “professional reductionist,” a man of science who “can't help thinking it's down to invisible folds and kinks of character, written in code, at the level of molecules” (281). A lifetime of medical experience has led him to conclude that much of our behavior is dictated by biology. But Huntington's disease represents an extreme case. For someone with this condition, the “future is fixed and easily foretold” (94).

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