Complex rotation numbers: bubbles and their intersections

Heat transfer characteristics of a three-pass serpentine flow passage with rotation are experimentally studied. The walls of the square flow passage are plated with thin stainless-steel foils through which electrical current is applied to generate heat. The local heat transfer performance on the four side walls of the three straight flow passages and two turning elbows are determined for both stationary and rotating cases. The throughflow Reynolds, Rayleigh (centrifugal type), and rotation numbers are varied. It is revealed that three-dimensional flow structures cause the heat transfer rate at the bends to be substantially higher than at the straight flow passages. This mechanism is revealed by means of a flow visualization experiment for a nonrotating case. Along the first straight flow passage, the heat transfer rate is increased on the trailing surface but is reduced on the leading surface, due to the action of secondary streams induced by the Coriolis force. At low Reynolds numbers, the local heat transfer performance is primarily a function of buoyancy force. In the higher Reynolds number range, however, the circumferentially averaged Nusselt number is only a weak function of the Rayleigh and rotation numbers.

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Chain recurrence, growth rates and ergodic limits

Ergodic Theory and Dynamical Systems ◽

10.1017/s0143385707000363 ◽

2007 ◽

Vol 27 (5) ◽

pp. 1509-1524 ◽

Cited By ~ 5

Author(s):

FRITZ COLONIUS ◽

ROBERTA FABBRI ◽

RUSSELL JOHNSON

Keyword(s):

Lyapunov Exponents ◽

Growth Rates ◽

General Linear ◽

Chain Recurrence ◽

Hamiltonian Flows ◽

Rotation Numbers ◽

Linear Flows

AbstractAverages of functionals along trajectories are studied by evaluating the averages along chains. This yields results for the possible limits and, in particular, for ergodic limits. Applications to Lyapunov exponents and to concepts of rotation numbers of linear Hamiltonian flows and of general linear flows are given.

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Radar imaging for targets with complex rotation based on phase history decomposition

Multidimensional Systems and Signal Processing ◽

10.1007/s11045-012-0206-3 ◽

2012 ◽

Vol 25 (3) ◽

pp. 425-445 ◽

Cited By ~ 4

Author(s):

He Sisan ◽

Zhou Jianxiong ◽

Zhao Huining ◽

Fu Qiang

Keyword(s):

Radar Imaging ◽

Complex Rotation

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Heat Transfer in Rotating Serpentine Coolant Passage With Ribbed Walls at Low Mach Numbers

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4028905 ◽

2015 ◽

Vol 7 (1) ◽

Cited By ~ 7

Author(s):

Shang-Feng Yang ◽

Je-Chin Han ◽

Salam Azad ◽

Ching-Pang Lee

Keyword(s):

Heat Transfer ◽

Mach Number ◽

Reynolds Numbers ◽

Working Fluid ◽

Transfer Coefficients ◽

Low Mach Number ◽

Heat Transfer Coefficients ◽

Rotation Numbers ◽

Wide Range ◽

Mach Numbers

This paper experimentally investigates the effect of rotation on heat transfer in typical turbine blade serpentine coolant passage with ribbed walls at low Mach numbers. To achieve the low Mach number (around 0.01) condition, pressurized Freon R-134a vapor is utilized as the working fluid. The flow in the first passage is radial outward, after the 180 deg tip turn the flow is radial inward to the second passage, and after the 180 deg hub turn the flow is radial outward to the third passage. The effects of rotation on the heat transfer coefficients were investigated at rotation numbers up to 0.6 and Reynolds numbers from 30,000 to 70,000. Heat transfer coefficients were measured using the thermocouples-copper-plate-heater regional average method. Heat transfer results are obtained over a wide range of Reynolds numbers and rotation numbers. An increase in heat transfer rates due to rotation is observed in radially outward passes; a reduction in heat transfer rate is observed in the radially inward pass. Regional heat transfer coefficients are correlated with Reynolds numbers for nonrotation and with rotation numbers for rotating condition, respectively. The results can be useful for understanding real rotor blade coolant passage heat transfer under low Mach number, medium–high Reynolds number, and high rotation number conditions.

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