Metallographic autopsies of full-scale ITER prototype cable-in-conduit conductors after full cyclic testing in SULTAN: III. The importance of strand surface roughness in long twist pitch conductors

Adding vertical ribs is recognized as a useful practice for reducing wind effects on cooling towers. However, ribs are rarely used on cooling towers in China since Chinese Codes are insufficient to support the design of rough-walled cooling towers, and an “understanding” hampers the use of ribs, which thinks that increased surface roughness has limited effects on the maximum internal forces that control the structural design. To this end, wind tunnel model tests in both uniform flow field with negligible free-stream turbulence and atmospheric boundary layer (ABL) turbulent flow field are carried out in this article to meticulously study and quantify the surface roughness effects on both static and dynamic wind loads for the purpose of improving Chinese Codes first. Subsequently, a further step is taken to obtain wind effects on a full-scale large cooling tower at a high Re, which are employed to validate the results obtained in the wind tunnel. Finally, the veracity of the model test results is discussed by investigating the Reynolds number (Re) effects on them. It has been proved that the model test results for atmospheric boundary layer flow field are all obtained in the range of Re-independence and the conclusions drawn from model tests and full-scale measurements basically agree, so most model test results presented in this article can be directly applied to the full-scale condition without corrections.

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The influence of model surface roughness on wind loads of the RC chimney by comparing the full-scale measurements and wind tunnel simulations

Wind and Structures ◽

10.12989/was.2013.16.2.137 ◽

2013 ◽

Vol 16 (2) ◽

pp. 137-156 ◽

Cited By ~ 2

Author(s):

Chern-Hwa Chen ◽

Cheng-Hsin Chang ◽

Yuh-Yi Lin

Keyword(s):

Surface Roughness ◽

Wind Tunnel ◽

Full Scale ◽

Wind Loads ◽

Model Surface

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Prototype Reynolds Number Vortex-Induced Vibration Tests on a Full-Scale Rigid Riser

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4037538 ◽

2017 ◽

Vol 140 (1) ◽

Cited By ~ 2

Author(s):

Decao Yin ◽

Halvor Lie ◽

Rolf J. Baarholm

Keyword(s):

Surface Roughness ◽

Reynolds Number ◽

Flow Regime ◽

Amplitude Ratio ◽

Flow Regimes ◽

Offshore Structures ◽

Full Scale ◽

Displacement Amplitude ◽

Small Scale ◽

Supercritical Flow

Slender offshore structures in deep water subjected to currents may experience vortex-induced vibrations (VIV), which can cause significant fatigue damage. Extensive experimental researches have been conducted to study the VIV in the past several decades. However, most of the experimental works have small-scale models and relatively low Reynolds number (Re)—“subcritical” or even lower Reynolds number regime. There is a lack of full understanding of the VIV in prototype Re flow regime. Applying the results with low Re to a full-scale riser with prototype Re might have uncertainties due to the scaling effects. In addition, the surface roughness of the riser is also an important parameter, especially in critical Re regime, which is the case for prototype risers. In the present study, two full-scale rigid riser models with different surface roughness ratios were tested in the towing tank of MARINTEK in 2014. Stationary tests, pure crossflow (CF) free oscillation tests, and forced/controlled motion tests were carried out. Several conclusions could be made: The drag coefficient is dependent on the Re number and surface roughness ratio. At critical and supercritical flow regimes, the displacement amplitude ratio is less sensitive to Re than that at lower Re. The displacement amplitude ratio in subcritical flow regime is significantly larger than that in critical and supercritical flow regimes. Two excitation regions for the ‘smooth riser’ and one excitation region for the “rough riser” are identified.

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Prototype Reynolds Number VIV Tests on a Full-Scale Rigid Riser

Volume 2: Prof. Carl Martin Larsen and Dr. Owen Oakley Honoring Symposia on CFD and VIV ◽

10.1115/omae2017-61415 ◽

2017 ◽

Cited By ~ 1

Author(s):

Decao Yin ◽

Halvor Lie ◽

Rolf J. Baarholm

Keyword(s):

Surface Roughness ◽

Reynolds Number ◽

Flow Regime ◽

Amplitude Ratio ◽

Flow Regimes ◽

Offshore Structures ◽

Full Scale ◽

Displacement Amplitude ◽

Small Scale ◽

Supercritical Flow

Slender offshore structures in deep water subjected to currents may experience vortex-induced vibrations (VIV), which can cause significant fatigue damage. Extensive experimental researches have been conducted to study the VIV in the past several decades. However, most of the experimental works have small-scale models and relatively low Reynolds number (Re) - ‘subcritical’ or even lower Reynolds number regime. There is a lack of full understanding the VIV in prototype Re flow regime. Applying the results with low Re to a full scale riser with prototype Re might have uncertainties due to the scaling effects. In addition, the surface roughness of the riser is also an important parameter, especially in prototype Re regime. In present study, two full-scale rigid riser models with different surface roughness ratios were tested in the towing tank of MARINTEK in 2014. Stationary tests, pure cross-flow (CF) free oscillation tests and forced/controlled motion tests were carried out. Several conclusions could be made: • The drag coefficient is dependent on the Re number and surface roughness ratio. • At critical and supercritical flow regimes, the displacement amplitude ratio is less sensitive to Re than that at lower Re. The displacement amplitude ratio in subcritical flow regime is significantly larger than that in critical and supercritical flow regimes. • Two excitation regions for the ‘smooth riser’ and one excitation region for the ‘rough riser’ are identified.

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