• 설비공학논문집
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• 제17권11호
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• pp.1035-1042
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• 2005

In the present study, the principle of minimum energy is employed to configure the shape of rivulet flowing down an inclined surface. The profile of laminar rivulet is determined by numerical integration. The maximum center thickness, which corresponds to the minimum thickness of falling film, is found to exist regardless of liquid flow rate and is compared with the analytical and experimental data. At small liquid flow rate the center thickness of rivulet and its width increase almost linearly with flow rate. Once the center thickness of rivulet becomes very close to its maximum value, its growth rate retards abruptly. However the width of rivulet increases proportionally to the liquid flow rate and most part of its free surface is as flat as that of stable film. The growth rate of rivulet thickness with respect to liquid flow rate becomes larger at bigger contact angle. The width of rivulet increases rapidly with its flow rate especially at small contact angle, As the liquid-vapor interfacial shear stress increases, the center thickness of rivulet decreases with its flow rate, which is remarkable at small contact angle. However the effect of interfacial shear stress on the width of rivulet is almost negligible.

• Smart Structures and Systems
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• 제18권3호
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• pp.485-500
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• 2016

Stay cables in some cable-stayed bridges suffer large amplitude vibrations under the simultaneous occurrence of rain and wind. This phenomenon is called rain-wind-induced vibration (RWIV). The upper rivulet oscillating circumferentially on the inclined cable surface plays an important role in this phenomenon. However, its small size and high sensitivity to wind flow make measuring rivulet size and its movement challenging. Moreover, the distribution of the rivulet along the entire cable has not been measured. This paper applies the videogrammetric technique to measure the movement and geometry dimension of the upper rivulet along the entire cable during RWIV. A cable model is tested in an open-jet wind tunnel with artificial rain. RWIV is successfully reproduced. Only one digital video camera is employed and installed on the cable during the experiment. The camera records video clips of the upper rivulet and cable movements. The video clips are then transferred into a series of images, from which the positions of the cable and the upper rivulet at each time instant are identified by image processing. The thickness of the upper rivulet is also estimated. The oscillation amplitude, equilibrium position, and dominant frequency of the rivulet are presented. The relationship between cable and rivulet variations is also investigated. Results demonstrate that this non-contact, non-intrusive measurement method has good resolution and is cost effective.

• Wind and Structures
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• 제6권6호
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• pp.471-484
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• 2003

The rain-wind induced vibration of stays is a phenomenon discovered recently and not well explained yet. As it is influenced by a wide range of physical parameters (cable size and shape, wind speed, direction and turbulence, rain intensity, material repellency and roughness, cable weight, damping and pre-strain), this peculiar phenomenon is difficult to reproduce in laboratory controlled conditions. A successful wind tunnel experimental campaign, in which some basic physical quantities were measured, allowed an extensive analysis as to identify the parameters of the rain-wind induced excitation. The unsteady pressure field and water thickness around a cable model were measured under rainy-excited conditions. The knowledge of those parameters provided helpful information about the air-flow around the cable and allowed to clarify the physical phenomenon which produces the excitation.