Proceedings of the 11th International Conference

on Hydrodynamics (ICHD 2014)

October 19 – 24, 2014Singapore
Editors: TAN Soon Keat, WANG Xikun, GHO Wie Min & Joy CHUA

Session Papers (121-123)

121.  The Experiment Investigation of Large Scale of Turbulent flow in the Channel Bottom Layer Using DPIV.

Z. Huang, J. Gong, H.Q. Su, H.W. Wang.

China Academy of Aerospace Aerodynamic, Beijing, 100074, China.

Abstract :

The observation experiment of turbulent flow tripped in the channel bottom layer was performed by using dual frame straddling CCD(Charge Coupled Device) cameras DPIV(Digital Particle Image Velocimetry) system. Enormous data obtained from the experiment, the spatial structure and evolution characteristics of turbulence transverse vortex, turbulent velocity profile, ejection and sweep in the channel bottom were acquired. The physical mechanism of turbulent structure can be quantitatively explained by flow visualization. The result indicated that instantaneous velocity profile, sweep and ejection have direct physical relation with the evolution of clockwise transverse vortex. In the turbulent flow field near the bottom of channel, there exist clockwise transverse vortexes.  Sweep and ejection exist within transverse vortex and affect local instantaneous velocity profile to form inflexion point. On the one hand, sweep will reduce the position of inflexion point and is above inflexion point; on the other hand, ejection will increase the position of inflexion point and is under inflexion point. In the central core of transverse vortex, turbulence kinetic energy and shear stress is relatively small. But, on the margins of transverse vortex, turbulence kinetic energy and shear stress is relatively high. The result also showed that DPIV can not only provide a qualitative and quantitative and credible observation means but also be suitable for the observation experiment of turbulent flow in the channel bottom layer. For many turbulent phenomena, DPIV can give can give direct and intuitionistic physics explanation.

122.  To investigate the techniques of gas bubble detection in pore water for shallow subsoil conditions.

Raymond C.M. Ching.

School of Science and Technology, SIM University, 461 Clementi Road, Singapore 599491.

Abstract :

Soil is a complex natural material. The seabed condition varies fromplace to place, or even spot to spot within an area which could be due to the change in geological formation or presence of other seabed structures/activities. The stability of the spud can of Jack up legs is dependent upon the soil compaction. It has been also shown that the degree of water saturation and compressibility of soil will affect the amount of air bubble generation. At the same time, the amount of air bubbles has indicated the time variation pressure loading contributes to soil deformation, fluidization and hydraulic failure, as well as liquefaction. The basic principle ultrasonic wave concept has been visited. The ultrasonic sensing is commonly used in clinical applications and crack detection in metal/alloy. However, it has tremendous potential to detect air bubbles in submerged soil. The introduction to the ultrasonic sensing of the air bubbles in submerged soil can pioneer the research in shallow water oil drilling. It is also not surprising to see portable Magnetic Resonance Imaging (MRI) technology being used on soil deformation investigation in near future.

123.  Physical hydraulic modelling of controlling foaming at cooling water outfall.

Z.Q. Wang, S.P. Lim, Y.Y. Neoh, Mohd Nor Ahmad, Fauzan Kamal.

G&P Water (Singapore) Pte Ltd, Singapore.

Abstract :

Excessive foam is generated and dispersed in the vicinity of the coastal cooling water outfall. The operator intends to minimize the foam pollution and its dispersion as part the effort in improving the overall environment. The objective of this study is to test various solutions based on physical and numerical modeling works. The physical model was constructed in the scale of 1: 6. The discharged cooling water was pumped directly into the model and the foaming phenomenon at the outfall is reproduced. Structural, mechanical and chemical measures were tested in the model and the results shows the orifice structure is the most effective option among the proposed solutions. Computational Fluid Dynamic (CFD) modeling was carried out to serve as a cross-checking measure with the physical model and to further optimize the orifice configuration.