Validity of Generation System for Solitary Wave Boundary Layer

Abstract

The present study is concerning bottom boundary layer beneath solitary wave over smooth beds condition. A new generation system was proposed to generate an oscillatory motion similar to solitary wave in a closed conduit water tunnel using a mechanical system. This generation system facilitates easy measurement of periodical oscillatory motion to replace solitary wave motion with a sufficient tranquil period. The velocities were measured by using a Laser Doppler Veloci-meter (LDV) at 17 to 22 points in the vertical direction. The experiments were accomplished with different velocities under single and periodical oscillatory motion conditions and validations have been done in some various terms of experiment relevant to solitary wave boundary layer. A good agreement is achieved in validation of free stream velocity and also both single and periodical oscillatory motion measurements methods. Furthermore, validation of velocity distribution in time variation obtains a critical Reynolds number which has a good agreement with the finding of previous researchers.

Experimental Study on Transition to Turbulence in Solitary Wave Boundary Layer

“…In the present experiments, the instantaneous horizontal velocity was measured at 17-22 points in the vertical direction by LDV and at 10ms intervals over 50 wave cycles. The velocity measurement under single and continuous/periodical methods and the instantaneous velocity obtained from present experiment can be seen in the previous publication 3) . The current experiment conditions are summarized in Table 1.…”

“…Deviation with higher value than numerical laminar in the region closed to the bottom is caused by turbulence generation. It can be indicated by fluctuation which appears in the flow velocity 3) . As shown in Fig.…”

“…The detail explanation of generation system such as: general sketch, generation system mechanism was given in the previous publication 3) . Figure 1 illustrates the operational system of rotating disk in the experimental set-up.…”

“…And then, a series of experiments with R e range 2.8 x 10 4 to 2.0 x 10 6 had been accomplished by U-Shape oscillating water tunnel in the purpose of behavioral observation for laminar to turbulent flow beneath solitary motion 2) . Recently, a closed conduit generation system had been used to carry out solitary motion experiments and it is followed by validation 3) . As conclusions, the validation results of a closed conduit generation system show a good agreement with the previous studies 2)4) and this system can overcome difficulties of experimental facilities applied in the previous studies 1) 2) .…”

“…The present study is the next investigation of solitary wave boundary layer characteristics after successfully completion of a new generation system validation in some various criteria, such as: free stream velocity, single and periodical measurement, vertical velocity distribution and stability diagram 3) . Characterization of transition to turbulence in case of solitary wave will be our concern in this study.…”