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14 results on '"Liu, Minnan"'

4. Effects of Wetting–Drying Cycles on Strain–Stress Relationship from Triaxial Test of a Mudstone Mixture

Author

Zhen-Feng Qiu, J. Bai, Liu Minnan, Jun-Jie Wang, and Hui-Ping Zhang

Subjects
Materials science, Stress–strain curve, Soil Science, Geology, Geotechnical Engineering and Engineering Geology, Triaxial shear test, Stress (mechanics), Test material, Reservoir water, Architecture, Soil water, Axial strain, Wetting, Composite material
Abstract

Soils filled in or along bank of a large reservoir may be subjected to wetting–drying cycles induced by cyclic lowering and rising of reservoir water level. The wetting–drying cycles may affect the mechanical behaviors of the soils. This study focused on the effects of wetting–drying cycles on the strain–stress relationship from triaxial test of a mudstone mixture. Several consolidated drained triaxial tests with wetting–drying cycles were carried out. Experimental data indicates that the wetting–drying cycles may induce an increment of axial strain, Δe, and a decrement of deviator stress, Δ(σ1 − σ3). With increment of the number of cycles, N, the values of Δe and Δ(σ1 − σ3) are increasing along logarithmic curves. Both change rates of Δe and Δ(σ1 − σ3) are sharply dropping with increment of N value. Thus, the effects of wetting–drying cycles on the strain–stress relationship of test material are mainly concentrated on the period of first several cycles. Based on experimental data, several fitting equations, which may estimate the values of Δe, Δ(σ1 − σ3), change rates of Δe and Δ(σ1 − σ3), with increment of N value, were suggested.

Published
2018

5. Mean flow and turbulence structure in vertical slot fishways

Author

Liu, Minnan, Rajaratnam, Nallamuthu, and Zhu, David Z.

Subjects
Hydraulic engineering -- Research, Hydraulic measurements -- Research, Turbulence -- Research, Fishes -- Research, Engineering and manufacturing industries, Science and technology
Abstract

This paper presents the results of an experimental study on the mean and turbulence structures of flow in a vertical slot fishway with slopes of 5.06 and 10.52%. Two flow patterns existed in the fishway and for each one, two flow regions were formed in the pools: a jet flow region and a recirculating flow region. The mean kinetic energy decays rapidly in the jet region and the dissipation rate in most of the areas in the pool is less than 200 W/[m.sup.3]. For the jet flow, the nondimensional mean velocity profile across the jet agrees very well with that of a plane turbulent jet in the central part of the jet with some scatter near its boundaries. Its maximum velocity decays faster compared to a plane turbulent jet in a large stagnant ambient. The jet presents different turbulence structure for the two flow patterns and for each pattern, the turbulence characteristics appear different between the left and right halves of the jet. However, the turbulence characteristics show some similarity for each case. The normalized energy dissipation rate shows some similarity and has a maximum value on the center of the jet. The results are believed to provide useful insight on the turbulence characteristics of flow in vertical slot fishways and can be used to verify numerical models and also for guidance in the design of fishways in the future. CE Database subject headings: Fish habitats; Turbulence; Energy dissipation; Hydraulic structures; Water flow.

Published
2006

6. Turbulence structure of hydraulic jumps of low Froude numbers

Author

Liu, Minnan, Rajaratnam, Nallamuthu, and Zhu, David Z.

Subjects
Hydraulic engineering -- Research, Engineering and manufacturing industries, Science and technology
Abstract

Turbulence characteristics of hydraulic jumps with Froude numbers of 2.0, 2.5, and 3.32 are presented. A Micro Acoustic Doppler velocimeter was used to obtain measurements of the velocities, turbulence intensities, Reynolds stresses, and power spectra. The maximum turbulence intensities and Reynolds stress at any section were found to decrease rapidly from the toe of the jump towards downstream within the jump and then gradually level off in the transition region from the end of the jump to the friction dominated open channel flow downstream. The maximum turbulence kinetic energy at each section decreases linearly with the longitudinal distance within the jump and gradually levels off in the transition region. The Reynolds stress and turbulence intensities within the jump show some degree of similarity. The dissipative eddy size was estimated to vary from 0.04 mm within the jump to 0.15 mm at the end of the transition region. The dominant frequency is in the range from 0 to 4 Hz for both horizontal and vertical velocity components. CE Database subject headings: Hydraulic jump; Turbulence; Energy dissipation; Froude number.

Published
2004

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