Abstract An in situ suspension camera in combination with an image-analysis system was developed at NIOZ to measure the in situ particle size of suspended matter. It differs from other methods in that in sit particle size is measured from ∼ 4 μm upwards in a relatively simple and direct way. It can be used in any waters down to ∼ 4000 m depth (with some adjustments to 7000 m) and in water with a suspended matter concentration up to 200 mg·dm −3 . In very clear ocean water the system becomes inconvenient because of the large number of photographs that have to be taken to obtain a reliable size distribution. This paper describes the camera and the image-analysis system and gives some results of measurements in the Scheldt river and estuary in April 1989. These measurements show a continuous size distribution by volume between 3.6 μm and 644 μm and a good agreement of the data obtained with the 1:1 and 1:10 cameras.

In situ observation of flocs in natural waters

Wake-induced vibration of a circular cylinder at a low Reynolds number of 100

The south west coastal zone of Bangladesh have been affected by rampant water logging due to vulnerable climate, silted rivers and stumpy terrain; and introduction of IWRM and TRM at some places of the zone has substantially safeguarded the circumstance. This study aims to assess the benefits achieved due to implementation of IWRM in parts of Khulna and Jessore districts, and investigate some technical aspects evolving TRM. Analyses have been carried out using satellite images, RS and GIS technology, Digital Elevation Model (DEM) and field investigations. A mathematical formulation has been made to assess rate of tidal sedimentation due to TRM and selection strategies of tidal basins. The study comes up with evidences of considerable advancements in regional livelihood i.e. flood resistance, cultivated lands, cultivable area, cropping intensities and food security due to IWRM. Moreover, the technical facts established on TRM would help planners to have vivid perception regarding the process.

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Integrated Water Resources Management (IWRM) Impacts in South West Coastal Zone of Bangladesh and Fact-Finding on Tidal River Management (TRM)

The flow-induced vibration (FIV) of multiple cylinders is a common phenomenon in industry and nature. The FIV and energy harvesting of three circular cylinders in tandem are numerically studied by 2D-URANS simulations in Reynolds number range of 30,000 < Re < 105,000. Simulation results match well with experiments in the tested cases. Four branches of FIV are clearly captured in the amplitude and frequency ratio curves of the three cylinders with roughness, including initial branch of vortex-induced vibration (VIV), VIV upper branch, transition from VIV to galloping, and galloping. It is shown that the vortices from downstream cylinder are strongly disrupted and modified by vortices of upstream cylinder. The third cylinder is almost suppressed in VIV initial branch. The 2P vortex pattern is observed for the first cylinder in the VIV upper branch. For Re = 90,000 in the transition regime, the vortex patterns of the first and second cylinders are 2P + 4S and 2P + 2S, respectively. In the galloping branch, the shear layer motion is in synchronization with the motion of the cylinder, and the maximum amplitude of 2.8D is reached by the first cylinder. The total converted power of the three cylinders increases with U*water both in the simulation and experiment. For the three cylinders, the maximum power reaches up to 85.26 W with the increase of Reynolds number. The energy conversion efficiency is stable and higher than 35% in the starting region of VIV upper branch, and the maximum value of 40.41% is obtained when Re = 40,000.

Research on Flow-Induced Vibration and Energy Harvesting of Three Circular Cylinders with Roughness Strips in Tandem

Flow past a single stationary sphere, 2. Regime mapping and effect of external disturbances

https://pure.tue.nl/ws/files/148442182/1_s2.0_S1385894720306471_main.pdf

Open-cell foams as catalysts support : a systematic analysis of the mass transfer limitations

https://pure.tue.nl/ws/files/144699499/1_s2.0_S1385894719330566_main.pdf

Direct numerical simulation of a non-isothermal non-adiabatic packed bed reactor

Vortex-induced vibrations of three staggered circular cylinders are investigated via two-dimensional finite element computations. All the cylinders are of equal diameter (D) and are mounted on elastic supports in both streamwise (x−) and transverse (y−) directions. The two downstream cylinders are placed symmetrically on either side of the upstream body at a streamwise gap of 5D, with the vertical distance between them being 3D. Flow simulations are carried out for Reynolds numbers (Re) in the range of Re = 60-160. Reduced mass (m*) of 10 is considered and the damping is set to zero value. The present investigations show that the upstream cylinder exhibits initial and lower synchronization response modes like an isolated cylinder does at low Re. Whereas for both the downstream cylinders, the upper lock-in branch also appears. The initial and the upper modes are characterized by periodic oscillations, while the lower lock-in branch is associated with nonperiodic vibrations. The 2S mode of vortex shedding i...

Vortex-induced vibrations of three staggered circular cylinders at low Reynolds numbers

Suspended sediments deposition at estuary affects marine life in coastal ecosystem. Particle size distribution (PSD) is used to find settling velocity of suspended sediments. In this study, a new i...

Determination of suspended sediments particle size distribution using image capturing method

https://pure.tue.nl/ws/files/110034420/1_s2.0_S1385894718319600_main.pdf

Venu Chandra

Papers

Open-cell foams as catalysts support : a systematic analysis of the mass transfer limitations

Direct numerical simulation of a non-isothermal non-adiabatic packed bed reactor

Vortex-induced vibrations of three staggered circular cylinders at low Reynolds numbers

Determination of suspended sediments particle size distribution using image capturing method

Direct numerical simulation of hydrodynamic dispersion in open-cell solid foams