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Simulation of Flow and Sediment Transport in an Open Channel With Obstacle using IRIC NAYS2DH
No full textThis thesis is submitted to the Department of Civil Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Civil Engineering, May 2018.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 89-91).Hydraulic structures such as barbs, groins and spur dikes have been constructed in river bank
in order to deflect the flowing water away from vulnerable zone. They are made of stone,
gravel, rock, earth or piles, beginning at the river bank with a root and ending the regulation
line with a head. River flow mechanisms with the hydraulic structures need to be intensively
studied to protect the river bank from erosion, increase the bank stability, improve navigation
and flood control. Such structure also plays an important role to enrich the biodiversity of
different aquatic species by providing shelter them. The main objective of this thesis is to
simulate the straight channel with the presence of several types of such structures by using
2D numerical simulation model, iRIC Nays2DH. The groin like structures can be oriented
perpendicular or be inclined either upstream or downstream. Each orientation affects the
stream in a different way and shows different result in the vicinity of the groin. In chapter,
simulation of flow around groin, details of streamline variation, velocity vector and computed
recirculation around groin are shown for 45º, 90º and 135º groin. The length of recirculation
zone is found 1.2m, 1.04m and 1m, respectively. The simulated present study of velocity
profiles and shear stress profiles are compared with previous experimental and numerical
results. Good agreement is found for all of the cases. It is observed that predicted velocity
profiles and predicted bed shear stress profiles for 45º, 90º and 135º, the position of
maximum velocity and shear stress are found to be shifted towards downstream with
increasing y/l = 1, 1.5, 2, 3and 4, respectively. For all the cases, peak of the velocity and
shear stress are also deviated from upstream to downstream, 45º to 135º angled groin. From
the velocity contour and shear stress contour, it is found that left bank is higher velocity and
higher shear stress zone and right bank is lower velocity and lower shear stress zone. In
chapter, local scour around groin, to determine the variation of scour depth and sediment
deposition near the head of the groin, groins are orientated 45º, 90º and 135º at the upstream
of the channel. The comparison of velocity field, bed level contour results, Elevation of bed
profiles of 45º, 90º and 135º groin are given. Simulated present study are compared with
previous numerical results and good agreement are found. 45º, 90º and 135º groin are
simulated for 1 hour and 5 hours, respectively. After 5 hours, equilibrium scour is attended
and maximum scour depth for 45º, 90º and 135º are found as 0.065m, 0.062m and 0.054m,
respectively. In case of multiple groin, maximum scour are found 0.145m for discharge
0.035 m3/s and 0.24m for discharge 0.046 m3/s.. Bed deformation contour lines, velocity
vectors, transverse and longitudinal bed profiles are depict in this chapter. Computed
scouring are compared with previous experimental and numerical results. For discharge,
0.035 m3/s, scour at first spur dikes to third spur dikes are 0.123m, 0.005m and 0.005m,
respectively. Similarly, when discharge 0.046 m3/s, scour at first to third spur dikes are
0.16m, 0.01m and 0.012m, respectively. The model is also used to evaluate and analyze flow
patterns, streamline variation, velocity vector contour, vorticity, bed shear stress contour,
scour and sediment deposition around a groin like structure on a straight channel.
Most of the natural flow are three dimensional; for example, in case of meandering channel,
the flow passing through the bend is obviously of a three-dimensional (3D) nature because of
the generation of secondary current due to the centrifugal force. When a flow in an open
channel passes an obstacle ( such as groin), the deviation of flow causes the generation of
secondary current and flow become highly 3D. Therefore, a 3D hydrodynamic model is
necessary to accurately simulate the flows in a meandering channel. However, dealing with
the practical engineering problems, such as alluvial geomorphic process, it is not
computationally efficient to use 3D models. In such problems, a two-dimensional (2D) model
is generally used. To predict the applicability of iRIC software in a flow field with strong
secondary current, the model is also applied for 180º sharp and mildly bend. Water surface
elevation contour and velocity vector are evaluated from the simulation. For both cases, the
velocity of flow is greater in the inner section than the outer section. The results are
compared with previous experiment result and found well agreed with previous experiments.Masuma HaqueMaster of Science in Civil Engineerin
Effect of Surfactant on Formation of Hydroxyapatite under Reverse Micelle Condition
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Masters of Philosophy in Chemistry, December 2018.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 57-61).Hydroxyapatite, (HAp), Ca10(PO4)6(OH)2, is a naturally occurring material found in the inorganic component of human bone and enamel. The constituent elements of HAp are primarily calcium and phosphorous, with a stoichiometric calcium to phosphorous ratio is 1.667 capable of promoting intimate bone growth onto femoral implants. The performance, lifespan and quality of the resultant biological coating in vivo is largely dependent on the coating morphology, phase composition, particle size and crystallinity of the powders pre-coating application. The present study focused on preparing Hydroxyapatite nanoparticles (HAp-NPs) through chemical precipitation technique using mixed micelle core as a nanoreactor. Mixed micelle core was used to control morphology such as crystallinity, particle size, particle shape, particle size. Anionic (sodium dodecyl sulphate (SOS)) and cationic (Cetyl trimethyl ammonium bromide (CTAB)) surfactants were used to prepare the mixed micellar core. 18 : 2 ratio of
propanol-1 : water system experimentally selected for the formation of reverse micelle for the afore mentioned surfactants. Compositions of both surfactants were varied to control the morphology of HAp-NPs under the same experimental condition. Several techniques such as FTIR, XRD, TOA and SEM were used to characterize the prepared HAp-NPs. Appearance of peaks at various position of the FTIR spectrum shows the PO vibrations of PO;- which are characteristics of hydroxyapatite. In addition, the diffraction pattern of the prepared HAp-NPs are in well agreement with the standard published by the International Centre for Diffraction Data. However, the diffractogram indicates the presence of crystalline as well as amorphous phase. No significant weight loss was observed for the prepared HAp-NPs. SEM result reveals significant morphological variation of the prepared HAp-NPs by changing the amount of two surfactants. Variation of the ratio of surfactants SOS and CT AB allow the variation in the morphology of the prepared particles.Fargana YeasminMasters of Philosophy in Chemistr
