Two-dimensional Hydrodynamic Flow Research Articles

Two-dimensional hydrodynamic electron flow through periodic and random potentials

Two-dimensional hydrodynamic electron flow through periodic and random potentials

Manipulation of Microparticles in Optofluidic Devices Fabricated by Femtosecond Laser Micromachining

This study reports the fabrication of three-dimensional microfluidic channels in fused silica, using femtosecond laser micromachining, to achieve two-dimensional hydrodynamic flow focusing in either the horizontal or the vertical directions. Spatial focusing of 3 μm polystyrene particles was successfully demonstrated, showing the ability of the fabricated devices to confine microparticles within a 6 μm layer over a channel width of 420 μm and within a 5 μm layer over a channel height of 260 μm. Integration of laser-direct written optical waveguides inside a microfluidic chip and orthogonal to the channel also enabled the implementation of a dual-beam optical trap, with trapping of polystyrene microparticles using a 1550 nm beam being demonstrated.

Coastal morphodynamic alterations in response to non-tsunami waves — Northern Oman

The tectonically active Makran Subduction Zone (MSZ) overlooks Oman’s northern coast, where the Eurasian and Arabian Plates meet in the Sea of Oman. There have been significant tsunamis and earthquakes caused by the MSZ in the past. A recent non-tsunami event in northern Oman led to hydrodynamic and morphological alterations, as well as changes in coastal stability, which were explored in this study. An integrated module for hydrodynamics, waves, and sediment flow is assigned to carry out process-based numerical modeling. To manage a two-dimensional hydrodynamic flow system, CMS-Flow and CMS-Wave steering modules were employed. Tidal currents exhibit spatial variability due to bathymetric and geographic complexity. This, combined with sediment transport channels that follow tide-related asymmetry patterns, results in an apparent asymmetry between ebb and flood flows. The annual morphological change in the region around the port of Sohar is not affected by waves created by northwesterly high winds, despite the fact that these waves have the capacity to redistribute sediments. As shoals are propelled by waves/winds in the same direction, their currents are not as predictable as those generated by waves/winds. This study’s computational sediment transport model shows that flood-driven transport happens mostly on the east side of the port of Sohar. There has been very little accumulation of intertidal sand shoals in the port, as shown by the model; this suggests that sediment filling has progressed very slowly, which could lead to navigational hazards over time. While flood control measures have been necessary for Sohar’s coastal area, they will be unnecessary shortly as the port’s eastern section is expected to shift from flood to ebb dominance and act as a source of sediment rather than sink.

2D hydrodynamic approach supporting evaluations of hydrological response in small watersheds: Implications for lag time estimation

The use of integrated flood models represents an approach of growing interest in the literature, being the hydrological and hydrodynamic flood processes described entirely within the two-dimensional (2D) hydrodynamic unsteady flow equations. Due to its ability in simulating complex spatial–temporal dependence of both the hydrodynamic and hydrologic responses of a catchment to rainfall events, this kind of approach paves the way to the development of novel lines of research in catchment hydrology. With particular reference to the lag time estimation, the paper focuses on three interrelated issues: 1) the use of the 2D-SWEs model to provide evidence on the variability of the lag time in small basins, 2) the description of the hydrologic response of small catchments based on characteristic times influencing the hydrodynamic response to rainfall events and 3) the representativeness of hydrodynamic-based rainfall-runoff scenarios in the description of the hydrologic response observed in real events. To that purpose, synthetic rainfall-runoff scenarios for different return periods are firstly generated to analyze the hydrologic response time in three ungauged basins. Then regressive formulas, based on ad hoc variables representing characteristic times, are introduced to interpret the variability shown by the computed lag time. Finally, the physical soundness of the proposed approach is tested against observed rainfall-runoff data in four additional basins. Despite all the simplifications introduced in the proposed approach, the regressive formulas provided a reasonably good agreement with the estimations of the lag time of the observed events, showing errors of the order of 30%. The comparison with the predictions of empirical literature formulas further confirms the potential of the proposed approach. This study represents the basis for future research on basin response to rainfall events through the use of a 2D integrated hydrodynamic-hydrologic modeling.

Investigation of the drainage loss effects with a street view based drainage calculation method in hydrodynamic modelling of pluvial floods in urbanized area

Drainage loss effects are crucial for flash flood modelling induced by torrential rains in urbanized environment. This paper proposes a novel approach for incorporating drainage loss effects into two-dimensional hydrodynamic overland flow simulations with the open source databases offered by geographical information providers. Street inlet locations within the road network are determined using street view images based on feature points extracted throughout automatic navigation along the roads in the panoramas, where the runoff of the surface flood flow is determined by the drainage network's capacity. By implementing the proposed data acquisition and drainage loss calculation method into the 2D overflow model HiPIMS as an alternative to the often-unrealizable physically based method or to the overly simplistic rainfall reduction method, the flood modelling results are validated against field observations during severe flood events in an intensely urbanized area to demonstrate the feasibility and effectiveness of the newly proposed method. In comparison to other simulation scenarios without drainage loss effects or with those considered by the rainfall reduction method, the drainage loss effects induced by the newly proposed method are analyzed for both the spatially lumped and distributed urban flood patterns. While the drainage effects are more essential after the rainfall peak hours for the flood extent as spatially lumped results, the low-lying area with dense building complexes are found to benefit more from the drainage effects in a spatially distributed way. Variations of the speed and direction of flood flows caused by the drainage effects at inlets are observed to depend on the surrounding environment. Competitions between the drainage effects and the gravity effects induced by topographical features are revealed with street-level evaluations of the flood modeling results using high-resolution hydrodynamic modeling in conjunction with the proposed drainage calculation approach.

Numerical Computation of Rapid Flow over Steep Terrain Using Total Acceleration Method

ABSTRACT Rhee, D.S.; Lyu, S.W., and Song, C.G., 2018. Numerical computation of rapid flow over steep terrain using total acceleration concept. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 986–990. Coconut Creek (Florida), ISSN 0749-0208. To model the rapid mass movement over steep slope under the framework of shallow water flow, total acceleration method (TAM hereafter) was adopted, and an extended two-dimensional hydrodynamic flow model was developed. This approach can be regarded as gravity modeling as eddy viscosity in turbulence modeling. It was found that the developed flow model with total acceleration method gave satisfactory results in predicting the front propagation speed, flow depth, and bed-shear stress under significant non-hydrostatic condition. TAM reproduced considerable difference in describing the routing of fast flow compared with usual 2...

Characterization of Nanoscale Loaded Liposomes Produced by 2D Hydrodynamic Flow Focusing.

This paper presents the continuous flow formation by two-dimensional (2D) hydrodynamic flow focusing (HFF) of nanosized liposomes in microfluidic systems. The size distribution and concentration of the nanosized liposomes, as well as the polydispersity index (PDI) and zeta potential (ZP) of the liposomal dispersions, were investigated under various flow rate ratios (FRRs) and lipid formulations, by the selective incorporation of either positively charged DDAB (didodecyl-dimethylammonium bromide) or negatively charged DOPG (1,2 dioleoyl-sn-glycero-3- phosphoglycerol) lipids to the main bilayer DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) constituent. The challenges of encapsulating an FITC (fluorescein isothiocyanate)-labeled LC-TAT peptide (long chain of transactivator of transcription peptide), which plays a direct role in the HIV regulation and transcription, overcame and could be achieved via one-step nanoliposomes synthesis, in order to validate the potential of this device as an all-in-one nanoparticle synthesis and loading platform. Liposomes with sizes ranging between 60 to 800 nm were produced with low polydispersity and high particle throughput from alteration of the flow rate ratio and lipid concentration. We introduced the use of nanoparticle tracking analysis (NTA) to estimate for the first time the throughput of microfluidic synthesized liposomal NPs by measuring quantitatively the concentration of the synthesized particles at the outlet. These measurements showed that stable and unilamellar liposomes are generated at a maximum concentration of 1740 × 108 particles/mL in less than 2 min, with higher FRR enabling the most rapid generation of liposomes with similar diameter and significant lower polydispersity index than those obtained by other batch techniques.

Hydraulic and Hydrologic Modeling of Steep Channel of Putih River, Magelang District, Central Java Province, Indonesia

Hydrologic and hydraulic modeling are important to be conducted to examine the watershed response based on a rainfall input, especially over disaster-prone watershed such as Putih River watershed in Magelang, Central Java Province. A GIS-based grid-based distributed rainfall-runoff model was used to simulate the rainfall-runoff transformation. A two-dimensional hydrodynamic flow modeling was then carried out to simulate the flood processes on the stream and floodplain area. A sensitivity analysis was conducted on infiltration rate, Manning’s n value, and rainfall intensity. Infiltration rate, Manning’s n value, and rainfall intensity give considerable effects to the resulted flow hydrographs. The modeling results show that the results of hydrologic-hydraulic modeling is in good agreement with the observed results.

Two-dimensional hydrodynamic flow focusing in a microfluidic platform featuring a monolithic integrated glass micronozzle

Two-dimensional hydrodynamic flow focusing is demonstrated through a microfluidic device featuring a monolithic integrated glass micronozzle inside a flow-focusing geometry. Such a coaxial configuration allows simple one-step focusing of a sample fluid stream, jetted from the micronozzle tip, in both in-plane and out-of-plane directions. The width of the focused filament can be precisely controlled and further scaled down to the submicrometer regime to facilitate rapid hydrodynamic mixing. Fluorescence quenching experiments reveal ultra-fast microsecond mixing of the denaturant into the focused filament. This device offers new possibilities to a set of applications such as the study of protein folding kinetics.

Effects of radiation on convection heat transfer of Cu-water nanofluid past a moving wedge

Heat transfer characteristics of a two-dimensional steady hydrodynamic flow of water-based copper(Cu) nanofluid over a moving wedge, taking into account the effects of thermal radiation, have been investigated numerically. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing fundamental equations are first transformed into a system of ordinary differential equations and solved numerically by using the fourth-order Runge-kutta method with shooting technique. A comparison with previously published work has been carried out and the results are found to be in good agreement. The existence of unique and dual solutions for self-similar equations of the flow and heat transfer are analyzed numerically. The results indicate that there is strong dependence of the thermal gradient at the surface of the wedge on both velocity ratio parameter and thermal radiation.

Edge gradients evaluation for 2D hybrid finite volume method model

ABSTRACTThis paper presents a two-dimensional depth-integrated hydrodynamic flow model using the Finite Volume Method (FVM) on a hybrid unstructured mesh system with a collocated variable arrangement. A new evaluation method for computing the gradients at the cell edges, derived based on the second-order Taylor series expansion, is proposed to improve the solution due to mesh irregularity and non-uniformity. In this method, no interpolation for variables at cell vertices is necessary. The cross-edge flux is evaluated by using the momentum interpolation. The convergence, robustness and accuracy of this model based on the new evaluation method of edge gradients have been demonstrated by several numerical convergence tests and applications to natural rivers with complex geometries and instream structures.

Transient Boundary Layer Laminar Free Convective Flow of a Nanofluid Over a Vertical Cone/Plate

Two-dimensional transient hydrodynamic boundary layer flow of incompressible Newtonian nanofluid past a cone and plate with constant boundary conditions is investigated numerically. The Newtonian nanofluid model incorporates the effects of Brownian motion and thermophoresis. In order to solve the transformed unsteady, nonlinear coupled boundary layer equations numerically under the conditions, an implicit finite difference scheme of Crank–Nicolson type has been employed. Numerical results obtained for the velocity, temperature and nanoparticle concentration distributions, as well as the skin friction, local Nusselt number and local Sherwood number for several values of the parameters, namely the buoyancy ratio parameter, Prandtl number, Lewis number and nanofluid parameters. The dependency of the thermophysical properties has been discussed on these parameters. The results shown that the Brownian motion parameter increased, the local skin friction decreased while the local Nusselt number and local Sherwood number increased. However, they both decreased as the thermophoresis parameter increased. The approach used in optimizing the transient boundary layer heat transfer of nanofluid problems. The use of nanoparticles improve the heat transfer performance of the base fluids having poor thermophysical properties which are not able to meet the cooling rate of modern engineering equipments.

Computer modeling the hydrodynamics of explosion above a surface

The hydrodynamics of processes occurring in explosion of condensed explosives in air at some height above the ground surface is considered. The computation technique, physical model, and results of simulation of a two-dimensional hydrodynamic flow arising in explosion of cylindrical charges are discussed. For the description of products of explosion the Jones–Wilkins–Lee equation of state is used. The explosions of charges with different mass (0.5, 5, 50kgTNT) are considered. The results of calculation allow one to obtain a detailed space–time picture of the arising flow and to study the origination, propagation, interaction and subsequent attenuation of shock waves. It is shown that the interaction of secondary and reflected from surface shock waves can strongly influence on the dynamics of flow.

Numerical modeling the dynamics of flow in explosion above a surface

The hydrodynamics of processes occurring in explosion of condensed explosives in air is considered. The physical model, computation technique, and results of simulation of a two-dimensional hydrodynamic flow arising in explosion of cylindrical charges are discussed. In this case, the explosions are considered at some distance above the ground. To close the gas-dynamics equations, the Jones–Wilkins–Lee equation of state is used. The results of calculation allow one to obtain a detailed space–time pattern of the arising flow and to study the origination, propagation, and subsequent attenuation of shock waves. Cylindrical charges of the same mass but with different diameter-to-length ratios are considered. It is shown that the charge shape can render essential influence on dynamics of flow and the parameters of shock waves (in the near and medium fields of explosion).

Critical flow over spillway profiles

One of the oldest problems of critical flow in open-channel hydraulics is rise in the channel bottom, which causes a critical flow at the weir crest. Although the classic hydraulic theory for parallel flow shows the usefulness of critical flow leading to unique head–discharge relations over the weir, in practice the parallel flow condition is unreal; theoretical analysis of round-crested weirs is thus restricted to teaching purposes or is used as a rough indication of flow characteristics before using more complete methods. The spillway problem has been treated previously with more laborious methods, either using two-dimensional (2D) hydrodynamic flow nets or accurate physical model experiments. A new extended Bernoulli energy equation, which is valid for moderately curved channel flows, is presented. From this equation, a higher-order critical flow condition suitable for a curved streamline flow has been developed. As a practical application, the flow over spillway profiles used in dam engineering has been studied. The proposed new critical flow theory makes it possible to simulate flow features with a reasonable agreement up to design conditions of the spillway, thus obtaining accurate results in situations in which the velocity is non-uniform, the pressure is non-hydrostatic and conventional critical flow theory is not valid.

Model investigation on the impact of Raha Beach development on Umm Al Nar Power and Desalination Plant

Umm Al Nar Power and Desalination Plant is one of the largest plants in Abu Dhabi Emirate, United Arab Emirates. The plant was built in the mid eighties and its capacity was increased in 2001. The present plant capacity after the extension is 1000 Mega Watt power and 165 Million Gallon water per day. Recently, it was decided to develop and reclaim the Raha Beach coastal area near the plant for housing and recreation purposes. This requires reclamation of a large area in the Airport Channel, which is a large channel connected to the plant vicinity. A comprehensive study was carried out by Water & Power Research Center of Abu Dhabi Water & Electricity Authority to investigate the impact of the reclamation activities in the Airport Channel on the flow pattern in the plant vicinity and the recirculation of effluents from the outfalls of the plant to its intakes. The paper describes the two-dimensional numerical hydrodynamic flow model used in the study. The model results showing the effects of the reclamation activities on the flow pattern and the brine disposal of the plant is presented and discussed.

Numerical and experimental study of mass transfer in lysozyme ultrafiltration

This paper addresses protein ultrafiltration (UF) and its dependence on UF operating conditions. Cellulose acetate (CA) asymmetric membranes are laboratory made by the phase-inversion method and characterized in terms of pure water permeability, 8.8×10 −12 m/s/Pa, and molecular weight cut-off (10000 Da for 98% of rejection). The important feature of the permeation cell is the slit feed channel of 200 mm×30 mm×1.2 mm that simulates the two-dimensional hydrodynamic flow conditions in a spiral wound membrane module. Permeation experiments were carried out for solutions of reference solutes in order to characterize the membranes and for lysozyme solutions under different operating conditions. The influence of the ionic strength in the permeation flux and protein rejection is studied by performing permeation tests with a solution of lysozyme (0.3 kg/m 3) containing different NaCl concentrations. Experimentally was observed a decline in the permeate flux with increasing ionic strength. The membrane is almost completely retentive in relation to lysozyme, since the apparent rejection coefficient, ƒ, for this protein is always higher than 95% (in almost all cases, higher than 98%). Two distinct sets of CFD simulations were performed. One to predict the permeation velocities, ν p , and another to predict the lysozyme concentration polarization.

Fluid instabilities and wakes in a soap-film tunnel

We present a compact, low-budget two-dimensional hydrodynamic flow visualization system based on a tilted, gravity-driven soap film tunnel. This system is suitable for demonstrations and studies of a variety of fluid mechanics problems, including turbulent wakes past bluff bodies and lifting surfaces, Kelvin–Helmholtz instability, and grid turbulence.

Nanofiltration Mass Transfer at the Entrance Region of a Slit Laminar Flow

A numerical model to predict laminar flows hydrodynamics and concentration polarization of salt aqueous solutions in a slit is proposed and experimentally validated. Physical modeling for the flow and for the mass transfer process is incorporated, in association with the osmotic pressure constitutive equation and a variation law for the membrane intrinsic rejection coefficient. The finite volume formulation is used with the SIMPLE algorithm to solve the discretized equations derived from the partial nonlinear differential equations of the mathematical model. The convection terms of the transport equations are discretized by the second-order hybrid central differences/upwind scheme. The experimental cell is a slit 200 mm × 30 mm × 2 mm that simulates the two-dimensional hydrodynamic flow conditions of the open feed channel of a spiral wound module. The predicted values at the hydrodynamic entrance region for different permeation velocities and rejection coefficients for sodium sulfate solutions, and for a single Schmidt number of 850, are compared against the corresponding experimental values and exhibit an excellent agreement. A new mass transfer correlation Stp = 1 + 3.68 × 10-4(x/h)-1.11Re0.95Rep-1.79 is proposed.

Cellular automata and hydrodynamic applications

Cellular automata are large lattices where each site carries a spin; the orientation of each spin at time t + 1 is completely determined by the orientation of its neighbor spins at time t. We review the classification of automata in the style of Wolfram, but now including two and three dimensions. As a practical application, we use the "lattice gas" automata with seven spins on each site of a triangular lattice to describe two-dimensional hydrodynamic flow around an obstacle, through a membrane, and through porous media.