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hydrodynamics
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Global drag-induced instabilities in protoplanetary disks
, Article Astrophysical Journal ; Volume 772, Issue 1 , 2013 ; 0004637X (ISSN) ; Sharif University of Technology
2013
Abstract
We use the Fokker-Planck equation and model the dispersive dynamics of solid particles in annular protoplanetary disks whose gas component is more massive than the particle phase. We model particle-gas interactions as hard sphere collisions, determine the functional form of diffusion coefficients, and show the existence of two global unstable modes in the particle phase. These modes have spiral patterns with the azimuthal wavenumber m = 1 and rotate slowly. We show that in ring-shaped disks, the phase-space density of solid particles increases linearly in time toward an accumulation point near the location of pressure maximum, while instabilities grow exponentially. Therefore, planetesimals...
A SPH solver for simulating paramagnetic solid fluid interaction in the presence of an external magnetic field
, Article Applied Mathematical Modelling ; Volume 40, Issue 7-8 , 2016 , Pages 4341-4369 ; 0307904X (ISSN) ; Manzari, M. T ; Fatehi, R ; Sharif University of Technology
Elsevier Inc
2016
Abstract
The Smoothed Particle Hydrodynamics (SPH) method is extended to solve magnetostatic problems involving magnetically interacting solid bodies. In order to deal with the jump in the magnetic permeability at a fluid-solid interface, a consistent SPH scheme is utilized and a modified formulation is proposed to calculate the magnetic force density along the interface. The results of the magnetostatic solver are verified against those of the finite element method. The governing fluid flow equations are discretized using the same SPH scheme, developing an efficient method for simulating the motion of paramagnetic solid bodies in a fluid flow. The proposed algorithm is applied to a benchmark problem...
Multiphase simulation of liquid jet breakup using smoothed particle hydrodynamics
, Article International Journal of Modern Physics C ; Volume 28, Issue 4 , 2017 ; 01291831 (ISSN) ; Omidvar, P ; Morad, M. R ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2017
Abstract
This paper deals with numerical modeling of two-phase liquid jet breakup using the smoothed particle hydrodynamics (SPH) method. Simulation of multiphase flows involving fluids with a high-density ratio causes large pressure gradients at the interface and subsequently divergence of numerical solutions. A modified procedure extended by Monaghan and Rafiee is employed to stabilize the sharp interface between the fluids. Various test cases such as Rayleigh-Taylor instability, two-phase still water and air bubble rising in water have been conducted, by which the capability of accurately capturing the physics of multiphase flows is verified. The results of these simulations are in a good...
Investigation of hydrodynamically dominated membrane rupture, using smoothed particle hydrodynamics–finite element method
, Article Fluids ; Volume 4, Issue 3 , 2019 ; 23115521 (ISSN) ; Taeibi Rahni, M ; Akbarzadeh, A. M ; Javadi, K ; Ahmadi, G ; Sharif University of Technology
MDPI AG
2019
Abstract
The rupturing process of a membrane, located between two fluids at the center of a three-dimensional channel, is numerically investigated. The smoothed particle hydrodynamics (SPH) and the finite element method (FEM) are used, respectively, for modeling the fluid and solid phases. A range of pressure differences and membrane thicknesses are studied and two different rupturing processes are identified. These processes differ in the time scale of the rupture, the location of the rupture initiation, the level of destruction and the driving mechanism. © 2019 by the authors
Vortex shedding modes around oscillating non-uniform double heave plates
, Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; 2020 ; Alvandi, M ; Behzad, M ; Thiagarajan, K. P ; Sharif University of Technology
SAGE Publications Ltd
2020
Abstract
Multiple co-axial heave plates of uniform geometry are attached to offshore platforms for inducing damping and added mass. These effects generally decrease the magnitude of the dynamic response of the platform under applied environmental excitation forces. When spacing between heave plates is decreased the damping and added mass performance are altered due to their strong vortex interaction. A new non-uniform plate configuration is proposed that may create different hydrodynamic characteristics. The modes of vortex shedding around plate edges in a non-uniform arrangement under forced harmonic oscillation are investigated via the CFD method. Furthermore, a new simplified formula for the total...
Studying effect of entrainment on dynamics of debris flows using numerical simulation
, Article Computers and Geosciences ; Volume 134 , 2020 ; Manzari, M. T ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
This paper studies entrainment phenomenon in debris flows using full flow (non-depth-averaged) equations and an Incompressible Smoothed Particle Hydrodynamics (ISPH) method. A viscoplastic constitutive relationship is adopted for both the overlying fluid and bed material. Collapse of a two-dimensional dry granular column on a horizontal bed consisting of entrainable dry granular material is considered as a benchmark problem. The adopted ISPH method for simulation of collapse over rigid and entrainable beds is validated using available numerical and experimental data. To quantify the effects of entrainment on dynamics of flow, the initial aspect ratio of granular column (a) is varied and the...
Revealing mass transfer and hydrodynamic effects in a PRDC column by using the integration of extraction and separation for molybdenum and tungsten ions from aqueous solution
, Article Chemical Papers ; Volume 74, Issue 12 , 2020 , Pages 4295-4313 ; Torkaman, R ; Torab Mostaedi, M ; Asadollahzadeh, M ; Sharif University of Technology
Springer
2020
Abstract
The present work is performed to assess the hydrodynamic parameters and mass transfer coefficients in a PRDC column for the chemical reaction systems. By considering the selective extraction of molybdenum from tungsten, the extraction parameters and synergistic enhancement factor were interpreted at the batch experiments. In the column experiments, the impacts of operating conditions such as the agitation rate, inlet solvent phase velocity as well as inlet aqueous phase velocity were studied on the drop behavior, overall mass transfer coefficients, and extraction efficiencies. The modified correlations by using relationship of dimensionless numbers were illustrated to estimate the...
An efficient system identification approach to estimate unsteady loads on cavitator plates
, Article Ocean Engineering ; Volume 207 , 2020 ; Dehghani Firouz Abadi, R ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
A new and efficient model for calculation of the unsteady hydrodynamic loads on an oscillating plate in two-dimensional flow is proposed. In order to compute the hydrodynamic loads, an unsteady hydrodynamic model is derived using the boundary-element method along with the potential flow assumption. To this aim, the steady boundary of cavity is determined by a full-nonlinear iterative procedure. Thereafter, assuming that amplitude and frequency of oscillations are so that the length of cavity in unsteady flow remains intact, simulation of the unsteady hydrodynamic flow is performed by imposing some velocity perturbations over the steady cavity solutions. Consequently, based on this...
Hydrodynamic analysis of trimaran vessels
, Article Polish Maritime Research ; Volume 15, Issue 1 , June , 2008 , Pages 11-18 ; 12332585 (ISSN) ; Jahanbakhsh, E ; Seif, M ; Sayyaadi, H ; Sharif University of Technology
2008
Abstract
Trimaran vessels are developed for different applications and hydrodynamic behavior of such vessels is different than usual mono-hulls. In this paper hydrodynamic resistance and maneuvering of a trimaran with Wigley body form are investigated. The effects of outriggers position in four different longitudinal and two transverse locations are studied. For hydrodynamic simulations a CFD code has been developed and used. This code is capable for simulating three dimensional, time dependent, two phases, viscous flow coupled with rigid body motion. Formulation and solution algorithm are described in detail. Different case studies have been performance and numerical results have shown good...
Ship hull drag reduction using bottom air injection
, Article ASME 2007- 26th International Conference on Offshore Mechanics and Arctic Engineering 2007, OMAE2007, San Diego, CA, 10 June 2007 through 15 June 2007 ; Volume 4 , 2007 , Pages 283-292 ; 0791842703 (ISBN); 9780791842706 (ISBN) ; Rad, M ; Amini, H ; Rishehri, M ; Sharif University of Technology
2007
Abstract
Air cavity ship concept has received some interest due to its potential on viscous resistance reduction for high speed craft. Air-cavity ships (ACS) are advanced marine vehicles that use air injection at the wetted hull surfaces to improve a vessel's hydrodynamic characteristics. Air is supplied through nozzles under a profiled bottom to generate an air cavity beneath such a ship, so that a steady air layer separates a part of the bottom from contact with water, consequently reducing hydrodynamic resistance. Resistance tests were conducted with two forms: first of which was planning catamaran hull form, and second one was an alternative form with an air cavity injection under its bottom...
An analytical solution for thermally fully developed combined pressure - electroosmotically driven flow in microchannels
, Article International Journal of Heat and Mass Transfer ; Volume 50, Issue 5-6 , 2007 , Pages 1087-1096 ; 00179310 (ISSN) ; Taghizadeh Manzari, M ; Hannani, S. K ; Sharif University of Technology
2007
Abstract
An analytical solution is presented to study the heat transfer characteristics of the combined pressure - electroosmotically driven flow in planar microchannels. The physical model includes the Joule heating effect to predict the convective heat transfer coefficient in two dimensional microchannels. The velocity field, which is a function of external electrical field, electroosmotic mobility, fluid viscosity and the pressure gradient, is obtained by solving the hydrodynamically fully-developed laminar Navier-Stokes equations considering the electrokinetic body force for low wall zeta potentials. Then, assuming a thermally fully-developed flow, the temperature distribution and the Nusselt...
Developing consistent inlet boundary conditions to study the entrance zone in microchannels
, Article Journal of Thermophysics and Heat Transfer ; Volume 21, Issue 3 , 2007 , Pages 596-607 ; 08878722 (ISSN) ; Vakilipour, S ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2007
Abstract
One important point in microflow study is the correct consideration of the Knudsen layer. In addition to the many complexities behind numerical simulation of the Knudsen layer near the solid walls, there are serious uncertainties at the microchannel inlet (the point at which the flow enters the microdomain). One major difficulty is the appearance of two singularities at the two corners of the inlet section. They seriously affect the solution in the entrance region of microchannels in which the lengths are comparable with the lengths of their hydrodynamic developing zones. Although the macro inlet flow problem has been largely investigated, there has been little attempt to study the issue in...
The effect of the time dependent pressure difference on bubble dynamics in microchannels
, Article 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, 19 June 2006 through 21 June 2006 ; Volume 2006 A , 2006 , Pages 83-88 ; 0791847608 (ISBN); 9780791847602 (ISBN) ; Rouhani, S ; Saboohi, Y ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
The physical processes responsible for bubble formation in microchannels are not well understood and lack fundamental understanding. Experimental results are not exactly in agreement with each other and there are no definite theories to explain the possible effects of different parameters. Among different parameters the microchannel hydraulic diameter can affect the bubble formation mechanism in microchannels strongly. In this paper the effect of the time dependent pressure difference between inside and outside of the bubble on bubble dynamics in microchannels have been investigated. The source of this time dependency can be the emergence of bubble embryos which produces a density...
Role of liquid compressional viscosity in the dynamics of a sonoluminescing bubble
, Article Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics ; Volume 70, Issue 1 , 2004 , Pages 6- ; 1063651X (ISSN) ; Sadighi Bonabi, R ; Sharif University of Technology
2004
Abstract
The well-known Rayleigh-Plesset [Formula presented] equation is the basis of almost all hydrodynamical descriptions of single-bubble sonoluminescence [Formula presented]. A major deficiency of the [Formula presented] equation is that it accounts for viscosity of an incompressible liquid and compressibility, separately. By removing this approximation, a new modification of the [Formula presented] equation is presented considering effect of compressional viscosity of the liquid. This modification leads to addition of a new viscous term to the traditional bubble boundary equation. Influence of this new term in the dynamics of a sonoluminescing bubble has numerically been studied considering...
Novel quantum hydrodynamic equations for semiconductor devices
, Article Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers ; Volume 41, Issue 3 A , 2002 , Pages 1300-1304 ; 00214922 (ISSN) ; Faez, R ; Sharif University of Technology
Japan Society of Applied Physics
2002
Abstract
The Liouville equation for the distribution function is solved and a series solution for the Wigner distribution function is derived. In this solution, potential is nonlocal so that the distribution function in each point is influenced by the potential of the entire space. By computing the carrier density, an effective classical potential is defined. In a quantum system this effective potential replaces the classical potential. Based on the solution of the Liouville equation a novel set of three-dimensional quantum hydrodynamic equations (QHD) is derived. The form of the resulting QHD equations is similar to the classical hydrodynamic (HD) equations but there are explicit quantum corrections...
Experimental Study on Hydrodynamic Behavior of Drilling Fluid by Fluidizing Granular Materials in an Annulus
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Saeed (Supervisor) ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
During the drilling process, cutting concentration in vertical and inclined wells is a common problem and major issue in designing hydraulic parameters. This is becoming more important in near bit area. Cutting transport usually is affected by several parameters such as mud rheology, flow rate, nozzle size, rotation speed, and mud weight.
In this work it was aimed to design a new set-up to test all the factors on hole cleaning phenomenon especially in near bit area. The set-up consists of a 16 feet long flow loop, 3.28 feet height of the test section, and 3.33 inches inner diameter of the test section. Each parameter which has an impact on hole cleaning could be varied. The cutting...
In this work it was aimed to design a new set-up to test all the factors on hole cleaning phenomenon especially in near bit area. The set-up consists of a 16 feet long flow loop, 3.28 feet height of the test section, and 3.33 inches inner diameter of the test section. Each parameter which has an impact on hole cleaning could be varied. The cutting...
Simulation of Advection and Diffusion of Hazardous Noxious Substances (HNS) in Sea, Case Study: Oil Derivations in Caspian Sea
, M.Sc. Thesis Sharif University of Technology ; Raie, Mohammad (Supervisor)
Abstract
Hazardous Noxious Substances (HNS) are chemicals. Due to population increase and as a result, increased demand, HNS transportation by sea has been raised. Gasoline and diesel are two kinds of HNS which have the largest transported amount via northern ports of Iran especially Anzali port. So, HNS spill from tankers is an imminent event and threat for environment of Caspian Sea. Organizations that are concern about the health of coasts and seas water always try to use the softwares to simulate the currents and waves to define the hydrocarbon slick transport. Therfore in this study, a 2D hydrodynamic/oil spill model has been developed to predict the transportation of diesel and gasoline slick...
Optimizing the Propulsion Arrangement of a Par Wig Craft to Reduce the Take-off Time
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohamad Saeed (Supervisor)
Abstract
In this thesis, an attempt is made to provide a hydro-aerodynamic mathematical model of a 20-bird batboat with a combined wing with catamaran body shape equipped with a parachute propulsion system in the rising phase of the surface and optimizing the propulsion system to reduce the take-off phase of the bird's boat. For this purpose, the hydro-aerodynamic modeling of the bird's boat from the rest period to the cruise phase has been considered, taking into account the parachuting system. For this purpose, three methods are considered. In the first method, combinatorial wing aerodynamic modeling and hydrodynamic modeling of the radar catamaran float were first studied. Finally, in the case of...
Hull Form Optimization of Floating Body for Maneuvering
, M.Sc. Thesis Sharif University of Technology ; Sayyaadi, Hassan (Supervisor)
Abstract
This paper was directed to recognize maneuver equations perfectly, and with regard to CFD method maneuver simulation is going to be done in form of two and three dimensional. Today, since CFD methods have been exerted in different works, further and more actual development of floating body's maneuver is going to be our special need. As numerical methods for floating body's maneuver simulation by RANS method are developing, more researches are being done about this field as well. This thesis is going to simulate primitively maneuver of one floating body by Smoothed Particle Hydrodynamic(SPH) method in order to be as the beginning of maneuver simulation by this method in which with regard to...
High frequency oscillatory flow in micro channels
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Vol. 460 , 2014 , pp. 355-360 ; ISSN: 09277757 ; Javadi, A ; Bastani, D ; Miller, R ; Sharif University of Technology
Abstract
This paper deals with computational and experimental studies on the oscillatory flow at high frequencies up to 100. Hz performed with the Oscillating Drop and Bubble Analyzer (ODBA) setup based on the capillary pressure technique. The CFD results are validated considering pressure amplitude experimental data. The simulated results of phase shift between the generated oscillatory flow and the consequent pressure amplitudes show also good agreement with the experimental data. In absence of any compressibility and viscoelasticity effects and assumptions, a complex velocity field during oscillation is the main reason for the observation of a phase shift. The results of velocity profiles at the...