CFD modeling of liquid–solid fluidization: Effect of drag correlation and added mass force

Particuology ◽  
2011 ◽  
Vol 9 (4) ◽  
pp. 441-445 ◽  
Author(s):  
Xiaoyan Huang
Keyword(s):  
Added Mass ◽  
Cfd Modeling ◽  
Mass Force

A Double Birkhoff Wake Oscillator for the Modeling of Vortex-Induced Vibration

2011 ◽  
Author(s):  
R. H. M. Ogink
Keyword(s):  
Free Vibration ◽  
Added Mass ◽  
Mass Force ◽  
Near Wake ◽  
Vibration Measurements ◽  
Vortex Induced Vibration ◽  
Fluid Forces ◽  
Wake Oscillator ◽  
Model Equations ◽  
Far Wake

A double Birkhoff wake oscillator for the modeling of vortex-induced vibration is presented in which the oscillating variables are assumed to be associated with the boundary layer/near wake and the far wake. The fluid forces are assumed to consist of a potential added mass force and a force due to vortex shedding. In the limit of vanishing incoming flow velocity, the model equations reduce to a form similar to the Morison equation. The results of the double wake oscillator have been compared with forced vibration measurements and free vibration measurements over a range of mass and damping ratios. The model is capable of describing the most important trends in both the forced and free vibration experiments. Specifically, the double wake oscillator is able to model both the upper and lower branch of free vibration.

An Investigation to Added Mass Force on the Wing of Insect Inspired from a Rigid Sphere Model

2012 ◽  
Vol 476-478 ◽  
pp. 2485-2488
Author(s):  
Mei Jun Hu ◽  
Xing Yao Yan ◽  
Jin Yao Yan
Keyword(s):  
Insect Flight ◽  
Aerodynamic Force ◽  
Mass Effect ◽  
Added Mass ◽  
Rigid Sphere ◽  
Force Model ◽  
Mass Force ◽  
Real Time Control ◽  
Wing Model ◽  
Force Peak

There is a force peak at the beginning of each stroke during the insect flight, this force peak contributes a lot to the total aerodynamic force. To build a man made insect inspired man-made micro aero vehicle, this force need to be considered in the aero force model, and this model should as simple as possible in order to be used in feedback real-time control. Here we presented a simplified model to take the medium added mass effect of the wing into account. Simulated results show a high force peak at the beginning of each stroke and are quite similar to the measured forces on the physical wing model which were carried out by Dickinson et.al.

On the unsteady inviscid force on cylinders and spheres in subcritical compressible flow

2008 ◽  
Vol 366 (1873) ◽  
pp. 2161-2175 ◽  
Author(s):  
M Parmar ◽  
A Haselbacher ◽  
S Balachandar
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Propagation Speed ◽  
Added Mass ◽  
The Body ◽  
Mass Force ◽  
Unsteady Force ◽  
Mass Coefficient ◽  
Added Mass Coefficient ◽  
Cylinders And Spheres

The unsteady inviscid force on cylinders and spheres in subcritical compressible flow is investigated. In the limit of incompressible flow, the unsteady inviscid force on a cylinder or sphere is the so-called added-mass force that is proportional to the product of the mass displaced by the body and the instantaneous acceleration. In compressible flow, the finite acoustic propagation speed means that the unsteady inviscid force arising from an instantaneously applied constant acceleration develops gradually and reaches steady values only for non-dimensional times c ∞ t / R ≳10, where c ∞ is the freestream speed of sound and R is the radius of the cylinder or sphere. In this limit, an effective added-mass coefficient may be defined. The main conclusion of our study is that the freestream Mach number has a pronounced effect on both the peak value of the unsteady force and the effective added-mass coefficient. At a freestream Mach number of 0.5, the effective added-mass coefficient is about twice as large as the incompressible value for the sphere. Coupled with an impulsive acceleration, the unsteady inviscid force in compressible flow can be more than four times larger than that predicted from incompressible theory. Furthermore, the effect of the ratio of specific heats on the unsteady force becomes more pronounced as the Mach number increases.

scholarly journals Decomposition of the forces on a body moving in an incompressible fluid

2019 ◽  
Vol 881 ◽  
pp. 1097-1122
Author(s):  
W. R. Graham
Keyword(s):  
Velocity Field ◽  
Pressure Field ◽  
Rotational Velocity ◽  
Inviscid Flow ◽  
Added Mass ◽  
The Body ◽  
Mass Force ◽  
Natural Approach ◽  
Fluid Forces ◽  
Point Pressure

In analysing fluid forces on a moving body, a natural approach is to seek a component due to viscosity and an ‘inviscid’ remainder. It is also attractive to decompose the velocity field into irrotational and rotational parts, and apportion the force resultants accordingly. The ‘irrotational’ resultants can then be identified as classical ‘added mass’, but the remaining, ‘rotational’, resultants appear not to be consistent with the physical interpretation of the rotational velocity field (as that arising from the fluid vorticity with the body stationary). The alternative presented here splits the inviscid resultants into components that are unquestionably due to independent aspects of the problem: ‘convective’ and ‘accelerative’. The former are associated with the pressure field that would arise in an inviscid flow with (instantaneously) the same velocities as the real one, and with the body’s velocity parameters – angular and translational – unchanging. The latter correspond to the pressure generated when the body accelerates from rest in quiescent fluid with its given rates of change of angular and translational velocity. They are reminiscent of the added-mass force resultants, but are simpler, and closer to the standard rigid-body inertia formulae, than the developed expressions for added-mass force and moment. Finally, the force resultants due to viscosity also include a contribution from pressure. Its presence is necessary in order to satisfy the equations governing the pressure field, and it has previously been recognised in the context of ‘excess’ stagnation-point pressure. However, its existence does not yet seem to be widely appreciated.

The Phenomenon of Bubbles Negative Relative Velocity in Vertical Bubbly Jets

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Jamel Chahed ◽  
Aroua Aouadi ◽  
Mariem Rezig ◽  
Ghazi Bellakhal
Keyword(s):  
Slip Velocity ◽  
Added Mass ◽  
Mass Force ◽  
Relative Slip ◽  
Velocity Inversion ◽  
Injection Zone ◽  
Bubbly Jet ◽  
New Formulation ◽  
Interfacial Force ◽  
Bubbly Jets

Many experiments demonstrate that the bubble relative (slip) velocities in vertical turbulent sheared bubbly flows are significantly lower than those in quiescent infinite fluid. Moreover, vertical bubbly jet experiments performed by Sun and Faeth (1986, “Structure of Turbulent Bubbly Jets-1. Methods and Centerline Properties,” Int. J. Multiphase Flow, 12(1), pp. 99–114) indicate that bubble slip velocities have negative values in the high sheared zone near the injector. The present analysis shows that the phenomenon of the slip velocity inversion is associated with the effect of the turbulent part of the interfacial force. A new formulation of the turbulent contribution of the added mass force is proposed. This formulation is analyzed using the vertical bubbly jet experimental data. The results provide evidence that the turbulent contribution of the added mass force is at the origin of the slip velocity reduction and could explain the appearance of the negative values observed in bubbly jet experiments. As a whole, the turbulent contribution of the added mass force which comprises two terms (a nonlinear turbulent term and a convective acceleration term associated to the drift velocity) opposes the action of the gravity and their effect may be high enough to produce negative slip velocities. Taken separately, the two turbulent terms cannot explain the reversal and the reduction of slip through the entire section in the near injection zone of the bubbly jet. The combined effect of the two turbulent terms makes it possible to reproduce slip velocity profiles as observed in the near injection zone.

Lift, drag and added mass of a hemispherical bubble sliding and growing on a wall in a viscous linear shear flow

2008 ◽  
Vol 366 (1873) ◽  
pp. 2233-2248 ◽  
Author(s):  
Dominique Legendre ◽  
Catherine Colin ◽  
Typhaine Coquard
Keyword(s):  
Shear Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Added Mass ◽  
Unsteady Motion ◽  
Navier Stokes ◽  
Mass Force ◽  
Navier Stokes Equations ◽  
Wide Range ◽  
Linear Shear

The three-dimensional flow around a hemispherical bubble sliding and growing on a wall in a viscous linear shear flow is studied numerically by solving the full Navier–Stokes equations in a boundary-fitted domain. The main goal of the present study is to provide a complete description of the forces experienced by the bubble (drag, lift and added mass) over a wide range of sliding and shear Reynolds numbers (0.01≤ Re b , Re α ≤2000) and shear rate (0≤ Sr ≤5). The drag and lift forces are computed successively for the following situations: an immobile bubble in a linear shear flow; a bubble sliding on the wall in a fluid at rest; and a bubble sliding in a linear shear flow. The added-mass force is studied by considering an unsteady motion relative to the wall or a time-dependent radius.

scholarly journals Modeling of Deposition of Solid Particles at Cleaning of Oil in Gravitational Separator

2020 ◽  
Vol 126 (1) ◽  
pp. 8-10
Author(s):  
А. А. Gasanov ◽  
◽  
N. Kh. Gamzaeva ◽  
Keyword(s):  
Particle Deposition ◽  
Stationary Process ◽  
Viscous Friction ◽  
Added Mass ◽  
Solid Particles ◽  
Mass Force ◽  
Empirical Theory ◽  
Friction Forces ◽  
Proposed Model ◽  
Semi Empirical

The non-stationary process of sedimentation of a solid spherical particle in a fluid at rest in a gravitational separator is considered. To describe this process, we propose a mathematical model that takes into account viscous friction forces, which is determined on the basis of the Prandtl semi-empirical theory of turbulence, Basse hereditary force, as well as the added mass force. To implement the proposed model, a difference method is used. Using a numerical experiment, the effects of various forces on the particle deposition rate are investigated.

scholarly journals CFD Modeling on Thermal Management of IC using Water Based Fe, Cu and Al Nanofluids

2019 ◽  
Vol 8 (6) ◽  
pp. 1666-1670
Keyword(s):  
Thermal Management ◽  
Temperature Limit ◽  
Temperature Curve ◽  
Cfd Modeling ◽  
Solid Boundary ◽  
Mass Force ◽  
Boundary Temperature ◽  
Water Based ◽  
One To One

In unrelenting civility, CFD codes are developed and simulated with water based Fe, Cu and Al nanofluids for foreseeing the heat alarms of ICs. The convective governing equalities of mass, force and drive are computed for envisaging the thermal issues of ICs. The time pace selected throughout the intact computation is 0.0001 s. The soundings affect CFD forecasts of temperature curve, temperature arena plus fluid-solid boundary temperature of IC. Corresponding fluid-solid boundaries temperatures of IC are viewed as 321, 309 and 313 K for water based Fe, Cu and Al nanofluids, one-to-one. The temperature of water-Cu nanofluid stands peak contiguous to the IC locality as it stands far less than the chancy temperature limit of 356 K. Further, the temperature of water-Cu nanofluid gently drops with improvement in aloofness from IC. Afterwards, this becomes surrounding temperature in the distant arena precinct. The analogous tinted temperature curve stands accessible. In addition, the congruent plot of temperature verses distance from IC stays revealed. The uneasiness of CFD compassionate position nearby the conveniences of jargons.

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