An Experimental Study of Internal Hygrocysts

1976 ◽  
Vol 98 (4) ◽  
pp. 688-692 ◽  
Author(s):  
R. T. Balmer ◽  
T. G. Wang
Keyword(s):  
Secondary Flow ◽  
Weber Number ◽  
Critical Speed ◽  
Body Force ◽  
Volume Fraction ◽  
Anomalous Behavior ◽  
Body Motion ◽  
Fluid Systems ◽  
Correlation Models ◽  
Lateral Body

The onset of the stable laminar secondary flow (hygrocysts) that arises when a partially filled container is rotated about a horizontal axis has been experimentally studied. Nearly 500 sets of data on thirteen fluid systems were obtained and analyzed using a multiple linear regression computer program. Numerous dimensionless correlation models were investigated, the best being a power law relationship between the Reynolds number, volume fraction, and Weber number. Anomalous behavior was observed in that as the volume fraction approached unity, the critical speed of the onset of the secondary flow approached zero, indicating non-rigid body motion (driven by the lateral body force) in completely filled horizontal rotating containers.

NUMERICAL SIMULATION OF MARANGONI MAGNETOHYDRODYNAMIC BIO-NANOFLUID CONVECTION FROM A NON-ISOTHERMAL SURFACE WITH MAGNETIC INDUCTION EFFECTS: A BIO-NANOMATERIAL MANUFACTURING TRANSPORT MODEL

2014 ◽  
Vol 14 (03) ◽  
pp. 1450039 ◽  
Author(s):  
O. ANWAR BÉG ◽  
M. FERDOWS ◽  
S. SHAMIMA ◽  
M. NAZRUL ISLAM
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Prandtl Number ◽  
Stream Function ◽  
Magnetic Induction ◽  
Body Force ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Convection Boundary Layer ◽  
Force Parameter

Laminar magnetohydrodynamic Marangoni-forced convection boundary layer flow of a water-based biopolymer nanofluid containing nanoparticles from a non-isothermal plate is studied. Magnetic induction effects are incorporated. A variety of nanoparticles are studied, specifically, silver, copper, aluminium oxide and titanium oxide. The Tiwari–Das model is utilized for simulating nanofluid effects. The normalized ordinary differential boundary layer equations (mass, magnetic field continuity, momentum, induced magnetic field and energy conservation) are solved subject to appropriate boundary conditions using Maple shooting quadrature. The influence of Prandtl number (Pr), magnetohydrodynamic body force parameter (β), reciprocal of magnetic Prandtl number (α) and nanofluid solid volume fraction (φ) on velocity, temperature and magnetic stream function distributions is investigated in the presence of strong Marangoni effects (ξ i.e., Marangoni parameter is set as unity). Magnetic stream function is accentuated with body force parameter. The flow is considerably decelerated as is magnetic stream function gradient, with increasing nanofluid solid volume fraction, whereas temperatures are significantly enhanced. Interesting features in the flow regime are explored. The study finds applications in the fabrication of complex biomedical nanofluids, biopolymers, etc.

Design of Lizard-Inspired Robot with Lateral Body Motion

2018 ◽  
Author(s):  
Jeongryul Kim ◽  
Hongmin Kim ◽  
Youngsoo Kim ◽  
Hwa Soo Kim ◽  
Jongwon Kim
Keyword(s):  
Body Motion ◽  
Lateral Body

On Transverse Vibrations of Functionally Graded Rotating Hollow Disk

2010 ◽  
Author(s):  
Rui Liu ◽  
Hamid Nayeb-Hashemi ◽  
Masoud Olia ◽  
Ashkan Vaziri
Keyword(s):  
Elastic Modulus ◽  
Critical Speed ◽  
Volume Fraction ◽  
Rotating Disk ◽  
Outer Radius ◽  
Functionally Graded ◽  
Distribution Functions ◽  
Rotating Disks ◽  
Disk Radius ◽  
Power Law Function

We studied the stress field and vibration characteristics of functionally graded rotating disks by solving the governing equation of motion using the finite difference scheme. The material was assumed to have a constant Poisson’s ratio with the elastic modulus varying as a power law function of the disk radius. Such a material could be developed by using particle reinforced composites with various reinforcements or reinforcement volume fraction. The results show that the first critical speed of the rotating disk could be increased by using FGMs. The first critical speed is greater for disks having higher elastic modulus at the outer radius. However, the disk may be unstable for certain distribution functions.

The transverse force on a drop in an unbounded parabolic flow

1974 ◽  
Vol 62 (1) ◽  
pp. 185-207 ◽  
Author(s):  
Philip R. Wohl ◽  
S. I. Rubinow
Keyword(s):  
Reynolds Number ◽  
Poiseuille Flow ◽  
Weber Number ◽  
Lift Force ◽  
Body Force ◽  
The Body ◽  
Flow Profile ◽  
External Fluid ◽  
Parabolic Flow ◽  
Undisturbed Flow

The steady flow in and around a deformable liquid sphere moving in an unbounded viscous parabolic flow and subject to an external body force is calculated for small values of the ratio of the Weber number to the Reynolds number in the creeping-flow regime. It is found that, in addition to the drag force, the drop experiences a force orthogonal to the undisturbed flow direction. When the body force is absent (neutrally buoyant drop), this lift force tends to drive the drop inwards to the axis, where the undisturbed flow velocity is maximum, i.e., towards a position of lower velocity gradient. In the case for which the parabolic flow profile is a Poiseuille flow profile, the lift force is given by the expression. \[ {\bf F}_1 =-6\pi\mu\epsilon U_0\frac{\alpha +\frac{2}{3}}{\alpha + 1}\bigg(\frac{a}{R_0}\bigg)^4{\bf b}F[1+o(\epsilon)]. \] Here a is the radius of the undeformed sphere, R0 is the radial distance from the position of maximum undisturbed flow U0 at the profile axis to the position of zero flow, ε is the ratio of the Weber number to the Reynolds number, given by ε=μU0T−1, where μ is the external fluid viscosity and T is the surface tension of the drop, α is the ratio of the drop and external fluid viscosities, b is the radial vector from the flow axis to the centre of mass of the drop, and F is a function of α and a dimensionless parameter dependent on the body force that is determined in the analysis. Reasonable agreement is found between the observations by Goldsmith & Mason (1962) of the axial drift of liquid drops in Poiseuille flow and the predictions of the theory herein.

Experimental Results and CFD Simulations of Labyrinth and Pocket Damper Seals for Wet Gas Compression

2015 ◽  
Author(s):  
Giuseppe Vannini ◽  
Matteo Bertoneri ◽  
Kenny Krogh Nielsen ◽  
Piero Iudiciani ◽  
Robert Stronach
Keyword(s):  
Liquid Phase ◽  
Centrifugal Compressor ◽  
Critical Speed ◽  
Volume Fraction ◽  
Material Selection ◽  
Operating Conditions ◽  
Liquid Volume ◽  
Wet Gas ◽  
Gas Compression ◽  
Annular Seals

The most recent development in centrifugal compressor technology is towards wet gas operating conditions. This means the centrifugal compressor has to manage a liquid phase which is varying between 0 to 3% Liquid Volume Fraction (LVF) according to the most widely agreed definition. The centrifugal compressor operation is challenged by the liquid presence with respect to all the main aspects (e.g. thermodynamics, material selection, thrust load) and especially from a rotordynamic viewpoint. The main test results of a centrifugal compressor tested in a special wet gas loop [1] show that wet gas compression (without an upstream separation) is a viable technology. In wet gas conditions the rotordynamic behavior could be impacted by the liquid presence both from a critical speed viewpoint and stability wise. Moreover the major rotordynamic results from the previous mentioned test campaign [2] show that both vibrations when crossing the rotor first critical speed and stability (tested through a magnetic exciter) are not critically affected by the liquid phase. Additionally it was found that the liquid may affect the vibration behavior by partially flooding the internal annular seals and causing a sort of forced excitation phenomenon. In order to better understand the wet gas test outcomes, the authors performed an extensive CFD analysis simulating all the different types of balance piston annular seals used (namely a Tooth on Stator Labyrinth Seal and a Pocket Damper Seal). They were simulated in both steady state and transient conditions and finally compared in terms of liquid management capability. CFD simulation after a proper tuning (especially in terms of LVF level) showed interesting results which are mostly consistent with the experimental outcome. The results also provide a physical explanation of the behavior of both seals, which was observed during testing.

Numerical Simulation of Droplet Flows and Evaluation of Interfacial Area

2002 ◽  
Vol 124 (3) ◽  
pp. 576-583 ◽  
Author(s):  
T. Watanabe ◽  
K. Ebihara
Keyword(s):  
Lattice Boltzmann ◽  
Weber Number ◽  
Volume Fraction ◽  
Interfacial Area ◽  
Force Balance ◽  
Two Phase ◽  
Critical Weber Number ◽  
Boltzmann Method ◽  
Droplet Flows ◽  
Good Agreement

Droplet flows with coalescence and breakup are simulated numerically using the lattice Boltzmann method. It is shown that the rising velocities are in good agreement with those obtained by the force balance and the empirical correlation. The breakup of droplets after coalescence is simulated well in terms of the critical Weber number. A numerical method to evaluate the interfacial area and the volume fraction in two-phase flows is proposed. It is shown that the interfacial area corresponds to the shape, the number and the size of droplets, and the proposed method is effective for numerical evaluation of interfacial area even if the interface changes dynamically.

DNS Study of Collision and Coalescence Over a Wide Range of Volume Fraction

2010 ◽  
Author(s):  
G. Luret ◽  
T. Me´nard ◽  
J. Re´veillon ◽  
A. Berlemont ◽  
F. X. Demoulin
Keyword(s):  
Kinetic Energy ◽  
Weber Number ◽  
Volume Fraction ◽  
Density Ratio ◽  
Liquid Volume ◽  
Kinetic Energy Density ◽  
Two Phase ◽  
Liquid Volume Fraction ◽  
Gas Phases ◽  
Wide Range

Among the different processes that play a role during the atomization process, collisions are addressed in this work. Collisions can be very important in dense two-phase flows. Recently, the Eulerian Lagrangian Spray Atomization (ELSA) model has been developed. It represents the atomization by taking into account the dense zone of the spray. Thus in this context, collisions modeling are of the utmost importance. In this model results of collisions are controlled by the value of an equilibrium Weber number, We*. It is defined as the ratio between the kinetic energy to the surface energy. Such a value of We* has been studied in the past using Lagrangian collision models with various complexity. These models are based on analysis of collisions between droplets that have surface at rest. This ideal situation can be obtained only if droplet agitation created during a collision has enough time to vanish before the next collision. For a spray, this requirement is not always fulfill depending for instance on the mean liquid volume fraction. If there is not enough time, collisions will occur between agitated droplets changing the issue of the collision with respect to the ideal case. To study this effect, a DNS simulation with a stationary turbulence levels has been conducted for different liquid volume fractions in a cubic box with periodic condition in all directions. For liquid volume fraction close to zero the spray is diluted and collisions between spherical droplets can be identified. For a volume fraction close to one, collisions between bubbles are found. For a middle value of the volume fraction no discrete phase can be observed, instead a strong interaction between both liquid and gas phases is taking place. In all this case the equilibrium value of the Weber number We* can be determined. First propositions to determine We* as a function of the kinetic energy, density ratio, surface tension coefficient and the volume fraction will be proposed.

Viscosity Measurement and Modeling for Mixtures of Athabasca Bitumen/n-Pentane at Temperatures Up to 200°C

SPE Journal ◽  
2014 ◽  
Vol 20 (02) ◽  
pp. 226-238 ◽  
Author(s):  
Hossein Nourozieh ◽  
Mohammad Kariznovi ◽  
Jalal Abedi
Keyword(s):  
Heavy Oil ◽  
Volume Fraction ◽  
Weight Fraction ◽  
Viscosity Reduction ◽  
Athabasca Bitumen ◽  
Recovery Processes ◽  
Correlation Models ◽  
In Situ Recovery ◽  
Recovery Methods

Summary The phase-behavior and thermophysical properties of bitumen/solvent systems are of crucial importance for heavy-oil and bitumen in-situ recovery methods. The viscosity reduction as a result of solvent dissolution and/or steam heating is the main recovery mechanism in the solvent-based bitumen-recovery processes. In this paper, the viscosity of bitumen, pentane, and their mixtures at different pentane weight fractions (0.05, 0.1, 0.2, 0.3, 0.4, and 0.5) are accurately measured. The measurements are conducted under conditions applicable for both in-situ recovery methods and the pipeline transportation of heavy oil. The experiments are taken with Athabasca bitumen at temperatures varying from ambient up to 200°C and at pressures up to 10 MPa. The data for the mixtures are evaluated with predictive schemes as well as with correlation models representing certain mixing rules proposed in the literature. The influences of pressure, temperature, and solvent weight fraction on the viscosity of mixtures are considered in the models and evaluated from the experimental data. The results indicated that the power-law model and the Cragoe model (Cragoe 1933) represent the data better than other models that use a volume-fraction basis.

Patterns of Secondary Flow Field in a Circular Tube Caused by Corona Wind Using the Method of Characteristics

2009 ◽  
Author(s):  
Reza Baghaei Lakeh ◽  
Majid Molki
Keyword(s):  
Flow Field ◽  
Electric Field ◽  
Charge Density ◽  
Corona Discharge ◽  
Secondary Flow ◽  
Computational Methods ◽  
Method Of Characteristics ◽  
Body Force ◽  
Circular Tube ◽  
Secondary Flow Field

Corona discharge is widely known as an effective method for improving the characteristics of the flow field and enhancing heat transfer. Distribution of charge density and electric field form a Coulomb body force which acts on the charged particles within the fluid and generates a secondary flow field. The thermal enhancing effects of corona wind are normally dominant in low Reynolds numbers or free convection problems. Although the governing differential equations of corona discharge are relatively simple, solving these equations by conventional computational methods does not yield a smooth solution for charge density and electric field. In particular, the results obtained from finite-volume method suffer from dispersion errors and fluctuations which lead to distorted values of electric body force, and consequently a distorted secondary flow. In this study, the corona discharge in a circular tube with the electrode positioned at the tube centerline is considered. An exact solution for charge density, electric field, and potential distribution along the radius of the tube has been derived analytically using a Lagrangian formulation for the charge density and the Method of Characteristics. It was found that the results of this method do not show any fluctuations or dispersion effects on charge density and electric field. The solution of the electric field provided a body force which was used in the Navier-Stokes equations to obtain the secondary flow in the cross section of the tube. In this paper, the electric and fluid flow fields are presented. The results are compared with those obtained by other computational methods and the differences are discussed.

Movable Rigid Scatterer Model for Flexural Wave Scattering on Thin Plates

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Liang-Wu Cai ◽  
Stephen A. Hambric
Keyword(s):  
Volume Fraction ◽  
Mass Density ◽  
Stop Band ◽  
Body Motion ◽  
Thin Plates ◽  
Flexural Wave ◽  
Fixed Structure ◽  
Limiting Case ◽  
Flexural Wave Scattering ◽  
Lower Frequencies

Rigid scatterers are fundamentally important in the study of scattering of many types of waves. However, in the recent literature on scattering of flexural waves on thin plates, a “rigid scatterer” has been used to represent a clamped boundary. Such a model physically resembles riveting the plate to a fixed structure. In this paper, a movable model for a rigid scatterer that allows rigid-body motion is established. It is shown that, when the mass density of the movable rigid scatterer is much greater than that of the host plate and at high frequencies, the movable rigid scatterer approaches the limiting case that is the riveted rigid scatterer. The single- and multiple-scattering by such scatterers are examined. Numerical examples show that, at the extreme end of lower frequencies, the scattering cross section for the movable model vanishes while that of the riveted models approaches infinity. An array of such movable rigid scatterers can form a broad and well-defined stop band for flexural wave transmission. With a volume fraction above 50%, the spectrum is rather clean: consisting of only an extremely broad stop band and two groups of higher frequency Perot–Fabry resonance peaks. Increasing either scatterer’s mass density or the lattice spacing can compress the spectral features toward lower frequencies.

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