Micellar confinement disrupts collective structure and accelerates collective dynamics of encapsulated water

2018 ◽  
Vol 20 (16) ◽  
pp. 11454-11469 ◽  
Author(s):  
Philipp Honegger ◽  
Michael Schmollngruber ◽  
Othmar Steinhauser
Keyword(s):  
Analytical Model ◽  
Reverse Micelles ◽  
Numerical Study ◽  
Dielectric Spectrum ◽  
Collective Dynamics ◽  
Collective Structure

Detailed numerical study of the dielectric spectrum of zwitterionic reverse micelles is combined with interpretation using a new semi-quantitative analytical model.

scholarly journals Model of thermal buoyancy in cavity-ventilated roof constructions

2021 ◽  
pp. 174425912098418
Author(s):  
Toivo Säwén ◽  
Martina Stockhaus ◽  
Carl-Eric Hagentoft ◽  
Nora Schjøth Bunkholt ◽  
Paula Wahlgren
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Numerical Study ◽  
Air Flow ◽  
Wind Pressure ◽  
Air Flow Rate ◽  
Test Set ◽  
Air Cavity ◽  
Thermal Buoyancy ◽  
The Impact

Timber roof constructions are commonly ventilated through an air cavity beneath the roof sheathing in order to remove heat and moisture from the construction. The driving forces for this ventilation are wind pressure and thermal buoyancy. The wind driven ventilation has been studied extensively, while models for predicting buoyant flow are less developed. In the present study, a novel analytical model is presented to predict the air flow caused by thermal buoyancy in a ventilated roof construction. The model provides means to calculate the cavity Rayleigh number for the roof construction, which is then correlated with the air flow rate. The model predictions are compared to the results of an experimental and a numerical study examining the effect of different cavity designs and inclinations on the air flow rate in a ventilated roof subjected to varying heat loads. Over 80 different test set-ups, the analytical model was found to replicate both experimental and numerical results within an acceptable margin. The effect of an increased total roof height, air cavity height and solar heat load for a given construction is an increased air flow rate through the air cavity. On average, the analytical model predicts a 3% higher air flow rate than found in the numerical study, and a 20% lower air flow rate than found in the experimental study, for comparable test set-ups. The model provided can be used to predict the air flow rate in cavities of varying design, and to quantify the impact of suggested roof design changes. The result can be used as a basis for estimating the moisture safety of a roof construction.

Spin-Up From Rest of a Two-Layer Liquid in a Cylinder

1994 ◽  
Vol 116 (4) ◽  
pp. 808-814 ◽  
Author(s):  
Kwan Yeop Kim ◽  
Jae Min Hyun
Keyword(s):  
Analytical Model ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Bottom Layer ◽  
Meridional Flow ◽  
Individual Layer ◽  
Ekman Number ◽  
Radial Profiles ◽  
The Individual

A numerical and analytical study is made of spin-up from rest of a two-layer liquid in a rapidly rotating cylinder. The overall system Ekman number is small. The density of the top layer is smaller than that of the bottom layer (ρ1/ρ2<1.0), but the ratio of the individual layer kinematic viscosities is arbitrary (v1/v2<1.0 or v1/v2>1.0). The highlights of the analytical model, which is based on amended formulations of the Wedemeyer-Gerber-Homicz flow configurations, are briefly recapitulated. Comprehensive numerical solutions are secured to the time-dependent Navier–Stokes equations. The numerical solutions are validated by comparing the maximum interface displacements with the available experimental data as well as the analytical model predictions. Descriptions are made of the prominent characteristics of the interface shape for the two regimes of v1/v2<1.0 and v1/v2 > 1.0. Details of the azimuthal and meridional flow structures are illustrated by exploiting the numerical solutions. The computed meridional flows are compatible with the basic assumptions embedded in the development of the analytical model. Sequential plots of the radial profiles of azimuthal velocities are presented. These show that the global spin-up process is substantially accomplished over (En−1/2Ω−1), where En denotes the value of the smaller Ekman number of the two layers. The numerical study gives credence to the reliability and accuracy of the simplified analytical model.

Experimental and Numerical Study of Motion of Rotating Drill Pipe Owing to Magnus Effect

2019 ◽  
Author(s):  
Tomoya Inoue ◽  
Hiroyoshi Suzuki ◽  
Tokihiro Katsui ◽  
Keita Tsuchiya ◽  
Yusuke Notani
Keyword(s):  
Analytical Model ◽  
Rotational Speed ◽  
Numerical Study ◽  
Flow Direction ◽  
Drill Pipe ◽  
Ocean Current ◽  
Gas Drilling ◽  
Pipe Model ◽  
Magnus Effect ◽  
Drilling Operations

Abstract During riserless drilling operations conducted in some scientific drillings and the initial stages of all oil and gas drilling operations, drill pipe motions such as vortex induced vibration, whirl motion, and motion due to the Magnus effect are generated. The last motion represents an interesting and important phenomenon that generates a lift force in addition to a drag force due to the ocean current and the rotation of the drill pipe. Accordingly, this study focuses on the drill pipe motions owing to the Magnus effect. An analytical model of a drill pipe was established by applying an absolute nodal coordinate formulation (ANCF) that can capture the behavior of a relatively flexible and long pipe, such as a drill pipe. The lifting and drag forces are calculated using computational fluid dynamics (CFD), and the lift and drag coefficients are calculated for several different drill pipe rotational velocities and ocean current velocities. A series of model experiments were conducted in a towing tank, with changing water flow velocities and rotational speed of the drill pipe model to observe the corresponding changes in the Magnus effect and to measure the resulting drill pipe motions. Additionally, the resulting drag and lift forces were measured. It was observed from the experiments that the motions in the cross-flow direction increased as the rotational speed of the drill pipe model increased, and that the lifting force increased as the rotational speed increased. The drill pipe motions were then simulated using a previously established analytical model and the results of the CFD simulations. The results of the simulations were evaluated against the results of the experiments, and reasons for observed discrepancies are discussed.

Analytical Model to Establish the Thermal Conductivity of Porous Structure

2014 ◽  
Vol 69 (1) ◽  
Author(s):  
C. H. Mao ◽  
M. A. Othuman Mydin ◽  
X. B. Que
Keyword(s):  
Thermal Conductivity ◽  
Porous Structure ◽  
Pore Size ◽  
Uniform Distribution ◽  
Analytical Model ◽  
Numerical Study ◽  
Fire Retardant ◽  
Mass Conservation ◽  
Intumescent Coating ◽  
Pore Size Distributions

The presented research paper deals with analytical method to determine the thermal conductivity of porous material (intumescent coating) where the main objective is to assess whether it is possible to treat the voids in intumescent coating as having a uniform diameter. Considering the nature of intumescent coating, the mechanisms of its fire retardant properties are expansion and heat absorption. A predictive model should therefore include prediction of expansion behaviour, energy and mass conservation based on both physical and chemical behaviour, and also thermal conductivity of the coating. A 3-D analytical model will be developed to determine the thermal conductivity of intumescent coating. Finite Element simulations using ABAQUS also will be performed to assess the influence of different pore size distributions. The results of this numerical study indicate that, given the same porosity, the overall thermal conductivity of the porous structure is very close to that with uniform distribution of pores of the dominant size. This strongly suggests that, given the difficulty of obtaining precise pore size distribution, it is reasonable to treat an intumescent coating as having a uniform distribution of pores of the same size.

scholarly journals Comparison of an analytical and computational fluid-dynamics models of a commercial Ranque-Hilsch vortex tube operating with Air and Methane

2019 ◽  
Vol 9 (2) ◽  
pp. 61-71
Author(s):  
Luz Marlen Ahumada ◽  
Antonio José Bula Silvera ◽  
Kevin Andres Melendez Valencia ◽  
Julio Medina Suarez
Keyword(s):  
Analytical Model ◽  
Vortex Tube ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Preliminary Information ◽  
Industrial Implementation ◽  
Inlet Conditions ◽  
Dynamics Models

This paper presents a comparison between the behavior predicted by a computational fluid-dynamic model (CFD) and an analytical model for a commercial vortex tube using air and methane as working fluids, in addition to a three-dimensional mesh for this purpose. The numerical simulation of the turbulent, compressible and high vorticity flow was carried out using RANS equations, the Realizable k-e turbulence model and STAR-CCM+ as software for the equations solution. The variables measured in this work were temperature, pressure and velocity at the exit nozzles of the vortex generator and the tube discharges, resulting in errors of less than 16% between CFD and the analytical model. This numerical study represents a first approximation of the vorticityphenomenon and has been developed in order to establish a prototype simulation model that provides, under certain inlet conditions to the process, preliminary information on the vortex tube industrial implementation for obtaining liquefied natural gas.

An Investigation of the Damping Effects of Various Gas Environments on a Vibratory MEMS Device

2009 ◽  
Author(s):  
Seong Jin Kim ◽  
Robert Dean ◽  
Robert Jackson ◽  
George Flowers
Keyword(s):  
Experimental Investigation ◽  
Analytical Model ◽  
Numerical Study ◽  
Experimental Setup ◽  
Mems Device ◽  
Damping Effects

An experimental investigation of the damping effects in several different gas chemistries on a vibrating micromachined structure was conducted. A corresponding numerical study using an analytical model was also performed and the results correlated with the experimental observations. Both the experimental setup/procedure and the analytical model are described in detail. A summary of the results is presented and conclusions/observations discussed.

scholarly journals Numerical Study of Power Loss and Lubrication of Connecting Rod Big-End

Lubricants ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 47 ◽  
Author(s):  
Abbas Razavykia ◽  
Cristiana Delprete ◽  
Paolo Baldissera
Keyword(s):  
Analytical Model ◽  
Power Loss ◽  
Numerical Study ◽  
Hydrodynamic Lubrication ◽  
Computation Time ◽  
Hydrodynamic Pressure ◽  
Mobility Model ◽  
Accurate Estimation ◽  
Connecting Rod ◽  
Numerical Effort

A hydrodynamic lubrication analysis for connecting rod big-end bearing is conducted. The effects of engine speed, operating condition, lubricant viscosity and oil temperature on tribological performance of big-end bearing have been examined. Force equilibrium is solved to define instantaneous eccentricity between journal and bearing to have accurate estimation of oil film thickness at interface of connecting rod big-end bearing and crankpin. Connecting rod big-end is treated as π film hydrodynamic journal bearing and finite difference scheme is applied to calculate generated hydrodynamic pressure and frictional power loss at each crank angle. Beside the development of analytical formulation, well-known Mobility model introduced by Booker has been employed to be compared with the analytical model. The presented analytical model reduces the complexity and the numerical effort with respect to Mobility method, thus shortening the computation time. The simulation results show good agreement between analytical model, Mobility approach and experimental data.

scholarly journals Hydrodynamics of Clumpy Flows: Application to the PNe

2003 ◽  
Vol 209 ◽  
pp. 201-202
Author(s):  
A. Y. Poludnenko ◽  
A. Prank ◽  
E. G. Blackman
Keyword(s):  
Analytical Model ◽  
Numerical Experiments ◽  
Numerical Study ◽  
Planetary Nebulae ◽  
Inhomogeneous Media ◽  
Two Dimensional ◽  
Mass Loading ◽  
Planar Shock ◽  
Astrophysical Flows

Many astrophysical flows occur in inhomogeneous media. We present results of a hydrodynamic numerical study of the interaction of a steady, planar shock/supersonic postshock flow with a system of embedded cylindrical clouds in a two-dimensional geometry and describe an analytical model of the evolution of such systems. Finally we discuss mass-loading in such systems and the applicability of the results to the planetary nebulae (PNe).The most recent results and animations of the numerical experiments described in this paper can be found at www.pas.rochester.edu/~wma.

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