Numerical Investigation of the Drag and Lift Forces Acting on Impenetrable Rotating Spherical Nano-Particle

2008 ◽  
Author(s):  
M. R. Meigounpoory ◽  
A. Rahi ◽  
A. Mirbozorgi
Keyword(s):  
Lift Coefficient ◽  
Three Dimensional ◽  
Slip Boundary Condition ◽  
Slip Condition ◽  
Nano Particle ◽  
Slip Coefficient ◽  
Slip Boundary ◽  
Lift Forces ◽  
Drag And Lift ◽  
Drag And Lift Coefficient

The drag and lift forces acting on a rotating impenetrable spherical suspended nano-particle in a homogeneous uniform flow are numerically studied by means of a three-dimensional numerical simulation with slip boundary condition. The effects of both the slip coefficient and rotational speed of the nanosphere on the drag and lift forces are investigated for Reynolds numbers in the range of 0.1 < Re < 100. Increase of rotation increases the drag and lift force exerted by flow at the surface of nano-sphere. By increasing slip coefficient the values of drag and lift coefficients decreases. At full slip condition, rotation of the nano-sphere has not significant effects on the drag and lift coefficient values moreover the lift coefficient of flow around the rotating spherical particle will be vanished. Present numerical results at no-slip condition are in good agreements with certain results of flow around of rotating sphere.

Slip over rough and coated surfaces

1994 ◽  
Vol 273 ◽  
pp. 125-139 ◽  
Author(s):  
Michael J. Miksis ◽  
Stephen H. Davis
Keyword(s):  
Slip Boundary Condition ◽  
Slip Condition ◽  
Slip Coefficient ◽  
Outer Flow ◽  
Navier Slip ◽  
Two Fluids ◽  
Slip Boundary ◽  
Lubricating Film ◽  
Effective Slip ◽  
Coated Surfaces

We study the effect of surface roughness and coatings on fluid flow over a solid surface. In the limit of small-amplitude roughness and thin lubricating films we are able to derive asymptotically an effective slip boundary condition to replace the no-slip condition over the surface. When the film is absent, the result is a Navier slip condition in which the slip coefficient equals the average amplitude of the roughness. When a layer of a second fluid covers the surface and acts as a lubricating film, the slip coefficient contains a term which is proportional to the viscosity ratio of the two fluids and which depends on the dynamic interaction between the film and the fluid. Limiting cases are identified in which the film dynamics can be decoupled from the outer flow.

Three-dimensional viscoelastic simulation of the effect of wall slip on encapsulation in the coextrusion process

2013 ◽  
Vol 33 (7) ◽  
pp. 625-632 ◽  
Author(s):  
Hesheng Liu ◽  
Xiaozhen Deng ◽  
Yibin Huang ◽  
Xingyuan Huang ◽  
Mengshan Li
Keyword(s):  
Flow Rate ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Wall Slip ◽  
Slip Boundary Condition ◽  
The Finite Element Method ◽  
Slip Coefficient ◽  
Melt Flow Rate ◽  
Slip Boundary ◽  
Interface Profile

Abstract A three-dimensional viscoelastic numerical simulation was developed for a two-layer coextrusion through a rectangular channel by using the finite element method. The Phan-Thien and Tanner model was considered as viscoelastic constitutive equations. The generalized Navier’s law was adopted to found the slip boundary condition. The numerical results of the effects of the wall slip coefficient and the flow rate on the interface profile and the degree of encapsulation were compared with the experimental results of previous researchers. It was found that the interfacial offset and the degree of encapsulation increased with the increase of the wall slip coefficient and the flow rate, and the growing rate was large when the wall slip coefficient was between 106 and 108. We were able to control the interface shape and the degree of encapsulation at the die exit by varying the wall slip coefficient and the magnitude of the melt flow rate.

Application of CFD Technology Analyzing the Three-Dimensional Aerodynamic Behavior of Dimpled Golf Balls

2002 ◽  
Author(s):  
L. L. Ting
Keyword(s):  
Lift Coefficient ◽  
Three Dimensional ◽  
Modeling Method ◽  
Flight Behavior ◽  
Surface Design ◽  
Fluid Field ◽  
Ball Surface ◽  
Pattern Distribution ◽  
Drag And Lift ◽  
Drag And Lift Coefficient

A computational modeling method using the CFD codes GAMBIT and FLUENT jointly has been developed for analyzing the three-dimensional aerodynamic behavior of surface dimpled golf balls. Drag and lift coefficient values and fluid field solutions have been obtained for the balls with three different types of dimple pattern distributions, which consist of the dimples with the same or different pocket sizes and depths. The baseline case golf ball carries 422 circular dimples with the dimple distribution pattern very similar to that of a Spalding TOP-FLITE PLUS II ball. The computed drag and lift coefficients of this baseline ball stationary or spinning have been made to compare with some published wind-tunnel experimental results, and the agreement was found to be good. This indicates that the modeling method developed is relevant and suitable for predicting the ball flight behavior for varying dimple geometry and dimple pattern distribution designs. From this, the necessary ball surface design parameter changes can be found either to enhance or to limit the ball’s aerodynamic performance, which controls and determines the ball flying distance and trajectory accuracy after initial impact.

An Experimental Investigation Assessing the Validity of Quasi-Static Calculations for an Oscillating Hydrofoil

2011 ◽  
Author(s):  
Rajan Fernandez ◽  
Keith Alexander
Keyword(s):  
Steady Flow ◽  
Strouhal Number ◽  
Strong Dependence ◽  
Lift Coefficient ◽  
Experimental Program ◽  
Design Data ◽  
Drag And Lift ◽  
Drag And Lift Coefficient ◽  
Lift And Drag ◽  
Human Powered

Inspired by animals, flapping wing propulsion has been of interest since the early 1900s. Flapping hydrofoil propulsion has been attempted by designers of human powered watercraft because of the novelty and the apparent high theoretical efficiency, but with limited success. The earliest human powered hydrofoil, the Wasserlaufer, was invented by Julius Schuck in 1953. The first really successful human powered hydrofoil, the Trampofoil, was invented by Alexander Sahlin in 1998. While these craft function adequately the design data for flapping hydrofoils is inadequate or not available. This paper describes an experimental program and initial results for the required data. To design a vehicle with a lifting and thrusting oscillating hydrofoil the force that the hydrofoil will exert on the vehicle through its entire oscillating cycle must ideally be known. The force profiles could be estimated via quasi-static calculations based on steady flow lift and drag coefficients, but these often do not cover the full 360 degree range that can be required and there is doubt that the steady flow coefficients properly represent the dynamic situation of an oscillating hydrofoil. Hence a valuable process would be one that could determine dynamic drag and lift coefficient loops as function of the Strouhal number, heaving and pitching profiles. To work toward the collection of this information, experimental data is being recorded in a towing tank with an oscillating NACA4415 hydrofoil over a range of Strouhal numbers and types of oscillating profiles. While there are still some limitations to the experimental equipment preliminary experimental results show the limitations of using quasi-static calculations and go some way to providing the design data for the hydrofoil section tested. We conclude that quasi-static calculations based on the gliding coefficient curve for for an oscillating hydrofoil are only valid for very small Strouhal numbers (St≪0.05). We have shown that as the Strouhal number increases, the error in such calculations increases very rapidly. We also note that the lift coefficient of the hydrofoil has a strong dependence on the angle of attack and is not affected by the gliding stall.

scholarly journals The mechanics of the Tollmien-Schlichting wave

1996 ◽  
Vol 312 ◽  
pp. 107-124 ◽  
Author(s):  
Peter G. Baines ◽  
Sharan J. Majumdar ◽  
Humio Mitsudera
Keyword(s):  
Boundary Layer ◽  
Outer Part ◽  
Slip Boundary Condition ◽  
Slip Condition ◽  
Linear Solution ◽  
Slip Boundary ◽  
Uniform Shear ◽  
Blasius Boundary Layer ◽  
Partial Mode ◽  
Tollmien Schlichting

We describe a mechanistic picture of the essential dynamical processes in the growing Tollmien-Schlichting wave in a Blasius boundary layer and similar flows. This picture depends on the interaction between two component parts of a disturbance (denoted ‘partial modes’), each of which is a complete linear solution in some idealization of the system. The first component is an inviscid mode propagating on the vorticity gradient of the velocity profile with the free-slip boundary condition, and the second, damped free viscous modes in infinite uniform shear with the no-slip condition. There are two families of these viscous modes, delineated by whether the phase lines of the vorticity at the wall are oriented with or against the shear, and they are manifested as resonances in a forced system. The interaction occurs because an initial ‘inviscid’ disturbance forces a viscous response via the no-slip condition at the wall. This viscous response is large near the resonance associated with the most weakly damped viscous mode, and in the unstable parameter range it has suitable phase at the outer part of the boundary layer to increase the amplitude of the inviscid partial mode by advection.

Boundary Drag Force Acting on an Impenetrable Nano-Particle

2010 ◽  
Author(s):  
H. Karrabi ◽  
M. H. Kebriai ◽  
M. R. Meigounpoury
Keyword(s):  
Fundamental Problem ◽  
Aqueous Media ◽  
Slip Boundary Condition ◽  
Reynolds Numbers ◽  
Nano Particles ◽  
Nano Particle ◽  
Coating Materials ◽  
Technical Problems ◽  
Slip Boundary ◽  
Automotive Engines

Flow over nano spheres is a fundamental problem encountered in many engineering technical problems and the motion of nano-particles is important in many technical areas, for example nano-organizms motion in aqueous media, super hydrophobic spray for coating materials, nano-capsules for detecting cancer, and additive nano-particles in oil and fuel for automotive engines. In this paper computations are performed to determine the steady flow forces acting on the stationary nano-tube for Reynolds numbers in the range of 0.1&lt;Re&lt;40 and 0.01&lt;Kn&lt;0.1 with the slip boundary condition. A single dimensionless parameter, the so-called slip number (Tr), is defined to account for the slip at the nano-particle boundary., Increasing slip causes to delay of flow separation around the nano-tube surface. Numerical results confirm that slip variations can not affect on the drag coefficient values at low Reynolds regime. At higher Reynolds number increasing slip causes to drag reduction of flow around the Nano-Tube.

Influence of the Key Factors on the Wall Slip Phenomenon in Micro Flow

2012 ◽  
Vol 472-475 ◽  
pp. 2415-2421
Author(s):  
Pei Qian He ◽  
Yan Lou ◽  
Xiao Yu Wu
Keyword(s):  
Shear Stress ◽  
Flow Analysis ◽  
Wall Slip ◽  
Slip Boundary Condition ◽  
Key Factors ◽  
Slip Coefficient ◽  
Slip Boundary ◽  
Navier’S Slip ◽  
Micro Flow ◽  
Slip Phenomenon

Aimed at the wall slip phenomenon of micro flow, the wall slip boundary condition was added to simulate the process of the micro flow by Polyflow based on the traditional flow analysis method. The effect of the wall slip on the micro flow was verified by comparing the pressure difference data obtained from the simulation with the quoted test data. In addition, based on the Generalized Navier’s slip law, the shear stress and slip coefficient were researched by the numerical simulation analyses to find out the influence of the key factors on the phenomenon of wall slip. The results show that the phenomenon of wall slip is an important factor that cannot be ignored in the micro flow. And only under the high shear stress, the wall slip phenomenon will have an obvious influence on the micro flow. Along with the decrease of the slip coefficient, the wall slip phenomenon becomes more apparent and the micro flow tends to be stable.

Numerical Study on Deformation Behavior of a Fluid Particle Under Shear Flow

2011 ◽  
Author(s):  
Youngho Suh ◽  
Changhoon Lee
Keyword(s):  
Shear Flow ◽  
Deformation Behavior ◽  
Present Method ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Conditions ◽  
Droplet Deformation ◽  
Lift Forces ◽  
Drag And Lift ◽  
Acting Force

In this work, we studied the deformation behavior of a droplet under the various flow conditions. The droplet deformation is calculated by a level-set method. In order to determine the acting force on a particle in shear flow field, we propose the feedback forces which can maintain particle position with efficient handling of deformation. Computations were carried out to investigate the deformation behavior of a droplet caused by the surrounding gaseous flow and the effect of the deformation on the droplet characteristics with various dimensionless parameters. Based on the numerical results, we observed that drag and lift forces acting on a droplet depend strongly on the deformation. Also, the present method is proven to be applicable to a three-dimensional deformation of droplet in shear flow, which cannot be properly analyzed by the previous studies. The drag and lift forces obtained from the present numerical method are favorably compared with the data reported in the literature.

Numerical investigation of flow around a structure using Navier-slip boundary conditions

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sang-Do Choi ◽  
Tae-Soo Eum ◽  
Eun Taek Shin ◽  
Chang Geun Song
Keyword(s):  
Boundary Conditions ◽  
Slip Length ◽  
Lift Coefficient ◽  
Vortex Formation ◽  
Slip Condition ◽  
Partial Slip ◽  
Slip Boundary Conditions ◽  
Content Type ◽  
Navier Slip ◽  
Slip Boundary

Purpose Complicated motion of vortex is frequently observed in the wake of islands. These kinds of swirling fluid cause the trap of sediments or pollutants, subsequently inducing the dead zone, odor or poor water quality. Therefore, the understanding of flow past a circular cylinder is significant in predicting water quality and positioning the immersed structures. This study aims to investigate the flow properties around a structure using Navier-slip boundary conditions. Design/methodology/approach Boundary conditions are a major factor affecting the flow pattern because the magnitude of flow detachment on a surface can redistribute the tangential stress on the wall. Therefore, the authors performed an analysis of laminar flow passing through a circular structure to investigate the effect of boundary conditions on the flow pattern. Findings The authors examined the relationship between the partial-slip boundary conditions and the flow behavior at low Reynolds number past a circular cylinder considering velocity and vorticity distributions behind the cylinder, lift coefficient and Strouhal number. The amplitude of lift coefficient by the partial slip condition had relatively small value compared with that of no-slip condition, as the wall shear stress acting on the cylinder became smaller by the velocity along the cylinder surface. The frequency of the asymmetrical vortex formation with partial slip velocity was increased compared with no-slip case due to the intrinsic inertial effect of Navier-slip condition. Originality/value The ability to engineer slip could have dramatic influences on flow, as the viscous dominated motion can lead to large pressure drops and large axial dispersion. By the slip length control, no-slip, partial-slip and free-slip boundary conditions are tunable, and the velocity distributions at the wall, vortex formation and wake pattern including the amplitude of lift coefficient and frequency were significantly affected by slip length parameter.

scholarly journals Aerodynamics of aero-engine installation

2016 ◽  
Vol 230 (14) ◽  
pp. 2673-2692 ◽  
Author(s):  
Tomasz P Stańkowski ◽  
David G MacManus ◽  
Christopher TJ Sheaf ◽  
Robert Christie
Keyword(s):  
Lift Coefficient ◽  
Aerodynamic Characteristics ◽  
Installation Effects ◽  
Through Flow ◽  
Aero Engine ◽  
Flow Capture ◽  
Research Programmes ◽  
Drag And Lift ◽  
Drag And Lift Coefficient ◽  
Aircraft Aerodynamics

This paper describes current progress in the development of methods to assess aero-engine airframe installation effects. The aerodynamic characteristics of isolated intakes, a typical transonic transport aircraft as well as a combination of a through-flow nacelle and aircraft configuration have been evaluated. The validation task for an isolated engine nacelle is carried out with concern for the accuracy in the assessment of intake performance descriptors such as mass flow capture ratio and drag rise Mach number. The necessary mesh and modelling requirements to simulate the nacelle aerodynamics are determined. Furthermore, the validation of the numerical model for the aircraft is performed as an extension of work that has been carried out under previous drag prediction research programmes. The validation of the aircraft model has been extended to include the geometry with through flow nacelles. Finally, the assessment of the mutual impact of the through flow nacelle and aircraft aerodynamics was performed. The drag and lift coefficient breakdown has been presented in order to identify the component sources of the drag associated with the engine installation. The paper concludes with an assessment of installation drag for through-flow nacelles and the determination of aerodynamic interference between the nacelle and the aircraft.

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