scholarly journals Вклад силы присоединенных масс в формирование пропульсивной силы машущего профиля в вязкой жидкости

2020 ◽  
Vol 46 (17) ◽  
pp. 14
Author(s):  
С.В. Гувернюк ◽  
Я.А. Дынников ◽  
Г.Я. Дынникова ◽  
Т.В. Малахова
Keyword(s):  
Continuous Medium ◽  
Stokes Equations ◽  
Viscous Incompressible Fluid ◽  
General Theorem ◽  
Navier Stokes ◽  
Propulsive Force ◽  
Navier Stokes Equations ◽  
Added Masses ◽  
Hydrodynamic Mechanism ◽  
Angular Oscillations

In the light of the recently proved general theorem on the added mass of bodies in a viscous incompressible fluid, the mechanism of the formation of the propulsive force of the flapping airfoil, which performs harmonic angular oscillations in the flow of a continuous medium, is investigated. The flow is described by the Navier-Stokes equations. The calculations were performed by a meshless numerical method of viscous vortex domains. The mechanism of the formation of a reversed vortex track in the wake behind the flapping profile in the positive traction mode is explained. The dominant contribution of the force of the added masses to the value of the propulsive force is revealed. The results obtained to some extent reveal the hydrodynamic mechanism of action of the caudal fin of underwater creatures.

scholarly journals Vortex motion of a continuous medium depending on the pressure change

2020 ◽  
Vol 2020 (6) ◽  
Author(s):  
Alexander Braginsky
Keyword(s):  
Angular Velocity ◽  
Continuous Medium ◽  
Stokes Equations ◽  
Equations Of Motion ◽  
Vortex Motion ◽  
Pressure Change ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Least Action ◽  
Force Components

Abstract In this paper, we study the vortex motion of a continuous medium, which is described by forces obtained from the principle of least action. It is shown that in a continuous medium the vortex force components are proportional to the velocity and pressure gradient components. This article gives a description of the 2D vortex motion of air in zones of high and low pressure. If the pressure decreases, the angular velocity of rotation of the continuous medium increases, whereas if the pressure increases, the angular velocity fades. The lifting force is obtained due to the vortex movement of air in the form of a funnel. It is shown that the vortex force contains a vortex term of the Euler hydrodynamic equations with a relative factor equal to the velocity of the continuous medium squared divided by the sound velocity squared. To describe the motion of a continuous medium correctly it is necessary to replace the forces obtained by Euler with the forces obtained from the minimum of action in the equations of motion. It is concluded that vortex motions and turbulence are described by the obtained equations of motion, and not by the Navier–Stokes equations. Most likely, this is related to the Problem of the Millennium description of turbulence announced at the International Congress of Mathematics in 2000.

Centrifugal instabilities during spin-down to rest in finite cylinders. Numerical experiments

1981 ◽  
Vol 102 ◽  
pp. 329-352 ◽  
Author(s):  
G. P. Neitzel ◽  
Stephen H. Davis
Keyword(s):  
Stokes Equations ◽  
Viscous Incompressible Fluid ◽  
Onset Time ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Initial State ◽  
Navier Stokes Equations ◽  
Aspect Ratios ◽  
Gradient Forces ◽  
Axis Of Symmetry

A cylinder filled with a viscous, incompressible fluid is in an initial state of rigid-body rotation about its axis of symmetry. If the container is brought to rest impulsively, the resulting unsteady spin-down flow may be subject to sidewall instabilities due to an imbalance between centrifugal and pressure gradient forces. These instabilities are examined numerically using a finite-difference simulation to integrate the axisymmetric Navier–Stokes equations for a variety of aspect ratios and Reynolds numbers. The Taylor–Görtler vortex-wavelength spectrum, the torque and the angular momentum histories are calculated. Criteria for the onset time for instability and the spin-down time are given. The effects of the enhanced mixing due to instability on the spin-down characteristics and torque are discussed. The results are compared with experiment.

scholarly journals Stability Analysis of Symmetrical Rotors Partially Filled with a Viscous Incompressible Fluid

2001 ◽  
Vol 7 (5) ◽  
pp. 301-310 ◽  
Author(s):  
Zhu Changsheng
Keyword(s):  
Stability Analysis ◽  
Incompressible Fluid ◽  
Stokes Equations ◽  
Viscous Incompressible Fluid ◽  
Damping Ratio ◽  
Navier Stokes ◽  
Fluid Viscosity ◽  
Navier Stokes Equations ◽  
Rotor Systems ◽  
The Stability

On the basis of the linearized fluid forces acting on the rotor obtained directly by using the two-dimensional Navier-Stokes equations, the stability of symmetrical rotors with a cylindrical chamber partially filled with a viscous incompressible fluid is investigated in this paper. The effects of the parameters of rotor system, such as external damping ratio, fluid fill ratio, Reynolds number and mass ratio, on the unstable regions are analyzed. It is shown that for the stability analysis of fluid filled rotor systems with external damping, the effect of the fluid viscosity on the stability should be considered. When the fluid viscosity is included, the adding external damping will make the system more stable and two unstable regions may exist even if rotors are isotropic in some casIs.

Vibrations of Circular Cylindrical Shells With Nonuniform Constraints, Elastic Bed and Added Mass Coupled to Internal, External and Annular Flow

2002 ◽  
Author(s):  
M. Amabili ◽  
R. Garziera
Keyword(s):  
Annular Flow ◽  
Stokes Equations ◽  
Computer Code ◽  
Inviscid Flow ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Viscous Forces ◽  
Added Masses ◽  
Circular Cylindrical Shells ◽  
Lumped Masses

The effect of steady viscous forces on vibrations of shell with internal and annular flow has been considered by using the time-mean Navier-Stokes equations. The model developed by Amabili & Garziera (2000), capable of simulating shells with non-uniform boundary conditions, added masses and partial elastic bed, has been extended to include non-uniform prestress. The effect of steady viscous forces has been added to the inviscid flow formulation considered by Amabili & Garziera (2002). The computer code DIVA has been developed by using the model developed in the present study. It has been validated by comparison with available results for shells with uniform constraints and has been used to study shells with non-uniform constraints and added lumped masses.

Time delay and Lagrangian approximation for Navier–Stokes flow

Analysis ◽  
2015 ◽  
Vol 35 (4) ◽  
Author(s):  
Nazgul Asanalieva ◽  
Carolin Heutling ◽  
Werner Varnhorn
Keyword(s):  
Fluid Flow ◽  
Time Delay ◽  
Incompressible Fluid ◽  
Stokes Flow ◽  
Stokes Equations ◽  
Viscous Incompressible Fluid ◽  
Navier Stokes ◽  
Incompressible Fluid Flow ◽  
Navier Stokes Equations

AbstractWe consider the nonstationary nonlinear Navier–Stokes equations describing the motion of a viscous incompressible fluid flow for

VORTICAL FLOW OF INCOMPRESSIBLE VISCOUS FLUID IN FINITE CYLINDER

2008 ◽  
Vol 13 (3) ◽  
pp. 371-381
Author(s):  
Harijs Kalis ◽  
Ilmārs Kangro
Keyword(s):  
Stokes Equations ◽  
Viscous Incompressible Fluid ◽  
Velocity Fields ◽  
Vortical Flow ◽  
Finite Cylinder ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vortex Lines ◽  
Smooth Pipe ◽  
Effective Use

The effective use of vortex energy in production of strong velocity fields by different devices is one of the modern areas of applications, developed during the last decade. In this paper the distribution of velocity field for viscous incompressible fluid in a pipe with a system of finite number of circular vortex lines, positioned on the inner surface of the finite cylinder is calculated. The approximation of the corresponding boundary value problem for the Navier‐Stokes equations is based on the finite difference method. This procedure allows us to reduce the 2D problem decribed by the system of Navier‐ Stokes PDEs to the monotonous difference equations. Calculations are done using the computer program Matlab and the following regimes are calculated: a) the flow in a smooth pipe; b) the flow, poured inside a pipe through the circle; c) the flow, poured inside a pipe through the ring. The model is investigated for different values of parameters Re (Reynolds number), G(swirl number) and A (vortex intensity).

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