Self-similar solutions for the two dimensional non-Newtonian Navier-Stokes

equation

Imre Ferenc Barna

Wigner Research Center of the Hungarian Academy of Sciences

2 Dec. 2013 Zimányi School’13

Outline

Solutions of PDEs self-similar, traveling wave

Equations of various dissipative flows &my2/3D Ansatz and geometry my solutions, replay from

last years

non-newtonian Navier-Stokes equation with

the same Ansatz, some part of the solutions

Summary & Outlook

Physically important solutions of PDEs

- Travelling waves:

arbitrary wave fronts

u(x,t) ~ g(x-ct), g(x+ct)

- Self-similar

Sedov, Barenblatt, Zeldovich

in Fourier heat-conduction

Physically important solutions of PDEs II

- generalised self-similar:

- one case: blow-up solution:

goes to infinity in finite time

other forms are available too

- additional:

additive separable

multiplicative separable

generalised separable eg.

Various dissipative fluid equations

Non-compressible and Newtonian (I)

Compressible and Newtonian (II)

Non-compressible and Non-Newtonian (III)

Compressible and Non-Newtonian tooo complicated, we will see…

0

Euler description; Cartesian coordinate; v velocity field, p pressure, a external field viscosity, density, kompressibility, E stress tensor

My 3 dimensional Ansatz

A more general function does not work for N-S

The final applied forms:

Geometrical meaning: all v components with coordinate constrain x+y+z=0lie in a plane = equivalent

The non-compressible Newtonian Navier-Stokes equation(I)

just to write outall the coordinates:

Considering the most general Cartesian case:

as constraints the exponents:universality relations, are all fixed no free paramater(s)

Solutions of the ODE

a single Eq. remains

Kummer is spec. func.

Solutions of N-S

I.F. Barna http://arxiv.org/abs/1102.5504Commun. Theor. Phys. 56 (2011) 745-750

analytic only for one velocity component

Geometrical explanation:Naver-Stokes makes a getting a multi-valued surfacedynamics of this plane

all v components with coordinate constrain x+y+z=0lie in a plane = equivalent

for fixed space it decays in timet^-1/2 KummerT or U(1/t)

Other analytic solutions Without completeness, usually from Lie algebra studies all are for non-compressible N-S

Presented 19 various solutionsone of them is:

Sedov, stationary N-S, only the angular part

Solutions are Kummer functions as well

Ansatz:

“Only” Radial solution for 2 or 3 D

Ansatz:

Ansatz:

The compressible Newtonian Navier-Stokes eq. (II)

most general case:

polytropic EOS

as constraints the exponents are not fixed:universality relations are depend on the EOS exponent

`There are different regimes for different ns

n > 1 all exponents are positive decaying, spreading solutions for speed and densityn = 1 see above-1 ≤ n ≤ +1 decaying and spreading density & enhancing velocity in timen ≠ -1n ≤ -1 sharpening and enhancing density & decaying and sharpening velocity

Relevant physics is for n >1

en

`

The compressible Newtonian Navier-Stokes eq. (II)

there is an ODE for the density with analytic solutions for any n BUT more important the ODE for the velocity field:

For n =1/2 and n= 3/2 HeunT functionstooo elaborate BUT for n=2 we have the Whitakker functions

The solution for the non-compressible case

There is no kappa 0 limit to compare the results

The compressible Newtonian Navier-Stokes eq. (II)

Solutions for the same parameters red is the non/compressible and blue is the compresible solution nu = 0.1, kappa =1, c1 = 1

the compresible solutions for kappa = 0.1,1,2 values red, blue green

I.F. Barna http://arxiv.org/abs/1309.0703 & under publication

The non-compressible non-newtonian

Navier-Stokes eq. for 2D (III)Abs value of the tensor in 2D, in 3D much longer

There are existence theorems for weak solutions for some rsOur Ansatz:

The non-compressible non-newtonian

Navier-Stokes eq. for 2D (III)

For C1 =0, mu_1 = 0.1

under heavy investigation

Large number of solutions (20), some of them are explicit with compact support

The non-compressible non-newtonian

Navier-Stokes eq. for 2D (III)

for r = 0 we get back the non-newtonian ODE with the Kummer M/W solutions but for 2D

An important message: the non-Newtonian contribution gives „more localised” velocity distributions then tha Newtonian

Summary & Outlook• The self-similar Ansatz is presented as a tool

for non-linear PDA

• The non-compressible N-S eq. & compressible N-S eq. & non-Newtonian non-compressible N-S are investigated

• The non-compressible N-S is the „simplest case”

• The other two systems have more „localized” or

even compact support solutions which are important

• Clear out the dark points, include heat conduction

Questions, Remarks, Comments?…