Polymer Stretching by Turbulence + Elastic Turbulence Theory

1. La Jolla, 07/07/00 Polymer Stretching by Turbulence + Elastic Turbulence Theory Misha Chertkov Los Alamos Nat. Lab. • Polymer Stretching by Turbulence (Statistics of a Passive Polymer) • Pure (Re<<1, Wi>>1) Elastic Turbulence of dilute polymer solution • Inertia-Elastic Turbulence (Re>>1,Wi>>1). Drag reduction. Thanks A. Groisman, V. Steinberg, E. Balkovsky, L. Burakovsky, G. Falkovich, G. Doolen, D. Preston, S. Tretiak, B. Shraiman http:/cnls.lanl.gov/~chertkov/elturb.ps /polyprl.ps

2. Polymer Stretching by Turbulence MC, PRL 05/00 Balance of forces ABC Models of Elasticity linear (Hook) dumb-bell nonlinear chain nonlinear dumb-bell smallest scale of the flow stretched polymer length equilibrium polymer length Scale Separation >> >> The question: to describe statistics of passive polymer ? Advection >> Diffusion Batchelor ‘59 Kraichnan ‘68 Shraiman, Siggia ‘94,’95 MC,Falkovich,Kolokolov,Lebedev ‘95 MC,Gamba,Kolokolov ‘94 Balkovsky,MC,Kolokolov,Lebedev ‘95 Bernard,Gawedzki,Kupianen’98 MC, Falkovich, Kolokolov ‘98 Balkovsky,Fouxon ‘99 Statistics of passive scalar advected by the large scale “Batchelor” velocity is understood statistics of is given Passive =

3. Passivelinear polymerA CLT for the Lyapunov exponent statistics at (saddle point parameter) First order transition: the polymer stretches indefinitly ifadvection exceeds diffusion PDF Lumley ‘72 Balkovsky,Fouxon,Lebedev’99 PDF Nonlinearity beats the stretching !! diss. scale

4. Passivenonlinear polymerB MC ‘99 saddle point parameter PDF PDF Passive nonlinear chain C • linear conformations are dominant • N (number of segments) >>1 is an • additional saddle parameter Notice the nonlinear dependance coming from the “equilibration” of the stretching by the nonlinearity

5. Non-Newtonian hydrodynamics of a dilute polymer solution Navier-Stokes equation Scale separation Hydrod. Inter-polymerStretched Equilibrium scalesdistance polymer length polymer length >> >> >> n- is the polymer solution concentration N>>1- is the dimensionless polymer length Elastic part of the stress tensor in the kinetic theory approximation Regime of a weak elasticity (linear stretching) =>OldroydB model Regime of a strong elasticity (nonlinear stretching)=> local relation between and : Weissenberg number the maximal tension the largest eigenvalue of constitutive equation the direction of the eigenvector nondeg. deg.

6. Pure Elastic Turbulence (experiment) Groisman, Steinberg ‘96-’99 d=20mm Swirling flow between two parallel disks transition to turbulence d=10mm pure solvent 80ppm polyacrylamide+ 65% sugar+1% NaCl in water Power spectra of velocity fluctuations Wi=13 Re=0.7

7. Pure Elastic Turbulence (theory) Elastic dissipation >> Viscous dissipation, Advection Nonlinear diffusion + constitutive equation poor-man scaling K- is the pumping amplitude of

8. Inertia-elastic Turbulence (instead of conclusions) Energy containing scale Viscous (Kolmogorov) scale • Dissipation due to elasticity at the Kolmogorov scale • is less then the viscous dissipation • The drag reduction (dissipation dominated by • the elasticity onset) • The energy is dissipated at the elastic scale • Polymers start to overlap each other • (the kinetic approximation fails) Increase of n - polymer density According to Lumley’69 the increase in bulk dissipation (viscosity) is accompanied by a swelling of a boundary layer, that leads to the drag reduction