3D experimental techniques Multi-hot-wire & 3D-PTV Arkady Tsinober, Alex Liberzon School of Mechanical Engineering Tel Aviv University IACAS48

The real motivation of this talk is to expose the experimental abilities The main one is to demonstrate the Israeli Aerospace community the two experimental systems that have not been explored The situation is such that the Turbulence Structure Laboratory has both experimental methods under one umbrella - ready for use “ Know how” (e.g. Marie Curie Chair in Fundamental Aspects of Turbulence)‏ http://www.eng.tau.ac.il/efdl

The main one is to demonstrate the Israeli Aerospace community the two experimental systems that have not been explored

The situation is such that the Turbulence Structure Laboratory has both experimental methods under one umbrella - ready for use

“ Know how” (e.g. Marie Curie Chair in Fundamental Aspects of Turbulence)‏

The field of our study is turbulent flows characteristic of: “ The velocity field is such a complicated function of space and time that a statistical description is easier than a detailed description. It is essentially three-dimensional , in the sense that the dynamical mechanism responsible for it (the stretching of vorticity by velocity gradients) can only take place in three dimensions; It is essentially nonlinear and rotational. A system of partial differential equations exists, relating the instantaneous velocity field to itself at every time and place. ” STEWART, 1963

This quote helps to motivate the experimental research in turbulence “ I soon understood that there was little hope of developing a pure, closed theory, and because of the absence of such a theory the investigation must be based on hypotheses obtained in processing of experimental data ... ” KOLMOGOROV, 1985 ** http://www.eng.tau.ac.il/~tsinober/MarieCurieChair.htm

There are turbulent features that need 3D and time resolved measurements, e.g. vortex breakdown – abrupt, fast and unpredictable (at least in location or time)‏

Lagrangian approach is more “natural” to describe the flow Describes motion of fluid parcels in Newtonian mechanics “ identity conservation law”: X(a,t), a ≡X(0)‏ Mixing, dispersion, diffusion Transfer of scalars, heat and mass Multi-phase flows with “Lagrangian” phase: bubbles, particles, polymers Eulerian vs Lagrangian

Describes motion of fluid parcels in Newtonian mechanics

“ identity conservation law”: X(a,t), a ≡X(0)‏

Mixing, dispersion, diffusion

Transfer of scalars, heat and mass

Multi-phase flows with “Lagrangian” phase: bubbles, particles, polymers

Lagrangian approach is more difficult in some sense The equations are nonlinear and non-integrable for “simple” flows Pathlines (trajectories) are chaotic – difficult to track No unique statistical relationship to “known” Eulerian quantities, e.g. mean, two-point correlation tensor In Eulerian stationary flow Lagrangian can be unsteady, e.g. lack of homogeneity

The equations are nonlinear and non-integrable for “simple” flows

Pathlines (trajectories) are chaotic – difficult to track

No unique statistical relationship to “known” Eulerian quantities, e.g. mean, two-point correlation tensor

In Eulerian stationary flow Lagrangian can be unsteady, e.g. lack of homogeneity

Multi-hot-cold-wire anemometry

Multi-hot-cold-wire anemometry The 5--channel thermometers unit, 20 channel thermometers unit, signal limitation unit, signal conditioning interface, are connected to a 3 mm ‘‘point’’ probe. The central array is shifted forward about 1.5 mm allowing access to all spatial “derivatives”and various (all) components of accelerations in Euler settings.

The 5--channel thermometers unit, 20 channel thermometers unit, signal limitation unit, signal conditioning interface, are connected to a 3 mm ‘‘point’’ probe.

The central array is shifted forward about 1.5 mm allowing access to all spatial “derivatives”and various (all) components of accelerations in Euler settings.

The core is in the calibration ... and people

Recent measurement sessions: in the wind tunnel, Imperial College

Malloja pass, Italy-Switzerland Alps

Does acceleration scale as a local quantity – do we get closer to the solution?

Just to remind you that we use 3D-PTV

Great details from computations Now also achievable by “streaks” 3D-PTV

Intrinsic structure, 3D and small scale (“last but not the least”)‏ Field: Re  ~ 10 4 3D-PTV, Re  ~ 50

Field: Re  ~ 10 4 3D-PTV, Re  ~ 50

Before with DNS, now in the atmospheric boundary layer or in a lab

Lagrangian properties: alignments and correlations

The way to discover that vortex lines are NOT analogy to the material lines

Summary The experimental methods and systems have been presented The general overview of their capabilities are demonstrated Representative results are shown Everybody are welcome to visit the lab and get an impression of the experimental facilities

The experimental methods and systems have been presented

The general overview of their capabilities are demonstrated

Representative results are shown

Everybody are welcome to visit the lab and get an impression of the experimental facilities

Thank you

Lecture series at the Imperial College London, 2007-2008, “Fundamental and Conceptual Introduction to Turbulence” Marie Curie Chair. G. Gulitskii, M. Kholmyansky,W. Kinzlebach, B. Lüthi, A. Tsinober and S. Yorish (2007) Velocity and temperature derivatives in high Reynolds number turbulent flows in the atmospheric surface layer. Part I. Facilities, methods and some general results J. Fluid Mech 589, 57-81. Part II. Accelerarations and related matters, J. Fluid Mech. . 589, 83-102 Part III. Temperature and joint statistics of temperature and velocity derivatives, J. Fluid Mech. . 589, 103-123.

Lecture series at the Imperial College London, 2007-2008, “Fundamental and Conceptual Introduction to Turbulence” Marie Curie Chair.

G. Gulitskii, M. Kholmyansky,W. Kinzlebach, B. Lüthi, A. Tsinober and S. Yorish (2007) Velocity and temperature derivatives in high Reynolds number turbulent flows in the atmospheric surface layer.

Part I. Facilities, methods and some general results J. Fluid Mech 589, 57-81.

Part II. Accelerarations and related matters, J. Fluid Mech. . 589, 83-102

Part III. Temperature and joint statistics of temperature and velocity derivatives, J. Fluid Mech. . 589, 103-123.

One owes to Euler the first general formulas for fluid motion ... presented in the simple and luminous notation of partial differences... By this discovery, all fluid mechanics was reduced to a single point analysis, and if the equations involved were integrable , one could determine completely, in all cases the motion of a fluid moved by any forces... LAGRANGE 1788 Mécanique analitique, Paris, Sec X. p. 271