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Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing ...

Wesleyan University

The purpose of this study was to determine career preferences of medical students at the time of entering medical school compared with interns who were graduating; and to determine what factors influence the choice of a special discipline as a career.

Freshmen versus interns' specialty interests.

The rotational dynamics of anisotropic particles advected in a turbulent fluid flow are important in many industrial and natural settings. Particle rotations are controlled by small scale properties of turbulence that are nearly universal, and so provide a rich system where experiments can be directly compared with theory and simulations. Here we report the first three-dimensional experimental measurements of the orientation dynamics of rodlike particles as they are advected in a turbulent fluid flow. We also present numerical simulations that show good agreement with the experiments and allow extension to a wide range of particle shapes. Anisotropic tracer particles preferentially sample the flow since their orientations become correlated with the velocity gradient tensor. The rotation rate is heavily influenced by this preferential alignment, and the alignment depends strongly on particle shape.

Rotation rate of rods in turbulent fluid flow.

We derive a scaling relationship for the mean square rotation rate of rods with lengths in the inertial range in turbulence: <p(i)p(i)> ∝ l(-4/3). We present experimental measurements of the rotational statistics of neutrally buoyant rods with lengths 2.8<l/η<72.9, and find that the measurements approach the predicted scaling. The approach to inertial range scaling is shown to be more complex than anticipated with an overshoot and approach to the scaling from above. For all rod lengths, the correlation time of the Lagrangian autocorrelation of the rotation rate scales as the turnover time of the eddies of the size of the rod. Measuring rotational dynamics of single long rods provides a new way to access the spatial structure of the flow at different length scales.

Inertial range scaling in rotations of long rods in turbulence.

We present a simple, noninvasive method for simultaneous measurement of flow velocity and inference of liquid viscosity in a microfluidic channel. We track the dynamics of a sharp front of photobleached fluorescent dye using a confocal microscope and measure the intensity at a single point downstream of the initial front position. We fit an exact solution of the advection diffusion equation to the fluorescence intensity recovery curve to determine the average flow velocity and the diffusion coefficient of the tracer dye. The dye diffusivity is correlated to solute concentration to infer rheological properties of the liquid. This technique provides a simple method for simultaneous elucidation of flow velocity and liquid viscosity in microchannels.

Shima Parsa

Department of Physics

Wesleyan University

Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

Shima Parsa

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Physics

Wesleyan University

Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

Department of Physics