Related Experiment Video
Updated: May 26, 2026
10:12
Analyzing Mixing Inhomogeneity in a Microfluidic Device by Microscale Schlieren Technique
Published on: June 12, 2015
Small-scale anisotropy in turbulent shearless mixing
Daniela Tordella1, Michele Iovieno
1Dipartimento di Ingegneria Aeronautica e Spaziale, Politecnico di Torino, 10129 Torino, Italy. daniela.tordella@polito.it
Physical Review Letters
|December 21, 2011
Summary
Turbulent shearless mixing generates small-scale anisotropy, differing significantly from homogeneous turbulence. Velocity derivative moments show opposite skewness signs, indicating unique anisotropic patterns in mixing layers.
Area of Science:
- Fluid dynamics
- Turbulence research
- Computational physics
Background:
- Homogeneous and isotropic turbulence (HIT) serves as a baseline for understanding turbulent flows.
- Turbulent mixing layers exhibit complex dynamics, including anisotropy, which deviate from HIT.
- Understanding anisotropy is crucial for accurate modeling of turbulent phenomena.
Purpose of the Study:
- To numerically investigate the generation of small-scale anisotropy in turbulent shearless mixing.
- To compare the anisotropy in shearless mixing with that in homogeneous and isotropic turbulence.
- To analyze the behavior of velocity derivative moments and skewness in the mixing layer.
Main Methods:
- Direct numerical simulations (DNS) were employed.
- Simulations covered a range of Taylor Reynolds numbers (45–150).
- Analysis focused on longitudinal and transversal velocity derivative moments and skewness.
Main Results:
- Significant departures in longitudinal velocity derivative moments compared to HIT were observed.
- Skewness variation showed opposite signs for components across and parallel to the mixing layer.
- Transversal derivative moments in the mixing layer were found to be very small.
Conclusions:
- Small-scale anisotropy in turbulent shearless mixing differs substantially from HIT.
- The pattern of anisotropy induced by a kinetic energy gradient is distinct from homogeneous shear.
- Small transversal moments do not guarantee isotropy in turbulent mixing layers.
Related Concept Videos
01:28Navier–Stokes Equations
For incompressible Newtonian fluids, where density remains constant, stresses show a linear relationship with the deformation rate, defined by normal and shear stresses. Normal stresses depend on the pressure exerted on the fluid and the rate of deformation in specific directions, which determines how fluid flows under varying pressures. Shear stresses, on the other hand, act tangentially across fluid layers. They explain how adjacent fluid layers slide relative to one another, connecting...
01:22Couette Flow
Couette flow represents the flow of fluid between two parallel plates, with one plate fixed and the other moving with a constant velocity. This configuration allows for a simplified analysis using the Navier-Stokes equations, which govern fluid motion under conditions of viscosity and incompressibility. For Couette flow, the assumptions include a steady, laminar, incompressible flow with a zero-pressure gradient in the flow direction. This flow type is beneficial for understanding shear-driven...
01:24Turbulent Flow
Turbulent flow is characterized by unpredictable fluctuations in velocity and pressure, which result in a chaotic fluid movement distinct from the orderly patterns of laminar flow. While laminar flow is governed by smooth, parallel layers with minimal mixing, turbulent flow exhibits highly irregular, three-dimensional patterns. This behavior arises due to instabilities in the fluid's velocity profile, and amplifies as the flow velocity increases. Minor disturbances, known as turbulent spots,...
01:18Newtonian Fluid: Problem Solving
Newtonian fluids exhibit a constant viscosity, meaning their shear stress and shear strain rate are directly proportional. This property ensures a predictable and stable response to applied forces, maintaining a linear relationship between force and flow. Examples include water, air, and light oils, consistently demonstrating this proportional behavior regardless of external conditions.
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
01:07Laminar and Turbulent Flow
Fluid dynamics is the study of fluids in motion. Velocity vectors are often used to illustrate fluid motion in applications like meteorology. For example, wind—the fluid motion of air in the atmosphere—can be represented by vectors indicating the speed and direction of the wind at any given point on a map. Another method for representing fluid motion is a streamline. A streamline represents the path of a small volume of fluid as it flows. When the flow pattern changes with time, the streamlines...
01:17Steady, Laminar Flow Between Parallel Plates
Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.