Related Experiment Video
Updated: May 16, 2026
11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Simulation of granular jets: is granular flow really a perfect fluid?
Tomohiko G Sano1, Hisao Hayakawa
1Yukawa Institute for Theoretical Physics, Kyoto University Kitashirakawa Oiwakecho, Kyoto 606-8502 Japan.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|December 11, 2012
Summary
Simulations show granular jets have finite viscosity, unlike perfect fluids. This suggests the similarity between granular jets and quark-gluon plasma is only superficial.
Area of Science:
- Physics
- Computational Physics
- Granular Dynamics
Background:
- Granular jets exhibit complex fluid-like behavior.
- Previous experiments observed shear stress in granular jets.
- Comparisons have been drawn between granular jets and quark-gluon plasma.
Purpose of the Study:
- To simulate the impact of granular jets in three dimensions.
- To investigate the fluid properties of granular jets post-impact.
- To assess the validity of the analogy between granular jets and quark-gluon plasma.
Main Methods:
- Three-dimensional numerical simulations.
- Modeling of both frictional and frictionless granular materials.
- Analysis of fluid state and viscosity after impact.
Main Results:
- Successfully reproduced the small shear stress observed in experiments.
- The simulated fluid state after impact is not a perfect fluid.
- A finite viscosity was calculated for the granular jet.
Conclusions:
- The similarity between granular jets and quark-gluon plasma is superficial.
- The observed finite viscosity aligns with kinetic theory predictions.
- Granular jets behave as non-perfect fluids with measurable viscosity.
Related Concept Videos
01:14Free Jet
Free jets describe the flow of liquid exiting a reservoir through an opening into the atmosphere without resistance. The velocity (v) of the liquid jet is derived using Bernoulli's principle and expressed as:
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...
01:28Irrotational Flow
Irrotational flow is characterized by fluid motion where particles do not rotate around their axes, resulting in zero vorticity. For a flow to be irrotational, the curl of the velocity field must be zero. This imposes specific conditions on velocity gradients. For instance, to maintain zero rotation about the z-axis, the gradient condition:
01:17Viscosity
When water is poured into a glass, it falls freely and quickly, whereas if honey or maple syrup is poured over a pancake, it flows slowly and sticks to the surface of the container. This difference in the flow of different kinds of liquids arises due to the fluid friction between the liquid layers and the liquid and the surrounding material. This property of fluids is called fluid viscosity. In this example, water has a lower viscosity than honey and maple syrup.
The SI unit of viscosity is...
The SI unit of viscosity is...
01:30Bernoulli's Equation for Flow Along a Streamline
Bernoulli's equation relates the energy conservation in a fluid moving along a streamline. The equation applies to incompressible and inviscid fluids under steady flow. For such a flow, Newton's second law is applied to a small fluid element, which experiences forces due to pressure differences, gravity, and velocity variations. The force balance leads to the following form of Bernoulli's equation:
01:17Accelerating Fluids
When a fluid is in constant acceleration, the pressure and buoyant force equations are modified. Suppose a beaker is placed in an elevator accelerating upward with a constant acceleration, a. In the beaker, assume there is a thin cylinder of height h with an infinitesimal cross-sectional area, ΔS.
The motion of the liquid within this infinitesimal cylinder is considered to obtain the pressure difference. Three vertical forces act on this liquid:
The motion of the liquid within this infinitesimal cylinder is considered to obtain the pressure difference. Three vertical forces act on this liquid: