01327nas a2200145   4500008004100000245008100041210006900122260000800191300001100199490000700210520081400217100002101031700002101052856010801073       2007                        eng d00aVelocity correlations in dense granular flows observed with internal imaging0 aVelocity correlations in dense granular flows observed with inte  cJUN  a2380010 v983 a<p>We show that the velocity correlations in uniform dense granular flows inside a silo are similar to the hydrodynamic response of an elastic hard-sphere liquid. The measurements are made using a fluorescent refractive-index-matched interstitial fluid in a regime where the flow is dominated by grains in enduring contact and fluctuations scale with the distance traveled, independent of flow rate. The velocity autocorrelation function of the grains in the bulk shows a negative correlation at short time and slow oscillatory decay to zero similar to simple liquids. Weak spatial velocity correlations are observed over several grain diameters. The mean square displacements show an inflection point indicative of caging dynamics. The observed correlations are qualitatively different at the boundaries.</p>1 aOrpe, Ashish, V.1 aKudrolli, Arshad  uhttps://library.ncl.res.in/content/velocity-correlations-dense-granular-flows-observed-internal-imaging