We derive an exact equation governing two-particle backwards mean-squared dispersion for both deterministic and stochastic tracer particles in turbulent flows. For the deterministic trajectories, we probe the consequences of our formula for short times and arrive at approximate expressions for the mean-squared dispersion which involve second order structure functions of the velocity and acceler...

Individual random trajectories of stochastic processes are often analyzed by using quadratic forms such as time averaged (TA) mean square displacement (MSD) or velocity auto-correlation function (VACF). The appropriate quadratic form is expected to have a narrow probability distribution in order to reduce statistical uncertainty of a single measurement. We consider the problem of finding the op...

Calculation of the velocity of body displacement and of the momentum of the body from 100 normal ballistic tracings shows that the values of the velocity of body displacement present a small scatter (mean value 68.3 + 13.9 mm. per second) and are independent of body weight and surface area. For uniformity of values and simplicity of calculation, which can be effected also on many abnormal traci...

Microphone turbulence screens are used to suppress turbulent pressure fluctuations when measuring the acoustic pressure inside a duct with flow. They consist of a long tube with a slit covered with porous material, and thus are also called sampling tubes. Because they are not omnidirectional, it is necessary to calculate corrections when higher order modes are propagating in the duct. In order ...

Abstract We investigate the sedimentation of identical inertialess spherical particles in a Stokes fluid limit many small particles. It is known that presence leads to an increase effective viscosity suspension. By Einstein's formula this effect order particle volume fraction ?. The disturbance flow responsible for very singular (like | x ? 2 ). Nevertheless, well-prepared initial configuration...

Fluid velocity has the potential to cause severe erosion damage to oil & gas production infrastructure. In order to avoid or alleviate damage due to erosion, the American Petroleum Institute Recommended Practice (API RP) 14E recommends a threshold fluid velocity for production tubing and pipelines. However, field and laboratory data have proven that the applied empirical constants, known as C-f...

Particle concentration is a key unit operation in biochemical assays. Although there are many techniques for particle concentration in continuous-phase microfluidics, relatively few are available in multiphase (plug-based) microfluidics. Existing approaches generally require external electric or magnetic fields together with charged or magnetized particles. This paper reports a passive techniqu...

1. The reconstruction of the 3D-velocities of the clusters of galaxies and their large-scale motions remains one of the central problems of observational cosmology (see [2,7] and references therein). The reason is clear: these properties should contain crucial information on the mechanisms of formation of the filaments and even on more early phases of evolution of the Universe, as well as on th...