This paper introduces an innovated plate anchor, increasing its bearing section area during uplift. In this experimental study, the influences of embedment depth of plate anchor and soil surface condition (restricted or free) on sand deformation field during uplift test are investigated. In order to study the soil deformation around the anchor, Particle Image Velocimetry (PIV) is used. The experimental setup consists of a camera, a new designed box, load cell, encoder and computer. During the uplift test on physical models, images are captured and used by PIV to depict the soil displacement field. Based on this study, it is found that pullout capacity and sand deformation zone are significantly influenced by anchor embedment depth. In shallow anchors, sand deformation zone lines are similar to a curve and cross the soil surface; however, in deep anchors, sand deformation zone is a bulb-shaped zone that extends from anchor to a distance of approximately two times its diameter above. Soil surface restriction increases anchor pullout capacity in shallow anchors up to 37 %, but in deep ones, there is no significant difference. Soil surface restriction changes shallow anchor behavior to deep anchors; however, it has no notable influence on deep anchors.
The cavitations in turbo-machines decrease their efficiency and have a bad impact of their work-life and therefore constructors are always trying to avoid or minimize the cavitation risks in hydraulic machines. In this paper we have done the LDV measurement of flow in the model pump suction sump with baffle. In precedent works we did the PIV (Particles Image Velocimetry) measurement with and without baffle. Around the pump bell there are very complex vortices, which can affect seriously the flow characteristics of the pump. They can also cause vibrations, cavitations and decrease the efficiency of the system. In this experiment the pump suction sump and the pump bell with particular structure are used to search the flow situation in the surrounding of the bell. Both LDV and PIV experiments were done with steady flow using appropriate materials. and Kavitace v turbogenerátorech a čerpacích systémech snižuje jejich účinnost a negativně ovlivňuje jejich životnost. Snahou konstruktérů je proto vyloučit nebo minimalizovat riziko kavitace v hydraulických strojích. V článku jsou prezentována měření rychlostních polí pomocí LDV v modelové sací jímce s tokovým usměrňovačem a výsledky jsou porovnány s dřívějšími měřeními pomocí PIV. V blízkosti sacího zvonu vznikají komplikované vírové struktury, které mohou následně ovlivňovat charakteristiku čerpadla a které mohou být příčinou vzniku vibrací, kavitace a snížení účinnosti. Pozornost proto byla zaměřena na měření rychlostních polí v okolí sacího zvonu.
A three-dimensional numerical simulation of particle motion in a pipe with a rough bed is presented. The simulation based on the Lattice Boltzmann Method (LBM) employs the hybrid diffuse bounce-back approach to model moving boundaries. The bed of the pipe is formed by stationary spherical particles of the same size as the moving particles. Particle movements are induced by gravitational and hydrodynamic forces. To evaluate the hydrodynamic forces, the Momentum Exchange Algorithm is used. The LBM unified computational frame makes it possible to simulate both the particle motion and the fluid flow and to study mutual interactions of the carrier liquid flow and particles and the particle–bed and particle–particle collisions. The trajectories of simulated and experimental particles are compared. The
Particle Tracking method is used to track particle motion. The correctness of the applied approach is assessed.
Pressure-swirl atomizers are widely used in various combustion applications including aircraft jet engines. Spray characteristics, such as drop-size and velocity distribution have a principal influence on the combustion process. A number of studies have dealt with single-point laser diagnostic techniques, such as Phase-Doppler Anemometry, for spray measurements. An alternative approach is the use of a whole-field method - Particle Image Velocimetry (PIV). This contribution deals with investigation of spray characteristics of a spill-return pressure-swirl atomizer for a small-sized jet engine by means of PIV. The nozzle was operated on a cold test bench at atmospheric pressure and room temperature. Measurements were carried out in an axial section of the spray cone with various single-camera and stereoscopic PIV configurations. Results of out measurements provide a quantitative visualization of the spray flow fields in regimes based on the engine operating conditions. Comparison of velocity profiles obtained from the individual PIV configurations is presented and discussed. The pressure-swirl spray is recognised as an optically harsh environment for PIV due to large particle size range, high diameter-velocity correlations, strong velocity gradients and large velocity differences within an image, large variations in ‘seeding‘ concentration and out-of-plane particle movement. The PIV results comprise new findings to the complex 3D character of velocity field in the pressure-swirl sprays. and Obsahuje seznam literatury
Turbulence of flow over mobile bedforms in natural open channels is not yet clearly understood. An attempt is made in this paper to determine the effect of naturally formed mobile bedforms on velocities, turbulent intensities and turbulent stresses. Instantaneous velocities are measured using a two-dimensional particle image velocimetry (PIV) to evaluate the turbulence structure of free surface flow over a fixed (immobile) bed, a weakly mobile bed and a temporally varying mobile bed with different stages of bedform development. This paper documents the vertical distribution of velocity, turbulence intensities, Reynolds shear stress and higher-order moments including skewness and turbulent diffusion factors. Analysis of the velocity distributions shows a substantial decrease of velocity near the bed with increasing bedform mobility due to increased friction. A modified logarithmic law with a reduced von Kármán constant and increased velocity shift is proposed for the case of the mobile bedforms. A significant increase in the Reynolds shear stress is observed in the mobile bedforms experiments accompanied by changes over the entire flow depth compared to an immobile bed. The skewness factor distribution was found to be different in the case of the flow over the mobile bedforms. All higher-order turbulence descriptors are found to be significantly affected by the formation of temporally varying and non-equilibrium mobile bedforms. Quadrant analysis indicates that sweep and outward events are found to be dominant in strongly mobile bedforms and govern the bedform mobility.