HIGH-REYNOLDS-NUMBER ASYMPTOTICS OF THE STEADY FLOW-THROUGH A ROW OF BLUFF-BODIES

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Experimentální stanovení Magnusova koeficientu rotačně se pohybující kulové částice

The Magnus force coefficient was determined from comparison of theoretical and experimental trajectory of rotating spherical particle falling in calm water. Theoretical trajectories of the particle were calculated using 2D numerical model of the rotating spherical particle moving in fluid and the proper value of the Magnus force coefficient was established from condition of the best fitting of the experimental trajectory by the calculated one. The mutual influence of the translational and rotational movements was described

Numerický 3D model kolize pevné částice s drsným dnem kanálu

The paper deals with 3D numerical model of the random process of rotating spherical particle-bed impact and rebound for saltation movement of a particle in channels with rough bed. The collision height and the contact point are defined as random variables of the collision process. The collision height depends on bed roughness. The contact point position depends on the irection of the particle velocity vector before the collisio

Influence of the spheroid prolongation on the drag force

The drag force acting on a spheroid moving perpendicularly to its axis of rotation in water was studied experimentally. Along the spheroid axis, which is normal to its axis of rotation, a round narrow hole was bored. The spheroid moved along a thin vertical thread stretched in water. A video system recorded the spheroid motion and the spheroid velocity was determined from the record. The drag force coefficient was calculated from the balance of forces acting on the spheroid. Two oblate, two prolate spheroids and one sphere with ratio of the axes 0.67; 0.81; 1.33; 2 and I (sphere), respectively, with approximately the same volumes, were used. The friction coefficient between the thread and spheroid was determined from the comparison of the experimental and calculated motions of the sphere, for which the drag force coefficient is known. The dependence of the drag force coefficient of the spheroid on the ratio of its semi-axes was obtained

Magnusův odporový koeficient kulové částice pohybující se v kapalině

The Magnus force coefficient was determined from comparison of theoretical and experimental trajectory of rotating spherical particle moving in calm water. Theoretical trajectories of the particle were calculated using the 2D numerical model of the rotating spherical particle moving in liquid and the proper value of the Magnus force coefficient was established from condition of the best fitting of the experimental trajectory by the calculated one

3D mathematical model of spherical particle saltatory movement in open channel with rough bed

One of the main modes of bed load transport is saltation when particles hop up from the bed and follow ballistic-like trajectories. Mathematical models of saltation are mostly two-dimensional although the particle motion is actually three-dimensional. The aim of the present study is development of the 3D mathematical model of solid particle saltatory motion over rouhg bed in an open channel

Experimental investigation of drag force, Magnus force and drag torque acting on rough sphere moving in calm water

The paper describes the results of experiments with a rotating golf ball moving quasi-steadily in calm water. The motion of the ball was recorded on a digital video camera. The dimensionless drag force, Magnus force, and drag torque coefficients were determined from the comparison of the calculated translational and angular velocities and trajectory with experimental ones for the rough particle. The proper value of the correction coefficients were established from condition of the best fitting of the experimental trajectory by the calculated one

Experimentální výzkum odporu rotačně se pohybující kulové částice

Saltatory solid particles conveyed by fluid impact a channel bed from time to time. As a result of the collision the particles receive angular velocity, which gradually decreases with time. For numerical simulation of saltation it is necessary to know values of the drag rotation coefficient. In this paper experimental results of the rotating spherical particles moving in water are described. The rubber spherical balls with density near that of water were used; each of them was speeded up in a special chute that ensured that the particle rotated in a given plane. Values of the drag coefficient of the rotating spherical particle were determined in a dependence on rotation particle Reynolds numbe

Numerický model saltace kulovité částice v kanále s příčně skloněným drsným dnem

The paper deals with 3D numerical model of the spherical particle saltation in the rectangular channel with rough bed and the effect of lateral slope of the bed. The stochastic method based on the concept of contact zone is used for the calculation of particle-bed collision. Some examples of calculation are presented, in particular, the effect of transverse tilted bed on the particles sorting. The beams of the trajectories of particles starting saltation from one point are calculated. The centrelines of the beams can be approximated by straight lines for low and moderate values of the bed transverse slope and the angles between centrelines and the stream direction depend on the lateral slope of the bed