G. Surov, Y. Shadrina, O. Murashova
Wednesday 19 December 2018 by Libadmin2018


Raft-assembling unit composed of four small volume bundles (up to 5 cubic meters) linked by the means of the fastening logs and flexible couplings has been proposed for the shallow rivers. As the results of experimental researches the mathematical model of hydrodynamics resistance was obtained. The timber transport units (TTU) were formed from 1…6 raft sections. The study was performed at 1:20 model-prototype relationship. The “length/beam” ratio of the TTU varied from 1 to 6. Modeling during uniform motion of the TTU was carried out by Froude number varied from 0.16 to 0.46. The experiments in unsteady motion conditions were performed by Froude factors and homochronicity condition. The studies were carried out within the Reynolds number range of 3.1·104 … 5.5·105 . The models were towed at speeds of 0.1…0.3 m/sec. Quadratic dependences of the water resistance force to the velocity of the uniform motion of the TTU models have been derived. The water resistance in the case of the TTU non-stationary motion is represented as the latter for the uniform motion plus additional resistance arising during non-stationary motion. The values taken into account as the aggregated nonstationarity coefficient were: associated mass, water mass in the TTU hollow space and additional water resistance. Dependences of the nonstationarity coefficient to the relative motion speed for all TTU models at the depth / draft ratios of 7.0; 5.0; 4.0; 2.7; 1.6 have been derived. The results obtained by the researchers allow to determine the duration and distance of a TTU acceleration. Some additional tasks become solvable. For instance, necessary acceleration force for attainment of a TTU predetermined motion speed can be found.

Keywords: research on models, rafting unit, experimental study, unsteady motion, water tractive resistance, nonstationarity factor/

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