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The Results of the Study on Water Resistance to the Motion of Timber Transport Units

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Ya.V. Vatlina, G.Ya. Surov

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A raft section consisting of four small volume bundles (up to 5 m3) linked by means of fastening logs and flexible couplings has been proposed for shallow rivers. Experimental investigations of the motion of timber transport units (TTU) in shallow waters were conducted.  TTUs were formed of 1­–6 raft sections. The study was performed using models on a scale of 1:20. The length–beam ratio of the TTU ranged between 1 and 6. At uniform motion of the TTU, modelling was carried out using Froude number ranging between 0.16 and 0.48. At unsteady motion, the experiments were performed using Froude number and homochronicity criterion. The research was conducted at Reynolds numbers ranging between 3.1?104 and 5.5?105. The models were towed at the speeds from 0.1 to 0.3 m/sec. A non-contact rotational velocity sensor was used to register the motion of the models. The sensor formed impulses at a frequency proportional to the frequency of passing the tachometric marks on the light-reflecting rotating block. Variation of impulse frequency was recorded by means of Zet Panel computer program.  Quadratic dependences of the water resistance force to the uniform TTU motion on the model velocity were derived for each model. Water resistance to TTU’s unsteady motion is represented as water resistance to uniform motion plus additional resistance arising at unsteady motion. The values taken into account as nonstationarity factors were: associated mass, water mass in the voids of TTUs, and additional water resistance. For all TTU models we derived dependences of the nonstationarity factor on the relative motion speed at the following depth–draught ratios: 7.0; 5.0; 4.0; 2.7 and 1.6. The results obtained allow one to determine TTU’s acceleration time and distance. Some additional tasks can be solved, such as determining the acceleration force required to reach a given TTU motion speed in a certain time.


Ya.V. Vatlina, Postgraduate Student, G.Ya. Surov, Candidate of Engineering, Professor

Northern (Arctic) Federal University named after M.V. Lomonosov
Naberezhnaya Severnoy Dviny, 17, 163002 Arkhangelsk, Russia


Northern (Arctic) Federal University named after M.V. Lomonosov


raft section, experimental study, unsteady motion, water resistance, nonstationarity factor, velocity, mass.


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The Results of the Study on Water Resistance to the Motion of Timber Transport Units


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