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

Complete text of the article:

Download article (pdf, 0.4MB )

UDС

634.0.378.34

DOI:

Abstract

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.

Authors

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

Affiliation

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

Keywords

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

References

1. Barabanov V.A. Issledovanie razvorota lesotransportnoy edinitsy pri neustanovivshemsya rezhime dvizheniya [Study of U-Turn of the Timber Transport Unit at Transient Driving Conditions]. Khimiko-lesnoy kompleks: problemy i resheniya: materialy Vseros. konf. Forest-Chemical Complex: Problems and Solutions: Proc. All-Russian Conf. Krasnoyarsk, 2002, pp. 71–76. 2. Mitrofanov A.A. Lesosplav. Novye tekhnologii, nauchnoe i tekhnicheskoe obespechenie [Rafting. New Technologies, Scientific and Technical Support]. Arkhangelsk, 2007. 492 p. 3. Ovchinnikov M.M., Rodionov P.M. Soprotivlenie dvizheniyu khlystovykh plotov [Resistance to Motion of Tree-Length Rafts]. Lesnaya promyshlennost', 1979, no. 6, pp. 28–29. 4. Surov G.Ya., Vatlina Ya.V., Sharova T.M. Splotochnaya edinitsa [Raft Section]. Patent RF no. 115769 5. Surov G.Ya. O vliyanii massy vody v pustotakh puchka breven na velichinu sily udara [Influence of the Mass of Water in Voids of the Log Truss on the Impact Force Value]. Vodnyy transport lesa: mezhvuz. sb. nauch. tr. [Timber Transportation by Water: Interuniversity Collection of Sci. Papers]. Iss. 5. Krasnoyarsk, 1977, pp. 15–21.