Author(s): Wojciech Majewski

Linked Author(s): Wojciech Majewski

Keywords: No Keywords

Abstract: Appearance of ice cover on rivers and channels changes considerably flow condi­tions from free surface flow to quasi pressure flow induced by floating ice cover. Good knowledge of the conditions with continuous ice cover over the whole width of the channel has been obtained mainly due to field measurements of velocity distribution and character of ice cover. Very little information is on flow characteristics for the flow with partial ice cover. Such situations appear during the formation of border ice in the beginning of winter or when icebreakers form "ice free" channel for navigation or ice-run. Measurements of velocity distribution in these cross-sections are very difficult and even dangerous. Hydraulic calculations of the flow with compound ice cover are based on the conveyance principle applied to consecutive river cross-sections. Results of these calculations are very difficult to verify because of the lack of necessary data. In order to fill this gap laboratory experiments were carried out in a horizontal hydraulic flume 20 m long and 2 m wide. Floating ice cover was simulated by means of special impregnated plates of density similar to the density of ice. Experiments were carried out for steady flow conditions of the depth 0.20 III and constant discharge for free sur­face and partly covered flow. Plates simulating ice cover were floating on both sides of the channel. Bottom roughness as well as roughness of the underside of the simulated ice cover were changed in consecutive experiments. Velocity distribution in the whole cross-section was measured by means of miniature propeller current meter. These data allowed to determine discharge in various parts of the cross-section, resistance coeffi­cients, and energy coefficients a. Values of flow characteristics based on experimental data were compared with calculated ones.

DOI:

Year: 1992