TY JOUR TI Determination of the drag coefficient of trawls by the hydraulic-mathematical method KW trawl KW water resistance force KW friction resistance KW pressure resistance KW resistance coefficient KW Bernulli equation KW body contour inversion KW local resistances KW pres-sure drop KW dynamic pressure KW boundary layer KW calculus of variations KW optimal control KW Dido problem KW Bolts’s Task KW multi-criteria problem KW Galerkin method JO Fisheries AU Gaydenok, N.D. PY 2021 IS 2021 PB FSBI "TSUREN"