( 3 ) using conformal mapping , the longitudinal protrusion height and the lateral protrusion height on the v - grooved surfaces are given , on this basis , some drag reducing features in parallel - flow , cross - flow and enlarge - flow are presented and analyzed ; in addition , drag reducing features with blade - shaped grooves and u - shaped grooves are discussed , consequently , the riblets designing criterions are suggested which will reduce the drag and noise most effectively underwater ( 3 )利用保角變換方法求出v ?型條紋的縱向和橫向突出高度,在此基礎(chǔ)上得出縱向流、橫向流和帶角度流動(dòng)時(shí)的降阻特性,并分析結(jié)果;而且分析了葉片型條紋和u ?型條紋表面上的降阻情況,提出水下具有最佳降阻效果的條紋表面設(shè)計(jì)準(zhǔn)則。