本邦近海に於ける暴風の型式と海洋波の性質に就て

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Characters of the ocean wind about Japan, whichis limited to the region from 120°E to 150°E and 20°N to 50°N, is that the prevailing wind which blows more than four days with constant direction and constant velocity occurs rarely, so there can hardly be seen fully grown-up swell.The foundamental equation of Sverdrup^Munk's theory can be expressed as d/(dt)(δ^2β^5u^5)=0.2237[1±2.5(1-β)^2]δ^2β^2u^4. (1)I_n the centre of storm dβ/dt=0,so that, (du)/(dt)|_<u=u_m>=0.0447(1+2.5(1-β_m)^2)/(β^3_m), (2)where the most frequently observed value ot the gradient of the wind velocity is about 2m/s・hour, then β_m≒0.4,(3)so that δ_m≒0.1 (4)When the variations of wind velocity occur frequently, the wave-arising force of wind acting on waves which is represented in the right hand side of equation (1) becomes weak.Under this condition, above equation can be integrated imediately, ((δ/(δ_m))^2((βu)/(β_mu_m))^5=1,. (5)Because 0.3≦β_m≦0.4,0.09≦δ_m≦0.10,we obtain βu≒β_mu_m, which show that the wave period is unchanged in the region of storm. Then the wave length and wave period is : L≡⃥(2π)/g(β_mu_m)^2≒0.1.u_m^2,(6)T≒(2π)/gβ_mu_m≒0.26u_m; (7)and wave height is H≒u/(u_m)H_m, H_m≒(2π)/g(β_mu_m)^2δ_m≒(1/(10)u_m)^2 (8)where the unit is L and H in metre, T in second and u in metre per second respectively.These analytical results show good accordance with the records of weather ships at X-ray and Tnago.
社団法人日本船舶海洋工学会の論文

本邦近海に於ける暴風の型式と海洋波の性質に就て

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