简答题

已知某内河船船模长4m,湿面积4.6m2,缩尺比α=36,在试验水池中速度为1.8m/s时测得总阻力为3.6kgf,求:实船相应航速、总阻力、有效马力(摩擦阻力按1957ITTC公式;不考虑粗糙度补贴,ν=1.3064*10-6m2/s,ρ=999.63kg/m)

正确答案

傅如德换算关系:Rts=Rfs+(Rtm-Rfm)α3
Vs=α0.5,Vm=6*1.8=10.8m/s
Ss=Sm*α2=4.6*36*36=5961.6
R.e=VL/v
Res=VsLs/v=10.8*100*10-6/1.3064=8.267*108
Rem=VmLm/v=1.8*4*10-6/1.3064=5.511*106
Cfs=0.075/(lgRe-2)2=0.001567
Cfm=0.075/(lgRe-2)2=0.003336
Rfs= Cfs 0.5ρSsVs2=0.0016*0.5*2875*999.63*116.64=268172.7N
Rfm= Cfm 0.5ρSmVm2=0.003336*0.5*4.6*999.63*3.24=24.85N
Rts=Rfs +(Rtm-Rfm)α3=268172.7+(3.6*9.8-24.85)α3=268172.7+162968.8=431141.5N=43994kg
Pe=V*T/75=10.8*35666/75=6335hp。

答案解析