The drag characteristics of a torpedo are to be studied in a water tunnel using a 1 : 5 scale model. The tunnel operates with fresh water at 20∘C whereas the prototype torpedo is to be used in seawater at 15.6∘C.To correctly simulate the behavior of the prototype moving with a velocity of 30 m/s, what velocity is required in the water tunnel?

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raefx88y · Accepted Answer

Set the equation by applying the principle of dynamic similarity using the Reynolds number:  RE model=RE  Vmodellmodelvmodel=Vlv  From the table 1.6 obtain the viscosity of the sea water at 15.6∘C, and from the table obtain the kinematic viscosity of the water at 20∘C. Transform the equation to isolate model fluid velocity on the left-hand side, and then substitute the values to obtain:  Vmodel=llmodel⋅vmodelv⋅V  =51⋅1.004⋅10−61.17⋅10−6⋅30ms  =128.71ms  Vmodel=128.71ms

The drag characteristics of a torpedo are to be studied in a water tun

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