# Maxsurf Motions Encounter Frequency

Discussion in 'Software' started by alidesigner, Jul 7, 2023.

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1. Joined: Nov 2006
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Location: Australia

### alidesignerSenior Member

Hi Guys, I want to check a design at 10 knots into head seas that are 1m high with a period of 16 seconds. Maxsurf motions works in rad/s for encounter frequency and I am lost in the math, it's been a while. I have read the manual but all those integral symbols have done my head in. Is there a simple formula that I can use to I transform the linear encounters into equivalent rad/s? Thanks.

2. Joined: Oct 2008
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Location: Japan

So, a 1m wave of T=16 s (very long shallow wave?!)
This means the wave length, L is = 1.56xT^2 = 399.4m, say 400m

The wave period, w, is then sqrt(2xPixg/L) = sqrt(2x3.1416x9.81/400) = 0.393 rad/s

Vessel speed = 10knots,
So the encounter period is thus:
vessel speed, v =10x0.5148 = 5.15m/s

We = w(1+(v. w/g)) = 0.393(1 + (5.15 x 0.393/9.81)) = 0.474 rad/s

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3. Joined: Nov 2006
Posts: 189
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Location: Australia

### alidesignerSenior Member

Thanks Ad Hoc, that helped a lot, much appreciated.

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