NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Question on currents and waves
From: George Huxtable
Date: 2009 Dec 18, 15:22 -0000
From: George Huxtable
Date: 2009 Dec 18, 15:22 -0000
John Huth wrote "First on the Fisher's Island waves: I've actually paddled in the Race off of Fisher's, it's quite a thrill. In this case, the current itself will create a wind-stress. If you have absolutely still wind, and some current flowing, the current itself will create waves due to the wind stress on the surface. These will be "standing" waves - meaning that if you have a fixed reference in the distance, it will seem like the waves are not moving." I have some doubts about that, though I know nothing about the locality. If the stream is flowing at x knots, and the air is still, than relative to the water surface there is a wind blowing at x knots. And if any waves are not moving with respect to the local land, those waves must also be travelling at x knots relative to the water surface. And yet, when wind at x knots blows across still water, the resulting waves that it generates always travel much slower than x knots. So it seems to me more likely that the standing wave pattern that John observes from his kayak is caused by the water flow, past irregularities on the bottom, creating a stationary "bow wave" which has its effect in ripples at the surface. John continues- "I thought about swells traveling thousands of miles and then encountering a current, and tried to figure this out - I would imagine that the period would be unchanged, but the wavelength would shorten or lengthen, depending on whether it was with or against the current. It might alter the shape, too." Wouldn't it be vice versa, actually; shorter when against the current? But otherwise, I think he has got that exactly right. George. contact George Huxtable, at george@hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. -- NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList+@fer3.com