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    Re: Question on currents and waves
    From: John Huth
    Date: 2009 Dec 18, 10:42 -0500

    George - 

    Sorry, I got it backwards on the "with" and "against".   Also - yes, the effect of drag against the bottom will create standing waves as well - I was just exploring one aspect of the wind/wave interactions.   

    (there's also a huge eddy behind the Race - induced by Fisher's Point).

    John H. 

    On Fri, Dec 18, 2009 at 10:22 AM, George Huxtable <george{at}hux.me.uk> wrote:
    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{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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