Line element with linear viscous model Answered

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Robin James

Respected Sir/Madam,

I found that to define line element with a non-linear viscous model I need to use the command:

line

 prop visc mass c1 c2 vmax delt

 

and it follows the equation F = c1*x^(-c2).

If I input C2 = 1, will this change to a linear viscous model?

Also, what are the units of c1 and c2? Are these quantities per unit area or per unit length of the line element or do they have units of damping such as Ns?

2 comments

  • Official comment
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    Chloe Allison
    (Edited )

    Hi Robin,

    The command reference for the viscous line element does not render the equation properly (we will fix this). It should be:

    F = c1 * x_dot^c2 , where x_dot is x with a dot on top. 

    This is the relative velocity of the two endpoints of the line element and there is no negative sign.

    So we could say:
    F = c1 * v^c2

    c1 is the usual viscous coefficient in SI units of N.s/m

    c2 is unitless and yes, a value of 1.0 will give a linear model F = c1 * x_dot


    There is no area defined for this element.

     

    I hope this helps. 

     

    Best Regards,

    Chloe

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  • Avatar
    Robin James

    Great,
    Thanks Chloe.
    This clarifies my doubt.

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