Can anyone help me in calculating Kelvin Kei function.

Hi, I am working on estimating deflection using axisymmetric bending of plate due to a point load. I came across a solution, which fits my requirement - but which involves using Kelvin Kei function. I have searched a lot, but could not find a way for matlab to handle Kelvin Kei. Can anyone help me with it? I am trying to evaluate something of the following form:

w = C*kei(r/a), where C and a are constants.

Any help/suggestion will be very much appreciated.

Answer 1

[Roger Stafford]

See the sites:

 http://en.wikipedia.org/wiki/Kelvin_functions
 http://www.mathworks.com/help/matlab/ref/besselk.html

The Kelvin Kei function is simply the imaginary part of matlab's 'besselk' function. Note however that it requires two arguments, an order nu and a possibly complex argument z. Your example shows only one argument.

[sumant]

Hi, Thanks for explanation. I did visit both the links earlier and pardon my ignorance, but what is order nu and complex argument z you talked about? I understand from the explaination on wiki that one needs these two arguments when trying to derive Kei. However, I am not sure how we decide upon them? Like is nu and z arbitrary? I understand its not a matlab question per se, but knowing the answer will help me in creating the code, i am talking about.

[Roger Stafford]

My apologies, Sumant! What I should have said is that the Kelvin kei function which you are presumably attempting to calculate can be evaluated in terms of the imaginary part of matlab's 'besselk' function using the equation

 kei(z) = imag(besselk(0,z*(1+1i)/sqrt(2)));

The order here would be understood to be zero and the argument z is to be multiplied by the square root of the imaginary number i, which is (1+1i)/sqrt(2). In your case z would be r/a.

[sumant]

Great!! This was exactly what I am looking for. :)

Answer 2

[Ahmed]

Hi,

Can someone help me to write the MATLAB code of Bessel functions of zero (J0) and first order (J1) respectively? These Bessel functions (Jo and J1) equations are given in the attached figure.

Cheers, Nisar

[Walter Roberson]

besselj(0,xi), besselj(1,xi)