define 'if' and 'else' statemets in [soln-ics] section

[AC]

Hi guys,

I am trying to define some velocity profiles in [soln-ics]  using the expressions below. I think that it doesn't pass the 'if' and 'else' statements to the solver. 

Do you have some suggestions please? Any help would be much appreciated. 

Cheers, Andrei 

if y<1.:

        yplus = y * u_tau / nu_inf

else:

       yplus = ((2-y)) * u_tau / nu_inf

[Freddie Witherden]

Hi Andrei,

On 13/08/2018 16:47, AC wrote:
> I am trying to define some velocity profiles in [soln-ics]  using the
> expressions below. I think that it doesn't pass the 'if' and 'else'
> statements to the solver.
> Do you have some suggestions please? Any help would be much appreciated.

You can accomplish this by using an expression with a hyperbolic tangent
(tanh) function. This provides a smooth means of transitioning between
one function and another.

Regards, Freddie.

[Kiny Wan]

Hi Freddie,

         The hyperbolic tangent (tanh) function is difficult to initiate a shock wave. The following is a matlab code and its related picture:

        r=-5:0.0001:5;

        aaa=1.34161*tanh(500000000*(1-tanh(500000000*(r))))+(1-0.2*1.0*1.0*exp(1-(r-4).*(r-4))).^2.5.*tanh(500000000*(1+tanh(500000000*(r)))/2);

        plot(r,aaa)

        A peak value is generated near x=0.

Yours 

Wan

[Tarik Dzanic]

Hi Wan,

Try this:

aaa = 1.34161*(0.5*(tanh(500000000*(1-r)) +1))   +   (1-0.2*1.0*1.0*exp(1-(r-4).*(r-4))).^2.5.*(1 - 0.5*(tanh(500000000*(1-r)) + 1));

[Kiny Wan]

Hi Dzanic

        Thank you. It works.