Rectangular pulse as field function

Jul1731 · April 3, 2014, 08:30

Hi guys,

I am trying to create a field function (first time I am doing that on Star) to make a velocity inlet depending of the time.
I want to create a rectangular pulse so I am using a sinusoidal function, and when this function is positive the velocity will be like 80m/s and when it is negative, the velity will be zero.
So here is the field function I have created:

(sin(352*$Time)>=0) ? $$Velocity=80 : (sin(352*$Time)<0) ? $$Velocity=0

Unfortunately, this function doest not compile. I can't find what I have did wrong ... do you have any ideas where I have done a mistake ?

Thank you

RobertB · April 3, 2014, 09:09

Velocity is a vector, you will need something like $$Velocity[1] (Y velocity) or use $VelocityMagnitude if you want a scalar.

Jul1731 · April 4, 2014, 09:32

Thank you for your answer.
My code is now compiling but still not working.
So I tried to set a field funtion very simple as:
$VelocityMagnitude==80
And the velocity keeps to zero ...
Do you have any idea where I am doing wrong ?

Jul1731 · April 4, 2014, 12:54

I have found the solution !!
Thank you for your help !

April 3, 2014, 08:30	Rectangular pulse as field function	#1
Jul1731 New Member Jul Join Date: Feb 2014 Posts: 4 Rep Power: 12	Hi guys, I am trying to create a field function (first time I am doing that on Star) to make a velocity inlet depending of the time. I want to create a rectangular pulse so I am using a sinusoidal function, and when this function is positive the velocity will be like 80m/s and when it is negative, the velity will be zero. So here is the field function I have created: (sin(352$Time)>=0) ? $$Velocity=80 : (sin(352$Time)<0) ? $$Velocity=0 Unfortunately, this function doest not compile. I can't find what I have did wrong ... do you have any ideas where I have done a mistake ? Thank you

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April 3, 2014, 09:09		#2
RobertB Senior Member Robert Join Date: Jun 2010 Posts: 117 Rep Power: 17	Velocity is a vector, you will need something like $$Velocity[1] (Y velocity) or use $VelocityMagnitude if you want a scalar.

April 4, 2014, 09:32		#3
Jul1731 New Member Jul Join Date: Feb 2014 Posts: 4 Rep Power: 12	Thank you for your answer. My code is now compiling but still not working. So I tried to set a field funtion very simple as: $VelocityMagnitude==80 And the velocity keeps to zero ... Do you have any idea where I am doing wrong ?

April 4, 2014, 12:54		#4
Jul1731 New Member Jul Join Date: Feb 2014 Posts: 4 Rep Power: 12	I have found the solution !! Thank you for your help !