## Fluids

#### Functional Expressions

• Viktor Polášek
Subscriber

Hi gents,
I'm dealing with water flow in the pipe and air flow around the pipe at the same time. Whether water or air is flowing is controlled by the following condition. If temperature of monitored point (tp) at tube is below 263K, the water is flowing. If temperature of tp is above 333K water is switched off and air starts flowing. Air flows until temperature of tp is below 263K. See behavior of flowing in graph below.I'm trying solve it through expressions at water/air velocity inlet.

Water:

IF(OR(AND(tp>=263.15[K],vc=0[m/s])(AND(tp<=333.15[K],vc=0.25[m/s]))), 0.25 [m/s], 0 [m/s])

Air:

IF(OR(AND(tp>=333.15[K],vair=0[m/s])(AND(tp>=263.15[K],vair=4[m/s]))), 4 [m/s], 0 [m/s])

where

tp - monitored temperature of point at tube wall

vc - monitored water velocity at inlet

vair - monitored air velocity at inlet

Unfortunatelly, it doesnt work. Any idea how to solve? Thanks in advance.

Greetings amd smooth convergence.

Viktor

• Rob
Ansys Employee

Please can you expand on "doesn't work"? Ie is there an error, or the boundary isn't what you expect?

• Viktor Polášek
Subscriber

Hi Rob,