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Custom density of water - rho(time)

Posted 25 nov 2017, 07:52 GMT-5 Fluid & Heat, Materials Version 3.5a 2 Replies

Federica Guidotti
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Hello everyone,

I'm using Comsol 3.5a. Is it possible to define a time dependent density also at steady-state (chemical engineering module-->momentum transport-->laminar flow-->incompressible Navier-Stokes)? For example, if I define (in expressions--> subdomain expressions):

rho=(1+exp(-t/1[s]))[kg/m^3]

I'll expect that, at steady state (t=+infinity), Comsol'll give me rho=1.

Thank you so much for your time.

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2 Replies Last Post 27 nov 2017, 11:18 GMT-5
Jeff Hiller COMSOL Employee

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Posted: 7 years ago 27 nov 2017, 08:23 GMT-5
Updated: 7 years ago 27 nov 2017, 08:31 GMT-5

Hello Federica,

In a steady-state analysis, t does not take the value + infinity. You could assign t=some large number by defining it as a parameter, but it would just be easier to simply replace your expression that depends on t with the value you want. BTW, rho for water should be close to 1000[kg/m^3]¸ not 1[kg/m^3].

Best,

Jeff

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Jeff Hiller
Hello Federica, In a steady-state analysis, t does not take the value + infinity. You could assign t=some large number by defining it as a parameter, but it would just be easier to simply replace your expression that depends on t with the value you want. BTW, rho for water should be close to 1000[kg/m^3]¸ not 1[kg/m^3]. Best, Jeff
Federica Guidotti
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Posted: 7 years ago 27 nov 2017, 11:18 GMT-5

Thank you so much Jeff.

Thank you so much Jeff.

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