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Non-newtonian Flow
Posted 6 août 2015, 08:51 UTC−4 Fluid & Heat Version 5.1 3 Replies
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I am simulating a chute flow. My geometry is a rectangular box. There is an inlet and outlet and other walls are fixed. In inlet I am giving velocity inlet conditions and at the outlet I am giving pressure outflow conditions and the value for Po is 0.1.
The fluid is non-newtonian type. In this mu(viscosity) is a function of shear rate and pressure and also it depends on square root of pressure term.
When i try to simulate it gives an error saying it cannot calculate the non-integral power of a negative number. So, it must be because of the square root of pressure we were talking about.
I want to know why the pressure is getting negative
or is there any way to give the command like,
mu= max(2, expression)
where expression is that function of shear rate and pressure
OR
will it get the same result as it cannot calculate the square root of a negative number.
The fluid is non-newtonian type. In this mu(viscosity) is a function of shear rate and pressure and also it depends on square root of pressure term.
When i try to simulate it gives an error saying it cannot calculate the non-integral power of a negative number. So, it must be because of the square root of pressure we were talking about.
I want to know why the pressure is getting negative
or is there any way to give the command like,
mu= max(2, expression)
where expression is that function of shear rate and pressure
OR
will it get the same result as it cannot calculate the square root of a negative number.
3 Replies Last Post 2 sept. 2015, 06:17 UTC−4
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Posted:
9 years ago
This error message comes due to non-integer powers, like sqrt(p). Instead use - using this example - sqrt(p+eps) where eps is a machine constant, of the order of 1e-63. This should prevent the error.
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Posted:
9 years ago
Sorry but it did not solve the problem. Is there any way that i can use a function like max(0.1,p), something like that, so that it does not take value of p if it is negative?
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Posted:
9 years ago
Gives an error of non integral power of negative number in my non-Newtonian flow as viscosity is function of Pressure so there is a term of sqrt(p) and I also used sqrt(p+eps) but it doesn't work. Can there be any other solution to this problem?