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December 28, 2017, 05:38 |
Modelling Cavitation
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#1 |
New Member
Pina
Join Date: Sep 2017
Posts: 5
Rep Power: 8 |
When modelling cavitation on a hydrofoil, what are the values of inlet and outlet pressure one should enter to obtain a specific cavitation number?
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December 28, 2017, 09:20 |
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#2 |
Member
Daniel Edebro
Join Date: Feb 2016
Location: Gothenburg
Posts: 41
Rep Power: 10 |
The cavitation number is a measure of how close you are to cavitation and it can be defined for every point according to the following formula:
Ca = (p_loc - p_vap)/(0.5*rho*U_inf^2) Where U_inf is the velocity far from the hydrofoil. What do you mean by "optain a specific cavitation number"? |
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December 28, 2017, 09:47 |
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#3 |
New Member
Pina
Join Date: Sep 2017
Posts: 5
Rep Power: 8 |
What i meant to say is that I wanted to carry out the simulation using different cavitation numbers. This can be done by changing the magnitude of velocity.
I initially thought I had a wrong set up however the simulation was not converging due to incorrect initialization. |
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December 28, 2017, 10:57 |
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#4 |
Member
Daniel Edebro
Join Date: Feb 2016
Location: Gothenburg
Posts: 41
Rep Power: 10 |
Ok, maybe this is arguing about semantics but I wouldn't say that you are "using different cavitation numbers". The cavitation number is a part of your solution the same way that pressure is. Or in other words, the cavitation number is always an output never an input to a calculation.
On a side note: If you are doing valve analysis there is a global parameter called cavitation index (sigma) that is defined as: Sigma = (P_up - P_vap) / (P_up - P_down) This parameter can be used as an input value for a CFD calculation. |
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December 28, 2017, 13:59 |
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#5 |
New Member
Pina
Join Date: Sep 2017
Posts: 5
Rep Power: 8 |
I am analysing the cavitational effects on hydrofoils and examining its effect on the lift coefficient.
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