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axial flow pump, inflow boundary

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Old   September 19, 2002, 08:31
Default axial flow pump, inflow boundary
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tma
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Hi I use TascFlow to learning cavitation in axial flow pump which is imported blade geometry from CAD application to BladeGen and generated grid by Turbogrid. I have some problem about inflow boundary. When I focus on cavitation, I should set type of boundary as pressure but I when I set pressure to negsative value the solver stop due to error. Who does have an ides to solve this problem. How to calculate pressure at inlet of axial flow pump or estimate it from other parameter. I am looking for other guy who work on cavitatin phenomena or interresting my work for exchange data, blade profile and result. Thank everybody to reading this message. Regards
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Old   September 19, 2002, 22:05
Default Re: axial flow pump, inflow boundary
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Robin
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You are setting the total pressure at the inlet. A negative total pressure is not physically correct, unless you specify a corresponding pressure offset in your PRM file. See the documentation on cavitation for more help.

Robin
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Old   September 23, 2002, 02:38
Default Re: axial flow pump, inflow boundary
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tma
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Thank you for your advise on this. I try to set inflow boundary as pressure and outflow as mass flow but solver cannot run.POFF is set 101325 in the text area. When inflow is set on other solver can run and give a good result. I think some parameter shoul be get from exerperiment but now pump is prepared, How to check when solver has overflow or linear error for correct the parameter that make solver faile? What is the cauxe when the solver cannot solve? Could u please advise on this matter.
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Old   September 26, 2002, 15:28
Default Re: axial flow pump, inflow boundary
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GTM
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Since you're looking at cavitation, I assume the pump is not near its design point. If the boundary conditions represent a point that is not stable convergence is difficult. Suggest that an initial convergence be achieved at a more stable condition, then modify the boundary condition and use the restart deck. If the cavitation is severe, this may have to be done in steps. I know this works with surging compressors.
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