# How to get a constant rotation speed?

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 May 10, 2004, 05:48 How to get a constant rotation speed? #1 Mangnan Guest   Posts: n/a Hi everyone: I am now simulating a hydraulic turbine.And I use a rotation reference frame.I specified an angular velocity of 400 rpm which I assumed.So the angular velocity is not constant one.Then the fluid domain will accelerate aroud its aixs.Could anybody tell me how to get it? Best Regards, Mangnan

 May 10, 2004, 08:23 Re: How to get a constant rotation speed? #2 Mangnan Guest   Posts: n/a Hi everyone: Sorry I made a mistake in the message.Now I correct it. I am now simulating a hydraulic turbine.And I use a rotation reference frame.I specified an angular velocity of 400 rpm which I assumed.So the angular velocity is not constant one.Then the impeller will accelerate aroud its aixs.Could anybody tell me how to get it? Best Regards, Mangnan

 May 11, 2004, 03:00 Re: How to get a constant rotation speed? #3 pp Guest   Posts: n/a Did you have correct inlet condition at inlet section (inlet at spiral casing)? Regards, pp

 May 11, 2004, 09:52 Re: How to get a constant rotation speed? #4 Mangnan Guest   Posts: n/a Hi pp: I know that to get the constant rotation speed I should adjust inlet condition.I am a freshman in hydraulic turbine simulating. I don't how to adjust it.When I correct the inlet condition,what should I depend on? Should I increase the inlet velocity(in my model I sspecified a inlet velocity)or decrease it? Some experts tell me I should adjust the inlet condition in order to get zero net torque.But the zero net torque is another problem which confuse me. Do you have another way to get the constant rotation speed? Hope you and other experts give me some information about it. Thanks Mangnan

 May 12, 2004, 03:59 Re: How to get a constant rotation speed? #5 Mangnan Guest   Posts: n/a Hi everyone: I think my problem is a very fundamental one. So people who simulate the hydraulic turbine model would encounter such problem.How they solve it? Best Regards, Mangnan

 May 12, 2004, 07:49 Re: How to get a constant rotation speed? #6 pp Guest   Posts: n/a If you are simulating fluid flow through hydraulic machine (existing) then you should know runner angular velocity (rpm). Inlet conditions can taken by velocity inlet (if you knew volumetric flow rate) or total pressure which can be calculated. Hydraulic losses in penstock should be taken into account. Hope I help you in some way. Regards, pp

 May 13, 2004, 00:47 How to get a constant rotation speed? Unsolved! #7 Mangnan Guest   Posts: n/a Hi pp: Yes,you are right.I got the angular velocity from experiment. But we do not know whether the angular velocity is a constant one using in the simulation.Then the impeller will accelerate around its axis.And we can not trust the results from our simulation. What a confused problem!

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