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Hammer - Setting gravity

Hi

I am modelling a scheme which has a gravity lower than the standard 9.81 due to elevation.

Is there somewhere in Hammer to set this, as surely the available energy will change?

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  • I've heard of users modifying the Specific Gravity calculation option for fluids other than water, (View > Calculation Options > double click active steady state/eps solver option set) but I do not recall hearing about a need to change anything for water at different altitudes. According to wikipedia, the gravitational constant varies by only .0.04 m/s^2 depending on the elevation.

    The only thing I can think of that you would need to change for transient analysis purposes is the pipe Wave Speed (you can account for it using the Wave Speed Calculator Tool) and the vapor pressure limit (default is -9.98 m, as seen in the transient solver calculation options)

    Please clarify if I have misunderstood.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  • Thanks for your help.

    The reason I am concerned about gravity is because I have set hammer to read out pressure in m H2O to match some results which I am trying to emulate. Because this site is at elevation, gravity is notablly less than at sea level, or more specifically, barometric pressure. Thus I would expect the pressure to read slightly differently. I have adjusted the SG of the fluid, ratio'd by the difference in gravity from sea level, to account for this. The results appear more accurate under this method.

    As you mention, I probably now need to modify the wavespeed to reflect this also.

  • As a further note, the gravity at this site is 9.782. At a more detailed look this appears not to be due to elevation but more because the site is almost on the equator. Interestingly wikipedia states a significant difference does occur between the equator and poles. As a side note this must surely affect the energy yield of a station, and in turn a transient event as the energy to be expended will be less.

  • I am curious to know if anyone else has encountered a variation in gravity before and how they handled it?

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