Vapor pocket and friction

Question

Hello, 
 Does a vapor pocket increase friction so that we reach steady state faster than in case if no vapor pocket is present? 
 Thanks in advance

Scott Kampa · Answer

Hello m b, 
 HAMMER using a Darcy-Weisbach friction factor to calculated frictional losses during the transient run. This is based on the discharge coefficient calculated during the initial conditions calculation. You can see flow based on the expansion and contraction of a vapor pocket, so this could contribute to frictional losses. I would recommend reviewing the Theory section in HAMMER, specifically as it relates to friction loss methods, for details. You can find some information here as well, particularly if you are seeing little or no dampening of the pressure wave: Transient pressure wave not dampening or unexpected lack of headloss . 
 Regards, 
 Scott

Vapor pocket and friction

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