How to set up Time Step Size correctly ?

shuai_manlou · July 8, 2012, 10:52

Hello everyone, I have been trying to simulate the free-surface flow around a ship in FLUENT, using a VOF(open channel flow)model, hybrid mesh(tetra close to ship, hexa outer domain), SIMPLE and RNG k-e, and yplus mostly in the range of 150-450, the problem is when I set the Time Step Size 0.01(some papers do), the Cd is 0.08, then the Cd changes to 0.04 when I set the Time Step Size to 0.005(some other papers do) . Could u please give me some advices to set the Time Step Size correctly? Thanks~

cfd seeker · July 9, 2012, 05:50

which solver you are using? pressure or density based? what's the length of your domain, inlet velocity and the size of smallest cell in your mesh? tell me the fallowing parameters then I will guide you how to set the time step correctly.....

July 8, 2012, 10:52	How to set up Time Step Size correctly ?	#1
shuai_manlou Member CAO Liushuai Join Date: Apr 2012 Posts: 30 Rep Power: 14	Hello everyone, I have been trying to simulate the free-surface flow around a ship in FLUENT, using a VOF(open channel flow)model, hybrid mesh(tetra close to ship, hexa outer domain), SIMPLE and RNG k-e, and yplus mostly in the range of 150-450, the problem is when I set the Time Step Size 0.01(some papers do), the Cd is 0.08, then the Cd changes to 0.04 when I set the Time Step Size to 0.005(some other papers do) . Could u please give me some advices to set the Time Step Size correctly? Thanks~

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July 9, 2012, 05:50		#2
cfd seeker Senior Member Join Date: Mar 2011 Location: Germany Posts: 552 Rep Power: 20	which solver you are using? pressure or density based? what's the length of your domain, inlet velocity and the size of smallest cell in your mesh? tell me the fallowing parameters then I will guide you how to set the time step correctly.....