Why does time-step affect average and variance of flow speed at a point? -- CFD Online Discussion Forums

May 20, 2018, 16:41	Why does time-step affect average and variance of flow speed at a point?	#1
kingjewel1 Senior Member Join Date: Jul 2009 Posts: 260 Rep Power: 17	I'm modelling flow past a surface mounted cube and monitoring the upstream flow speed upstream of the cube. I've run it using SAS-SST using SIMPLEC in Fluent. Cube is 6mx6mx6m, domain is 10H x 6H x 3H and mesh size ranges from H/100 to 6H/100. Inlet speed is 2m/s at cube eave height. Time step was set initially at 0.01s. This is a time-series of front face averaged pressure. The red is from unperturbed flow. The green is from perturbed flow using the inlet Vortex Method and 1000 eddies. The blue is using a delta t of 0.05s. Why should there be a difference in both mean and variance of the green and the blue data sets?

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