Flow past a cylinder. Help needed

Lurapa · July 15, 2013, 10:11

Hey guys,

I am dealing with the 2D incompressible flow past a cylinder problem. I am using FV on unstructured meshes with collocated variables (with Rhie-Chow interpolation) and I am employing the SIMPLE algorithm.

The code works fine on the cavity flow problem and other benchmark problems.

My problem comes with the BC (inlet and outlet). Anyone could help me?

Thanks in advance

leflix · August 18, 2013, 11:25

Hi Lurapa,

Inlet is easy. Generally use U=1, V=0
for outlet many choices are available according the lenght of your domain and your Reynolds number.
you can use dU/dx=0 dV/dx=0
or d²U/dx²=0 dV/dx=0
with mass flow rate correction for outflow velocity so that at the outlet the mass flow rate is ensured and the same as at the inlet.

the most sophisticated outflow BC is the Orlansky BC
dU/dt + Ubarre dU/dx=0
dV/dt + Ubarre dV/dx=0

where Ubarre is the mean velocity in the domain and computed from the mass flow rate.

July 15, 2013, 10:11	Flow past a cylinder. Help needed	#1
Lurapa New Member Luis Join Date: Jul 2011 Posts: 8 Rep Power: 15	Hey guys, I am dealing with the 2D incompressible flow past a cylinder problem. I am using FV on unstructured meshes with collocated variables (with Rhie-Chow interpolation) and I am employing the SIMPLE algorithm. The code works fine on the cavity flow problem and other benchmark problems. My problem comes with the BC (inlet and outlet). Anyone could help me? Thanks in advance

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August 18, 2013, 11:25		#2
leflix Senior Member Join Date: Aug 2011 Posts: 272 Rep Power: 16	Hi Lurapa, Inlet is easy. Generally use U=1, V=0 for outlet many choices are available according the lenght of your domain and your Reynolds number. you can use dU/dx=0 dV/dx=0 or d²U/dx²=0 dV/dx=0 with mass flow rate correction for outflow velocity so that at the outlet the mass flow rate is ensured and the same as at the inlet. the most sophisticated outflow BC is the Orlansky BC dU/dt + Ubarre dU/dx=0 dV/dt + Ubarre dV/dx=0 where Ubarre is the mean velocity in the domain and computed from the mass flow rate.