Pressure boundary condition

doubtsincfd · August 24, 2010, 18:35

For a problem like laminar flow in a lid driven cavity, we specify the pressure boundary condition as dp/dn = 0. How do we arrive at this boundary condition?

CAVT · August 24, 2010, 19:14

I guess it's like one of Prandlt's boundary layer deductions, stattic pressure doesn't change with height (the normal), that's what the zero derivative means, no change. However, I don't recall well the cavity case.

Hamidzoka · August 25, 2010, 02:54

the pressure gradient across the boundary layer is zero.
it means the pressure inside the boundary layer is equal to that outside the boundary layer.
therefore when you are to solve viscous flow passing a wall, pressure condition will be in fact the zero gradient pressure normal to wall.

regards

CCTech_Pune · August 25, 2010, 07:36

HI

Since the boundary layer thickness is small, it is assumed that within the boundary layer free stream pressure is impressed upon. Hence dp/dn normal to the wall is considered negligible and can be ignored.

Thanks
CCTech Pune

August 24, 2010, 18:35	Pressure boundary condition	#1
doubtsincfd Senior Member Join Date: Nov 2009 Location: Michigan Posts: 135 Rep Power: 16	For a problem like laminar flow in a lid driven cavity, we specify the pressure boundary condition as dp/dn = 0. How do we arrive at this boundary condition?

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August 24, 2010, 19:14		#2
CAVT New Member César Vecchio Join Date: Jul 2010 Location: Córdoba, Argentina Posts: 21 Rep Power: 15	I guess it's like one of Prandlt's boundary layer deductions, stattic pressure doesn't change with height (the normal), that's what the zero derivative means, no change. However, I don't recall well the cavity case.

August 25, 2010, 02:54		#3
Hamidzoka Senior Member Hamid Zoka Join Date: Nov 2009 Posts: 282 Rep Power: 18	the pressure gradient across the boundary layer is zero. it means the pressure inside the boundary layer is equal to that outside the boundary layer. therefore when you are to solve viscous flow passing a wall, pressure condition will be in fact the zero gradient pressure normal to wall. regards

August 25, 2010, 07:36		#4
CCTech_Pune New Member CCTech Join Date: Jul 2010 Posts: 20 Rep Power: 15	HI Since the boundary layer thickness is small, it is assumed that within the boundary layer free stream pressure is impressed upon. Hence dp/dn normal to the wall is considered negligible and can be ignored. Thanks CCTech Pune