Lower vacuum pressure using Scalable Wall function compared to Standard Wall function

harshitsoniii · July 21, 2021, 14:36

Hello,

I am currently running a simulation using Ansys Fluent where for different inlet pressures (10,20,30 psi), the vacuum pressure generated inside the part at a point using Scalable Wall function is lower (-400 Pa) compared to Standard Wall function (-550 Pa). The Mass Flow rate at inlet is the same for both though. Can anyone please explain what could be the reason for this? Irrespective of mesh size, the vacuum pressure at a point inside the part is always lower using scalable wall function compared to Standard Wall function. Thanks in advance!

LuckyTran · July 21, 2021, 17:11

Please, give relevant details of your simulation and model. You are asking for an explanation of why two different black boxes have different garbage out's with the same garbage in.

harshitsoniii · July 22, 2021, 10:38

Thank you for your response LuckyTran.

Sorry for the incomplete details. I'm using a k-epsilon-RNG model with different inlet pressures and a set outlet pressure of 0. The fluid used is air with Ideal-gas density. For a set inlet pressure, Venturi effect takes place inside the part and I'm concerned as to why a point which is placed in the area where the Venturi effect takes places, reports a lower vacuum pressure using Scalable wall function compared to Standard and Enhanced wall function.

Because of the confidentiality of the project, I'm won't be able to share the complete details of the geometry.

July 21, 2021, 14:36	Lower vacuum pressure using Scalable Wall function compared to Standard Wall function	#1
harshitsoniii New Member Harshit Soni Join Date: Jul 2021 Posts: 2 Rep Power: 0	Hello, I am currently running a simulation using Ansys Fluent where for different inlet pressures (10,20,30 psi), the vacuum pressure generated inside the part at a point using Scalable Wall function is lower (-400 Pa) compared to Standard Wall function (-550 Pa). The Mass Flow rate at inlet is the same for both though. Can anyone please explain what could be the reason for this? Irrespective of mesh size, the vacuum pressure at a point inside the part is always lower using scalable wall function compared to Standard Wall function. Thanks in advance!

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July 21, 2021, 17:11		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	Please, give relevant details of your simulation and model. You are asking for an explanation of why two different black boxes have different garbage out's with the same garbage in.

July 22, 2021, 10:38		#3
harshitsoniii New Member Harshit Soni Join Date: Jul 2021 Posts: 2 Rep Power: 0	Thank you for your response LuckyTran. Sorry for the incomplete details. I'm using a k-epsilon-RNG model with different inlet pressures and a set outlet pressure of 0. The fluid used is air with Ideal-gas density. For a set inlet pressure, Venturi effect takes place inside the part and I'm concerned as to why a point which is placed in the area where the Venturi effect takes places, reports a lower vacuum pressure using Scalable wall function compared to Standard and Enhanced wall function. Because of the confidentiality of the project, I'm won't be able to share the complete details of the geometry.