[Commercial meshers] Total Boundary Layer Height for an airplane

waseeqsiddiqui · April 10, 2019, 11:29

Hello everyone. For a certain airplane containing multiple parts (Wing, Stabilizer etc.), how does one calculate the total boundary layer thickness?
Does one specify the total height differently for each individual component in ICEM or is it wise to specify one common thickness obtained using the mean aerodynamic chord of the wing for all individual parts?

waseeqsiddiqui · August 21, 2019, 10:09

Anyone? Please help

Carlo_P · August 22, 2019, 03:03

Hey waseeqsiddiqui..long name!

I think that you are talking about the prismatic cells next to the wall, correct?

In that case, it is not always simple to know before the simulation.
You have to calculate the first cell high (h1) and then the total tickness is equal to

h1*(er -er*(N+1))/(1-er)

where er is the expansion ratio (normally 1.2) and N is the total number of cells.

h1 can be calculate with: https://www.cfd-online.com/Tools/yplus.php . h1 is the eximated wall distance.

After the simulation, you have to check if the yplus is between the correct range (1-10) for k-omega (20-200) for k-epsilon.
If yplus is inside this range in all the parts, you can maintein the same total tickness.
If yplus is too different in the different parts, you have to reduce the totaltickness where yplus is too high and increase if too low.

Sorry, but it is a complex answer!

waseeqsiddiqui · August 22, 2019, 10:01

Okay, Thanks!

April 10, 2019, 11:29	Total Boundary Layer Height for an airplane	#1
waseeqsiddiqui Member MWRS Join Date: Apr 2018 Location: Islamabad Posts: 99 Rep Power: 8	Hello everyone. For a certain airplane containing multiple parts (Wing, Stabilizer etc.), how does one calculate the total boundary layer thickness? Does one specify the total height differently for each individual component in ICEM or is it wise to specify one common thickness obtained using the mean aerodynamic chord of the wing for all individual parts?

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August 21, 2019, 10:09		#2
waseeqsiddiqui Member MWRS Join Date: Apr 2018 Location: Islamabad Posts: 99 Rep Power: 8	Anyone? Please help

August 22, 2019, 03:03		#3
Carlo_P Senior Member Carlo_P Join Date: May 2019 Location: Italy Posts: 176 Rep Power: 7	Hey waseeqsiddiqui..long name! I think that you are talking about the prismatic cells next to the wall, correct? In that case, it is not always simple to know before the simulation. You have to calculate the first cell high (h1) and then the total tickness is equal to h1(er -er(N+1))/(1-er) where er is the expansion ratio (normally 1.2) and N is the total number of cells. h1 can be calculate with: https://www.cfd-online.com/Tools/yplus.php . h1 is the eximated wall distance. After the simulation, you have to check if the yplus is between the correct range (1-10) for k-omega (20-200) for k-epsilon. If yplus is inside this range in all the parts, you can maintein the same total tickness. If yplus is too different in the different parts, you have to reduce the totaltickness where yplus is too high and increase if too low. Sorry, but it is a complex answer!

August 22, 2019, 10:01		#4
waseeqsiddiqui Member MWRS Join Date: Apr 2018 Location: Islamabad Posts: 99 Rep Power: 8	Okay, Thanks!