Accession Number:

ADA566297

Title:

The Prandtl Plus Scaling Parameters and Velocity Profile Similarity

Descriptive Note:

Interim rept. 1 Oct 2011-1 May 2012

Corporate Author:

AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SENSORS DIR

Personal Author(s):

• Weyburne, David

Report Date:

2012-10-01

Pagination or Media Count:

27.0

Abstract:

Numerous experimental results have demonstrated similar behavior of the velocity profile in the near-wall region of the turbulent boundary layer using Prandtls Plus scaling variables. However, the implications for similarity behavior of the near-wall turbulent boundary velocity profiles using Prandtls Plus scaling variables have not been carefully explored. In the following report, we apply the momentum balance type approach to study velocity profile similarity using Prandtls Plus scaling variables. It is shown that the Plus scaling variables do in fact satisfy the requirements for similarity based on this approach so long as the friction velocity is proportional to 1x-x0 where x is the distance along the wall in the flow direction and x0 is a constant. Experimental results are examined and found to confirm that certain datasets we tested do in fact have the friction velocity values behaving as 1x-x0. We show the Plus scaling variables satisfy all of the conditions for similarity using the momentum balance type approach for these datasets. However, the same velocity profile dataset plots also confirm that Prandtls Plus scaling variables do not show whole profile similarity. Hence, we conclude that the scaling variables discovered by the momentum balance type approach as presently constituted are a necessary but not sufficient condition for velocity profile similarity..

Descriptors:

• *PRANDTL NUMBER
• *TURBULENT BOUNDARY LAYER
• BOUNDARY LAYER
• BOUNDARY LAYER FLOW
• FRICTION
• MOMENTUM
• REQUIREMENTS
• SCALING FACTOR
• TURBULENT FLOW
• VELOCITY

Subject Categories:

• Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE