ESDU TM 181
An assessment of methods for estimation of turbulent boundary-layer profiles
Knowledge of the boundary-layer velocity profile provides useful information required to calculate the drag of surface imperfections (or excrescences) of height less than the thickness of the boundary layer. A body placed within the boundary layer causes a drag component which is a function of an effective kinetic pressure. For such cases can be derived from the velocity distribution.
The current methods and data used by the aerospace industry to determine the excrescence drag due to surface imperfections are mainly based on the ESDU Aerodynamic Data Items and have an excrescence height to boundary-layer thickness limit of 10.0%. Investigations have shown, for cases where the excrescence height is greater than 10% of the turbulent boundary-layer thickness, that by applying a correction based on the change in effective dynamic pressure, the adjusted drag increase shows better agreement with experiment. Therefore it is possible to relax the current limitation on excrescence height by applying a correction factor based on obtaining an effective kinetic pressure adjustment from the local turbulent boundary-layer profile.
This Technical Memo compares a selection of experimental cases with various methods that can be used to calculate the turbulent boundary-layer profile. The important aspect is to establish a rapid technique to predict the boundary-layer thickness and also produce a good representation of the turbulent boundary-layer profile for a range of retarded flows up to flow separation.
|Data Item ESDU TM 181|
- Aircraft Noise
- Fatigue - Endurance Data
- Fatigue - Fracture Mechanics
- Fluid Mechanics, Internal Flow
- Fluid Mechanics, Internal Flow (Aerospace)
- Heat Transfer
- Physical Data, Chemical Engineering
- Stress and Strength
- Transonic Aerodynamics
- Vibration and Acoustic Fatigue
- Wind Engineering