Dr. Xia Wang Assistant Professor Department of Mechanical Engineering Tel: Fax: Contact Information:

Turbulent Boundary Layer with separation by Dr. Xia Wang

TBL-with separation  (x) U0U0 U(x,y) Separation Reverse Flow  (x) U0U0 U(x,y) Separation Reverse Flow Favorable pressure gradient (FPG) Adverse Pressure Gradient (APG) xoxo Zero pressure gradient (ZPG)

TBL separation is everywhere Turbine Blade Diffuser Flow around a car Taken from (Hucho and Sovran 1993)

Research Interests Can we characterize the turbulent boundary layers with eventual separation? How to predict the separation position? How can this instruct the car body design?

TBL Separation is an event! ID ITDD Coherent structure Detached flow ID: Incipient Detachment 1% ITD: Intermittent Transitory Detachment 20% TD: Transitory Detachment 50% D: Detachment Cf=0.0

Research Approach- Similarity Analysis The scales for the turbulent boundary layer flow are dictated by the equation and its boundary conditions alone. In the limit as Re , the equations of motion become independent of Re. Thus any scale or function expressing the solutions must also be independent of Pe. (Asymptotic Invariance Principle: AIP, George & Castillo 1997)

Research Approach- Similarity Analysis Apply similarity analysis to RANS

Pressure parameters

Separation Criterion Integral Momentum Equation Replacing the PG parameter from the similarity analysis At separation: Cf  0 H sep =2.76  0.23

Results-1 TBL without separationTBL with separation

Results-2 Consistent with Industrial Practices Hall (2003) : To avoid separation on compressor blades, Hsep<2.5 Elsberry et al (2000): To keep an equilibrium on the verge of separation, Hsep<2.6 Consistent with Measure Results Sandborn & Kline (1961), Kline et al (1983), Sajben & Liao (1995) Hsep=2.7 for the intermittent detachment. Fernholz & Alving (1990) : Hsep=2.85  0.1 Alving & Fernholz (1996) : Hsep=2.78