The effects of adverse pressure gradients on momentum and thermal structures in transitional boundary layers. Part 1: Mean quantities

Journal Article · Tue Oct 01 04:00:00 EDT 1996 · Journal of Turbomachinery

DOI:https://doi.org/10.1115/1.2840927· OSTI ID:404410

Mislevy, S P; Wang, T ^[1]

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1. Clemson Univ., SC (United States). Dept. of Mechanical Engineering

The effects of adverse pressure gradients on the thermal and momentum characteristics of a heated transitional boundary layer were investigated with free-stream turbulence ranging from 0.3 to 0.6 %. The acceleration parameter, K, was kept constant along the test section. Both surface heat transfer and boundary layer measurements were conducted. The boundary layer measurements were conducted with a three-wire probe (two velocity wires and one temperature wire) for two representative cases, K1 = {minus}0.51 {times} 10{sup {minus}6} and K2 = {minus}1.05 {times} 10{sup {minus}6}. The surface heat transfer measurements were conducted for K values ranging from {minus}0.045 {times} 10{sup {minus}6} to {minus}1.44 {times} 10{sup {minus}6} over five divergent wall angles. The Stanton numbers of the cases with adverse pressure gradients were greater than that of the zero-pressure-gradient turbulent correlation in the low-Reynolds-number turbulent flow, and the difference increased as the adverse pressure gradient was increased. The adverse pressure gradient caused earlier transition onset and shorter transition length based on Re{sub x}, Re*{sub {delta}}, and Re{sub {theta}} in comparison to zero-pressure-gradient conditions. As expected, there was a reduction in skin friction as the adverse pressure gradient increased. In the U{sup +}-Y{sup +} coordinates, the adverse pressure gradients had a significant effect on the mean velocity profiles in the near-wall region for the late-laminar and early transition stations. The mean temperature profile was observed to precede the velocity profile in starting and ending the transition process, opposite to what occurred in favorable pressure gradient cases in previous studies. A curve fit of the turbulent temperature profile in the log-linear region for the K2 case gave a conduction layer thickness of Y{sup +}=9.8 and an average Pr{sub t}=0.71. The wake region of the turbulent mean temperature profile was significantly suppressed.

• Sponsoring Organization: USDOE
• OSTI ID: 404410
• Report Number(s): CONF-950629--
• Journal Information: Journal of Turbomachinery, Journal Name: Journal of Turbomachinery Journal Issue: 4 Vol. 118; ISSN JOTUEI; ISSN 0889-504X
• Country of Publication: United States
• Language: English

Related Subjects

20 FOSSIL-FUELED POWER PLANTS
33 ADVANCED PROPULSION SYSTEMS
FRICTION FACTOR
GAS COMPRESSORS
GAS TURBINES
HEAT TRANSFER
LAMINAR FLOW
THERMAL EFFICIENCY
TURBULENT FLOW