Terrence W. Simon

Bio: Terrence W. Simon is an academic researcher from University of Minnesota. The author has contributed to research in topics: Heat transfer & Turbulence. The author has an hindex of 37, co-authored 305 publications receiving 5025 citations. Previous affiliations of Terrence W. Simon include Motorola & DuPont.

An Experimental Investigation of Transition as Applied to Low Pressure Turbine Suction Surface Flows

Abstract: Results of an experimental study of flow separation and transition in either attached boundary layers or separated shear layers over the suction surface of a simulation of a low-pressure turbine airfoil flow are presented. Detailed velocity profiles were measured with the hot-wire technique. Static pressure distributions are also presented. Flow transition is documented using measured intermittency distributions in the boundary layer and the separated shear layer. Cases for Reynolds numbers of 50,000, 100,000, 200,000 and 300,000 are reported. These Reynolds numbers are based on suction surface length and exit velocity. Three Free Stream Turbulence Intensity values, 0.5%, 2.5% and 10%, are represented. Flow separation is observed for all the low-FSTI cases. Of these, the lowest Reynolds number case was not able to complete transition of the shear layer and the separation bubble persisted over the entire blade surface. For the other low-FSTI cases, transition is observed in the shear layer over the separation bubble. This transition proceeded quickly, spreading rapidly toward the wall. Elevated FSTI drives an earlier transition than in the low-FSTI cases and the separation bubbles are smaller. For the highest Reynolds number cases with 2.5% and 10% FSTI, transition is of the attached boundary layer and no separation exists. Flow separation with shear flow transition is observed for the lower-Re cases. Models for intermittency and transition length and location from the modern literature are assessed.

Free-stream turbulence and concave curvature effects on heated, transitional boundary layers

Abstract: An experimental investigation of the transition process on flat-plate and concave curved-wall boundary layers for various free-stream turbulence levels was performed. Results show that for transition of a flat-plate, the two forms of boundary layer behavior, identified as laminar-like and turbulent-like, cannot be thought of as separate Blasius and fully-turbulent profiles, respectively. Thus, simple transition models in which the desired quantity is assumed to be an average, weighted on intermittency, of the theoretical laminar and fully turbulent values is not expected to be successful. Deviation of the flow identified as laminar-like from theoretical laminar behavior is shown to be due to recovery after the passage of a turbulent spot, while deviation of the flow identified as turbulent-like from the full-turbulent values is thought to be due to incomplete establishment of the fully-turbulent power spectral distribution. Turbulent Prandtl numbers for the transitional flow, computed from measured shear stress, turbulent heat flux and mean velocity and temperature profiles, were less than unity. For the curved-wall case with low free-stream turbulence intensity, the existence of Gortler vortices on the concave wall within both laminar and turbulent flows was established using liquid crystal visualization and spanwise velocity and temperature traverses. Transition was found to occur via a vortex breakdown mode. The vortex wavelength was quite irregular in both the laminar and turbulent flows, but the vortices were stable in time and space. The upwash was found to be more unstable, with higher levels of u' and u'v', and lower skin friction coefficients and shape factors. Turbulent Prandtl numbers, measured using a triple-wire probe, were found to be near unity for all post-transitional profiles, indicating no gross violation of Reynolds analogy. No evidence of streamwise vortices was seen in the high turbulence intensity case.

Measurements Over a Film-Cooled, Contoured Endwall With Various Coolant Injection Rates

Abstract: This paper presents the results of a study of film coverage for coolant injection through an axisymmetric, contoured endwall of a high-pressure turbine first stage vane row. Tests are done on a low speed, linear cascade. The injection is either through a single slot upstream of the leading edges of the vanes or through two slots, one upstream of the other. Because the contouring begins upstream of the leading edges, injection is in an accelerating flow region. The effects of such injection on the secondary flows within the vane cascade are inferred by means of contours of dimensionless temperature. These thermal measurements are made by slightly heating the injection stream above the main flow temperature and documenting the temperatures inside the coolant-mainstream mixing zone. The thermal results are complemented with three-component, hot-wire measurements taken near the exit plane. Performance with different injection rates is discussed. The secondary flow seems to affect the cooling flow strongly when the momentum of the injected flow is small, compared to the main flow momentum. As a result, coolant coverage is non-uniform, with most of the coolant accumulating near the suction side of the passage. As the injection momentum is increased, some pressure-side accumulation of coolant is observed. However, non-uniformity still exists, with a lesser amount of coolant in the central region and more near the suction and pressure surfaces. For the same ratio of coolant to mainstream mass flow rates, cooling through a single slot seems to give more cooling towards the pressure side than does cooling through two slots. With the same mass flow rate, the one-slot case has higher injection momentum than does the two-slot case. This indicates that momentum flux is an important parameter in establishing the distribution of the coolant within the passage.Copyright © 2001 by ASME

Boundary Layer Theory

Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Numerical Heat Transfer And Fluid Flow

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Assessment of high-heat-flux thermal management schemes

Abstract: This paper explores the recent research developments in high-heat-flux thermal management. Cooling schemes such as pool boiling, detachable heat sinks, channel flow boiling, microchannel and mini-channel heat sinks, jet-impingement, and sprays, are discussed and compared relative to heat dissipation potential, reliability, and packaging concerns. It is demonstrated that, while different cooling options can be tailored to the specific needs of individual applications, system considerations always play a paramount role in determining the most suitable cooling scheme. It is also shown that extensive fundamental electronic cooling knowledge has been amassed over the past two decades. Yet there is now a growing need for hardware innovations rather than perturbations to those fundamental studies. An example of these innovations is the cooling of military avionics, where research findings from the electronic cooling literature have made possible the development of a new generation of cooling hardware which promise order of magnitude increases in heat dissipation compared to today's cutting edge avionics cooling schemes.