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.

Turbulent transport measurements in a heated boundary layer: Combined effects of free-stream

Abstract: Turbulence measurements for both momentum and heat transport are taken in a boundary layer over a flat recovery wall downstream of a concave wall (R = 0.97 m). The boundary layer appears turbulent from the beginning of the upstream, concave wall and grows over the flat test wall downstream of the curved wall with negligible streamwise acceleration. The strength of curvature at the bend exit, δ99.5 /R , is 0.04. The free-stream turbulence intensity (FSTI) is ~8 percent at the beginning of the curve and is nearly uniform at ~4.5 percent throughout the recovery wall. Comparisons are made with data taken in an earlier study, in the same test facility, but with a low FSTI (~0.6 percent). Results show that on the recovery wall, elevated FSTI enhances turbulent transport quantities such as −uν and νt in most of the outer part of the boundary layer, but near-wall values of νt remain unaffected. This is in contrast to near-wall νt values within the curve which decrease when FSTI is increased. At the bend exit, decreases of −uν and νt due to removal of curvature become more profound when FSTI is elevated, compared to low-FSTI behavior. Measurements in the core of the flow indicate that the high levels of cross transport of momentum over the upstream concave wall cease when curvature is removed. Other results show that turbulent Prandtl numbers over the recovery wall are reduced to ~0.9 when FSTI is elevated, consistent with the rise in Stanton numbers over the recovery wall.

Fluid mechanics experiments in oscillatory flow. Volume 2: Tabulated data

Abstract: Results of a fluid mechanics measurement program in oscillating flow within a circular duct are presented. The program began with a survey of transition behavior over a range of oscillation frequency and magnitude and continued with a detailed study at a single operating point. Such measurements were made in support of Stirling engine development. Values of three dimensionless parameters, Re sub max, Re sub w, and A sub R, embody the velocity amplitude, frequency of oscillation, and mean fluid displacement of the cycle, respectively. Measurements were first made over a range of these parameters that are representative of the heat exchanger tubes in the heater section of NASA's Stirling cycle Space Power Research Engine (SPRE). Measurements were taken of the axial and radial components of ensemble-averaged velocity and rms velocity fluctuation and the dominant Reynolds shear stress, at various radial positions for each of four axial stations. In each run, transition from laminar to turbulent flow, and its reverse, were identified and sufficient data was gathered to propose the transition mechanism. Volume 2 contains data reduction program listings and tabulated data (including its graphics).

Measurements of the turbulent transport of heat and momentum in convexly curved boundary layers: effects of curvature, recovery and free-stream turbulence.

Abstract: The effects of streamwise convex curvature, recovery, and freestream turbulence intensity on the turbulent transport of heat and momentum in a mature boundary layer are studied using a specially designed three-wire hot-wire probe. Increased freestream turbulence is found to increase the profiles throughout the boundary layer on the flat developing wall. Curvature effects were found to dominate turbulence intensity effects for the present cases considered. For the higher TI (turbulence intensity) case, negative values of the turbulent Prandtl number are found in the outer half of the boundary layer, indicating a breakdown in Reynolds analogy.

High pressure turbine rotor stage endwall cooling and passage thermal fields as affected by leakage flow and combustor liner coolant streams

Abstract: The effects of an engine-representative combustor exit temperature profile and different disc cavity leakage flow rates on endwall adiabatic effectiveness distributions and passage temperature fields in a high pressure turbine rotor stage of a gas turbine are experimentally documented. The measurements are made on a stationary linear blade row cascade with an axisymmetrically-contoured endwall of modern engine geometry and with engine-representative approach flow thermal and fluid mechanics characteristics. The measurements give insight into mixing of coolant emerging as leakage flow and combustor liner coolant mix with hot core gases ahead of the airfoil row. Reported results are thermal fields in the passage, adiabatic wall temperatures and adiabatic effectiveness values in using an engine-representative approach flow temperature profile and with approach flow temperature profiles with 1) no coolant in the approach flow (flat profile) and 2) coolant only within 10% of the span (approach flow profile with a thin thermal boundary layer).The results give insight into mixing between the leakage flow and the mainstream passage flow and its effects on endwall cooling. The results demonstrate that for the conditions studied; much of the endwall cooling is contributed by the coolant in the approach flow. This is an important result that has previously not been well documented.Copyright © 2013 by ASME

Turbine Vane Passage Cooling Experiments With a Close-Coupled Combustor-Turbine Interface Geometry Part 1: Describing the Flow

Abstract: Due to the proximity of the first stage gas turbine vanes to the combustor, coolant introduced to the combustor walls interacts with the endwall film coolant and changes the vane passage flow physics. Recent results show that combustor coolant contributes significantly to cooling the endwall and vane surfaces. In this paper, the traditional combustor-turbine interface was modified to improve overall cooling performance. The performance of this new injection cooling scheme on passage fluid dynamics and surface cooling is assessed. The first of this two-part paper reports detailed experimental tests that document secondary flows and coolant transport throughout the vane passage for four combustor coolant flowrates. The experimental facility imitates combustor coolant injection and engine-level turbulence and has a modified transition duct design, called the ‘close-coupled combustor-turbine interface.’ The ‘impingement vortex’ seen in previous studies with combustor cooling appears as the dominant secondary flow. It is observed in the present study over a wide range of flowrates, confirming its tie to the combustor coolant flowrate and not the combustor-turbine interface geometry. It was found, however, that the location and size of the impingement vortex are affected by coolant flowrate. The second of this two-part paper discusses the impact of the observed secondary flows on cooling vane passage surfaces.

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.