Richard J Goldstein

Bio: Richard J Goldstein is an academic researcher from University of Minnesota. The author has contributed to research in topics: Heat transfer & Heat transfer coefficient. The author has an hindex of 56, co-authored 242 publications receiving 14047 citations. Previous affiliations of Richard J Goldstein include University of Illinois at Chicago & Tulane University.

Effect of surface roughness on film cooling performance.

Abstract: Etude experimentale par la technique du transfert de masse. On etudie deux geometries d'injection et 6 types de rugosite. Etude de l'influence du type de rugosite sur l'efficacite moyenne et sur l'uniformite laterale de l'efficacite

Effects of Hole Arrangements on Local Heat/Mass Transfer for Impingement/Effusion Cooling With Small Hole Spacing

Abstract: The present study investigates the local heat (mass) transfer characteristics of flow through perforated plates. Two parallel perforated plates placed, relative to each other, in either staggered, in-line or shifted in one direction. Hole length to diameter ratio of 1.5, hole pitch to diameter ratio of 3.0, and distance between the perforated plates of 1 to 3 hole diameters are used at hole Reynolds numbers of 3,000 to 14,000. For flows through the staggered layers and the layers shifted in one direction, the mass transfer rates on the windward surface of the second wall increase approximately 50% from impingement cooling alone and are about three to four times that with effusion cooling alone (single perforated plate). The high transfer rate is induced by strong secondary vortices formed between two adjacent impinging jets that are accelerated by the effusion flow. The overall transfer rate is dominated by the target (second) surface (approximately 50%) instead of the inside hole surface that is dominant with a single plate case. The transfer coefficient for the in-line layers is approximately 100% higher on the windward surface of the second wall than that of the single plate case. The transfer coefficient on the leeward surface for the second plate is affected little by upstream flow conditions.Copyright © 2004 by ASME

An experimental study on natural convection heat transfer in an inclined square enclosure containing internal energy sources

Abstract: An experiment was carried out to study two-dimensional laminar natural convection within an inclined square enclosure containing fluid with internal energy sources bounded by four rigid planes of constant equal temperature. Inclination angles, from the horizontal, of 0, 15, 30, and 45 deg for Rayleigh numbers from 1.0 {times} 10{sup 4} to 1.5 {times} 10{sup 5} were studied. At inclined angles of 0 and 15 deg, there are two extreme values of temperature and temperature gradient within the fluid, while there is only one at 30 and 45 deg. Local and average Nusselt numbers are obtained on all four walls. As the inclination angles increases, the average Nusselt number increases on the right (upper) and bottom walls, decreases on the left (lower) wall and stays almost constant on the top wall.

Pattern formation outside of equilibrium

Abstract: A comprehensive review of spatiotemporal pattern formation in systems driven away from equilibrium is presented, with emphasis on comparisons between theory and quantitative experiments. Examples include patterns in hydrodynamic systems such as thermal convection in pure fluids and binary mixtures, Taylor-Couette flow, parametric-wave instabilities, as well as patterns in solidification fronts, nonlinear optics, oscillatory chemical reactions and excitable biological media. The theoretical starting point is usually a set of deterministic equations of motion, typically in the form of nonlinear partial differential equations. These are sometimes supplemented by stochastic terms representing thermal or instrumental noise, but for macroscopic systems and carefully designed experiments the stochastic forces are often negligible. An aim of theory is to describe solutions of the deterministic equations that are likely to be reached starting from typical initial conditions and to persist at long times. A unified description is developed, based on the linear instabilities of a homogeneous state, which leads naturally to a classification of patterns in terms of the characteristic wave vector q0 and frequency ω0 of the instability. Type Is systems (ω0=0, q0≠0) are stationary in time and periodic in space; type IIIo systems (ω0≠0, q0=0) are periodic in time and uniform in space; and type Io systems (ω0≠0, q0≠0) are periodic in both space and time. Near a continuous (or supercritical) instability, the dynamics may be accurately described via "amplitude equations," whose form is universal for each type of instability. The specifics of each system enter only through the nonuniversal coefficients. Far from the instability threshold a different universal description known as the "phase equation" may be derived, but it is restricted to slow distortions of an ideal pattern. For many systems appropriate starting equations are either not known or too complicated to analyze conveniently. It is thus useful to introduce phenomenological order-parameter models, which lead to the correct amplitude equations near threshold, and which may be solved analytically or numerically in the nonlinear regime away from the instability. The above theoretical methods are useful in analyzing "real pattern effects" such as the influence of external boundaries, or the formation and dynamics of defects in ideal structures. An important element in nonequilibrium systems is the appearance of deterministic chaos. A greal deal is known about systems with a small number of degrees of freedom displaying "temporal chaos," where the structure of the phase space can be analyzed in detail. For spatially extended systems with many degrees of freedom, on the other hand, one is dealing with spatiotemporal chaos and appropriate methods of analysis need to be developed. In addition to the general features of nonequilibrium pattern formation discussed above, detailed reviews of theoretical and experimental work on many specific systems are presented. These include Rayleigh-Benard convection in a pure fluid, convection in binary-fluid mixtures, electrohydrodynamic convection in nematic liquid crystals, Taylor-Couette flow between rotating cylinders, parametric surface waves, patterns in certain open flow systems, oscillatory chemical reactions, static and dynamic patterns in biological media, crystallization fronts, and patterns in nonlinear optics. A concluding section summarizes what has and has not been accomplished, and attempts to assess the prospects for the future.

Experimental and Theoretical Investigation of Backward-Facing Step Flow

Abstract: Laser-Doppler measurements of velocity distribution and reattachment length are reported downstream of a single backward-facing step mounted in a two-dimensional channel. Results are presented for laminar, transitional and turbulent flow of air in a Reynolds-number range of 70 < Re < 8000. The experimental results show that the various flow regimes are characterized by typical variations of the separation length with Reynolds number. The reported laser-Doppler measurements do not only yield the expected primary zone of recirculating flow attached to the backward-facing step but also show additional regions of flow separation downstream of the step and on both sides of the channel test section. These additional separation regions have not been previously reported in the literature.Although the high aspect ratio of the test section (1:36) ensured that the oncoming flow was fully developed and two-dimensional, the experiments showed that the flow downstream of the step only remained two-dimensional at low and high Reynolds numbers.The present study also included numerical predictions of backward-facing step flow. The two-dimensional steady differential equations for conservation of mass and momentum were solved. Results are reported and are compared with experiments for those Reynolds numbers for which the flow maintained its two-dimensionality in the experiments. Under these circumstances, good agreement between experimental and numerical results is obtained.

Turbulent flows over rough walls

Abstract: ▪ AbstractWe review the experimental evidence on turbulent flows over rough walls. Two parameters are important: the roughness Reynolds number ks+, which measures the effect of the roughness on the buffer layer, and the ratio of the boundary layer thickness to the roughness height, which determines whether a logarithmic layer survives. The behavior of transitionally rough surfaces with low ks+ depends a lot on their geometry. Riblets and other drag-reducing cases belong to this regime. In flows with δ/k ≲ 50, the effect of the roughness extends across the boundary layer, and is also variable. There is little left of the original wall-flow dynamics in these flows, which can perhaps be better described as flows over obstacles. We also review the evidence for the phenomenon of d-roughness. The theoretical arguments are sound, but the experimental evidence is inconclusive. Finally, we discuss some ideas on how rough walls can be modeled without the detailed computation of the flow around the roughness element...