Statistical stationary states for a two-layer quasi-geostrophic system

Existence of a family of locally invariant probability measures for large scale flows in enclosed temperate sea is proved. This model is extremely important for understanding the meso-scale phenomena in oceans. The techniques used are those developed by Albeverio and his collaborators.     

Experimental studies on steady free convection heat transfer from fins and fin arrays

This paper deals with an experimental study of free convective heat transfer from fins and fin arrays attached to a heated horizontal base. The technique of differential interferometry has been utilised and experiments have been carried out under steady state conditions. Local values of heat flux, temperature, heat transfer coefficients, local and overall Nusselt numbers have been estimated. An attempt has been made to discuss in detail the flow and heat transfer mechanisms for three cases namely an isothermal vertical flat plate, a single fin attached to a heated horizontal base and a fin array in the light of the experimental findings. Correlations are presented relating the overall Nusselt number with the relevant non-dimensional parameters in these cases.Diese Abhandlung beschäftigt sich mit einer experimentellen Studie über freie konvektive Wärmeübertragung von Rippen und Rippenfeldern, die an eine erwärmte horizontale Grundfläche angebracht sind. Es wurde die Technik der differentiellen Interferometrie verwendet. Die Versuche sind unter konstanten Zustandsbedingungen ausgeführt worden. Lokale Werte des Wärmestroms, der Temperatur, des Wärmeübertragungskoeffizienten sowie lokale und mittlere Nusseltzahlen sind bestimmt worden. Der Strömungs- und Wärmeübertragungsmechanismus wurde an drei Fällen detailliert untersucht: nämlich eine isotherme vertikale ebene Platte; eine einzelne Rippe, angebracht an einer beheizten horizontalen Grundfläche und ein dem Strahlengang entsprechend angeordnetes Rippenfeld. Für diese drei Fälle werden die Berechnungen der mittleren Nusseltzahl in Abhängigkeit der relevanten dimensionslosen Parameter dargestellt.     

Experimental analysis of unsteady free convection heat transfer from horizontal fin arrays

Experimental work has been carried out on horizontal fin arrays using the differential interferometric technique. The local variations of heat flux and temperature in the central fin of a three fin array have been studied in the transient heating and cooling regimes. The average values of heat transfer coefficients in the transient state have been calculated for three spacings of 10 mm, 15 mm and 25 mm and with two materials namely aluminum and mild steel under constant heat input to the system. The results have been compared with experimental findings in the cases of a single fin attached to a base and a vertical isothermal flat plate. Attempt has been made to explain the differences between these cases in relation to the physical mechanism of heat and fluid flow about a fin array.

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Eine experimentelle Untersuchung der Wärmeübertragung bei instationärer freier Konvektion an horizontalen Rippenanordnungen

Zusammenfassung Unter Anwendung der Differential-Interferometrie-Technik wurde eine experimentelle Arbeit auf dem Gebiet horizontaler Anordnungen von Kühlrippen durchgeführt. Die lokale Veränderung von Wärmestrom und Temperatur der mittleren Rippe einer Dreieranordnung wurde an transienten Heiz- und Kühlbereichen untersucht. Im transienten Zustand wurden die Durchschnittswerte der Wärmeübertragungskoeffizienten bei konstanter Wärmezuführ in das System für Aluminium und Flußstahl bei Zwischenräumen von 10 mm, 15 mm und 20 mm berechnet. Die Berechnungen wurden mit experimentellen Ergebnissen einer einzigen, auf einer Basis befestigten Rippe und einer vertikalen isothermen flachen Platte verglichen. Es wurde der Versuch gemacht, den Unterschied zwischen diesen Fällen, in bezug auf den physikalischen Mechanismus der Wärmeübertragung und Strömung über eine Rippenanordnung, zu erklären.

     

Unsteady fluid flow and heat transfer over a bank of flat tubes

Transient numerical simulations of fluid flow and heat transfer over a bank of flat tubes have been carried for both in-line and staggered configurations for the following boundary conditions: (a) isothermal and (b) isoflux. The effect of Reynolds number, Prandtl number, length ratio, and the height ratio, on the Nusselt number, and the dimensionless pressure drop are elucidated. Correlations are proposed for both pressure drop and Nusselt number and optimum configurations have been determined.     

Approximate solution of non-linear transient heat conduction in cylindrical geometry

The applicability of the Heat Balance Integral method (HBI) using hybrid profiles (HP _n ) for heat diffusion problems in cylindrical geometry is studied. Three test problems are taken to validate the method, namely, TP1 — long hollow cylinder, inner boundary is supplied with constant heat flux and the outer boundary is at infinity, TP2 — the same geometry with the inner boundary at constant temperature, TP3 — the same geometry with convection at the boundary. It is found that HBI in combination with HP _n gives much better solutions as compared to the HBI-polynomial (P _n ) combinations. This method is applied to non-linear cases like temperature dependent thermal conductivity, boiling or condensation at the boundary. For assessment of accuracy Root Mean Square Residual (E _rms) is defined. The residual minimization technique is used to select the parameter in the HP _n profile. It is shown that this procedure yields solutions which are in excellent agreement with the available exact solutions in the case of the three test problems. In the case of nonlinear problems, the value ofE _rms which is comparable to the values in the test cases, shows that the HBI-HP _n is a very good combination for all problems.In dieser Studie wurde die Verwendbarkeit des Wärmebilanz-Integrationsverfahrens (HBI) unter Benutzung von hybriden Profilen (HP _n ) für Wärmeausbreitungsprobleme in zylindrischen Geometrien untersucht. Um das Verfahren zu veranschaulichen wurden drei Testprobleme genommen; wobei für alle drei Fälle die gleiche Geometrie benützt wurde, und zwar ein langer, ausgehöhlter Zylinder. Beim TP-1 ist die innere Grenze mit konstantem Wärmestrom versorgt und die äußere Grenze ist im Unendlichen angenommen worden. Beim TP-2 herrscht an der inneren Grenze eine konstante Temperatur. Beim TP-3 herrscht Konvektion an den Grenzen. Hierbei wurde festgestellt, daß HBI in Verbindung mit HP _n sehr viel bessere Lösungen liefert, als die HBI-Polynom-Kombinationen (P _n ). Dieses Verfahren ist für nicht lineare Fälle, wie temperaturabhängige Wärmeleitfähigkeit, Sieden oder Kondensation and den Grenzen verwendet worden. Für die Abschätzung der Genauigkeit ist das restliche quadratische Mittel definiert worden. Die Residuen-Minimisierungstechnik ist für die Auswahl des Parameters \ benützt worden. Es ist gezeigt worden, daß dieses Verfahren Lösungen liefert, welche mit den benützten genauen Lösungen der drei Testfälle hervorragend übereinstimmen. Im Fall der nicht linearen Probleme zeigt der Wert vonE _rms, der mit den Testfällen vergleichbar ist, daß die HBI-HP _n eine sehr gute Kombination für alle Probleme ist.     

High-resolution emission spectroscopy of CO2 collisionally excited by N2. Rotational distribution

We obtained, for the first time, high-resolution rotational distribution of CO₂ collisionally excited by N₂. The rotational distribution is non-Boltzmann, and the initial results suggest that surprisingly large impact parameter collisions contribute substantially to the collisional excitation, even though small impact parameter collisions are more effective, as expected.     

Evolution of vibrational properties during a macromolecule's growth

The elastic constants and vibrational contributions to thermal properties of three polymerizing liquids were investigated by using the available hypersonic velocity measured by Brillouin light scattering in real time. During the addition polymerization to a molecular network structure, Poisson's ratio upsilon(Poisson) decreases approximately according to exp[-(kt(polym))]n, where both k and n are composition dependent. The Debye frequency increases and the corresponding heat capacity, energy, and entropy approaching a limiting value. upsilon(Poisson) of the vitrified polymer continues to decrease but much more slowly, indicating its continued slow polymerization and structural relaxation with time. In the potential energy landscape interpretation, a polymerizing liquid's state point continuously shifts to another landscape's more curved, deeper minima.     

Locating and staffing service centers under service level constraints

Many firms experience demand from geographically dispersed customers. This demand is satisfied by mobile servers that travel to the site of the customer. To achieve this in a cost-effective manner, the firm needs to decide where to locate its service centers, which customer regions to assign to the centers and the staffing level   at each center so that customers experience a defined level of service at minimum cost. To determine adequate staffing levels, we approximate a service center and the customer regions assigned to it as an M/G/s$M/G/s$ queueing system. Based on this queueing model, we explore properties of two different staffing level functions. The queueing model is embedded in a large-scale integer program. Using the concept of column generation, we develop an algorithm that can efficiently solve moderate-sized problems.     

Experiment Driven Ann-GA Based Technique for Optimal Distribution of Discrete Heat Sources Under Mixed Convection

This article reports the results of mixed convection heat transfer studies from five heat sources (aluminum) mounted at different positions on a substrate board (Bakelite). The goal is to determine the optimal arrangement, such that, the maximum temperature excess is minimum among all the possible configurations. For accomplishing this, a completely experimental driven hybrid optimization strategy, that combines Artificial neural network (ANN) with Genetic algorithm (GA) is used. Initial optimization studies are carried out by employing a heuristic non-dimensional geometric parameter λ, which is identified to be the key parameter to decide the maximum temperature in the system.     

Plasma waves in a stochastic magnetic field

The effect of a weak stochastic magnetic field on circular polarized waves in a plasma is investigated. It is shown that the waves are damped. The damping coefficients in various cases of interest are evaluated.