Viscous Dissipation

Reflecting internal gravity waves in a stratified fluid preserve their frequency and thus their angle with the gravitational directi on. This leads to a focusing or defocus- ing of the waves at boundaries that are neither hor izontal nor vertical. Previous theoreti- cal and experimental work has demonstrated how this can result in the internal wave en- ergy being focused

Numerical simulation based on finite numerical methods is used to predict the production process by injection molding of two polymers parts used in low cost domestic refrigerators. The Hele-Shaw fluid mechanics model along with the volume of fluid method are used to calculate velocity and pressure for non- newtonian polymer flows during the injection process using finite elements. The energy equation, with transient, convective, diffusive and viscous dissipation terms, describing the cooling process of the heated polymer while being injected in the cold mold, is solved by the finite difference method. Results for the time evolution of polymer front, pressure and temperature distributions during injection of Polystrol 495F in the mould cavity to produce the freezer door, obtained from two different non-newtonian fluid models, three mold temperatures and two thickness are presented. The effects of the location of the injection point and heat transfer coefficient between polymer flow a...

The study of MHD and nano effect on the flow over a moving surface in presence
of thermal radiation, vis
Engineering processes can be modeled as flow over a moving surface. Viscous
nanofluid flows play very important role in chemical engineering. So in this paper the
effect of viscous dissipation and chemi
layer region is studied. The governing equations are solved by HAM by considering
plate movement in both the directions. The effects of non
graphically represented and the results

This study focuses on the analytical solution for the chemical reaction and melting heat transfer effects on MHD steady two-dimensional laminar viscous incompressible radiating boundary layer flow over a flat plate in the presence of variable fluid properties and Soret effect. The presence of viscous dissipation is also put into consideration at the plate under the influence of uniform transverse magnetic field. A mathematical model is developed to investigate the heat transfer characteristics occurring during the melting process due to a stretching sheet. The model contains nonlinear coupled partial differential equations which have been transformed into a system of ordinary differential equation via suitable similarity variables and then solved analytically by employing the Homotopy analysis method (HAM). The convergence of the series solution is established. The impact of various controlling parameters on the flow, heat and mass transfer characteristics are analyzed and discussed in detail through graphs and tables. The velocity and temperature depreciate with increase in radiation parameter and variable viscosity parameter. It is observed that for rising values of magnetic field parameter, variable viscosity parameter, and Prandtl number, the local skin friction increases while a reverse effect is seen in the case of Grashof number and melting parameter. It is found that the temperature decreases as the thermal radiation and melting parameter increase.

Energy conservation and sustainable development demands have been driving research efforts, within the scope of thermal engineering, towards more energy efficient equipments and processes. In this context, the scale reduction in mechanical fabrication has been permitting the miniaturization of thermal devices, such as in the case of micro-heat exchangers [1]. More recently, heat exchangers employing micro-channels with characteristic dimensions below 500 μm have been calling the attention of researchers and practitioners, towards applications that require high heat removal demands and/or space and weight limitations [2]. Recent review works [2, 3] have pointed out discrepancies between experimental results and classical cor-relation predictions of heat transfer coefficients in micro-channels. Such deviations have been stimulating theoretical research efforts towards a better agreement between experiments and simulations, through the incorporation of different effects that are either typically present in micro-scale heat transfer or are effects that are normally disregarded at the macro-scale and might have been erroneously not accounted for in micro-channels. Our own research effort was first related to the fundamental analysis of forced convection within micro-channels with and without slip flow, as required for the design of micro-heat exchangers in steady, periodic and transient regimen [4, 5]. Also recently in Refs. [6–11], the analytical contributions were directed towards more general problem formulations, including viscous dissipation, axial diffusion in the fluid and three-dimensional flow geometries. Then, this fundamental research was extended to include the effects of axial fluid heat conduction and wall corrugation or roughness on heat transfer enhancement [12]. The work of Maranzana et al. [13] further motivated the present analysis, dealing with longitudinal wall heat conduction effects in symmetric micro-channels.

This paper concerns the effects of conduction and viscous dissipation on natural convection flow of an incompressible, viscous and electrically conducting fluid in the presence of transverse magnetic field. Numerical solutions for the governing momentum and energy equations are given. A discussion has been provided for the effects of magnetic parameter, Prandtl number, conjugate conduction parameter and viscous dissipation parameter on two-dimensional flow. Results for the details of the velocity, temperature distributions as well as the skin friction and the rate of heat transfer are shown graphically. Also the numerical values of the surface temperature distributions are presented in tabular form.

An analysis is performed to study the MHD flow of an electrically conducting, incompressible, viscous fluid past a semi-infinite vertical plate with mass transfer, under the action of transversely applied magnetic field is carried out. The heat due to viscous dissipation and the induced magnetic field are assumed to be negligible. The dimensionless governing equations are unsteady, two-dimensional, coupled and non-linear partial differential equations. A most accurate, unconditionally stable and fast converging implicit finite difference scheme is used to solve the non-dimensional governing equations. The effects of external cooling (Gr > 0) of the plate by the free convection are studied.

The solution of extended Graetz problem for micro-scale gas flows is performed by coupling of rarefaction, axial conduction and viscous dissipation at slip flow regime. The analytical coupling achieved by using Gram–Schmidt orthogonalization technique provides interrelated appearance of corresponding effects through the variation of non-dimensional numbers. The developing temperature field is determined by solving the energy equation locally together with the fully developed flow profile. Analytical solutions of local temperature distribution, and local and fully developed Nusselt number are obtained in terms of dimensionless parameters: Peclet number, Knudsen number, Brinkman number, and the parameter Kappa accounting temperature-jump. The results indicate that the Nusselt number decreases with increasing Knudsen number as a result of the increase of temperature jump at the wall. For low Peclet number values, temperature gradients and the resulting temperature jump at the pipe wall cause Knudsen number to develop higher effect on flow. Axial conduction should not be neglected for Peclet number values less than 100 for all cases without viscous dissipation, and for short pipes with viscous dissipation. The effect of viscous heating should be considered even for small Brinkman number values with large length over diameter ratios. For a fixed Kappa value, the deviation from continuum increases with increasing rarefaction, and Nusselt number values decrease with an increase in Knudsen number.

We have characterized pumice products belonging to the climactic phase of the 800-year-b.p. Quilotoa eruption. Bulk rock compositions, petrography, mineral, and glass chemistry and textural investigations were performed on the three end-member pumice types, namely white, gray, and mingled pumices. All the investigated pumice clasts are dacites characterized by the same bulk rock composition and mineralogical assemblage, but glass compositions and bulk textures change according to different pumice types. White pumice has higher crystallinity ( 48 wt%), abundant euhedral pheno/microphenocrysts, no groundmass microlites, the most evolved glass compositions (74-78 wt% SiO2), and heterogeneous vesicle populations marked by deformed and highly coalesced vesicles with thin walls. Gray pumice exhibits lower crystallinity (29-36 wt%), abundant broken and/or resorbed crystals, ubiquitous groundmass phenocryst fragments and microlites, the widest range of glass compositions (69-78 wt% SiO2), and quite homogeneous poorly deformed and coalesced vesicles with thicker walls. Mingled pumices are characterized by the alternation of bands or patches with white and gray pumice compositional and textural characteristics. We attribute heterogeneities in glass compositions and crystal and vesicle textures to processes occurring within volcanic conduits as magma is ascending to the surface. In particular, the above observations and results are consistent with an origin of a gray magma by heating of the original white magma in a strongly sheared region of the conduit because of a mechanism of viscous dissipation and crystal grinding and resorption at the conduit walls. The less viscous gray magma, therefore, would enable the onset and preservation of a high mass flux of the eruption otherwise difficult to explain for highly viscous crystal-rich dacitic magmas.

The viscous dissipation within boundary layers of high speed vehicle creates high skin temperatures. Designing of an appropriate thermal protection system requires computation of thermal loads which would be experienced by vehicle during its flight trajectory. The objective of the present work is to develop a methodology for transient aerothermal analysis of high speed vehicle. The most appropriate method for predicting aerodynamic heating is computational fluid dynamics solution (CFD). Solid-Fluid coupling and transient boundary condition capabilities of CFD software FLUENT are used to develop required methodology. The available X-15 flight data is used for its validation. Temperature transients are calculated for complete flight trajectory of X-15 at wing mid-span chord location and compared with available flight data at stagnation, 4%, 20%, and 46% chord locations. The results obtained for skin temperatures at different locations are found both qualitatively and quantitatively in good agreement with in-flight data. This validates the methodology utilized in modeling the transient aero-thermal analysis of high speed vehicles. This method could be very useful in predicting the aerodynamic heating loads of high speed vehicles.

A programme of research is outlined which considers the foaming performance and foam behaviour of surfactant systems commonly encountered in hand-wash laundry detergent applications. An experimental study of the physical chemistry of foam generation indicates that precipitation of a typical anionic surfactant with calcium forms mesophase particles and causes a marked reduction in the rate of transport of surfactant to air–water surfaces and a concomitant reduction in foaming. Oily soil antifoam effects are however insensitive to the presence of calcium, being equally effective regardless of pH and calcium content. They may be reproduced by a simple particle–oil mixture of a saturated and an unsaturated triglyceride (e.g. tristearin and triolein respectively). A detailed foam rheometry study is performed using foam flowing through a constriction. Bubble shapes are used to deduce the normal and shear stresses across the foam flow field. Broad agreement between the experimental stress field and that obtained from quasistatic simulations is demonstrated. As foam flow-rate increases, a different model, which takes explicit account of viscous dissipative forces within the foam flow field is required. The dissipative foam flow model predicts differential shrinkage and stretch rates of foam films. Coupled to a model for surfactant transport, this shows the extent to which surfactant concentration accumulates in shrinking films and is depleted in stretching films. In addition to film stretching, it is also important to know about film bursting or failure rates. Here failure rates are estimated using capillary suction pressures exerted on the films by Plateau border channels around film edges. The failure rates can then be employed to predict the evolution of bubble size at various spatial locations in a foam: reasonable agreement with experimental bubble size distributions is obtained.