Academic literature on the topic 'Dimensionless profile functions'
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Journal articles on the topic "Dimensionless profile functions"
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Paul, Ashish, and Rudra Kanta Deka. "Chemical Reaction Effect on Transient Free Convective Flow past an Infinite Moving Vertical Cylinder." International Journal of Chemical Engineering 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/531513.
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An analysis is performed to study the heat and mass transfer on the flow past an infinite moving vertical cylinder, in the presence of first-order chemical reaction. The closed-form solutions of the dimensionless governing partial differential equations are obtained in terms of Bessel's functions and modified Bessel's functions by the Laplace transform technique. The transient velocity profiles, temperature profiles, and concentration profiles are studied for various sets of physical parameters, namely, the chemical reaction parameter, Prandtl number, Schmidt number, thermal Grashof number, mass Grashof number, and time. The skin friction, Nusselt number, and Sherwood number are also obtained and presented in graphs. It is observed that in presence of as well as increase in chemical reaction the flow velocity decreases. Also, in presence of destructive chemical reaction the concentration profile and Sherwood number tend to the steady state at large time.
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Maynes, D., and B. W. Webb. "Fully-Developed Thermal Transport in Combined Pressure and Electro-Osmotically Driven Flow in Microchannels." Journal of Heat Transfer 125, no. 5 (2003): 889–95. http://dx.doi.org/10.1115/1.1597624.
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Thermally fully-developed heat transfer has been analyzed for combined electro-osmotic and pressure driven flow in a circular microtube. The two classical thermal boundary conditions of constant wall heat flux and constant wall temperature were considered. Such a flow is established by the combination of an imposed pressure gradient and voltage potential gradient along the length of the tube. The induced flow rate and velocity profile are functions of the imposed potential gradient, electro-osmotic mobility of the fluid, the ratio of the duct radius to the Debye length, the established streamwise pressure gradient, and the fluid viscosity. The imposed voltage gradient results in Joule heating in the fluid, with an associated distributed volumetric source of energy. For this scenario, the solution for the fully developed, dimensionless temperature profile and corresponding Nusselt number have been determined. The fully-developed Nusselt number is found to depend on the duct radius/Debye length ratio (termed the relative duct radius), the dimensionless volumetric source, and a dimensionless parameter that characterizes the relative strengths of the two driving mechanisms. This parameter can take on both positive and negative values, depending on the signs of the streamwise voltage and pressure gradients imposed. Analytical results are presented and discussed for a range of the governing dimensionless parameters.
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Tong, Shih-Hsi, and Daniel C. H. Yang. "Rotor Profiles Synthesis for Lobe Pumps With Given Flow Rate Functions." Journal of Mechanical Design 127, no. 2 (2005): 287–94. http://dx.doi.org/10.1115/1.1798271.
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In this paper we present a complete synthesis procedure for lobe pumps with required flow rate functions. A dimensionless flow rate expression, called the “specific flow rate,” is used for our pump synthesis. This specific flow rate depends only on the pitch and deviation functions of the pump rotor, and it is independent of the individual pump size, neither pumping frequency. Another important design parameter used is the “lobe noncircularity,” which is defined as the ratio of the lobe length to the rotor center distance. It is found that the lobe noncircularity is linearly dependent on the ratio of maximum to minimum flow rate regardless of the type of flow rate function. As a result, our synthesis procedure can be simplified as (1) select a type of desirable flow rate function, (2) from the flow rate function derive the corresponding deviation function, (3) based on the deviation function generate the desired rotor profile, and (4) calculate the real pump size. Another advantage is that by using this method wide classes of lobe pumps can be designed. A detailed design example is presented for illustration. In addition, new lobe profiles are invented based on some typical flow rate functions.
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Poonia, Hemant, and R. C. Chaudhary. "MHD free convection and mass transfer flow over an infinite vertical porous plate with viscous dissipation." Theoretical and Applied Mechanics 37, no. 4 (2010): 263–87. http://dx.doi.org/10.2298/tam1004263p.
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An unsteady, two-dimensional, hydromagnetic, laminar mixed convective boundary layer flow of an incompressible and electrically-conducting fluid along an infinite vertical plate embedded in the porous medium with heat and mass transfer is analyzed, by taking into account the effect of viscous dissipation. The dimensionless governing equations for this investigation are solved analytically using two-term harmonic and non-harmonic functions. Numerical evaluation of the analytical results is performed and graphical results for velocity, temperature and concentration profiles within the boundary layer are discussed. The results show that increased cooling (Gr > 0) of the plate and the Eckert number leads to a rise in the velocity profile. Also, an increase in Eckert number leads to an increase in the temperature. Effects of Sc on velocity and concentration are discussed and shown graphically.
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Hersbach, Hans. "Sea Surface Roughness and Drag Coefficient as Functions of Neutral Wind Speed." Journal of Physical Oceanography 41, no. 1 (2011): 247–51. http://dx.doi.org/10.1175/2010jpo4567.1.
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Abstract Near the surface, it is commonly believed that the behavior of the (turbulent) atmospheric flow can be well described by a constant stress layer. In the case of a neutrally stratified surface layer, this leads to the well-known logarithmic wind profile that determines the relation between near-surface wind speed and magnitude of stress. The profile is set by a surface roughness length, which, over the ocean surface, is not constant; rather, it depends on the underlying (ocean wave) sea state. For instance, at the European Centre for Medium-Range Weather Forecasts this relation is parameterized in terms of surface stress itself, where the scale is set by kinematic viscosity for light wind and a Charnock parameter for strong wind. For given wind speed at a given height, the determination of the relation between surface wind and stress (expressed by a drag coefficient) leads to an implicit equation that is to be solved in an iterative way. In this paper a fit is presented that directly expresses the neutral drag coefficient and surface roughness in terms of wind speed without the need for iteration. Since the fit is formulated in purely dimensionless quantities, it is able to produce accurate results over the entire range in wind speed, level height, and values for the Charnock parameter for which the implicit set of equations is believed to be valid.
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Bhansali, A. P., and W. Z. Black. "Local, Instantaneous Heat Transfer Coefficients for Jet Impingement on a Phase Change Surface." Journal of Heat Transfer 118, no. 2 (1996): 334–42. http://dx.doi.org/10.1115/1.2825849.
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The local variation in the heat transfer coefficient for an axisymmetric, turbulent, submerged liquid jet impinging on a nonuniform boundary of a phase-change material is measured with an ultrasonic measurement technique. The time required for an acoustic wave to traverse the phase-change material is measured with an ultrasonic transducer and the time data are converted into local thickness profiles of the phase-change material via knowledge of the longitudinal acoustic velocity in the material. An energy balance at the melt interface between the impinging jet and the phase-change material is used in conjunction with the local thickness profile data to determine the local variation in the heat transfer coefficient. The phase-change material is originally flat, but its shape changes with time as the heated jet melts a complex shape into its surface. The heat transfer rate over the surface of the melting interface is shown to vary with time as a result of the changing shape of the phase change material. A deep cavity is melted into the solid at the stagnation point and secondary cavities are melted into the interface for certain jet flow rates and surface spacings between the jet nozzle and the melt interface. When secondary cavities are produced, secondary peaks in the local heat transfer coefficient are observed. The heat transfer data are formulated into two Nusselt number correlations that are functions of the dimensionless time, dimensionless radius, dimensionless jet-to-surface spacing, and jet Reynolds number. One correlation is formulated for all locations along the surface of the phase-change material except the stagnation point, and a second correlation is valid at the stagnation point.
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Sahoo, Goloka Behari, and David Luketina. "Bubbler design for reservoir destratification." Marine and Freshwater Research 54, no. 3 (2003): 271. http://dx.doi.org/10.1071/mf02045.
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Two important bubbler-performance criteria, the mechanical efficiency, ηmech, and the destratification time, Γ, were analysed as functions of two dimensionless parameters, G, the strength of stratification, and M, the source strength. Equations to estimate the optimum airflow rate (via M) and corresponding ηmech and Γ for a known linear stratification G in a reservoir were derived. Owing to difficulties in accurately determining the actual G, it was demonstrated that it is appropriate practice to reduce the design G value by around 10%. It was shown that the equivalent linear stratification method might lead to sub-optimal design for stratification profiles that deviate substantially from a linear profile. Rather, a bubble-plume model should be applied. Finally, the effects of incorporating changes in bubble radius in a bubble-plume model were examined. ηmech and Γ were found to be relatively insensitive to bubble radius; however, the ideal bubble size for maintaining a suitable oxygen dissolution efficiency is 1 mm.
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ROMANO, ANTONIO ENEA. "INHOMOGENEOUS COSMOLOGICAL MODELS AND H0 OBSERVATIONS." International Journal of Modern Physics D 21, no. 12 (2012): 1250085. http://dx.doi.org/10.1142/s021827181250085x.
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We address some recent erroneous claim that H0 observations are difficult to accommodate with LTB cosmological models, showing how to construct solutions in agreement with an arbitrary value of H0 by rewriting the exact solution in terms of dimensionless parameters and functions. This approach can be applied to fully exploit LTB solutions in designing models alternative to dark energy without making any restrictive or implicit assumption about the inhomogeneity profile. The same solution can also be used to study structure formation in the regime in which perturbation theory is not enough and an exact solution of the Einstein's equation is required, or to estimate the effects of a local inhomogeneities on the apparent equation of state of dark energy.
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Mirbahar, Muhammad Nawaz, Kashif Ali Abro, and Abdul Wasim Shaikh. "Calorimetric Investigation for Thermal Plate of Casson Fluid via Fractional Derivative." Journal of Nanofluids 8, no. 8 (2019): 1668–75. http://dx.doi.org/10.1166/jon.2019.1720.
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The manuscript reveals the collective effects of the moving plate of Casson fluid in which magnetic, porous outcomes are under consideration. Thermal stratification is investigated to disclose the hidden phenomenon of mass concentration and temperature distribution. Fractional operator has been applied on the fundamental equations of Casson fluid namely Caputo-Fabrizio fractional operator based on sufficient memory operator. For the exact analysis of basic fractional governing equations of velocity profile, temperature distribution and mass concentration the integral transforms have been employed. The solutions of the dimensionless equations have been described in terms special functions in convoluted form. For the sake of non-fractional solution of the basic equations of the Casson fluid X = 1 in the obtained solutions has been implemented for the four type's fluid models. Finally, thermal conductivity of the fluid has been analyzed by estimating various different parametric values which result the increment in velocity profile along with porous permeability but reverse in transvers magnetic field on the flow.
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Kakac, S., W. Li, and R. M. Cotta. "Unsteady Laminar Forced Convection in Ducts With Periodic Variation of Inlet Temperature." Journal of Heat Transfer 112, no. 4 (1990): 913–20. http://dx.doi.org/10.1115/1.2910499.
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A theoretical and experimental study of laminar forced convection in the thermal entrance region of a rectangular duct, subjected to a sinusoidally varying inlet temperature, is presented. A general boundary condition of the fifth kind that accounts for both external convection and wall thermal capacitance effects is considered, and an analytical solution is obtained through extending the generalized integral transform technique. The variations of amplitudes and phase lags of centerline and bulk temperatures are determined as functions of modified Biot number, fluid-to-wall thermal capacitance ratio, and dimensionless inlet frequency. An apparatus has been designed, built, and used for the experimental study to provide validation of the mathematical modeling employed. Good agreement is obtained when the nonuniform sinusoidally varying inlet temperature profile obtained by experiments is incorporated into the theoretical model.
Dissertations / Theses on the topic "Dimensionless profile functions"
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Lindgren, Kristina. "The Behaviour of the Latent Heat Exchange Coefficient in the Stable Marine Boundary Layer." Thesis, Uppsala University, Department of Earth Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9140.
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<p>Knowledge of the turbulent fluxes at the sea surface is important for understanding the interaction between atmosphere and ocean. With better knowledge, improvements in the estimation of the heat exchange coefficients can be made and hence models are able to predict the weather and future climate with higher accuracy.</p><p>The exchange coefficients of latent and sensible heat during stable stratification vary in the literature. Therefore it is necessary to investigate the processes influencing the air-sea exchange of water vapour and heat in order to estimate these values. With measurements from a tower and a directional waverider buoy at the site Östergarnsholm in the Baltic Sea, data used in this study have been sampled from the years 2005-2007. This site represents open-ocean conditions during most situations when the wind comes from the south-east sector. The neutral exchange coefficients, CEN and CHN, have been calculated along with the non-dimensional profile functions for temperature and wind to study the dependence of stability and other parameters of relevance.</p><p>It was found that CEN increased slightly with wind speed and reached a mean value of approximately 1.45×10-3. The highest values of CEN were observed during near neutral conditions and low wave ages. CHN attained a mean value of approximately 0.77×10-3 and did not show any relation to wind speed or to wave age. No significant dependence with wind or wave direction could be shown for either CEN or CHN in the sector 80-220°. The stability correction, performed to reduce the dependence on stratification for CEN and CHN, was well performed for stabilities higher than 0.15. The stability is represented by a relationship between the height and the Obukhov-length (z/L).</p><p>Validity of the non-dimensional profile functions for temperature and wind showed that, for smaller stabilities, these functions gave higher values than the corresponding functions recommended by Högström (1996). The profile funtions for temperature was shown to have a larger scatter while the profile functions for wind was less scattered and deviated more from the functions given by Högström</p><br><p>Kunskap om turbulenta flöden i det marina gränsskiktet är viktigt för att förstå växelverkan mellan atmosfär och hav. Med bättre kunskap kan förbättringar i bestämningen av utbyteskoefficienterna för latent och sensibelt värme erhållas. Det medför att modeller kan prognostisera väder och framtida klimat med högre noggrannhet.</p><p>Utbyteskoefficienterna för latent och sensibelt värme har för stabil skiktning olika värden i litteraturen. Detta gör det nödvändigt att undersöka de processer som påverkar utbytet av vattenånga och värme mellan luft och hav för att kunna bestämma dessa värden. Data som har använts i den här studien insamlades mellan år 2005 och 2007 från en boj och ett torn vid mätplatsen Östergarnsholm i Baltiska havet. För det flesta situationer, när vinden blåser från syd-ost, representerar mätplatsen ett förhållande likvärdigt det över öppet hav. De neutrala utbyteskoefficienterna, CEN och CHN, och de dimensionslösa profilfunktionera för temperatur och vind, och , har beräknats för att studera beroendet av stabilitet samt andra relevanta parametrar.</p><p>Beräkningarna visade att CEN ökade något med vindhastighet och hamnade på ett medelvärde av ungefär 1.45×10-3. De högsta värdena på CEN observerades vid nära neutrala förhållanden och låga vågåldrar. CHN uppmättes till att ha ett medelvärde på ungefär 0.77×10-3 och uppvisade inget beroende med vindhastighet eller vågålder. Inget märkbart beroende med vind- eller vågriktning kunde visas för CEN eller CHN i sektorn 80-220°. Stabilitetskorrektionen, utförd för att reducera beroendet av atmosfärens skiktning för CEN och CHN, var bra för stabiliteter högre än 0.15. Stabiliteten representeras av förhållandet mellan höjden och Obukhov-längden (z/L).</p><p>Utvärdering av de dimensionslösa funktionerna för temperatur och vind visade att dessa funktioner, för små stabiliteter, gav högre värden än motsvarande funktioner som rekommenderas av Högström (1996). Värdena på profilfunktionerna för temperatur hade större spridning än värdena på profilfunktionerna för vind och avvek mer från funktionerna givna av Högström.</p>
Book chapters on the topic "Dimensionless profile functions"
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Jan, Chyan-Deng. "Normal-Depth-Based Dimensionless GVF Solutions Using the Gaussian Hypergeometric Function." In Gradually-varied Flow Profiles in Open Channels. Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-35242-3_3.
Full textConference papers on the topic "Dimensionless profile functions"
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Jiménez, Edson M., Juan P. Escandón, and Oscar E. Bautista. "Study of the Transient Electroosmotic Flow of Maxwell Fluids in Square Cross-Section Microchannels." In ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/icnmm2015-48547.
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Several kinds of fluids with non-Newtonian behavior are manipulated in microfluidic devices for medical, chemical and biological applications. This work presents an analytical solution for the transient electroosmotic flow of Maxwell fluids in square cross-section microchannels. The appropriate combination of the momentum equation with the rheological Maxwell model derives in a mathematical model based in a hyperbolic partial differential equation, that permits to determine the velocity profile. The flow field is solved using the Green’s functions for the steady-state regime, and the method of separation of variables for the transient phenomenon in the electroosmotic flow. Taking in to account the normalized form of the governing equations, we predict the influence of the main dimensionless parameters on the velocity profiles. The results show an oscillatory behavior in the transient stage of the fluid flow, which is directly controlled by the dimensionless relaxation time, this parameter is an indicator of the competition between elastic and viscous effects. Hence, this investigation about the characteristics of the fluid rheology on the fluid velocity of the transient electroosmotic flow are discussed in order to contribute to the understanding the different tasks and design of microfluidic devices.
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Escandón, Juan P., Eduardo G. Merino, and Clara G. Hernández. "Transient Electroosmotic Flow of Newtonian Fluids in a Microchannel With Heterogeneous Zeta Potentials at the Walls." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65939.
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This paper presents an analytical study of the transient electroosmotic flow for Newtonian fluids through a parallel flat plate microchannel with heterogeneous zeta potentials. The dimensionless mathematical model is based on the Poisson-Boltzmann, mass and momentum conservation governing equations together with the lubrication theory. The distribution of the zeta potentials at the walls obeys to a sinusoidal function, which includes dimensional parameters as Δζ that controls the magnitude and polarity of the zeta potentials, being capable to produce slanted velocity profiles and inverse flows. On the other hand, the combination of the phase angle between the sinusoidal functions of the zeta potentials ω, the dimensionless parameter of their amplitude Δζ, and the parameter that controls the frequency of the sinusoidal functions m, induce additional perturbations on the flow, which is directly related to the dimensionless pressure distribution and to the transient flow field. The transient behavior characteristics of the electroosmotic flow are discussed in terms of the zeta potential variations. It is demonstrated that the results for the transient electroosmotic flow, predict the influence of the main dimensionless parameters above mentioned on the velocity profiles and the streamlines. This work about the perturbations on the electroosmotic flow by heterogeneous zeta potentials, contributes to a better understanding of the transport phenomena in microfluidic devices for future mixing applications.
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Lee, Hyesoo, Youngho Jang, Woodong Jung, and Wonmo Sung. "CO2 Plume Migration With Gravitational, Viscous, and Capillary Forces in Saline Aquifers." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54123.
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In this study, we attempt to consider three forces of gravitational, viscous and capillary forces, simultaneously when CO2 is injected in saline aquifers. In order to conduct it, we propose a dimensionless group in the form of combination of Capillary number and Bond number. This dimensionless group is a function of CO2 saturation, in which the pattern of CO2 flow regimes can be determined. By the analysis of the acquired each trapping mechanism from flow regimes, optimum CO2 injecting scheme can be designed for maximizing the solubility and residual trappings as stable mechanism. With utilizing the proposed dimensionless group, we conducted several numbers of simulations using 2D vertical heterogeneous system with respect to CO2 flow rate, interfacial tension between CO2 and water, and brine salinity. From the simulation results, when gravitational and viscous forces with respect to capillary force are described by two individual dimensionless groups of Capillary number and Bond number, CO2 saturation profiles are variously generated. These are not satisfactory correlations in the dependence of CO2 saturation on Capillary number and Bond number for the variable terms of density differences between CO2 and water and CO2 injection rates. With the proposed dimensionless group, the universal profile of CO2 saturation was obtained in describing CO2 flow behaviors for the variables. Thus, considering two variables of density differences and CO2 injection rates simultaneously, that is, when three forces considering at the same time, more realistic CO2 flow behavior can be analyzed. This study helps to determine the most secure conditions of CO2 injection and storage according to building the pattern of CO2 flow regimes which is classified by the range of a dimensionless group.
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Carranza, Richard G. "A Dynamic Heat Transfer Analysis of a Three Sided Pyramidal Fin of Scalene Triangular Cross-Sectional Area." In ASME 2008 Heat Transfer Summer Conference collocated with the Fluids Engineering, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/ht2008-56011.
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A dynamic analysis is performed on a three sided pyramidal fin of scalene triangular cross-sectional area (from here on referred to as a TSPSCA). Finite differences are used to solve the governing equation and produce a temperature profile throughout the TSPSCA as a function of time. Dimensionless variables are used. The characteristics of the temperature profile throughout the TSPSCA as a function of time are dependent upon a dimensionless parameter: the thermal conductance due to convection per the thermal conductance due to conduction. It is assumed that the temperature of the fin is homogenous and equal to the temperature of the convecting fluid at time equal zero. The results show that when the conductance ratio is high, the fin temperature profile reaches steady-state quickly; and that the temperatures through the fin deviate greatly from the fin base. Conversely, as this ratio falls in magnitude, the temperature throughout the fin at steady-state approaches the temperature of the fin base; and is slower to reach steady-state.
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Yan, Jia, Daniel C. H. Yang, and Shih-Hsi Tong. "On the Generation of Analytical Noncircular Multi-Lobe Internal Pitch Pairs." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-34017.
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A method for the design of general analytical noncircular multi-lobe internal pitch pairs is presented. The method is based on a reshaping algorithm. A selected monotonic function can be assigned as the initial profile for the outer rotor of the designed pitch pair. This initial function will then be reshaped to satisfy that the number of lobes must be an integer. This final pitch function can then be obtained analytically. To archive smooth profile design, the C1 continuous conditions on pitch rotors are established. A dimensionless parameter geometrically interpreted as the noncircularity of pitch rotor is introduced for the systematic design of pitch pairs. Results from this research have applications to the design of noncircular gears.
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Ladino, Alexander. "Numerical Study of Cavitation Characteristics of Profiles for Use in Marine Current Turbines." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62526.
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Kinetic energy in the oceans offers an important and promising source of renewable energy which can be exploited by marine current turbines (MCT). One of the key issues related with design of MCT’s is the cavitation inception along turbine blades. Cavitation occurrence in MCT’s blades generates erosion and poor power performance with similar effect in the hydraulic turbine case. In this work, a numerical investigation using the vorticity–stream function code XFOIL in order to study cavitation characteristics in NACA 4 series profiles was performed. The study was developed systematically starting from NACA 4415 profiles and varying independently camber percentage, camber position and thickness. Other study carried out was the effect of trailing edge deflection in the cavitation bucket. Results show a symmetrical increment in cavitation free zone for profiles with increasing thickness. Also for camber increment, the cavitation free zone is incremented, especially at high angles of attack. For variation of camber percentage, increasing camber produces the cavitation bucket moves to high lift zone which suggest that the profile could cavitate at low and negative Cl in wide range of cavitation numbers. Finally the effect of trailing edge deflection produces a slight increment in cavitation free zone which is similar to the effect of camber increment. Also, the trailing edge deflection shows that a same Cl can be achieved with lower angle of attack and lower pressure coefficient compared with the standard profile, constituting a desired behavior from the cavitation point of view. Finally, local dimensionless correlations were developed which can be used for parametric studies of cavitation performance of MCT’s in the design stage.
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Issa, Johnny, and Alfonso Ortega. "The Skin Friction and Heat Transfer in a Laminar Plane Wall Jet That Evolves From a Uniform Velocity to Its Self-Similar Behavior." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72034.
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The plane, steady, laminar wall jet with a uniform velocity and temperature profiles at the jet exit is numerically investigated using a two-dimensional finite volume approach for a variety of Reynolds numbers and Prandtl number of 0.712 and 7. Between the jet exit and the downstream self-similar behavior, the flow exhibits a developing region that is not self-similar. The location of the dimensionless virtual origin is carefully investigated and expressed as a function of Reynolds number. The local skin friction coefficient is observed to converge to the analytical self-similar solution at downstream locations. Since no analytical solution exists for the temperature field in either the developing or self-similar regions of this problem, the thermal solution is investigated for both isothermal and isoflux boundary conditions at the wall. The local and overall skin friction coefficients, in addition to the local and overall Nusselt numbers, are reported as a function of Reynolds number, Prandtl number and the dimensionless location downstream of the jet exit.
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Issa, Johnny, and Alfonso Ortega. "A Numercial Investigation of the Skin Friction Coefficient and Nusselt Number in a Laminar Wall Jet That Evolves From a Parabolic Velocity Profile to its Self-Similar Behavior." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21264.
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A finite volume numerical approach is used to study the steady, laminar, plane wall jet that evolves from a parabolic velocity profile with uniform temperature to its self-similar behavior downstream of the jet exit. A variety of Reynolds numbers ranging between 50 and 250 is considered in this numerical investigation. The working fluids are air and water with constant physical properties corresponding to Prandtl number of 0.712 and 7 at ambient conditions. In these types of flows, a developing region over which the flow converges to its self-similar behavior is observed in the vicinity of the jet exit. The location of the dimensionless virtual origin, which is of main importance in determining the flow field in the self-similar region, is carefully studied and correlated as a function of Reynolds number. The local skin friction coefficient is observed to converge to the analytical self-similar solution at downstream locations. Given that an analytical solution for the thermal behavior of this problem doesn’t exist in either the developing or self-similar regions, the thermal solution of this problem is studied for isothermal and uniform heat flux boundary conditions at the wall. The idea of a dimensionless thermal virtual origin is introduced and correlated as a function of Reynolds number. The Nusselt number dependence on Prandtl number, Reynolds number and the downstream location are obtained for both thermal boundary conditions at the wall.
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Li, Zhihua, Jane H. Davidson, and Susan C. Mantell. "Heat Transfer Enhancement Using Shaped Polymer Tubes: Fin Analysis." In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47214.
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Uniquely shaped tubes extruded with an inner circular flow passage and an outer streamlined profile are proposed to withstand the inside fluid pressure and simultaneously to reduce the pressure drop across heat exchanger tube bundles comprising hundreds of small-diameter, thin-walled polymer tubes. Heat transfer rates are characterized by treating the tubes as the combination of a base circular tube and longitudinal fin(s) of oval or lenticular profile. Numerical solution of the non-linear differential equation for surface temperature provides the shaped tube efficiency, similar in function to fin efficiency. The effects of Biot number and a dimensionless shape factor on the tube efficiency and the convective heat transfer rate are discussed. A comparison of a circular to an oval shaped tube indicates that convective heat transfer is enhanced for 2000 ≤ Re ≤ 20,000 when Bi < 0.3.
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Abbasi, K., M. Del Valle, A. P. Wemhoff, and A. Ortega. "A Transient Model for Parallel Flow and Counter Flow Heat Exchangers." In ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73118.
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The transient and steady-state response of single pass constant-flow (concentric parallel flow, concentric counter flow) heat exchangers was investigated using a finite volume method. Heat exchanger transients initiated by both step-change and sinusoidally varying hot stream inlet temperatures were investigated. The wall separating the fluid streams was modeled by conduction with thermal mass; hence the heat exchanger transient behavior is dependent on the thermal mass of the fluid streams as well as the internal wall. The outer wall is approximated as fully insulating. The time dependent temperature profiles were investigated as a function of heat exchanger dimensionless length and dimensionless time for both fluids. It was found that the transient response of the heat exchanger is controlled by a combination of the residence time and thermal capacitance of the fluid streams, the overall heat transfer coefficient between the fluid streams, and the thermal capacitance of the internal wall.