Hamiltonian formulation of inviscid flows with free boundaries
International Nuclear Information System (INIS)
Abarbanel, H.D.I.; Brown, R.; Yang, Y.M.
1988-01-01
The formulation of the Hamiltonian structures for inviscid fluid flows with material free surfaces is presented in both the Lagrangian specification, where the fundamental Poisson brackets are canonical, and in the Eulerian specification, where the dynamics is given in noncanonical form. The noncanonical Eulerian brackets are derived explicitly from the canonical Lagrangian brackets. The Eulerian brackets are, with the exception of a single term at each material free surface separating flows in different phases, identical to those for isentropic flow of a compressible, inviscid fluid. The dynamics of the free surface is located in the Hamiltonian and in the definition of the Eulerian variables of mass density, rho(x, t), momentum density, M(x,t) [which is rho times the fluid velocity v(x,t)], and the specific entropy, σ(x,t). The boundary conditions for the Eulerian variables and the evolution equations for the free surfaces come from the Euler equations of the flow. This construction provides a unified treatment of inviscid flows with any number of free surfaces
High speed inviscid compressible flow by the finite element method
Zienkiewicz, O. C.; Loehner, R.; Morgan, K.
1984-01-01
The finite element method and an explicit time stepping algorithm which is based on Taylor-Galerkin schemes with an appropriate artificial viscosity is combined with an automatic mesh refinement process which is designed to produce accurate steady state solutions to problems of inviscid compressible flow in two dimensions. The results of two test problems are included which demonstrate the excellent performance characteristics of the proposed procedures.
General stability criterion for inviscid parallel flow
International Nuclear Information System (INIS)
Sun Liang
2007-01-01
Arnol'd's second stability theorem is approached from an elementary point of view. First, a sufficient criterion for stability is found analytically as either -μ 1 s ) s ) in the flow, where U s is the velocity at the inflection point, and μ 1 is the eigenvalue of Poincare's problem. Second, this criterion is generalized to barotropic geophysical flows in the β plane. And the connections between present criteria and Arnol'd's nonlinear criteria are also discussed. The proofs are completely elementary and so could be used to teach undergraduate students
Numerical solution of inviscid and viscous flow around the profile
Slouka, Martin; Kozel, Karel; Prihoda, Jaromir
2015-05-01
This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox's k-ω model. Calculations are done in GAMM channel computational domain with 10% DCA profile and in turbine cascade computational domain with 8% DCA profile. Numerical methods are based on a finite volume solution and compared with experimental measurements for 8% DCA profile.
Numerical solution of inviscid and viscous flow around the profile
Directory of Open Access Journals (Sweden)
Slouka Martin
2015-01-01
Full Text Available This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox’s k-ω model. Calculations are done in GAMM channel computational domain with 10% DCA profile and in turbine cascade computational domain with 8% DCA profile. Numerical methods are based on a finite volume solution and compared with experimental measurements for 8% DCA profile.
Development of an inviscid flux scheme for thermochemical nonequilibrium flow
Campbell, Charles Hugh
Solutions to the governing equations that model hypersonic aerothermodynamics rely heavily on the mathematical and numerical technology that characterizes Computational Fluid Dynamics. Many areas of significant investigation are relevant to advancing state of the art hypersonic aerothermodynamic engineering and applied research analyses. Due to the relatively high energy achieved by spacecraft during launch, physical models for thermal nonequilibrium and chemical nonequilibrium are necessary to develop adequate numerical reentry simulations. In addition, complex features of the Navier Stokes equations require sophisticated mathematical and numerical techniques in order to develop reasonably accurate simulations in an acceptable amount of time. The objective of this work is to present the development of a new inviscid flux evaluation method. This new method, referred to as the Flux Consistent scheme, is closely related to the Modified Steger-Warming method. The unique characteristics of this new flux scheme involve an original eigenvalue implementation. This original eigenvalue formulation, however, leads to incorrect flux magnitudes which must be corrected in the total flux to provide an accurate representation of the inviscid fluxes. The mathematical technique used to identify flux magnitude errors in the Flux Consistent scheme is also applied to the Modified Steger-Warming flux evaluation method. This assessment leads to the characterization of flux errors in the Modified Steger-Warming scheme which are generated by eigenvalue differences between the left and right cell interface flow states. These Modified Steger-Warming flux errors are shown to vanish for supersonic conditions. Two hypotheses in reference to the Modified Steger-Warming scheme are proposed. The first is that sonic glitch problems occurring in some Steger-Warming simulations are the result of the flux error vanishing at supersonic conditions. The second hypothesis concerning the Steger
A numerical simulation of the inviscid flow through a counter-rotating propeller
Celestina, M. L.; Mulac, R. A.; Adamczyk, J. H.
1986-01-01
The results of a numerical simulation of the time-averaged inviscid flow field through the blade rows of a multiblade row turboprop configuration are presented. The governing equations are outlined along with a discussion of the solution procedure and coding strategy. Numerical results obtained from a simulation of the flow field through a modern high-speed turboprop will be shown.
A numerical simulation of the inviscid flow through a counterrotating propeller
Celestina, M. L.; Mulac, R. A.; Adamczyk, J. J.
1986-01-01
The results of a numerical simulation of the time-averaged inviscid flow field through the blade rows of a multiblade row turboprop configuration are presented. The governing equations are outlined along with a discussion of the solution procedure and coding strategy. Numerical results obtained from a simulation of the flow field through a modern high-speed turboprop will be shown.
Numerical solution of inviscid transonic flow through 3D axial blade row
Energy Technology Data Exchange (ETDEWEB)
Fort, J.; Fuerst, J.; Halama, J.; Kozel, K. [CTU Prague (Czech Republic). Dept. of Technical Mathematics
2000-07-01
Presented paper deals with numerical solution of 3D inviscid transonic flow through axial cascades. Two different finite volume methods are mentioned. Authors show a comparison of both methods using results computed for the stator and the rotor cascades. A role of inlet parameters and body forces in the case of a rotor flow has been also investigated. (orig.)
Sturdza, Peter (Inventor); Martins-Rivas, Herve (Inventor); Suzuki, Yoshifumi (Inventor)
2014-01-01
A fluid-flow simulation over a computer-generated surface is generated using a quasi-simultaneous technique. The simulation includes a fluid-flow mesh of inviscid and boundary-layer fluid cells. An initial fluid property for an inviscid fluid cell is determined using an inviscid fluid simulation that does not simulate fluid viscous effects. An initial boundary-layer fluid property a boundary-layer fluid cell is determined using the initial fluid property and a viscous fluid simulation that simulates fluid viscous effects. An updated boundary-layer fluid property is determined for the boundary-layer fluid cell using the initial fluid property, initial boundary-layer fluid property, and an interaction law. The interaction law approximates the inviscid fluid simulation using a matrix of aerodynamic influence coefficients computed using a two-dimensional surface panel technique and a fluid-property vector. An updated fluid property is determined for the inviscid fluid cell using the updated boundary-layer fluid property.
Numerical solution of inviscid and viscous laminar and turbulent flow around the airfoil
Directory of Open Access Journals (Sweden)
Slouka Martin
2016-01-01
Full Text Available This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox k-omega model. Calculations are done for NACA 0012 and RAE 2822 airfoil profile for the different angles of upstream flow. Numerical results are compared and discussed with experimental data.
Numerical solution of inviscid and viscous laminar and turbulent flow around the airfoil
Slouka, Martin; Kozel, Karel
2016-03-01
This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox k-omega model. Calculations are done for NACA 0012 and RAE 2822 airfoil profile for the different angles of upstream flow. Numerical results are compared and discussed with experimental data.
Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)
2013-01-01
Fluid-flow simulation over a computer-generated aircraft surface is generated using inviscid and viscous simulations. A fluid-flow mesh of fluid cells is obtained. At least one inviscid fluid property for the fluid cells is determined using an inviscid fluid simulation that does not simulate fluid viscous effects. A set of intersecting fluid cells that intersects the aircraft surface are identified. One surface mesh polygon of the surface mesh is identified for each intersecting fluid cell. A boundary-layer prediction point for each identified surface mesh polygon is determined. At least one boundary-layer fluid property for each boundary-layer prediction point is determined using the at least one inviscid fluid property of the corresponding intersecting fluid cell and a boundary-layer simulation that simulates fluid viscous effects. At least one updated fluid property for at least one fluid cell is determined using the at least one boundary-layer fluid property and the inviscid fluid simulation.
Afsar, Mohammed; Sescu, Adrian
2014-11-01
Transition in boundary layer flow over flat/curved surfaces and at moderate to high freestream disturbances or under the influence of various surface roughness elements often involves inviscid secondary instability. This stage in transition can be pictured as being a parametric resonance-type phenomena where a unstable primary flow saturates to a more-or-less steady-state, susceptible to infinitesimal three-dimensional wave-like instability modes that grow much faster than the primary. In decades of research on boundary layers, experimenters have relied upon an inflection point in the wall normal y and/or spanwise directions z of the primary as a pre-cursor to transition. This assertion, based on Rayleigh's theorem, does not however apply in transversely sheared flows. In this talk, we show that an alternative local criterion for inviscid secondary instability - sharing similarities to the original one-dimensional Rayleigh criterion - exists for a class of non-planar transversely sheared flows at long streamwise wavelength. Our general stability criterion is, remarkably, given by necessity of the surface U y , z possessing at least one saddle point in the plane. We analyze this saddle-point criterion numerically show its relevance to secondary instabilities. M.Z.A. would like to anknowledge financial support from Laminar Flow Control (LFC-UK) Research Program at Imperial College London and would like to thank Professor Philip Hall for motivating his interest in this problem.
Schwab, J. R.; Povinelli, L. A.
1984-01-01
A comparison of the secondary flows computed by the viscous Kreskovsky-Briley-McDonald code and the inviscid Denton code with benchmark experimental data for turning duct is presented. The viscous code is a fully parabolized space-marching Navier-Stokes solver while the inviscid code is a time-marching Euler solver. The experimental data were collected by Taylor, Whitelaw, and Yianneskis with a laser Doppler velocimeter system in a 90 deg turning duct of square cross-section. The agreement between the viscous and inviscid computations was generally very good for the streamwise primary velocity and the radial secondary velocity, except at the walls, where slip conditions were specified for the inviscid code. The agreement between both the computations and the experimental data was not as close, especially at the 60.0 deg and 77.5 deg angular positions within the duct. This disagreement was attributed to incomplete modelling of the vortex development near the suction surface.
Enhanced Dissipation, Hypoellipticity, and Anomalous Small Noise Inviscid Limits in Shear Flows
Bedrossian, Jacob; Coti Zelati, Michele
2017-06-01
We analyze the decay and instant regularization properties of the evolution semigroups generated by two-dimensional drift-diffusion equations in which the scalar is advected by a shear flow and dissipated by full or partial diffusion. We consider both the space-periodic T^2 setting and the case of a bounded channel T × [0,1] with no-flux boundary conditions. In the infinite Péclet number limit (diffusivity {ν\\to 0}), our work quantifies the enhanced dissipation effect due to the shear. We also obtain hypoelliptic regularization, showing that solutions are instantly Gevrey regular even with only partial diffusion. The proofs rely on localized spectral gap inequalities and ideas from hypocoercivity with an augmented energy functional with weights replaced by pseudo-differential operators (of a rather simple form). As an application, we study small noise inviscid limits of invariant measures of stochastic perturbations of passive scalars, and show that the classical Freidlin scaling between noise and diffusion can be modified. In particular, although statistically stationary solutions blow up in {H^1} in the limit {ν \\to 0}, we show that viscous invariant measures still converge to a unique inviscid measure.
Relativistic low angular momentum accretion: long time evolution of hydrodynamical inviscid flows
Mach, Patryk; Piróg, Michał; Font, José A.
2018-05-01
We investigate relativistic low angular momentum accretion of inviscid perfect fluid onto a Schwarzschild black hole. The simulations are performed with a general-relativistic, high-resolution (second-order), shock-capturing, hydrodynamical numerical code. We use horizon-penetrating Eddington–Finkelstein coordinates to remove inaccuracies in regions of strong gravity near the black hole horizon and show the expected convergence of the code with the Michel solution and stationary Fishbone–Moncrief toroids. We recover, in the framework of relativistic hydrodynamics, the qualitative behavior known from previous Newtonian studies that used a Bondi background flow in a pseudo-relativistic gravitational potential with a latitude-dependent angular momentum at the outer boundary. Our models exhibit characteristic ‘turbulent’ behavior and the attained accretion rates are lower than those of the Bondi–Michel radial flow. For sufficiently low values of the asymptotic sound speed, geometrically thick tori form in the equatorial plane surrounding the black hole horizon while accretion takes place mainly through the poles.
Numerical simulations of incompressible laminar flows using viscous-inviscid interaction procedures
Shatalov, Alexander V.
The present method is based on Helmholtz velocity decomposition where velocity is written as a sum of irrotational (gradient of a potential) and rotational (correction due to vorticity) components. Substitution of the velocity decomposition into the continuity equation yields an equation for the potential, while substitution into the momentum equations yields equations for the velocity corrections. A continuation approach is used to relate the pressure to the gradient of the potential through a modified Bernoulli's law, which allows the elimination of the pressure variable from the momentum equations. The present work considers steady and unsteady two-dimensional incompressible flows over an infinite cylinder and NACA 0012 airfoil shape. The numerical results are compared against standard methods (stream function-vorticity and SMAC methods) and data available in literature. The results demonstrate that the proposed formulation leads to a good approximation with some possible benefits compared to the available formulations. The method is not restricted to two-dimensional flows and can be used for viscous-inviscid domain decomposition calculations.
International Nuclear Information System (INIS)
Iwayama, T; Sueyoshi, M; Watanabe, T
2013-01-01
The linear stability of parallel shear flows for an inviscid generalized two-dimensional (2D) fluid system, the so-called α turbulence system, is studied. This system is characterized by the relation q = −( − Δ) α/2 ψ between the advected scalar q and the stream function ψ. Here, α is a real number not exceeding 3 and q is referred to as the generalized vorticity. In this study, a sufficient condition for linear stability of parallel shear flows is derived using the conservation of wave activity. A stability analysis is then performed for a sheet vortex that violates the stability condition. The instability of a sheet vortex in the 2D Euler system (α = 2) is referred to as a Kelvin–Helmholtz (KH) instability; such an instability for the generalized 2D fluid system is investigated for 0 3−α for 1 < α < 3, where k is the wavenumber of the perturbation. In contrast, for 0 < α ⩽ 1, the growth rate is infinite. In other words, a transition of the growth rate of the perturbation occurs at α = 1. A physical model for KH instability in the generalized 2D fluid system, which can explain the transition of the growth rate of the perturbation at α = 1, is proposed. (paper)
Parallel Simulation of HGMS of Weakly Magnetic Nanoparticles in Irrotational Flow of Inviscid Fluid
Directory of Open Access Journals (Sweden)
Kanok Hournkumnuard
2014-01-01
Full Text Available The process of high gradient magnetic separation (HGMS using a microferromagnetic wire for capturing weakly magnetic nanoparticles in the irrotational flow of inviscid fluid is simulated by using parallel algorithm developed based on openMP. The two-dimensional problem of particle transport under the influences of magnetic force and fluid flow is considered in an annular domain surrounding the wire with inner radius equal to that of the wire and outer radius equal to various multiples of wire radius. The differential equations governing particle transport are solved numerically as an initial and boundary values problem by using the finite-difference method. Concentration distribution of the particles around the wire is investigated and compared with some previously reported results and shows the good agreement between them. The results show the feasibility of accumulating weakly magnetic nanoparticles in specific regions on the wire surface which is useful for applications in biomedical and environmental works. The speedup of parallel simulation ranges from 1.8 to 21 depending on the number of threads and the domain problem size as well as the number of iterations. With the nature of computing in the application and current multicore technology, it is observed that 4–8 threads are sufficient to obtain the optimized speedup.
Suitable weak solutions: from compressible viscous to incompressible inviscid fluid flows
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Novotný, A.; Petzeltová, Hana
2013-01-01
Roč. 356, č. 2 (2013), s. 683-702 ISSN 0025-5831 R&D Projects: GA ČR GA201/09/0917 Institutional research plan: CEZ:AV0Z10190503 Keywords : relative entropy * incompressible limit * inviscid limit Subject RIV: BA - General Mathematics Impact factor: 1.201, year: 2013 http://link.springer.com/article/10.1007%2Fs00208-012-0862-5
Johnston, W. A.
1983-01-01
A viscous-inviscid interactive calculation procedure is developed for application to flow in cascades of two-dimensional airfoils. This procedure has essentially three components. First, a numerical solution of the Eulers equations which can accommodate an arbitrarily specified cascade geometry of the cascade. A method of grid generation has been used which relics in part on a succession of conformal mappings. Second, a viscous solution for use in boundary layers and wake regions was programmed. Finally, an interactive scheme which takes the form of a source-sink distribution along the blade surface and wake centerline is employed. Results were obtained with this procedure for several cascade flow situations, and some comparisons with experiment are presented.
Clark, R. W.; James, R. M.
1981-01-01
A new approach to the solution of matrix equations resulting from integral equations is presented and applied to the solution of two-dimensional Neumann problems describing the inviscid, incompressible flow past an airfoil. The problem is reformulated in terms of a preselected set of mode functions giving an equivalent matrix equation to be solved for the mode-function expansion coefficients. Because of the inherent smoothness of the original problem, the coefficient problem can be solved approximately without significantly affecting the accuracy of the final solution. Very promising two-dimensional results are obtained and the extension of the method to three-dimensional problems is investigated. On the basis of these results it is shown that the computing time for the matrix solution for a large three-dimensional panel method calculation could be reduced by an order of magnitude compared with that required for a direct solution.
Grose, W. L.
1971-01-01
An approximate inverse solution is presented for the nonequilibrium flow in the inviscid shock layer about a vehicle in hypersonic flight. The method is based upon a thin-shock-layer approximation and has the advantage of being applicable to both subsonic and supersonic regions of the shock layer. The relative simplicity of the method makes it ideally suited for programming on a digital computer with a significant reduction in storage capacity and computing time required by other more exact methods. Comparison of nonequilibrium solutions for an air mixture obtained by the present method is made with solutions obtained by two other methods. Additional cases are presented for entry of spherical nose cones into representative Venusian and Martian atmospheres. A digital computer program written in FORTRAN language is presented that permits an arbitrary gas mixture to be employed in the solution. The effects of vibration, dissociation, recombination, electronic excitation, and ionization are included in the program.
Maslen, S. H.
1974-01-01
A general method developed for the analysis of inviscid hypersonic shock layers is discussed for application to the case of the shuttle vehicle at high (65 deg) angle of attack. The associated extensive subsonic flow region caused convergence difficulties whose resolution is discussed. It is required that the solution be smoother than anticipated.
Putnam, L. E.; Hodges, J.
1983-01-01
The Langley Research Center of the National Aeronautics and Space Administration and the Royal Aircraft Establishment have undertaken a cooperative program to conduct an assessment of their patched viscous-inviscid interaction methods for predicting the transonic flow over nozzle afterbodies. The assessment was made by comparing the predictions of the two methods with experimental pressure distributions and boattail pressure drag for several convergent circular-arc nozzle configurations. Comparisons of the predictions of the two methods with the experimental data showed that both methods provided good predictions of the flow characteristics of nozzles with attached boundary layer flow. The RAE method also provided reasonable predictions of the pressure distributions and drag for the nozzles investigated that had separated boundary layers. The NASA method provided good predictions of the pressure distribution on separated flow nozzles that had relatively thin boundary layers. However, the NASA method was in poor agreement with experiment for separated nozzles with thick boundary layers due primarily to deficiencies in the method used to predict the separation location.
International Nuclear Information System (INIS)
Li Jiequan; Li Qibing; Xu Kun
2011-01-01
The generalized Riemann problem (GRP) scheme for the Euler equations and gas-kinetic scheme (GKS) for the Boltzmann equation are two high resolution shock capturing schemes for fluid simulations. The difference is that one is based on the characteristics of the inviscid Euler equations and their wave interactions, and the other is based on the particle transport and collisions. The similarity between them is that both methods can use identical MUSCL-type initial reconstructions around a cell interface, and the spatial slopes on both sides of a cell interface involve in the gas evolution process and the construction of a time-dependent flux function. Although both methods have been applied successfully to the inviscid compressible flow computations, their performances have never been compared. Since both methods use the same initial reconstruction, any difference is solely coming from different underlying mechanism in their flux evaluation. Therefore, such a comparison is important to help us to understand the correspondence between physical modeling and numerical performances. Since GRP is so faithfully solving the inviscid Euler equations, the comparison can be also used to show the validity of solving the Euler equations itself. The numerical comparison shows that the GRP exhibits a slightly better computational efficiency, and has comparable accuracy with GKS for the Euler solutions in 1D case, but the GKS is more robust than GRP. For the 2D high Mach number flow simulations, the GKS is absent from the shock instability and converges to the steady state solutions faster than the GRP. The GRP has carbuncle phenomena, likes a cloud hanging over exact Riemann solvers. The GRP and GKS use different physical processes to describe the flow motion starting from a discontinuity. One is based on the assumption of equilibrium state with infinite number of particle collisions, and the other starts from the non-equilibrium free transport process to evolve into an
International Nuclear Information System (INIS)
Buntine, J.D.
1994-01-01
Part I. A study of the behaviour of an inviscid, swirling fluid is performed. This flow can be described by the Squire-Long equation if the constraints of time-independence and axisymmetry are invoked. The particular case of flow through a diverging pipe is selected and a study is conducted to determine over what range of parameters does a solution exist. The work is performed with a view to understanding how the phenomenon of vortex breakdown develops. Experiments and previous numerical studies have indicated that the flow is sensitive to boundary conditions particularly at the pipe inlet. A open-quotes quasi-cylindricalclose quotes amplification of the Squire-Long equation is compared with the more complete model and shown to be able to account for most of its behaviour. An advantage of this latter representation is the relatively undetailed description of the flow geometry it requires in order to calculate a solution. open-quotes Criticalityclose quotes or the ability of small disturbances to propagate upstream is related to results of the quasi-cylindrical and axisymmetric flow models. This leads to an examination of claims made by researchers such as Benjamin and Hall concerning the interrelationship between open-quotes failureclose quotes of the quasi-cylindrical model and the occurrence of a open-quotes criticalclose quotes flow state. Lundgren developed an analytical model for homogeneous turbulence based on a collection of contracting spiral vortices each embedded in an axisymmetric strain field. Using asymptotic approximations he was able to deduce the Kolmogorov k -5/3 behaviour for inertial scales in the turbulence energy spectrum. Pullin ampersand Saffman have enlarged upon his work to make a number of predictions about the behaviour of turbulence described by the model. This work investigates the model numerically. The first part considers how the flow description compares with numerical simulations using the Navier-Stokes equations
Hydraulic Performances of a Mixed-Flow Pump: Unsteady Inviscid Computations and Loss Models
van Esch, B.P.M.; van Esch, B.P.M.; Kruyt, Nicolaas P.
2001-01-01
The hydraulic performance of an industrial mixed-flow pump is analyzed using a three-dimensional potential flow model to compute the unsteady flow through the entire pump configuration. Subsequently, several additional models that use the potential flow results are employed to assess the losses.
Developments in the simulation of compressible inviscid and viscous flow on supercomputers
International Nuclear Information System (INIS)
Steger, J.L.; Buning, P.G.; Tel Aviv Univ., Israel)
1985-01-01
In anticipation of future supercomputers, finite difference codes are rapidly being extended to simulate three-dimensional compressible flow about complex configurations. Some of these developments are reviewed. The importance of computational flow visualization and diagnostic methods to three-dimensional flow simulation is also briefly discussed. 46 references
Numerical Solution of Inviscid Compressible Steady Flows around the RAE 2822 Airfoil
Directory of Open Access Journals (Sweden)
Kryštůfek P.
2015-01-01
Full Text Available The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Euler equations in 2D compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil. The results are compared with the solution using the software Ansys Fluent 15.0.7.
Numerical Solution of Inviscid Compressible Steady Flows around the RAE 2822 Airfoil
Kryštůfek, P.; Kozel, K.
2015-05-01
The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Euler equations in 2D compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil. The results are compared with the solution using the software Ansys Fluent 15.0.7.
An Improved Ghost-cell Immersed Boundary Method for Compressible Inviscid Flow Simulations
Chi, Cheng
2015-05-01
This study presents an improved ghost-cell immersed boundary approach to represent a solid body in compressible flow simulations. In contrast to the commonly used approaches, in the present work ghost cells are mirrored through the boundary described using a level-set method to farther image points, incorporating a higher-order extra/interpolation scheme for the ghost cell values. In addition, a shock sensor is in- troduced to deal with image points near the discontinuities in the flow field. Adaptive mesh refinement (AMR) is used to improve the representation of the geometry efficiently. The improved ghost-cell method is validated against five test cases: (a) double Mach reflections on a ramp, (b) supersonic flows in a wind tunnel with a forward- facing step, (c) supersonic flows over a circular cylinder, (d) smooth Prandtl-Meyer expansion flows, and (e) steady shock-induced combustion over a wedge. It is demonstrated that the improved ghost-cell method can reach the accuracy of second order in L1 norm and higher than first order in L∞ norm. Direct comparisons against the cut-cell method demonstrate that the improved ghost-cell method is almost equally accurate with better efficiency for boundary representation in high-fidelity compressible flow simulations. Implementation of the improved ghost-cell method in reacting Euler flows further validates its general applicability for compressible flow simulations.
A computational study of inviscid hypersonic flows using energy relaxation method
International Nuclear Information System (INIS)
Nagdewe, Suryakant; Kim, H. D.; Shevare, G. R.
2008-01-01
Reasonable analysis of hypersonic flows requires a thermodynamic non-equilibrium model to properly simulate strong shock waves or high pressure and temperature states in the flow field. The energy relaxation method (ERM) has been used to model such a non-equilibrium effect which is generally expressed as a hyperbolic system of equations with a stiff relaxation source term. Relaxation time that is multiplied with source terms is responsible for nonequilibrium in the system. In the present study, a numerical analysis has been carried out with varying values of relaxation time for several hypersonic flows with AUSM (advection upstream splitting method) as a numerical scheme. Vibration modes of thermodynamic nonequilibrium effects are considered. The results obtained showed that, as the relaxation time reduces to zero, the solution marches toward equilibrium, while it shows non-equilibrium effects, as the relaxation time increases. The present computations predicted the experiment results of hypersonic flows with good accuracy. The work carried out suggests that the present energy relaxation method can be robust for analysis of hypersonic flows
Multiple inviscid solutions for the flow in a leading- edge vortex
van Noordenburg, M.B.H.; Hoeijmakers, Hendrik Willem Marie
2000-01-01
To analyze the flowfield inside the vortex formed at the leading edge of a highly swept wing at an angle of attack, conical similarity solutions of the compressible Euler equations have been obtained and compared to incompressible conical similarity flow solutions. It is shown that, in contrast to
A two-dimensional, TVD numerical scheme for inviscid, high Mach number flows in chemical equilibrium
Eberhardt, S.; Palmer, G.
1986-01-01
A new algorithm has been developed for hypervelocity flows in chemical equilibrium. Solutions have been achieved for Mach numbers up to 15 with no adverse effect on convergence. Two methods of coupling an equilibrium chemistry package have been tested, with the simpler method proving to be more robust. Improvements in boundary conditions are still required for a production-quality code.
Riley, Christopher J.
1992-01-01
An engineering method has been developed that couples an approximate three dimensional inviscid technique with the axisymmetric analog and a set of approximate convective heating equations. The displacement effect on the boundary layer on the outer inviscid flow is calculated and included as a boundary condition in the inviscid technique. This accounts for the viscous interaction present at lower Reynolds numbers. The method is applied to blunted axisymmetric and three dimensional elliptic cones at angle of attack for the laminar hypersonic flow of a perfect gas. The method is applied to turbulent and equilibrium-air conditions. The present technique predicts surface heating rates, pressures, and shock shapes that compare favorably with experimental (ground-test and flight) data and numerical solutions of the Navier-Stokes and viscous shock-layer equations. In addition, the inclusion of viscous interaction significantly improves results obtained at lower Reynolds numbers. The new technique represents a major improvement over current engineering aerothermal methods with only a modest increase in computational effort.
Bartholomay, Sirko; Ramos-García, Néstor; Mikkelsen, Robert Flemming; Technical University of Denmark (DTU)-WInd Energy Team
2014-11-01
The viscous-inviscid flow solver Q3UIC for 2D aerodynamics has recently been developed at the Technical University of Denmark. The Q3UIC solver takes viscous and unsteady effects into account by coupling an unsteady inviscid panel method with the integral boundary layer equations by means of a strong coupling between the viscous and inviscid parts, and in this respect differs from other classic panel codes e.g. Xfoil. In the current work a Runge-Kutta-Nyström scheme was employed to couple inertial, elastic and aerodynamical forces and moments calculated by Q3UIC for a two-dimensional blade section in the time-domain. Numerical simulations are validated by a three step experimental verification process carried out in the low-turbulence wind tunnel at DTU. First, a comparison against steady experiments for a NACA 64418 profile and a flexible trailing edge flap is presented for different fixed flap angles, and second, the measured aerodynamic characteristics considering prescribed motion of the airfoil with a moving flap are compared to the Q3UIC predictions. Finally, an aeroelastic experiment for one degree of freedom-airfoil pitching- is used to evaluate the accuracy of aeroelastic coupling.
A Viscous-Inviscid Interaction Model for Rotor Aerodynamics
DEFF Research Database (Denmark)
Filippone, Antonino; Sørensen, Jens Nørkær
1994-01-01
A numerical model for the viscous-inviscid interactive computations ofrotor flows is presented. The basic methodology for deriving the outer inviscid solution is a fully three-dimensional boundary element method.The inner viscous domain, i.e. the boundary layer, is described by the two-dimensiona...
Viscous-inviscid interaction with the quasi-simultaneous method for 2D and 3D aerodynamic flow
Coenen, Edith Gerda Maria
2001-01-01
Flow phenomena are around us everywhere. One can think of the waves in the sea or the wind playing with the leaves fallen from the trees. Most of these fluid flow situations are described by the so-called Navier-Stokes equations which are based on the conservation laws of mass, momentum and energy.
Inviscid flux-splitting algorithms for real gases with non-equilibrium chemistry
Shuen, Jian-Shun; Liou, Meng-Sing; Van Leer, Bram
1990-01-01
Formulations of inviscid flux splitting algorithms for chemical nonequilibrium gases are presented. A chemical system for air dissociation and recombination is described. Numerical results for one-dimensional shock tube and nozzle flows of air in chemical nonequilibrium are examined.
Viscous-Inviscid Coupling Methods for Advanced Marine Propeller Applications
Greve, Martin; Wöckner-Kluwe, Katja; Abdel-Maksoud, Moustafa; Rung, Thomas
2012-01-01
The paper reports the development of coupling strategies between an inviscid direct panel method and a viscous RANS method and their application to complex propeller ows. The work is motivated by the prohibitive computational cost associated to unsteady viscous flow simulations using geometrically resolved propellers to analyse the dynamics of ships in seaways. The present effort aims to combine the advantages of the two baseline methods in order to reduce the numerical effort without comprom...
Directory of Open Access Journals (Sweden)
Sorin BERBENTE
2011-12-01
Full Text Available A gas (oxidizer flows between two parallel walls of solid fuel. A combustion is initiated: the solid fuel is vaporized and a diffusive flame occurs. The hot combustion products are submitted both to thermal diffusion and convection. Analytical solutions can be obtained both for the velocity and temperature distributions by considering an equivalent mean temperature where the density and the thermal conductivity are evaluated. The main effects of heat transfer are due to heat convection at the flame. Because the detailed mechanism of the diffusion flame is not introduced the reference chemical reaction is the combustion of premixed fuel with oxidizer in excess. In exchange the analytical solution is used to define an ideal quasi-uniform combustion that could be realized by an n adequate control. The given analytical closed solutions prove themselves flexible enough to adjust the main data of some existing experiments and to suggest new approaches to the problem.
Stabilization of Inviscid Vortex Sheets
Protas, Bartosz; Sakajo, Takashi
2017-11-01
In this study we investigate the problem of stabilizing inviscid vortex sheets via feedback control. Such models, expressed in terms of the Birkhoff-Rott equation, are often used to describe the Kevin-Helmholtz instability of shear layers and are known to be strongly unstable to small-scale perturbations. First, we consider the linear stability of a straight vortex sheet in the periodic setting with actuation in the form of an array of point vortices or sources located a certain distance away from the sheet. We establish conditions under which this system is controllable and observable. Next, using methods of the linear control theory, we synthesize a feedback control strategy which stabilizes a straight vortex sheet in the linear regime. Given the poor conditioning of the discretized problem, reliable solution of the resulting algebraic Riccati equation requires the use of high-precision arithmetic. Finally, we demonstrate that this control approach also succeeds in the nonlinear regime, provided the magnitude of the initial perturbation is sufficiently small.
Spatial-Temporal Instability of an Inviscid Shear Layer
Directory of Open Access Journals (Sweden)
Qing-fei Fu
2017-01-01
Full Text Available In this work, we explore the transition of absolute instability and convective instability in a compressible inviscid shear layer, through a linear spatial-temporal instability analysis. From linearized governing equations of the shear layer and the ideal-gas equation of state, the dispersion relation for the pressure perturbation was obtained. The eigenvalue problem for the evolution of two-dimensional perturbation was solved by means of shooting method. The zero group velocity is obtained by a saddle point method. The absolute/convective instability characteristics of the flow are determined by the temporal growth rate at the saddle point. The absolute/convective nature of the flow instability has strong dependence on the values of the temperature ratio, the velocity ratio, the oblique angle, and M number. A parametric study indicates that, for a great value of velocity ratio, the inviscid shear layer can transit to absolute instability. The increase of temperature ratio decreases the absolute growth rate when the temperature ratio is large; the effect of temperature ratio is opposite when the temperature ratio is relatively small. The obliquity of the perturbations would cause the increase of the absolute growth rate. The effect of M number is different when the oblique angle is great and small. Besides, the absolute instability boundary is found in the velocity ratio, temperature ratio, and M number space.
Inviscid/Boundary-Layer Aeroheating Approach for Integrated Vehicle Design
Lee, Esther; Wurster, Kathryn E.
2017-01-01
A typical entry vehicle design depends on the synthesis of many essential subsystems, including thermal protection system (TPS), structures, payload, avionics, and propulsion, among others. The ability to incorporate aerothermodynamic considerations and TPS design into the early design phase is crucial, as both are closely coupled to the vehicle's aerodynamics, shape and mass. In the preliminary design stage, reasonably accurate results with rapid turn-representative entry envelope was explored. Initial results suggest that for Mach numbers ranging from 9-20, a few inviscid solutions could reasonably sup- port surface heating predictions at Mach numbers variation of +/-2, altitudes variation of +/-10 to 20 kft, and angle-of-attack variation of +/- 5. Agreement with Navier-Stokes solutions was generally found to be within 10-15% for Mach number and altitude, and 20% for angle of attack. A smaller angle-of-attack increment than the 5 deg around times for parametric studies and quickly evolving configurations are necessary to steer design decisions. This investigation considers the use of an unstructured 3D inviscid code in conjunction with an integral boundary-layer method; the former providing the flow field solution and the latter the surface heating. Sensitivity studies for Mach number, angle of attack, and altitude, examine the feasibility of using this approach to populate a representative entry flight envelope based on a limited set of inviscid solutions. Each inviscid solution is used to generate surface heating over the nearby trajectory space. A subset of a considered in this study is recommended. Results of the angle-of-attack sensitivity studies show that smaller increments may be needed for better heating predictions. The approach is well suited for application to conceptual multidisciplinary design and analysis studies where transient aeroheating environments are critical for vehicle TPS and thermal design. Concurrent prediction of aeroheating
Newton solution of inviscid and viscous problems
International Nuclear Information System (INIS)
Venkatakrishnan, V.
1988-01-01
The application of Newton iteration to inviscid and viscous airfoil calculations is examined. Spatial discretization is performed using upwind differences with split fluxes. The system of linear equations which arises as a result of linearization in time is solved directly using either a banded matrix solver or a sparse matrix solver. In the latter case, the solver is used in conjunction with the nested dissection strategy, whose implementation for airfoil calculations is discussed. The boundary conditions are also implemented in a fully implicit manner, thus yielding quadratic convergence. Complexities such as the ordering of cell nodes and the use of a far field vortex to correct freestream for a lifting airfoil are addressed. Various methods to accelerate convergence and improve computational efficiency while using Newton iteration are discussed. Results are presented for inviscid, transonic nonlifting and lifting airfoils and also for laminar viscous cases. 17 references
Inviscid incompressible limits on expanding domains
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Nečasová, Šárka; Sun, Y.
2014-01-01
Roč. 27, č. 10 (2014), s. 2465-2477 ISSN 0951-7715 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : compressible Navier-Stokes system * large domain * inviscid limit * incompressible limit Subject RIV: BA - General Mathematics Impact factor: 1.208, year: 2014 http://iopscience.iop.org/0951-7715/27/10/2465/
Inviscid Design of Hypersonic Wind Tunnel Nozzles for a Real Gas
Korte, J. J.
2000-01-01
A straightforward procedure has been developed to quickly determine an inviscid design of a hypersonic wind tunnel nozzle when the test crash is both calorically and thermally imperfect. This real gas procedure divides the nozzle into four distinct parts: subsonic, throat to conical, conical, and turning flow regions. The design process is greatly simplified by treating the imperfect gas effects only in the source flow region. This simplification can be justified for a large class of hypersonic wind tunnel nozzle design problems. The final nozzle design is obtained either by doing a classical boundary layer correction or by using this inviscid design as the starting point for a viscous design optimization based on computational fluid dynamics. An example of a real gas nozzle design is used to illustrate the method. The accuracy of the real gas design procedure is shown to compare favorably with an ideal gas design based on computed flow field solutions.
An inviscid model for vortex shedding from a deforming body
Energy Technology Data Exchange (ETDEWEB)
Shukla, Ratnesh K.; Eldredge, Jeff D. [University of California, Mechanical and Aerospace Engineering Department, Los Angeles, CA (United States)
2007-09-15
An inviscid vortex sheet model is developed in order to study the unsteady separated flow past a two-dimensional deforming body which moves with a prescribed motion in an otherwise quiescent fluid. Following Jones (J Fluid Mech 496, 405-441, 2003) the flow is assumed to comprise of a bound vortex sheet attached to the body and two separate vortex sheets originating at the edges. The complex conjugate velocity potential is expressed explicitly in terms of the bound vortex sheet strength and the edge circulations through a boundary integral representation. It is shown that Kelvin's circulation theorem, along with the conditions of continuity of the normal velocity across the body and the boundedness of the velocity field, yields a coupled system of equations for the unknown bound vortex sheet strength and the edge circulations. A general numerical treatment is developed for the singular principal value integrals arising in the solution procedure. The model is validated against the results of Jones (J Fluid Mech 496, 405-441, 2003) for computations involving a rigid flat plate and is subsequently applied to the flapping foil experiments of Heathcote et al. (AIAA J, 42, 2196-2204, 2004) in order to predict the thrust coefficient. The utility of the model in simulating aquatic locomotion is also demonstrated, with vortex shedding suppressed at the leading edge of the swimming body. (orig.)
An inviscid three-dimensional analysis of the Space Shuttle main engine hot-gas manifold
Liang, P. Y.
1983-01-01
A numerical study using an inviscid three-dimensional Lagrangian fluid dynamics code has been conducted as a part of an overall effort to understand the flow behavior in the SSME fuel side hot-gas manifold. The model simulates flow from the high-pressure fuel turbine exit through the transfer ducts, including the effects of swirl, inlet flow symmetry, and presence of straightening vanes and struts; a separate, more-detailed effort is in progress that includes viscosity and turbulence effects. The simplified model presented is divided into two parts, the first includes the 180-degree turnaround duct downstream of the turbine exit and the spherical fuel bowl section, while the second models the three transfer ducts. The two parts of the model are coupled together with the interface conditions being updated through iteration. Results indicate that a transverse pressure differential of 165 psi would be imposed on the turbine exit and that unstable flow separation occurs around the vanes, struts, and within the transfer ducts. The three transfer ducts show a mass flux split of approximately 41, 21, and 38 percent. Results to date are encouraging that certain flow characteristics can be usefuly represented using a relatively coarse grid inviscid code.
Viscous-inviscid interaction using the parabolized Navier-Stokes equations
DEFF Research Database (Denmark)
Filippone, Antonino; Sørensen, Jens Nørkær
1997-01-01
adaptive grid is used.The interaction is achieved by iterative updatingof the boundary conditions, through the wall transpiration concept. The Navier-Stokes equationsare discretized on a semi-staggered grid.Space-marching integration is performed starting from the stagnation streamline ontwo independent......A numerical model for the calculation of incompressible viscous flows past airfoils andwings has been developed. The approach is based on a strong viscous-inviscid coupling of aboundary element method with the Navier-Stokesequations in vorticity-streamfunction formulation.A semi-adaptive or fully...
A strong viscous–inviscid interaction model for rotating airfoils
DEFF Research Database (Denmark)
Ramos García, Néstor; Sørensen, Jens Nørkær; Shen, Wen Zhong
2014-01-01
version, a parametric study on rotational effects induced by the Coriolis and centrifugal forces in the boundary-layer equations shows that the effects of rotation are to decrease the growth of the boundary-layer and delay the onset of separation, hence increasing the lift coefficient slightly while...... the viscous and inviscid parts. The inviscid part is modeled by a 2D panel method, and the viscous part is modeled by solving the integral form of the laminar and turbulent boundary-layer equations with extension for 3D rotational effects. Laminar-to-turbulent transition is either forced by employing...
Stability of a Bubble Expanding and Translating Through an Inviscid ...
Indian Academy of Sciences (India)
A bubble expands adiabatically and translates in an incompressible and inviscid liquid. We investigate the number of equilibrium points of the bubble and the nature of stability of the bubble at these points. We find that there is only one equilibrium point and the bubble is stable there.
Stability of a bubble expanding and translating through an inviscid ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
Department of Mathematics, Delhi University, Delhi 110 007, India. MS received 27 August 2001; revised 2 February 2002. Abstract. A bubble expands adiabatically and translates in an incompressible and inviscid liquid. We investigate the number of equilibrium points of the bubble and the nature of stability of the bubble at ...
Cebeci, Tuncer
2005-01-01
This second edition of our book extends the modeling and calculation of boundary-layer flows to include compressible flows. The subjects cover laminar, transitional and turbulent boundary layers for two- and three-dimensional incompressible and compressible flows. The viscous-inviscid coupling between the boundary layer and the inviscid flow is also addressed. The book has a large number of homework problems.
Inviscid melt spinning-IMS crystallization of amorphous alumina fibers
Energy Technology Data Exchange (ETDEWEB)
Wallenberger, F.T. (E.I. Du Pont De Nemours Co., Wilmington, DE (USA)); Dunn, S.A. (Univ. of Wisconsin, Madison (USA)); Weston, N.E.
1990-04-01
Experimental amorphous Al{sub 2}O{sub 3}CaO fibers (<80% Al{sub 2}O{sub 3}) which had been made by inviscid melt spinning (IMS) of low viscosity melts were found to retain up to 87% of their room temperature tensile strength at 750{degree}C (versus 25% for S-glass). The results suggest that the strength of these fibers is ultimately limited by their crystallization temperatures and that they might tolerate 100-200{degree}C higher temperatures than S-glass in comparable applications (e.g., in fiber reinforced composites). Some fibers were crystallized in a laboratory furnace. The crystalline phases of the resulting fibers were correlated with measured properties. The implications were applied to an analysis of a proposed process for redrawing inviscid melt spun (RIMS) fibers.
Magnetogasdynamic Flow Acceleration in a Scramjet Nozzle
National Research Council Canada - National Science Library
Harrington, Brian
2004-01-01
.... The parameters of conductivity pattern and load factor are varied in both inviscid and viscous flow regimes with the intent of increasing axial force exerted on the flow through a scramjet accelerator...
Discrete Symmetries Analysis and Exact Solutions of the Inviscid Burgers Equation
Directory of Open Access Journals (Sweden)
Hongwei Yang
2012-01-01
Full Text Available We discuss the Lie point symmetries and discrete symmetries of the inviscid Burgers equation. By employing the Lie group method of infinitesimal transformations, symmetry reductions and similarity solutions of the governing equation are given. Based on discrete symmetries analysis, two groups of discrete symmetries are obtained, which lead to new exact solutions of the inviscid Burgers equation.
Shallow water equations: viscous solutions and inviscid limit
Chen, Gui-Qiang; Perepelitsa, Mikhail
2012-12-01
We establish the inviscid limit of the viscous shallow water equations to the Saint-Venant system. For the viscous equations, the viscosity terms are more degenerate when the shallow water is close to the bottom, in comparison with the classical Navier-Stokes equations for barotropic gases; thus, the analysis in our earlier work for the classical Navier-Stokes equations does not apply directly, which require new estimates to deal with the additional degeneracy. We first introduce a notion of entropy solutions to the viscous shallow water equations and develop an approach to establish the global existence of such solutions and their uniform energy-type estimates with respect to the viscosity coefficient. These uniform estimates yield the existence of measure-valued solutions to the Saint-Venant system generated by the viscous solutions. Based on the uniform energy-type estimates and the features of the Saint-Venant system, we further establish that the entropy dissipation measures of the viscous solutions for weak entropy-entropy flux pairs, generated by compactly supported C 2 test-functions, are confined in a compact set in H -1, which yields that the measure-valued solutions are confined by the Tartar-Murat commutator relation. Then, the reduction theorem established in Chen and Perepelitsa [5] for the measure-valued solutions with unbounded support leads to the convergence of the viscous solutions to a finite-energy entropy solution of the Saint-Venant system with finite-energy initial data, which is relative with respect to the different end-states of the bottom topography of the shallow water at infinity. The analysis also applies to the inviscid limit problem for the Saint-Venant system in the presence of friction.
Inviscid linear stability analysis of two fluid columns of different densities subject to gravity
Prathama, Aditya; Pantano, Carlos
2017-11-01
We investigate the inviscid linear stability of vertical interface between two fluid columns of different densities under the influence of gravity. In this flow arrangement, the two free streams are continuously accelerating, in contrast to the canonical Kelvin-Helmholtz or Rayleigh-Taylor instabilities whose base flows are stationary (or weakly time dependent). In these classical cases, the temporal evolution of the interface can be expressed as Fourier or Laplace solutions in time. This is not possible in our case; instead, we employ the initial value problem method to solve the equations analytically. The results, expressed in terms of the well-known parabolic cylinder function, indicate that the instability grows as the exponential of a quadratic function of time. The analysis shows that in this accelerating Kelvin-Helmholtz configuration, the interface is unconditionally unstable at all wave modes, despite the presence of surface tension. Department of Energy, National Nuclear Security Administration (Award No. DE-NA0002382) and the California Institute of Technology.
Real gas flows with high velocities
Lunev, Vladimir V
2009-01-01
Gasdynamic Model and Equations Outline of the Gasdynamic Model Basic Equations and Postulates Equations of State Kinetic Theory Second Law of Thermodynamics Speed of Sound Integral Equations of Motion Kinematics of Fluid Media Differential Equations of Gasdynamics Rheological Model Initial and Boundary Conditions Similarity and Modeling in Gasdynamics Euler Equations Navier-Stokes Equations Turbulent Flows Viscous and Inviscid Flow Models Inviscid Gasdynamics Stream Function, Potential,
A counter-rotating vortex pair in inviscid fluid
Habibah, Ummu; Fukumoto, Yasuhide
2017-12-01
We study the motion of a counter-rotating vortex pair with the circulations ±Γ move in incompressible fluid. The assumption is made that the core is very thin, that is the core radius σ is much smaller than the vortex radius d such that ɛ = σ/d ≪ 1. With this condition, the method of matched asymptotic expansion is employed. The solutions of the Navier-Stokes equations and the Biot-Savart law, regarding the inner and outer solutions respectively, are constructed in the form of a small parameter. An asymptotic expansion of the Biot-Savart law near the vortex core provides with the matching condition for an asymptotic expansion for limiting the Navier-Stokes equations for large radius r. The general formula of an anti-parallel vortex pair is established. At leading order O(ɛ0), we apply the special case in inviscid fluid, the Rankine vortex, a circular vortex of uniform vorticity. Furthermore at leading order O(ɛ5) we show the traveling speed of a vortex pair.
Numerical simulation of viscous transonic airfoil flows
Coakley, Thomas J.
1987-01-01
Numerical simulations of transonic airfoil flows using the Reynolds-averaged Navier-Stokes equations and various turbulence models are presented and compared with experimental data. Three different airfoils were investigated under varying flow conditions ranging from subcritical unseparated flows to supercritical separated flows. The turbulence models investigated consisted of three zero-equation models and one two-equation model. For unseparated flows involving weak viscous-inviscid interactions, the four models were comparable in their agreement with experiment. For separated flows involving strong viscous-inviscid interactions, the nonequilibrium zero-equation model of Johnson and King gave the best overall agreement with experiment.
Numerical simulation of 2D and 3D compressible flows
Huml, Jaroslav; Kozel, Karel; Příhoda, Jaromír
2013-02-01
The work deals with numerical solutions of 2D inviscid and laminar compressible flows in the GAMM channel and DCA 8% cascade, and of 3D inviscid compressible flows in a 3D modification of the GAMM channel (Swept Wing). The FVM multistage Runge-Kutta method and the Lax-Wendroff scheme (Richtmyer's form) with Jameson's artificial dissipation were applied to obtain the numerical solutions. The results are discussed and compared to other similar results and experiments.
A quasi-3D viscous-inviscid interaction code: Q^{3}UIC
DEFF Research Database (Denmark)
Ramos García, Néstor; Sørensen, Jens Nørkær; Shen, Wen Zhong
2014-01-01
and inviscid parts. The rotational effects generated by centrifugal and Coriolis forces are introduced in Q3UIC via the streamwise and spanwise integral boundary layer momentum equations. A special inviscid version of the code has been developed to cope with massive separation. To check the ability of the code...
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Novotný, A.; Sun, Y.
2014-01-01
Roč. 34, č. 1 (2014), s. 121-143 ISSN 1078-0947 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : compressible MHD system * inviscid limit * incompressible limit Subject RIV: BA - General Mathematics Impact factor: 0.826, year: 2014 http://aimsciences.org/journals/displayArticlesnew.jsp?paperID=8717
Selective decay by Casimir dissipation in inviscid fluids
International Nuclear Information System (INIS)
Gay-Balmaz, François; Holm, Darryl D
2013-01-01
The problem of parameterizing the interactions of larger scales and smaller scales in fluid flows is addressed by considering a property of two-dimensional (2D) incompressible turbulence. The property we consider is selective decay, in which a Casimir of the ideal formulation (enstrophy in 2D flows, helicity in three-dimensional flows) decays in time, while the energy stays essentially constant. This paper introduces a mechanism that produces selective decay by enforcing Casimir dissipation in fluid dynamics. This mechanism turns out to be related in certain cases to the numerical method of anticipated vorticity discussed in Sadourny and Basdevant (1981 C. R. Acad. Sci. Paris 292 1061–4, 1985 J. Atm. Sci. 42 1353–63). Several examples are given and a general theory of selective decay is developed that uses the Lie–Poisson structure of the ideal theory. A scale-selection operator allows the resulting modifications of the fluid motion equations to be interpreted in several examples as parametrizing the nonlinear, dynamical interactions between disparate scales. The type of modified fluid equation systems derived here may be useful in modelling turbulent geophysical flows where it is computationally prohibitive to rely on the slower, indirect effects of a realistic viscosity, such as in large-scale, coherent, oceanic flows interacting with much smaller eddies. (paper)
Average-passage flow model development
Adamczyk, John J.; Celestina, Mark L.; Beach, Tim A.; Kirtley, Kevin; Barnett, Mark
1989-01-01
A 3-D model was developed for simulating multistage turbomachinery flows using supercomputers. This average passage flow model described the time averaged flow field within a typical passage of a bladed wheel within a multistage configuration. To date, a number of inviscid simulations were executed to assess the resolution capabilities of the model. Recently, the viscous terms associated with the average passage model were incorporated into the inviscid computer code along with an algebraic turbulence model. A simulation of a stage-and-one-half, low speed turbine was executed. The results of this simulation, including a comparison with experimental data, is discussed.
Betchov, R
2012-01-01
Stability of Parallel Flows provides information pertinent to hydrodynamical stability. This book explores the stability problems that occur in various fields, including electronics, mechanics, oceanography, administration, economics, as well as naval and aeronautical engineering. Organized into two parts encompassing 10 chapters, this book starts with an overview of the general equations of a two-dimensional incompressible flow. This text then explores the stability of a laminar boundary layer and presents the equation of the inviscid approximation. Other chapters present the general equation
Boundary-layer interactions in the plane-parallel incompressible flows
International Nuclear Information System (INIS)
Nguyen, Toan T; Sueur, Franck
2012-01-01
We study the inviscid limit problem of incompressible flows in the presence of both impermeable regular boundaries and a hypersurface transversal to the boundary across which the inviscid flow has a discontinuity jump. In the former case, boundary layers have been introduced by Prandtl as correctors near the boundary between the inviscid and viscous flows. In the latter case, the viscosity smoothes out the discontinuity jump by creating a transition layer which has the same amplitude and thickness as the Prandtl layer. In the neighbourhood of the intersection of the impermeable boundary and of the hypersurface, interactions between the boundary and the transition layers must then be considered. In this paper, we initiate a mathematical study of this interaction and carry out a strong convergence in the inviscid limit for the case of the plane-parallel flows introduced by Di Perna and Majda (1987 Commun. Math. Phys. 108 667–89). (paper)
Riley, Christopher J.
1993-01-01
An engineering inviscid-boundary layer method has been modified for application to slender three-dimensional (3-D) forebodies which are characteristic of transatmospheric vehicles. An improved shock description in the nose region has been added to the inviscid technique which allows the calculation of a wider range of body geometries. The modified engineering method is applied to the perfect gas solution over a slender 3-D configuration at angle of attack. The method predicts surface pressures and laminar heating rates on the windward side of the vehicle that compare favorably with numerical solutions of the thin-layer Navier-Stokes equations. These improvements extend the 3-D capabilities of the engineering method and significantly increase its design applications.
Directory of Open Access Journals (Sweden)
Rajneesh Kumar
2014-01-01
Full Text Available The present investigation deals with the propagation of Rayleigh type surface waves in an isotropic microstretch thermoelastic diffusion solid half space under a layer of inviscid liquid. The secular equation for surface waves in compact form is derived after developing the mathematical model. The dispersion curves giving the phase velocity and attenuation coefficients with wave number are plotted graphically to depict the effect of an imperfect boundary alongwith the relaxation times in a microstretch thermoelastic diffusion solid half space under a homogeneous inviscid liquid layer for thermally insulated, impermeable boundaries and isothermal, isoconcentrated boundaries, respectively. In addition, normal velocity component is also plotted in the liquid layer. Several cases of interest under different conditions are also deduced and discussed.
Energy Technology Data Exchange (ETDEWEB)
Karlsen, Kenneth Hvistendal; Risebro, Nils Henrik
2000-09-01
We consider the initial value problem for degenerate viscous and inviscid scalar conservation laws where the flux function depends on the spatial location through a ''rough'' coefficient function k(x). we show that the Engquist-Osher (and hence all monotone) finite difference approximations converge to the unique entropy solution of the governing equation if, among other demands, k' is in BV, thereby providing alternative (new) existence proofs for entropy solutions of degenerate convection-diffusion equations as well as new convergence results for their finite difference approximations. In the inviscid case, we also provide a rate of convergence. Our convergence proofs are based on deriving a series of a priori estimates and using a general L{sup p} compactness criterion. (author)
Inviscid incompressible limits of the full Navier-Stokes-Fourier system
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Novotný, A.
2013-01-01
Roč. 321, č. 3 (2013), s. 605-628 ISSN 0010-3616 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : Navier-Stokes-Fourier system * inviscid limit * incompressible limit Subject RIV: BA - General Mathematics Impact factor: 1.901, year: 2013 http://link.springer.com/article/10.1007%2Fs00220-013-1691-4
Static Aeroelastic Analysis with an Inviscid Cartesian Method
Rodriguez, David L.; Aftosmis, Michael J.; Nemec, Marian; Smith, Stephen C.
2014-01-01
An embedded-boundary, Cartesian-mesh flow solver is coupled with a three degree-of-freedom structural model to perform static, aeroelastic analysis of complex aircraft geometries. The approach solves a nonlinear, aerostructural system of equations using a loosely-coupled strategy. An open-source, 3-D discrete-geometry engine is utilized to deform a triangulated surface geometry according to the shape predicted by the structural model under the computed aerodynamic loads. The deformation scheme is capable of modeling large deflections and is applicable to the design of modern, very-flexible transport wings. The coupling interface is modular so that aerodynamic or structural analysis methods can be easily swapped or enhanced. After verifying the structural model with comparisons to Euler beam theory, two applications of the analysis method are presented as validation. The first is a relatively stiff, transport wing model which was a subject of a recent workshop on aeroelasticity. The second is a very flexible model recently tested in a low speed wind tunnel. Both cases show that the aeroelastic analysis method produces results in excellent agreement with experimental data.
40 CFR 1065.640 - Flow meter calibration calculations.
2010-07-01
... temperature of the flow rate. R = molar gas constant. M mix = molar mass of the flow rate. Example 1: V stdref...). These governing equations assume one-dimensional isentropic inviscid compressible flow of an ideal gas... ideal gas, the governing equations include a first-order correction for the behavior of a real gas...
van der Vegt, Jacobus J.W.; van der Ven, H.
1998-01-01
A new discretization method for the three-dimensional Euler equations of gas dynamics is presented, which is based on the discontinuous Galerkin finite element method. Special attention is paid to an efficient implementation of the discontinuous Galerkin method that minimizes the number of flux
Inviscid limit of stochastic damped 2D Navier–Stokes equations
International Nuclear Information System (INIS)
Bessaih, Hakima; Ferrario, Benedetta
2014-01-01
We consider the inviscid limit of the stochastic damped 2D Navier–Stokes equations. We prove that, when the viscosity vanishes, the stationary solution of the stochastic damped Navier–Stokes equations converges to a stationary solution of the stochastic damped Euler equation and that the rate of dissipation of enstrophy converges to zero. In particular, this limit obeys an enstrophy balance. The rates are computed with respect to a limit measure of the unique invariant measure of the stochastic damped Navier–Stokes equations. (paper)
Surface wave propagation in a swelling porous elastic material under a inviscid liquid layer
Directory of Open Access Journals (Sweden)
Kuldeep Kumar
2010-12-01
Full Text Available The present investigation is to study the surface wave propagationin a swelling porous elastic half space under homogeneous inviscidliquid layer. The frequency equation is derive for both swellingporous (SP and without swelling porous (elastic medium (EL medium. The dispersion curves giving the phase velocity and attenuation coefficient with wave number are plotted graphically to depict the effect of swelling porous half space under a homogeneous inviscid liquid layer. The amplitudes of displacement in both SP and EL medium are obtained and are shown graphically. Some special cases are also deduced from the present investigation.
Applebaum, Michael P.; Hall, Leslie, H.; Eppard, William M.; Purinton, David C.; Campbell, John R.; Blevins, John A.
2015-01-01
This paper describes the development, testing, and utilization of an aerodynamic force and moment database for the Space Launch System (SLS) Service Module (SM) panel jettison event. The database is a combination of inviscid Computational Fluid Dynamic (CFD) data and MATLAB code written to query the data at input values of vehicle/SM panel parameters and return the aerodynamic force and moment coefficients of the panels as they are jettisoned from the vehicle. The database encompasses over 5000 CFD simulations with the panels either in the initial stages of separation where they are hinged to the vehicle, in close proximity to the vehicle, or far enough from the vehicle that body interference effects are neglected. A series of viscous CFD check cases were performed to assess the accuracy of the Euler solutions for this class of problem and good agreement was obtained. The ultimate goal of the panel jettison database was to create a tool that could be coupled with any 6-Degree-Of-Freedom (DOF) dynamics model to rapidly predict SM panel separation from the SLS vehicle in a quasi-unsteady manner. Results are presented for panel jettison simulations that utilize the database at various SLS flight conditions. These results compare favorably to an approach that directly couples a 6-DOF model with the Cart3D Euler flow solver and obtains solutions for the panels at exact locations. This paper demonstrates a method of using inviscid CFD simulations coupled with a 6-DOF model that provides adequate fidelity to capture the physics of this complex multiple moving-body panel separation event.
On Howard's conjecture in heterogeneous shear flow problem
Indian Academy of Sciences (India)
M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22
Abstract. Howard's conjecture, which states that in the linear instability problem of inviscid heterogeneous parallel shear flow growth rate of an arbitrary unstable wave must approach zero as the wave length decreases to zero, is established in a mathematically rigorous fashion for plane parallel heterogeneous shear flows ...
Viscous-Inviscid Methods in Unsteady Aerodynamic Analysis of Bio-Inspired Morphing Wings
Dhruv, Akash V.
Flight has been one of the greatest realizations of human imagination, revolutionizing communication and transportation over the years. This has greatly influenced the growth of technology itself, enabling researchers to communicate and share their ideas more effectively, extending the human potential to create more sophisticated systems. While the end product of a sophisticated technology makes our lives easier, its development process presents an array of challenges in itself. In last decade, scientists and engineers have turned towards bio-inspiration to design more efficient and robust aerodynamic systems to enhance the ability of Unmanned Aerial Vehicles (UAVs) to be operated in cluttered environments, where tight maneuverability and controllability are necessary. Effective use of UAVs in domestic airspace will mark the beginning of a new age in communication and transportation. The design of such complex systems necessitates the need for faster and more effective tools to perform preliminary investigations in design, thereby streamlining the design process. This thesis explores the implementation of numerical panel methods for aerodynamic analysis of bio-inspired morphing wings. Numerical panel methods have been one of the earliest forms of computational methods for aerodynamic analysis to be developed. Although the early editions of this method performed only inviscid analysis, the algorithm has matured over the years as a result of contributions made by prominent aerodynamicists. The method discussed in this thesis is influenced by recent advancements in panel methods and incorporates both viscous and inviscid analysis of multi-flap wings. The surface calculation of aerodynamic coefficients makes this method less computationally expensive than traditional Computational Fluid Dynamics (CFD) solvers available, and thus is effective when both speed and accuracy are desired. The morphing wing design, which consists of sequential feather-like flaps installed
International Nuclear Information System (INIS)
Zhu, Changjiang; Duan, Renjun
2003-01-01
This paper is concerned with the existence and uniqueness of the entropy solution to the initial boundary value problem for the inviscid Burgers equation. To apply the method of vanishing viscosity to study the existence of the entropy solution, we first introduce the initial boundary value problem for the viscous Burgers equation, and as in Evans (1998 Partial Differential Equations (Providence, RI: American Mathematical Society) and Hopf (1950 Commun. Pure Appl. Math. 3 201-30), give the formula of the corresponding viscosity solutions by Hopf-Cole transformation. Secondly, we prove the convergence of the viscosity solution sequences and verify that the limiting function is an entropy solution. Finally, we give an example to show how our main result can be applied to solve the initial boundary value problem for the Burgers equation
A three-dimensional viscous/potential flow interaction analysis method for multi-element wings
Dvorak, F. A.; Woodward, F. A.; Maskew, B.
1977-01-01
An analysis method and computer program were developed for the calculation of the viscosity dependent aerodynamic characteristics of multi-element, finite wings in incompressible flow. A fully-three dimensional potential flow program is used to determine the inviscid pressure distribution about the configuration. The potential flow program uses surface source and vortex singularities to represent the inviscid flow. The method is capable of analysing configurations having at most one slat, a main element, and two slotted flaps. Configurations are limited to full span slats or flaps. The configuration wake is allowed to relax as a force free wake, although roll up is not allowed at this time. Once the inviscid pressure distribution is calculated, a series of boundary layer computations are made along streamwise strips.
Numerical experiments for turbulent flows
Trefilík, Jiří; Kozel, Karel; Příhoda, Jaromír
2013-04-01
The aim of the work is to explore the possibilities of modelling transonic flows in the internal and external aerodynamics. Several configurations were analyzed and calculations were performed using both inviscid and viscous models of flow. Viscous turbulent flows have been simulated using either zero equation algebraic Baldwin-Lomax model and two equation k—ω model in its basic version and improved TNT variant. The numerical solution was obtained using Lax-Wendroff scheme in the MacCormack form on structured non-ortogonal grids. Artificial dissipation was added to improve the numerical stability. Achieved results are compared with experimental data.
Numerical experiments for turbulent flows
Directory of Open Access Journals (Sweden)
Příhoda Jaromír
2013-04-01
Full Text Available The aim of the work is to explore the possibilities of modelling transonic flows in the internal and external aerodynamics. Several configurations were analyzed and calculations were performed using both inviscid and viscous models of flow. Viscous turbulent flows have been simulated using either zero equation algebraic Baldwin-Lomax model and two equation k—ω model in its basic version and improved TNT variant. The numerical solution was obtained using Lax-Wendroff scheme in the MacCormack form on structured non-ortogonal grids. Artificial dissipation was added to improve the numerical stability. Achieved results are compared with experimental data.
On Dispersive Effects In Inviscid Fluids And Non-Uniqueness Of Weak Wave Maps
Widmayer, Klaus
This work is devoted to the study of some aspects of the well-posedness theory of evolution differential equations in mathematical physics. In Part I we explore the effects of dispersion in incompressible, inviscid fluids in a variety of settings. In the absence of the strongly regularizing mechanism of viscosity, even in only two spatial dimensions effects such as the rotation of the earth or unidirectional gravitational forces are not understood well. For these we bring to light a mechanism that disperses waves, i.e. we show that in such systems waves or disturbances at different frequencies travel at distinct speeds, often also in different directions. On the one hand, this allows us to improve the well-posedness theory of a wide range of problems. In some scenarios this yields a theory that holds on a very large timespan. On the other hand, it may also resolve questions regarding the qualitative behavior of more complicated systems, where effects other than the dispersion play a dominant role. In Part II we study the well-posedness theory of the so-called wave maps equation, which arises in quantum physics. The corresponding energy conservation law suggests a natural mathematical framework. For this problem, however, we show that in the physically relevant setting this consideration does not provide a satisfactory theory: For a given initial setup, the time evolution is not unique.
Simple numerical method for predicting steady compressible flows
Vonlavante, Ernst; Nelson, N. Duane
1986-01-01
A numerical method for solving the isenthalpic form of the governing equations for compressible viscous and inviscid flows was developed. The method was based on the concept of flux vector splitting in its implicit form. The method was tested on several demanding inviscid and viscous configurations. Two different forms of the implicit operator were investigated. The time marching to steady state was accelerated by the implementation of the multigrid procedure. Its various forms very effectively increased the rate of convergence of the present scheme. High quality steady state results were obtained in most of the test cases; these required only short computational times due to the relative efficiency of the basic method.
DEFF Research Database (Denmark)
Knoop, Hans Henrik
2006-01-01
FLOW. Orden i hovedet på den fede måde Oplevelsesmæssigt er flow-tilstanden kendetegnet ved at man er fuldstændig involveret, fokuseret og koncentreret; at man oplever stor indre klarhed ved at vide hvad der skal gøres, og i hvilket omfang det lykkes; at man ved at det er muligt at løse opgaven...
Fast Multilevel Panel Method for Wind Turbine Rotor Flow Simulations
van Garrel, Arne; Venner, Cornelis H.; Hoeijmakers, Hendrik Willem Marie
2017-01-01
A fast multilevel integral transform method has been developed that enables the rapid analysis of unsteady inviscid flows around wind turbines rotors. A low order panel method is used and the new multi-level multi-integration cluster (MLMIC) method reduces the computational complexity for
On Howard's conjecture in heterogeneous shear flow problem
Indian Academy of Sciences (India)
M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22
This conjecture of Howard has also drawn the attention of researchers. Banerjee et al [1] were able to validate the correctness of this conjecture for the special case of inviscid homogeneous parallel shear flows. Their approach consisted of combining the governing equations and boundary conditions in an innovative way ...
A physical five-equation model for compressible two-fluid flow, and its numerical treatment
J.J. Kreeft (Jasper); B. Koren (Barry)
2009-01-01
htmlabstractA novel five-equation model for inviscid, non-heat-conducting, compressible two-fluid flow is derived, together with an appropriate numerical method. The model uses flow equations based on conservation laws and exchange laws only. The two fluids exchange momentum and energy, for which
A compressible Navier-Stokes code for turbulent flow modeling
Coakley, T. J.
1984-01-01
An implicit, finite volume code for solving two dimensional, compressible turbulent flows is described. Second order upwind differencing of the inviscid terms of the equations is used to enhance stability and accuracy. A diagonal form of the implicit algorithm is used to improve efficiency. Several zero and two equation turbulence models are incorporated to study their impact on overall flow modeling accuracy. Applications to external and internal flows are discussed.
Strongly coupled interaction between a ridge of fluid and an inviscid airflow
Paterson, C.
2015-07-01
© 2015 AIP Publishing LLC. The behaviour of a steady thin sessile or pendent ridge of fluid on an inclined planar substrate which is strongly coupled to the external pressure gradient arising from an inviscid airflow parallel to the substrate far from the ridge is described. When the substrate is nearly horizontal, a very wide ridge can be supported against gravity by capillary and/or external pressure forces; otherwise, only a narrower (but still wide) ridge can be supported. Classical thin-aerofoil theory is adapted to obtain the governing singular integro-differential equation for the profile of the ridge in each case. Attention is focused mainly on the case of a very wide sessile ridge. The effect of strengthening the airflow is to push a pinned ridge down near to its edges and to pull it up near to its middle. At a critical airflow strength, the upslope contact angle reaches the receding contact angle at which the upslope contact line de-pins, and continuing to increase the airflow strength beyond this critical value results in the de-pinned ridge becoming narrower, thicker, and closer to being symmetric in the limit of a strong airflow. The effect of tilting the substrate is to skew a pinned ridge in the downslope direction. Depending on the values of the advancing and receding contact angles, the ridge may first de-pin at either the upslope or the downslope contact line but, in general, eventually both contact lines de-pin. The special cases in which only one of the contact lines de-pins are also considered. It is also shown that the behaviour of a very wide pendent ridge is qualitatively similar to that of a very wide sessile ridge, while the important qualitative difference between the behaviour of a very wide ridge and a narrower ridge is that, in general, for the latter one or both of the contact lines may never de-pin.
Numerical Investigation of unsteady inlet flow fields
Hsieh, T.; Wardlaw, A. B., Jr.; Collins, P.; Coakley, T.
1984-01-01
The flow field within an unsteady, two-dimensional inlet is studied numerically, using a two dimensional Navier Stokes and a one-dimensional inviscid model. Unsteadiness is introduced by varying the outflow pressure boundary condition. The cases considered include outflow pressure variations which were a single pressure pulse, a rapid increase and a sine function. The amplitude of the imposed exit plane pressure disturbance varied between 1 percent and 20 percent of the mean exit pressure. At the higher levels of pressure fluctuation, the viscous flow field results bore little resemblance to the inviscid ones. The viscous solution included such phenomena as shock trains and bifurcating separation pockets. The induced velocity at the outflow plane predicted by the viscous model differs significantly from accoustical theory or small perturbation results.
Energy Technology Data Exchange (ETDEWEB)
Fialova, M.; Fuerst, J.; Horak, J.; Kozel, K. [Czech Technical Univ., Faculty of Mechanical Engineering, Dept. of Technical Mathematics, Prague (Czech Republic)
1997-12-31
The work deals with numerical solution of 2D and 3D transonic flows using mathematical models of Euler and Navier-Stokes equations. For inviscid flows with a shock wave we tested modern TVD upwind and central methods. For computations of 2D and 3D compressible viscous laminar flows multistage Runge-Kutta methods were used. (orig.)
Mulac, Richard A.; Celestina, Mark L.; Adamczyk, John J.; Misegades, Kent P.; Dawson, Jef M.
1987-01-01
A procedure is outlined which utilizes parallel processing to solve the inviscid form of the average-passage equation system for multistage turbomachinery along with a description of its implementation in a FORTRAN computer code, MSTAGE. A scheme to reduce the central memory requirements of the program is also detailed. Both the multitasking and I/O routines referred to in this paper are specific to the Cray X-MP line of computers and its associated SSD (Solid-state Storage Device). Results are presented for a simulation of a two-stage rocket engine fuel pump turbine.
Mulac, Richard A.; Celestina, Mark L.; Adamczyk, John J.; Misegades, Kent P.; Dawson, Jef M.
1987-01-01
A procedure is outlined which utilizes parallel processing to solve the inviscid form of the average-passage equation system for multistage turbomachinery along with a description of its implementation in a FORTRAN computer code, MSTAGE. A scheme to reduce the central memory requirements of the program is also detailed. Both the multitasking and I/O routines referred to are specific to the Cray X-MP line of computers and its associated SSD (Solid-State Disk). Results are presented for a simulation of a two-stage rocket engine fuel pump turbine.
International Nuclear Information System (INIS)
Hernandez-Walls, R; Martín-Atienza, B; Salinas-Matus, M; Castillo, J
2017-01-01
When solving the linear inviscid shallow water equations with variable depth in one dimension using finite differences, a tridiagonal system of equations must be solved. Here we present an approach, which is more efficient than the commonly used numerical method, to solve this tridiagonal system of equations using a recursion formula. We illustrate this approach with an example in which we solve for a rectangular channel to find the resonance modes. Our numerical solution agrees very well with the analytical solution. This new method is easy to use and understand by undergraduate students, so it can be implemented in undergraduate courses such as Numerical Methods, Lineal Algebra or Differential Equations. (paper)
Remark on numerical simulation of 2D unsteady transonic flows
Foŕt, J.; Hülek, T.; Kozel, K.; Vavrincová, M.
The work deals with three numerical methods solving the system of Euler or Navier-Stokes equations. Mac Cormack cell centered and Ni cell vertex finite volume schemes were used for simulation of inviscid unsteady solution of transonic flows through a 2D cascade. Unsteady motion is caused by a periodic change of downstream pressure. The Runge-Kutta multistage cell centered finite volume scheme has been used for viscous laminar steady and unsteady transonic flows over NACA 0012.
Applications of Taylor-Galerkin finite element method to compressible internal flow problems
Sohn, Jeong L.; Kim, Yongmo; Chung, T. J.
1989-01-01
A two-step Taylor-Galerkin finite element method with Lapidus' artificial viscosity scheme is applied to several test cases for internal compressible inviscid flow problems. Investigations for the effect of supersonic/subsonic inlet and outlet boundary conditions on computational results are particularly emphasized.
Simulation of flow structure in the suction pipe of a hydroturbine by integral characteristics
DEFF Research Database (Denmark)
Kuibin, P.A.; Okulov, Valery; Pylev, I.M.
2006-01-01
Within the framework of a model of a twisted flow of an inviscid incompressible liquid, we solve the problem of determining the frequency and amplitude of oscillations caused by the precession of a helical vortex core in the suction tube of a hydroturbine from the specified integral characteristics...
Numerical Simulation of 2D Transonic Flows in DCA 8% Cascade
Directory of Open Access Journals (Sweden)
Příhoda Jaromír
2013-04-01
Full Text Available This work deals with a numerical simulation of 2D inviscid and laminar compressible flows in the DCA 8% cascade achieved by the FVM using a multistage Runge-Kutta method and Lax-Wendroff scheme (Richtmyer form with an artificial dissipation on non-orthogonal structured grids. The results are discussed and compared with other similar ones and experiment.
Numerical Simulation of 2D Transonic Flows in DCA 8% Cascade
Huml, Jaroslav; Kozel, Karel; Příhoda, Jaromír
2013-04-01
This work deals with a numerical simulation of 2D inviscid and laminar compressible flows in the DCA 8% cascade achieved by the FVM using a multistage Runge-Kutta method and Lax-Wendroff scheme (Richtmyer form) with an artificial dissipation on non-orthogonal structured grids. The results are discussed and compared with other similar ones and experiment.
A model for closing the inviscid form of the average passage equation system
Adamczyk, John J.; Mulac, R. A.; Celestina, M. L.
1996-01-01
A mathematical model for closing or mathematically completing the system of equations is proposed. The model describes the time average flow field through the blade passages of multistage turbomachinery. These average-passage equation systems govern a conceptual model useful in turbomachinery aerodynamic design and analysis. The closure model was developed to insure a consistency between these equations and the axisymmetric through-flow equations. The closure model was incorporated into a calculation code for use in the simulation of the flow field about a high-speed counter rotating propeller and a high-speed fan stage.
A model for closing the inviscid form of the average-passage equation system
Adamczyk, J. J.; Mulac, R. A.; Celestina, M. L.
1986-01-01
A mathematical model is proposed for closing or mathematically completing the system of equations which describes the time average flow field through the blade passages of multistage turbomachinery. These equations referred to as the average passage equation system govern a conceptual model which has proven useful in turbomachinery aerodynamic design and analysis. The closure model is developed so as to insure a consistency between these equations and the axisymmetric through flow equations. The closure model was incorporated into a computer code for use in simulating the flow field about a high speed counter rotating propeller and a high speed fan stage. Results from these simulations are presented.
Directory of Open Access Journals (Sweden)
R. Selvamani
2016-01-01
Full Text Available Wave propagation in a transversely isotropic magneto-electro-elastic solid bar immersed in an inviscid fluid is discussed within the frame work of linearized three dimensional theory of elasticity. Three displacement potential functions are introduced to uncouple the equations of motion, electric and magnetic induction. The frequency equations that include the interaction between the solid bar and fluid are obtained by the perfect slip boundary conditions using the Bessel functions. The numerical calculations are carried out for the non-dimensional frequency, phase velocity and attenuation coefficient by fixing wave number and are plotted as the dispersion curves. The results reveal that the proposed method is very effective and simple and can be applied to other bar of different cross section by using proper geometric relation.
International Nuclear Information System (INIS)
Constantin, P.; Wu, J.
1997-01-01
Using the methods of Foias [Sem. Math. Univ. Padova 48, 219 endash 343 (1972); 49, 9 endash 123 (1973)] and Vishik endash Fursikov [Mathematical Problems of Statistical Hydromechanics (Kluwer, Dordrecht, 1988)], we prove the existence and uniqueness of both spatial and space endash time statistical solutions of the Navier endash Stokes equations on the phase space of vorticity. Here the initial vorticity is in Yudovich space and the initial measure has finite mean enstrophy. We show under further assumptions on the initial vorticity that the statistical solutions of the Navier endash Stokes equations converge weakly and the inviscid limits are the corresponding statistical solutions of the Euler equations. copyright 1997 American Institute of Physics
Studies of vortex dominated flows; Proceedings of the Symposium, Hampton, VA, July 9-11, 1985
International Nuclear Information System (INIS)
Hussaini, M.Y.; Salas, M.D.
1987-01-01
Papers are presented on waves and bifurcations in vortex filaments, a ring-vortex representation of an axisymmetric vortex sheet, and comparison of experiment with the dynamics of the von Karman vortex trail. Also considered are force-free and loss-free transitions between vortex flow states, a vortex breakdown simulation based on a nonlinear inviscid method, and the prediction of highly vortical flows using an Euler equation model. Other topics include the theory of high-Reynolds-number flow past a blunt body, progress on the calculation of large-scale separation at high Reynolds numbers, and viscous-inviscid interaction solvers and computation of highly separated flows. Papers are also presented on simulation studies of vortex dynamics of a leading edge vortex flap, methods for numerical simulation of leading edge vortex flow, and comparison of measured and computed pitot pressures in a leading edge vortex from a delta wing
Algorithm For Hypersonic Flow In Chemical Equilibrium
Palmer, Grant
1989-01-01
Implicit, finite-difference, shock-capturing algorithm calculates inviscid, hypersonic flows in chemical equilibrium. Implicit formulation chosen because overcomes limitation on mathematical stability encountered in explicit formulations. For dynamical portion of problem, Euler equations written in conservation-law form in Cartesian coordinate system for two-dimensional or axisymmetric flow. For chemical portion of problem, equilibrium state of gas at each point in computational grid determined by minimizing local Gibbs free energy, subject to local conservation of molecules, atoms, ions, and total enthalpy. Major advantage: resulting algorithm naturally stable and captures strong shocks without help of artificial-dissipation terms to damp out spurious numerical oscillations.
An interactive boundary layer modelling methodology for aerodynamic flows
CSIR Research Space (South Africa)
Smith, L
2013-01-01
Full Text Available -of-boundary layer flow, with the inviscid flow approximation: Continuity 0= ∂ ∂ j j u x ρ (1) Conservation of momentum (Newton’s second law) ( ) ( ) ∂ ∂ − ∂ ∂ + ∂ ∂ ∂ ∂ += ∂ ∂ + ∂ ∂ + ∂ ∂ ij k k i j j i j i i ji j i...-integral boundary layer solutions to a generic inviscid solver in an iterative fashion. Design/methodology/approach –The boundary layer solution is obtained using the two-integral method to solve displacement thickness point by point with a local Newton method...
Heat transfer characteristics of alkali metals flowing across tube banks
International Nuclear Information System (INIS)
Sugiyama, K.; Ishiguro, R.; Kojima, Y.; Kanaoka, H.
2004-01-01
For the purpose of getting heat transfer coefficients of alkali metals flowing across tube banks at an acceptable level, we propose to use an inviscid-irrotational flow model, which is based on our flow visualization experiment. We show that the heat transfer coefficients obtained for the condition where only the test rod is heated in tube banks considerably differ from those obtained for the condition where all the rods are heated, because of interference between thick thermal boundary layers of alkali metals. We also confirm that the analytical values obtained by this flow model are in a reasonable agreement with experimental values. (author)
Early Regimes of Water Capillary Flow in Slit Silica Nanochannels
DEFF Research Database (Denmark)
Oyarzua, Elton; Walther, Jens Honore; Mejia, Andres
2015-01-01
on the dynamics of capillaryfilling. The results indicate that the nanoscale imbibition process is divided into three main flow regimes:an initial regime where the capillary force is balanced only by the inertial drag and characterized by aconstant velocity and a plug flow profile. In this regime, the meniscus...... velocity profiles identify the passage froman inviscid flow to a developing Poiseuille flow. Gas density profiles ahead of the capillary front indicatea transient accumulation of air on the advancing meniscus. Furthermore, slower capillary filling ratescomputed for higher air pressures reveal a significant...... retarding effect of the gas displaced by the advancing meniscus....
Basic numerical methods. [of unsteady and transonic flow
Steger, Joseph L.; Van Dalsem, William R.
1989-01-01
Some of the basic finite-difference schemes that can be used to solve the nonlinear equations that describe unsteady inviscid and viscous transonic flow are reviewed. Numerical schemes for solving the unsteady Euler and Navier-Stokes, boundary-layer, and nonlinear potential equations are described. Emphasis is given to the elementary ideas used in constructing various numerical procedures, not specific details of any one procedure.
Agopian, K. G.
1974-01-01
The problem of inviscid, steady transonic conical flow, formulated in terms of the small disturbance theory, is studied. The small disturbance equation and similarity rules are presented, and a boundary value problem is formulated for the case of a supersonic freestream Mach number. The equation for the perturbation potential is solved numerically using an elliptic finite difference system. The difference equations are solved with a point relaxation algorithm that is also capable of capturing the shock wave during the iteration procedure by using the boundary conditions at the shock. Numerical calculations, for shock location, pressure distribution and drag coefficient, are presented for a family of nonlifting conical wings. The theory of slender wings is also presented and analytical results for pressure and drag coefficients are obtained.
Assessment of modern methods in numerical simulations of high speed flows
Pindera, M. Z.; Yang, H. Q.; Przekwas, A. J.; Tucker, K.
1992-01-01
Results of extensive studies on CFD algorithms for 2D inviscid flows in Cartesian and body fitted coordinates geometries are reviewed. These studies represent part of an ongoing investigation of combustion instabilities involving the interactions of high-speed nonlinear acoustic waves. Four numerical methods for the treatment of high speed flows are compared, namely, Roe-Sweby TVD, Yee symmetric TVD; Osher-Chakravarthy TVD; and the Colella's multi-dimensional Godunov method.
A missed persistence property for the Euler equations and its effect on inviscid limits
International Nuclear Information System (INIS)
Veiga, H Beirão da; Crispo, F
2012-01-01
We consider the problem of strong convergence, as the viscosity goes to zero, of the solutions to the three-dimensional evolutionary Navier–Stokes equations, under the Navier slip-type boundary condition (1.4), to the solution of the Euler equations under the no-penetration condition. In two dimensions, the above strong convergence holds in any smooth domain. Furthermore, in three dimensions, arbitrarily strong convergence results hold in the half-space case. In spite of the above results, recently we presented an explicit family of smooth initial data in the 3D sphere, for which the result fails. The result was proved as a by-product of the lack of time persistency for the above boundary condition under the Euler flow. Our aim here is to show a more general, and simpler proof, displayed in arbitrary, smooth domains
An Engineering Aerodynamic Heating Method for Hypersonic Flow
Riley, Christopher J.; DeJarnette, Fred R.
1992-01-01
A capability to calculate surface heating rates has been incorporated in an approximate three-dimensional inviscid technique. Surface streamlines are calculated from the inviscid solution, and the axisymmetric analog is then used along with a set of approximate convective-heating equations to compute the surface heat transfer. The method is applied to blunted axisymmetric and three-dimensional ellipsoidal cones at angle of attack for the laminar flow of a perfect gas. The method is also applicable to turbulent and equilibrium-air conditions. The present technique predicts surface heating rates that compare favorably with experimental (ground-test and flight) data and numerical solutions of the Navier-Stokes (NS) and viscous shock-layer (VSL) equations. The new technique represents a significant improvement over current engineering aerothermal methods with only a modest increase in computational effort.
A finite element formulation of Euler equations for the solution of steady transonic flows
Ecer, A.; Akay, H. U.
1982-01-01
The main objective of the considered investigation is related to the development of a relaxation scheme for the analysis of inviscid, rotational, transonic flow problems. To formulate the equations of motion for inviscid flows in a fixed coordinate system, an Eulerian type variational principle is required. The derivation of an Eulerian variational principle which is employed in the finite element formulation is discussed. The presented numerical method describes the mathematical formulation and the application of a numerical process for the direct solution of steady Euler equations. The development of the procedure as an extension of existing potential flow formulations provides the applicability of previous procedures, e.g., proper application of the artificial viscosity for supersonic elements, and the accurate modeling of the shock.
Grossman, B.; Garrett, J.; Cinnella, P.
1989-01-01
Several versions of flux-vector split and flux-difference split algorithms were compared with regard to general applicability and complexity. Test computations were performed using curve-fit equilibrium air chemistry for an M = 5 high-temperature inviscid flow over a wedge, and an M = 24.5 inviscid flow over a blunt cylinder for test computations; for these cases, little difference in accuracy was found among the versions of the same flux-split algorithm. For flows with nonequilibrium chemistry, the effects of the thermodynamic model on the development of flux-vector split and flux-difference split algorithms were investigated using an equilibrium model, a general nonequilibrium model, and a simplified model based on vibrational relaxation. Several numerical examples are presented, including nonequilibrium air chemistry in a high-temperature shock tube and nonequilibrium hydrogen-air chemistry in a supersonic diffuser.
Choquard, Ph.; Vuffray, M.
2014-10-01
The coupling between dilatation and vorticity, two coexisting and fundamental processes in fluid dynamics (Wu et al., 2006, pp. 3, 6) is investigated here, in the simplest cases of inviscid 2D isotropic Burgers and pressureless Euler-Coriolis fluids respectively modeled by single vortices confined in compressible, local, inertial and global, rotating, environments. The field equations are established, inductively, starting from the equations of the characteristics solved with an initial Helmholtz decomposition of the velocity fields namely a vorticity free and a divergence free part (Wu et al., 2006, Sects. 2.3.2, 2.3.3) and, deductively, by means of a canonical Hamiltonian Clebsch like formalism (Clebsch, 1857, 1859), implying two pairs of conjugate variables. Two vector valued fields are constants of the motion: the velocity field in the Burgers case and the momentum field per unit mass in the Euler-Coriolis one. Taking advantage of this property, a class of solutions for the mass densities of the fluids is given by the Jacobian of their sum with respect to the actual coordinates. Implementation of the isotropy hypothesis entails a radial dependence of the velocity potentials and of the stream functions associated to the compressible and to the rotational part of the fluids and results in the cancellation of the dilatation-rotational cross terms in the Jacobian. A simple expression is obtained for all the radially symmetric Jacobians occurring in the theory. Representative examples of regular and singular solutions are shown and the competition between dilatation and vorticity is illustrated. Inspired by thermodynamical, mean field theoretical analogies, a genuine variational formula is proposed which yields unique measure solutions for the radially symmetric fluid densities investigated. We stress that this variational formula, unlike the Hopf-Lax formula, enables us to treat systems which are both compressible and rotational. Moreover in the one
International Nuclear Information System (INIS)
Koffi-Kpante, Kossi
1996-01-01
Inviscid flow of the N 2 -CH 4 -Ar gas mixture in thermochemical nonequilibrium has been studied. We have specially modelled the thermal and the chemical processes, such as vibrational excitation, dissociation, ionization and radiation which can occur in the hypersonic flows. Different vibrational models are tested and the effects of kinetic-vibration coupling modeling are studied on the flow-field properties. Therefore, the intensity of spontaneous emission of CN molecule from B 2 Σ + → X 2 Σ + electronic transition of the violet band, where Δν = 0 is computed. So, comparison is made between experimental and numerical results on: 1) The spontaneous emission of CN, 2) the rotational temperature of CN B state and 3) the vibrational temperature of CN B state. Because of the profiles of the measured intensity and the disagreement between numerical results and measurements, especially on the spontaneous emission and in the thermodynamic size, the inviscid flow and the unsteady boundary layer interaction study is made. Last, the thermal and the chemical processes models described in the first part of this thesis are used to compute the inviscid nonequilibrium flow around the Huygens probe. The equations system has been solved with a finite volume method, in with the fluxes have been split with Van-Leer methods. (author) [fr
A waveless two-dimensional flow in a channel against an inclined wall with surface tension effect
International Nuclear Information System (INIS)
Merzougui, Abdelkrim; Mekias, Hocine; Guechi, Fairouz
2007-01-01
Surface tension effect on a two-dimensional channel flow against an inclined wall is considered. The flow is assumed to be steady, irrotational, inviscid and incompressible. The effect of surface tension is taken into account and the effect of gravity is neglected. Numerical solutions are obtained via series truncation procedure. The problem is solved numerically for various values of the Weber number α and for various values of the inclination angle β between the horizontal bottom and the inclined wall
Hamilton, H. H., II; Spall, J. R.
1986-01-01
A time-asymptotic method has been used to obtain steady-flow solutions for axisymmetric inviscid flow over several blunt bodies including spheres, paraboloids, ellipsoids, and spherically blunted cones. Comparisons with experimental data and results of other computational methods have demonstrated that accurate solutions can be obtained using this approach. The method should prove useful as an analysis tool for comparing with experimental data and for making engineering calculations for blunt reentry vehicles.
Nonlinear evolution of layered stratified shear flows
Lee, Victoria; Caulfield, Colm-Cille
2000-11-01
We investigate numerically and theoretically the nonlinear evolution of a parallel shear flow at moderate Reynolds number which has embedded within it a mixed layer of intermediate fluid. Linear stability theory predicts that such flows are unstable to stationary vortical disturbances which are a generalization of an inviscid instability first considered by G. I. Taylor. We investigate the behaviour of these Taylor modes at finite amplitude through numerical simulations. Through considering the long-time evolution of such flows, we investigate how secondary instabilities, and the layered background density profile, affect merging between neighbouring Taylor billows, and alter the irreversible mixing of the background stratification as the flow undergoes transition to small-scale disorder.
Ultrasonically Absorptive Coatings for Hypersonic Laminar Flow Control
2007-12-01
6.25) In this case, we have OF/Oxj << OF’/Ox, . Substituting the decompositions (6.24) into the exact Navier - Stockes equations, using approximate...the wall temperature is T = 297.28 K. The local flow parameters (at the upper boundary-layer edge) are determined from the Navier -Stokes solution for...predicted by the Navier -Stokes solver (Figs. 1.6 and 1.7); i.e., the viscous-inviscid interaction weakly affects the boundary-layer mean flow. R Mn 22
Fluid Mechanics of Inhalant Siphon Flows
True, A. C.; Crimaldi, J. P.
2016-02-01
Inhalant siphon and suction flows are ubiquitous in marine ecosystems. From biological flows in filter-feeding benthic bivalves and predation by planktivorous fishes, to engineered flows in water samplers and production of hydrodynamic stimuli for laboratory assays, inhalant siphon flows span much of the laminar range (Reynolds number 0.01 - 2,000) and fundamentally influence many transport and exchange processes. Direct numerical simulations (DNS) of inhalant siphon flows with varying Reynolds numbers and geometries have informed design and construction of an index of refraction-matched flow facility (mineral oil, borosilicate glass tubing) in which we are employing particle image velocimetry (PIV) to quantify transient and steady-state flow fields outside and inside the siphon tube. Varying siphon diameter, flow rate, and extraction height allows us to evaluate effects of Reynolds number and siphon geometry on local hydrodynamics. This complementary experimental and numerical modeling investigation of siphon flow hydrodynamics was motivated recently by a colleague whose biologically inspired numerical modeling of inhalant siphons using a boundary condition of constant volumetric outflow (as opposed to the classically assumed uniform inlet velocity profile) revealed nontrivial departures from idealized flows: inviscid potential flows (i.e. point sink) and pipe flows (the classical pipe entry problem), particularly in the low Reynolds number regime. Reduced entrance lengths, larger radial inflows, and modifications to fluid capture zones seen numerically at low Reynolds number are being tested experimentally and may have important implications for both biological and engineered siphons.
Numerical solution of subsonic and transonic flows in 2D and 3D
Huml, Jaroslav; Kozel, Karel
2014-03-01
This work deals with a numerical simulation of 2D and 3D inviscid and laminar compressible flows around a DCA 18% profile. Numerical results were achieved on non-orthogonal structured grids by the authors' in-home code with an implemented FVM multistage Runge-Kutta method and an artificial dissipation. The results are discussed and compared with other similar ones (e.g. the results by G. S. Deiwert).
Numerical solution of subsonic and transonic flows in 2D and 3D
Directory of Open Access Journals (Sweden)
Huml Jaroslav
2014-03-01
Full Text Available This work deals with a numerical simulation of 2D and 3D inviscid and laminar compressible flows around a DCA 18% profile. Numerical results were achieved on non-orthogonal structured grids by the authors’ in-home code with an implemented FVM multistage Runge-Kutta method and an artificial dissipation. The results are discussed and compared with other similar ones (e.g. the results by G. S. Deiwert.
Stability and suppression of turbulence in relaxing molecular gas flows
Grigoryev, Yurii N
2017-01-01
This book presents an in-depth systematic investigation of a dissipative effect which manifests itself as the growth of hydrodynamic stability and suppression of turbulence in relaxing molecular gas flows. The work describes the theoretical foundations of a new way to control stability and laminar turbulent transitions in aerodynamic flows. It develops hydrodynamic models for describing thermal nonequilibrium gas flows which allow the consideration of suppression of inviscid acoustic waves in 2D shear flows. Then, nonlinear evolution of large-scale vortices and Kelvin-Helmholtz waves in relaxing shear flows are studied. Critical Reynolds numbers in supersonic Couette flows are calculated analytically and numerically within the framework of both linear and nonlinear classical energy hydrodynamic stability theories. The calculations clearly show that the relaxation process can appreciably delay the laminar-turbulent transition. The aim of the book is to show the new dissipative effect, which can be used for flo...
DEFF Research Database (Denmark)
van der Horst, Sander; van de Wiel, Jelmer E.; Ferreira, Carlos Simao
2016-01-01
Blades on a Vertical Axis Wind Turbine (VAWT) experience curved streamlines, caused by the rotation of the turbine. This phenomenon is known as flow curvature and has effects on the aerodynamic loading of the blades. Several authors have proposed methods to account for flow curvature, resulting...... errors remain that are intrinsic to the conformal methods used. It is shown that VAWT rotation is equivalent to an eternal pitching motion. Using this similarity, flow curvature modeling has been added to the airfoil analysis tool XFOIL. The various changes have been made in the inviscid solver, in a way...
Lan, C. Edward
1985-01-01
A computer program based on the Quasi-Vortex-Lattice Method of Lan is presented for calculating longitudinal and lateral-directional aerodynamic characteristics of nonplanar wing-body combination. The method is based on the assumption of inviscid subsonic flow. Both attached and vortex-separated flows are treated. For the vortex-separated flow, the calculation is based on the method of suction analogy. The effect of vortex breakdown is accounted for by an empirical method. A summary of the theoretical method, program capabilities, input format, output variables and program job control set-up are described. Three test cases are presented as guides for potential users of the code.
An experimental and analytical study of flow through a supersonic open channel with contoured floor
Saheli, F. P.; Dunn, B.; Marrs, K.; Kumar, A.; Peery, K. M.
1984-01-01
A wind tunnel experiment was performed to study the characteristics of supersonic airflow (M(infinity) = 2.5-3.86) through an open channel with a contoured floor. The measured static pressures along the centerline of the channel floor exhibited an unexpected rise at the end of the channel. Complex three-dimensional interactions of compression and expansion waves within the channel coupled with external flow perturbations caused by model/tunnel wall interference were the suspected sources of this flow behavior. Three-dimensional inviscid flow analysis procedures were used to investigate and explain this phenomenon. The results of the computations and the experiment are presented and discussed.
Flux-split algorithms for flows with non-equilibrium chemistry and vibrational relaxation
Grossman, B.; Cinnella, P.
1990-01-01
The present consideration of numerical computation methods for gas flows with nonequilibrium chemistry thermodynamics gives attention to an equilibrium model, a general nonequilibrium model, and a simplified model based on vibrational relaxation. Flux-splitting procedures are developed for the fully-coupled inviscid equations encompassing fluid dynamics and both chemical and internal energy-relaxation processes. A fully coupled and implicit large-block structure is presented which embodies novel forms of flux-vector split and flux-difference split algorithms valid for nonequilibrium flow; illustrative high-temperature shock tube and nozzle flow examples are given.
Transition and mixing in layered stratified shear flows.
Lee, Victoria; Caulfield, C. P.
2001-11-01
Flows with step-wise density distributions, i.e. well-mixed layers of fluid separated by narrow regions of high density gradient, are common in geophysics. We investigate numerically and theoretically the nonlinear evolution of a parallel shear flow at a moderate Reynolds number which has embedded within it a mixed layer of intermediate fluid. Linear stability theory predicts that the flow may be unstable to stationary vortical disturbances which are a generalization of an inviscid instability first considered by G. I. Taylor. We investigate the behaviour of these "Taylor waves" at finite amplitude through 3D nonlinear numerical simulations. We follow the development of primary and secondary instabilities which contribute to the eventual breakdown of the layered flow. In particular, we are interested in the mixing properties of the flow as it undergoes transition to small-scale disorder.
Parabolized Navier-Stokes solutions of separation and trailing-edge flows
Brown, J. L.
1983-01-01
A robust, iterative solution procedure is presented for the parabolized Navier-Stokes or higher order boundary layer equations as applied to subsonic viscous-inviscid interaction flows. The robustness of the present procedure is due, in part, to an improved algorithmic formulation. The present formulation is based on a reinterpretation of stability requirements for this class of algorithms and requires only second order accurate backward or central differences for all streamwise derivatives. Upstream influence is provided for through the algorithmic formulation and iterative sweeps in x. The primary contribution to robustness, however, is the boundary condition treatment, which imposes global constraints to control the convergence path. Discussed are successful calculations of subsonic, strong viscous-inviscid interactions, including separation. These results are consistent with Navier-Stokes solutions and triple deck theory.
A turbulent two-phase flow model for nebula flows
International Nuclear Information System (INIS)
Champney, J.M.; Cuzzi, J.N.
1990-01-01
A new and very efficient turbulent two-phase flow numericaly model is described to analyze the environment of a protoplanetary nebula at a stage prior to the formation of planets. Focus is on settling processes of dust particles in flattened gaseous nebulae. The model employs a perturbation technique to improve the accuracy of the numerical simulations of such flows where small variations of physical quantities occur over large distance ranges. The particles are allowed to be diffused by gas turbulence in addition to settling under gravity. Their diffusion coefficients is related to the gas turbulent viscosity by the non-dimensional Schmidt number. The gas turbulent viscosity is determined by the means of the eddy viscosity hypothesis that assumes the Reynolds stress tensor proportional to the mean strain rate tensor. Zero- and two-equation turbulence models are employed. Modeling assumptions are detailed and discussed. The numerical model is shown to reproduce an existing analytical solution for the settling process of particles in an inviscid nebula. Results of nebula flows are presented taking into account turbulence effects of nebula flows. Diffusion processes are found to control the settling of particles. 24 refs
Evolution of a Vortex in a Strain Flow
Hurst, N. C.; Danielson, J. R.; Dubin, D. H. E.; Surko, C. M.
2016-12-01
Experiments and vortex-in-cell simulations are used to study an initially axisymmetric, spatially distributed vortex subject to an externally imposed strain flow. The experiments use a magnetized pure electron plasma to model an inviscid two-dimensional fluid. The results are compared to a theory assuming an elliptical region of constant vorticity. For relatively flat vorticity profiles, the dynamics and stability threshold are in close quantitative agreement with the theory. Physics beyond the constant-vorticity model, such as vortex stripping, is investigated by studying the behavior of nonflat vorticity profiles.
Numerical Simulation of Generalized Newtonian Flows in Bypass
Prokop, V.; Kozel, K.
2010-09-01
This paper is concerned with numerical solution of Newtonian and non-Newtonian fluid flows described by the system of basic conservation laws with variable viscosity. Temperature variations are not taken into account. Numerical solution of steady system with steady boundary conditions is in our case based on artificial compressibility method that allows to use time marching method to converge to steady state. Space derivatives are discretized using finite volume method in cell centered formulation. Inviscid fluxes are discretized centrally and computation of viscous fluxes is based on dual finite volubmes.
Oscillatory Stokes Flow Past a Slip Cylinder
Palaniappan, D.
2013-11-01
Two-dimensional transient slow viscous flow past a circular cylinder with Navier slip boundary conditions is considered in the limit of low-Reynolds number. The oscillatory Stokes flow problem around a cylinder is solved using the stream function method leading to an analytic solution in terms of modified Bessel functions of the second kind. The corresponding steady-state behavior yields the familiar paradoxical result first detected by Stokes. It is noted that the two key parameters, viz., the frequency λ, and the slip coefficient ξ have a significant impact on the flow field in the vicinity of the cylinder contour. In the limit of very low frequency, the flow is dominated by a term containing a well-known biharmonic function found by Stokes that has a singular behavior at infinity. Local streamlines for small times show interesting flow patterns. Attached eddies due to flow separation - observed in the no-slip case - either get detached or pushed away from the cylinder surface as ξ is varied. Computed asymptotic results predict that the flow exhibits inviscid behavior far away from the cylinder in the frequency range 0 < λ << 1 . Although the frequency of oscillations is finite, our exact solutions reveal fairly rapid transitions in the flow domain. Research Enhancement grant, TAMUCC.
Linear flow dynamics near a T/NT interface
Teixeira, Miguel; Silva, Carlos
2011-11-01
The characteristics of a suddenly-inserted T/NT interface separating a homogeneous and isotropic shear-free turbulence region from a non-turbulent flow region are investigated using rapid distortion theory (RDT), taking full account of viscous effects. Profiles of the velocity variances, TKE, viscous dissipation rate, turbulence length scales, and pressure statistics are derived, showing very good agreement with DNS. The normalized inviscid flow statistics at the T/NT interface do not depend on the form of the assumed TKE spectrum. In the non-turbulent region, where the flow is irrotational (except within a thin viscous boundary layer), the dissipation rate decays as z-6, where z is distance from the T/NT interface. The mean pressure exhibits a decrease towards the turbulence due to the associated velocity fluctuations, consistent with the generation of a mean entrainment velocity. The vorticity variance and dissipation rate display large maxima at the T/NT interface due to the existing inviscid discontinuities of the tangential velocity, and these maxima are quantitatively related to the thickness of the viscous boundary layer (VBL). At equilibrium, RDT suggests that the thickness of the T/NT interface scales on the Kolmogorov microscale. We acknowledge the financial support of FCT under Project PTDC/EME-MFE/099636/2008.
Flow Modelling for partially Cavitating Two-dimensional Hydrofoils
DEFF Research Database (Denmark)
Krishnaswamy, Paddy
2001-01-01
The present work addresses te computational analysis of partial sheet hydrofoil cavitation in two dimensions. Particular attention is given to the method of simulating the flow at the end of the cavity. A fixed-length partially cavitating panel method is used to predict the height of the re...... of the model and comparing the present calculations with numerical results. The flow around the partially cavitating hydrofoil with a re-entrant jet has also been treated with a viscous/inviscid interactive method. The viscous flow model is based on boundary layer theory applied on the compound foil......, consisting of the union of the cavity and the hydrofoil surface. The change in the flow direction in the cavity closure region is seen to have a slightly adverse effect on the viscous pressure distribution. Otherwise, it is seen that the viscous re-entrant jet solution compares favourably with experimental...
Numerical simulation of steady and unsteady flows through plane cascades
Fořt, J.; Huněk, M.; Kozel, K.; Lain, J.; Šejna, M.; Vavřincová, M.
This paper of a few co-authors presents some works of the group of the Department of Technical Mathematics, Faculty of Mechanical Eng., TU Prague, which deals with numerical methods in fluid dynamics. We present numerical methods for a solution of different physical and mathematical models of flow through plane cascades. We use the Mac Cormack's scheme, Ron — Ho — Ni's scheme and Runge — Kutta schemes on H — type structured grid and upwind schemes on an unstructured triangular grid. This methods are used for simulation of steady or unsteady inviscid flow and for simulation of viscous laminar flow. We deal with comparison of different methods mutually and with experimental data and with comparison of different physical and mathematical models of flow used for numerical simulation.
Shuen, Jian-Shun; Liou, Meng-Sing; Van Leer, Bram
1989-01-01
The extension of the known flux-vector and flux-difference splittings to real gases via rigorous mathematical procedures is demonstrated. Formulations of both equilibrium and finite-rate chemistry for real-gas flows are described, with emphasis on derivations of finite-rate chemistry. Split-flux formulas from other authors are examined. A second-order upwind-based TVD scheme is adopted to eliminate oscillations and to obtain a sharp representation of discontinuities.
Positivity-preserving space-time CE/SE scheme for high speed flows
Shen, Hua
2017-03-02
We develop a space-time conservation element and solution element (CE/SE) scheme using a simple slope limiter to preserve the positivity of the density and pressure in computations of inviscid and viscous high-speed flows. In general, the limiter works with all existing CE/SE schemes. Here, we test the limiter on a central Courant number insensitive (CNI) CE/SE scheme implemented on hybrid unstructured meshes. Numerical examples show that the proposed limiter preserves the positivity of the density and pressure without disrupting the conservation law; it also improves robustness without losing accuracy in solving high-speed flows.
Numerical calculations of 2D transonic flow in GAMM channel and over the profile
Directory of Open Access Journals (Sweden)
Slouka Martin
2017-01-01
Full Text Available The aim of this work is to make a 2D numerical model of the solution of the transonic inviscid and viscous compressible flow around the profile. In a case of viscous flow several turbulent models are used. For the verification of the calculation Baldwin-Lomax model is compared with Wilcox k-omega model and SST turbulent model. Calculations are done in GAMM channel computational domain with 10% DCA profile and in the turbine cascade computational domain with 8% DCA profile. Numerical methods are based on a finite volume solution. Comparisons are done with the experimental data for the 8% DCA profile.
Numerical calculations of 2D transonic flow in GAMM channel and over the profile
Slouka, Martin; Kozel, Karel
The aim of this work is to make a 2D numerical model of the solution of the transonic inviscid and viscous compressible flow around the profile. In a case of viscous flow several turbulent models are used. For the verification of the calculation Baldwin-Lomax model is compared with Wilcox k-omega model and SST turbulent model. Calculations are done in GAMM channel computational domain with 10% DCA profile and in the turbine cascade computational domain with 8% DCA profile. Numerical methods are based on a finite volume solution. Comparisons are done with the experimental data for the 8% DCA profile.
Solutions to the linearized Navier-Stokes equations for channel flow via the WKB approximation
Leonard, Anthony
2017-11-01
Progress on determining semi-analytical solutions to the linearized Navier-Stokes equations for incompressible channel flow, laminar and turbulent, is reported. Use of the WKB approximation yields, e.g., solutions to initial-value problem for the inviscid Orr-Sommerfeld equation in terms of the Bessel functions J+ 1 / 3 ,J- 1 / 3 ,J1 , and Y1 and their modified counterparts for any given wave speed c = ω /kx and k⊥ ,(k⊥2 =kx2 +kz2) . Of particular note to be discussed is a sequence i = 1 , 2 , . . . of homogeneous inviscid solutions with complex k⊥ i for each speed c, (0 < c <=Umax), in the downstream direction. These solutions for the velocity component normal to the wall v are localized in the plane parallel to the wall. In addition, for limited range of negative c, (- c * <= c <= 0) , we have found upstream-traveling homogeneous solutions with real k⊥(c) . In both cases the solutions for v serve as a source for corresponding solutions to the inviscid Squire equation for the vorticity component normal to the wall ωy.
Spatial linear flows of finite length with nonuniform intensity distribution
Directory of Open Access Journals (Sweden)
Mikhaylov Ivan Evgrafovich
2014-02-01
Full Text Available Irrotational flows produced by spatial linear flows of finite length with different uneven lows of discharge over the flow length are represented in cylindrical coordinate system. Flows with the length 2a are placed in infinite space filled with ideal (inviscid fluid. In “А” variant discharge is fading linearly downward along the length of the flow. In “B” variant in upper half of the flow (length a discharge is fading linearly downward, in lower half of the flow discharge is fading linearly from the middle point to lower end. In “C” variant discharge of the flow is growing linearly from upper and lower ends to middle point.Equations for discharge distribution along the length of the flow are provided for each variant. Equations consist of two terms and include two dimensional parameters and current coordinate that allows integrating on flow length. Analytical expressions are derived for speed potential functions and flow speed components for flow speeds produced by analyzed flows. These analytical expressions consist of dimensional parameters of discharge distribution patterns along the length of the flow. Flow lines equation (meridional sections of flow surfaces for variants “A”, “B”, “C” is unsolvable in quadratures. Flow lines plotting is proposed to be made by finite difference method. Equations for flow line plotting are provided for each variant. Calculations of these equations show that the analyzed flows have the following flow lines: “A” has confocal hyperbolical curves, “B” and “C” have confocal hyperboles. Flow surfaces are confocal hyperboloids produced by rotation of these hyperboles about the axis passing through the flows. In “A” variant the space filled with fluid is separated by vividly horizontal flow surface in two parts. In upper part that includes the smaller part of the flow length flow lines are oriented downward, in lower part – upward. The equation defining coordinate of
Geometry of thin liquid sheet flows
Chubb, Donald L.; Calfo, Frederick D.; Mcconley, Marc W.; Mcmaster, Matthew S.; Afjeh, Abdollah A.
1994-01-01
Incompresible, thin sheet flows have been of research interest for many years. Those studies were mainly concerned with the stability of the flow in a surrounding gas. Squire was the first to carry out a linear, invicid stability analysis of sheet flow in air and compare the results with experiment. Dombrowski and Fraser did an experimental study of the disintegration of sheet flows using several viscous liquids. They also detected the formulation of holes in their sheet flows. Hagerty and Shea carried out an inviscid stability analysis and calculated growth rates with experimental values. They compared their calculated growth rates with experimental values. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. Brown experimentally investigated thin liquid sheet flows as a method of application of thin films. Clark and Dumbrowski carried out second-order stability analysis for invicid sheet flows. Lin introduced viscosity into the linear stability analysis of thin sheet flows in a vacuum. Mansour and Chigier conducted an experimental study of the breakup of a sheet flow surrounded by high-speed air. Lin et al. did a linear stability analysis that included viscosity and a surrounding gas. Rangel and Sirignano carried out both a linear and nonlinear invisid stability analysis that applies for any density ratio between the sheet liquid and the surrounding gas. Now there is renewed interest in sheet flows because of their possible application as low mass radiating surfaces. The objective of this study is to investigate the fluid dynamics of sheet flows that are of interest for a space radiator system. Analytical expressions that govern the sheet geometry are compared with experimental results. Since a space radiator will operate in a vacuum, the analysis does not include any drag force on the sheet flow.
Steady flow in a rotating sphere with strong precession
Kida, Shigeo
2018-04-01
The steady flow in a rotating sphere is investigated by asymptotic analysis in the limit of strong precession. The whole spherical body is divided into three regions in terms of the flow characteristics: the critical band, which is the close vicinity surrounding the great circle perpendicular to the precession axis, the boundary layer, which is attached to the whole sphere surface and the inviscid region that occupies the majority of the sphere. The analytic expressions, in the leading order of the asymptotic expansion, of the velocity field are obtained in the former two, whereas partial differential equations for the velocity field are derived in the latter, which are solved numerically. This steady flow structure is confirmed by the corresponding direct numerical simulation.
Bistable flows in precessing spheroids
Energy Technology Data Exchange (ETDEWEB)
Cébron, D, E-mail: david.cebron@ujf-grenoble.fr [Université Grenoble Alpes, CNRS, ISTerre, Grenoble (France)
2015-04-15
Precession driven flows are found in any rotating container filled with liquid, when the rotation axis itself rotates about a secondary axis that is fixed in an inertial frame of reference. Because of its relevance for planetary fluid layers, many works consider spheroidal containers, where the uniform vorticity component of the bulk flow is reliably given by the well-known equations obtained by Busse (1968 J. Fluid Mech. 33 739–51). So far however, no analytical result for the solutions is available. Moreover, the cases where multiple flows can coexist have not been investigated in detail since their discovery by Noir et al (2003 Geophys. J. Int. 154 407–16). In this work we aim at deriving analytical results for the solutions, aiming in particular at first estimating the ranges of parameters where multiple solutions exist, and second studying quantitatively their stability. Using the models recently proposed by Noir and Cébron (2013 J. Fluid Mech. 737 412–39), which are more generic in the inviscid limit than the equations of Busse, we analytically describe these solutions, their conditions of existence, and their stability in a systematic manner. We then successfully compare these analytical results with the theory of Busse (1968). Dynamical model equations are finally proposed to investigate the stability of the solutions, which describe the bifurcation of the unstable flow solution. We also report for the first time the possibility that time-dependent multiple flows can coexist in precessing triaxial ellipsoids. Numerical integrations of the algebraic and differential equations have been efficiently performed with the dedicated script FLIPPER (supplementary material). (paper)
Aeroacoustic computation of low mach number flow
Energy Technology Data Exchange (ETDEWEB)
Skriver Dahl, K. [Risoe National Laboratory, Roskilde (Denmark)
1997-12-31
The possibilities of applying a recently developed numerical technique to predict aerodynamically generated sound from wind turbines is explored. The technique is a perturbation technique that has the advantage that the underlying flow field and the sound field are computed separately. Solution of the incompressible, time dependent flow field yields a hydrodynamic density correction to the incompressible constant density. The sound field is calculated from a set of equations governing the inviscid perturbations about the corrected flow field. Here, the emphasis is placed on the computation of the sound field. The nonlinear partial differential equations governing the sound fields are solved numerically using an explicit MacCormack scheme. Two types of non-reflecting boundary conditions are applied; one based on the asymptotic solution of the governing equations and the other based on a characteristic analysis of the governing equations. The former condition is easy to use and it performs slightly better than the charcteristic based condition. The technique is applied to the problems of the sound generation of a co-rotating vortex pair, which is a quadrupole, and the viscous flow over a circular cylinder, which is a dipole. Numerical results agree very well with the analytical solution for the problem of the co-rotating vortex pair. Numerical results for the viscous flow over a cylinder are presented and evaluated qualitatively. (au)
Simulation of a Wall-Bounded Flow using a Hybrid LES/RAS Approach with Turbulence Recycling
Quinlan, Jesse R.; Mcdaniel, James; Baurle, Robert A.
2012-01-01
Simulations of a supersonic recessed-cavity flow are performed using a hybrid large-eddy/ Reynolds-averaged simulation approach utilizing an inflow turbulence recycling procedure and hybridized inviscid flux scheme. Calorically perfect air enters the three-dimensional domain at a free stream Mach number of 2.92. Simulations are performed to assess grid sensitivity of the solution, efficacy of the turbulence recycling, and effect of the shock sensor used with the hybridized inviscid flux scheme. Analysis of the turbulent boundary layer upstream of the rearward-facing step for each case indicates excellent agreement with theoretical predictions. Mean velocity and pressure results are compared to Reynolds-averaged simulations and experimental data for each case, and these comparisons indicate good agreement on the finest grid. Simulations are repeated on a coarsened grid, and results indicate strong grid density sensitivity. The effect of turbulence recycling on the solution is illustrated by performing coarse grid simulations with and without inflow turbulence recycling. Two shock sensors, one of Ducros and one of Larsson, are assessed for use with the hybridized inviscid flux reconstruction scheme.
Improvements of Critical Heat Flux Models Based on the Viscous Potential Flow Theory
International Nuclear Information System (INIS)
Kim, Byoung Jae; Lee, Jong Hyuk; Kim, Kyung Doo
2014-01-01
The absence of fluid viscosities in most existing models may be attributed to the fact that inviscid flow analyses are performed for the model development. For example, the hydrodynamic theory and macrolayer dryout models rely on the Rayleigh-Taylor, Kelvin-Helmholtz, and capillary instabilities for inviscid fluids. However, as the viscosities of two fluids become closer, none of them cannot be neglected. Moreover, the gas viscosity effect cannot be neglected on the condition that the gas layer is thin. Nevertheless, the previous studies neglected the viscous effect. Recently, Kim et al. showed that for the model development of critical heat flux and minimum film boiling, the Rayleigh-Taylor instability should be analyzed with a thin layer of viscous gas instead of a thick layer of inviscid gas. The decrease of the most unstable wavelength was shown to improve the prediction accuracy of critical heat flux models for various fluids, particularly at elevated pressures. In addition, the most dangerous wavelength and the most rapid growth rate for viscous thin films are shown to be applicable to the minimum heat flux condition. Kim et al. touch only the most unstable wavelength for developing critical heat flux models. The critical heat flux is inversely proportional to the square root of the most unstable wavelength (Zuber, Guan et al). Here, we notice that the existing critical heat flux models make use of the Kelvin-Helmholtz instability of inviscid flows. The Kelvin-Helmholtz instability determines the maximum vapor escape velocity (Zuber) and the initial liquid macrolayer thickness (Haramura and Katto). Therefore, there is a room for improving the prediction accuracy by the help of the Kelvin-Helmholtz instability of viscous fluids. The Kelvin-Helmholtz instability arises when the different fluid layers are in relative motion. Usually, a uniform flow is considered in each fluid layer, allowing a velocity discontinuity at the interface. Therefore, in general, the
Nonlinear evolution of a layered stratified shear flow
Lee, V.; Caulfield, C. P.
2001-10-01
We investigate numerically and theoretically the nonlinear evolution of a parallel shear flow at moderate Reynolds number which has embedded within it a mixed layer of intermediate fluid. The two relatively thin strongly stratified density interfaces are centered on the edges of the shear layer. We are particularly interested in the development of primary and secondary instabilities. We present the results of a stability analysis which predicts that such flows may be unstable to stationary vortical disturbances which are a generalization of an inviscid instability first considered by G.I. Taylor. We investigate the behavior of these "Taylor billows" at finite amplitude through two-dimensional numerical simulations. We observe that the braid regions connecting adjacent primary Taylor billows are susceptible to secondary, inherently two-dimensional instabilities. We verify that these secondary instabilities, which take the form of small elliptical vortices, arise due to a local intensification of the spanwise vorticity in the braid region.
Investigation of gas particle flow in an erosion wind tunnel
Energy Technology Data Exchange (ETDEWEB)
Tabakoff, W.; Hamed, A.; Beacher, B.
1983-04-01
Trajectories of small particles approaching the test specimen in an erosion tunnel are analytically determined. The two-dimensional equations of motion are solved for a spherical particle under the sole influence of aerodynamic drag. The two-dimensional gradients of gas properties in the flow field are determined by a numerical solution of the equations describing a compressible inviscid fluid. At one inlet condition, the trajectories are computed for coal ash particles of various sizes approaching test specimens at several orientations. Trends are identified in the approaching characteristics that may be related to the observed erosion. The results indicate that, for ash particles with diameters less than 10 ..mu..m, significant numbers are deflected away from the specimen. These particles would otherwise impact with the specimen if they had to resist the turning effect of the flow field.
Drag Reduction by Laminar Flow Control
Directory of Open Access Journals (Sweden)
Nils Beck
2018-01-01
Full Text Available The Energy System Transition in Aviation research project of the Aeronautics Research Center Niedersachsen (NFL searches for potentially game-changing technologies to reduce the carbon footprint of aviation by promoting and enabling new propulsion and drag reduction technologies. The greatest potential for aerodynamic drag reduction is seen in laminar flow control by boundary layer suction. While most of the research so far has been on partial laminarization by application of Natural Laminar Flow (NLF and Hybrid Laminar Flow Control (HLFC to wings, complete laminarization of wings, tails and fuselages promises much higher gains. The potential drag reduction and suction requirements, including the necessary compressor power, are calculated on component level using a flow solver with viscid/inviscid coupling and a 3D Reynolds-Averaged Navier-Stokes (RANS solver. The effect on total aircraft drag is estimated for a state-of-the-art mid-range aircraft configuration using preliminary aircraft design methods, showing that total cruise drag can be halved compared to today’s turbulent aircraft.
Numerical study of the viscous heat-conducting gas flow in a long shock tube
Kudryavtsev, Alexey; Khotyanovsky, Dmitry
2017-10-01
The results of numerical simulations of the propagation of the shock wave in a cylindrical shock tube of large length are presented. The results of the numerical computations agree well with the experimental data of Duff. The effects of viscous friction and heat conduction cause significant difference of the shock wave velocity from its inviscid theoretical value. The results of the computations at the considered flow parameters show that the shock wave and the contact surface, starting from a certain moment of time, propagate with equal speeds.
Energy Technology Data Exchange (ETDEWEB)
Cline, M.C.
1981-08-01
VNAP2 is a computer program for calculating turbulent (as well as laminar and inviscid), steady, and unsteady flow. VNAP2 solves the two-dimensional, time-dependent, compressible Navier-Stokes equations. The turbulence is modeled with either an algebraic mixing-length model, a one-equation model, or the Jones-Launder two-equation model. The geometry may be a single- or a dual-flowing stream. The interior grid points are computed using the unsplit MacCormack scheme. Two options to speed up the calculations for high Reynolds number flows are included. The boundary grid points are computed using a reference-plane-characteristic scheme with the viscous terms treated as source functions. An explicit artificial viscosity is included for shock computations. The fluid is assumed to be a perfect gas. The flow boundaries may be arbitrary curved solid walls, inflow/outflow boundaries, or free-jet envelopes. Typical problems that can be solved concern nozzles, inlets, jet-powered afterbodies, airfoils, and free-jet expansions. The accuracy and efficiency of the program are shown by calculations of several inviscid and turbulent flows. The program and its use are described completely, and six sample cases and a code listing are included.
Fluid Dynamics And Mass Transfer In Two-Fluid Taylor-Couette Flow
International Nuclear Information System (INIS)
Baier, G.; Graham, M.D.
1998-01-01
The Taylor-Couette instability of a single liquid phase can be used to enhance mass transfer processes such as filtration and membrane separations. We consider here the possibility of using this instability to enhance interphase transport in a two-fluid systems, with a view toward improved liquid-liquid extractions for biotechnology applications. We investigate the centrifugal instability of a pair of radially stratified immiscible liquids in the annular gap between concentric, corotating cylinders: two-fluid Taylor-Couette flow. Experiments show that a two-layer flow with a well-defined interface and Taylor vortices in each phase can be obtained. The experimental results are in good agreement with predictions of inviscid arguments based on a two-phase extension of Rayleigh's criterion, as well as with detailed linear stability calculations. For a given geometry, the most stable configuration occurs for fluids of roughly (exactly in the inviscid limit) equal dynamic viscosities. A number of preliminary mass transfer experiments have also been performed, in the presence of axial counterflow. The onset of Taylor vortices coincides with a clear decrease in the extent of axial dispersion and an increase in the rate of interphase transport, thus suggesting that this flow geometry may provide an effective means for countercurrent chromatographic separations
Structure of the Small Amplitude Motion on Transversely Sheared Mean Flows
Goldstein, Marvin E.; Afsar, Mohamed Z.; Leib, Stewart J.
2013-01-01
This paper considers the small amplitude unsteady motion of an inviscid non-heat conducting compressible fluid on a transversely sheared mean flow. It extends a previous result given in Goldstein (1978(b) and 1979(a)) which shows that the hydrodynamic component of the motion is determined by two arbitrary convected quantities in the absence of solid surfaces or other external sources. The result is important because it can be used to specify appropriate boundary conditions for unsteady surface interaction problems on transversely sheared mean flows in the same way that the vortical component of the Kovasznay (1953) decomposition is used to specify these conditions for surface interaction problems on uniform mean flows. But unlike the Kovasznay (1953) case the arbitrary convected quantities no longer bear a simple relation to the physical variables. One purpose of this paper is to derive a formula that relates these quantities to the (physically measurable) vorticity and pressure fluctuations in the flow.
A numerical method for computing unsteady 2-D boundary layer flows
Krainer, Andreas
1988-01-01
A numerical method for computing unsteady two-dimensional boundary layers in incompressible laminar and turbulent flows is described and applied to a single airfoil changing its incidence angle in time. The solution procedure adopts a first order panel method with a simple wake model to solve for the inviscid part of the flow, and an implicit finite difference method for the viscous part of the flow. Both procedures integrate in time in a step-by-step fashion, in the course of which each step involves the solution of the elliptic Laplace equation and the solution of the parabolic boundary layer equations. The Reynolds shear stress term of the boundary layer equations is modeled by an algebraic eddy viscosity closure. The location of transition is predicted by an empirical data correlation originating from Michel. Since transition and turbulence modeling are key factors in the prediction of viscous flows, their accuracy will be of dominant influence to the overall results.
Computation of supersonic viscous flows over ogive-cylinders at angle of attack
Rakich, J. V.; Vigneron, Y. C.; Agarwal, R.
1979-01-01
The parabolic Navier-Stokes (PNS) marching finite-difference method is applied to 3-D viscous flow over pointed ogive-cylinders, and to turbulent flow over a cone. Ogive computations were performed using the new technique recently reported by Vigneron, Rakich, and Tannehill. Comparison is made with experiment and inviscid computations. The present results show that this method, which neglects part of the pressure gradient in the x-momentum equation, is nevertheless valid for flows with a strong favorable pressure gradient. In addition, turbulent separated flow over a cone has been computed using the older PNS code due to Lubard and Helliwell. It is found that one must freeze the turbulent eddy-viscosity model upstream of 3-D separation to get agreement with experiment.
On the origins of vortex shedding in two-dimensional incompressible flows
Boghosian, M. E.; Cassel, K. W.
2016-12-01
An exegesis of a novel mechanism leading to vortex splitting and subsequent shedding that is valid for two-dimensional incompressible, inviscid or viscous, and external or internal or wall-bounded flows, is detailed in this research. The mechanism, termed the vortex shedding mechanism (VSM) is simple and intuitive, requiring only two coincident conditions in the flow: (1) the existence of a location with zero momentum and (2) the presence of a net force having a positive divergence. Numerical solutions of several model problems illustrate causality of the VSM. Moreover, the VSM criteria is proved to be a necessary and sufficient condition for a vortex splitting event in any two-dimensional, incompressible flow. The VSM is shown to exist in several canonical problems including the external flow past a circular cylinder. Suppression of the von Kármán vortex street is demonstrated for Reynolds numbers of 100 and 400 by mitigating the VSM.
Turbulence Modeling of Flows with Extensive Crossflow Separation
Directory of Open Access Journals (Sweden)
Argyris G. Panaras
2015-07-01
Full Text Available The reasons for the difficulty in simulating accurately strong 3-D shock wave/turbulent boundary layer interactions (SBLIs and high-alpha flows with classical turbulence models are investigated. These flows are characterized by the appearance of strong crossflow separation. In view of recent additional evidence, a previously published flow analysis, which attributes the poor performance of classical turbulence models to the observed laminarization of the separation domain, is reexamined. According to this analysis, the longitudinal vortices into which the separated boundary layer rolls up in this type of separated flow, transfer external inviscid air into the part of the separation adjacent to the wall, decreasing its turbulence. It is demonstrated that linear models based on the Boussinesq equation provide solutions of moderate accuracy, while non-linear ones and others that consider the particular structure of the flow are more efficient. Published and new Reynolds Averaged Navier–Stokes (RANS simulations are reviewed, as well as results from a recent Large Eddy Simulation (LES study, which indicate that in calculations characterized by sufficient accuracy the turbulent kinetic energy of the reverse flow inside the separation vortices is very low, i.e., the flow is almost laminar there.
Kang, Donggu; Payor, James
2015-01-01
We consider flow rounding: finding an integral flow from a fractional flow. Costed flow rounding asks that we find an integral flow with no worse cost. Randomized flow rounding requires we randomly find an integral flow such that the expected flow along each edge matches the fractional flow. Both problems are reduced to cycle canceling, for which we develop an $O(m \\log(n^2/m))$ algorithm.
International Nuclear Information System (INIS)
Thornton, E.A.; Ramakrishnan, R.
1986-06-01
Prediction of compressible flow phenomena using the finite element method is of recent origin and considerable interest. Two shock capturing finite element formulations for high speed compressible flows are described. A Taylor-Galerkin formulation uses a Taylor series expansion in time coupled with a Galerkin weighted residual statement. The Taylor-Galerkin algorithms use explicit artificial dissipation, and the performance of three dissipation models are compared. A Petrov-Galerkin algorithm has as its basis the concepts of streamline upwinding. Vectorization strategies are developed to implement the finite element formulations on the NASA Langley VPS-32. The vectorization scheme results in finite element programs that use vectors of length of the order of the number of nodes or elements. The use of the vectorization procedure speeds up processing rates by over two orders of magnitude. The Taylor-Galerkin and Petrov-Galerkin algorithms are evaluated for 2D inviscid flows on criteria such as solution accuracy, shock resolution, computational speed and storage requirements. The convergence rates for both algorithms are enhanced by local time-stepping schemes. Extension of the vectorization procedure for predicting 2D viscous and 3D inviscid flows are demonstrated. Conclusions are drawn regarding the applicability of the finite element procedures for realistic problems that require hundreds of thousands of nodes
Experimental characterization of spin motor nozzle flow.
Energy Technology Data Exchange (ETDEWEB)
Erven, Rocky J.; Peterson, Carl Williams; Henfling, John Francis
2006-11-01
The Mach number in the inviscid core of the flow exiting scarfed supersonic nozzles was measured using pitot probes. Nozzle characterization experiments were conducted in a modified section of an obsolete M = 7.3 test section/nozzle assembly on Sandia's Hypersonic Wind Tunnel. By capitalizing on existing hardware, the cost and time required for tunnel modifications were significantly reduced. Repeatability of pitot pressure measurements was excellent, and instrumentation errors were reduced by optimizing the pressure range of the transducers used for each test run. Bias errors in probe position prevented us from performing a successful in situ calibration of probe angle effects using pitot probes placed at an angle to the nozzle centerline. The abrupt throat geometry used in the Baseline and Configuration A and B nozzles modeled the throat geometry of the flight vehicle's spin motor nozzles. Survey data indicates that small (''unmeasurable'') differences in the nozzle throat geometries produced measurable flow asymmetries and differences in the flow fields generated by supposedly identical nozzles. Therefore, data from the Baseline and Configuration A and B nozzles cannot be used for computational fluid dynamics (CFD) code validation. Configuration C and D nozzles replaced the abrupt throat geometry of Baseline and Configuration A and B nozzles with a 0.500-inch streamwise radius of curvature in the throat region. This throat geometry eliminated the flow asymmetries, flow separation in the nozzle throat, and measurable differences between the flow fields from identical nozzles that were observed in Baseline/A/B nozzles. Data from Configuration C and D nozzles can be used for CFD code validation.
Numerical simulation of compressible, turbulent, two-phase flow
Coakley, t. J.; Champney, J. M.
1985-01-01
A computer program for numerically simulating compressible, turbulent, two-phase flows is described and applied. Special attention is given to flows in which dust is ingested into the turbulent boundary layer behind shock waves moving over the earth's surface. it is assumed that the two phases are interpenetrating continua which are coupled by drag forces and heat transfer. The particle phase is assumed to be dilute, and turbulent effects are modeled by zero- and two-equation eddy viscosity models. An important feature of the turbulence modeling is the treatment of surface boundary conditions which control the ingestion of particles into the boundary layer by turbulent friction and diffusion. The numerical method uses second-order implicit upwind differencing of the inviscid terms of the equations and second-order central differencing of the viscous terms. A diagonal form of the implicit algorithm is used to improve efficiency, and the transformation to a curvilinear coordinate system is accomplished by the finite volume techniques. Applications to a series of representative flows include a two-phase nozzle flow, the steady flow of air over a sand bed, and the air flow behind a normal shock wave in uniform motion over a sand bed. Results of the latter two applications are compared with experimental results.
Optimal energy growth in a stably stratified shear flow
Jose, Sharath; Roy, Anubhab; Bale, Rahul; Iyer, Krithika; Govindarajan, Rama
2018-02-01
Transient growth of perturbations by a linear non-modal evolution is studied here in a stably stratified bounded Couette flow. The density stratification is linear. Classical inviscid stability theory states that a parallel shear flow is stable to exponentially growing disturbances if the Richardson number (Ri) is greater than 1/4 everywhere in the flow. Experiments and numerical simulations at higher Ri show however that algebraically growing disturbances can lead to transient amplification. The complexity of a stably stratified shear flow stems from its ability to combine this transient amplification with propagating internal gravity waves (IGWs). The optimal perturbations associated with maximum energy amplification are numerically obtained at intermediate Reynolds numbers. It is shown that in this wall-bounded flow, the three-dimensional optimal perturbations are oblique, unlike in unstratified flow. A partitioning of energy into kinetic and potential helps in understanding the exchange of energies and how it modifies the transient growth. We show that the apportionment between potential and kinetic energy depends, in an interesting manner, on the Richardson number, and on time, as the transient growth proceeds from an optimal perturbation. The oft-quoted stabilizing role of stratification is also probed in the non-diffusive limit in the context of disturbance energy amplification.
A matrix-free implicit treatment for all speed flows on unstructured grids
International Nuclear Information System (INIS)
Kloczko, Th.
2006-03-01
The aim of this research work is the development of an efficient implicit scheme for computing compressible and low-speed flows on unstructured meshes. The first part is devoted to the review and analysis of some standard block-implicit treatments for the two-dimensional Euler and Navier-Stokes equations with a view to identify the best candidate for a fair comparison with the matrix-free treatment. The second part forms the main original contribution of this research work. It describes and analyses a matrix-free treatment that can be applied to any type of flow (inviscid/viscous, low Mach/highly compressible, steady/unsteady). The third part deals with the implementation of this treatment within the CAST3M code, and the demonstration of its advantages over existing techniques for computing applications of interest for the CEA: low-Mach number steady and unsteady flows in a Tee junction for example
Analysis of the Scramjet inlet flow field using two-dimensional Navier-Stokes equations
Kumar, A.; Tiwari, S. N.
1982-01-01
A computer code was developed to solve the full two dimensional Navier-Stokes equations in a scramjet inlet. The analysis uses a numerical coordinate transformation which generates a set of boundary-fitted curvilinear coordinates. The explicit finite difference algorithm of MacCormack is used to solve the governing equations. A two-layer eddy viscosity model is used for the turbulent flow. The code can analyze both inviscid and viscous flows with multiple struts in the flow field. Detailed results are presented for two model problems and two scramjet inlets with one and two struts. The application of the two dimensional analysis in the preliminary design of the actual scramjet inlet is briefly discussed.
A proposed through-flow inverse method for the design of mixed-flow pumps
Borges, Joao Eduardo
1991-01-01
A through-flow (hub-to-shroud) truly inverse method is proposed and described. It uses an imposition of mean swirl, i.e., radius times mean tangential velocity, given throughout the meridional section of the turbomachine as an initial design specification. In the present implementation, it is assumed that the fluid is inviscid, incompressible, and irrotational at inlet and that the blades are supposed to have zero thickness. Only blade rows that impart to the fluid a constant work along the space are considered. An application of this procedure to design the rotor of a mixed-flow pump is described in detail. The strategy used to find a suitable mean swirl distribution and the other design inputs is also described. The final blade shape and pressure distributions on the blade surface are presented, showing that it is possible to obtain feasible designs using this technique. Another advantage of this technique is the fact that it does not require large amounts of CPU time.
Xiang, G.; Wang, C.; Teng, H.; Jiang, Z.
2018-03-01
This study explores the three-dimensional (3D) wave configurations induced by 3D asymmetrical intersecting compression wedges in supersonic and hypersonic inviscid flows. By using the "spatial dimension reduction" approach, the problem of 3D steady shock/shock interaction is converted to that of the interaction of two moving shock waves in the characteristic two-dimensional (2D) plane. Shock polar theory is used to analyze the shock configurations in asymmetrical situations. The results show that various shock configurations exist in 3D asymmetrical shock wave interactions, including regular interaction, transitioned regular interaction, single Mach interaction, inverse single Mach interaction, transitional double Mach interaction, weak shock interaction, and weak single Mach interaction. All of the above 3D steady shock/shock interactions have their corresponding 2D moving shock/shock interaction configurations. Numerical simulations are performed by solving the 3D inviscid Euler equations with the non-oscillatory, non-free parameters, dissipative (NND) numerical scheme, and good agreement with the theoretical analysis is obtained. Furthermore, the comparison of results show that the concept of the "virtual wall" in shock dynamics theory is helpful for understanding the mechanism of two-dimensional shock/shock interactions.
Analysis of a discrete element method and coupling with a compressible fluid flow method
International Nuclear Information System (INIS)
Monasse, L.
2011-01-01
This work aims at the numerical simulation of compressible fluid/deformable structure interactions. In particular, we have developed a partitioned coupling algorithm between a Finite Volume method for the compressible fluid and a Discrete Element method capable of taking into account fractures in the solid. A survey of existing fictitious domain methods and partitioned algorithms has led to choose an Embedded Boundary method and an explicit coupling scheme. We first showed that the Discrete Element method used for the solid yielded the correct macroscopic behaviour and that the symplectic time-integration scheme ensured the preservation of energy. We then developed an explicit coupling algorithm between a compressible inviscid fluid and an un-deformable solid. Mass, momentum and energy conservation and consistency properties were proved for the coupling scheme. The algorithm was then extended to the coupling with a deformable solid, in the form of a semi implicit scheme. Finally, we applied this method to unsteady inviscid flows around moving structures: comparisons with existing numerical and experimental results demonstrate the excellent accuracy of our method. (author) [fr
Numerical study of the particle motion with 6 degree of freedom in a flow
Essmann, Erich; Shui, Pei; Govindarajan, Rama; Popinet, Stephane; Valluri, Prashant
2017-11-01
Traditionally solid-fluid simulations used an incomplete physics model, with only a one-way coupling between the solid and fluid domains. The basis for our work is Gerris, an open-source fluid solver, (Popinet et al., 2003). Its adaptive Cartesian mesh scores over traditional algorithms in convergence. We augmented Gerris with a fully-coupled solver for fluid-solid interaction with 6 degrees-of-freedom (6DOF). This was done by using the immersed boundary method, which allows the solid boundary to move or deform while requiring few mesh adaptations. Our new solver, Gerris Immersed Solid Solver (GISS), accounts for collisions with a novel composite contact model (Ness & Sun, 2016) for solid-solid interactions. We have validated our methodology against published experimental data. We are thus enabled to reveal some deep correlations between the hydrodynamic force and particle motion in inviscid flow. (Aref, 1993) had shown that the dynamics should be chaotic under certain conditions and our inviscid results agree with these findings. Our analysis includes analytic solutions and recurrence quantification (Marwan et al., 2007), to quantify the chaos and to evaluate the nature of that behaviour.
Experimental and numerical studies on super-cavitating flow of axisymmetric cavitators
Directory of Open Access Journals (Sweden)
Byoung-Kwon Ahn
2010-03-01
Full Text Available Recently underwater systems moving at high speed such as a super-cavitating torpedo have been studied for their practical advantage of the dramatic drag reduction. In this study we are focusing our attention on super-cavitating flows around axisymmetric cavitators. A numerical method based on inviscid flow is developed and the results for several shapes of the cavitator are presented. First using a potential based boundary element method, we find the shape of the cavitator yielding a sufficiently large enough cavity to surround the body. Second, numerical predictions of supercavity are validated by comparing with experimental observations carried out in a high speed cavitation tunnel at Chungnam National University (CNU CT.
Detailed Aerodynamic Analysis of a Shrouded Tail Rotor Using an Unstructured Mesh Flow Solver
Lee, Hee Dong; Kwon, Oh Joon
The detailed aerodynamics of a shrouded tail rotor in hover has been numerically studied using a parallel inviscid flow solver on unstructured meshes. The numerical method is based on a cell-centered finite-volume discretization and an implicit Gauss-Seidel time integration. The calculation was made for a single blade by imposing a periodic boundary condition between adjacent rotor blades. The grid periodicity was also imposed at the periodic boundary planes to avoid numerical inaccuracy resulting from solution interpolation. The results were compared with available experimental data and those from a disk vortex theory for validation. It was found that realistic three-dimensional modeling is important for the prediction of detailed aerodynamics of shrouded rotors including the tip clearance gap flow.
An improved flux-split algorithm applied to hypersonic flows in chemical equilibrium
Palmer, Grant
1988-01-01
An explicit, finite-difference, shock-capturing numerical algorithm is presented and applied to hypersonic flows assumed to be in thermochemical equilibrium. Real-gas chemistry is either loosely coupled to the gasdynamics by way of a Gibbs free energy minimization package or fully coupled using species mass conservation equations with finite-rate chemical reactions. A scheme is developed that maintains stability in the explicit, finite-rate formulation while allowing relatively high time steps. The codes use flux vector splitting to difference the inviscid fluxes and employ real-gas corrections to viscosity and thermal conductivity. Numerical results are compared against existing ballistic range and flight data. Flows about complex geometries are also computed.
User's manual for three-dimensional analysis of propeller flow fields
Chaussee, D. S.; Kutler, P.
1983-01-01
A detailed operating manual is presented for the prop-fan computer code (in addition to supporting programs) recently developed by Kutler, Chaussee, Sorenson, and Pulliam while at the NASA'S Ames Research Center. This code solves the inviscid Euler equations using an implicit numerical procedure developed by Beam and Warming of Ames. A description of the underlying theory, numerical techniques, and boundary conditions with equations, formulas, and methods for the mesh generation program (MGP), three dimensional prop-fan flow field program (3DPFP), and data reduction program (DRP) is provided, together with complete operating instructions. In addition, a programmer's manual is also provided to assist the user interested in modifying the codes. Included in the programmer's manual for each program is a description of the input and output variables, flow charts, program listings, sample input and output data, and operating hints.
Viscous flow in the near-Venusian plasma wake
International Nuclear Information System (INIS)
Perez-de-Tejada, H.; Dryer, M.; Vaisberg, O.L.
1977-01-01
The acquisiton of the Venera 9 and 10 plasma probe data has provided further support for the notion that the shocked solar wind in the flank regions of the Venusian ionosheath interacts viscously with the local ionospheric plasma and that the resulting mixing region is rapidly forced into the planetary umbra. The measured velocities and flow directions suggest that the deflection of the mixing layer downstream of the terminator proceeds at a fast pace, as was predicted from the analysis of a suitable MHD analog proposed by Perez-de-Tejada and Dryer (1976). By measuring the apparent displacement of the mixing region within the planetary umbra with respect to the position of the undeviated ionopause (calculated from the inviscid flow model of Spreiter et al, (1970) it is possible to obtain an order-of-magnitude estimate of the equivalent kinematic viscosity coefficient of the flow in the region. Some speculative comments are also given in regard to the behavior of the flow in the Venusian plasma wake, in particular, to the implications that the penetration of the mixing layer into the umbra may have for the formation of the nighttime Venusian ionosphere
Theoretical study of flow in a thermal countercurrent centrifuge
International Nuclear Information System (INIS)
Durivault, Jean; Louvet, Pierre.
1976-03-01
This paper deals with the flow calculation in a thermal countercurrent centrifuge at total reflux. Matched asymptotic expansions are used to find approximate solutions of Navier-Stokes equations which are assumed to be valid in the whole domaine. Convection and viscous dissipation disappear because of linearization, but compressibility is taken into account. Let epsilon be the Ekman number. The equations are solved in the inviscid core, in the horizontal Ekman layers of thickness 0 (epsilonsup(1/2) and in the Stewartson layer of thickness 0 (epsilonsup(1/3)), parallel to the axis. As the thermal convection is neglected, the Stewartson layer of thickness 0 (epsilon sup(1/4)) does not occur. The results show the importance of the recirculating mass-flow rate of order 0 (epsilonsup(1/3)) in front of the countercurrent mass-flow rate of order 0 (epsilonsup(1/2)). The temperature profile rules the pattern and the intensity of the recirculating flow [fr
CFD Study of NACA 0018 Airfoil with Flow Control
Eggert, Christopher A.; Rumsey, Christopher L.
2017-01-01
The abilities of two different Reynolds-Averaged Navier-Stokes codes to predict the effects of an active flow control device are evaluated. The flow control device consists of a blowing slot located on the upper surface of an NACA 0018 airfoil, near the leading edge. A second blowing slot present on the airfoil near mid-chord is not evaluated here. Experimental results from a wind tunnel test show that a slot blowing with high momentum coefficient will increase the lift of the airfoil (compared to no blowing) and delay flow separation. A slot with low momentum coefficient will decrease the lift and induce separation even at low angles of attack. Two codes, CFL3D and FUN3D, are used in two-dimensional computations along with several different turbulence models. Two of these produced reasonable results for this flow, when run fully turbulent. A more advanced transition model failed to predict reasonable results, but warrants further study using different inputs. Including inviscid upper and lower tunnel walls in the simulations was found to be important in obtaining pressure distributions and lift coefficients that best matched experimental data. A limited number of three-dimensional computations were also performed.
Exact and Approximate Solutions for Transient Squeezing Flow
Lang, Ji; Santhanam, Sridhar; Wu, Qianhong
2017-11-01
In this paper, we report two novel theoretical approaches to examine a fast-developing flow in a thin fluid gap, which is widely observed in industrial applications and biological systems. The problem is featured by a very small Reynolds number and Strouhal number, making the fluid convective acceleration is negligible, while its local acceleration is not. We have developed an exact solution for this problem which shows that the flow starts with an inviscid limit when the viscous effect has no time to appear, and is followed by a subsequent developing flow, in which the viscous effect continues to penetrate into the entire fluid gap. An approximate solution is also developed using a boundary layer integral method. This solution precisely captures the general behavior of the transient fluid flow process, and agrees very well with the exact solution. We also performed numerical simulation using Ansys-CFX. Excellent agreement between the analytical and the numerical solutions is obtained, indicating the validity of the analytical approaches. The study presented herein fills the gap in the literature, and will have a broad impact in industrial and biomedical applications. This work is supported by National Science Foundation CBET Fluid Dynamics Program under Award #1511096, and supported by the Seed Grant from The Villanova Center for the Advancement of Sustainability in Engineering (VCASE).
Directory of Open Access Journals (Sweden)
U Ali
2016-06-01
Full Text Available The objectives of the present study on Unmanned Combat Air Vehicles (UCAVs are two-fold: first to control the flow by inserting leading-edge and cross-flow slots and analysing the viscous flow development over the outer panels of a flying-wing configuration to maximise the performance of the elevons control surfaces; second to predict high-lift performance particularly the maximum-lift characteristics. This is demonstrated using a variety of inviscid Vortex Lattice Method (VLM and Euler, and viscous CFD Reynolds Averaged Navier-Stokes (RANS methods. The computational results are validated against experiment measured in a wind tunnel. Two flying-wing planforms are considered based around a generic 40˚ edge-aligned configuration. The VLM predicts a linear variation of lift and pitching moment with incidence angle, and substantially under-predicts the induced drag. Results obtained from RANS and Euler agree well with experiment.
MONOTONIC DERIVATIVE CORRECTION FOR CALCULATION OF SUPERSONIC FLOWS WITH SHOCK WAVES
Directory of Open Access Journals (Sweden)
P. V. Bulat
2015-07-01
Full Text Available Subject of Research. Numerical solution methods of gas dynamics problems based on exact and approximate solution of Riemann problem are considered. We have developed an approach to the solution of Euler equations describing flows of inviscid compressible gas based on finite volume method and finite difference schemes of various order of accuracy. Godunov scheme, Kolgan scheme, Roe scheme, Harten scheme and Chakravarthy-Osher scheme are used in calculations (order of accuracy of finite difference schemes varies from 1st to 3rd. Comparison of accuracy and efficiency of various finite difference schemes is demonstrated on the calculation example of inviscid compressible gas flow in Laval nozzle in the case of continuous acceleration of flow in the nozzle and in the case of nozzle shock wave presence. Conclusions about accuracy of various finite difference schemes and time required for calculations are made. Main Results. Comparative analysis of difference schemes for Euler equations integration has been carried out. These schemes are based on accurate and approximate solution for the problem of an arbitrary discontinuity breakdown. Calculation results show that monotonic derivative correction provides numerical solution uniformity in the breakdown neighbourhood. From the one hand, it prevents formation of new points of extremum, providing the monotonicity property, but from the other hand, causes smoothing of existing minimums and maximums and accuracy loss. Practical Relevance. Developed numerical calculation method gives the possibility to perform high accuracy calculations of flows with strong non-stationary shock and detonation waves. At the same time, there are no non-physical solution oscillations on the shock wave front.
Epi-Two-Dimensional Fluid Flow: A New Topological Paradigm for Dimensionality.
Yoshida, Z; Morrison, P J
2017-12-15
While a variety of fundamental differences are known to separate two-dimensional (2D) and three-dimensional (3D) fluid flows, it is not well understood how they are related. Conventionally, dimensional reduction is justified by an a priori geometrical framework; i.e., 2D flows occur under some geometrical constraint such as shallowness. However, deeper inquiry into 3D flow often finds the presence of local 2D-like structures without such a constraint, where 2D-like behavior may be identified by the integrability of vortex lines or vanishing local helicity. Here we propose a new paradigm of flow structure by introducing an intermediate class, termed epi-two-dimensional flow, and thereby build a topological bridge between 2D and 3D flows. The epi-2D property is local and is preserved in fluid elements obeying ideal (inviscid and barotropic) mechanics; a local epi-2D flow may be regarded as a "particle" carrying a generalized enstrophy as its charge. A finite viscosity may cause "fusion" of two epi-2D particles, generating helicity from their charges giving rise to 3D flow.
Merzkirch, Wolfgang
1974-01-01
Flow Visualization describes the most widely used methods for visualizing flows. Flow visualization evaluates certain properties of a flow field directly accessible to visual perception. Organized into five chapters, this book first presents the methods that create a visible flow pattern that could be investigated by visual inspection, such as simple dye and density-sensitive visualization methods. It then deals with the application of electron beams and streaming birefringence. Optical methods for compressible flows, hydraulic analogy, and high-speed photography are discussed in other cha
Jing, Wenjia; Tran, Hung V.; Yu, Yifeng
2017-05-01
The main goal of this paper is to understand finer properties of the effective burning velocity from a combustion model introduced by Majda and Souganidis (1994 Nonlinearity 7 1-30). Motivated by results in Bangert (1994 Calculus Variations PDE 2 49-63) and applications in turbulent combustion, we show that when the dimension is two and the flow of the ambient fluid is either weak or very strong, the level set of the effective burning velocity has flat pieces. Due to the lack of an applicable Hopf-type rigidity result, we need to identify the exact location of at least one flat piece. Implications on the effective flame front and other related inverse type problems are also discussed.
Hydrodynamic of a deformed bubble in linear shear flow
International Nuclear Information System (INIS)
Adoua, S.R.
2007-07-01
This work is devoted to the study of an oblate spheroidal bubble of prescribed shape set fixed in a linear shear flow using direct numerical simulation. The three dimensional Navier-Stokes equations are solved in orthogonal curvilinear coordinates using a finite volume method. The bubble response is studied over a wide range of the aspect ratio (1-2.7), the bubble Reynolds number (50-2000) and the non-dimensional shear rate (0.-1.2). The numerical simulations shows that the shear flow imposes a plane symmetry of the wake whatever the parameters of the flow. The trailing vorticity is organized into two anti-symmetrical counter rotating tubes with a sign imposed by the competition of two mechanisms (the Lighthill mechanism and the instability of the wake). Whatever the Reynolds number, the lift coefficient reaches the analytical value obtained in an inviscid, weakly sheared flow corresponding to a lift force oriented in the same direction as that of a spherical bubble. For moderate Reynolds numbers, the direction of the lift force reverses when the bubble aspect ratio is large enough as observed in experiments. This reversal occurs for aspect ratios larger than 2.225 and is found to be directly linked to the sign of the trailing vorticity which is concentrated within two counter-rotating threads which propel the bubble in a direction depending of their sign of rotation. The behavior of the drag does not revel any significant effect induced by the wake structure and follows a quadratic increase with the shear rate. Finally, the torque experienced by the bubble also reverses for the same conditions inducing the reversal of the lift force. By varying the orientation of the bubble in the shear flow, a stable equilibrium position is found corresponding to a weak angle between the small axis of the bubble and the flow direction. (author)
Agarwal, R.; Rakich, J. V.
1978-01-01
Computational results obtained with a parabolic Navier-Stokes marching code are presented for supersonic viscous flow past a pointed cone at angle of attack undergoing a combined spinning and coning motion. The code takes into account the asymmetries in the flow field resulting from the motion and computes the asymmetric shock shape, crossflow and streamwise shear, heat transfer, crossflow separation and vortex structure. The side force and moment are also computed. Reasonably good agreement is obtained with the side force measurements of Schiff and Tobak. Comparison is also made with the only available numerical inviscid analysis. It is found that the asymmetric pressure loads due to coning motion are much larger than all other viscous forces due to spin and coning, making viscous forces negligible in the combined motion.
CFD simulations of steady flows over the IAR 65o delta wing
International Nuclear Information System (INIS)
Benmeddour, A.; Mebarki, Y.; Huang, X.Z.
2004-01-01
Computational Fluid Dynamics (CFD) studies have been conducted to simulate vortical flows around the IAR 65 o delta wing with a sharp leading edge. The effects of the centerbody on the aerodynamic characteristics of the wing are also investigated. Two flow solvers have been employed to compute steady inviscid flows over with and without centerbody configurations of the wing. These two solvers are an IAR in-house code, FJ3SOLV, and the CFD-FASTRAN commercial software. The computed flow solutions of the two solvers have been compared and correlated against the IAR wind tunnel data, including Pressure Sensitive Paint (PSP) measurements. The major features of the primary vortex have been well captured and overall reasonable accuracy was obtained. In accordance with the experimental observations for the flow conditions considered, the CFD computations revealed no major global effects of the centerbody on the surface pressure distributions of the wing and on the lift coefficient. However, CFD-FASTRAN seems to predict a vortex breakdown, which is neither predicted by FJ3SOLV nor observed in the wind tunnel for the flow conditions considered. (author)
Supersonic Laminar Viscous Flow Past a Cone at Angle of Attack in Spinning and Coning Motion
Agarwal, Ramesh; Rakich, John V.
1982-01-01
Computational results obtained with a parabolic Navier-Stokes marching code are presented for supersonic viscous flow past a pointed cone at angle of attack undergoing a combined spinning and coning motion. The code takes into account the asymmetries in the flowfield resulting from the motion and computes the asymmetric shock shape, crossflow and streamwise shear, heat transfer, crossflow separation and vortex structure. The side force and moment are also computed. Reasonably good agreement is obtained with the side force measurements of Schiff and Tobak. Comparison is also made with the only available numerical inviscid analysis. It is found that the asymmetric pressure loads due lo coning motion are much larger than all other viscous forces due lo spin and coning, making viscous forces negligible in the combined motion.
Hanson, R. K.; Presley, L. L.; Williams, E. V.
1972-01-01
The method of characteristics for a chemically reacting gas is used in the construction of the time-dependent, one-dimensional flow field resulting from the normal reflection of an incident shock wave at the end wall of a shock tube. Nonequilibrium chemical reactions are allowed behind both the incident and reflected shock waves. All the solutions are evaluated for oxygen, but the results are generally representative of any inviscid, nonconducting, and nonradiating diatomic gas. The solutions clearly show that: (1) both the incident- and reflected-shock chemical relaxation times are important in governing the time to attain steady state thermodynamic properties; and (2) adjacent to the end wall, an excess-entropy layer develops wherein the steady state values of all the thermodynamic variables except pressure differ significantly from their corresponding Rankine-Hugoniot equilibrium values.
Hsieh, T.; Coakley, T. J.
1987-01-01
An investigation of downstream boundary effects on the frequency of self-excited oscillations in two-dimensional, separated transonic diffuser flows has been conducted numerically by solving the compressible, Reynolds-averaged, thin-layer Navier-Stokes equation with a two-equation turbulence model. It was found that the unsteady diffuser flowfields are very sensitive to the location of the downstream boundary. Extension of the diffuser downstream boundary significantly reduces the frequency and amplitude of oscillations for pressure, velocity and shock. Computational results suggest that the mechanism causing the self-excited oscillation changes from viscous convective wave dominated oscillations to inviscid acoustic wave dominated oscillations when the location of downstream boundary varies from 8.66 to 134.7 throat height. The existence of a suction slot in the experimental setup obscures the physical downstream boundary and, therefore, presents a difficulty for quantitative comparisons between computation and experiment.
International Nuclear Information System (INIS)
Liles, D.R.
1982-01-01
Internal boundaries in multiphase flow greatly complicate fluid-dynamic and heat-transfer descriptions. Different flow regimes or topological configurations can have radically dissimilar interfacial and wall mass, momentum, and energy exchanges. To model the flow dynamics properly requires estimates of these rates. In this paper the common flow regimes for gas-liquid systems are defined and the techniques used to estimate the extent of a particular regime are described. Also, the current computer-code procedures are delineated and introduce a potentially better method is introduced
Exact Integral Solutions for Two-Phase Flow
McWhorter, David B.; Sunada, Daniel K.
1990-03-01
Exact integral solutions for the horizontal, unsteady flow of two viscous, incompressible fluids are derived. Both one-dimensional and radial displacements are calculated with full consideration of capillary drive and for arbitrary capillary-hydraulic properties. One-dimensional, unidirectional displacement of a nonwetting phase is shown to occur increasingly like a shock front as the pore-size distribution becomes wider. This is in contrast to the situation when an inviscid nonwetting phase is displaced. The penetration of a nonwetting phase into porous media otherwise saturated by a wetting phase occurs in narrow, elongate distributions. Such distributions result in rapid and extensive penetration by the nonwetting phase. The process is remarkably sensitive to the capillary-hydraulic properties that determine the value of knw/kw at large wetting phase saturations, a region in which laboratory measurements provide the least resolution. The penetration of a nonwetting phase can be expected to be dramatically affected by the presence of fissures, worm holes, or other macropores. Calculations for radial displacement of a nonwetting phase resident at a small initial saturation show the displacement to be inefficient. The fractional flow of the nonwetting phase falls rapidly and, for a specific example, becomes 1% by the time one pore volume of water has been injected.
Energy Technology Data Exchange (ETDEWEB)
Feraille, Th.; Casalis, G. [Aerodynamics and Energetics Modeling Dept., 31 - Toulouse (France)
2003-12-01
the particles. Then, the evolution of the Eigenmodes from a given injection speed of the particles to another one is deduced by affinity, all other parameters being fixed. With a fixed Stokes number, stability results for a finite Reynolds number and results for the inviscid flow bring together when augmenting the particle mass concentration at the wall. Therefore, by knowing single phase flow results and the evolution of stability characteristics of the two phase flow in the inviscid case, it it easy to determine whether particle-laden Taylor flow is more or less stable than the monophasic Taylor flow for large particle mass concentration. (authors)
An experimental study of wall-injected flows in a rectangular cylinder
Perrotta, A.; Romano, G. P.; Favini, B.
2018-01-01
An experimental investigation of the flow inside a rectangular cylinder with air injected continuously along the wall is performed. This kind of flow is a two-dimensional approximation of what happens inside a solid rocket motor, where the lateral grain burns expelling exhaust gas or in processes with air filtration or devices to attain uniform flows. We propose a brief derivation of some analytical solutions and a comparison between these solutions and experimental data, which are obtained using the particle image velocimetry technique, to provide a global reconstruction of the flowfield. The flow, which enters orthogonal to the injecting wall, turns suddenly its direction being pushed towards the exit of the chamber. Under the incompressible and inviscid flow hypothesis, two analytical solutions are reported and compared. The first one, known as Hart-McClure solution, is irrotational and the injection velocity is non-perpendicular to the injecting wall. The other one, due to Taylor and Culick, has non-zero vorticity and constant, vertical injection velocity. The comparison with laminar solutions is useful to assess whether transition to turbulence is reached and how the disturbance thrown in by the porous injection influences and modifies those solutions.
Schmid, L. A.
1977-01-01
The first and second variations are calculated for the irreducible form of Hamilton's Principle that involves the minimum number of dependent variables necessary to describe the kinetmatics and thermodynamics of inviscid, compressible, baroclinic flow in a specified gravitational field. The form of the second variation shows that, in the neighborhood of a stationary point that corresponds to physically stable flow, the action integral is a complex saddle surface in parameter space. There exists a form of Hamilton's Principle for which a direct solution of a flow problem is possible. This second form is related to the first by a Friedrichs transformation of the thermodynamic variables. This introduces an extra dependent variable, but the first and second variations are shown to have direct physical significance, namely they are equal to the free energy of fluctuations about the equilibrium flow that satisfies the equations of motion. If this equilibrium flow is physically stable, and if a very weak second order integral constraint on the correlation between the fluctuations of otherwise independent variables is satisfied, then the second variation of the action integral for this free energy form of Hamilton's Principle is positive-definite, so the action integral is a minimum, and can serve as the basis for a direct trail and error solution. The second order integral constraint states that the unavailable energy must be maximum at equilibrium, i.e. the fluctuations must be so correlated as to produce a second order decrease in the total unavailable energy.
Blade bowing effects on radial equilibrium of inlet flow in axial compressor cascades
Directory of Open Access Journals (Sweden)
Han XU
2017-10-01
Full Text Available The circumferentially averaged equation of the inlet flow radial equilibrium in axial compressor was deduced. It indicates that the blade inlet radial pressure gradient is closely related to the radial component of the circumferential fluctuation (CF source item. Several simplified cascades with/without aerodynamic loading were numerically studied to investigate the effects of blade bowing on the inlet flow radial equilibrium. A data reduction program was conducted to obtain the CF source from three-dimensional (3D simulation results. Flow parameters at the passage inlet were focused on and each term in the radial equilibrium equation was discussed quantitatively. Results indicate that the inviscid blade force is the inducement of the inlet CF due to geometrical asymmetry. Blade bowing induces variation of the inlet CF, thus changes the radial pressure gradient and leads to flow migration before leading edge (LE in the cascades. Positive bowing drives the inlet flow to migrate from end walls to mid-span and negative bowing turns it to the reverse direction to build a new equilibrium. In addition, comparative studies indicate that the inlet Mach number and blade loading can efficiently impact the effectiveness of blade bowing on radial equilibrium in compressor design.
Daoud, Mohamed Ibrahim
. One mechanism was related to sources localized at the height of the vortex centers in the outer-shear layer, which represented direct generation of p' caused by the strong vortex-induced disturbances in the outer part of the flow. The other was located near the wall (y/delta generated by the vortex passage with the strong mean wall shear. It is important to realize that while it is likely that the former mechanism could be modeled by the wall-pressure field associated with quasi-periodic passing of vortices embedded in uniform inviscid flow, the latter mechanism requires proper account of viscous effects near the wall and associated mean shear.
An upwind, kinetic flux-vector splitting method for flows in chemical and thermal non-equilibrium
Eppard, W. M.; Grossman, B.
1993-01-01
We have developed new upwind kinetic difference schemes for flows with non-equilibrium thermodynamics and chemistry. These schemes are derived from the Boltzmann equation with the resulting Euler schemes developed as moments of the discretized Boltzmann scheme with a locally Maxwellian velocity distribution. Splitting the velocity distribution at the Boltzmann level is seen to result in a flux-split Euler scheme and is called Kinetic Flux Vector Splitting (KFVS). Extensions to flows with finite-rate chemistry and vibrational relaxation is accomplished utilizing nonequilibrium kinetic theory. Computational examples are presented comparing KFVS with the schemes of Van Leer and Roe for a quasi-one-dimensional flow through a supersonic diffuser, inviscid flow through two-dimensional inlet, and viscous flow over a cone at zero angle-of-attack. Calculations are also shown for the transonic flow over a bump in a channel and the transonic flow over an NACA 0012 airfoil. The results show that even though the KFVS scheme is a Riemann solver at the kinetic level, its behavior at the Euler level is more similar to the existing flux-vector splitting algorithms than to the flux-difference splitting scheme of Roe.
Investigation of the Unsteady Flow Behaviour on a Wind Turbine Using a BEM and a RANSE Method
Directory of Open Access Journals (Sweden)
Israa Alesbe
2016-01-01
Full Text Available Analyses of the unsteady flow behaviour of a 5 MW horizontal-axis wind turbine (HAWT rotor (Case I and a rotor with tower (Case II are carried out using a panel method and a RANSE method. The panel method calculations are obtained by applying the in-house boundary element method (BEM panMARE code, which is based on the potential flow theory. The BEM is a three-dimensional first-order panel method which can be used for investigating various steady and unsteady flow problems. Viscous flow simulations are carried out by using the RANSE solver ANSYS CFX 14.5. The results of Case I allow for the calculation of the global integral values of the torque and the thrust and include detailed information on the local flow field, such as the pressure distribution on the blade sections and the streamlines. The calculated pressure distribution by the BEM is compared with the corresponding values obtained by the RANSE solver. The tower geometry is considered in the simulation in Case II, so the unsteady forces due to the interaction between the tower and the rotor blades can be calculated. The application of viscous and inviscid flow methods to predict the forces on the HAWT allows for the evaluation of the viscous effects on the calculated HAWT flows.
Parallel discrete vortex methods for viscous flow simulation
Takeda, Kenji
In this thesis a parallel discrete vortex method is developed in order to investigate the long-time behaviour of bluff body wakes. The method is based on inviscid theory, and its extension to include viscous effects is a far from trivial problem. In this work four grid-free viscous models are directly compared to assess their accuracy and efficiency. The random walk, diffusion velocity, corrected core-spreading and vorticity redistribution methods are compared for simulating unbounded fluid flows, and for flows past an impulsively started cylinder at Reynolds numbers between 550 and 9500. The code uses a common core, so that the only free parameters are those directly related to the viscous models. The vorticity redistribution method encompasses all of the advantages of a purely Lagrangian method and incorporates a dynamic regridding scheme to maintain accurate discretisation of the vorticity field. This is used to simulate long-time flow past an impulsively started cylinder for Reynolds numbers 100, 150 and 1000. The code is fully parallel and achieves good speedup on both commodity and proprietary supercomputer systems. At Reynolds numbers below 150 the breakdown of the primary vortex street has been simulated. Results reveal a merging process, causing relaxation to a parallel shear flow. This itself sheds vortices, creating a secondary wake of increased wavelength. At Reynolds number 1000 the cylinder wake becomes chaotic, forming distinct vortex couples. These couples self-convect and can travel upstream. This has a destabilising effect on the vortex street, inducing merging, formation of tripolar and quadrupolar structures and, ultimately, spontaneous ejection of vortex couples upstream of the initial disturbance.
Israel, R.; Rosner, D. E.
1983-01-01
The aerodynamic capture efficiency of small but nondiffusing particles suspended in a high-speed stream flowing past a target is known to be influenced by parameters governing small particle inertia, departures from the Stokes drag law, and carrier fluid compressibility. By defining an effective Stokes number in terms of the actual (prevailing) particle stopping distance, local fluid viscosity, and inviscid fluid velocity gradient at the target nose, it is shown that these effects are well correlated in terms of a 'standard' (cylindrical collector, Stokes drag, incompressible flow, sq rt Re much greater than 1) capture efficiency curve. Thus, a correlation follows that simplifies aerosol capture calculations in the parameter range already included in previous numerical solutions, allows rational engineering predictions of deposition in situations not previously specifically calculated, and should facilitate the presentation of performance data for gas cleaning equipment and aerosol instruments.
Colagrossi, Andrea; Antuono, Matteo; Souto-Iglesias, Antonio; Le Touzé, David
2011-08-01
The theoretical formulation of the smoothed particle hydrodynamics (SPH) method deserves great care because of some inconsistencies occurring when considering free-surface inviscid flows. Actually, in SPH formulations one usually assumes that (i) surface integral terms on the boundary of the interpolation kernel support are neglected, (ii) free-surface conditions are implicitly verified. These assumptions are studied in detail in the present work for free-surface Newtonian viscous flow. The consistency of classical viscous weakly compressible SPH formulations is investigated. In particular, the principle of virtual work is used to study the verification of the free-surface boundary conditions in a weak sense. The latter can be related to the global energy dissipation induced by the viscous term formulations and their consistency. Numerical verification of this theoretical analysis is provided on three free-surface test cases including a standing wave, with the three viscous term formulations investigated.
The stability of two-phase flow over a swept-wing
Coward, Adrian; Hall, Philip
1994-01-01
We use numerical and asymptotic techniques to study the stability of a two-phase air/water flow above a flat porous plate. This flow is a model of the boundary layer which forms on a yawed cylinder and can be used as a useful approximation to the air flow over swept wings during heavy rainfall. We show that the interface between the water and air layers can significantly destabilize the flow, leading to traveling wave disturbances which move along the attachment line. This instability occurs for lower Reynolds numbers than in the case of the absence of a water layer. We also investigate the instability of inviscid stationary modes. We calculate the effective wavenumber and orientation of the stationary disturbance when the fluids have identical physical properties. Using perturbation methods we obtain corrections due to a small stratification in viscosity, thus quantifying the interfacial effects. Our analytical results are in agreement with the numerical solution which we obtain for arbitrary fluid properties.
Boundary layer-shock interaction in hypersonic flows with chemical reaction effects
International Nuclear Information System (INIS)
Mirzaei, M.; Shadaram, A.; Jahantigh, N.
2003-01-01
In this paper, viscous interaction phenomenon in hypersonic flows with chemical reactions is numerically simulated. Two-dimensional Navier-Stokes equations are solved to simulate this phenomenon. Inviscid fluxes are approximated using Van Leer flux vector splitting method and to increase the accuracy of this approximation, MUSCL approach with Van albada limiters is applied. Chemical reactions are considered to be in equilibrium conditions. With this assumption there is no closed form for equation of state for the gas (air) and relation between thermodynamic properties are calculated from thermodynamic tables. In addition, transport properties (viscosity and conductivity) are functions of two independent thermodynamic properties. These functions are calculated using kinetic theory. To evaluate the performance of the model used in this research, some test cases are studied. First test case is flow over a ramp with various angles. The results of this test case are compared with the results of other numerical methods and the effect of geometry on separation length is studied. The second case is a hypersonic flow over a 15-degree ramp. The results are in good agreement compared with experimental data. In addition, there results are compared with the results of ideal gas (non-reacting flow) calculations. It can be seen that ideal gas assumption for air introduces considerable deviation form experimental data. (author)
Second-order small-disturbance solutions for hypersonic flow over power-law bodies
Townsend, J. C.
1975-01-01
Similarity solutions were found which give the adiabatic flow of an ideal gas about two-dimensional and axisymmetric power-law bodies at infinite Mach number to second order in the body slenderness parameter. The flow variables were expressed as a sum of zero-order and perturbation similarity functions for which the axial variations in the flow equations separated out. The resulting similarity equations were integrated numerically. The solutions, which are universal functions, are presented in graphic and tabular form. To avoid a singularity in the calculations, the results are limited to body power-law exponents greater than about 0.85 for the two-dimensional case and 0.75 for the axisymmetric case. Because of the entropy layer induced by the nose bluntness (for power-law bodies other than cones and wedges), only the pressure function is valid at the body surface. The similarity results give excellent agreement with the exact solutions for inviscid flow over wedges and cones having half-angles up to about 20 deg. They give good agreement with experimental shock-wave shapes and surface-pressure distributions for 3/4-power axisymmetric bodies, considering that Mach number and boundary-layer displacement effects are not included in the theory.
Energy Technology Data Exchange (ETDEWEB)
Mullins, O.C.; Dong, C. [Schlumberger-Doll Research Center, Cambridge, MA (United States); Elshahawi, H. [Shell Exploration and Production Company, The Hague (Netherlands)
2008-07-01
This study emphasized the need for considering flow assurance for producing oil and gas, particularly in high cost areas such as deepwater. Phase behaviour studies, sticking propensities, and interfacial interactions have been investigated in many laboratory studies using asphaltenes, wax, hydrates, organic and inorganic scale, and even diamondoids. However, the spatial variation of reservoir fluids has received little attention, despite the fact that it is one of the most important factors affecting flow assurance. This issue was difficult to address in a systematic way in the past because of cost constraints. Today, reservoir fluid variation and flow assurance can be considered at the outset of a project given the technological advances in downhole fluid analysis. This study described the origins of reservoir fluid compositional variations and the controversies surrounding them. It also described the indispensable chemical analytical technology. The impact of these reservoir fluid compositional variations on flow assurance considerations was also discussed. A methodology that accounts for these variations at the outset in flow assurance evaluation was also presented.
Converging shock flows for a Mie-Grüneisen equation of state
Ramsey, Scott D.; Schmidt, Emma M.; Boyd, Zachary M.; Lilieholm, Jennifer F.; Baty, Roy S.
2018-04-01
Previous work has shown that the one-dimensional (1D) inviscid compressible flow (Euler) equations admit a wide variety of scale-invariant solutions (including the famous Noh, Sedov, and Guderley shock solutions) when the included equation of state (EOS) closure model assumes a certain scale-invariant form. However, this scale-invariant EOS class does not include even simple models used for shock compression of crystalline solids, including many broadly applicable representations of Mie-Grüneisen EOS. Intuitively, this incompatibility naturally arises from the presence of multiple dimensional scales in the Mie-Grüneisen EOS, which are otherwise absent from scale-invariant models that feature only dimensionless parameters (such as the adiabatic index in the ideal gas EOS). The current work extends previous efforts intended to rectify this inconsistency, by using a scale-invariant EOS model to approximate a Mie-Grüneisen EOS form. To this end, the adiabatic bulk modulus for the Mie-Grüneisen EOS is constructed, and its key features are used to motivate the selection of a scale-invariant approximation form. The remaining surrogate model parameters are selected through enforcement of the Rankine-Hugoniot jump conditions for an infinitely strong shock in a Mie-Grüneisen material. Finally, the approximate EOS is used in conjunction with the 1D inviscid Euler equations to calculate a semi-analytical Guderley-like imploding shock solution in a metal sphere and to determine if and when the solution may be valid for the underlying Mie-Grüneisen EOS.
AbuAlSaud, Moataz
2012-07-01
The purpose of this thesis is to solve unsteady two-dimensional compressible Navier-Stokes equations for a moving mesh using implicit explicit (IMEX) Runge- Kutta scheme. The moving mesh is implemented in the equations using Arbitrary Lagrangian Eulerian (ALE) formulation. The inviscid part of the equation is explicitly solved using second-order Godunov method, whereas the viscous part is calculated implicitly. We simulate subsonic compressible flow over static NACA-0012 airfoil at different angle of attacks. Finally, the moving mesh is examined via oscillating the airfoil between angle of attack = 0 and = 20 harmonically. It is observed that the numerical solution matches the experimental and numerical results in the literature to within 20%.
MPDATA: Third-order accuracy for variable flows
Waruszewski, Maciej; Kühnlein, Christian; Pawlowska, Hanna; Smolarkiewicz, Piotr K.
2018-04-01
This paper extends the multidimensional positive definite advection transport algorithm (MPDATA) to third-order accuracy for temporally and spatially varying flows. This is accomplished by identifying the leading truncation error of the standard second-order MPDATA, performing the Cauchy-Kowalevski procedure to express it in a spatial form and compensating its discrete representation-much in the same way as the standard MPDATA corrects the first-order accurate upwind scheme. The procedure of deriving the spatial form of the truncation error was automated using a computer algebra system. This enables various options in MPDATA to be included straightforwardly in the third-order scheme, thereby minimising the implementation effort in existing code bases. Following the spirit of MPDATA, the error is compensated using the upwind scheme resulting in a sign-preserving algorithm, and the entire scheme can be formulated using only two upwind passes. Established MPDATA enhancements, such as formulation in generalised curvilinear coordinates, the nonoscillatory option or the infinite-gauge variant, carry over to the fully third-order accurate scheme. A manufactured 3D analytic solution is used to verify the theoretical development and its numerical implementation, whereas global tracer-transport benchmarks demonstrate benefits for chemistry-transport models fundamental to air quality monitoring, forecasting and control. A series of explicitly-inviscid implicit large-eddy simulations of a convective boundary layer and explicitly-viscid simulations of a double shear layer illustrate advantages of the fully third-order-accurate MPDATA for fluid dynamics applications.
The contact angle in inviscid fluid mechanics
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
assumed to start and continue with a uniform pressure over the interface; we will assume the gas to be passive, i.e. it only exerts a constant pressure on the liquid interface. In. §2.1, we write down the equations governing the motion. In §2.2, we first consider planar motions; motions in a cylinder of arbitrary cross-section are ...
Computation of Viscous-Inviscid Interactions
1981-02-01
oO la darivfie de S, augmeute- fortement jusqu’l devenir infinie. Or il eat dana ce cas bien fitabli qu’il slagit d’un pro- blame lig A L£utilisation...extiriaurea, ella se aimplifie pour devenir en =9 n’~tpaa Equivalent A un calcul de couche litnite pour lequel on ae donne lea Epaiaaeura S.Let 91 Dana
Surface shear inviscidity of soluble surfactants.
Zell, Zachary A; Nowbahar, Arash; Mansard, Vincent; Leal, L Gary; Deshmukh, Suraj S; Mecca, Jodi M; Tucker, Christopher J; Squires, Todd M
2014-03-11
Foam and emulsion stability has long been believed to correlate with the surface shear viscosity of the surfactant used to stabilize them. Many subtleties arise in interpreting surface shear viscosity measurements, however, and correlations do not necessarily indicate causation. Using a sensitive technique designed to excite purely surface shear deformations, we make the most sensitive and precise measurements to date of the surface shear viscosity of a variety of soluble surfactants, focusing on SDS in particular. Our measurements reveal the surface shear viscosity of SDS to be below the sensitivity limit of our technique, giving an upper bound of order 0.01 μN·s/m. This conflicts directly with almost all previous studies, which reported values up to 10(3)-10(4) times higher. Multiple control and complementary measurements confirm this result, including direct visualization of monolayer deformation, for SDS and a wide variety of soluble polymeric, ionic, and nonionic surfactants of high- and low-foaming character. No soluble, small-molecule surfactant was found to have a measurable surface shear viscosity, which seriously undermines most support for any correlation between foam stability and surface shear rheology of soluble surfactants.
Inviscid incompressible limits for rotating fluids
Czech Academy of Sciences Publication Activity Database
Caggio, Matteo; Nečasová, Šárka
2017-01-01
Roč. 163, November (2017), s. 1-18 ISSN 0362-546X R&D Projects: GA ČR GA16-03230S Institutional support: RVO:67985840 Keywords : compressible Navier -Stokces system * rotating fluids * incompressible limit Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.192, year: 2016 http://www.sciencedirect.com/science/article/pii/S0362546X17301815?via%3Dihub
Inviscid incompressible limits of strongly stratified fluids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Jin, B.J.; Novotný, A.
2014-01-01
Roč. 89, 3-4 (2014), s. 307-329 ISSN 0921-7134 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : compressible Navier-Stokes system * anelastic approximation * stratified fluid Subject RIV: BA - General Mathematics Impact factor: 0.528, year: 2014 http://iospress.metapress.com/content/d71255745tl50125/?p=969b60ae82634854ab8bd25505ce1f71&pi=3
Inviscid incompressible limits for rotating fluids
Czech Academy of Sciences Publication Activity Database
Caggio, Matteo; Nečasová, Šárka
2017-01-01
Roč. 163, November (2017), s. 1-18 ISSN 0362-546X R&D Projects: GA ČR GA16-03230S Institutional support: RVO:67985840 Keywords : compressible Navier-Stokces system * rotating fluids * incompressible limit Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.192, year: 2016 http://www.sciencedirect.com/science/article/pii/S0362546X17301815?via%3Dihub
High order methods for incompressible fluid flow: Application to moving boundary problems
Energy Technology Data Exchange (ETDEWEB)
Bjoentegaard, Tormod
2008-04-15
Fluid flows with moving boundaries are encountered in a large number of real life situations, with two such types being fluid-structure interaction and free-surface flows. Fluid-structure phenomena are for instance apparent in many hydrodynamic applications; wave effects on offshore structures, sloshing and fluid induced vibrations, and aeroelasticity; flutter and dynamic response. Free-surface flows can be considered as a special case of a fluid-fluid interaction where one of the fluids are practically inviscid, such as air. This type of flows arise in many disciplines such as marine hydrodynamics, chemical engineering, material processing, and geophysics. The driving forces for free-surface flows may be of large scale such as gravity or inertial forces, or forces due to surface tension which operate on a much smaller scale. Free-surface flows with surface tension as a driving mechanism include the flow of bubbles and droplets, and the evolution of capillary waves. In this work we consider incompressible fluid flow, which are governed by the incompressible Navier-Stokes equations. There are several challenges when simulating moving boundary problems numerically, and these include - Spatial discretization - Temporal discretization - Imposition of boundary conditions - Solution strategy for the linear equations. These are some of the issues which will be addressed in this introduction. We will first formulate the problem in the arbitrary Lagrangian-Eulerian framework, and introduce the weak formulation of the problem. Next, we discuss the spatial and temporal discretization before we move to the imposition of surface tension boundary conditions. In the final section we discuss the solution of the resulting linear system of equations. (Author). refs., figs., tabs
DEFF Research Database (Denmark)
Mitarai, Namiko; Nakanishi, Hiizu
2012-01-01
Granular material is a collection of macroscopic particles that are visible with naked eyes. The non-equilibrium nature of the granular materials makes their rheology quite different from that of molecular systems. In this minireview, we present the unique features of granular materials focusing ...... on the shear flow of dry granular materials and granule-liquid mixture....
Papanastasiou, Tasos C.
1989-01-01
Discusses fluid mechanics for undergraduates including the differential Navier-Stokes equations, dimensional analysis and simplified dimensionless numbers, control volume principles, the Reynolds lubrication equation for confined and free surface flows, capillary pressure, and simplified perturbation techniques. Provides a vertical dip coating…
A Curvature Flow Unifying Symplectic Curvature Flow And Pluriclosed Flow
Dai, Song
2013-01-01
Streets and Tian introduced pluriclosed flow and symplectic curvature flow in recent years. Here we construct a curvature flow to unify these two flows. We show the short time existence of our flow and exhibit an obstruction to long time existence.
Numerical simulation of weakly ionized hypersonic flow over reentry capsules
Scalabrin, Leonardo C.
The mathematical and numerical formulation employed in the development of a new multi-dimensional Computational Fluid Dynamics (CFD) code for the simulation of weakly ionized hypersonic flows in thermo-chemical non-equilibrium over reentry configurations is presented. The flow is modeled using the Navier-Stokes equations modified to include finite-rate chemistry and relaxation rates to compute the energy transfer between different energy modes. The set of equations is solved numerically by discretizing the flowfield using unstructured grids made of any mixture of quadrilaterals and triangles in two-dimensions or hexahedra, tetrahedra, prisms and pyramids in three-dimensions. The partial differential equations are integrated on such grids using the finite volume approach. The fluxes across grid faces are calculated using a modified form of the Steger-Warming Flux Vector Splitting scheme that has low numerical dissipation inside boundary layers. The higher order extension of inviscid fluxes in structured grids is generalized in this work to be used in unstructured grids. Steady state solutions are obtained by integrating the solution over time implicitly. The resulting sparse linear system is solved by using a point implicit or by a line implicit method in which a tridiagonal matrix is assembled by using lines of cells that are formed starting at the wall. An algorithm that assembles these lines using completely general unstructured grids is developed. The code is parallelized to allow simulation of computationally demanding problems. The numerical code is successfully employed in the simulation of several hypersonic entry flows over space capsules as part of its validation process. Important quantities for the aerothermodynamics design of capsules such as aerodynamic coefficients and heat transfer rates are compared to available experimental and flight test data and other numerical results yielding very good agreement. A sensitivity analysis of predicted radiative
DEFF Research Database (Denmark)
Olsen, Jesper Lind
2003-01-01
Flow Game er et dialogspil, der kan bruges som ledelsesværktøj, ledertræning, samtaletræning, coachingtræning og ideudvikling m.m. Gennem dilemmakort provokeres en dialog og teori-U inspireret afklaring- og udviklingsproces, hvor der enten arbejdes på en gruppes eller et individs vision/innovatio......Flow Game er et dialogspil, der kan bruges som ledelsesværktøj, ledertræning, samtaletræning, coachingtræning og ideudvikling m.m. Gennem dilemmakort provokeres en dialog og teori-U inspireret afklaring- og udviklingsproces, hvor der enten arbejdes på en gruppes eller et individs vision...
DEFF Research Database (Denmark)
Kabel, Lars
2016-01-01
News and other kinds of journalistic stories, 16-17 hours a day, all year round, on all platforms, also the moderated social media. The key research thesis behind this article is that the continuous and speedy stream of news stories and media content now is becoming the centre of the production...... processes and the value creation in converged multimedia newsrooms. The article identify new methods and discuss editorial challenges in handling media flow....
1988-12-01
n Vlog n ), which is a linear time algorithm for all but the sparsest classes of shortest path problems. 3.4. Label Correcting Algorithms Label...11962] (Programming , Games and Transportation Networks), Iri (1969] (Network Flows, Transportation and Scheduling), Hu [1969] (Integer Programming and...though the improvements are not as dramatic as they have been for E>inic’s and the FIFO preflow push algorithms. For example, the 0(nm + n^ Vlog U
Munafò, A; Panesi, M; Magin, T E
2014-02-01
A Boltzmann rovibrational collisional coarse-grained model is proposed to reduce a detailed kinetic mechanism database developed at NASA Ames Research Center for internal energy transfer and dissociation in N(2)-N interactions. The coarse-grained model is constructed by lumping the rovibrational energy levels of the N(2) molecule into energy bins. The population of the levels within each bin is assumed to follow a Boltzmann distribution at the local translational temperature. Excitation and dissociation rate coefficients for the energy bins are obtained by averaging the elementary rate coefficients. The energy bins are treated as separate species, thus allowing for non-Boltzmann distributions of their populations. The proposed coarse-grained model is applied to the study of nonequilibrium flows behind normal shock waves and within converging-diverging nozzles. In both cases, the flow is assumed inviscid and steady. Computational results are compared with those obtained by direct solution of the master equation for the rovibrational collisional model and a more conventional multitemperature model. It is found that the proposed coarse-grained model is able to accurately resolve the nonequilibrium dynamics of internal energy excitation and dissociation-recombination processes with only 20 energy bins. Furthermore, the proposed coarse-grained model provides a superior description of the nonequilibrium phenomena occurring in shock heated and nozzle flows when compared with the conventional multitemperature models.
An implicit multigrid algorithm for computing hypersonic, chemically reacting viscous flows
International Nuclear Information System (INIS)
Edwards, J.R.
1996-01-01
An implicit algorithm for computing viscous flows in chemical nonequilibrium is presented. Emphasis is placed on the numerical efficiency of the time integration scheme, both in terms of periteration workload and overall convergence rate. In this context, several techniques are introduced, including a stable, O(m 2 ) approximate factorization of the chemical source Jacobian and implementations of V-cycle and filtered multigrid acceleration methods. A five species-seventeen reaction air model is used to calculate hypersonic viscous flow over a cylinder at conditions corresponding to flight at 5 km/s, 60 km altitude and at 11.36 km/s, 76.42 km altitude. Inviscid calculations using an eleven-species reaction mechanism including ionization are presented for a case involving 11.37 km/s flow at an altitude of 84.6 km. Comparisons among various options for the implicit treatment of the chemical source terms and among different multilevel approaches for convergence acceleration are presented for all simulations
Viscous potential flow analysis of magnetohydrodynamic interfacial stability through porous media
International Nuclear Information System (INIS)
Obied Allah, M.H.
2013-01-01
In the view of viscous potential flow theory, the hydromagnetic stability of the interface between two infinitely conducting, incompressible plasmas, streaming parallel to the interface and subjected to a constant magnetic field parallel to the streaming direction will be considered. The plasmas are flowing through porous media between two rigid planes and surface tension is taken into account. A general dispersion relation is obtained analytically and solved numerically. For Kelvin-Helmholtz instability problem, the stability criterion is given by a critical value of the relative velocity. On the other hand, a comparison between inviscid and viscous potential flow solutions has been made and it has noticed that viscosity plays a dual role, destabilizing for Rayleigh-Taylor problem and stabilizing for Kelvin-Helmholtz. For Rayleigh-Taylor instability, a new dispersion relation has been obtained in terms of a critical wave number. It has been found that magnetic field, surface tension, and rigid planes have stabilizing effects, whereas critical wave number and porous media have destabilizing effects. (author)
Bounds on dissipation in stress driven flow in a rotating frame
Tang, W.; Caulfield, C. P.; Young, W. R.
2004-11-01
We calculate the optimal upper bound and a rigorous lower bound, subject to the assumption of streamwise invariance, on the long-time-averaged mechanical energy dissipation rate l E within the rotating flow of an incompressible viscous fluid of constant kinematic viscosity ν, depth h and rotational rate f, driven by a constant surface stress τ=ρ u^2_*, where u_* is the friction velocity. We show that l E ≤ l E_max=l E_Stokes, i.e. the dissipation is bounded above by the dissipation associated with the Stokes flow. Using an approach similar to the variational ``background method'', we also generate a rigorous lower bound on the energy dissipation rate, subject to the constraints of total power balance and streamwise momentum balance, in the inviscid limit for fixed values of GE^2, where G=τ h^2/(ρ ν^2) is the Grashof number and E=ν/fh^2 is the Ekman number. Assuming streamwise invariance as G arrow ∞ or equivalently Earrow 0, and by restricting our attention to utilizing a particular, analytically tractable, class of background shear profiles as the Lagrangian multiplier imposing mean streamwise momentum balance, we show that l E ≥ l E_min=2√3 u_*^3/h, a bound that is independent of the flow viscosity.
Theory and Low-Order Modeling of Unsteady Airfoil Flows
Ramesh, Kiran
Unsteady flow phenomena are prevalent in a wide range of problems in nature and engineering. These include, but are not limited to, aerodynamics of insect flight, dynamic stall in rotorcraft and wind turbines, leading-edge vortices in delta wings, micro-air vehicle (MAV) design, gust handling and flow control. The most significant characteristics of unsteady flows are rapid changes in the circulation of the airfoil, apparent-mass effects, flow separation and the leading-edge vortex (LEV) phenomenon. Although experimental techniques and computational fluid dynamics (CFD) methods have enabled the detailed study of unsteady flows and their underlying features, a reliable and inexpensive loworder method for fast prediction and for use in control and design is still required. In this research, a low-order methodology based on physical principles rather than empirical fitting is proposed. The objective of such an approach is to enable insights into unsteady phenomena while developing approaches to model them. The basis of the low-order model developed here is unsteady thin-airfoil theory. A time-stepping approach is used to solve for the vorticity on an airfoil camberline, allowing for large amplitudes and nonplanar wakes. On comparing lift coefficients from this method against data from CFD and experiments for some unsteady test cases, it is seen that the method predicts well so long as LEV formation does not occur and flow over the airfoil is attached. The formation of leading-edge vortices (LEVs) in unsteady flows is initiated by flow separation and the formation of a shear layer at the airfoil's leading edge. This phenomenon has been observed to have both detrimental (dynamic stall in helicopters) and beneficial (high-lift flight in insects) effects. To predict the formation of LEVs in unsteady flows, a Leading Edge Suction Parameter (LESP) is proposed. This parameter is calculated from inviscid theory and is a measure of the suction at the airfoil's leading edge. It
Kirk, Helen
2014-07-01
Observations over the last few years, especially those from the Herschel Space Telescope have shown that filaments are intimately connected with dense cores. Both theory and observations are starting to suggest that filaments may provide an important reservoir of material both in the accretion of relatively isolated dense cores found along filaments, as well cluster-forming cores, which tend to be found at the junction of multiple filaments. I will review some of the recent evidence of gas flows in filaments, highlighting results from the young Serpens South cluster-forming region. I will also touch on recent analysis of numerical simulations which suggests a similar behavior.
Organized Oscillations of Initially-Turbulent Flow Past a Cavity
Energy Technology Data Exchange (ETDEWEB)
J.C. Lin; D. Rockwell
2002-09-17
Flow past an open cavity is known to give rise to self-sustained oscillations in a wide variety of configurations, including slotted-wall, wind and water tunnels, slotted flumes, bellows-type pipe geometries, high-head gates and gate slots, aircraft components and internal piping systems. These cavity-type oscillations are the origin of coherent and broadband sources of noise and, if the structure is sufficiently flexible, flow-induced vibration as well. Moreover, depending upon the state of the cavity oscillation, substantial alterations of the mean drag may be induced. In the following, the state of knowledge of flow past cavities, based primarily on laminar inflow conditions, is described within a framework based on the flow physics. Then, the major unresolved issues for this class of flows will be delineated. Self-excited cavity oscillations have generic features, which are assessed in detail in the reviews of Rockwell and Naudascher, Rockwell, Howe and Rockwell. These features, which are illustrated in the schematic of Figure 1, are: (i) interaction of a vorticity concentration(s) with the downstream corner, (ii) upstream influence from this corner interaction to the sensitive region of the shear layer formed from the upstream corner of the cavity; (iii) conversion of the upstream influence arriving at this location to a fluctuation in the separating shear layer; and (iv) amplification of this fluctuation in the shear layer as it develops in the streamwise direction. In view of the fact that inflow shear-layer in the present investigation is fully turbulent, item (iv) is of particular interest. It is generally recognized, at least for laminar conditions at separation from the leading-corner of the cavity, that the disturbance growth in the shear layer can be described using concepts of linearized, inviscid stability theory, as shown by Rockwell, Sarohia, and Knisely and Rockwell. As demonstrated by Knisely and Rockwell, on the basis of experiments interpreted
STANDING SHOCK INSTABILITY IN ADVECTION-DOMINATED ACCRETION FLOWS
Energy Technology Data Exchange (ETDEWEB)
Le, Truong [Department of Physics, Astronomy and Geology, Berry College, Mount Berry, GA 30149 (United States); Wood, Kent S.; Wolff, Michael T. [High Energy Space Environment Branch, Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Becker, Peter A. [Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030 (United States); Putney, Joy, E-mail: tle@berry.edu [Department of Physics and Engineering, Washington and Lee University, Lexington, VA 24450 (United States)
2016-03-10
Depending on the values of the energy and angular momentum per unit mass in the gas supplied at large radii, inviscid advection-dominated accretion flows can display velocity profiles with either preshock deceleration or preshock acceleration. Nakayama has shown that these two types of flow configurations are expected to have different stability properties. By employing the Chevalier and Imamura linearization method and the Nakayama instability boundary conditions, we discover that there are regions of parameter space where disks/shocks with outflows can be stable or unstable. In regions of instability, we find that preshock deceleration is always unstable to the zeroth mode with zero frequency of oscillation, but is always stable to the fundamental mode and overtones. Furthermore, we also find that preshock acceleration is always unstable to the zeroth mode and that the fundamental mode and overtones become increasingly less stable as the shock location moves away from the horizon when the disk half-height expands above ∼12 gravitational radii at the shock radius. In regions of stability, we demonstrate the zeroth mode to be stable for the velocity profiles that exhibit preshock acceleration and deceleration. Moreover, for models that are linearly unstable, our model suggests the possible existence of quasi-periodic oscillations (QPOs) with ratios 2:3 and 3:5. These ratios are believed to occur in stellar and supermassive black hole candidates, for example, in GRS 1915+105 and Sgr A*, respectively. We expect that similar QPO ratios also exist in regions of stable shocks.
Dvorak, F. A.; Woodward, F. A.
1974-01-01
An analysis method and computer program have been developed for the calculation of the viscosity dependent aerodynamic characteristics of multi-element infinite swept wings in incompressible flow. The wing configuration consisting at the most of a slat, a main element and double slotted flap is represented in the method by a large number of panels. The inviscid pressure distribution about a given configuration in the normal chord direction is determined using a two dimensional potential flow program employing a vortex lattice technique. The boundary layer development over each individual element of the high lift configuration is determined using either integral or finite difference boundary layer techniques. A source distribution is then determined as a function of the calculated boundary layer displacement thickness and pressure distributions. This source distribution is included in the second calculation of the potential flow about the configuration. Once the solution has converged (usually after 2-5 iterations between the potential flow and boundary layer calculations) lift, drag, and pitching moments can be determined as functions of Reynolds number.
A numerical model of two-phase flow at the micro-scale using the volume-of-fluid method
Shams, Mosayeb; Raeini, Ali Q.; Blunt, Martin J.; Bijeljic, Branko
2018-03-01
This study presents a simple and robust numerical scheme to model two-phase flow in porous media where capillary forces dominate over viscous effects. The volume-of-fluid method is employed to capture the fluid-fluid interface whose dynamics is explicitly described based on a finite volume discretization of the Navier-Stokes equations. Interfacial forces are calculated directly on reconstructed interface elements such that the total curvature is preserved. The computed interfacial forces are explicitly added to the Navier-Stokes equations using a sharp formulation which effectively eliminates spurious currents. The stability and accuracy of the implemented scheme is validated on several two- and three-dimensional test cases, which indicate the capability of the method to model two-phase flow processes at the micro-scale. In particular we show how the co-current flow of two viscous fluids leads to greatly enhanced flow conductance for the wetting phase in corners of the pore space, compared to a case where the non-wetting phase is an inviscid gas.
Energy Technology Data Exchange (ETDEWEB)
Casalis, G.; Robinet, J.Ch. [Office National d`Etudes et de Recherches Aerospatiales (ONERA), 31 - Toulouse (France). Centre d`Etudes et de Recherches
1998-01-01
The purpose of this paper is to give the first results of a linear stability analysis which has been applied to the problem of shock oscillations in a transonic diffuser flow. The mean flow is calculated with a numerical code solving the averaged Navier-Stockes equations, but the proposed stability approach is limited to the core region where the viscous effects can be neglected. In order to validate the present approach, the results are compared with Sahben`s experimental results and those numerically obtained Liou and Coakley. It is the first time that these published results are compared with a simple linear stability analysis. As demonstrated below, the shock motion spectra have been correctly reproduced and the frequencies of 200 Hz and 300 Hz have been clearly obtained for the diffuser lengths of l/h = 13 and l/h 8.6 respectively. As far as stability of the mean flow is concerned, the temporal amplification rate is always negative, the mean flow is therefore linearly stable. Finally, the amplitude and phase of the fluctuating pressure have been compared. The phase of example is in very good agreement with the experimental results. This can prove that at least in some cases, self-sustained shock oscillations can be explained and predicted with an inviscid linear stability analysis. (authors) 11 refs.
Erdos, J. I.; Alzner, E.
1977-01-01
A numerical method of solution of the inviscid, compressible, two-dimensional unsteady flow on a blade-to-blade stream surface through a stage (rotor and stator) or a single blade row of an axial flow compressor or fan is described. A cyclic procedure has been developed for representation of adjacent blade-to-blade passages which asymptotically achieves the correct phase between all passages of a stage. A shock-capturing finite difference method is employed in the interior of the passage, and a method of characteristics technique is used at the boundaries. The blade slipstreams form two of the passage boundaries and are treated as moving contact surfaces capable of supporting jumps in entropy and tangential velocity. The Kutta condition is imposed by requiring the slipstreams to originate at the trailing edges, which are assumed to be sharp. Results are presented for several transonic fan rotors and compared with available experimental data, consisting of holographic observations of shock structure and pressure contour maps. A subcritical stator solution is also compared with results from a relaxation method. Finally, a periodic solution for a stage consisting of 44 rotor blades and 46 stator blades is discussed.
Computer analysis of flow perturbations generated by placement of choke bumps in a wind tunnel
Campbell, R. L.
1981-01-01
An inviscid analytical study was conducted to determine the upstream flow perturbations caused by placing choke bumps in a wind tunnel. A computer program based on the stream-tube curvature method was used to calculate the resulting flow fields for a nominal free-stream Mach number range of 0.6 to 0.9. The choke bump geometry was also varied to investigate the effect of bump shape on the disturbance produced. Results from the study indicate that a region of significant variation from the free-stream conditions exists upstream of the throat of the tunnel. The extent of the disturbance region was, as a rule, dependent on Mach number and the geometry of the choke bump. In general, the upstream disturbance distance decreased for increasing nominal free-stream Mach number and for decreasing length-to-height ratio of the bump. A polynomial-curve choke bump usually produced less of a disturbance than did a circular-arc bump and going to an axisymmetric configuration (modeling choke bumps on all the tunnel walls) generally resulted in a lower disturbance than with the corresponding two dimensional case.
Generalized derivation of the added-mass and circulatory forces for viscous flows
Limacher, Eric; Morton, Chris; Wood, David
2018-01-01
The concept of added mass arises from potential flow analysis and is associated with the acceleration of a body in an inviscid irrotational fluid. When shed vorticity is modeled as vortex singularities embedded in this irrotational flow, the associated force can be superimposed onto the added-mass force due to the linearity of the governing Laplace equation. This decomposition of force into added-mass and circulatory components remains common in modern aerodynamic models, but its applicability to viscous separated flows remains unclear. The present work addresses this knowledge gap by presenting a generalized derivation of the added-mass and circulatory force decomposition which is valid for a body of arbitrary shape in an unbounded, incompressible fluid domain, in both two and three dimensions, undergoing arbitrary motions amid continuous distributions of vorticity. From the general expression, the classical added-mass force is rederived for well-known canonical cases and is seen to be additive to the circulatory force for any flow. The formulation is shown to be equivalent to existing theoretical work under the specific conditions and assumptions of previous studies. It is also validated using a numerical simulation of a pitching plate in a steady freestream flow, conducted by Wang and Eldredge [Theor. Comput. Fluid Dyn. 27, 577 (2013), 10.1007/s00162-012-0279-5]. In response to persistent confusion in the literature, a discussion of the most appropriate physical interpretation of added mass is included, informed by inspection of the derived equations. The added-mass force is seen to account for the dynamic effect of near-body vorticity and is not (as is commonly claimed) associated with the acceleration of near-body fluid which "must" somehow move with the body. Various other consequences of the derivation are discussed, including a concept which has been labeled the conservation of image-vorticity impulse.
Numerical Solution of the Flow of a Perfect Gas Over A Circular Cylinder at Infinite Mach Number
Hamaker, Frank M.
1959-01-01
A solution for the two-dimensional flow of an inviscid perfect gas over a circular cylinder at infinite Mach number is obtained by numerical methods of analysis. Nonisentropic conditions of curved shock waves and vorticity are included in the solution. The analysis is divided into two distinct regions, the subsonic region which is analyzed by the relaxation method of Southwell and the supersonic region which was treated by the method of characteristics. Both these methods of analysis are inapplicable on the sonic line which is therefore considered separately. The shapes of the sonic line and the shock wave are obtained by iteration techniques. The striking result of the solution is the strong curvature of the sonic line and of the other lines of constant Mach number. Because of this the influence of the supersonic flow on the sonic line is negligible. On comparison with Newtonian flow methods, it is found that the approximate methods show a larger variation of surface pressure than is given by the present solution.
Xu, Li; Weng, Peifen
2014-02-01
An improved fifth-order weighted essentially non-oscillatory (WENO-Z) scheme combined with the moving overset grid technique has been developed to compute unsteady compressible viscous flows on the helicopter rotor in forward flight. In order to enforce periodic rotation and pitching of the rotor and relative motion between rotor blades, the moving overset grid technique is extended, where a special judgement standard is presented near the odd surface of the blade grid during search donor cells by using the Inverse Map method. The WENO-Z scheme is adopted for reconstructing left and right state values with the Roe Riemann solver updating the inviscid fluxes and compared with the monotone upwind scheme for scalar conservation laws (MUSCL) and the classical WENO scheme. Since the WENO schemes require a six point stencil to build the fifth-order flux, the method of three layers of fringes for hole boundaries and artificial external boundaries is proposed to carry out flow information exchange between chimera grids. The time advance on the unsteady solution is performed by the full implicit dual time stepping method with Newton type LU-SGS subiteration, where the solutions of pseudo steady computation are as the initial fields of the unsteady flow computation. Numerical results on non-variable pitch rotor and periodic variable pitch rotor in forward flight reveal that the approach can effectively capture vortex wake with low dissipation and reach periodic solutions very soon.
Goldman, Louis J.
1993-01-01
An advanced laser anemometer (LA) was used to measure the axial and tangential velocity components in an annular cascade of turbine stator vanes operating at transonic flow conditions. The vanes tested were based on a previous redesign of the first-stage stator in a two-stage turbine for a high-bypass-ratio engine. The vanes produced 75 deg of flow turning. Tests were conducted on a 0.771-scale model of the engine-sized stator. The advanced LA fringe system employed an extremely small 50-micron diameter probe volume. Window correction optics were used to ensure that the laser beams did not uncross in passing through the curved optical access port. Experimental LA measurements of velocity and turbulence were obtained at the mean radius upstream of, within, and downstream of the stator vane row at an exit critical velocity ratio of 1.050 at the hub. Static pressures were also measured on the vane surface. The measurements are compared, where possible, with calculations from a three-dimensional inviscid flow analysis. Comparisons were also made with the results obtained previously when these same vanes were tested at the design exit critical velocity ratio of 0.896 at the hub. The data are presented in both graphical and tabulated form so that they can be readily compared against other turbomachinery computations.
Sengupta, Tapan K.; Gullapalli, Atchyut
2016-11-01
Spinning cylinder rotating about its axis experiences a transverse force/lift, an account of this basic aerodynamic phenomenon is known as the Robins-Magnus effect in text books. Prandtl studied this flow by an inviscid irrotational model and postulated an upper limit of the lift experienced by the cylinder for a critical rotation rate. This non-dimensional rate is the ratio of oncoming free stream speed and the surface speed due to rotation. Prandtl predicted a maximum lift coefficient as CLmax = 4π for the critical rotation rate of two. In recent times, evidences show the violation of this upper limit, as in the experiments of Tokumaru and Dimotakis ["The lift of a cylinder executing rotary motions in a uniform flow," J. Fluid Mech. 255, 1-10 (1993)] and in the computed solution in Sengupta et al. ["Temporal flow instability for Magnus-robins effect at high rotation rates," J. Fluids Struct. 17, 941-953 (2003)]. In the latter reference, this was explained as the temporal instability affecting the flow at higher Reynolds number and rotation rates (>2). Here, we analyze the flow past a rotating cylinder at a super-critical rotation rate (=2.5) by the enstrophy-based proper orthogonal decomposition (POD) of direct simulation results. POD identifies the most energetic modes and helps flow field reconstruction by reduced number of modes. One of the motivations for the present study is to explain the shedding of puffs of vortices at low Reynolds number (Re = 60), for the high rotation rate, due to an instability originating in the vicinity of the cylinder, using the computed Navier-Stokes equation (NSE) from t = 0 to t = 300 following an impulsive start. This instability is also explained through the disturbance mechanical energy equation, which has been established earlier in Sengupta et al. ["Temporal flow instability for Magnus-robins effect at high rotation rates," J. Fluids Struct. 17, 941-953 (2003)].
Adaptive finite element simulation of flow and transport applications on parallel computers
Kirk, Benjamin Shelton
design and to demonstrate the capability for resolving complex multiscale processes efficiently and reliably. The first application considered is the simulation of chemotactic biological systems such as colonies of Escherichia coli. This work appears to be the first application of AMR to chemotactic processes. These systems exhibit transient, highly localized features and are important in many biological processes, which make them ideal for simulation with adaptive techniques. A nonlinear reaction-diffusion model for such systems is described and a finite element formulation is developed. The solution methodology is described in detail. Several phenomenological studies are conducted to study chemotactic processes and resulting biological patterns which use the parallel adaptive refinement capability developed in this work. The other application study is much more extensive and deals with fine scale interactions for important hypersonic flows arising in aerospace applications. These flows are characterized by highly nonlinear, convection-dominated flowfields with very localized features such as shock waves and boundary layers. These localized features are well-suited to simulation with adaptive techniques. A novel treatment of the inviscid flux terms arising in a streamline-upwind Petrov-Galerkin finite element formulation of the compressible Navier-Stokes equations is also presented and is found to be superior to the traditional approach. The parallel adaptive finite element formulation is then applied to several complex flow studies, culminating in fully three-dimensional viscous flows about complex geometries such as the Space Shuttle Orbiter. Physical phenomena such as viscous/inviscid interaction, shock wave/boundary layer interaction, shock/shock interaction, and unsteady acoustic-driven flowfield response are considered in detail. A computational investigation of a 25°/55° double cone configuration details the complex multiscale flow features and investigates a
... Home Flow of Aqueous Humor Flow of Aqueous Humor Most, but not all, forms of glaucoma are ... remains normal when some of the fluid (aqueous humor) produced by the eye's ciliary body flows out ...
Instability modes on a solid-body-rotation flow in a finite-length pipe
Directory of Open Access Journals (Sweden)
Chunjuan Feng
2017-09-01
Full Text Available Numerical solutions of the incompressible Navier-Stokes equations are obtained to study the time evolution of both axisymmetric and three-dimensional perturbations to a base solid-body-rotation flow in a finite-length pipe with non-periodic boundary conditions imposed at the pipe inlet and outlet. It is found that for a given Reynolds number there exists a critical swirl number beyond which the initial perturbations grow, in contrast to the solid-body rotation flow in an infinitely-long pipe or a finite-length pipe with periodic inlet and exit boundary conditions for which the classical Kelvin analysis and Rayleigh stability criterion affirm neutrally stable for all levels of swirl. This paper uncovers for the first time the detailed evolution of the perturbations in both the axisymmetric and three-dimensional situations. The computations reveal a linear growth stage of the perturbations with a constant growth rate after a brief initial period of decay of the imposed initial perturbations. The fastest growing axisymmetric and three-dimensional instability modes and the associated growth rates are identified numerically for the first time. The computations show that the critical swirl number increases and the growth rate of instability decreases at the same swirl number with decreasing Reynolds number. The growth rate of the axisymmetric mode at high Reynolds number agrees well with previous stability theory for inviscid flow. More importantly, three-dimensional simulations uncover that the most unstable mode is the spiral type m = 1 mode, which appears at a lower critical swirl number than that for the onset of the axisymmetric mode. This spiral mode grows faster than the unstable axisymmetric mode at the same swirl. Moreover, the computations reveal that after the linear growing stage of the perturbation the flow continues to evolve nonlinearly to a saturated axisymmetric vortex breakdown state.
Diwakar, S. V.; Das, Sarit K.; Sundararajan, T.
2009-12-01
A new Quadratic Spline based Interface (QUASI) reconstruction algorithm is presented which provides an accurate and continuous representation of the interface in a multiphase domain and facilitates the direct estimation of local interfacial curvature. The fluid interface in each of the mixed cells is represented by piecewise parabolic curves and an initial discontinuous PLIC approximation of the interface is progressively converted into a smooth quadratic spline made of these parabolic curves. The conversion is achieved by a sequence of predictor-corrector operations enforcing function ( C0) and derivative ( C1) continuity at the cell boundaries using simple analytical expressions for the continuity requirements. The efficacy and accuracy of the current algorithm has been demonstrated using standard test cases involving reconstruction of known static interface shapes and dynamically evolving interfaces in prescribed flow situations. These benchmark studies illustrate that the present algorithm performs excellently as compared to the other interface reconstruction methods available in literature. Quadratic rate of error reduction with respect to grid size has been observed in all the cases with curved interface shapes; only in situations where the interface geometry is primarily flat, the rate of convergence becomes linear with the mesh size. The flow algorithm implemented in the current work is designed to accurately balance the pressure gradients with the surface tension force at any location. As a consequence, it is able to minimize spurious flow currents arising from imperfect normal stress balance at the interface. This has been demonstrated through the standard test problem of an inviscid droplet placed in a quiescent medium. Finally, the direct curvature estimation ability of the current algorithm is illustrated through the coupled multiphase flow problem of a deformable air bubble rising through a column of water.
Instability modes on a solid-body-rotation flow in a finite-length pipe
Feng, Chunjuan; Liu, Feng; Rusak, Zvi; Wang, Shixiao
2017-09-01
Numerical solutions of the incompressible Navier-Stokes equations are obtained to study the time evolution of both axisymmetric and three-dimensional perturbations to a base solid-body-rotation flow in a finite-length pipe with non-periodic boundary conditions imposed at the pipe inlet and outlet. It is found that for a given Reynolds number there exists a critical swirl number beyond which the initial perturbations grow, in contrast to the solid-body rotation flow in an infinitely-long pipe or a finite-length pipe with periodic inlet and exit boundary conditions for which the classical Kelvin analysis and Rayleigh stability criterion affirm neutrally stable for all levels of swirl. This paper uncovers for the first time the detailed evolution of the perturbations in both the axisymmetric and three-dimensional situations. The computations reveal a linear growth stage of the perturbations with a constant growth rate after a brief initial period of decay of the imposed initial perturbations. The fastest growing axisymmetric and three-dimensional instability modes and the associated growth rates are identified numerically for the first time. The computations show that the critical swirl number increases and the growth rate of instability decreases at the same swirl number with decreasing Reynolds number. The growth rate of the axisymmetric mode at high Reynolds number agrees well with previous stability theory for inviscid flow. More importantly, three-dimensional simulations uncover that the most unstable mode is the spiral type m = 1 mode, which appears at a lower critical swirl number than that for the onset of the axisymmetric mode. This spiral mode grows faster than the unstable axisymmetric mode at the same swirl. Moreover, the computations reveal that after the linear growing stage of the perturbation the flow continues to evolve nonlinearly to a saturated axisymmetric vortex breakdown state.
Relaminarization of fluid flows
International Nuclear Information System (INIS)
Narasimha, R.; Sreenivasan, K.R.
1979-01-01
The mechanisms of the relaminarization of turbulent flows are investigated with a view to establishing any general principles that might govern them. Three basic archetypes of reverting flows are considered: the dissipative type, the absorptive type, and the Richardson type exemplified by a turbulent boundary layer subjected to severe acceleration. A number of other different reverting flows are then considered in the light of the analysis of these archetypes, including radial Poiseuille flow, convex boundary layers, flows reverting by rotation, injection, and suction, as well as heated horizontal and vertical gas flows. Magnetohydrodynamic duct flows are also examined. Applications of flow reversion for turbulence control are discussed
Energy Technology Data Exchange (ETDEWEB)
Adoua, S.R
2007-07-15
This work is devoted to the study of an oblate spheroidal bubble of prescribed shape set fixed in a linear shear flow using direct numerical simulation. The three dimensional Navier-Stokes equations are solved in orthogonal curvilinear coordinates using a finite volume method. The bubble response is studied over a wide range of the aspect ratio (1-2.7), the bubble Reynolds number (50-2000) and the non-dimensional shear rate (0.-1.2). The numerical simulations shows that the shear flow imposes a plane symmetry of the wake whatever the parameters of the flow. The trailing vorticity is organized into two anti-symmetrical counter rotating tubes with a sign imposed by the competition of two mechanisms (the Lighthill mechanism and the instability of the wake). Whatever the Reynolds number, the lift coefficient reaches the analytical value obtained in an inviscid, weakly sheared flow corresponding to a lift force oriented in the same direction as that of a spherical bubble. For moderate Reynolds numbers, the direction of the lift force reverses when the bubble aspect ratio is large enough as observed in experiments. This reversal occurs for aspect ratios larger than 2.225 and is found to be directly linked to the sign of the trailing vorticity which is concentrated within two counter-rotating threads which propel the bubble in a direction depending of their sign of rotation. The behavior of the drag does not revel any significant effect induced by the wake structure and follows a quadratic increase with the shear rate. Finally, the torque experienced by the bubble also reverses for the same conditions inducing the reversal of the lift force. By varying the orientation of the bubble in the shear flow, a stable equilibrium position is found corresponding to a weak angle between the small axis of the bubble and the flow direction. (author)
International Nuclear Information System (INIS)
Sengupta, P.R.; Sadat, Khondokar Anowarus; Kundu, Shyamal Kumar
2003-01-01
In this paper, an attempt has been made to study the flow of Rivlin-Ericksen visco-elastic fluid between two inclined parallel planes in presence of gravity and uniform transverse magnetic field. It has been assumed that the lower plane is at rest and the upper plane is moving with a transient velocity in the first case, while in the second case it is moving longitudinally with a periodic velocity. In both cases the fluid velocity and flux of fluid have been obtained by variable separation technique. These results are then deduced for the case of visco-elastic Maxwell fluid taking the fluid to be electrically conducting and placed in presence of a uniform transverse magnetic field. Further, when the magnetic field is absent the corresponding results are obtained by passing to the limit as uniform magnetic field tending to zero. Moreover, the titled problem has also been solved in case of inviscid fluid in both cases of hydromagnetic flow and flow in absence of magnetic field. Thus the present problem is focused to a wide range of flow problems of different types of fluid models. (author)
Concentrated energy addition for active drag reduction in hypersonic flow regime
Ashwin Ganesh, M.; John, Bibin
2018-01-01
Numerical optimization of hypersonic drag reduction technique based on concentrated energy addition is presented in this study. A reduction in wave drag is realized through concentrated energy addition in the hypersonic flowfield upstream of the blunt body. For the exhaustive optimization presented in this study, an in-house high precision inviscid flow solver has been developed. Studies focused on the identification of "optimum energy addition location" have revealed the existence of multiple minimum drag points. The wave drag coefficient is observed to drop from 0.85 to 0.45 when 50 Watts of energy is added to an energy bubble of 1 mm radius located at 74.7 mm upstream of the stagnation point. A direct proportionality has been identified between energy bubble size and wave drag coefficient. Dependence of drag coefficient on the upstream added energy magnitude is also revealed. Of the observed multiple minimum drag points, the energy deposition point (EDP) that offers minimum wave drag just after a sharp drop in drag is proposed as the most optimum energy addition location.
Unsteady 2D potential-flow forces and a thin variable geometry airfoil undergoing arbitrary motion
Energy Technology Data Exchange (ETDEWEB)
Gaunaa, M.
2006-07-15
In this report analytical expressions for the unsteady 2D force distribution on a variable geometry airfoil undergoing arbitrary motion are derived under the assumption of incompressible, irrotational, inviscid flow. The airfoil is represented by its camberline as in classic thin-airfoil theory, and the deflection of the airfoil is given by superposition of chordwise deflection mode shapes. It is shown from the expressions for the forces, that the influence from the shed vorticity in the wake is described by the same time-lag for all chordwise positions on the airfoil. This time-lag term can be approximated using an indicial function approach, making the practical calculation of the aerodynamic response numerically very efficient by use of Duhamel superposition. Furthermore, the indicial function expressions for the time-lag terms are formulated in their equivalent state-space form, allowing for use of the present theory in problems employing the eigenvalue approach, such as stability analysis. The analytical expressions for the forces simplify to all previously known steady and unsteady thin-airfoil solutions. Apart from the obvious applications within active load control/reduction, the current theory can be used for various applications which up to now have been possible only using much more computational costly methods. The propulsive performance of a soft heaving propulsor, and the influence of airfoil camberline elasticity on the flutter limit are two computational examples given in the report that highlight this feature. (au)
Intelligent Flow Control Valve
Kelley, Anthony R (Inventor)
2015-01-01
The present invention is an intelligent flow control valve which may be inserted into the flow coming out of a pipe and activated to provide a method to stop, measure, and meter flow coming from the open or possibly broken pipe. The intelligent flow control valve may be used to stop the flow while repairs are made. Once repairs have been made, the valve may be removed or used as a control valve to meter the amount of flow from inside the pipe. With the addition of instrumentation, the valve may also be used as a variable area flow meter and flow controller programmed based upon flowing conditions. With robotic additions, the valve may be configured to crawl into a desired pipe location, anchor itself, and activate flow control or metering remotely.
Vortex sound radiation in a flow duct with a dipole source and a flexible wall of finite length.
Chiang, Y K; Choy, Y S; Tang, S K
2017-03-01
The noise attenuation of fan-ducted noise at low blade-passage frequency remains a challenge. The present study investigates the noise reduction mechanism of a tensioned membrane housing device that directly controls the sound radiation from the doublet which is enclosed in an infinitely long duct with a point vortex. The time dependent sound radiation mechanism and the vibro-acoustics coupling mechanism of the systems are studied by adopting the potential theory and matched asymptotic expansion technique. The silencing performance of such a passive approach depends on the amplitude and phase of the sound field created by the doublet and the acoustic pressure induced by the membrane oscillation in order to achieve sound cancellation. Results show that the response of membrane vibration is strongly associated with the flow field induced by the grazing uniform flow and also the fluid loading generated by the inviscid vortex. The geometrical property of the cavity and the mechanical properties of the flexible membranes play important roles in controlling the performance of the proposed device.
The effect of small-scale forcing on large-scale structures in two-dimensional flows
Chekhlov, Alexei; Orszag, Steven A.; Sukoriansky, Semion; Galperin, Boris; Staroselsky, Ilya
The effect of small-scale forcing on large-scale structures in β-plane two-dimensional (2D) turbulence is studied using long-term direct numerical simulations (DNS). We find that nonlinear effects remain strong at all times and for all scales and establish an inverse energy cascade that extends to the largest scales available in the system. The large-scale flow develops strong spectral anisotropy: k - {5}/{3} Kolmogorov scaling holds for almost all φ, φ = arctan( {k y}/{k x}) except in the small vicinity of kx = 0, where Rhines's k-5 scaling prevails. Due to the k-5 scaling, the spectral evolution of β-plane turbulence becomes extremely slow which, perhaps, explains why this scaling law has never before been observed in DNS. Simulations with different values of β indicate that the β-effect diminishes at small scales where the flow is nearly isotropic. Thus, for simulations of β-plane turbulence forced at small scales sufficiently removed from the scales where β-effect is strong, large eddy simulation (LES) can be used. A subgrid scale (SGS) parameterization for such LES must account for the small-scale forcing that is not explicitly resolved and correctly accommodate two inviscid conservation laws, viz. energy and enstrophy. This requirement gives rise to a new anisotropic stabilized negative viscosity (SNV) SGS representation which is discussed in the context of LES of isotropic 2D turbulence.
DEFF Research Database (Denmark)
Heiselberg, Per; Nielsen, Peter V.
Air distribution in ventilated rooms is a flow process that can be divided into different elements such as supply air jets, exhaust flows, thermal plumes, boundary layer flows, infiltration and gravity currents. These flow elements are isolated volumes where the air movement is controlled...... by a restricted number of parameters, and the air movement is fairly independent of the general flow in the enclosure. In many practical situations, the most convenient· method is to design the air distribution system using flow element theory....
Dynamic power flow controllers
Energy Technology Data Exchange (ETDEWEB)
Divan, Deepakraj M.; Prasai, Anish
2017-03-07
Dynamic power flow controllers are provided. A dynamic power flow controller may comprise a transformer and a power converter. The power converter is subject to low voltage stresses and not floated at line voltage. In addition, the power converter is rated at a fraction of the total power controlled. A dynamic power flow controller controls both the real and the reactive power flow between two AC sources having the same frequency. A dynamic power flow controller inserts a voltage with controllable magnitude and phase between two AC sources; thereby effecting control of active and reactive power flows between two AC sources.
Introduction to compressible fluid flow
Oosthuizen, Patrick H
2013-01-01
IntroductionThe Equations of Steady One-Dimensional Compressible FlowSome Fundamental Aspects of Compressible FlowOne-Dimensional Isentropic FlowNormal Shock WavesOblique Shock WavesExpansion Waves - Prandtl-Meyer FlowVariable Area FlowsAdiabatic Flow with FrictionFlow with Heat TransferLinearized Analysis of Two-Dimensional Compressible FlowsHypersonic and High-Temperature FlowsHigh-Temperature Gas EffectsLow-Density FlowsBibliographyAppendices
Organocatalysis in continuous flow
Berg, van den S.A.
2016-01-01
Continuous flow chemistry is an enabling technique in organic chemistry. Advantages include extremely fast mixing and heat transfer capabilities as well as rapid screening of reaction conditions. Combining continuous flow chemistry with solid-supported organocatalysis presents challenges that have
International Nuclear Information System (INIS)
Diamond, P.H.; Itoh, S.-I.; Itoh, K.; Hahm, T.S.
2004-10-01
A comprehensive review of zonal flow phenomena in plasmas is presented. While the emphasis is on zonal flows in laboratory plasmas, zonal flows in nature are discussed as well. The review presents the status of theory, numerical simulation and experiments relevant to zonal flows. The emphasis is on developing an integrated understanding of the dynamics of drift wave - zonal flow turbulence by combining detailed studies of the generation of zonal flows by drift waves, the back-interaction of zonal flows on the drift waves, and the various feedback loops by which the system regulates and organizes itself. The implications of zonal flow phenomena for confinement in, and the phenomena of fusion devices are discussed. Special attention is given to the comparison of experiment with theory and to identifying direction for progress in future research. (author)
National Research Council Canada - National Science Library
Shapiro, Howard M
2003-01-01
... ... Conflict: Resolution ... 1.3 Problem Number One: Finding The Cell(s) ... Flow Cytometry: Quick on the Trigger ... The Main Event ... The Pulse Quickens, the Plot Thickens ... 1.4 Flow Cytometry: ...
A peak flow meter is commonly used by a person with asthma to measure the amount of air that can be ... become narrow or blocked due to asthma, peak flow values will drop because the person cannot blow ...
Load flow optimization and optimal power flow
Das, J C
2017-01-01
This book discusses the major aspects of load flow, optimization, optimal load flow, and culminates in modern heuristic optimization techniques and evolutionary programming. In the deregulated environment, the economic provision of electrical power to consumers requires knowledge of maintaining a certain power quality and load flow. Many case studies and practical examples are included to emphasize real-world applications. The problems at the end of each chapter can be solved by hand calculations without having to use computer software. The appendices are devoted to calculations of line and cable constants, and solutions to the problems are included throughout the book.
Hyperspectral imaging flow cytometer
Sinclair, Michael B.; Jones, Howland D. T.
2017-10-25
A hyperspectral imaging flow cytometer can acquire high-resolution hyperspectral images of particles, such as biological cells, flowing through a microfluidic system. The hyperspectral imaging flow cytometer can provide detailed spatial maps of multiple emitting species, cell morphology information, and state of health. An optimized system can image about 20 cells per second. The hyperspectral imaging flow cytometer enables many thousands of cells to be characterized in a single session.
Granular media : flow & agitations
Dijksman, Joshua Albert
2009-01-01
This thesis is about weakly driven granular flows and suspensions. Chapter 1 is an overview of the current knowledge of slow granular flows in so-called split-bottom geometries, which in essence consist of a disk rotating at the bottom of a container. In chapter 2 we study dry granular flows in this
Smiler S, Kingston
2015-01-01
This book is intended for network protocol developers, SDN controller application developers, and academics who would like to understand and develop their own OpenFlow switch or OpenFlow controller in any programming language. With basic understanding of OpenFlow and its components, you will be able to follow the recipes in this book.
Elwenspoek, Michael Curt
1999-01-01
A review is given on sensors fabricated by silicon micromachining technology using the thermal domain for the measurement of fluid flow. Attention is paid especially to performance and geometry of the sensors. Three basic types of thermal flow sensors are discussed: anemometers, calorimetric flow
Chang, Paul K
2014-01-01
Interdisciplinary and Advanced Topics in Science and Engineering, Volume 3: Separation of Flow presents the problem of the separation of fluid flow. This book provides information covering the fields of basic physical processes, analyses, and experiments concerning flow separation.Organized into 12 chapters, this volume begins with an overview of the flow separation on the body surface as discusses in various classical examples. This text then examines the analytical and experimental results of the laminar boundary layer of steady, two-dimensional flows in the subsonic speed range. Other chapt
Abrahams, J R; Hiller, N
1965-01-01
Signal Flow Analysis provides information pertinent to the fundamental aspects of signal flow analysis. This book discusses the basic theory of signal flow graphs and shows their relation to the usual algebraic equations.Organized into seven chapters, this book begins with an overview of properties of a flow graph. This text then demonstrates how flow graphs can be applied to a wide range of electrical circuits that do not involve amplification. Other chapters deal with the parameters as well as circuit applications of transistors. This book discusses as well the variety of circuits using ther
Miles, Robin R [Danville, CA; Benett, William J [Livermore, CA; Coleman, Matthew A [Oakland, CA; Pearson, Francesca S [Livermore, CA; Nasarabadi, Shanavaz L [Livermore, CA
2011-03-08
A lateral flow strip assay apparatus comprising a housing; a lateral flow strip in the housing, the lateral flow strip having a receiving portion; a sample collection unit; and a reagent reservoir. Saliva and/or buccal cells are collected from an individual using the sample collection unit. The sample collection unit is immersed in the reagent reservoir. The tip of the lateral flow strip is immersed in the reservoir and the reagent/sample mixture wicks up into the lateral flow strip to perform the assay.
Annular Flow Distribution test
Energy Technology Data Exchange (ETDEWEB)
Kielpinski, A.L. (ed.) (Westinghouse Savannah River Co., Aiken, SC (United States)); Childerson, M.T.; Knoll, K.E.; Manolescu, M.I.; Reed, M.J. (Babcock and Wilcox Co., Alliance, OH (United States). Research Center)
1990-12-01
This report documents the Babcock and Wilcox (B W) Annular Flow Distribution testing for the Savannah River Laboratory (SRL). The objective of the Annular Flow Distribution Test Program is to characterize the flow distribution between annular coolant channels for the Mark-22 fuel assembly with the bottom fitting insert (BFI) in place. Flow rate measurements for each annular channel were obtained by establishing hydraulic similarity'' between an instrumented fuel assembly with the BFI removed and a reference'' fuel assembly with the BFI installed. Empirical correlations of annular flow rates were generated for a range of boundary conditions.
Annular Flow Distribution test
International Nuclear Information System (INIS)
Kielpinski, A.L.; Childerson, M.T.; Knoll, K.E.; Manolescu, M.I.; Reed, M.J.
1990-12-01
This report documents the Babcock and Wilcox (B ampersand W) Annular Flow Distribution testing for the Savannah River Laboratory (SRL). The objective of the Annular Flow Distribution Test Program is to characterize the flow distribution between annular coolant channels for the Mark-22 fuel assembly with the bottom fitting insert (BFI) in place. Flow rate measurements for each annular channel were obtained by establishing ''hydraulic similarity'' between an instrumented fuel assembly with the BFI removed and a ''reference'' fuel assembly with the BFI installed. Empirical correlations of annular flow rates were generated for a range of boundary conditions
International Nuclear Information System (INIS)
Itoh, K.; Fujisawa, A.; Itoh, S.-I.; Yagi, M.; Nagashima, Y.; Diamond, P.H.; Tynan, G.R.; Hahm, T.S.
2006-01-01
Zonal flows, which means azimuthally symmetric band-like shear flows, are ubiquitous phenomena in nature and the laboratory. It is now widely recognized that zonal flows are a key constituent in virtually all cases and regimes of drift wave turbulence, indeed, so much so that this classic problem is now frequently referred to as ''drift wave-zonal flow turbulence.'' In this review, new viewpoints and unifying concepts are presented, which facilitate understanding of zonal flow physics, via theory, computation and their confrontation with the results of laboratory experiment. Special emphasis is placed on identifying avenues for further progress. (author)
Energy Technology Data Exchange (ETDEWEB)
Boudesocque-Dubois, C.; Gauthier, S.; Clarisse, J.M
2007-07-01
We exhibit and detail the properties of exact self-similar solutions for inviscid compressible ablative flows in slab symmetry with nonlinear heat conduction relevant to inertial confinement fusion (ICF). These solutions have been found after several contributions over the last four decades. We first derived the set of ODEs that governs the self-similar solutions by using the invariance of the Euler's equations with nonlinear heat conduction under the two-parameter Lie group symmetry. A sub-family that leaves the density invariant is detailed since this is the most relevant case for ICF. A physical analysis of these unsteady ablation flows is then provided where the associated dimensionless numbers (Mach, Froude and P let numbers) are calculated. Finally we show that these solutions do not satisfy the constraints of the low Mach number approximation that means that ablation fronts generated within the framework of the present hypotheses (electronic conduction, growing heat flux at the boundary, etc.) cannot be approximated by a steady quasi-incompressible flow as it is often assumed in ICF. Two particular solutions of this family have been recently used for studying stability properties of ablation fronts, since they are representative of the flows that should be reached on the future French Laser MegaJoule. (authors)
46 CFR 154.546 - Excess flow valve: Closing flow.
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Excess flow valve: Closing flow. 154.546 Section 154.546... and Process Piping Systems § 154.546 Excess flow valve: Closing flow. (a) The rated closing flow of vapor or liquid cargo for an excess flow valve must be specially approved by the Commandant (CG-522). (b...
Group flow, complex flow, unit vector flow, and the (2+ϵ)-flow conjecture
DEFF Research Database (Denmark)
Thomassen, Carsten
2014-01-01
If F is a (possibly infinite) subset of an abelian group Γ, then we define f(F,Γ) as the smallest natural number such that every f(F,Γ)-edge-connected (finite) graph G has a flow where all flow values are elements in F. We prove that f(F,Γ) exists if and only if some odd sum of elements in F equals...... some even sum. We discuss various instances of this problem. We prove that every 6-edge-connected graph has a flow whose flow values are the three roots of unity in the complex plane. If the edge-connectivity 6 can be reduced, then it can be reduced to 4, and the 3-flow conjecture follows. We prove...... that every 14-edge-connected graph has a flow whose flow values are the five roots of unity in the complex plane. Any such flow is balanced modulo 5. So, if the edge-connectivity 14 can be reduced to 9, then the 5-flow conjecture follows, as observed by F. Jaeger. We use vector flow to prove that, for each...
Generalized Kutta–Joukowski theorem for multi-vortex and multi-airfoil flow (a lumped vortex model
Directory of Open Access Journals (Sweden)
Bai Chenyuan
2014-02-01
Full Text Available For purpose of easy identification of the role of free vortices on the lift and drag and for purpose of fast or engineering evaluation of forces for each individual body, we will extend in this paper the Kutta–Joukowski (KJ theorem to the case of inviscid flow with multiple free vortices and multiple airfoils. The major simplification used in this paper is that each airfoil is represented by a lumped vortex, which may hold true when the distances between vortices and bodies are large enough. It is found that the Kutta–Joukowski theorem still holds provided that the local freestream velocity and the circulation of the bound vortex are modified by the induced velocity due to the outside vortices and airfoils. We will demonstrate how to use the present result to identify the role of vortices on the forces according to their position, strength and rotation direction. Moreover, we will apply the present results to a two-cylinder example of Crowdy and the Wagner example to demonstrate how to perform fast force approximation for multi-body and multi-vortex problems. The lumped vortex assumption has the advantage of giving such kinds of approximate results which are very easy to use. The lack of accuracy for such a fast evaluation will be compensated by a rigorous extension, with the lumped vortex assumption removed and with vortex production included, in a forthcoming paper.
DEFF Research Database (Denmark)
Jørgensen, Ivan Harald Holger; Bogason, Gudmundur; Bruun, Erik
1995-01-01
This paper proposes a new way to estimate the flow in a micromechanical flow channel. A neural network is used to estimate the delay of random temperature fluctuations induced in a fluid. The design and implementation of a hardware efficient neural flow estimator is described. The system...... is implemented using switched-current technique and is capable of estimating flow in the μl/s range. The neural estimator is built around a multiplierless neural network, containing 96 synaptic weights which are updated using the LMS1-algorithm. An experimental chip has been designed that operates at 5 V...
Directory of Open Access Journals (Sweden)
Hric Vladimír
2015-01-01
Full Text Available We present an engineering approach to mathematical modeling and numerical solution of 2D inviscid transonic flow of wet steam in a steam turbine cascade channel of penultimate stage at rotor tip section in full Eulerian framework. Our flow model consists of the Euler system for the mixture (dry steam + homogeneously dispersed water droplets and transport equations for moments of droplet number distribution function known as method of moments. Thermodynamic properties of vapor steam are provided by set of IAPWS equations. For equation of state for vapor phase valid both in superheated and wet (meta-stable region we adopted recently developed equation in CFD formulation for low pressures provi1ded by Hrubý et al. [9], [8], [10]. For extraction of vapor parameters from the mixture ones we implemented simple relations in polynomial form describing thermodynamic properties of saturated liquid state. Nucleation model is resorting to modified classical nucleation theory. Linear droplet growth model is implemented for calculation of liquid sources. Numerical method is simple: cell-centered finite volume approach, 1st-order AUSM+ scheme for spatial derivatives, symmetrical fractional step method for separation of convection and condensation part, explicit 2-stage 2nd-order Runge-Kutta method for time integration. Geometry of blade profile and experimental results are provided by Bakhtar’s work [22], [23]. Results were obtained for one subsonic inlet/subsonic outlet regime and gave quite reasonable accordance with experiment.
Flow visualization using bubbles
International Nuclear Information System (INIS)
Henry, J.P.
1974-01-01
Soap bubbles were used for visualizing flows. The tests effected allowed some characteristics of flows around models in blow tunnels to be precised at mean velocities V 0 5 . The velocity of a bubble is measured by chronophotography, the bulk envelope of the trajectories is also registered [fr
Airport Network Flow Simulator
1978-10-01
The Airport Network Flow Simulator is a FORTRAN IV simulation of the flow of air traffic in the nation's 600 commercial airports. It calculates for any group of selected airports: (a) the landing and take-off (Type A) delays; and (b) the gate departu...
National Research Council Canada - National Science Library
Jaroszeski, Mark J; Heller, Richard
1998-01-01
... are individually analyzed, and it is typical for flow cytometers to quantitatively process thousands of individual particles in a matter of seconds. This a powerful analytic feat particularly if one relates it to the time required to examine several thousand individual cells using a microscope. This leaves little doubt regarding why the field of flow cytometry has...
2015-09-30
Flow around steep topography T. M. Shaun Johnston Scripps Institution of Oceanography University of California, San Diego 9500 Gilman Drive, M...tall, steep, submarine topography and islands. During the Flow Encountering Abrupt Topography (FLEAT) DRI, investigators will determine: • Whether...estimates from making accurate statistical/deterministic predictions at km resolution around submarine topography and islands? How can we
Casas, J.; Liu, Chang; Krijnen, Gijsbertus J.M.
2012-01-01
Biomimetic flow sensors are biologically inspired devices that measure the speed and direction of fluids. This survey starts by describing the role and functioning of airflow-sensing hairs in arthropods and in fishes, carries on with the biomimetic MEMS implementations, both for air and water flow
DEFF Research Database (Denmark)
Kristensen, René
2006-01-01
Artiklen handler om pædagogisk perspektivering af flow i forhold til anerkendelse og kreativitet. Procedural hukommelsesdannelse inddrages i forbindelse med flowforståelsen......Artiklen handler om pædagogisk perspektivering af flow i forhold til anerkendelse og kreativitet. Procedural hukommelsesdannelse inddrages i forbindelse med flowforståelsen...
DEFF Research Database (Denmark)
Andersen, Frans Ørsted; Hanssen, Nina
Bogen afspejler et eksplorativt dansk-norsk forskningsprojekt med fokus på hverdagslivets psykiske sider, herunder størrelser som stress og flow.......Bogen afspejler et eksplorativt dansk-norsk forskningsprojekt med fokus på hverdagslivets psykiske sider, herunder størrelser som stress og flow....
Delays of Interconnected Flows
Sorger, U.; Suchanecki, Z.
2011-07-01
A rigorous approach to flows of particles in networks is presented. Under the assumption of independence of the transversal flows the asymptotic distributions of inter-delay times between particles are shown to be log-normal. In the case of dependent transversal traffic the ARCH and GARCH time series models, as well as martingale approach, have been applied.
Physics suggests that the interplay of momentum, continuity, and geometry in outward radial flow must produce density and concomitant pressure reductions. In other words, this flow is intrinsically auto-expansive. It has been proposed that this process is the key to understanding...
Optimised Renormalisation Group Flows
Litim, Daniel F
2001-01-01
Exact renormalisation group (ERG) flows interpolate between a microscopic or classical theory and the corresponding macroscopic or quantum effective theory. For most problems of physical interest, the efficiency of the ERG is constrained due to unavoidable approximations. Approximate solutions of ERG flows depend spuriously on the regularisation scheme which is determined by a regulator function. This is similar to the spurious dependence on the ultraviolet regularisation known from perturbative QCD. Providing a good control over approximated ERG flows is at the root for reliable physical predictions. We explain why the convergence of approximate solutions towards the physical theory is optimised by appropriate choices of the regulator. We study specific optimised regulators for bosonic and fermionic fields and compare the optimised ERG flows with generic ones. This is done up to second order in the derivative expansion at both vanishing and non-vanishing temperature. An optimised flow for a ``proper-time ren...
DEFF Research Database (Denmark)
Wohlgemuth, Ole
2016-01-01
"Begrebet flow, som det er formuleret af den ungarskefødte, amerikanske psykolog Mihaly Csikszentmihalyi", "beskriver en koncentreret tilstand af opslugthed i forbindelse med en oplevelse eller aktivitet. Flow betragtes som den tilstand, hvor læring foregår mest meningsfuldt, intensivt og...... grundlæggende; flow er endog blevet beskrevet som "de positive følelser kroppen belønner os med, når vi lærer noget vigtigt". Flow har sit udspring i positiv psykologi, som er et begreb indenfor den psykologiske forskning, der fokuserer på spørgsmålet om, hvad skal der til for at mennesker og samfund bedre kan...... trives og blomstre frem for et fokus på sygdomsfremkaldende og negative sammenhænge." ... "flow er en væsentlig tilstand at være fokuseret på og arbejde mod i forbindelse med formidling af naturen."...
Energy Technology Data Exchange (ETDEWEB)
Larsen, Marit; Munaweera, Sampath
2010-07-01
Vega is a gas condensate field located at the west coast of Norway and developed as a tie-in to the Gjoea platform. Operator is Statoil, production startup is estimated to the end of 2010. Flow assurance challenges are high reservoir pressure and temperature, hydrate and wax control, liquid accumulation and monitoring the well/template production rates. The Vega Flow Assurance System (FAS) is a software that supports monitoring and operation of the field. The FAS is based FlowManagerTM designed for real time systems. This is a flexible tool with its own steady state multiphase- and flow assurance models. Due to the long flowlines lines and the dynamic behavior, the multiphase flow simulator OLGA is also integrated in the system. Vega FAS will be used as: - An online monitoring tool - An offline what-if simulation and validation tool - An advisory control system for well production allocation. (Author)
Environmental stratified flows
Armenio, Vincenzo
2006-01-01
The volume covers the theory of stratified flows, from basic concepts to recent developments in the area of environmental fluid mechanics. The state of art of numerical techniques suited for stratified flows is given. Results of very recent researches in the areas of environmental stratified flows are discussed with details. The topics are treated in four separate chapters. The volume gives a unified view of stratified turbulent flows, from small-scale mixing, to large-scale environmental phenomena, also including detailed discussion on interaction between turbulence and internal gravity waves. The book will serve as an important review tool for all the scientists involved in the investigation of small scale as well as geophysical stratified flows.
Flow regime analysis of non-Newtonian duct flows
Speetjens, Michel; Rudman, Murray; Metcalfe, Guy
2006-01-01
Reoriented duct flows of generalized Newtonian fluids are an idealization of non-Newtonian fluid flow in industrial in-line mixers. Based on scaling analysis and computation we find that non-Newtonian duct flows have several limit behaviors, in the sense that such flows can become (nearly) independent of one or more of the rheological and dynamical control parameters, simplifying the general flow and mixing problem. These limit flows give several levels of modeling complexity to the full problem of non-Newtonian duct flow. We describe the sets of simplified flow models and their corresponding regions of validity. This flow-model decomposition captures the essential rheological and dynamical characteristics of the reoriented duct flows and enables a more efficient and systematic study and design of flow and mixing of non-Newtonian fluids in ducts. Key aspects of the flow-model decomposition are demonstrated via a specific, but representative, duct flow.
Venditti, Jeremy G; Rennie, Colin D; Bomhof, James; Bradley, Ryan W; Little, Malcolm; Church, Michael
2014-09-25
Bedrock erosion in rivers sets the pace of landscape evolution, influences the evolution of orogens and determines the size, shape and relief of mountains. A variety of models link fluid flow and sediment transport processes to bedrock incision in canyons. The model components that represent sediment transport processes are increasingly well developed. In contrast, the model components being used to represent fluid flow are largely untested because there are no observations of the flow structure in bedrock canyons. Here we present a 524-kilometre, continuous centreline, acoustic Doppler current profiler survey of the Fraser Canyon in western Canada, which includes 42 individual bedrock canyons. Our observations of three-dimensional flow structure reveal that, as water enters the canyons, a high-velocity core follows the bed surface, causing a velocity inversion (high velocities near the bed and low velocities at the surface). The plunging water then upwells along the canyon walls, resulting in counter-rotating, along-stream coherent flow structures that diverge near the bed. The resulting flow structure promotes deep scour in the bedrock channel floor and undercutting of the canyon walls. This provides a mechanism for channel widening and ensures that the base of the walls is swept clear of the debris that is often deposited there, keeping the walls nearly vertical. These observations reveal that the flow structure in bedrock canyons is more complex than assumed in the models presently used. Fluid flow models that capture the essence of the three-dimensional flow field, using simple phenomenological rules that are computationally tractable, are required to capture the dynamic coupling between flow, bedrock erosion and solid-Earth dynamics.
High-Fidelity Numerical Modeling of Compressible Flow
2015-11-01
shock-capturing modified Steger -Warming flux vector splitting scheme. The viscous fluxes were evaluated using a second-order accurate central...Stokes equations on unstructured grids, and was developed at the University of Minnesota.22 Inviscid fluxes are evaluated using the modified Steger ...Warming flux vector splitting scheme developed by MacCormack and Candler.23 This modified Steger -Warming method utilizes a pressure-dependent weighting
Numerical Modeling of Compressible Flow and Its Control
2014-03-01
equations on unstructured grids, developed at the University of Minnesota.25 The modified Steger -Warming flux vector splitting scheme of MacCormack and...Candler26 is used to evaluate the inviscid fluxes. This modified Steger -Warming method uses a pressure-dependent weighting function to D ow nl oa de d...smoothly from a low-dissipation method in regions of low gradients to the original Steger –Warming scheme when a large-pressure gradient is detected across
Bruno, B. C.; Taylor, G. J.; Rowland, S. K.; Lucey, P. G.; Self, S.
1992-01-01
Results are presented of a preliminary investigation of the fractal nature of the plan-view shapes of lava flows in Hawaii (based on field measurements and aerial photographs), as well as in Idaho and the Galapagos Islands (using aerial photographs only). The shapes of the lava flow margins are found to be fractals: lava flow shape is scale-invariant. This observation suggests that nonlinear forces are operating in them because nonlinear systems frequently produce fractals. A'a and pahoehoe flows can be distinguished by their fractal dimensions (D). The majority of the a'a flows measured have D between 1.05 and 1.09, whereas the pahoehoe flows generally have higher D (1.14-1.23). The analysis is extended to other planetary bodies by measuring flows from orbital images of Venus, Mars, and the moon. All are fractal and have D consistent with the range of terrestrial a'a and have D consistent with the range of terrestrial a'a and pahoehoe values.
International Nuclear Information System (INIS)
Hazi, G.; Mayer, G.
2005-01-01
For power upgrading VVER-440 reactors we need to know exactly how the temperature measured by the thermocouples is related to the average outlet temperature of the fuel assemblies. Accordingly, detailed knowledge on mixing process in the rod bundles and in the fuel assembly head have great importance. Here we study the hydrodynamics of rod bundles based on the results of direct numerical and large eddy simulation of flows in subchannels. It is shown that secondary flow and flow pulsation phenomena can be observed using both methodologies. Some consequences of these observations are briefly discussed. (author)
International Nuclear Information System (INIS)
Hanratty, T.J.; Woods, B.D.
1995-01-01
The initiation of slug flow in a horizontal pipe can be predicted either by considering the stability of a slug or by considering the stability of a stratified flow. Measurements of the shedding rate of slugs are used to define necessary conditions for the existence of a slug. Recent results show that slugs develop from an unstable stratified flow through the evolution of small wavelength waves into large wavelength waves that have the possibility of growing to form a slug. The mechanism appears to be quite different for fluids with viscosities close to water than for fluids with large viscosities (20 centipoise)
Magnetic vortex filament flows
International Nuclear Information System (INIS)
Barros, Manuel; Cabrerizo, Jose L.; Fernandez, Manuel; Romero, Alfonso
2007-01-01
We exhibit a variational approach to study the magnetic flow associated with a Killing magnetic field in dimension 3. In this context, the solutions of the Lorentz force equation are viewed as Kirchhoff elastic rods and conversely. This provides an amazing connection between two apparently unrelated physical models and, in particular, it ties the classical elastic theory with the Hall effect. Then, these magnetic flows can be regarded as vortex filament flows within the localized induction approximation. The Hasimoto transformation can be used to see the magnetic trajectories as solutions of the cubic nonlinear Schroedinger equation showing the solitonic nature of those
Directory of Open Access Journals (Sweden)
Pavlović Miloš
2013-01-01
Full Text Available A cash flow is "bloodstream" of business and without constant cash flow a company would not be able to function. The cash flow statement is statutory financial report that provides information to the interested parties on cash inflows and outflows from operating, investing and financing activities during the accounting period. This paper will discuss the origin and significance of the cash slow statement; in addition, we will define the main categories of this statement and present the methodology of its composition in accordance with IAS 7.
Refrigeration. Two-Phase Flow. Flow Regimes and Pressure Drop
DEFF Research Database (Denmark)
Knudsen, Hans-Jørgen Høgaard
2002-01-01
The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature.......The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature....
Energy Technology Data Exchange (ETDEWEB)
none,
2012-05-01
This report documents findings from a workshop on the impacts of complex wind flows in and out of wind turbine environments, the research needs, and the challenges of meteorological and engineering modeling at regional, wind plant, and wind turbine scales.
DEFF Research Database (Denmark)
Nielsen, Jens Kromann; Rasmussen, Henrik K.
2008-01-01
Afilament stretching rheometer (FSR) was used for measuring the start-up of uni-axial elongational flow followed by reversed bi-axial flow, both with a constant elongational rate. A narrow molecular mass distribution linear polystyrene with a molecular weight of 145 kg / mole wis subjected...... to the start-up of elongation for three Hencky strain units and subsequently the reversed flow. The integral molecular stress function formulation within the 'interchain pressure' concept agrees with the experiments. In the experiments the Hencky strain at which the str~ss becomes zero (the recovery strain......) in the reversed flow has been identified. The recovery strain is found to increase with elongational rate, and has a maximum value of approximately 1.45. The Doi Edwards model using any stretch evolution equation is not able to predict the correct level of the recovery strain....
2016-11-01
Computer and video gamers of a certain vintage will have fond memories of Lemmings, a game in which players must shepherd pixelated, suicidal rodents around a series of obstacles to reach safety. At first glance, Ice Flows is strikingly similar.
National Research Council Canada - National Science Library
Drikakis, D; Geurts, Bernard
2002-01-01
... discretization 3 A test-case: turbulent channel flow 4 Conclusions 75 75 82 93 98 4 Analysis and control of errors in the numerical simulation of turbulence Sandip Ghosal 1 Introduction 2 Source...
Federal Laboratory Consortium — The primary goal of the Flow Cytometry Section is to provide the services of state-of-the-art multi-parameter cellular analysis and cell sorting for researchers and...
Flow cytometry bioinformatics.
Directory of Open Access Journals (Sweden)
Kieran O'Neill
Full Text Available Flow cytometry bioinformatics is the application of bioinformatics to flow cytometry data, which involves storing, retrieving, organizing, and analyzing flow cytometry data using extensive computational resources and tools. Flow cytometry bioinformatics requires extensive use of and contributes to the development of techniques from computational statistics and machine learning. Flow cytometry and related methods allow the quantification of multiple independent biomarkers on large numbers of single cells. The rapid growth in the multidimensionality and throughput of flow cytometry data, particularly in the 2000s, has led to the creation of a variety of computational analysis methods, data standards, and public databases for the sharing of results. Computational methods exist to assist in the preprocessing of flow cytometry data, identifying cell populations within it, matching those cell populations across samples, and performing diagnosis and discovery using the results of previous steps. For preprocessing, this includes compensating for spectral overlap, transforming data onto scales conducive to visualization and analysis, assessing data for quality, and normalizing data across samples and experiments. For population identification, tools are available to aid traditional manual identification of populations in two-dimensional scatter plots (gating, to use dimensionality reduction to aid gating, and to find populations automatically in higher dimensional space in a variety of ways. It is also possible to characterize data in more comprehensive ways, such as the density-guided binary space partitioning technique known as probability binning, or by combinatorial gating. Finally, diagnosis using flow cytometry data can be aided by supervised learning techniques, and discovery of new cell types of biological importance by high-throughput statistical methods, as part of pipelines incorporating all of the aforementioned methods. Open standards, data
International Nuclear Information System (INIS)
2005-01-01
RCA is an inter-governmental agreement among IAEA Member States in Asia and the Pacific. The Member States are Australia, Bangladesh, China, India, Indonesia, Japan, Korea, Malaysia, Mongolia, Myanmar, New Zealand, Pakistan, The Philippines, Singapore, Sri Lanka, Thailand and Viet Nam. The RCA Thematic Sectors are Agriculture, Human Health, Industry, Environment, Energy, Research Reactors, Radiation Safety, Electronic Networking and Outreach. This PowerPoint presentation gives an overview about the RCA projects, the information flow mechanism and the information flow programme
Böser, W.; Belfroid, S.P.C.
2013-01-01
Generally large scale carbon capture projects require pipeline systems for the transporting of the CO2 from its point of capture to the storage site. The article will give information on the proposed operational management system. This has to work for all process situations, ranging from steady flow at varying injection conditions and flow rates, to start-up and shutdown procedures and also for emergency shutdown at the platform. In all these operational situations the phase behaviour of CO2 ...
Electrochemical flow capacitors
Gogotsi, Yury; Presser, Volker; Kumbur, Emin Caglan
2015-10-27
The present invention generally relates to devices for energy storage technologies, and more particularly to electrochemical flow capacitor systems and applications. In some aspects, these flow capacitors have at least one electrode comprising a non-stationary solid or semi-solid composition comprising supercapacitive particles and an electrolytic solvent in electrical communication with at least one current collector, and energy is stored and/or released by charging and/or discharging the electrode(s).
International Nuclear Information System (INIS)
Sargsyan, R.A.
2011-01-01
A cost-effective hydropower system called here Flow Energy Converter was developed, patented, manufactured and tested for water pumping, electricity generation and other purposes especially useful for the rural communities. The system consists of water-driven turbine with plane-surface blades, power transmission means and pump and/or generator. Working sample of the Flow Energy Converter was designed and manufactured at the Institute of Radio Physics and Electronics
Flow with Negative Differential Viscosity
川口, 明彦; Akihiko, KAWAGUCHI; 京大人環; Graduate School of Human and Enviromental Studies, Kyoto University
2000-01-01
Only a monotonous flow appears to the movement of the incompressible flow body in a porous medium under a simple condition according to Darcy's law. However, the character of the flow changes greatly if we think about the model by which the temperature dependency in the coefficient of viscosity is considered. Becoming of the inclination of pressure deifference-flow velocity specific characteristics nagative if we think about the one-dimensnional flow under a suitable condition, that is, "Flow...
Directory of Open Access Journals (Sweden)
Edris Yousefi Rad
2017-08-01
Full Text Available In the present research, considering the importance of desirable steam turbine design, improvement of numerical modeling of steam two-phase flows in convergent and divergent channels and the blades of transonic steam turbines has been targeted. The first novelty of this research is the innovative use of combined Convective Upstream Pressure Splitting (CUSP and scalar methods to update the flow properties at each calculation point. In other words, each property (density, temperature, pressure and velocity at each calculation point can be computed from either the CUSP or scalar method, depending on the least deviation criterion. For this reason this innovative method is named “hybrid method”. The next novelty of this research is the use of an inverse method alongside the proposed hybrid method to find the amount of the important parameter z in the CUSP method, which is herein referred to as “CUSP’s convergence parameter”. Using a relatively simple computational grid, firstly, five cases with similar conditions to those of the main cases under study in this research with available experimental data were used to obtain the value of z by the Levenberg-Marquardt inverse method. With this innovation, first, an optimum value of z = 2.667 was obtained using the inverse method and then directly used for the main cases considered in the research. Given that the aim is to investigate the two-dimensional, steady state, inviscid and adiabatic modeling of steam nucleating flows in three different nozzle and turbine blade geometries, flow simulation was performed using a relatively simple mesh and the innovative proposed hybrid method (scalar + CUSP, with the desired value of z = 2.667 . A comparison between the results of the hybrid modeling of the three main cases with experimental data showed a very good agreement, even within shock zones, including the condensation shock region, revealing the efficiency of this numerical modeling method innovation
Energy Technology Data Exchange (ETDEWEB)
Roediger, E. [Hamburger Sternwarte, Universität Hamburg, Gojensbergsweg 112, D-21029 Hamburg (Germany); Kraft, R. P.; Nulsen, P. E. J.; Forman, W. R.; Machacek, M.; Randall, S.; Jones, C. [Harvard/Smithsonian Center for Astrophysics, 60 Garden Street MS-4, Cambridge, MA 02138 (United States); Churazov, E. [MPI für Astrophysik, Karl-Schwarzschild-Str. 1, Garching, D-85741 (Germany); Kokotanekova, R., E-mail: eroediger@hs.uni-hamburg.de [AstroMundus Master Programme, University of Innsbruck, Technikerstr. 25/8, 6020 Innsbruck (Austria)
2015-06-10
Elliptical cluster galaxies are progressively stripped of their atmospheres due to their motion through the intracluster medium (ICM). Deep X-ray observations reveal the fine-structure of the galaxy’s remnant atmosphere and its gas tail and wake. This fine-structure depends on dynamic conditions (galaxy potential, initial gas contents, orbit through the host cluster), orbital stage (early infall, pre-/post-pericenter passage), and ICM plasma properties (thermal conductivity, viscosity, magnetic field structure). We aim to disentangle dynamic and plasma effects in order to use stripped ellipticals as probes of ICM plasma properties. This first paper of a series investigates the hydrodynamics of progressive gas stripping by means of inviscid hydrodynamical simulations. We distinguish a long-lasting initial relaxation phase and a quasi-steady stripping phase. During quasi-steady stripping, the ICM flow around the remnant atmosphere resembles the flow around solid bodies, including a “deadwater” region in the near wake. Gas is stripped from the remnant atmosphere predominantly at its sides via Kelvin–Helmholtz instabilities. The downstream atmosphere is largely shielded from the ICM wind and thus shaped into a tail. Observationally, both this “remnant tail” and the stripped gas in the wake can appear as a “tail”, but only in the wake can galactic gas mix with the ambient ICM. While the qualitative results are generic, the simulations presented here are tailored to the Virgo elliptical galaxy M89 (NGC 4552) for the most direct comparison to observations. Papers II and III of this series describe the effect of viscosity and compare to Chandra and XMM-Newton observations, respectively.
Planetary heat flow measurements.
Hagermann, Axel
2005-12-15
The year 2005 marks the 35th anniversary of the Apollo 13 mission, probably the most successful failure in the history of manned spaceflight. Naturally, Apollo 13's scientific payload is far less known than the spectacular accident and subsequent rescue of its crew. Among other instruments, it carried the first instrument designed to measure the flux of heat on a planetary body other than Earth. The year 2005 also should have marked the launch of the Japanese LUNAR-A mission, and ESA's Rosetta mission is slowly approaching comet Churyumov-Gerasimenko. Both missions carry penetrators to study the heat flow from their target bodies. What is so interesting about planetary heat flow? What can we learn from it and how do we measure it?Not only the Sun, but all planets in the Solar System are essentially heat engines. Various heat sources or heat reservoirs drive intrinsic and surface processes, causing 'dead balls of rock, ice or gas' to evolve dynamically over time, driving convection that powers tectonic processes and spawns magnetic fields. The heat flow constrains models of the thermal evolution of a planet and also its composition because it provides an upper limit for the bulk abundance of radioactive elements. On Earth, the global variation of heat flow also reflects the tectonic activity: heat flow increases towards the young ocean ridges, whereas it is rather low on the old continental shields. It is not surprising that surface heat flow measurements, or even estimates, where performed, contributed greatly to our understanding of what happens inside the planets. In this article, I will review the results and the methods used in past heat flow measurements and speculate on the targets and design of future experiments.
Oscillatory flow chemical reactors
Directory of Open Access Journals (Sweden)
Slavnić Danijela S.
2014-01-01
Full Text Available Global market competition, increase in energy and other production costs, demands for high quality products and reduction of waste are forcing pharmaceutical, fine chemicals and biochemical industries, to search for radical solutions. One of the most effective ways to improve the overall production (cost reduction and better control of reactions is a transition from batch to continuous processes. However, the reactions of interests for the mentioned industry sectors are often slow, thus continuous tubular reactors would be impractically long for flow regimes which provide sufficient heat and mass transfer and narrow residence time distribution. The oscillatory flow reactors (OFR are newer type of tube reactors which can offer solution by providing continuous operation with approximately plug flow pattern, low shear stress rates and enhanced mass and heat transfer. These benefits are the result of very good mixing in OFR achieved by vortex generation. OFR consists of cylindrical tube containing equally spaced orifice baffles. Fluid oscillations are superimposed on a net (laminar flow. Eddies are generated when oscillating fluid collides with baffles and passes through orifices. Generation and propagation of vortices create uniform mixing in each reactor cavity (between baffles, providing an overall flow pattern which is close to plug flow. Oscillations can be created by direct action of a piston or a diaphragm on fluid (or alternatively on baffles. This article provides an overview of oscillatory flow reactor technology, its operating principles and basic design and scale - up characteristics. Further, the article reviews the key research findings in heat and mass transfer, shear stress, residence time distribution in OFR, presenting their advantages over the conventional reactors. Finally, relevant process intensification examples from pharmaceutical, polymer and biofuels industries are presented.
Flow: Statistics, visualization and informatics for flow cytometry
Directory of Open Access Journals (Sweden)
Kepler Thomas B
2008-06-01
Full Text Available Abstract Flow is an open source software application for clinical and experimental researchers to perform exploratory data analysis, clustering and annotation of flow cytometric data. Flow is an extensible system that offers the ease of use commonly found in commercial flow cytometry software packages and the statistical power of academic packages like the R BioConductor project.
Load flow analysis using decoupled fuzzy load flow under critical ...
African Journals Online (AJOL)
user
The conventional load flow methods like Newton-Raphson load flow (NRLF), Fast Decoupled load flow (FDLF) provide poor performance under critical conditions such as high R/X ratio, heavily loading condition etc. Exploiting the decoupling properties of power system, reliable fuzzy load flow is developed to overcome the ...
Tomographic multiphase flow measurement
International Nuclear Information System (INIS)
Sætre, C.; Johansen, G.A.; Tjugum, S.A.
2012-01-01
Measurement of multiphase flow of gas, oil and water is not at all trivial and in spite of considerable achievements over the past two decades, important challenges remain (). These are related to reducing measurement uncertainties arising from variations in the flow regime, improving long term stability and developing new means for calibration, adjustment and verification of the multiphase flow meters. This work focuses on the first two issues using multi gamma beam (MGB) measurements for identification of the type of flow regime. Further gamma ray tomographic measurements are used for reference of the gas/liquid distribution. For the MGB method one Am-241 source with principal emission at 59.5 keV is used because this relatively low energy enables efficient collimation and thereby shaping of the beams, as well as compact detectors. One detector is placed diametrically opposite the source whereas the second is positioned to the side so that this beam is close to the pipe wall. The principle is then straight forward to compare the measured intensities of these detectors and through that identify the flow pattern, i.e. the instantaneous cross-sectional gas-liquid distribution. The measurement setup also includes Compton scattering measurements, which can provide information about the changes in the water salinity for flow segments with high water liquid ratio and low gas fractions. By measuring the transmitted intensity in short time slots (<100ms), rapid regime variations are revealed. From this we can select the time sections suitable for salinity measurements. Since the salinity variations change at the time scale of hours, a running average can be performed to increase the accuracy of the measurements. Recent results of this work will be presented here. - Highlights: ► Multiphase flow gas-fraction and flow regime measurements by multi gamma ray beams. ► High-speed gamma ray tomograph as reference for the flow pattern and gas fraction. ► Dual modality
Radiotracer techniques for measuring fluid flow and calibrating flow meters
International Nuclear Information System (INIS)
Cooper, E.L.
1987-08-01
Radiotracer techniques can be used to measure accurately both gas and liquid flow rates under operating conditions in a wide range of flow systems. They are ideally suited for calibrating flow meters as well as for measuring unmetered flows in industrial plants. Applications of these techniques range from measuring the flows of fuels and process fluids for energy and mass balance studies to measuring the flows of liquid and airborne effluents for pollution control. This report describes the various radiotracer techniques which can be used to measure fluid flows. The range of application and inherent accuracy of each technique is discussed
Upscaling of Forchheimer flows
Aulisa, Eugenio
2014-08-01
In this work we propose upscaling method for nonlinear Forchheimer flow in heterogeneous porous media. The generalized Forchheimer law is considered for incompressible and slightly-compressible single-phase flows. We use recently developed analytical results (Aulisa et al., 2009) [1] and formulate the resulting system in terms of a degenerate nonlinear flow equation for the pressure with the nonlinearity depending on the pressure gradient. The coarse scale parameters for the steady state problem are determined so that the volumetric average of velocity of the flow in the domain on fine scale and on coarse scale are close. A flow-based coarsening approach is used, where the equivalent permeability tensor is first evaluated following streamline methods for linear cases, and modified in order to take into account the nonlinear effects. Compared to previous works (Garibotti and Peszynska, 2009) [2], (Durlofsky and Karimi-Fard) [3], this approach can be combined with rigorous mathematical upscaling theory for monotone operators, (Efendiev et al., 2004) [4], using our recent theoretical results (Aulisa et al., 2009) [1]. The developed upscaling algorithm for nonlinear steady state problems is effectively used for variety of heterogeneities in the domain of computation. Direct numerical computations for average velocity and productivity index justify the usage of the coarse scale parameters obtained for the special steady state case in the fully transient problem. For nonlinear case analytical upscaling formulas in stratified domain are obtained. Numerical results were compared to these analytical formulas and proved to be highly accurate. © 2014.
Energy Technology Data Exchange (ETDEWEB)
Chambers, K.T.; Radke, C.J.
1990-10-01
Foams are often utilized as part of enhanced oil recovery techniques. This report presents the results of a micromodel foam flow study. Micromodels are valuable tools in uncovering capillary phenomena responsible for lamellae generation and coalescence during foam flow in porous media. Among the mechanisms observed are snap-off, weeping-flow breakup, and lamella division and leave behind. Coalescence mechanisms include dynamic capillary-pressure-induced lamella drainage and gas diffusion. These phenomena are sensitive to the mode of injection, the local capillary environment, and the geometry of the pore structure. An important consideration in presenting a tractable model of foam flow behavior is the ability to identify the pore-level mechanisms having the greatest impact on foam texture. The predominant mechanisms will vary depending upon the application for foam as an enhanced oil recovery (EOR) fluid. Both simultaneous gas and surfactant injection and surfactant alternating with gas injection (SAG) have been used to create foam for mobility control in EOR projects. The model developed is based on simultaneous gas and surfactant injection during steady-state conditions into a Berea sandstone core. The lamellae generation and coalescence mechanisms included in this model are snap-off, lamella division, and dynamic capillary-pressure-induced lamella drainage. This simplified steady-state model serves as a foundation for developing more complete rate expressions and for extending the population balance to handle transient foam flow behavior. 70 refs., 30 figs.
Turbine flow meter response in two-phase flows
International Nuclear Information System (INIS)
Shim, W.J.; Dougherty, T.J.; Cheh, H.Y.
1996-01-01
The purpose of this paper is to suggest a simple method of calibrating turbine flow meters to measure the flow rates of each phase in a two-phase flow. The response of two 50.8 mm (2 inch) turbine flow meters to air-water, two-phase mixtures flowing vertically in a 57 mm I.D. (2.25 inch) polycarbonate tube has been investigated for both upflow and downflow. The flow meters were connected in series with an intervening valve to provide an adjustable pressure difference between them. Void fractions were measured by two gamma densitometers, one upstream of the flow meters and the other downstream. The output signal of the turbine flow meters was found to depend only on the actual volumetric flow rate of the gas, F G , and liquid, F L , at the location of the flow meter
Designing reliability information flows
International Nuclear Information System (INIS)
Petkova, Valia T.; Lu Yuan; Ion, Roxana A.; Sander, Peter C.
2005-01-01
It is well-known [Reliab. Eng. Syst. Saf. 75 (2002) 295] that in modern development processes it is essential to have an information flow structure that facilitates fast feedback from product users (customers) to departments at the front end, in particular development and production. As information is only relevant if it is used when taking decisions, this paper presents a guideline for building field feedback information flows that facilitate the decision taking during the product creation and realisation process. The guideline takes into consideration that the type of decisions depends on the span-of-control, therefore following Parsons [Structure and Process in Modern Societies (1990)] the span-of-control is subdivided into the following three levels: strategic, tactic, and executive. The guideline is illustrated with a case in which it is used for analysing the quality of existing field feedback flows
Galdi, Giovanni; Nečasová, Šárka
2017-01-01
This book aims to face particles in flows from many different, but essentially interconnected sides and points of view. Thus the selection of authors and topics represented in the chapters, ranges from deep mathematical analysis of the associated models, through the techniques of their numerical solution, towards real applications and physical implications. The scope and structure of the book as well as the selection of authors was motivated by the very successful summer course and workshop "Particles in Flows'' that was held in Prague in the August of 2014. This meeting revealed the need for a book dealing with this specific and challenging multidisciplinary subject, i.e. particles in industrial, environmental and biomedical flows and the combination of fluid mechanics, solid body mechanics with various aspects of specific applications.
International Nuclear Information System (INIS)
Feburie, V.; Giot, M.; Granger, S.; Seynhaeve, J.M.
1992-06-01
The leaks through steam-generator cracks are the subject of a research carried out in cooperation between EDF and UCL. A software called ECREVISSE to predict the mass flow rate has been developed and has been successfully validated. The purpose of the paper is to present the mathematical model used in ECREVISSE as well as some comparison between the results and the presently available data. The model takes into account the persistence of some metastable liquid in the crack and the special flow pattern which appears in such particular geometry. Although the model involves the use of several correlations (friction, heat transfer), no adjustment of parameters against the data has been needed, neither in the single-phase part of the flow, or in the two-phase part. (authors). 8 figs., 1 tab., 20 refs
Robust Optical Flow Estimation
Directory of Open Access Journals (Sweden)
Javier Sánchez Pérez
2013-10-01
Full Text Available n this work, we describe an implementation of the variational method proposed by Brox etal. in 2004, which yields accurate optical flows with low running times. It has several benefitswith respect to the method of Horn and Schunck: it is more robust to the presence of outliers,produces piecewise-smooth flow fields and can cope with constant brightness changes. Thismethod relies on the brightness and gradient constancy assumptions, using the information ofthe image intensities and the image gradients to find correspondences. It also generalizes theuse of continuous L1 functionals, which help mitigate the effect of outliers and create a TotalVariation (TV regularization. Additionally, it introduces a simple temporal regularizationscheme that enforces a continuous temporal coherence of the flow fields.
Fluid Flow at Branching Junctions
Sochi, Taha
2013-01-01
The flow of fluids at branching junctions plays important kinematic and dynamic roles in most biological and industrial flow systems. The present paper highlights some key issues related to the flow of fluids at these junctions with special emphasis on the biological flow networks particularly blood transportation vasculature.
Directory of Open Access Journals (Sweden)
Nilankush Acharya
2016-06-01
Full Text Available The present article investigates the squeezing flow of two types of nanofluids such as Cu-water and Cu-kerosene between two parallel plates in the presence of magnetic field. The governing non-linear partial differential equations are transformed into ordinary differential equations by applying suitable similarity transformation and then solved numerically using RK-4 method with shooting technique and analytically using differential transformation method (DTM. The influence of arising relevant parameters on flow characteristics has been discussed through graphs and tables. A comparative study has been taken into account between existing results and present work and it is found to be in excellent harmony.
Araujo, Vitor; Viana, Marcelo
2010-01-01
In this book, the authors present the elements of a general theory for flows on three-dimensional compact boundaryless manifolds, encompassing flows with equilibria accumulated by regular orbits. The book aims to provide a global perspective of this theory and make it easier for the reader to digest the growing literature on this subject. This is not the first book on the subject of dynamical systems, but there are distinct aspects which together make this book unique. Firstly, this book treats mostly continuous time dynamical systems, instead of its discrete counterpart, exhaustively treated
Flow Analysis Software Toolkit
Watson, Velvin; Castagnera, Karen; Plessel, Todd; Merritt, Fergus; Kelaita, Paul; West, John; Sandstrom, Tim; Clucas, Jean; Globus, AL; Bancroft, Gordon;
1993-01-01
Flow Analysis Software Toolkit (FAST) computer program provides software environment facilitating visualization of data. Collection of separate programs (modules) running simultaneously and helps user to examine results of numerical and experimental simulations. Intended for graphical depiction of computed flows, also assists in analysis of other types of data. Combines capabilities of such programs as PLOT3D, RIP, SURF, and GAS into one software environment with modules sharing data. All modules have consistent, highly interactive graphical user interface. Modular construction makes it flexible and extensible. Environment custom-configured, and new modules developed and added as needed. Written in ANSI compliant FORTRAN 77 and C language.
Basniev, Kaplan S; Chilingar, George V 0
2012-01-01
The mechanics of fluid flow is a fundamental engineering discipline explaining both natural phenomena and human-induced processes, and a thorough understanding of it is central to the operations of the oil and gas industry. This book, written by some of the world's best-known and respected petroleum engineers, covers the concepts, theories, and applications of the mechanics of fluid flow for the veteran engineer working in the field and the student, alike. It is a must-have for any engineer working in the oil and gas industry.
International Nuclear Information System (INIS)
Hsu, Y.Y.
1974-01-01
The following papers related to two-phase flow are summarized: current assumptions made in two-phase flow modeling; two-phase unsteady blowdown from pipes, flow pattern in Laval nozzle and two-phase flow dynamics; dependence of radial heat and momentum diffusion; transient behavior of the liquid film around the expanding gas slug in a vertical tube; flooding phenomena in BWR fuel bundles; and transient effects in bubble two-phase flow. (U.S.)
Using Crossflow for Flow Measurements and Flow Analysis
Energy Technology Data Exchange (ETDEWEB)
Gurevich, A.; Chudnovsky, L.; Lopeza, A. [Advanced Measurement and Analysis Group Inc., Ontario (Canada); Park, M. H. [Sungjin Nuclear Engineering Co., Ltd., Gyeongju (Korea, Republic of)
2016-10-15
Ultrasonic Cross Correlation Flow Measurements are based on a flow measurement method that is based on measuring the transport time of turbulent structures. The cross correlation flow meter CROSSFLOW is designed and manufactured by Advanced Measurement and Analysis Group Inc. (AMAG), and is used around the world for various flow measurements. Particularly, CROSSFLOW has been used for boiler feedwater flow measurements, including Measurement Uncertainty Recovery (MUR) reactor power uprate in 14 nuclear reactors in the United States and in Europe. More than 100 CROSSFLOW transducers are currently installed in CANDU reactors around the world, including Wolsung NPP in Korea, for flow verification in ShutDown System (SDS) channels. Other CROSSFLOW applications include reactor coolant gross flow measurements, reactor channel flow measurements in all channels in CANDU reactors, boiler blowdown flow measurement, and service water flow measurement. Cross correlation flow measurement is a robust ultrasonic flow measurement tool used in nuclear power plants around the world for various applications. Mathematical modeling of the CROSSFLOW agrees well with laboratory test results and can be used as a tool in determining the effect of flow conditions on CROSSFLOW output and on designing and optimizing laboratory testing, in order to ensure traceability of field flow measurements to laboratory testing within desirable uncertainty.
Is flow verification necessary
International Nuclear Information System (INIS)
Beetle, T.M.
1986-01-01
Safeguards test statistics are used in an attempt to detect diversion of special nuclear material. Under assumptions concerning possible manipulation (falsification) of safeguards accounting data, the effects on the statistics due to diversion and data manipulation are described algebraically. A comprehensive set of statistics that is capable of detecting any diversion of material is defined in terms of the algebraic properties of the effects. When the assumptions exclude collusion between persons in two material balance areas, then three sets of accounting statistics are shown to be comprehensive. Two of the sets contain widely known accountancy statistics. One of them does not require physical flow verification - comparisons of operator and inspector data for receipts and shipments. The third set contains a single statistic which does not require physical flow verification. In addition to not requiring technically difficult and expensive flow verification, this single statistic has several advantages over other comprehensive sets of statistics. This algebraic approach as an alternative to flow verification for safeguards accountancy is discussed in this paper
DEFF Research Database (Denmark)
Tsirogiannis, Konstantinos; Haverkort, Herman
2011-01-01
Computing watersheds on triangulated terrain models in a robust manner is a difficult task as it is sensitive to noise that appears in the elevation values of the input. This is amplified by the existence of many very small watersheds (corresponding to spurious minima) that obscure the overall hy...... to use a robust flow model together with exact arithmetic....
Kaufman, Miron; Fodor, Petru S.
A detailed analysis of the fluid flow in Tadmor's unwound channel model of the single screw extruder is performed by combining numerical and analytical methods. Using the analytical solution for the longitudinal velocity field (in the limit of zero Reynolds number) allows us to devote all the computational resources solely for a detailed numerical solution of the transversal velocity field. This high resolution 3D model of the fluid flow in a single-screw extruder allows us to identify the position and extent of Moffatt eddies that impede mixing. We further consider the erosion of particles (e.g. carbon-black agglomerates) advected by the polymeric flow. We assume a particle to be made of primary fragments bound together. In the erosion process a primary fragment breaks out of a given particle. Particles are advected by the laminar flow and they disperse because of the shear stresses imparted by the fluid. The time evolution of the numbers of particles of different sizes is described by the Bateman coupled differential equations used to model radioactivity. Using the particle size distribution we compute an entropic fragmentation index which varies from 0 for a monodisperse system to 1 for an extreme poly-disperse system.
CERN. Geneva
2015-01-01
My talk will be covering my work as a whole over the course of the semester. The focus will be on using energy flow calibration in ECAL to check the precision of the corrections made by the light monitoring system used to account for transparency loss within ECAL crystals due to radiation damage over time.
Indian Academy of Sciences (India)
A multi-component wind tunnel balance, working with fibre-optic sensors, was already demonstrated by the authors in ... often for mapping surface pressure fields on wind tunnel models. The paint is a fluorescent ... When a gas turbine engine operates close to its peak performance, flow within the com- pressor can become ...
DEFF Research Database (Denmark)
Hansen, Elo Harald
1998-01-01
Learning objectives:* To provide an introduction to automated assays* To describe the basic principles of FIA * To demonstrate the capabilities of FIA in relation to batch assays and conventional continuous flow systems* To show that FIA allows one to augment existing analytical techniques* To show...
Böser, W.; Belfroid, S.P.C.
2013-01-01
Generally large scale carbon capture projects require pipeline systems for the transporting of the CO2 from its point of capture to the storage site. The article will give information on the proposed operational management system. This has to work for all process situations, ranging from steady flow
Energy Technology Data Exchange (ETDEWEB)
Eshraghi, H [Iran University of Science and Technology (IUST), School of Physics, Institute for Studies in Theoretical Physics and Mathematics, Tehran (Iran, Islamic Republic of); Gibbon, J D [Department of Mathematics, Imperial College London, London SW7 2AZ (United Kingdom)
2008-08-29
After a review of some of the recent works by Holm and Gibbon on quaternions and their application to Lagrangian flows, particularly the incompressible Euler equations and the equations of ideal MHD, this paper investigates the compressible and relativistic Euler equations using these methods.
Indian Academy of Sciences (India)
This is a simple exercise in elementary fluid dynamics for the undergraduate and the secondary school level. Here, we explore the flow of water through an orifice at the bottom of a cylindri- cal bottle/tank, first through a tube attached to the bottom of the bottle/tank and then without the tube. The experiment is easy to perform.
Posthuma-Trumpie, G.A.; Amerongen, van A.
2012-01-01
A simple version of immunochemical-based methods is the Lateral Flow Assay (LFA). It is a dry chemistry technique (reagents are included); the fluid from the sample runs through a porous membrane (often nitrocellulose) by capillary force. Typically the membrane is cut as a strip of 0.5*5 cm. In most
DEFF Research Database (Denmark)
Chen, Peiyuan; Chen, Zhe; Bak-Jensen, Birgitte
2008-01-01
This paper reviews the development of the probabilistic load flow (PLF) techniques. Applications of the PLF techniques in different areas of power system steady-state analysis are also discussed. The purpose of the review is to identify different available PLF techniques and their corresponding...
Enceladus' Enigmatic Heat Flow
Howett, C.; Spencer, J. R.; Spencer, D.; Verbiscer, A.; Hurford, T.; Segura, M.
2013-12-01
Accurate knowledge of Enceladus' heat flow is important because it provides a vital constraint on Enceladus' tidal dissipation mechanisms, orbital evolution, and the physical processes that generate the plumes. In 2011 we published an estimate of the current heat flow from Enceladus' active south polar terrain: 15.8 +/- 3.1 GW (Howett et al., 2011). This value was calculated by first estimating by modeling, and then removing, the passive component from 17 to 1000 micron observations made of the entire south polar terrain by Cassini's Composite Infrared Spectrometer (CIRS). The heat flow was then directly calculated from the residual, assumed endogenic, component. The derived heat flow of 15.8 GW was surprisingly high, about 10 times greater than that predicted by steady-state tidal heating (Meyer and Wisdom, 2007). CIRS has also returned high spatial resolution observations of Enceladus' active south polar terrain. Two separate observations are used: 9 to 16 micron observations taken over nearly the complete south polar terrain and a single 17 to 1000 micron scan over Damascus, Baghdad and Cairo. The shorter wavelength observations are only sensitive to high temperature emission (>70 K), and so longer wavelength observations are required (despite their limited spatial coverage) to estimate the low temperature emission from the stripes. Analysis of these higher resolution observations tells a different story of Enceladus' endogenic heat flow: the preliminary estimate of the heat flow from the active tiger stripes using these observations is 4.2 GW. An additional 0.5 GW must be added to this number to account for the latent heat release by the plumes (Ingersoll and Pankine 2009), giving a total preliminary estimate of 4.9 GW. The discrepancy in these two numbers is significant and we are currently investigating the cause. One possible reason is that there is significantly higher endogenic emission from the regions between the tiger stripes than we currently estimate
Efficient modelling of aerodynamic flows in the boundary layer for high performance computing
CSIR Research Space (South Africa)
Smith, L
2011-01-01
Full Text Available A unique technique to couple boundary-layer solutions with an inviscid solver is introduced. The boundary-layer solution is obtained using the two-integral method to solve displacement thickness with Newton’s method, at a fraction of the cost of a...
Davis, L. C.
2015-03-01
The Texas A&M Transportation Institute estimated that traffic congestion cost the United States 121 billion in 2011 (the latest data available). The cost is due to wasted time and fuel. In addition to accidents and road construction, factors contributing to congestion include large demand, instability of high-density free flow and selfish behavior of drivers, which produces self-organized traffic bottlenecks. Extensive data collected on instrumented highways in various countries have led to a better understanding of traffic dynamics. From these measurements, Boris Kerner and colleagues developed a new theory called three-phase theory. They identified three major phases of flow observed in the data: free flow, synchronous flow and wide moving jams. The intermediate phase is called synchronous because vehicles in different lanes tend to have similar velocities. This congested phase, characterized by lower velocities yet modestly high throughput, frequently occurs near on-ramps and lane reductions. At present there are only two widely used methods of congestion mitigation: ramp metering and the display of current travel-time information to drivers. To find more effective methods to reduce congestion, researchers perform large-scale simulations using models based on the new theories. An algorithm has been proposed to realize Wardrop equilibria with real-time route information. Such equilibria have equal travel time on alternative routes between a given origin and destination. An active area of current research is the dynamics of connected vehicles, which communicate wirelessly with other vehicles and the surrounding infrastructure. These systems show great promise for improving traffic flow and safety.
CSIR Research Space (South Africa)
Smakhtin, VU
2001-01-10
Full Text Available prolonged dry weather’. This definition does not make a clear distinction between low flows and droughts. Low flows is a seasonal phenomenon, and an integral component of a flow regime of any river. Drought, on the other hand, is a natural event...-flow generating mechanisms is rather limited. At the same time, identification of relative importance of various low-flow generation mechanisms and factors should ideally precede any low-flow analysis and also form an integral part of developing plans...
Pressure Driven Poiseuille Flow
DEFF Research Database (Denmark)
Stotz, Ingo Leonardo; Iaffaldano, Giampiero; Davies, D. Rhodri
2018-01-01
and lithosphere mutually exchange, by virtue of Newton's third law of motion. In light of these constraints, the notion that subduction is the main driver of present–day Pacific plate motion becomes somewhat unviable, as the pulling force that would be required by slabs exceeds the maximum available from......The Pacific plate is thought to be driven mainly by slab pull, associated with subduction along the Aleutians–Japan, Marianas–Izu–Bonin and Tonga–Kermadec trenches. This implies that viscous flow within the sub–Pacific asthenosphere is mainly generated by overlying plate motion (i.e. Couette flow......), and that the associated shear–stresses at the lithosphere's base are resisting such motion. Recent studies on glacial isostatic adjustment and lithosphere dynamics provide tighter constraints on the viscosity and thickness of Earth's asthenosphere and, therefore, on the amount of shear–stress that asthenosphere...
International Nuclear Information System (INIS)
Dershowitz, W; Herbert, A.; Long, J.
1989-03-01
The hydrology of the SCV site will be modelled utilizing discrete fracture flow models. These models are complex, and can not be fully cerified by comparison to analytical solutions. The best approach for verification of these codes is therefore cross-verification between different codes. This is complicated by the variation in assumptions and solution techniques utilized in different codes. Cross-verification procedures are defined which allow comparison of the codes developed by Harwell Laboratory, Lawrence Berkeley Laboratory, and Golder Associates Inc. Six cross-verification datasets are defined for deterministic and stochastic verification of geometric and flow features of the codes. Additional datasets for verification of transport features will be documented in a future report. (13 figs., 7 tabs., 10 refs.) (authors)
Structural power flow measurement
Energy Technology Data Exchange (ETDEWEB)
Falter, K.J.; Keltie, R.F.
1988-12-01
Previous investigations of structural power flow through beam-like structures resulted in some unexplained anomalies in the calculated data. In order to develop structural power flow measurement as a viable technique for machine tool design, the causes of these anomalies needed to be found. Once found, techniques for eliminating the errors could be developed. Error sources were found in the experimental apparatus itself as well as in the instrumentation. Although flexural waves are the carriers of power in the experimental apparatus, at some frequencies longitudinal waves were excited which were picked up by the accelerometers and altered power measurements. Errors were found in the phase and gain response of the sensors and amplifiers used for measurement. A transfer function correction technique was employed to compensate for these instrumentation errors.
Ricciardi, Roberto; Huskens, Jurriaan; Verboom, Willem
2015-08-24
Nanocatalysis in flow is catalysis by metallic nanoparticles (NPs; 1-50 nm) performed in microstructured reactors. These catalytic processes make use of the enhanced catalytic activity and selectivity of NPs and fulfill the requirements of green chemistry. Anchoring catalytically active metal NPs within a microfluidic reactor enhances the reagent/catalyst interaction, while avoiding diffusion limitations experienced in classical approaches. Different strategies for supporting NPs are reviewed herein, namely, packed-bed reactors, monolithic flow-through reactors, wall catalysts, and a selection of novel approaches (NPs embedded on nanotubes, nanowires, catalytic membranes, and magnetic NPs). Through a number of catalytic reactions, such as hydrogenations, oxidations, and cross-coupling reactions, the advantages and possible drawbacks of each approach are illustrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Langlois, William E
2014-01-01
Leonardo wrote, 'Mechanics is the paradise of the mathematical sciences, because by means of it one comes to the fruits of mathematics' ; replace 'Mechanics' by 'Fluid mechanics' and here we are." - from the Preface to the Second Edition Although the exponential growth of computer power has advanced the importance of simulations and visualization tools for elaborating new models, designs and technologies, the discipline of fluid mechanics is still large, and turbulence in flows remains a challenging problem in classical physics. Like its predecessor, the revised and expanded Second Edition of this book addresses the basic principles of fluid mechanics and solves fluid flow problems where viscous effects are the dominant physical phenomena. Much progress has occurred in the nearly half a century that has passed since the edition of 1964. As predicted, aspects of hydrodynamics once considered offbeat have risen to importance. For example, the authors have worked on problems where variations in viscosity a...
Energy Technology Data Exchange (ETDEWEB)
Dall' Anese, Emiliano; Simonetto, Andrea
2018-03-01
This paper considers distribution networks featuring inverter-interfaced distributed energy resources, and develops distributed feedback controllers that continuously drive the inverter output powers to solutions of AC optimal power flow (OPF) problems. Particularly, the controllers update the power setpoints based on voltage measurements as well as given (time-varying) OPF targets, and entail elementary operations implementable onto low-cost microcontrollers that accompany power-electronics interfaces of gateways and inverters. The design of the control framework is based on suitable linear approximations of the AC power-flow equations as well as Lagrangian regularization methods. Convergence and OPF-target tracking capabilities of the controllers are analytically established. Overall, the proposed method allows to bypass traditional hierarchical setups where feedback control and optimization operate at distinct time scales, and to enable real-time optimization of distribution systems.
Koczula, Katarzyna M; Gallotta, Andrea
2016-06-30
Lateral flow assays (LFAs) are the technology behind low-cost, simple, rapid and portable detection devices popular in biomedicine, agriculture, food and environmental sciences. This review presents an overview of the principle of the method and the critical components of the assay, focusing on lateral flow immunoassays. This type of assay has recently attracted considerable interest because of its potential to provide instantaneous diagnosis directly to patients. The range and interpretation of results and parameters used for evaluation of the assay will also be discussed. The main advantages and disadvantages of LFAs will be summarized and relevant future improvements to testing devices and strategies will be proposed. Finally, the major recent advances and future diagnostic applications in the LFA field will be explored. © 2016 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.
Koczula, Katarzyna M.
2016-01-01
Lateral flow assays (LFAs) are the technology behind low-cost, simple, rapid and portable detection devices popular in biomedicine, agriculture, food and environmental sciences. This review presents an overview of the principle of the method and the critical components of the assay, focusing on lateral flow immunoassays. This type of assay has recently attracted considerable interest because of its potential to provide instantaneous diagnosis directly to patients. The range and interpretation of results and parameters used for evaluation of the assay will also be discussed. The main advantages and disadvantages of LFAs will be summarized and relevant future improvements to testing devices and strategies will be proposed. Finally, the major recent advances and future diagnostic applications in the LFA field will be explored. PMID:27365041
DEFF Research Database (Denmark)
Andersen, Frans Ørsted
2010-01-01
Artiklen handler om flow og fordybelse i et nyt tværfagligt / naturfagligt undervisningskoncept, "Overvågningens dilemma", til brug i folkeskolens 7.-9.kl. og på gymnasiale uddannelser. Konceptet sætter fokus på den overvågning der foregår og er mulig i nutidens IT og hi-tec samfund og der arbejd...
International Nuclear Information System (INIS)
Anon.
1992-01-01
This chapter addresses the cash flow analysis of dual-purpose power plants. The topics discussed include the impact of inflation (including the relative inflation of individual cost components such as purchased power, supplemental power, standby charges, buy back rate, heating fuel costs, power plants costs, staffing, maintenance, insurance, and administrative charges), controlling costs, purchased power and fuel price projections, varying the assumptions, financing, and modeling of tax impacts
2006-09-01
used in this analysis is based on the full 2D time-dependent Navier - Stocks equations coupled with 2D electrodynamics equation in the low magnetic...includes the treatment of chemical reacting flows on the base of full Navier - Stockes approach, chemical kinetics model, and MHD effects model...code family, PlasmAero based on full Navier -Stokes 8 equations, MHD approximation of Maxwell equations, and plasma-chemical kinetics equations is an
Divergent flow isoelectric focusing
Czech Academy of Sciences Publication Activity Database
Šlais, Karel
2008-01-01
Roč. 29, č. 12 (2008), s. 2451-2457 ISSN 0173-0835 R&D Projects: GA AV ČR IAAX00310701; GA ČR GA203/06/1179 Institutional research plan: CEZ:AV0Z40310501 Keywords : isoelectric focusing * divergent flow * pI markers Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.509, year: 2008
Dillon, Joshua V.; Langmore, Ian; Tran, Dustin; Brevdo, Eugene; Vasudevan, Srinivas; Moore, Dave; Patton, Brian; Alemi, Alex; Hoffman, Matt; Saurous, Rif A.
2017-01-01
The TensorFlow Distributions library implements a vision of probability theory adapted to the modern deep-learning paradigm of end-to-end differentiable computation. Building on two basic abstractions, it offers flexible building blocks for probabilistic computation. Distributions provide fast, numerically stable methods for generating samples and computing statistics, e.g., log density. Bijectors provide composable volume-tracking transformations with automatic caching. Together these enable...
Analysis of High Order Difference Methods for Multiscale Complex Compressible Flows
Sjoegreen, Bjoern; Yee, H. C.; Tang, Harry (Technical Monitor)
2002-01-01
Accurate numerical simulations of complex multiscale compressible viscous flows, especially high speed turbulence combustion and acoustics, demand high order schemes with adaptive numerical dissipation controls. Standard high resolution shock-capturing methods are too dissipative to capture the small scales and/or long-time wave propagations without extreme grid refinements and small time steps. An integrated approach for the control of numerical dissipation in high order schemes with incremental studies was initiated. Here we further refine the analysis on, and improve the understanding of the adaptive numerical dissipation control strategy. Basically, the development of these schemes focuses on high order nondissipative schemes and takes advantage of the progress that has been made for the last 30 years in numerical methods for conservation laws, such as techniques for imposing boundary conditions, techniques for stability at shock waves, and techniques for stable and accurate long-time integration. We concentrate on high order centered spatial discretizations and a fourth-order Runge-Kutta temporal discretizations as the base scheme. Near the bound-aries, the base scheme has stable boundary difference operators. To further enhance stability, the split form of the inviscid flux derivatives is frequently used for smooth flow problems. To enhance nonlinear stability, linear high order numerical dissipations are employed away from discontinuities, and nonlinear filters are employed after each time step in order to suppress spurious oscillations near discontinuities to minimize the smearing of turbulent fluctuations. Although these schemes are built from many components, each of which is well-known, it is not entirely obvious how the different components be best connected. For example, the nonlinear filter could instead have been built into the spatial discretization, so that it would have been activated at each stage in the Runge-Kutta time stepping. We could think
Measurement of flow in supercritical flow regime using cutthroat flumes
Indian Academy of Sciences (India)
[6] Smith R E, Chery D L, Renard K G and Gwinn W R 1981. Supercritical flow flumes for measuring sediment-laden flow,. United States Department of Agriculture, Technical Bulletin number 1655. [7] Manekar V L, Porey P D and Ingle R N 2007 Discharge rela- tion for cutthroat flume under free flow condition. J. Irrig.
Low flow Coriolis flow controller with piezo operated control valve
Katerberg, M.R.; Ratering, G.H.J.M.; Platenkamp, T.H.; van de Geest, J.W.; Klein Hesselink, S.; Lötters, Joost Conrad
2014-01-01
We developed a compact conventional steel tube Coriolis mass flow controller for low flow rates down to 10mg/min and up to 3g/min in one instrument. The mechanical construction of the flow controller has been optimized to have a low internal dead volume for control speed and stability. An on board
Dunn, James C.; Hardee, Harry C.; Striker, Richard P.
1985-01-01
A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packer-type seals are provided along the probe above and below the heater pads.
Conversational flow promotes solidarity.
Koudenburg, Namkje; Postmes, Tom; Gordijn, Ernestine H
2013-01-01
Social interaction is fundamental to the development of various aspects of "we-ness". Previous research has focused on the role the content of interaction plays in establishing feelings of unity, belongingness and shared reality (a cluster of variables referred to as solidarity here). The present paper is less concerned with content, but focuses on the form of social interaction. We propose that the degree to which conversations flow smoothly or not is, of itself, a cue to solidarity. We test this hypothesis in samples of unacquainted and acquainted dyads who communicate via headsets. Conversational flow is disrupted by introducing a delay in the auditory feedback (vs. no delay). Results of three studies show that smoothly coordinated conversations (compared with disrupted conversations and a control condition) increase feelings of belonging and perceptions of group entitativity, independently of conversation content. These effects are driven by the subjective experience of conversational flow. Our data suggest that this process occurs largely beyond individuals' control. We conclude that the form of social interaction is a powerful cue for inferring group solidarity. Implications for the impact of modern communication technology on developing a shared social identity are discussed.
Towards Sustainable Flow Management - Introduction
DEFF Research Database (Denmark)
Moss, Timothy; Elle, Morten
1998-01-01
Outlines the conditions for the three Local Agenda 21 case-studies in the Sustainable Flow Management Project......Outlines the conditions for the three Local Agenda 21 case-studies in the Sustainable Flow Management Project...
Towards Sustainable Flow Management - Introduction
DEFF Research Database (Denmark)
Moss, Timothy; Elle, Morten
2001-01-01
Outlines the conditions for the three Local Agenda 21 case-studies in the Sustainable Flow Management project......Outlines the conditions for the three Local Agenda 21 case-studies in the Sustainable Flow Management project...
U.S. Environmental Protection Agency — These data accompany the manuscript 'Critical Review of Elementary Flows in LCA Data'. Each file presents a subgroup of the elementary flows (data used for analysis)...
Asymmetric reactions in continuous flow
Directory of Open Access Journals (Sweden)
Xiao Yin Mak
2009-04-01
Full Text Available An overview of asymmetric synthesis in continuous flow and microreactors is presented in this review. Applications of homogeneous and heterogeneous asymmetric catalysis as well as biocatalysis in flow are discussed.
... your child so they can help monitor your child's asthma symptoms . Why Should I Measure My Flow Rate? ... help parents determine what might be triggering their child's asthma. How Do You Use a Peak Flow Meter? ...
VanOsdol, John G.
2013-06-25
The disclosure provides a pulse jet mixing vessel for mixing a plurality of solid particles. The pulse jet mixing vessel is comprised of a sludge basin, a flow surface surrounding the sludge basin, and a downcoming flow annulus between the flow surface and an inner shroud. The pulse jet mixing vessel is additionally comprised of an upper vessel pressurization volume in fluid communication with the downcoming flow annulus, and an inner shroud surge volume separated from the downcoming flow annulus by the inner shroud. When the solid particles are resting on the sludge basin and a fluid such as water is atop the particles and extending into the downcoming flow annulus and the inner shroud surge volume, mixing occurs by pressurization of the upper vessel pressurization volume, generating an inward radial flow over the flow surface and an upwash jet at the center of the sludge basin.
National Research Council Canada - National Science Library
Smith, Charles
1997-01-01
An experimental study of the effects of spatially-limited (i.e. localized) surface suction on unsteady laminar and turbulent junction flows was performed using hydrogen bubble flow visualization and Particle Image Velocimetry (PIV...
Investigations on flow reversal in stratified horizontal flow
International Nuclear Information System (INIS)
Staebler, T.; Meyer, L.; Schulenberg, T.; Laurien, E.
2005-01-01
The phenomena of flow reversal in stratified flows are investigated in a horizontal channel with application to the Emergency Core Cooling System (ECCS) in Pressurized Water Reactors (PWR). In case of a Loss-of-Coolant-Accident (LOCA), coolant can be injected through a secondary pipe within the feeding line of the primary circuit, the so called hot leg, counter-currently to the steam flow. It is essential that the coolant reaches the reactor core to prevent overheating. Due to high temperatures in such accident scenarios, steam is generated in the core, which escapes from the reactor vessel through the hot leg. In case of sufficiently high steam flow rates, only a reduced amount of coolant or even no coolant will be delivered to the reactor core. The WENKA test facility at the Institute for Nuclear and Energy Technologies (IKET) at Forschungszentrum Karlsruhe is capable to investigate the fluid dynamics of two-phase flows in such scenarios. Water and air flow counter-currently in a horizontal channel made of clear acrylic glass to allow full optical access. Flow rates of water and air can be varied independently within a wide range. Once flow reversal sets in, a strong hysteresis effect must be taken into account. This was quantified during the present investigations. Local experimental data are needed to expand appropriate models on flow reversal in horizontal two-phase flow and to include them into numerical codes. Investigations are carried out by means of Particle Image Velocimetry (PIV) to obtain local flow velocities without disturbing the flow. Due to the wavy character of the flow, strong reflections at the interfacial area must be taken into account. Using fluorescent particles and an optical filter allows eliminating the reflections and recording only the signals of the particles. The challenges in conducting local investigations in stratified wavy flows by applying optical measurement techniques are discussed. Results are presented and discussed allowing
Dynamic simulation of wavy-stratified two-phase flow with the one-dimensional two-fluid model
Fullmer, William D.
conditions. This appears to result in non-convergence when particular solutions at a specific time are compared using different numerical discretizations. However, it is shown that the chaotic solutions exhibit an invariant spectrum in wavenumber space that can be used to assess the convergence of solutions. This concept is applied to a Kelvin-Helmholtz experiment of kerosene and liquid water in a tilted channel whereby many slightly different simulations are run and averaged to determine the mean behavior. Comparisons to experimental data are favorable; especially considering the limitations of applying a one-dimensional model to a dynamic simulation of wavy channel flow. When the analysis is extended to consider air-water flows, several additional challenges are encountered related to the long-wavelength inviscid Kelvin-Helmholtz instability, which is the instability inherent to the one-dimensional two-fluid model. The transition from stratified to wavy flow is significantly over-predicted, i.e., requires a larger velocity to become unstable than observed experimentally. The wave sheltering model of Brauner and Maron (1993) is included in the interfacial shear model and calibrated for flow in a rectangular channel. However, when the unstable flow regime is simulated a wavy flow pattern does not develop as in the liquid-liquid case. Due to the near absence of inertia in the lighter gas phase, viscosity and surface tension are unable to bound the growth of disturbances within the physical limitations of the channel geometry. Transitions to regions of single phase flow result, indicating a slug flow pattern where wavy flow should exist. A novel approach is taken where the instability mechanism, here the sheltering force, is adjusted based on local geometric conditions, namely the void fraction gradient. Comparison to data shows promising results, although a large degree of uncertainty in such an approach remains due to a lack of local experimental data.
Information Flow in Logical Environments
Kent, Robert E.
2016-01-01
This paper describes information flow within logical environments. The theory of information flow, the logic of distributed systems, was first defined by Barwise and Seligman (Information Flow: The Logic of Distributed Systems. 1997). Logical environments are a semantic-oriented version of institutions. The theory of institutions, which was initiated by Goguen and Burstall (Institutions: Abstract Model Theory for Specification and Programming. 1992), is abstract model theory. Information flow...
Simulation of gas compressible flow by free surface water flow
International Nuclear Information System (INIS)
Altafini, C.R.; Silva Ferreira, R.T. da
1981-01-01
The analogy between the water flow with a free surface and the compressible fluid flow, commonly called hydraulic analogy, is analyzed and its limitations are identified. The water table is the equipment used for this simulation, which allows the quatitative analysis of subsonic and supersonic flow with a low cost apparatus. The hydraulic analogy is applied to subsonic flow around circular cylinders and supersonic flow around cones. The results are compared with available theoretical and experimental data and a good agreement is achieved. (Author) [pt
Risk assessment future cash flows
Chachina H. G.
2012-01-01
This article is about risk assessment in planning future cash flows. Discount rate in DCF-model must include four factors: risk cash flow, inflation, value of investments, turnover assets. This has an influence net present value cash flow and make his incomparable.
Peak flow meter use - slideshow
... page: //medlineplus.gov/ency/presentations/100202.htm Peak flow meter use - Series—Peak flow meter use - part one To use the sharing ... slide 7 out of 7 Overview A peak flow meter helps you check how well your asthma ...
Flow shapes and higher harmonics in anisotropic transverse collective flow
Energy Technology Data Exchange (ETDEWEB)
Argintaru, Danut; Baban, Valerica [Constanta Maritime University, Faculty of Navigation and Naval Transport, Constanta (Romania); Besliu, Calin; Jipa, Alexandru; Grossu, Valeriu [University of Bucharest, Faculty of Physics, Bucharest (Romania); Esanu, Tiberiu; Cherciu, Madalin [Institute of Space Sciences Bucharest-Magurele, Bucharest (Romania)
2017-01-15
In this paper we show that by using a jet-finder algorithm (the Anti-k{sub T} one) on UrQMD/C simulated (Au+Au at 4, 10 and 15A GeV) collisions, we can identify different flow shape structures (single flow stream events, two flow streams events, three flow streams events, etc.) and order the bulk of events in equivalence flow shape classes. Considering these flow streams as the main directions of anisotropic transverse flow, we show that the Fourier coefficients v{sub n} of anisotropic flow are better emphasized when we analyze the different event flow shape classes than when the events are mixed. Also, if we do not know the real orientation of the reaction plane, we can use as reference the Flow stream 1 - the main particle flow stream - orientation (Ψ{sub Flowstream} {sub 1}) to highlight the initial shape of the participant nuclear matter in a central to peripheral collision, and the orientation of the participant plane of order n. (orig.)
Gas flow meter and method for measuring gas flow rate
Robertson, Eric P.
2006-08-01
A gas flow rate meter includes an upstream line and two chambers having substantially equal, fixed volumes. An adjustable valve may direct the gas flow through the upstream line to either of the two chambers. A pressure monitoring device may be configured to prompt valve adjustments, directing the gas flow to an alternate chamber each time a pre-set pressure in the upstream line is reached. A method of measuring the gas flow rate measures the time required for the pressure in the upstream line to reach the pre-set pressure. The volume of the chamber and upstream line are known and fixed, thus the time required for the increase in pressure may be used to determine the flow rate of the gas. Another method of measuring the gas flow rate uses two pressure measurements of a fixed volume, taken at different times, to determine the flow rate of the gas.
Dynamics of Supercritical Flows
2012-08-26
Joncas and Maslow (53) performed a linear stability study of a compressible coaxial jet with velocity and temperature profiles characteristic of a...interface d‟une couche de mélange liquide-gaz”, Thèse de Doctorat, Université Joseph Fourier, Grenoble, 1997. 53. Perrault-Joncas, D., Maslowe , S. A...characteristics of the flow (Sevilla et al. [35], Perrault-Joncas and Maslowe [49]). Sevilla et al. [35] investigate the effect of outer to inner jet
Providing Compassion through Flow
Directory of Open Access Journals (Sweden)
Lydia Royeen
2015-07-01
Full Text Available Meg Kral, MS, OTR/L, CLT, is the cover artist for the Summer 2015 issue of The Open Journal of Occupational Therapy. Her untitled piece of art is an oil painting and is a re-creation of a photograph taken while on vacation. Meg is currently supervisor of outpatient services at Rush University Medical Center. She is lymphedema certified and has a specific interest in breast cancer lymphedema. Art and occupational therapy serve similar purposes for Meg: both provide a sense of flow. She values the outcomes, whether it is a piece of art or improved functional status
International Nuclear Information System (INIS)
Sagan, C.
1979-01-01
Voyager 1 close-encounter photomosaics have clarified both the coloration of Io and its surface variation. These colour patterns seem explicable in terms of liquid sulphur produced in ionian volcanoes and solfataras and quenched at Io ambient temperatures approximately equal to 135 K. The liquid sulphur flow fronts and frozen rivers which appear in the Voyager images are discussed. It is argued that the volcanic deposition rates and the vapour pressure over sulphur melts are both consistent with the notion that the surface of Io changes significantly in geologically very short periods of time. (UK)
DEFF Research Database (Denmark)
Lyk-Jensen, Stéphanie
2011-01-01
model. The analysis uses a structural relationship to explain the structure of the exchange of the goods—a relationship that can be used in the year of forecast. This article also provides a new methodology for converting monetary aggregates into quantity aggregates. The resulting commodity growth rates....... This article models long-term dynamic physical trade flows and estimates a dynamic panel data model for foreign trade for the EU15 and two countries from the EFTA (European Free Trade Association) 1967–2002. The analysis suggests that a dynamic three-way-effects gravity equation is the best-fitted econometric...
DEFF Research Database (Denmark)
Schulz, Alexander
2015-01-01
assimilate movement includes an apoplasmic step, this mode is called apoplasmic loading. Well established is also the polymer-trap loading mode, where the phloem-transport sugars are raffinose-family oligomers in herbaceous plants. Also this mode depends on the investment of energy, here for sugar...... is currently matter of discussion, called passive symplasmic loading. Based on the limited material available, this review compares the different loading modes and suggests that diffusion is the driving force in apoplasmic loaders, while bulk flow plays an increasing role in plants having a continuous...
Experimental techniques in unsteady flows
Oldfield, M. L. G.
1990-12-01
Notes for four lectures intended as a practical user guide to some unsteady aerodynamic flow experimental measurement techniques are presented. Unsteady flows to be measured, including frequency and length scale, large scale unsteadiness, turbulence, boundary layer transition, shear layers and wakes, periodically time varying flows, shock waves and vortex flows, are explained. Wind tunnel requirements, intrusive measurements by hot wire and film anemometry and pressure probes, and surface measurements are described. Optical techniques covered include Schlieren photography, shadowgraph, holography, laser anemometry and flow tracing. Instrumentation and data acquisition and processing of unsteady data, using frequency analysis by fast Fourier transforms, convolution and correlation are described.
Overview of zonal flow physics
International Nuclear Information System (INIS)
Diamond, P.H.; Itoh, K.; Itoh, S.-I.; Hahm, T.S.
2005-01-01
Zonal flows, by which we mean azimuthally symmetric band-like shear flows, are ubiquitous phenomena in nature and the laboratory. It is now widely recognized that zonal flows are a key constituent in virtually all cases and regimes of drift wave turbulence, indeed, so much so that this classic problem is now frequently referred to as 'drift wave-zonal flow turbulence'. In this theory overview, we present new viewpoints and unifying concepts which facilitate understanding of zonal flow physics, via theory, computation and their confrontation with the results of laboratory experiment. Special emphasis is placed on identifying avenues for further progress. (author)
Industrial energy-flow management
International Nuclear Information System (INIS)
Lampret, Marko; Bukovec, Venceslav; Paternost, Andrej; Krizman, Srecko; Lojk, Vito; Golobic, Iztok
2007-01-01
Deregulation of the energy market has created new opportunities for the development of new energy-management methods based on energy assets, risk management, energy efficiency and sustainable development. Industrial energy-flow management in pharmaceutical systems, with a responsible approach to sustainable development, is a complex task. For this reason, an energy-information centre, with over 14,000 online measured data/nodes, was implemented. This paper presents the energy-flow rate, exergy-flow rate and cost-flow rate diagrams, with emphasis on cost-flow rate per energy unit or exergy unit of complex pharmaceutical systems
Ground vortex flow field investigation
Kuhn, Richard E.; Delfrate, John H.; Eshleman, James E.
1988-01-01
Flow field investigations were conducted at the NASA Ames-Dryden Flow Visualization Facility (water tunnel) to investigate the ground effect produced by the impingement of jets from aircraft nozzles on a ground board in a STOL operation. Effects on the overall flow field with both a stationary and a moving ground board were photographed and compared with similar data found in other references. Nozzle jet impingement angles, nozzle and inlet interaction, side-by-side nozzles, nozzles in tandem, and nozzles and inlets mounted on a flat plate model were investigated. Results show that the wall jet that generates the ground effect is unsteady and the boundary between the ground vortex flow field and the free-stream flow is unsteady. Additionally, the forward projection of the ground vortex flow field with a moving ground board is one-third less than that measured over a fixed ground board. Results also showed that inlets did not alter the ground vortex flow field.
Experimental investigation of cavity flows
Energy Technology Data Exchange (ETDEWEB)
Loeland, Tore
1998-12-31
This thesis uses LDV (Laser Doppler Velocimetry), PIV (Particle Image Velocimetry) and Laser Sheet flow Visualisation to study flow inside three different cavity configurations. For sloping cavities, the vortex structure inside the cavities is found to depend upon the flow direction past the cavity. The shape of the downstream corner is a key factor in destroying the boundary layer flow entering the cavity. The experimental results agree well with numerical simulations of the same geometrical configurations. The results of the investigations are used to find the influence of the cavity flow on the accuracy of the ultrasonic flowmeter. A method to compensate for the cavity velocities is suggested. It is found that the relative deviation caused by the cavity velocities depend linearly on the pipe flow. It appears that the flow inside the cavities should not be neglected as done in the draft for the ISO technical report on ultrasonic flowmeters. 58 refs., 147 figs., 2 tabs.
Exotic RG flows from holography
Energy Technology Data Exchange (ETDEWEB)
Kiritsis, Elias [APC, Universite Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris, Sorbonne Paris Cite (France); Crete Center for Theoretical Physics, Institute for Theoretical and Computational Physics, Department of Physics, University of Crete, Heraklion (Greece); Crete Center for Quantum Complexity and Nanotechnology, Department of Physics, University of Crete, Heraklion (Greece); Nitti, Francesco; Silva Pimenta, Leandro [APC, Universite Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris, Sorbonne Paris Cite (France)
2017-02-15
Holographic RG flows are studied in an Einstein-dilaton theory with a general potential. The superpotential formalism is utilized in order to characterize and classify all solutions that are associated with asymptotically AdS space-times. Such solutions correspond to holographic RG flows and are characterized by their holographic β-functions. Novel solutions are found that have exotic properties from a RG point-of view. Some have β-functions that are defined patch-wise and lead to flows where the β-function changes sign without the flow stopping. Others describe flows that end in non-neighboring extrema in field space. Finally others describe regular flows between two minima of the potential and correspond holographically to flows driven by the VEV of an irrelevant operator in the UV CFT. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Experimental research of the couette flow with cross flow
Directory of Open Access Journals (Sweden)
Schmidt Marcus
2012-04-01
Full Text Available When a solid cylinder is rotating inside a hollow cylinder, a characteristic fluid flow occurs inside the gap between the two cylinders, caused by the adhesion of the fluid at the walls. This flow problem is widely known as the Couette-flow. If an additional flow entrances through a radial located feedhole at the outer hollow cylinder, there is an interaction between the cross flow and the Couette-flow. In result there are complex three dimensional flow structures in the gap at the area around the feedhole. These arising flow structures are closely related with the technical important flow inside the gap of hydrodynamic lubricated journal bearings. When the flow conditions inside the bearing gap are well explored and appreciated, it will be possible to give suggestions for constructive details like the design, the location and the dimension of the feedhole for longer lifecycles or an even more efficiently running. In this paper the test rig of the bearing model will be presented. Moreover some representative results from researches with a Laser-Doppler-Velocimeter (LDV in comparison with the output of three dimensional numerical simulations will be illustrated.
Thermosensitive gas flow sensor
International Nuclear Information System (INIS)
Berlicki, T.; Osadnik, S.; Prociow, E.
1997-01-01
Results of investigations on thermal gas flow sensor have been presented. The sensor consists of three thin film resistors Si+Ta. The circuit was designed in the form of two bridges; one of them serves for measurement of the heater temperature, the second one for the measurement of temperature difference of peripheral resistors. The measurement of output voltage versus the rate of nitrogen flow at various power levels dissipated at the heater and various temperatures have been made. The measurements were carried out in three versions; (a) at constant temperature of the heater, (b) at constant power dissipated in the heater, controlled by the power of the heater, (c) at constant temperature of the heater controlled by the power dissipated in the peripheral resistors of the sensor. Due to measurement range it is advantageous to stabilize the temperature of the heater, especially by means of the power supplied to the peripheral resistors. In this case the wider measurement range can be obtained. (author)
Valenzuela, Javier
2001-01-01
A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.
Bureau, Lionel; Coupier, Gwennou; Dubois, Frank; Duperray, Alain; Farutin, Alexander; Minetti, Christophe; Misbah, Chaouqi; Podgorski, Thomas; Tsvirkun, Daria; Vysokikh, Mikhail
2017-01-01
The absence of gravity during space flight can alter cardio-vascular functions partially due to reduced physical activity. This affects the overall hemodynamics, and in particular the level of shear stresses to which blood vessels are submitted. Long-term exposure to space environment is thus susceptible to induce vascular remodeling through a mechanotransduction cascade that couples vessel shape and function with the mechanical cues exerted by the circulating cells on the vessel walls. Central to such processes, the glycocalyx - i.e. the micron-thick layer of biomacromolecules that lines the lumen of blood vessels and is directly exposed to blood flow - is a major actor in the regulation of biochemical and mechanical interactions. We discuss in this article several experiments performed under microgravity, such as the determination of lift force and collective motion in blood flow, and some preliminary results obtained in artificial microfluidic circuits functionalized with endothelium that offer interesting perspectives for the study of the interactions between blood and endothelium in healthy condition as well as by mimicking the degradation of glycocalyx caused by long space missions. A direct comparison between experiments and simulations is discussed. xml:lang="fr"
International Nuclear Information System (INIS)
Y. Wu
2004-01-01
The purpose of this report is to document the unsaturated zone (UZ) flow models and submodels, as well as the flow fields that have been generated using the UZ flow model(s) of Yucca Mountain, Nevada. In this report, the term ''UZ model'' refers to the UZ flow model and the several submodels, which include tracer transport, temperature or ambient geothermal, pneumatic or gas flow, and geochemistry (chloride, calcite, and strontium) submodels. The term UZ flow model refers to the three-dimensional models used for calibration and simulation of UZ flow fields. This work was planned in the ''Technical Work Plan (TWP) for: Unsaturated Zone Flow Analysis and Model Report Integration'' (BSC 2004 [DIRS 169654], Section 1.2.7). The table of included Features, Events, and Processes (FEPs), Table 6.2-11, is different from the list of included FEPs assigned to this report in the ''Technical Work Plan for: Unsaturated Zone Flow Analysis and Model Report Integration'' (BSC 2004 [DIRS 169654], Table 2.1.5-1), as discussed in Section 6.2.6. The UZ model has revised, updated, and enhanced the previous UZ model (BSC 2001 [DIRS 158726]) by incorporating the repository design with new grids, recalibration of property sets, and more comprehensive validation effort. The flow fields describe fracture-fracture, matrix-matrix, and fracture-matrix liquid flow rates, and their spatial distributions as well as moisture conditions in the UZ system. These three-dimensional UZ flow fields are used directly by Total System Performance Assessment (TSPA). The model and submodels evaluate important hydrogeologic processes in the UZ as well as geochemistry and geothermal conditions. These provide the necessary framework to test hypotheses of flow and transport at different scales, and predict flow and transport behavior under a variety of climatic conditions. In addition, the limitations of the UZ model are discussed in Section 8.11
Online traffic flow model applying dynamic flow-density relation
International Nuclear Information System (INIS)
Kim, Y.
2002-01-01
This dissertation describes a new approach of the online traffic flow modelling based on the hydrodynamic traffic flow model and an online process to adapt the flow-density relation dynamically. The new modelling approach was tested based on the real traffic situations in various homogeneous motorway sections and a motorway section with ramps and gave encouraging simulation results. This work is composed of two parts: first the analysis of traffic flow characteristics and second the development of a new online traffic flow model applying these characteristics. For homogeneous motorway sections traffic flow is classified into six different traffic states with different characteristics. Delimitation criteria were developed to separate these states. The hysteresis phenomena were analysed during the transitions between these traffic states. The traffic states and the transitions are represented on a states diagram with the flow axis and the density axis. For motorway sections with ramps the complicated traffic flow is simplified and classified into three traffic states depending on the propagation of congestion. The traffic states are represented on a phase diagram with the upstream demand axis and the interaction strength axis which was defined in this research. The states diagram and the phase diagram provide a basis for the development of the dynamic flow-density relation. The first-order hydrodynamic traffic flow model was programmed according to the cell-transmission scheme extended by the modification of flow dependent sending/receiving functions, the classification of cells and the determination strategy for the flow-density relation in the cells. The unreasonable results of macroscopic traffic flow models, which may occur in the first and last cells in certain conditions are alleviated by applying buffer cells between the traffic data and the model. The sending/receiving functions of the cells are determined dynamically based on the classification of the
Arterial secondary blood flow patterns visualized with vector flow ultrasound
DEFF Research Database (Denmark)
Pedersen, Mads Møller; Pihl, Michael Johannes; Hansen, Jens Munk
2011-01-01
and velocity magnitudes the blood flow patterns were visualised with streamlines in Matlab (Mathworks, Natick, MA, USA). The rotational flow was quantified by the angular frequency for each cardiac cycle, and the mean rotational frequencies and standard deviations were calculated for the abdominal aorta f-1......This study presents the first quantification and visualisation of secondary flow patterns with vector flow ultrasound. The first commercial implementation of the vector flow method Transverse Oscillation was used to obtain in-vivo, 2D vector fields in real-time. The hypothesis of this study...... was that the rotational direction is constant within each artery. Three data sets of 10 seconds were obtained from three main arteries in healthy volunteers. For each data set the rotational flow patterns were identified during the diastole. Each data set contains a 2D vector field over time and with the vector angles...
Radioisotopic flow scanning for portal blood flow and portal hypertension
International Nuclear Information System (INIS)
Hesdorffer, C.S.; Bezwoda, W.R.; Danilewitz, M.D.; Esser, J.D.; Tobias, M.
1987-01-01
The use of a simple, noninvasive, isotope scanning technique for the determination of relative portal blood flow and detection of portal hypertension is described. Using this technique the presence of portal hypertension was demonstrated in seven of nine patients known to have elevated portal venous pressure. By contrast, esophageal varices were demonstrated in only five of these patients, illustrating the potential value of the method. Furthermore, this technique has been adapted to the study of portal blood flow in patients with myeloproliferative disorders with splenomegaly but without disturbances in hepatic architecture. Results demonstrate that the high relative splenic flow resulting from the presence of splenomegaly may in turn be associated with elevated relative portal blood flow and portal hypertension. The theoretic reasons for the development of flow-related portal hypertension and its relationship to splenic blood flow are discussed
Surface obstacles in pulsatile flow
Carr, Ian A.; Plesniak, Michael W.
2017-11-01
Flows past obstacles mounted on flat surfaces have been widely studied due to their ubiquity in nature and engineering. For nearly all of these studies, the freestream flow over the obstacle was steady, i.e., constant velocity, unidirectional flow. Unsteady, pulsatile flows occur frequently in biology, geophysics, biomedical engineering, etc. Our study is aimed at extending the comprehensive knowledge base that exists for steady flows to considerably more complex pulsatile flows. Characterizing the vortex and wake dynamics of flows around surface obstacles embedded in pulsatile flows can provide insights into the underlying physics in all wake and junction flows. In this study, we experimentally investigate the wake of two canonical obstacles: a cube and a circular cylinder with an aspect ratio of unity. Our previous studies of a surface-mounted hemisphere in pulsatile flow are used as a baseline for these two new, more complex geometries. Phase-averaged PIV and hot-wire anemometry are used to characterize the dynamics of coherent structures in the wake and at the windward junction of the obstacles. Complex physics occur during the deceleration phase of the pulsatile inflow. We propose a framework for understanding these physics based on self-induced vortex propagation, similar to the phenomena exhibited by vortex rings.
Flow instability in flow past O-grooved circular cylinder
Energy Technology Data Exchange (ETDEWEB)
Kim, Jaehee; Yang, Kyungsoo [Inha University, Inchun (Korea, Republic of)
2015-04-15
This study was devoted to elucidating the change in the flow characteristics of a laminar flow past a circular cylinder by modifying the cylinder shape with O-grooves. A numerical analysis was performed in a two-dimensional framework. The cylinder was represented using an immersed boundary method and marker particles on a Cartesian grid system. The number and locations of the O-grooves were the key parameters. An analysis of the flow pattern and flow induced forces was performed at Re = 40 and 50. In addition, we calculated the critical Reynolds number depending on the number of O-grooves and their locations.
Fluid mechanics a concise introduction to the theory
Yih, Chia-Shun
1969-01-01
Fundamentals ; the basic equations ; general theorems for the flow of an inviscid fluid ; irrotational flows of an inviscid fluid of constant density ; waves in an incompressible ; effects of viscosity ; heat transfer and boundary layers of a gas ; hydrodynamic stability ; turbulence ; basic thermodynamics ; curvilinear coordinates.
International Nuclear Information System (INIS)
Andreani, M.; Yadigaroglu, G.
1989-12-01
Dispersed flow film boiling is the heat transfer regime that occurs at high void fractions in a heated channel. The way this transfer mode is modelled in the NRC computer codes (RELAP5 and TRAC) and the validity of the assumption and empirical correlations used is discussed. An extensive review of the theoretical and experimental work related with heat transfer to highly dispersed mixtures reveals the basic deficiencies of these models: the investigation refers mostly to the typical conditions of low rate bottom reflooding, since the simulation of this physical situation by the computer codes has often showed poor results. The alternative models that are available in the literature are reviewed, and their merits and limits are highlighted. The modification that could improve the physics of the models implemented in the codes are identified. (author) 13 figs., 123 refs
Moore, James E., Jr.; Bertram, Christopher D.
2018-01-01
The supply of oxygen and nutrients to tissues is performed by the blood system and involves a net leakage of fluid outward at the capillary level. One of the principal functions of the lymphatic system is to gather this fluid and return it to the blood system to maintain overall fluid balance. Fluid in the interstitial spaces is often at subatmospheric pressure, and the return points into the venous system are at pressures of approximately 20 cmH2O. This adverse pressure difference is overcome by the active pumping of collecting lymphatic vessels, which feature closely spaced one-way valves and contractile muscle cells in their walls. Passive vessel squeezing causes further pumping. The dynamics of lymphatic pumping have been investigated experimentally and mathematically, revealing complex behaviors that indicate that the system performance is robust against minor perturbations in pressure and flow. More serious disruptions can lead to incurable swelling of tissues called lymphedema.
DEFF Research Database (Denmark)
Hansen, Elo Harald
2004-01-01
This chapter provides an introduction to automated chemical analysis, which essentially can be divided into two groups: batch assays, where the solution is stationary while the container is moved through a number of stations where various unit operations performed; and continuous-flow procedures,......, but it permits thr execution of novel and unique analytical procedures which are difficult or even impossible by conventional means. The performance and applicability of FIA, SI and LOV are illustrated by a series of practical examples....... FIA is based on the creation of a concentration gradient of the injected sample solution and on reproducible and precise timing of all events, it allows exploitation of a transient read-out. This in turn implies that not only does FIA allow the augmentation of existing analytical techniques...
International Nuclear Information System (INIS)
Riva, R.; Bador, B.; Marchand, M.; Lebaigue, O.
1999-01-01
Fuel cells are energy converters, which directly and continuously produce electricity from paired oxidation reduction-reactions: In most cases, the reactants are oxygen and hydrogen with water as residue. There are several types of fuel cells using various electrolytes and working at different temperatures. Proton Exchange Membrane Fuel Cells are, in particular, studied in the GESTEAU facility. PEMFC performance is chiefly limited by two thermal-hydraulic phenomena: the drying of membranes and the flooding of gas distributors. Up to now, work has been focused on water flooding of gas channels. This has showed the influence of flow type on the electrical behaviour of the cells and the results obtained have led to proposals for new duct geometries. (authors)
Ockendon, Hilary
2016-01-01
Now in its second edition, this book continues to give readers a broad mathematical basis for modelling and understanding the wide range of wave phenomena encountered in modern applications. New and expanded material includes topics such as elastoplastic waves and waves in plasmas, as well as new exercises. Comprehensive collections of models are used to illustrate the underpinning mathematical methodologies, which include the basic ideas of the relevant partial differential equations, characteristics, ray theory, asymptotic analysis, dispersion, shock waves, and weak solutions. Although the main focus is on compressible fluid flow, the authors show how intimately gasdynamic waves are related to wave phenomena in many other areas of physical science. Special emphasis is placed on the development of physical intuition to supplement and reinforce analytical thinking. Each chapter includes a complete set of carefully prepared exercises, making this a suitable textbook for students in applied mathematics, ...
Ching, Kathryn H
2015-01-01
Lateral flow immunoassays (LFIAs) are a staple in the field of rapid diagnostics. These small handheld devices require no specialized training or equipment to operate, and generate a result within minutes of sample application. They are an ideal format for many types of home test kits, for emergency responders and for food manufacturers and producers looking for a quick evaluation of a given sample. LFIAs rely on high quality monoclonal antibodies that recognize the analyte of interest. As monoclonal antibody technology becomes more accessible to smaller laboratories, there has been increased interest in developing LFIA prototypes for potential commercial manufacture. In this chapter, the basics of designing and building an LFIA prototype are described.
International Nuclear Information System (INIS)
Ladd-Lively, Jennifer L
2008-01-01
The objectives of the work discussed in this report were to: (1) develop a flow loop that would simulate the purified uranium-bearing aqueous stream exiting the solvent extraction process in a natural uranium conversion plant (NUCP); (2) develop a test plan that would simulate normal operation and disturbances that could be anticipated in an NUCP; (3) use the flow loop to test commercially available flowmeters for use as safeguards monitors; and (4) recommend a flowmeter for production-scale testing at an NUCP. There has been interest in safeguarding conversion plants because the intermediate products [uranium dioxide (UO 2 ), uranium tetrafluoride (UF 4 ), and uranium hexafluoride (UF 6 )] are all suitable uranium feedstocks for producing special nuclear materials. Furthermore, if safeguards are not applied virtually any nuclear weapons program can obtain these feedstocks without detection by the International Atomic Energy Agency (IAEA). Historically, IAEA had not implemented safeguards until the purified UF 6 product was declared as feedstock for enrichment plants. H. A. Elayat et al. provide a basic definition of a safeguards system: 'The function of a safeguards system on a chemical conversion plant is in general terms to verify that no useful nuclear material is being diverted to use in a nuclear weapons program'. The IAEA now considers all highly purified uranium compounds as candidates for safeguarding. DOE is currently interested in 'developing instruments, tools, strategies, and methods that could be of use to the IAEA in the application of safeguards' for materials found in the front end of the nuclear fuel cycle-prior to the production of the uranium hexafluoride or oxides that have been the traditional starting point for IAEA safeguards. Several national laboratories, including Oak Ridge, Los Alamos, Lawrence Livermore, and Brookhaven, have been involved in developing tools or techniques for safeguarding conversion plants. This study was sponsored by
Xia, Yidong
a computer program. By using an AD tool, the manpower can be significantly reduced for deriving the flux Jacobians, which can be quite complicated, tedious, and error-prone if done by hand or symbolic arithmetic software, depending on the complexity of the numerical flux scheme. In addition, the workload for code maintenance can also be largely reduced in case the underlying flux scheme is updated. The approximate system of linear equations arising from the Newton linearization is solved by the general minimum residual (GMRES) algorithm with lower-upper symmetric gauss-seidel (LUSGS) preconditioning. This GMRES+LU-SGS linear solver is the most robust and efficient for implicit time integration of the discretized Navier-Stokes equations when the AD-based flux Jacobians are provided other than the other two approaches. The developed HWENO(P1P2) method is used to compute a variety of well-documented compressible inviscid and viscous flow test cases on 3D hybrid grids, including some standard benchmark test cases such as the Sod shock tube, flow past a circular cylinder, and laminar flow past a at plate. The computed solutions are compared with either analytical solutions or experimental data, if available to assess the accuracy of the HWENO(P 1P2) method. Numerical results demonstrate that the HWENO(P 1P2) method is able to not only enhance the accuracy of the underlying HWENO(P1) method, but also ensure the linear and non-linear stability at the presence of strong discontinuities. An extensive study of grid convergence analysis on various types of elements: tetrahedron, prism, hexahedron, and hybrid prism/hexahedron, for a number of test cases indicates that the developed HWENO(P1P2) method is able to achieve the designed third-order accuracy of spatial convergence for smooth inviscid flows: one order higher than the underlying second-order DG(P1) method without significant increase in computing costs and storage requirements. The performance of the the developed
Efficiency of osmotic pipe flows
DEFF Research Database (Denmark)
Haaning, Louise Sejling; Jensen, Kaare Hartvig; Helix Nielsen, Claus
2013-01-01
on the relative magnitude of radial diffusion and advection as well as the ratio of the osmotic velocity to pumping velocity, in very good agreement with experiments and with no adjustable parameters. Our analysis provides criteria that are useful for optimizing osmotic flow processes in, e.g., water purification......We present experiments and theory for flows of sugar or salt solutions in cylindrical tubes with semipermeable walls (hollow fiber membranes) immersed in water, quantifying the strength of the osmotic driving force in relation to the dimensionless parameters that specify the system. The pumping...... efficiency of these flows is limited by the presence of “unstirred” concentration boundary layers near the tube walls, and our primary aim is to understand and quantify these layers and their effect on the flow. We measure the outlet flow rate Qout while varying the inlet flow rate Q*, concentration c...
Flow, affect and visual creativity.
Cseh, Genevieve M; Phillips, Louise H; Pearson, David G
2015-01-01
Flow (being in the zone) is purported to have positive consequences in terms of affect and performance; however, there is no empirical evidence about these links in visual creativity. Positive affect often--but inconsistently--facilitates creativity, and both may be linked to experiencing flow. This study aimed to determine relationships between these variables within visual creativity. Participants performed the creative mental synthesis task to simulate the creative process. Affect change (pre- vs. post-task) and flow were measured via questionnaires. The creativity of synthesis drawings was rated objectively and subjectively by judges. Findings empirically demonstrate that flow is related to affect improvement during visual creativity. Affect change was linked to productivity and self-rated creativity, but no other objective or subjective performance measures. Flow was unrelated to all external performance measures but was highly correlated with self-rated creativity; flow may therefore motivate perseverance towards eventual excellence rather than provide direct cognitive enhancement.
Active combustion flow modulation valve
Hensel, John Peter; Black, Nathaniel; Thorton, Jimmy Dean; Vipperman, Jeffrey Stuart; Lambeth, David N; Clark, William W
2013-09-24
A flow modulation valve has a slidably translating hollow armature with at least one energizable coil wound around and fixably attached to the hollow armature. The energizable coil or coils are influenced by at least one permanent magnet surrounding the hollow armature and supported by an outer casing. Lorentz forces on the energizable coils which are translated to the hollow armature, increase or decrease the flow area to provide flow throttling action. The extent of hollow armature translation depends on the value of current supplied and the direction of translation depends on the direction of current flow. The compact nature of the flow modulation valve combined with the high forces afforded by the actuator design provide a flow modulation valve which is highly responsive to high-rate input control signals.
Endovascular blood flow measurement system
Khe, A. K.; Cherevko, A. A.; Chupakhin, A. P.; Krivoshapkin, A. L.; Orlov, K. Yu
2016-06-01
In this paper an endovascular measurement system used for intraoperative cerebral blood flow monitoring is described. The system is based on a Volcano ComboMap Pressure and Flow System extended with analogue-to-digital converter and PC laptop. A series of measurements performed in patients with cerebrovascular pathologies allows us to introduce “velocity-pressure” and “flow rate-energy flow rate” diagrams as important characteristics of the blood flow. The measurement system presented here can be used as an additional instrument in neurosurgery for assessment and monitoring of the operation procedure. Clinical data obtained with the system are used for construction of mathematical models and patient-specific simulations. The monitoring of the blood flow parameters during endovascular interventions was approved by the Ethics Committee at the Meshalkin Novosibirsk Research Institute of Circulation Pathology and included in certain surgical protocols for pre-, intra- and postoperative examinations.
Characterization of Accelerating Pipe Flow.
1988-03-01
Journal of Chemical Engineering of Japan , vol...92, January 1970. 17. K. Kataoka, T. Kawabata, and K. Miki, "The Start-Up Response of Pipe Flow to a Step Change in Flow Rate," Journal of Chemical Engineering of Japan , vol...Pipe Flows," Journal of Chemical Engineering of Japan , vol. 9, no. 6, pp. 431-439, 1975. 19. E. van de Sande, A.P. Belde, B.J.G. Hamer, and W.
High Speed Smoke Flow Visualization.
1981-03-01
releasable to the National Technical Information Service (NTIS). At NTIS, it will be available to the general public, including foreign nations. This... information . 9 The initial work focused on the evaluation of the flow field within the high speed flow visualization tunnels and the optical and...with the high speed flow visuLl iza tion; it waIs used to take simul taneous smoke/Schlieren photographs. Siice it allowed for this unique method of
Identification of material flow systems.
Bauer, G; Deistler, M; Gleiss, A; Glenck, E; Matyus, T
1997-01-01
Material Flow Analysis (MFA) has become an important instrument in environmental science and pollution research. In this paper, we look at the MFA problem as a particularly structured system identification problem. Special emphasis is given to the linear, static case, where we describe a procedure for reconciliating the flow measurements and for estimating the unmeasured flows and the transfer coefficients by taking into account a priori restrictions such as balance equations.
Directory of Open Access Journals (Sweden)
Tsz Leung Yip
2013-03-01
Full Text Available A model is developed for studying marine traffic flow through classical traffic flow theories, which can provide us with a better understanding of the phenomenon of traffic flow of ships. On one hand, marine traffic has its special features and is fundamentally different from highway, air and pedestrian traffic. The existing traffic models cannot be simply extended to marine traffic without addressing marine traffic features. On the other hand, existing literature on marine traffic focuses on one ship or two ships but does not address the issues in marine traffic flow.
Surface obstacles in pulsatile flow
Carr, Ian A.; Plesniak, Michael W.
2016-11-01
Flows past obstacles mounted on flat surfaces have been widely studied due to their ubiquity in nature and engineering. For nearly all of these studies, the freestream flow over the obstacle was steady, i.e. constant velocity unidirectional flow. Unsteady, pulsatile flows occur frequently in biology, geophysics, biomedical engineering, etc. Our study is aimed at extending the comprehensive knowledge base that exists for steady flows to considerably more complex pulsatile flows. Beyond the important practical applications, characterizing the vortex and wake dynamics of flows around surface obstacles embedded in pulsatile flows can provide insights into the underlying physics in all wake and junction flows. In this study, we experimentally investigated the wake of four canonical surface obstacles: hemisphere, cube, and circular cylinders with aspect ratio of 1:1 and 2:1. Phase-averaged PIV and hot-wire anemometry are used to characterize the dynamics of coherent structures in the wake and at the windward junction of the obstacles. Complex physics occur during the deceleration phase of the pulsatile inflow. We propose a framework for understanding these physics based on self-induced vortex propagation, similar to the phenomena exhibited by vortex rings. This material is based in part upon work supported by the National Science Foundation under Grant Number CBET-1236351, and GW Centeor Biomimetics and Bioinspired Engineering (COBRE).
International Nuclear Information System (INIS)
Delaje, Dzh.
1984-01-01
General hypothesis used to simplify the equations, describing two-phase flows, are considered. Two-component and one-component models of two-phase flow, as well as Zuber and Findlay model for actual volumetric steam content, and Wallis model, describing the given phase rates, are presented. The conclusion is made, that the two-component model, in which values averaged in time are included, is applicable for the solving of three-dimensional tasks for unsteady two-phase flow. At the same time, using the two-component model, including values, averaged in space only one-dimensional tasks for unsteady two-phase flow can be solved
Fundamentals of gas particle flow
Rudinger, G
1980-01-01
Fundamentals of Gas-Particle Flow is an edited, updated, and expanded version of a number of lectures presented on the "Gas-Solid Suspensions course organized by the von Karman Institute for Fluid Dynamics. Materials presented in this book are mostly analytical in nature, but some experimental techniques are included. The book focuses on relaxation processes, including the viscous drag of single particles, drag in gas-particles flow, gas-particle heat transfer, equilibrium, and frozen flow. It also discusses the dynamics of single particles, such as particles in an arbitrary flow, in a r
Energy Technology Data Exchange (ETDEWEB)
P. Dixon
2004-02-11
The purpose of this Model Report is to document the unsaturated zone (UZ) fluid flow and tracer transport models and submodels as well as the flow fields generated utilizing the UZ Flow and Transport Model of Yucca Mountain (UZ Model), Nevada. This work was planned in ''Technical Work Plan (TWP) for: Performance Assessment Unsaturated Zone'' (BSC 2002 [160819], Section 1.10, Work Package AUZM06). The UZ Model has revised, updated, and enhanced the previous UZ Flow Model REV 00 ICN 01 (BSC 2001 [158726]) by incorporation of the conceptual repository design with new grids, recalibration of property sets, and more comprehensive validation effort. The flow fields describe fracture-fracture, matrix-matrix, and fracture-matrix liquid flow rates and their spatial distributions as well as moisture conditions in the UZ system. These 3-D UZ flow fields are used directly by Performance Assessment (PA). The model and submodels evaluate important hydrogeologic processes in the UZ as well as geochemistry and geothermal conditions. These provide the necessary framework to test conceptual hypotheses of flow and transport at different scales and predict flow and transport behavior under a variety of climatic conditions. In addition, this Model Report supports several PA activities, including abstractions, particle-tracking transport simulations, and the UZ Radionuclide Transport Model.
International Nuclear Information System (INIS)
Dixon, P.
2004-01-01
The purpose of this Model Report is to document the unsaturated zone (UZ) fluid flow and tracer transport models and submodels as well as the flow fields generated utilizing the UZ Flow and Transport Model of Yucca Mountain (UZ Model), Nevada. This work was planned in ''Technical Work Plan (TWP) for: Performance Assessment Unsaturated Zone'' (BSC 2002 [160819], Section 1.10, Work Package AUZM06). The UZ Model has revised, updated, and enhanced the previous UZ Flow Model REV 00 ICN 01 (BSC 2001 [158726]) by incorporation of the conceptual repository design with new grids, recalibration of property sets, and more comprehensive validation effort. The flow fields describe fracture-fracture, matrix-matrix, and fracture-matrix liquid flow rates and their spatial distributions as well as moisture conditions in the UZ system. These 3-D UZ flow fields are used directly by Performance Assessment (PA). The model and submodels evaluate important hydrogeologic processes in the UZ as well as geochemistry and geothermal conditions. These provide the necessary framework to test conceptual hypotheses of flow and transport at different scales and predict flow and transport behavior under a variety of climatic conditions. In addition, this Model Report supports several PA activities, including abstractions, particle-tracking transport simulations, and the UZ Radionuclide Transport Model
Large amplitude oscillatory elongation flow
DEFF Research Database (Denmark)
Rasmussen, Henrik K.; Laillé, Philippe; Yu, Kaijia
2008-01-01
A filament stretching rheometer (FSR) was used for measuring the elongation flow with a large amplitude oscillative elongation imposed upon the flow. The large amplitude oscillation imposed upon the elongational flow as a function of the time t was defined as epsilon(t) =(epsilon) over dot(0)t...... with a molecular weight of 145 kg/ mol was subjected to the oscillative flow. The onset of the steady periodic regime is reached at the same Hencky strain as the onset of the steady elongational viscosity ( Lambda = 0). The integral molecular stress function formulation within the 'interchain pressure' concept...
Impact of enhanced flow on the flow system and wastewater ...
African Journals Online (AJOL)
The excess flow on low depth wetlands may cause overflows and destroy both the ecosystem and the livelihood of the local people. In this study, the pattern identification capability of neuro-genetic models was used to estimate the impact of the excess flow on sewage-fed wetlands. Two neural network models were created ...
Coriolis mass flow rate meters for low flows
Mehendale, A.
2008-01-01
The accurate and quick measurement of small mass flow rates (~10 mg/s) of fluids is considered an “enabling technology��? in semiconductor, fine-chemical, and food & drugs industries. Flowmeters based on the Coriolis effect offer the most direct sensing of the mass flow rate, and for this reason do
Jump phenomenon from jam to free flow in traffic flow
社本, 大輔; 友枝, 明保; 西成, 活裕; Daisuke, Shamoto; Akiyasu, Tomoeda; Katsuhiro, Nishinari; 東大工; 東大工; 東大工:独立行政法人科学技術振興機構さきがけ; Department of Aeronautics and Astronautics, Faculty of Engineering, University of Tokyo; Department of Aeronautics and Astronautics, Faculty of Engineering, University of Tokyo; Department of Aeronautics and Astronautics, Faculty of Engineering, University of Tokyo:PRESTO, Japan Science and Technology Corporation
2008-01-01
In real traffic flow, we have found jamp phenomena from jam to free flow. From the viewpoints of fluids dynamics, we can say this phenomenon as 'expansion shock wave.' In conventional fuids dynamics, 'expansion shock wave' can never occur because this phenomenon goes against the 2nd law of themodynamics. We analyzed this phenomenon from viewpoints of fluids dynamics.
Solving the minimum flow problem with interval bounds and flows
Indian Academy of Sciences (India)
and Ciurea et al (2008b) solved the minimum flow problem for bipartite networks, and Ciurea. & Deaconu (2007) solved the ... In Ghiyasvand (2011), a new method to solve the minimum cost flow problem with interval .... multiplication of convex sets, when the fuzzification uses Definition 1 for max–min and order operations.
Experimental Flow Characterization of a Flow Diverting Device
Sparrow, Eph; Chow, Ricky; Campbell, Gary; Divani, Afshin; Sheng, Jian
2012-11-01
Flow diverters, such as the Pipeline Embolization Device, are a new class of endovascular devices for the treatment of intracranial aneurysms. While clinical studies have demonstrated safety and efficacy, their impact on intra-aneurysmal flow is not confirmed experimentally. As such, optimization of the flow diversion behavior is not currently possible. A quasi-3D PIV technique was developed and applied in various glass models at Re = 275 and 550 to determine the changes to flow characteristics due to the deployment of a flow diverter across the aneurysm neck. Outcomes such as mean velocity, wall shear stress, and others metrics will be presented. Glass models with varying radii of curvature and aneurysm locations will be examined. Experiments were performed in a fully index-matched flow facility using ~10 μm diameter polystyrene particles doped with Rhodium 6G dye. The particles were illuminated with a 532nm laser sheet and observed with a CCD camera and a 592nm +/-43 nm bandpass filter. A quasi 3D flow field was reconstructed from multiple orthogonal planes (spaced 0.4mm apart) encompassing the entire glass model. Wall stresses were evaluated from the near-wall flow viscous stresses.
Coupled equations for transient water flow, heat flow, and ...
Indian Academy of Sciences (India)
Hydrogeological systems are earth systems influenced by water. Their behaviors are governed by interacting processes, including flow of fluids, deformation of porous materials, chemical reactions, and transport of matter and energy. Here, coupling among three of these processes is considered: flow of water, heat, and ...
Flow rate measurement in a pipe flow by vortex shedding
Energy Technology Data Exchange (ETDEWEB)
Reik, M.; Bruzzese, C.; Schenkel, T.; Oertel, H. [Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany). Inst. for Fluid Mechanics; Hoecker, R.; Hollmach, M.; Koudal, O. [Endress und Hauser Flowtec AG, Reinach (Switzerland)
2010-06-15
The flow rate measurement of liquid, steam, and gas is one of the most important areas of application for today's field instrumentation. Vortex meters are used in numerous branches of industry to measure the volumetric flow by exploiting the unsteady vortex flow behind a blunt body. The classical Karman vortex street behind a cylinder shows a decrease in Strouhal number with decreasing Reynolds number. Considering the flow behind a vortex shedding device in a pipe the Strouhal-Reynolds number dependence shows a different behaviour for turbulent flows: a decrease in Reynolds number leads to an increase in Strouhal number. This phenomenon was found in the experimental investigations as well as in the numerical results and has been confirmed theoretically by a stability analysis. (orig.)
Blauhut, Veit; Stölzle, Michael; Stahl, Kerstin
2017-04-01
Drought induced low flow extremes, despite a variety of management strategies, can cause direct and indirect impacts on socio economic and ecological functions of rivers. These negative effects determine local risk and are a function of the regional drought hazard and the river system's vulnerability. Whereas drought risk analysis is known to be essential for drought management, risk analysis for low flow is less common. Where no distributed hydrological models exist, merely the local hazard at gauging stations is available to represent the entire catchment. Vulnerability information are only sparsely available. Hence, a comprehensive understanding of the drivers of low flow risk along the longitudinal river profile is often lacking. For two different rivers in southwestern Germany, this study analysed major low flow events of the past five decades. Applying a transdisciplinary approach, the hazard component is assessed by hydro-climatic analysis, hydrological modelling and forward looking stress test scenarios; the vulnerability component is estimated by a combination of impact assessment and vulnerability estimation, based on stakeholder workshops, questionnaires and regional characteristics. The results show distinct differences in low flow risk between the catchments and along the river. These differences are due to: hydrogeological characteristics that govern groundwater-surface water interaction, catchment-specific anthropogenic stimuli such as low flow decrease by near-stream groundwater pumping for public water supply or low flow augmentation by treatment plant discharge. Thus, low flow risk is anthropogenically influenced in both ways: positive and negative. Furthermore, the measured longitudinal profiles highlight the impracticability of single gauges to represent quantitative and qualitative conditions of entire rivers. Hence, this work calls for a comprehensive spatially variable consideration of flow characteristics and human influences to analyse low
Directory of Open Access Journals (Sweden)
Gavril PANDI
2011-03-01
Full Text Available The influenced flow regimes. The presence and activities ofhumanity influences the uniform environmental system, and in this context, therivers water resources. In concordance with this, the natural runoff regime suffersbigger and deeper changes. The nature of these changes depending on the type anddegree of water uses. The multitude of the use cause different types of influence,whit different quantitative aspects. In the same time, the influences havequalitative connotations, too, regarding to the modifications of the yearly watervolume runoff. So the natural runoff regime is modified. After analyzing thedistribution laws of the monthly runoff, there have been differenced four types ofinfluenced runoff regimes. In the excess type the influenced runoff is bigger thanthe natural, continuously in the whole year. The deficient type is characterized byinverse rapports like the first type, in the whole year. In the sinusoidal type, theinfluenced runoff is smaller than the natural in the period when the water isretained in the lake reservoirs, and in the depletion period the situation inverts. Atthe irregular type the ratio between influenced and natural runoff is changeable ina random meaner monthly. The recognition of the influenced regime and the gradeof influence are necessary in the evaluation and analysis of the usable hydrologicalriver resources, in the flood defence activities, in the complex scheme of thehydrographic basins, in the environment design and so on.
Robinson, Julie A.; Tate-Brown, Judy M.
2009-01-01
Using a commercial software CD and minimal up-mass, SNFM monitors the Payload local area network (LAN) to analyze and troubleshoot LAN data traffic. Validating LAN traffic models may allow for faster and more reliable computer networks to sustain systems and science on future space missions. Research Summary: This experiment studies the function of the computer network onboard the ISS. On-orbit packet statistics are captured and used to validate ground based medium rate data link models and enhance the way that the local area network (LAN) is monitored. This information will allow monitoring and improvement in the data transfer capabilities of on-orbit computer networks. The Serial Network Flow Monitor (SNFM) experiment attempts to characterize the network equivalent of traffic jams on board ISS. The SNFM team is able to specifically target historical problem areas including the SAMS (Space Acceleration Measurement System) communication issues, data transmissions from the ISS to the ground teams, and multiple users on the network at the same time. By looking at how various users interact with each other on the network, conflicts can be identified and work can begin on solutions. SNFM is comprised of a commercial off the shelf software package that monitors packet traffic through the payload Ethernet LANs (local area networks) on board ISS.
Briggs, C. K.; Borg, I. Y.
1982-10-01
Flow diagrams to describe the US energy situation are given. In 1981 the energy consumption was 73 quads (or 73 times 10 to the 15th power Btu). Use was down from 75 quads in 1980. Oil continues to dominate the picture as it comprises 45% of the total energy used. Net oil use (exclusive of oil purchased for the Strategic Petroleum Reserve and Exports) fell 8%; oil imports declined 14%. In contrast to oil, use of natural gas and coal remained at 1980 levels. Decreased use of residual oils, principally for electric power generating, account for much of the drop in oil use. Increased use of coal and nuclear energy for power generation almost compensated for the decrease in use of oil in that end use. Transmitted power remained at 1980 levels. The remainder of the drop in energy usage is attributed to price driven conservation, increased efficiencies in end use and the recession that prevailed during most of the year. The share of the energy drop attributable to the recession is estimated by various analysts to be on the order of 40 to 50%.
Intelligent Flow Friction Estimation
Directory of Open Access Journals (Sweden)
Dejan Brkić
2016-01-01
Full Text Available Nowadays, the Colebrook equation is used as a mostly accepted relation for the calculation of fluid flow friction factor. However, the Colebrook equation is implicit with respect to the friction factor (λ. In the present study, a noniterative approach using Artificial Neural Network (ANN was developed to calculate the friction factor. To configure the ANN model, the input parameters of the Reynolds Number (Re and the relative roughness of pipe (ε/D were transformed to logarithmic scales. The 90,000 sets of data were fed to the ANN model involving three layers: input, hidden, and output layers with, 2, 50, and 1 neurons, respectively. This configuration was capable of predicting the values of friction factor in the Colebrook equation for any given values of the Reynolds number (Re and the relative roughness (ε/D ranging between 5000 and 108 and between 10−7 and 0.1, respectively. The proposed ANN demonstrates the relative error up to 0.07% which had the high accuracy compared with the vast majority of the precise explicit approximations of the Colebrook equation.
Directory of Open Access Journals (Sweden)
Sabah Al-Fedaghi
2017-02-01
Full Text Available Aim/Purpose: With information almost effortlessly created and spontaneously available, current progress in Information and Communication Technology (ICT has led to the complication that information must be scrutinized for trustworthiness and provenance. Information systems must become provenance-aware to be satisfactory in accountability, reproducibility, and trustworthiness of data. Background:\tMultiple models for abstract representation of provenance have been proposed to describe entities, people, and activities involved in producing a piece of data, including the Open Provenance Model (OPM and the World Wide Web Consortium. These models lack certain concepts necessary for specifying workflows and encoding the provenance of data products used and generated. Methodology: Without loss of generality, the focus of this paper is on OPM depiction of provenance in terms of a directed graph. We have redrawn several case studies in the framework of our proposed model in order to compare and evaluate it against OPM for representing these cases. Contribution: This paper offers an alternative flow-based diagrammatic language that can form a foundation for modeling of provenance. The model described here provides an (abstract machine-like representation of provenance. Findings: The results suggest a viable alternative in the area of diagrammatic representation for provenance applications. Future Research: Future work will seek to achieve more accurate comparisons with current models in the field.
Intermittency in Complex Flows
Ben Mahjoub, Otman; Redondo, Jose M.
2017-04-01
Experimental results of the complex turbulent wake of a cilinder in 2D [1] and 3D flows [2] were used to investigate the scaling of structure functions, similar research was also performed on wave propagation and breaking in the Ocean [3], in the the stratified Atmosphere (ABL) [4] and in a 100large flume (UPC) for both regular and irregular waves, where long time series of waves propagating and generating breaking turbulence velocity rms and higher order measurements were taken in depth. [3,5] by means of a velocimeter SONTEK3-D. The probability distribution functions of the velocity differences and their non Gaussian distribution related to the energy spectrum indicate that irregularity is an important source of turbulence. From Kolmogorov's K41 and K61 intermittency correction: the p th-order longitudinal velocity structure function δul at scale l in the inertial range of three-dimensional fully developed turbulence is related by ⟨δup⟩ = ⟨(u(x+ l)- u(x))p⟩ ˜ ɛp0/3lp/3 l where ⟨...⟩ represents the spatial average over flow domain, with ɛ0 the mean energy dissipation per unit mass and l is the separation distance. The importance of the random nature of the energy dissipation led to the K62 theory of intermittency, but locality and non-homogeneity are key issues. p p/3 p/3 ξd ⟨δul⟩ ˜ ⟨ɛl ⟩l ˜ l and ξp = p 3 + τp/3 , where now ɛl is a fractal energy dissipation at scale l, τp/3 is the scaling of and ξp is the scaling exponent of the velocity structure function of order p. Both in K41 and K62, the structure functions of third order related to skewness is ξ3 = 1. But this is not true either. We show that scaling exponents ξp do deviate from early studies that only investigated homogeneous turbulence, where a large inertial range dominates. The use of multi-fractal analysis and improvements on Structure function calculations on standard Enhanced mixing is an essential property of turbulence and efforts to alter and to control
Galois Connections for Flow Algebras
DEFF Research Database (Denmark)
Filipiuk, Piotr; Terepeta, Michal Tomasz; Nielson, Hanne Riis
2011-01-01
to the approach taken by Monotone Frameworks and other classical analyses. We present a generic framework for static analysis based on flow algebras and program graphs. Program graphs are often used in Model Checking to model concurrent and distributed systems. The framework allows to induce new flow algebras...
Directional synthetic aperture flow imaging
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt; Nikolov, Svetoslav
2004-01-01
. A plastic tube with an internal diameter of 17 mm was used with an EcoWatt 1 pump generating a laminar, stationary flow. The velocity profile was measured for flow angles of 90 and 60 degrees. The RASMUS research scanner was used for acquiring RF data from 128 elements of the array using 8 emissions with 11...
Ethernet Flow Monitoring with IPFIX
Hofstede, R.J.; Drago, Idilio; Sperotto, Anna; Pras, Aiko
The increasing amount of network traffic and the huge bandwidth needed to carry it requires managers to use scalable solutions to monitor their networks. Nowadays, flow-based techniques, such as Cisco’s NetFlow, provide aggregated network data and an overview of network activity at the IP layer.
Apparatus for measuring fluid flow
Smith, J.E.; Thomas, D.G.
Flow measuring apparatus includes a support loop having strain gages mounted thereon and a drag means which is attached to one end of the support loop and which bends the sides of the support loop and induces strains in the strain gages when a flow stream impacts thereon.
Filtering Undesirable Flows in Networks
Polevoy, G.; Trajanovski, S.; Grosso, P.; de Laat, C.; Gao, X.; Du, H.; Han, M.
2017-01-01
We study the problem of fully mitigating the effects of denial of service by filtering the minimum necessary set of the undesirable flows. First, we model this problem and then we concentrate on a subproblem where every good flow has a bottleneck. We prove that unless P=NP, this subproblem is
Flow properties of concentrated suspensions
Hattori, K.; Izumi, K.
1984-04-01
The viscosity and flow behavior of a concentrated suspension, with special emphasis on fresh concrete containing a superplasticizer, is analyzed according to Newton's law of viscosity. The authors interpreted Newton's law in a new way, and explain non-Newton flow from Newton's law. The outline of this new theory is given. Viscosity of suspensions, and the effect of dispersants are analyzed.
Multiphase flows with phase change
Indian Academy of Sciences (India)
Multiphase flows with phase change are ubiquitous in many industrial sectors ranging from energy and infra-structure to specialty chemicals and pharmaceuticals. My own interest in mul- tiphase flows with phase change started more than 15 years ago when I had initiated work on riser reactor for fluid catalytic cracking and ...
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 8. The Challenge of Fluid Flow - The Diversity of Flow Phenomena. Roddam Narasimha. General Article Volume 10 Issue 8 August 2005 pp 67-79. Fulltext. Click here to view fulltext PDF. Permanent link:
Redox Flow Batteries, a Review
Energy Technology Data Exchange (ETDEWEB)
Knoxville, U. Tennessee; U. Texas Austin; U, McGill; Weber, Adam Z.; Mench, Matthew M.; Meyers, Jeremy P.; Ross, Philip N.; Gostick, Jeffrey T.; Liu, Qinghua
2011-07-15
Redox flow batteries are enjoying a renaissance due to their ability to store large amounts of electrical energy relatively cheaply and efficiently. In this review, we examine the components of redox flow batteries with a focus on understanding the underlying physical processes. The various transport and kinetic phenomena are discussed along with the most common redox couples.
Numerical methods for turbulent flow
Turner, James C., Jr.
1988-01-01
It has generally become accepted that the Navier-Strokes equations predict the dynamic behavior of turbulent as well as laminar flows of a fluid at a point in space away form a discontinuity such as a shock wave. Turbulence is also closely related to the phenomena of non-uniqueness of solutions of the Navier-Strokes equations. These second order, nonlinear partial differential equations can be solved analytically for only a few simple flows. Turbulent flow fields are much to complex to lend themselves to these few analytical methods. Numerical methods, therefore, offer the only possibility of achieving a solution of turbulent flow equations. In spite of recent advances in computer technology, the direct solution, by discrete methods, of the Navier-Strokes equations for turbulent flow fields is today, and in the foreseeable future, impossible. Thus the only economically feasible way to solve practical turbulent flow problems numerically is to use statistically averaged equations governing mean-flow quantities. The objective is to study some recent developments relating to the use of numerical methods to study turbulent flow.
Flow Logics and Operational Semantics
DEFF Research Database (Denmark)
Nielson, Flemming; Nielson, Hanne Riis
1998-01-01
Flow logic is a “fast prototyping” approach to program analysis that shows great promise of being able to deal with a wide variety of languages and calculi for computation. However, seemingly innocent choices in the flow logic as well as in the operational semantics may inhibit proving the analysis...
Boiling flow through diverging microchannel
Indian Academy of Sciences (India)
118–. 1182 kg/m2-s) and heat flux (1.6–19.2 W/cm2) on single and two-phase pressure drop and average heat transfer coefficient has been studied. Concurrently, flow visu- alization is carried out to document the various flow regimes and to ...
Conceptualizing Group Flow: A Framework
Duncan, Jana; West, Richard E.
2018-01-01
This literature review discusses the similarities in main themes between Csikszentmihályi theory of individual flow and Sawyer theory of group flow, and compares Sawyer's theory with existing concepts in the literature on group work both in education and business. Because much creativity and innovation occurs within groups, understanding group…
Flow Cytometry in Pediatric Malignancies.
Handoo, Anil; Dadu, Tina
2018-01-15
The utility of flow cytometry as a useful diagnostic modality for the assessment of hematopoietic neoplasms has been established beyond doubt. In fact, it is now an integral part of the diagnosis and classification of various diseases like leukemias and lymphomas along with molecular studies and cytogenetics. Prognostication and disease monitoring by flow cytometry is also being recognized increasingly as one of the important fortes. This is evident by the number of articles in the published in literature on the minimal residual disease detection by flow cytometry especially in the last decade or so. To add to this, ever growing list of utilities in hematopoietic malignancies, many non-hematopoietic neoplasms can also be analyzed by flow cytometry. The examples include fluid specimens from serous cavity effusions and samples from solid tissues like lymph nodes, reticulo-endothelial tissue, central nervous system tissue, etc. Flow cytometry technique provides a unique blend of rapidity, high sensitivity and specificity compared to cyto-morphology and conventional immunohistochemical staining. It is also remarkable for simultaneous analysis of more than one marker on the cells. Evaluation of limited samples such as cerebrospinal fluid or fine needle aspiration samples makes Flow cytometry a valuable tool. DNA ploidy analysis and assessment of pediatric non-hematopoietic neoplasms by Flow cytometry has envisaged the utility vista of this technique. This review is aimed at providing an insight into the applications of flow cytometry in pediatric malignancies.
Sawyer, Keith
2015-01-01
Keith Sawyer views the spontaneous collaboration of group creativity and improvisation actions as "group flow," which organizations can use to function at optimum levels. Sawyer establishes ideal conditions for group flow: group goals, close listening, complete concentration, being in control, blending egos, equal participation, knowing…
Energy Technology Data Exchange (ETDEWEB)
Y. Wu
2004-11-01
The purpose of this report is to document the unsaturated zone (UZ) flow models and submodels, as well as the flow fields that have been generated using the UZ flow model(s) of Yucca Mountain, Nevada. In this report, the term ''UZ model'' refers to the UZ flow model and the several submodels, which include tracer transport, temperature or ambient geothermal, pneumatic or gas flow, and geochemistry (chloride, calcite, and strontium) submodels. The term UZ flow model refers to the three-dimensional models used for calibration and simulation of UZ flow fields. This work was planned in the ''Technical Work Plan (TWP) for: Unsaturated Zone Flow Analysis and Model Report Integration'' (BSC 2004 [DIRS 169654], Section 1.2.7). The table of included Features, Events, and Processes (FEPs), Table 6.2-11, is different from the list of included FEPs assigned to this report in the ''Technical Work Plan for: Unsaturated Zone Flow Analysis and Model Report Integration'' (BSC 2004 [DIRS 169654], Table 2.1.5-1), as discussed in Section 6.2.6. The UZ model has revised, updated, and enhanced the previous UZ model (BSC 2001 [DIRS 158726]) by incorporating the repository design with new grids, recalibration of property sets, and more comprehensive validation effort. The flow fields describe fracture-fracture, matrix-matrix, and fracture-matrix liquid flow rates, and their spatial distributions as well as moisture conditions in the UZ system. These three-dimensional UZ flow fields are used directly by Total System Performance Assessment (TSPA). The model and submodels evaluate important hydrogeologic processes in the UZ as well as geochemistry and geothermal conditions. These provide the necessary framework to test hypotheses of flow and transport at different scales, and predict flow and transport behavior under a variety of climatic conditions. In addition, the limitations of the UZ model are discussed in Section 8.11.
Formative flow in bedrock canyons
Venditti, J. G.; Kwoll, E.; Rennie, C. D.; Church, M. A.
2017-12-01
In alluvial channels, it is widely accepted that river channel configuration is set by a formative flow that represents a balance between the magnitude and frequency of flood flows. The formative flow is often considered to be one that is just capable of filling a river channel to the top of its banks. Flows much above this formative flow are thought to cause substantial sediment transport and rearrange the channel morphology to accommodate the larger flow. This idea has recently been extended to semi-alluvial channels where it has been shown that even with bedrock exposed, the flows rarely exceed that required to entrain the local sediment cover. What constitutes a formative flow in a bedrock canyon is not clear. By definition, canyons have rock walls and are typically incised vertically, removing the possibility of the walls being overtopped, as can occur in an alluvial channel at high flows. Canyons are laterally constrained, have deep scour pools and often have width to maximum depth ratios approaching 1, an order of magnitude lower than alluvial channels. In many canyons, there are a sequence of irregularly spaced scour pools. The bed may have intermittent or seasonal sediment cover, but during flood flows the sediment bed is entrained leaving a bare bedrock channel. It has been suggested that canyons cut into weak, well-jointed rock may adjust their morphology to the threshold for block plucking because the rock bed is labile during exceptionally large magnitude flows. However, this hypothesis does not apply to canyons cut into massive crystalline rock where abrasion is the dominant erosion process. Here, we argue that bedrock canyon morphology is adjusted to a characteristic flow structure developed in bedrock canyons. We show that the deeply scoured canyon floor is adjusted to a velocity inversion that is present at low flows, but gets stronger at high flows. The effect is to increase boundary shear stresses along the scour pool that forms in constricted
Dynamics of swirling jet flows
Energy Technology Data Exchange (ETDEWEB)
Ivanic, T.; Foucault, E.; Pecheux, J. [Laboratoire d' Etudes Aerodynamiques (L.E.A. CNRS UMR 6609), Boulevard Marie et Pierre Curie, Teleport 2, BP 30179, 86960, Futuroscope Chasseneuil Cedex (France)
2003-10-01
Experimental investigations of near-field structure of coaxial flows are presented for four different configurations: coaxial jets without rotation (reference case), outer flow rotating only (OFRO), inner-jet rotating only (IJRO) and corotating jets (CRJ). The investigations are performed in a cylindrical water tunnel, with an independent rotation of two coaxial flows. Laser tomography is used to document the flow field, and photographs are shown for different configurations. Time mean velocity profiles obtained by PIV, with and without swirl, are also presented. The dynamics of the swirling jets in the initial region (i.e. near the exit of the jets) is described. The effects of azimuthal velocity and axial velocity ratio variations on flow dynamics are examined. The appearance and growth of the first instabilities are presented and compared with some theoretical results, as is the influence of the rotation (inner or outer) on the dominating structures. (orig.)
Quantifying global international migration flows.
Abel, Guy J; Sander, Nikola
2014-03-28
Widely available data on the number of people living outside of their country of birth do not adequately capture contemporary intensities and patterns of global migration flows. We present data on bilateral flows between 196 countries from 1990 through 2010 that provide a comprehensive view of international migration flows. Our data suggest a stable intensity of global 5-year migration flows at ~0.6% of world population since 1995. In addition, the results aid the interpretation of trends and patterns of migration flows to and from individual countries by placing them in a regional or global context. We estimate the largest movements to occur between South and West Asia, from Latin to North America, and within Africa.
Entrained Flow Gasification of Biomass
DEFF Research Database (Denmark)
Qin, Ke
The present Ph. D. thesis describes experimental and modeling investigations on entrained flow gasification of biomass and an experimental investigation on entrained flow cogasification of biomass and coal. A review of the current knowledge of biomass entrained flow gasification is presented....... Biomass gasification experiments were performed in a laboratory-scale atmospheric pressure entrained flow reactor with the aim to investigate the effects of operating parameters and biomass types on syngas products. A wide range of operating parameters was involved: reactor temperature, steam/carbon ratio......, excess air ratio, oxygen concentration, feeder gas flow, and residence time. Wood, straw, and lignin were used as biomass fuels. In general, the carbon conversion was higher than 90 % in the biomass gasification experiments conducted at high temperatures (> 1200 °C). The biomass carbon...
Air flow around suspended cables
Directory of Open Access Journals (Sweden)
Gołębiowska Irena
2017-01-01
Full Text Available The impact of wind on construction structures is essential issue in design and operation. In particular, the wind can cause the dengerous vibrations of slender structures with low rigidity, eg. vibrations of cables of suspension and cable-stayed bridges or high voltage transmision lines, thus understanding of wind flow around such constructions is significant. In the paper the results of the analysis of wind flow around the cables for different Reynolds number is presented. The analysed flow meets the Navier-Stokes and continuity equations. The circle and elipse section of the cable is analysed. The discusion of vorticity, drag and lift coefficients and cases due to different angle of wind flow action is presented. The boundary layer and its infuence on total flow is analysed.
Flowing dusty plasma experiments: generation of flow and measurement techniques
Jaiswal, S.; Bandyopadhyay, P.; Sen, A.
2016-12-01
A variety of experimental techniques for the generation of subsonic/supersonic dust fluid flows and means of measuring such flow velocities are presented. The experiments have been carried out in a \\Pi -shaped dusty plasma experimental device with micron size kaolin/melamine formaldehyde particles embedded in a background of argon plasma created by a direct current glow discharge. A stationary dust cloud is formed over the cathode region by precisely balancing the pumping speed and gas flow rate. A flow of dust particles/fluid is generated by additional gas injection from a single or dual locations or by altering the dust confining potential. The flow velocity is then estimated by three different techniques, namely, by super particle identification code, particle image velocimetry analysis and the excitation of dust acoustic waves. The results obtained from these three different techniques along with their merits and demerits are discussed. An estimation of the neutral drag force responsible for the generation as well as the attenuation of the dust fluid flow is made. These techniques can be usefully employed in laboratory devices to investigate linear and non-linear collective excitations in a flowing dusty plasma.
Flow characteristics around a deformable stenosis under pulsatile flow condition
Choi, Woorak; Park, Jun Hong; Byeon, Hyeokjun; Lee, Sang Joon
2018-01-01
A specific portion of a vulnerable stenosis is deformed periodically under a pulsatile blood flow condition. Detailed analysis of such deformable stenosis is important because stenotic deformation can increase the likelihood of rupture, which may lead to sudden cardiac death or stroke. Various diagnostic indices have been developed for a nondeformable stenosis by using flow characteristics and resultant pressure drop across the stenosis. However, the effects of the stenotic deformation on the flow characteristics remain poorly understood. In this study, the flows around a deformable stenosis model and two different rigid stenosis models were investigated under a pulsatile flow condition. Particle image velocimetry was employed to measure flow structures around the three stenosis models. The deformable stenosis model was deformed to achieve high geometrical slope and height when the flow rate was increased. The deformation of the stenotic shape enhanced jet deflection toward the opposite vessel wall of the stenosis. The jet deflection in the deformable model increased the rate of jet velocity and turbulent kinetic energy (TKE) production as compared with those in the rigid models. The effect of stenotic deformation on the pulsating waveform related with the pressure drop was analyzed using the TKE production rate. The deformable stenosis model exhibited a phase delay of the peak point in the waveform. These results revealed the potential use of pressure drop waveform as a diagnostic index for deformable stenosis.
Computational fluid dynamics applied to flows in an internal combustion engine
Griffin, M. D.; Diwakar, R.; Anderson, J. D., Jr.; Jones, E.
1978-01-01
The reported investigation is a continuation of studies conducted by Diwakar et al. (1976) and Griffin et al. (1976), who reported the first computational fluid dynamic results for the two-dimensional flowfield for all four strokes of a reciprocating internal combustion (IC) engine cycle. An analysis of rectangular and cylindrical three-dimensional engine models is performed. The working fluid is assumed to be inviscid air of constant specific heats. Calculations are carried out of a four-stroke IC engine flowfield wherein detailed finite-rate chemical combustion of a gasoline-air mixture is included. The calculations remain basically inviscid, except that in some instances thermal conduction is included to allow a more realistic model of the localized sparking of the mixture. All the results of the investigation are obtained by means of an explicity time-dependent finite-difference technique, using a high-speed digital computer.
Flow visualization of a low density hypersonic flow field
International Nuclear Information System (INIS)
Masson, B.S.; Jumper, E.J.; Walters, E.; Segalman, T.Y.; Founds, N.D.
1989-01-01
Characteristics of laser induced iodine fluorescence (LIIF) in low density hypersonic flows are being investigated for use as a diagnostic technique. At low pressures, doppler broadening dominates the iodine absorption profile producing a fluorescence signal that is primarily temperature and velocity dependent. From this dependency, a low pressure flow field has the potential to be mapped for its velocity and temperature fields. The theory for relating iodine emission to the velocity and temperature fields of a hypersonic flow is discussed in this paper. Experimental observations are made of a fluorescencing free expansion and qualitatively related to the theory. 7 refs
Transformation of Commercial Flows into Physical Flows of Electricity – Flow Based Method
Directory of Open Access Journals (Sweden)
M. Adamec
2009-01-01
Full Text Available We are witnesses of large – scale electricity transport between European countries under the umbrella of the UCTE organization. This is due to the inabilyof generators to satisfy the growing consumption in some regions. In this content, we distinguish between two types of flow. The first type is physical flow, which causes costs in the transmission grid, whilst the second type is commercial flow, which provides revenues for the market participants. The old methods for allocating transfer capacity fail to take this duality into account. The old methods that allocate transmission border capacity to “virtual” commercial flows which, in fact, will not flow over this border, do not lead to optimal allocation. Some flows are uselessly rejected and conversely, some accepted flows can cause congestion on another border. The Flow Based Allocation method (FBA is a method which aims to solve this problem.Another goal of FBA is to ensure sustainable development of expansion of transmission capacity. Transmission capacity is important, because it represents a way to establish better transmission system stability, and it provides a distribution channel for electricity to customers abroad. For optimal development, it is necessary to ensure the right division of revenue allocation among the market participants.This paper contains a brief description of the FBA method. Problems of revenue maximization and optimal revenue distribution are mentioned.
Iverson, R.M.
1997-01-01
Recent advances in theory and experimentation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a comprehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoretical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining static; both can deform in a slow, tranquil mode characterized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompressible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (measured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibrational energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ???10 m3 of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris behind surge fronts is nearly liquefied by high pore pressure, which persists owing to the great compressibility and moderate
Simulation of Multistage Turbine Flows
Celestina, M. L.; Mulac, R. A.; Adamczyk, J. J.
1985-01-01
The numerical simulation of turbine flows serves to enhance the understanding of the flow phenomena within multistage turbomachinery components. The direct benefit of this activity is improved modeling capability, which can be used to improve component efficiency and durability. A hierarchy of equations was formulated to assess the difficulty in analyzing the flow field within multistage turbomachinery components. The Navier-Stokes equations provides the most complete description. The simplest description is given by a set of equations that govern the quasi-one-dimensional flow. The number of unknowns to be solved for increases monotonically above the number of equations. The development of the additional set of equations needed to mathematically close the system of equations forms the closure problem associated with that level of description. For the Navier-Stokes equation there is no closure problem. For the quasi-one-dimensional equation set random flow fluctuations, unsteady fluctuations, nonaxisymmetric flow variations, and hub-to-shroud variations on the quasi-one-dimensional flow must be accounted for.
Inertial objects in complex flows
Syed, Rayhan; Ho, George; Cavas, Samuel; Bao, Jialun; Yecko, Philip
2017-11-01
Chaotic Advection and Finite Time Lyapunov Exponents both describe stirring and transport in complex and time-dependent flows, but FTLE analysis has been largely limited to either purely kinematic flow models or high Reynolds number flow field data. The neglect of dynamic effects in FTLE and Lagrangian Coherent Structure studies has stymied detailed information about the role of pressure, Coriolis effects and object inertia. We present results of laboratory and numerical experiments on time-dependent and multi-gyre Stokes flows. In the lab, a time-dependent effectively two-dimensional low Re flow is used to distinguish transport properties of passive tracer from those of small paramagnetic spheres. Companion results of FTLE calculations for inertial particles in a time-dependent multi-gyre flow are presented, illustrating the critical roles of density, Stokes number and Coriolis forces on their transport. Results of Direct Numerical Simulations of fully resolved inertial objects (spheroids) immersed in a three dimensional (ABC) flow show the role of shape and finite size in inertial transport at small finite Re. We acknowledge support of NSF DMS-1418956.
Lectures on mean curvature flows
Zhu, Xi-Ping
2002-01-01
"Mean curvature flow" is a term that is used to describe the evolution of a hypersurface whose normal velocity is given by the mean curvature. In the simplest case of a convex closed curve on the plane, the properties of the mean curvature flow are described by Gage-Hamilton's theorem. This theorem states that under the mean curvature flow, the curve collapses to a point, and if the flow is diluted so that the enclosed area equals \\pi, the curve tends to the unit circle. In this book, the author gives a comprehensive account of fundamental results on singularities and the asymptotic behavior of mean curvature flows in higher dimensions. Among other topics, he considers in detail Huisken's theorem (a generalization of Gage-Hamilton's theorem to higher dimension), evolution of non-convex curves and hypersurfaces, and the classification of singularities of the mean curvature flow. Because of the importance of the mean curvature flow and its numerous applications in differential geometry and partial differential ...
PIE Nacelle Flow Analysis and TCA Inlet Flow Quality Assessment
Shieh, C. F.; Arslan, Alan; Sundaran, P.; Kim, Suk; Won, Mark J.
1999-01-01
This presentation includes three topics: (1) Analysis of isolated boattail drag; (2) Computation of Technology Concept Airplane (TCA)-installed nacelle effects on aerodynamic performance; and (3) Assessment of TCA inlet flow quality.
Ke, Xinyou; Prahl, Joseph M.; Alexander, J. Iwan D.; Savinell, Robert F.
2016-01-01
In this work, a two-dimensional mathematical model is developed to study the flow patterns and volumetric flow penetrations in the flow channel over the porous electrode layered system in vanadium flow battery with serpentine flow field design. The flow distributions at the interface between the flow channel and porous electrode are examined. It is found that the non-linear pressure distributions can distinguish the interface flow distributions under the ideal plug flow and ideal parabolic fl...
Statistical downscaling of river flows
Tisseuil, Clement; Vrac, Mathieu; Lek, Sovan; Wade, Andrew J.
2010-05-01
SummaryAn extensive statistical 'downscaling' study is done to relate large-scale climate information from a general circulation model (GCM) to local-scale river flows in SW France for 51 gauging stations ranging from nival (snow-dominated) to pluvial (rainfall-dominated) river-systems. This study helps to select the appropriate statistical method at a given spatial and temporal scale to downscale hydrology for future climate change impact assessment of hydrological resources. The four proposed statistical downscaling models use large-scale predictors (derived from climate model outputs or reanalysis data) that characterize precipitation and evaporation processes in the hydrological cycle to estimate summary flow statistics. The four statistical models used are generalized linear (GLM) and additive (GAM) models, aggregated boosted trees (ABT) and multi-layer perceptron neural networks (ANN). These four models were each applied at two different spatial scales, namely at that of a single flow-gauging station (local downscaling) and that of a group of flow-gauging stations having the same hydrological behaviour (regional downscaling). For each statistical model and each spatial resolution, three temporal resolutions were considered, namely the daily mean flows, the summary statistics of fortnightly flows and a daily 'integrated approach'. The results show that flow sensitivity to atmospheric factors is significantly different between nival and pluvial hydrological systems which are mainly influenced, respectively, by shortwave solar radiations and atmospheric temperature. The non-linear models (i.e. GAM, ABT and ANN) performed better than the linear GLM when simulating fortnightly flow percentiles. The aggregated boosted trees method showed higher and less variable R2 values to downscale the hydrological variability in both nival and pluvial regimes. Based on GCM cnrm-cm3 and scenarios A2 and A1B, future relative changes of fortnightly median flows were projected
Flow structures in cerebral aneurysms
Gambaruto, Alberto M; João, Ana
2012-01-01
Mechanical properties of blood flow are commonly correlated to a wide range of cardiovascular diseases. In this work means to describe and characterise the flow field in the free-slip and no-slip domains are discussed in the context of cerebral aneurysms, reconstructed from in-vivo medical imaging. The approaches rely on a Taylor series expansion of the velocity field to first order terms that leads to a system of ODEs, the solution to which locally describes the motion of the flow. On perfor...
Flow boiling in expanding microchannels
Alam, Tamanna
2017-01-01
This Brief presents an up to date summary of details of the flow boiling heat transfer, pressure drop and instability characteristics; two phase flow patterns of expanding microchannels. Results obtained from the different expanding microscale geometries are presented for comparison and addition to that, comparison with literatures is also performed. Finally, parametric studies are performed and presented in the brief. The findings from this study could help in understanding the complex microscale flow boiling behavior and aid in the design and implementation of reliable compact heat sinks for practical applications.
Synthetic Aperture Vector Flow Imaging
DEFF Research Database (Denmark)
Oddershede, Niels
2008-01-01
of the thesis considers a method for estimating the two-dimensional velocity vector within the image plane. This method, called synthetic aperture vector flow imaging, is first shortly reviewed. The main contribution of this work is partly an analysis of the method with respect to focusing effects, motion...... estimation. The method can be used for increasing the frame rate of color flow maps or alternatively for a new imaging modality entitled quadroplex imaging, featuring a color flow map and two independent spectrograms at a high frame rate. The second is an alternative method for ultrasonic vector velocity...
Information Flow Analysis for VHDL
DEFF Research Database (Denmark)
Tolstrup, Terkel Kristian; Nielson, Flemming; Nielson, Hanne Riis
2005-01-01
We describe a fragment of the hardware description language VHDL that is suitable for implementing the Advanced Encryption Standard algorithm. We then define an Information Flow analysis as required by the international standard Common Criteria. The goal of the analysis is to identify the entire...... information flow through the VHDL program. The result of the analysis is presented as a non-transitive directed graph that connects those nodes (representing either variables or signals) where an information flow might occur. We compare our approach to that of Kemmerer and conclude that our approach yields...
POSIVA groundwater flow measuring techniques
International Nuclear Information System (INIS)
Oehberg, A.; Rouhiainen, P.
2000-08-01
Posiva Oy has carried out site characterisation for the final disposal of spent nuclear fuel in Finland since 1987. To meet the demanding needs to measure the hydraulic parameters in bedrock Posiva launched development of new flowmeter techniques including measuring methods and equipment in co-operation with PRG-Tec Oy. The techniques have been tested and used in the ongoing site investigations in Finland, in the underground Hard Rock Laboratory (HRL) at Aespoe in Sweden and in URL in Canada. The new methods are called difference flow and transverse flow methods. The difference flow method includes two modes, normal and detailed flow logging methods. In the normal mode the flow rate measurement is based on thermal pulse and thermal dilution methods, in the detailed logging mode only on thermal dilution method. The measuring ranges for flow rate with thermal pulse and dilution methods are 0.1-10 ml/min and 2-5000 ml/min, respectively. The difference flow method(normal mode) for small flows (0.1-10 ml/min) is based on measuring the pulse transit time and direction of a thermal pulse in the sensor. For high flows (2-5000 ml/min) the method is based on thermal dilution rate of a sensor. Direction is measured with monitoring thermistors. Inflow or outflow in the test interval is created due to natural or by pumping induced differences between heads in the borehole water and groundwater around the borehole. The single point resistance (and the temperature of borehole water) measurement is carried out simultaneously with the difference flow measurements, both in normal and detailed flow logging modes, while the tool is moving. The result is utilised for checking the exact depth of the tool. As the result a continuous log is obtained from which single fractures can be detected. The transverse flowmeter is able to measure the groundwater flow across a borehole. A special packer system guides the flow through the flow sensors. Four inflatable seals between conventional
Content dependent information flow control
DEFF Research Database (Denmark)
Nielson, Hanne Riis; Nielson, Flemming
2017-01-01
a combined Hoare logic and type system for enforcing content dependent information flow policies dealing with both integrity and confidentiality. We establish the soundness of the Hoare logic with respect to an instrumented operational semantics and illustrate the development on a running example. We also......Information flow control extends access control by not only regulating who is allowed to access what data but also the subsequent use of the data. Applications within communications systems require such information flow control to be dependent on the actual contents of the data. We develop...
Subcubic Control Flow Analysis Algorithms
DEFF Research Database (Denmark)
Midtgaard, Jan; Van Horn, David
We give the first direct subcubic algorithm for performing control flow analysis of higher-order functional programs. Despite the long held belief that inclusion-based flow analysis could not surpass the ``cubic bottleneck, '' we apply known set compression techniques to obtain an algorithm...... that runs in time O(n^3/log n) on a unit cost random-access memory model machine. Moreover, we refine the initial flow analysis into two more precise analyses incorporating notions of reachability. We give subcubic algorithms for these more precise analyses and relate them to an existing analysis from...
A New Two-phase Flow Model Applied to the 2007 Crater Lake Break-out Lahar, Mt. Ruapehu, New Zealand
Sheridan, M. F.; Cordoba, G.; Pitman, E.; Cronin, S. J.; Procter, J.
2010-12-01
The 2007 Crater Lake break-out lahar, Mt. Ruapehu, New Zealand, is a complex but well-characterized natural debris flow that follows an intricate course over an array of topographic features (see Manville et al., this conference). Detailed digital terrain data (DEM) and accurate flow characterization allow us to test our computational model with an unusually high level of control for such a large natural flood wave. The new two-phase flow code is imbedded within the TITAN2D framework (Patra et al. 2005) that is widely used in hazard assessment for both dry (granular) and wet (debris flow) flows (Murcia et al., 2010). Because TITAN2D is actually valid for dry flows (avalanches) we developed a new two-phase model based on balance laws for mass and momentum for each phase. The granular material is assumed to obey a Coulomb constitutive relation and the fluid is assumed to be inviscid. The Darcy-Weisbach formulation is used to account for bed friction, and a phenomenological drag coefficient mediates the momentum exchange between phases. The resulting system of 6 partial differential equations are depth averaged and correspond to the Savage and Hutter model in the limit of no fluid, and to the typical shallow water solutions (Ortiz, et al., 2005) for pure water. This model is capable of simulating particle volumetric fractions as dilute as 0.001 and as concentrated as 0.55. To confirm the usefulness of the new code for complex flows we used data from four observation stations at Ruapehu located at runout distances of 2 km, 5 km, 7 km and 9 km. The specific flow data that we compare with the model outcomes include: 1) arrival time of the flood front, 2) maximum flood depth, and 3) flow velocity. The computed values for these flow characteristics are all within about ± 10% of the observed figures. References: Manville, V., et al., 2010, Anatomy of a basin break-out flood: The 2007 Crater Lake break-out lahar, Mt. Ruapehu, New Zealand, this conference. Murcia, H
Optimal Power Flow Control by Rotary Power Flow Controller
Directory of Open Access Journals (Sweden)
KAZEMI, A.
2011-05-01
Full Text Available This paper presents a new power flow model for rotary power flow controller (RPFC. RPFC injects a series voltage into the transmission line and provides series compensation and phase shifting simultaneously. Therefore, it is able to control the transmission line impedance and the active power flow through it. An RPFC is composed mainly of two rotary phase shifting transformers (RPST and two conventional (series and shunt transformers. Structurally, an RPST consists of two windings (stator and rotor windings. The rotor windings of the two RPSTs are connected in parallel and their stator windings are in series. The injected voltage is proportional to the vector sum of the stator voltages and so its amplitude and angle are affected by the rotor position of the two RPSTs. This paper, describes the steady state operation and single-phase equivalent circuit of the RPFC. Also in this paper, a new power flow model, based on power injection model of flexible ac transmission system (FACTS controllers, suitable for the power flow analysis is introduced. Proposed model is used to solve optimal power flow (OPF problem in IEEE standard test systems incorporating RPFC and the optimal settings and location of the RPFC is determined.
Redesigning flow injection after 40 years of development: Flow programming.
Ruzicka, Jaromir Jarda
2018-01-01
Automation of reagent based assays, by means of Flow Injection (FI), is based on sample processing, in which a sample flows continuously towards and through a detector for quantification of the target analyte. The Achilles heel of this methodology, the legacy of Auto Analyzer®, is continuous reagent consumption, and continuous generation of chemical waste. However, flow programming, assisted by recent advances in precise pumping, combined with the lab-on-valve technique, allows the FI manifold to be designed around a single confluence point through which sample and reagents are sequentially directed by means of a series of flow reversals. This approach results in sample/reagent mixing analogous to the traditional FI, reduces sample and reagent consumption, and uses the stop flow technique for enhancement of the yield of chemical reactions. The feasibility of programmable Flow Injection (pFI) is documented by example of commonly used spectrophotometric assays of, phosphate, nitrate, nitrite and glucose. Experimental details and additional information are available in online tutorial http://www.flowinjectiontutorial.com/. Copyright © 2017 Elsevier B.V. All rights reserved.
Bouley, Simon; François, Benjamin; Roger, Michel; Posson, Hélène; Moreau, Stéphane
2017-09-01
The present work deals with the analytical modeling of two aspects of outlet guide vane aeroacoustics in axial-flow fan and compressor rotor-stator stages. The first addressed mechanism is the downstream transmission of rotor noise through the outlet guide vanes, the second one is the sound generation by the impingement of the rotor wakes on the vanes. The elementary prescribed excitation of the stator is an acoustic wave in the first case and a hydrodynamic gust in the second case. The solution for the response of the stator is derived using the same unified approach in both cases, within the scope of a linearized and compressible inviscid theory. It is provided by a mode-matching technique: modal expressions are written in the various sub-domains upstream and downstream of the stator as well as inside the inter-vane channels, and matched according to the conservation laws of fluid dynamics. This quite simple approach is uniformly valid in the whole range of subsonic Mach numbers and frequencies. It is presented for a two-dimensional rectilinear-cascade of zero-staggered flat-plate vanes and completed by the implementation of a Kutta condition. It is then validated in sound generation and transmission test cases by comparing with a previously reported model based on the Wiener-Hopf technique and with reference numerical simulations. Finally it is used to analyze the tonal rotor-stator interaction noise in a typical low-speed fan architecture. The interest of the mode-matching technique is that it could be easily transposed to a three-dimensional annular cascade in cylindrical coordinates in a future work. This makes it an attractive alternative to the classical strip-theory approach.
Interregional migration flows in Indonesia
Wajdi, N.; van Wissen, L.J.G.; Mulder, C.H.
2015-01-01
Population Census and Intercensal Population Survey data permit description of the origin–destination patterns that characterize interregional migration flows in Indonesia. Application of the framework of population redistribution proposed by Long (1985) results in indications of over-urbanization,
International Nuclear Information System (INIS)
Boure, J.A.
1974-12-01
Two-phase flow instabilities are classified according to three criteria: the static or dynamic nature of the phenomenon, the necessity or not of a triggering phenomenon, and the pure or compound character of the phenomenon. Tables give the elementary instability phenomena, and the practical types of instability. Flow oscillations (or dynamic instabilities) share a number of characteristics which are dealt with, they are caused by the dynamic interactions between the flow parameters (flow rate, density, pressure, enthalpy and their distributions). Oscillation types are discussed: pure oscillations are density wave oscillations, acoustic oscillations may also occur, various compound oscillations involve either the density wave or the acoustic wave mechanism, interacting with some of the boundary conditions in the device. The analysis of slow oscillations has been made either by means of a simplified model (prediction of the thresholds) or of computer codes. Numerous computer codes are available [fr
Dust in flowing magnetized plasma
International Nuclear Information System (INIS)
Pandey, Birendra P.; Samarian, Alex A.; Vladimirov, Sergey V.
2009-01-01
Plasma flows occur in almost every laboratory device and interactions of flowing plasmas with near-wall impurities and/or dust significantly affects the efficiency and lifetime of such devices. The charged dust inside the magnetized flowing plasma moves primarily under the influence of the plasma drag and electric forces. Here, the charge on the dust, plasma potential, and plasma density are calculated self-consistently. The electrons are assumed non-Boltzmannian and the effect of electron magnetization and electron-atom collisions on the dust charge is calculated in a self-consistent fashion. For various plasma magnetization parameters viz. the ratio of the electron and ion cyclotron frequencies to their respective collision frequencies, plasma-atom and ionization frequencies, the evolution of the plasma potential and density in the flow region is investigated. The variation of the dust charge profile is shown to be a sensitive function of plasma parameters. (author)
2007 Estimated International Energy Flows
Energy Technology Data Exchange (ETDEWEB)
Smith, C A; Belles, R D; Simon, A J
2011-03-10
An energy flow chart or 'atlas' for 136 countries has been constructed from data maintained by the International Energy Agency (IEA) and estimates of energy use patterns for the year 2007. Approximately 490 exajoules (460 quadrillion BTU) of primary energy are used in aggregate by these countries each year. While the basic structure of the energy system is consistent from country to country, patterns of resource use and consumption vary. Energy can be visualized as it flows from resources (i.e. coal, petroleum, natural gas) through transformations such as electricity generation to end uses (i.e. residential, commercial, industrial, transportation). These flow patterns are visualized in this atlas of 136 country-level energy flow charts.
Rainfall and Detention Basin Flows
U.S. Environmental Protection Agency — Storm event data and flow rates in/out pre-post device installation. This dataset is associated with the following publication: Hawley, R., J. Goodrich, N. Korth, C....
Modeling Diesel Engine Injector Flows
National Research Council Canada - National Science Library
Heister, S
2001-01-01
Models have been developed to assess flow fields inside diesel injector orifice passages in order to increase our understanding of the spray formation process which governs performance and emissions in these engines...
Low-Order Modeling of Dynamic Stall on Airfoils in Incompressible Flow
Narsipur, Shreyas
Unsteady aerodynamics has been a topic of research since the late 1930's and has increased in popularity among researchers studying dynamic stall in helicopters, insect/bird flight, micro air vehicles, wind-turbine aerodynamics, and ow-energy harvesting devices. Several experimental and computational studies have helped researchers gain a good understanding of the unsteady ow phenomena, but have proved to be expensive and time-intensive for rapid design and analysis purposes. Since the early 1970's, the push to develop low-order models to solve unsteady ow problems has resulted in several semi-empirical models capable of effectively analyzing unsteady aerodynamics in a fraction of the time required by high-order methods. However, due to the various complexities associated with time-dependent flows, several empirical constants and curve fits derived from existing experimental and computational results are required by the semi-empirical models to be an effective analysis tool. The aim of the current work is to develop a low-order model capable of simulating incompressible dynamic-stall type ow problems with a focus on accurately modeling the unsteady ow physics with the aim of reducing empirical dependencies. The lumped-vortex-element (LVE) algorithm is used as the baseline unsteady inviscid model to which augmentations are applied to model unsteady viscous effects. The current research is divided into two phases. The first phase focused on augmentations aimed at modeling pure unsteady trailing-edge boundary-layer separation and stall without leading-edge vortex (LEV) formation. The second phase is targeted at including LEV shedding capabilities to the LVE algorithm and combining with the trailing-edge separation model from phase one to realize a holistic, optimized, and robust low-order dynamic stall model. In phase one, initial augmentations to theory were focused on modeling the effects of steady trailing-edge separation by implementing a non-linear decambering
Information Flow for Timed Automata
DEFF Research Database (Denmark)
Nielson, Flemming; Nielson, Hanne Riis; Vasilikos, Panagiotis
2017-01-01
One of the key demands of cyberphysical systems is that they meet their safety goals. Timed Automata has established itself as a formalism for modelling and analysing the real-time safety aspects of cyberphysical systems. Increasingly it is also demanded that cyberphysical systems meet a number o...... of security goals for confidentiality and integrity. Information Flow Control is an approach to ensuring that there are no flows of information that violate the stated security policy....
Symmetric instability of monsoon flows
Krishnakumar, V.; Lau, K.-M.
2011-01-01
Using a zonally symmetric multi-level moist linear model, we have examined the possibility of symmetric instability in the monsoon region. Stability analyses with a zonally symmetric model using monthly ECMWF (Jan – Dec) zonal basic flows revealed both unstable as well as neutral modes. In the absence of cumulus heating, the linear stability of the monsoon flow changes dramatically with the emergence of many unstable modes in the month of May and lasting through August; whereas with the inclu...