bluuebunny/crossref_metadata_2025_split huggingface dataset:
Collocated discrete least‐squares (CDLS) meshless method: error estimate and adaptive refinement
Authors: Afshar M. H. , Lashckarbolok M. 
Published: February 2008

AbstractInt. J. Numer. Meth. Fluids (in press) Published online in Wiley InterScience (www.interscience.wiley.com) (DOI: 10.1002/fld.1571)The authors apologizes the respected readers of the Int. J. Numer. Meth. Fluids for the unnoticed error in the formula (35) in Page 7 of the paper. The correct formula is
Development and application of a parallel multigrid solver for the simulation of spreading droplets
Authors: Gaskell P. H. , Jimack P. K. , Koh Y.‐Y. , Thompson H. M. 
Published: February 2008

AbstractWe consider the parallel application of an efficient solver developed for the accurate solution of a range of droplet spreading flows modelled as a coupled set of nonlinear lubrication equations. The underlying numerical scheme is based upon a second‐order finite difference discretization in space and a second‐order, fully implicit, adaptive scheme in time. At each time step, this leads to the need to solve a large system of nonlinear algebraic equations, for which the full approximation storage multigrid algorithm is employed. The motion of the contact line between the three phases (liquid, air and the solid substrate) is based upon the assumption of a thin precursor film, with a corresponding disjoining pressure term in the governing equations. It is the inclusion of this precursor film in the model that motivates the need for a parallel solution method. This is because the thickness of such a film must be very small in order to yield realistic predictions, while the finite difference grid must be correspondingly fine in order to obtain accurate numerical solutions. Results are presented which demonstrate that the parallel implementation is sufficiently efficient and robust to allow reliable numerical solutions to be obtained for a level of mesh resolution that is an order of magnitude finer than is possible using a single processor. Copyright © 2008 John Wiley & Sons, Ltd.
A symmetric formulation for flux‐limited convection schemes
Authors: Waterson N. P. 
Published: February 2008

AbstractThe present paper introduces a new limiter formulation for the definition of bounded higher‐order convection schemes within a finite‐volume context. The new formulation emphasizes the symmetry property and brings into clearer view certain types of solution behaviour, in particular strong positive solution curvature. The new formulation can be shown graphically, in a diagram similar to the well‐known Sweby diagram, and the various boundedness criteria in current use, in particular the total‐variation diminishing (TVD) and positivity conditions, can be shown as regions in the new diagram. The formulation allows the definition of smooth limiters with simple and flexible functional forms, of which some example classes are given (along with the transformed versions of some existing limiters). The smooth classes can be extended to maintain positive solution behaviour on non‐uniform grids in a simple and natural manner. Copyright © 2008 John Wiley & Sons, Ltd.
High‐order methods and mesh adaptation for Euler equations
Authors: Alauzet F. 
Published: February 2008

AbstractIn this paper, we point out a novel contribution of mesh adaptation to high‐order methods for stationary and time‐dependent problems. From theoretical results, we exhibit that mesh adaptation, based on an adjoint‐free method, achieves a global second‐order mesh convergence for numerical solutions with discontinuities in Lp norm. To attain this result, it is mandatory to combine together all mesh adaptive methods developed in the previous work. This theoretical result is validated on 2D and 3D examples for stationary and time‐dependent simulations. Copyright © 2008 John Wiley & Sons, Ltd.
On the use of orthogonal functions in fluid‐dynamic gradient‐based optimization
Authors: Catalano L. A. , Dadone A. , Daloiso V. S. E. 
Published: February 2008

AbstractThis paper proposes a method to derive a set of symmetrical and antisymmetric orthogonal shape functions, which can be efficiently used in fluid‐dynamic design optimization. The inverse design of an airfoil in inviscid transonic flow conditions is proposed to demonstrate that a gradient‐based optimization using orthogonal profiles is 6–10 times faster than the same procedure using non‐orthogonal interpolation functions. Copyright © 2008 John Wiley & Sons, Ltd.
Large‐eddy simulation of the flow in a low‐speed centrifugal compressor
Authors: Guleren K. M. , Turan A. , Pinarbasi A. 
Published: February 2008

AbstractThe results of a series of numerical simulations for the NASA low‐speed centrifugal compressor are presented. Large‐eddy simulation (LES) is carried out together with the most commonly used Reynolds‐averaged Navier–Stokes (RANS) models, including the mixing length, k–ε and k–ω models. Predictions are compared with the available experimental data. It is seen that quantitative predictions of LES are better than those of RANS models for the tip jet and wake regions. LES, unlike these RANS models and the past computational fluid dynamics predictions, shows separation near the casing starting around the halfway of the impeller and reveals a vortex bubble close the impeller exit/casing corner. The tip leakage flow, which is the main characteristic of an unshrouded compressor, is investigated using the probability density function (PDF) and the power spectral density (PSD) of the instantaneous velocity values. The skewness and flatness calculated from the PDF profiles show that the unsteady flow in the tip wake region is less‐intermittent compared with the flow in the tip jet region. The PSD analysis shows that the turbulent energy transfer rate from the larger scales to the smaller scales and the frequency range where the inertial region is valid increase in the tip wake region. Copyright © 2008 John Wiley & Sons, Ltd.
Numerical simulation of film cooling effectiveness on a flat plate
Authors: Kanani Homayoon , Shams Mehrzad , Ebrahimi Reza , Ahmadian Taher 
Published: February 2008

AbstractNumerical simulation has been conducted to study film cooling effectiveness on a flat plate. Three‐dimensional geometry was generated and the effects of blowing ratio and geometrical shape were studied. A cylindrical round, simple angle (CYSA) and laterally diffused, simple angle (LDSA) hole with a streamwise angle of 30° and spanwise angle of 0° were used. Hole length to diameter ratio (L/D=4) is constant for all geometries. Also the diameter of film cooling hole for different cooling holes at the entrance surface (D=10 mm) is constant. The blowing ratio ranges from 0.5 to 1.67, and the mainstream Reynolds number based on the mainstream velocity and hole diameter (ReD) was 8563. Both local and lateral averaged values are presented. Results have a good correspondence with experimental data obtained by Yuen and Martinez‐Botas (Int. J. Heat Mass Transfer 2003; 46:221–235). The simulation results show that cooling hole shape affects film cooling effectiveness significantly. The LDSA hole decreases the momentum of jet flow at the exit area of the hole and avoids lift‐off phenomenon. Counter‐rotating vortex formed downstream of the hole is weaker for the LDSA hole and secondary flow is not powerful enough to disturb the jet flow structure next to the wall. Also the results show that the LDSA hole has a better lateral coverage due to the diffused shape of the hole and has a higher effectiveness value in a wider region on the wall. Copyright © 2008 John Wiley & Sons, Ltd.
A large eddy simulation of an airfoil turbulent wake subjected to streamwise curvature
Authors: Farsimadan E. , Mokhtarzadeh‐Dehghan M. R. 
Published: February 2008

AbstractThis paper presents large eddy simulations (LES) of the curved wake of an airfoil. The wake was generated by placing a NACA0012 airfoil in a uniform stream of air, which is then subjected to an abrupt 90° curvature created by a duct bend. The trailing edge of the airfoil is one chord length upstream of the bend entry. The duct cross‐section measures 457 mm × 457 mm, and the bend has radius to height ratio of 1.17. The flow Reynolds number (1.02 × 105) is based on a mainstream velocity of 10 m/s and airfoil chord length 0.15 m. The sub‐grid scale models employed are the classical Smagorinsky, its dynamic variant and the dynamic kinetic energy transport. The performance of LES in depicting the experimental flow is assessed and compared with results predicted by the Reynolds stress model (RSM). The results show the advantages of LES over Reynolds‐averaged Navier–Stokes methods in predicting convex wall separation in strongly curved ducts on relatively coarse grids. Results from LES on a considerably finer near‐wall‐resolved grid lead to much improved comparison with the experimental data in the near wake, bettering predictions by RSM and LES on the coarse grid. Copyright © 2008 John Wiley & Sons, Ltd.
Computational framework for the regularized 20‐moment equations for non‐equilibrium gas flows
Authors: Mizzi S. , Gu X. J. , Emerson D. R. , Barber R. W. , Reese J. M. 
Published: February 2008

AbstractThis paper presents a framework for solving the regularized 20‐moment equations consisting of a set of transport‐like governing equations, the required constitutive closure, re‐casting of the equations in second‐order partial derivative form and derivation of additional wall boundary conditions. Couette flow results reveal that good agreement occurs between the 20‐moment equations and direct simulation Monte Carlo data. Copyright © 2008 John Wiley & Sons, Ltd.
Invariant numerical methods
Authors: Dawes A. S. 
Published: February 2008

AbstractThe discretization of partial differential equations can produce numerical errors, and in particular symmetry errors. Typically the symmetry is fitted into the numerical method based on the relative merits of physically aligning the mesh, solving in the natural coordinate frame or modifying the truncation error. In this paper we will consider two alternative approaches developed from capturing the underlying symmetries, inherent in the partial differential equations, in the numerical method. The invariant numerical methods are developed from the extension of Lie group theory to discretized equations using discrete invariants and the technique of invariantization for the heat equation. Their performances against more traditional schemes will be presented. © British Crown Copyright 2008/MOD. Reproduced with permission. Published by John Wiley & Sons, Ltd.
Two remarks on a paper by Sani et al.
Authors: Rempfer Dietmar 
Published: February 2008

AbstractIn Sani et al. (Int. J. Numer. Meth. Fluids 2006; 50:673–682), the authors claim to provide a proof of well‐posedness for certain formulations of the Navier–Stokes equations for incompressible flow. We consider the proof of their main Theorem 1 incomplete, and point out some inconsistencies in the above paper. Copyright © 2008 John Wiley & Sons, Ltd.
A fast and robust fictitious domain method for modelling viscous flows in complex mixers: The example of propellant make‐down
Authors: Coesnon Benjamin , Heniche Mourad , Devals Christophe , Bertrand François , Tanguy Philippe A. 
Published: February 2008

AbstractThis work deals with the development of a fast three‐dimensional numerical strategy for the simulation of viscous fluid flow in complex mixing systems. The proposed method is based on a distributed Lagrange multiplier fictitious domain method and the use of the low‐cost MINI finite element. Contrary to the previous fictitious domain method developed by our group a few years ago, the underlying partial differential equations are solved here in a coupled manner using a consistent penalty technique. The method is discussed in detail and its precision is assessed by means of experimental data in the case of an agitated vessel. A comparison made with our existing fictitious domain method and its decoupled Uzawa‐based solver clearly shows the advantages of resorting to the MINI finite element and fully coupled solution strategy. The new technique is then applied to the simulation of the flow of a Newtonian viscous fluid in a three‐blade planetary mixer in the context of the production of solid propellants. Copyright © 2008 John Wiley & Sons, Ltd.
A conformal Petrov–Galerkin method for convection‐dominated problems
Authors: Delsaute B. , Dupret F. 
Published: February 2008

AbstractIn this paper, we present the ‘conformal Petrov–Galerkin’ (CPG) method in order to solve the 2D convection–diffusion equation on meshes composed of triangular elements. By ‘conformal’ it is meant that the discrete system is obtained from the continuous weak formulation by appropriately selecting different finite‐dimensional subspaces for the shape and test functions without any additional stabilizing term. Our approach is based on searching continuous test functions that provide exact nodal values for a selected class of solutions. This method induces a stabilizing upwinding effect that removes the wiggles obtained with the Galerkin method. Copyright © 2008 John Wiley & Sons, Ltd.
Sliding mesh algorithm for CFD analysis of helicopter rotor–fuselage aerodynamics
Authors: Steijl R. , Barakos G. 
Published: February 2008

AbstractThe study of rotor–fuselage interactional aerodynamics is central to the design and performance analysis of helicopters. However, regardless of its significance, rotor–fuselage aerodynamics has so far been addressed by very few authors. This is mainly due to the difficulties associated with both experimental and computational techniques when such complex configurations, rich in flow physics, are considered. In view of the above, the objective of this study is to develop computational tools suitable for rotor–fuselage engineering analysis based on computational fluid dynamics (CFD).To account for the relative motion between the fuselage and the rotor blades, the concept of sliding meshes is introduced. A sliding surface forms a boundary between a CFD mesh around the fuselage and a rotor‐fixed CFD mesh which rotates to account for the movement of the rotor. The sliding surface allows communication between meshes. Meshes adjacent to the sliding surface do not necessarily have matching nodes or even the same number of cell faces. This poses a problem of interpolation, which should not introduce numerical artefacts in the solution and should have minimal effects on the overall solution quality. As an additional objective, the employed sliding mesh algorithms should have small CPU overhead. The sliding mesh methods developed for this work are demonstrated for both simple and complex cases with emphasis placed on the presentation of the inner workings of the developed algorithms. Copyright © 2008 John Wiley & Sons, Ltd.
Semi‐coupled air/water immersed boundary approach for curvilinear dynamic overset grids with application to ship hydrodynamics
Authors: Huang Juntao , Carrica Pablo M. , Stern Frederick 
Published: February 2008

AbstractFor many problems in ship hydrodynamics, the effects of air flow on the water flow are negligible (the frequently called free surface conditions), but the air flow around the ship is still of interest. A method is presented where the water flow is decoupled from the air solution, but the air flow uses the unsteady water flow as a boundary condition. The authors call this a semi‐coupled air/water flow approach. The method can be divided into two steps. At each time step the free surface water flow is computed first with a single‐phase method assuming constant pressure and zero stress on the interface. The second step is to compute the air flow assuming the free surface as a moving immersed boundary (IB). The IB method developed for Cartesian grids (Annu. Rev. Fluid Mech. 2005; 37:239–261) is extended to curvilinear grids, where no‐slip and continuity conditions are used to enforce velocity and pressure boundary conditions for the air flow. The forcing points close to the IB can be computed and corrected under a sharp interface condition, which makes the computation very stable. The overset implementation is similar to that of the single‐phase solver (Comput. Fluids 2007; 36:1415–1433), with the difference that points in water are set as IB points even if they are fringe points. Pressure–velocity coupling through pressure implicit with splitting of operators or projection methods is used for water computations, and a projection method is used for the air. The method on each fluid is a single‐phase method, thus avoiding ill‐conditioned numerical systems caused by large differences of fluid properties between air and water. The computation is only slightly slower than the single‐phase version, with complete absence of spurious velocity oscillations near the free surface, frequently present in fully coupled approaches. Validations are performed for laminar Couette flow over a wavy boundary by comparing with the analytical solution, and for the surface combatant model David Taylor Model Basin (DTMB) 5512 by comparing with Experimental Fluid Dynamics (EFD) and the results of two‐phase level set computations. Complex flow computations are demonstrated for the ONR Tumblehome DTMB 5613 with superstructure subject to waves and wind, including 6DOF motions and broaching in SS7 irregular waves and wind. Copyright © 2008 John Wiley & Sons, Ltd.
Numerical simulations of viscous flows using a meshless method
Authors: You Changfu , Qiu Yi , Xu Xuchang , Xu Delong 
Published: February 2008

AbstractThis paper uses the element‐free Galerkin (EFG) method to simulate 2D, viscous, incompressible flows. The control equations are discretized with the standard Galerkin method in space and a fractional step finite element scheme in time. Regular background cells are used for the quadrature. Several classical fluid mechanics problems were analyzed including flow in a pipe, flow past a step and flow in a driven cavity. The flow field computed with the EFG method compared well with those calculated using the finite element method (FEM) and finite difference method. The simulations show that although EFG is more expensive computationally than FEM, it is capable of dealing with cases where the nodes are poorly distributed or even overlap with each other; hence, it may be used to resolve remeshing problems in direct numerical simulations. Flows around a cylinder for different Reynolds numbers are also simulated to study the flow patterns for various conditions and the drag and lift forces exerted by the fluid on the cylinder. These forces are calculated by integrating the pressure and shear forces over the cylinder surface. The results show how the drag and lift forces oscillate for high Reynolds numbers. The calculated Strouhal number agrees well with previous results. Copyright © 2008 John Wiley & Sons, Ltd.
Comparative study of potential evapotranspiration and interception evaporation by land cover over Mekong basin
Authors: Zhou M. C. , Ishidaira H. , Takeuchi K. 
Published: February 2008

AbstractPotential evapotranspiration is a key input to hydrological models. Its estimation has often been via the Penman–Monteith (P‐M) equation, most recently in the form of an estimate of reference evapotranspiration (RET) as recommended by FAO‐56. In this article, the Shuttleworth–Wallace (S‐W) model is implemented to estimate the potential evapotranspiration from soil moisture (PET) and the potential evaporation from interception (PET0) directly in a form that recognizes vegetation diversity and temporal development without reference to experimental measurements and without calibration. The threshold values of vegetation parameters are drawn from the literature based on the International Geosphere–Biosphere Programme (IGBP) land cover classification. The spatial and temporal variation of the leaf area index (LAI) of vegetation is derived from the composite National Oceanic and Atmospheric Administration ‐ Advanced Very High Resolution Radiometer (NOAA‐AVHRR) normalized difference vegetation index (NDVI) using a method based on the SiB2 model, and the Climate Research Unit (CRU) database is used to provide the required meteorological data. All these data inputs are publicly and globally available. Consequently, the implementation of the S‐W model developed in this study is applicable at the global scale, an essential requirement if it is to be applied in data‐poor or ungauged large basins.A comparison is made between the FAO‐56 method and the S‐W model when applied to the Mekong River basin for the period 1981–2000. The resulting estimates of RET and PET and their association with vegetation types and LAI are examined over the whole basin both annual and monthly and at five specific points. The effect of NDVI on the PET estimate is further evaluated by replacing the monthly NDVI product with the 10‐day product. Multiple regression relationships between monthly PET, RET, LAI, and climatic variables are explored for categories of vegetation types. The estimated RET is a good climatic index that adequately reflects the temporal change and spatial distribution of climate over the basin, but the PET estimated using the S‐W model not only reflects the change in climate but also the vegetation distribution and the development of vegetation in response to climate. Although good statistical relationships can be established between PET, RET, and/or climatic variables, applying these relationships will likely result in large errors because of the strong non‐linearity and scatter between the PET and the LAI of the vegetation. It is concluded that use of the implementation of the S‐W model described in this study results in a physically sound estimate of PET, which accounts for changing land surface conditions. Copyright © 2008 John Wiley & Sons, Ltd.
Impact of paddy irrigation levels on floods and water use in the Mekong River basin
Authors: Masumoto Takao , Hai Pham Thanh , Shimizu Katsuyuki 
Published: February 2008

AbstractDuring the Asian monsoon, water use is considered to be well integrated because of the sustainable use of the agricultural water supply. From the viewpoint of watershed management, paddy areas help regulate floods by serving as retarding basins (ponds), but they also ensure a rational supply of water resources by taking advantage of natural hydrologic conditions. Paddies commonly serve both agricultural and flood‐control functions in low‐lying areas in Japan, Cambodia, Vietnam, and other Asian countries. We discuss herein the impact of irrigation levels on floods and water use by analyzing typical examples of paddies harmoniously used for agriculture and flood regulation in and around Tonle Sap Lake and its environs in the Mekong River Basin (drainage area, 790 000 km2; river length, 4400 km). Flood storage by the Tonle Sap involves a unique reverse flow from the river into the lake during the flood season. Rice cultivation starts after the floodwater recedes, so floods and agriculture are closely interrelated. A second example involves reservoirs created by dikes in paddy areas that protect the urban areas of Phnom Penh from floods and supply irrigation water. A third example involves the use of colmatage, in which a levee is created and water is led behind the levee from the Mekong and Bassac Rivers as the water levels in the rivers rise. Part of the water stored in this manner during the flood season can be used for rice production during the dry season. We then estimate the volume of flooded water on paddies in order to evaluate the impact of non‐irrigated paddies on floods and water use. We also evaluate the potential to harmonize the role of paddies in managing floodwaters with their agricultural role and propose policies, for Japan and the rest of the world, that could help resolve flooding problems. Copyright © 2008 John Wiley & Sons, Ltd.