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A newly developed computational approach different from the conventional methods which are popularly adapted by the fan designers is employed to study the flow field and performance characteristics of an axial flow fan by using the commercial code (STAR-CD) of computational fluid dynamics. The new approach, which is termed the "downstream flow resistance" (DFR) method, engages the flow resistance of the fan test bench in the downstream area of the computational domain. Both the static and moving grids are employed in the computation. The results show at least three emphases. Firstly, the...
This paper aims to improve current understanding of flow structure and particle deposition in asthmatic human airways. A single, symmetric airway bifurcation, corresponding to generations 10–11 of Weibel’s model, is investigated through validated numerical simulations. The parent airway segment is modelled as a smooth circular tube. The child segments are considered asthmatic and their cross-section is modelled as a constricted tube with sinusoidal folds uniformly distributed along the circumference. The flow structure and particle deposition pattern for normal (i.e., healthy) and asthmatic...
In conjunction with the NASA-Gulfstream and Gulfstream-University of Florida wind tunneltesting of a generic nose landing gear model, Computational Aero-Acoustics research was conducted at Gulfstream using the commercial Navier-Stokes Finite Volume CFD solver STAR-CCM+. The simulation modeled the ¼ scale G550 nose landing gear mounted in the NASA Basic Aerodynamics Research Tunnel (BART) wind tunnel test section. The model was run at the 0.166 Mach Number condition on the simplified nose landing gear with the gear cavity closed. Prior to simulation execution,dynamic pressure probes were...
A method is proposed to calculate the trailing-edge broadband noise emitted from an airfoil, based on a steady Reynolds-averaged Navier–Stokes solution of the flowfield. For this purpose, the pressure spectrum on the airfoil surface near the trailing edge is calculated using a statistical model from the Reynolds-averaged Navier–Stokes mean velocity and turbulence data in the airfoil boundary layer. The obtained wall-pressure spectrum is used to compute the radiated sound by means of an aeroacoustic analogy, namely, Amiet’s theory of airfoil sound. The statistical model for wall-pressure...
Transported probability density function (PDF) methods have been applied widely and effectively for modelling turbulent reacting flows. In most applications of PDF methods to date, Lagrangian particle Monte Carlo algorithms have been used to solve a modelled PDF transport equation. However, Lagrangian particle PDF methods are computationally intensive and are not readily integrated into conventional Eulerian computational fluid dynamics (CFD) codes. Eulerian field PDF methods have been proposed as an alternative. Here a systematic comparison is performed among three methods for solving the...
This paper compares two mean reaction rate closures for turbulent reacting flow: the Stochastic Fields (SF) method and the Direct Quadrature Method of Moments using the Interaction by Exchange with the Mean micromixing model (DQMoM-IEM). The methods have many common features and have received significant attention in recent literature, yet have not been systematically compared. We present both methods in the same mathematical framework and compare their numerical performance. In addition, we introduce antithetic sampling as a variance reduction technique to increase the efficiency of the SF...
A comparative study of predictions obtainable using the conformal and indirect interfaces for Conjugate Heat Transfer (CHT) analysis in an exhaust manifold was undertaken with a view to ascertain the degree of closeness of certain pre-defined physical quantities. The Indirect Mapped Interface feature has been incorporated in the latest release version (V7.02) of the multidisciplinary engineering simulation tool STAR-CCM+ and enables the use of non-conformal mesh at the interface between solid and fluid domains for CHT simulations. A steady-state analysis was performed for base mesh size...
A comparative study of predictions obtainable using the conformal and indirect interfaces for Conjugate Heat Transfer (CHT) analysis in an exhaust manifold was undertaken with a view to ascertain the degree of closeness of certain pre-defined physical quantities. The Indirect Mapped Interface feature has been incorporated in the latest release version (V7.02) of the multidisciplinary engineering simulation tool STAR-CCM+ and enables the use of non-conformal mesh at the interface between solid and fluid domains for CHT simulations. A steady-state analysis was performed for base mesh size...
This study examines the accuracy of solving the multi-component equations for a Proton Exchange Membrane Fuel Cell (PEMFC) by using a Computational Fluid Dynamics (CFD) technique. This technique uses an approximated multi-component (AMC) model with a correction term that guarantees the overall mass balance. Accuracy is assessed by comparing the species concentration computed with the Maxwell–Stefan and the corrected AMC models. This comparison is important because the structure of some CFD programs does not permit the direct use of the Maxwell–Stefan equations and this leads to confusion in...
Stringent emissions standards (Euro 6 and Tier2Bin5) lead to the use of nitrogen oxides (NOx) after treatment. One of the most widespread technical solutions able to meet these legislations is Urea Selective Catalytic Reduction (Urea SCR). A urea aqueous solution is introduced into the exhaust system in order to reduce NOx over SCR catalyst. Before reaching the catalyst, the aqueous solution has to be transformed into ammonia. Current serial applications need long distances (>400 mm) from injection point to SCR catalyst and a mixer apparatus to ensure sufficient mixing between exhaust gas...

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