David B. Carrington

Convective Heat Transfer Downstream of a 3-D Backward-Facing Step

Numerical solutions are obtained for fluid flow and heat transfer downstream of a 3-D backward-facing step within a duct. A heat flux is applied along the bottom surface downstream of the step. The dimensions downstream of the step are 30H 2 12H 2 H, where H = 1 cm (channel height); uniform flow enters a 20H 2 12H 2 H/2 channel upstream of the step. The numerical model is based on a modified Petrov-Galerkin finite element technique that incorporates sparse storage solution with mass lumping. A projection algorithm is used to solve the primitive equations of motion. Upper and lower recirculation zones in the 3-D solutions are very different from 2-D results. Solutions obtained for Re = 400, 800, and 1200 are presented that illustrate changing recirculation and vortex zones. A time history shows the evolution of velocities along the centerline at Re = 800. Bulk Nusselt numbers converge to experimental values downstream of the step where the flow returns to a fully developed parabolic profile.

Application of h‐adaptation for environmental fluid flow and species transport

An adaptive finite element model has been developed for simulating environmental fluid flow and species transport. The model uses Petrov–Galerkin weighting for the advection terms, mass lumping, and a h-adapting scheme that refines and unrefines the mesh using velocity and species concentration gradients. The model is currently being used to calculate atmospheric wind fields over the Nevada Test Site, and to calculate groundwater transport in saturated or unsaturated porous media. The model runs on Pentium PCs and SGI workstations; a parallel version of the model runs on an SGI Origin 2000 computer. Copyright

Modeling Indoor Air Pollution

Fluid Flow Fundamentals Contaminant Sources Assessment Criteria Simple Modeling Techniques Dynamics of Particles, Gases and Vapors Numerical Modeling - Conventional Techniques Numerical Modeling - Advanced Techniques Turbulence Modeling Homeland Security Issues.

A parallel h-adaptive finite element model for atmospheric transport prediction

Abstract A finite element model that uses h-adaptation is used to predict atmospheric wind fields and pollutant transport over the Nevada Test Site. Meteorological data are used to generate a diagnostic flow field; prognostic (forecast) solutions of the time-dependent equations of atmospheric motion and species transport are then obtained. Mass lumping, reduced integration and Petrov–Galerkin weighting are employed in the algorithm. A coarse mesh is first generated; the mesh is then refined and unrefined utilizing parameters based on velocity and species concentration gradients. The model runs on SGI workstations; a parallel version has been ported to the SGI Origin 2000 located within the NSCEE at UNLV.

A Meshless Method for Modeling Convective Heat Transfer

A meshless method is used in a projection-based approach to solve the primitive equations for fluid flow with heat transfer. The method is easy to implement in a MATLAB format. Radial basis functions are used to solve two benchmark test cases: natural convection in a square enclosure and flow with forced convection over a backward facing step. The results are compared with two popular and widely used commercial codes: COMSOL, a finite element model, and FLUENT, a finite volume-based model.

Three-dimensional ALE-FEM method for fluid flow in domains with moving boundaries part 1: algorithm description

A three-dimensional finite element method for simulating fluid flow in domains containing moving objects or boundaries is developed. This method is a type of arbitrary-Lagrangian-Eulerian, based on a fixed mesh that is locally fitted at the moving interfaces and recovers its original shape once the moving interfaces go past the elements. The moving interfaces are defined by marker points so that the global mesh is not affected by the interfaces motion, eliminating potential for mesh entanglement. The result is an efficient and robust formulation for multi-physics simulations. The mesh never becomes unsuitable by continuous deformation, thus eliminating the need for repeated re-meshing. The interface boundaries are exactly imposed Dirichlet type. The total domain volume is always calculated exactly thus automatically satisfying the geometric conservation law. This work supports the internal combustion engines simulator KIVA developed at Los Alamos National Laboratories; in this paper, only the interface moving aspect is addressed.

An h-Adaptive Finite Element Model for Environmental Transport Prediction

The development and implementation of an h-adaptive algorithm with a general finite element solver has been achieved for predicting species transport and dispersion within complex problem geometries. Coupling h-adaptation with a Petrov-Galerkin finite element algorithm produces very accurate solutions while minimizing computer time and storage demands. The finite element method, when coupled with h-adaptation, is well suited for calculating atmospheric and groundwater transport. Future research efforts will include the use of Delaunay triangulation (with the ability to produce hexahedrals), and h-p adaptation.