Coolant passage heat transfer with rotation, a progress report

The objective of this 36-month experimental and analytical program is to develop a heat transfer and pressure drop database, computational fluid dynamic techniques, and correlations for multipass rotating coolant passages with and without flow turbulators. The experimental effort will be focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines so that the effects of Coriolis and buoyancy forces on the coolant side flow can be rationally included in the design of turbine blades

Behaviour of acoustic waves in a duct with Helmholtz resonator in presence of a temperature gradient

Understanding the behaviour of one-dimensional acoustical wave propagation in ducts is very important for controlling combustion instabilities in propulsion, household burners, gas turbine combustors, and designing engineering mufflers. This paper is concerned with ducts in which temperature gradient exist. Computational Fluid Dynamics (CFD) simulation of the acoustic wave propagations through a duct with Helmholtz resonators in the presence of a mean temperature gradient without mean air flow has been investigated. Acoustic pressure and axial velocity amplitudes have been calculated as a function of time. Time and axial distance dependent acoustic pressure and velocity are visualised as 3D surface plots

Coolant passage heat transfer with rotation

The objective is to develop a heat transfer and pressure drop data base, computational fluid dynamic techniques, and correlations for multi-pass rotating coolant passages with and without flow turbulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades

Lead extrusion analysis by finite volume method

Computational numerical simulation is nowadays largely applied in the design and analysis of metal forming process. Extrusion of metals is one main forming process largely applied in the manufacturing of metallic products or parts. Historically, the Finite Element Method has been applied for decades in metal extrusion analysis [4]. However, recently in the academy, there is a trend to use Finite Volume Method: literature suggests that metal flow by extrusion can be analyzed by the flow formulation [1, 2]. Thus, metal flow can be modelled such us an incompressible viscous fluid [2]. This hypothesis can be assumed because extrusion process is an isochoric process. The MacCormack Method is commonly used to simulate compressible fluid flow by the finite volume method [3]. However, metal extrusion and incompressible fluid flow do not present state equations for the evolution of pressure, and therefore, a velocity-pressure coupling method is necessary to obtain a consistent velocity and pressure fields [3]. Present work proposes a new numerical scheme to obtain information about metal flow in the extrusion process, in steady state. The governing equations were discretized by Finite Volume Method, using the Explicit MacCormack Method to structured and collocated mesh. The SIMPLE Method was applied to attain pressure-velocity coupling [3]. These new numerical scheme was applied to forward extrusion process of lead. The incompressible metal extrusion velocity fields achieved faster convergence and a good agreement with analytical and experimental results obtained from literature. The MacCormack Method applied for metals produced consistent results without the need of artificial viscosity as employed by the compressible flow simulation approaches. Furthermore, the present numerical results also suggest that MacCormack Method and SIMPLE can be applied in the solution of metal forming processes besides the traditional application for compressible fluid flow

Simulation of Counterintuitive Pressure Drop in a Parallel Flow Design for a Specimen Basket for Use in the Advanced Test Reactor

The Boosted Fast Flux Loop (BFFL) will expand the Advanced Test Reactor (ATR) at Idaho National Laboratory. Part of the BFFL is a new corrosion test cap section for testing in the ATR. The corrosion test cap section was designed with parallel channels to reduce the pressure drop and allow coolant contact with specimens. The fluid experiment conducted by Idaho State University found the pressure drop not characteristic of parallel channel flow but greater than without parallel channels. A Computation Fluid Dynamics simulation using STAR-CCM+ was conducted with the objectives of showing sufficient flow through the test cap section for a corrosion test, verifying the fluid experiment\u27s validity, and explaining the abnormal pressure drop. The simulation used a polyhedral volume mesh and the k-e turbulent model with segregated equations. Convergence depended on a low continuity residual and an unchanging pressure drop result. The simulation showed the same pattern as the fluid experiment. The simulation provided evidence of flow through the test cap section needed for a corrosion test. The specimen holding assembly was found to be a small contributor to the pressure drop. The counterintuitive pressure drop was found to be the sum of many factors produced from the geometry of the test cap section. The inlet of the test cap section behaved as a diverging nozzle before a sudden expansion into the test cap section chamber with both creating a pressure drop. The chaotic flow inside the chamber gave rise to pressure loss from mixing. The fluid exited the chamber through a sudden contraction to a converging nozzle behaving exit, again, producing a pressure drop. By varying the flow rate in the simulation, a disturbance in the flow where the gap fluid separated into the parallel channels was found at high flow rates. At low flow rates the pressure drop anomaly was not found. The corrosion test cap section could be used in the ATR but with a higher pressure drop than desirable. The design of the corrosion test cap section created the abnormal pressure drop

Second order perturbations of a zero-pressure cosmological medium: Proofs of the relativistic-Newtonian correspondence

The dynamic world model and its linear perturbations were first studied in Einstein's gravity. In the system without pressure the relativistic equations coincide exactly with the later known ones in Newton's gravity. Here we prove that, except for the gravitational wave contribution, even to the second-order perturbations, equations for the relativistic irrotational zero-pressure fluid in a flat Friedmann background coincide exactly with the previously known Newtonian equations. Thus, to the second order, we correctly identify the relativistic density and velocity perturbation variables, and we expand the range of applicability of the Newtonian medium without pressure to all cosmological scales including the super-horizon scale. In the relativistic analyses, however, we do not have a relativistic variable which corresponds to the Newtonian potential to the second order. Mixed usage of different gauge conditions is useful to make such proofs and to examine the result with perspective. We also present the gravitational wave equation to the second order. Since our correspondence includes the cosmological constant, our results are relevant to currently favoured cosmology. Our result has an important practical implication that one can use the large-scale Newtonian numerical simulation more reliably even as the simulation scale approaches near horizon.Comment: 10 pages, no figur

Hamiltonian adaptive resolution simulation for molecular liquids

Adaptive resolution schemes allow the simulation of a molecular fluid treating simultaneously different subregions of the system at different levels of resolution. In this work we present a new scheme formulated in terms of a global Hamiltonian. Within this approach equilibrium states corresponding to well defined statistical ensembles can be generated making use of all standard Molecular Dynamics or Monte Carlo methods. Models at different resolutions can thus be coupled, and thermodynamic equilibrium can be modulated keeping each region at desired pressure or density without disrupting the Hamiltonian framework.Comment: 11 pages, 3 Figure