摘要:

AbstractSteps towards the numerical simulation of the flow behind the slug front in horizontal slug flow performed with a streamfunction‐vorticity representation of the mean flow and an energy dissipation model for the turbulence are discussed. The flow field consists of two vortices, one saddle point and four stagnation regions. Attention is focused on the following boundary conditions: moving wall jet, moving wall, free jet velocity discontinuity and vertical liquid‐gas open surface. A dissipation flux boundary condition is suggested to simulate the interaction of the turbulent eddies with the open surface. A method to assess the necessity to use a transport model equation for the dissipation rather than a geometric specification of a length is suggested. Three different ways to characterize the mixing zone length are propo

ISSN:0271-2091    

DOI:10.1002/fld.1650140202

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe divide‐and‐conquer paradigm of iterative domain decomposition or substructuring has become a practical tool in computational fluid dynamics applications because of its flexibility in accommodating adaptive refinement through locally uniform (or quasi‐uniform) grids, its ability to exploit multiple discretizations of the operator equations, and the modular pathway it provides towards parallelism. We illustrate these features on the classic model problem of flow over a backstep using Newton's method as the non‐linear iteration. Multiple discretizations (second‐order in the operator and first‐order in the preconditioner) and locally uniform mesh refinement pay dividends separately and can be combined synergistically. We include sample performance results from an Intel iPSC/860 hypercube imp

ISSN:0271-2091    

DOI:10.1002/fld.1650140203

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe observed phenomenon of slip between the layers of a flowing slurry is modelled mathematically by a finite‐element‐based numerical technique. This technique enables us to quantify variables such as the slip velocity and shear stress distribution at the interlayer boundary and the pressure drop within the flow dom

ISSN:0271-2091    

DOI:10.1002/fld.1650140204

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper describes the implementation of a fire field model in the parallel computing environment offered by multiple transputers. The fire model is built into the general purpose SIMPLE‐based CFD code HARWELL‐FLOW3D. The technique of domain decomposition has been applied tb convert the conventional serial version of FLOW3D into a code capable of efficiently utilizing an arbitrary number of transputers. Fire simulations consisting of up to 24 000 computational cells are performed on parallel systems with up to 15‐processors. The run time for this simulation has been reduced from over 4 days on a single processor to just over 8 h on the 15‐processor system. An interactive graphics system has also been developed which runs in parallel with the main compu

ISSN:0271-2091    

DOI:10.1002/fld.1650140205

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA slope modification method is proposed for non‐oscillatory schemes based on the Lax‐Friedrich solver. The modified scheme is proved to be total‐variation‐diminishing (TVD) and second‐order accurate. Application of the scheme to the shallow water equations produces sharp profiles for shocks and achieves high accuracy in the smooth regions of the

ISSN:0271-2091    

DOI:10.1002/fld.1650140206

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe Navier–Stokes–Boussinesq equations governing the transport of momentum, mass and heat in a non‐isothermal liquid bridge with a temperature‐dependent surface tension are solved using a vorticity‐stream‐function formulation together with a non‐orthogonal co‐ordinate transformation. The equations are discretized using a pseudo‐unsteady semi‐implicit finite difference scheme and are solved by the ADI method. A Picard‐type iteration is adopted which consists of inner and outer iterative processes. The outer iteration is used to update the shape of the free surface. Two schemes have been used for the outer iteration; both use the force balance normal to the free surface as the distinguished boundary condition. The first scheme involves successive approximation by the direct solution of the distinguished boundary condition. The second scheme uses the artificial force imbalance between the fluid pressure, viscous and capillary forces at the free surface which arises when the boundary condition for force balance normal to the surface is not satisfied. This artificial imbalance is then used to change the surface shape until the distinguished boundary condition is satisfied. These schemes have been used to examine a variety of model liquid bridge situations including purely thermocapillary‐driven flow situations and mixed thermocapillary‐

ISSN:0271-2091    

DOI:10.1002/fld.1650140207

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractHot flow of a sudden‐expansion dump combustor with swirling is analysed by employing an infinite chemical reaction rate. Turbulence properties are closed using one type of algebraic Reynolds stress model and two types of κ–ϵ model. One of the κ–ϵ models includes a swirling effect modification to the ε‐equation. Computations have been performed by the SIMPLE‐C algorithm with a power‐law scheme. The calculated results of the momentum fields and turbulence quantities for swirling flow are compared with the available experimental data. It is shown that the standard κ–ϵ model gives poor prediction of the mean velocity, particularly the tangential velocity. For the hot flow analysis of a sudden‐expansion dump combustor with swirling flow it is suggested that it is necessary to use the modified κ–ϵ model or algeb

ISSN:0271-2091    

DOI:10.1002/fld.1650140208

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe paper reports on a numerical study of turbulent confined jets in a conical duct with a 5° divergence. The flow has a large ratio of jet to ambient velocities at the entrance so that it gives rise to strong recirculation. The calculations are carried out with a general finite volume method designed for calculating incompressible elliptic flows with complex boundaries. Turbulence is simulated by the standard κ–ϵ model. The sensitivity of the solution to numerical discretization errors is examined using three convection schemes, i.e. hybrid central/upwind differencing, QUICK and SOUCUP, on two grids consisting of 68 × 50 and 102 × 82 points respectively. An examination is also made of the influence of inlet boundary conditions on the predicted flow field. The computed results are compared with experimental data for mean axial velocity, turbulent shear stress and turbulent kinetic energy profiles. It is shown that the calculations reproduce the essential features of the flow observed in the exper

ISSN:0271-2091    

DOI:10.1002/fld.1650140209

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650140201

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY