摘要:

AbstractThis is the first of two articles intended to develop, apply and verify a new method for averaging the momentum and mass transport equations for turbulence. The new method is based on Gaussian filtering in both the spatial and temporal domains. Application is made to the problem of momentum and scalar transport in a one‐dimensional transient Burgers' flow field. No actual calculations, with the averaged equations, are presented in this paper. However, an ‘exact’ solution of the one‐dimensional flow situation is presented as an economical tool for verifying the performance of the different turbulence models. In the second paper calculations are performed with the averaged one‐dimensional equations on coarse grids, and the results are compared to the exact or fully simulated data with a statistical verification

ISSN:0271-2091    

DOI:10.1002/fld.1650060202

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThis is the second of two articles intended to develop, apply and verify a new method for averaging the momentum and mass transport equations for turbulence. Part I presented the theoretical development of a new space‐time filter (STF) averaging procedure. The new method, as well as all existing averaging procedures, are applied to the one‐dimensional transient equations of momentum and scalar transport in a Burgers' flow field. Dense‐grid ‘exact’ results from the unaveraged equations are presented to depict the dynamic behaviour of the flow field and serve as a basis for verifying the coarse‐grid STF predictions. In this paper, a finite difference procedure is used to numerically solve the new STF averaged equations, as well as the other forms of the averaged equations derived in Part I. All averaged equations are solved on the same coarse grid. The velocity and scalar fields, predicted from each equation form, are intercompared according to a verification procedure based on the statistical and spectral properties of the results. It is found that the new STF procedure improves coarse‐grid dynamic predictions over the existing methods

ISSN:0271-2091    

DOI:10.1002/fld.1650060203

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe unsteady frictional flow of a compressible fluid generated in a long pipeline after an accidental rupture is of considerable interest to the offshore gas industry. It answers several important questions concerning safety and pollution, e.g. the flow rate at the broken pipe end.Laboratory tests cannot simulate the rather complex phenomenon satisfactorily. The problem is highly non‐linear and no general analytical solution is yet known.In this study, based on computational fluid dynamics, the simplifying assumptions of isothermal and low Mach number flow often applied in the case of unsteady compressible flows in pipelines, have not been used.Owing to the choking condition (Ma=1) which prevails for some time at the broken end. and the cumulative effect of friction over the 145 km long pipeline, we obtain (∂p/∂x)t→−∞. This analytically established singularity leads to numerical difficulties which seriously affect the accuracy. For short tubes (such as shock tubes) this negative feature is much less severe. Special procedures were necessary to keep the accuracy within the chosen limit of

ISSN:0271-2091    

DOI:10.1002/fld.1650060204

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650060205

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650060201

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY