摘要:

AbstractThe three‐dimensional turbulent flow in a curved hydraulic turbine draft tube is studied numerically. The analysis is based on the steady Reynolds‐averaged Navier–Stokes equations closed with the κ‐ε model. The governing equations are discretized by a conservative finite volume formulation on a non‐orthogonal body‐fitted co‐ordinate system. Two grid systems, one with 34 × 16 × 12 nodes and another with 50 × 30 × 22 nodes, have been used and the results from them are compared. In terms of computing effort, the number of iterations needed to yield the same degree of convergence is found to be proportional to the square root of the total number of nodes employed, which is consistent with an earlier study made for two‐dimensional flows using the same algorithm. Calculations have been performed over a wide range of inlet swirl, using both the hybrid and second‐order upwind schemes on coarse and fine grids. The addition of inlet swirl is found to eliminate the stalling characteristics in the downstream region and modify the behaviour of the flow markedly in the elbow region, thereby affecting the overall pressure recovery noticeably. The recovery factor increases up to a swirl ratio of about 0˙75, and then drops off. Although the general trends obtained with both finite difference operators are in agreement, the quantitative values as well as some of the fine flow structures can differ. Many of the detailed features observed on the fine grid system are smeared out on the coarse grid system, pointing out the necessity of both a good finite difference operator and a good grid distributio

ISSN:0271-2091    

DOI:10.1002/fld.1650061202

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Orr–Sommerfeld equation is solved numerically for a layer of liquid film flowing down an inclined plane under the action of gravity using the sequential gradient‐restoration algorithm (SGRA) The method consists of solving the governing equation as it is a Bolza problem in the calculus of variations. The neutral stability curves, eigenvalues and eigenfunctions to the stability problem can be determined simultaneously during the proc

ISSN:0271-2091    

DOI:10.1002/fld.1650061203

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractNew finite elements have been developed to simulate steady and unsteady two‐dimensional free surface flows. The depth‐averaged velocity components with the free surface elevation have been used as independent variables in the model. The differences between the various elements presented lie in the choice of velocity approximation. The Newton–Raphson method has been used to solve the non‐linear system of equations. Emphasis is put on bench‐mark examples to assess the accuracy and efficiency of the elements. A simple stable new element tested herein shows promising advantages for industrial finite elem

ISSN:0271-2091    

DOI:10.1002/fld.1650061204

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractFinite element models, optimized for running on conventional serial computers, are not suitable to make use of the potentional high performance of today's vector or parallel computers. Also, automatic vectorization by the compiler or manual vectorization at the local level do not by far lead to the required and expected computational speed.A global change of the overall program logic or a complete redesign becomes necessary, i.e. a completely new generation of program systems has to be created, considering the new hardware characteristics and abilities.A new computer‐independent programming technique for finite element problems to be implemented on vector computers is proposed and the test results of scalar and vectorized program structures on a conventional serial and on a non‐conventional pipeline computer are discus

ISSN:0271-2091    

DOI:10.1002/fld.1650061205

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAn implicit two‐equation turbulence solver, KEM. in generalized co‐ordinates, is used in conjunction with the three‐dimensional incompressible Navier–Stokes solver, INS3D, to calculate the internal flow in a channel and a channel with a sudden 2:3 expansion. A new and consistent boundary procedure for a low Reynolds number form of the κ‐ε turbulence model is chosen to integrate the equations up to the wall. The high Reynolds number form of the equations is integrated using wall functions. The latter approach yields a faster convergence to the steady‐state solution than the former. For the case of channel flow, both the wall‐function and wall‐boundary‐condition approaches yield results in good agreement with the experimental data. The back‐step (sudden expansion) flow is calculated using the wall‐function approach. The predictions are in reasonable agreement wit

ISSN:0271-2091    

DOI:10.1002/fld.1650061206

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650061207

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650061208

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650061201

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY