摘要:

AbstractIn this paper we consider a parameter estimation procedure for shallow sea models. The method is formulated as a minimization problem. An adjoint model is used to calculate the gradient of the criterion which is to be minimized. In order to obtain a robust estimation method, the uncertainty of the open boundary conditions can be taken into acoount by allowing random noise inputs to act on the open boundaries. This method avoids the possibility that boundary errors are interpreted by the estimation procedure as parameter fluctuations. We apply the parameter estimation method to identify a shallow sea model of the entire European continental shelf. First, a space‐varying bottom friction coefficient is estimated simultaneously with the depth. The second application is the estimation of the parameterization of the wind stress coefficient as a function of the wind velocity. Finally, an uncertain open boundary condition is included. It is shown that in this case the parameter estimation procedure does become more robust and produces more realistic estimates. Furthermore, an estimate of the open boundary conditions is also obtaine

ISSN:0271-2091    

DOI:10.1002/fld.1650170802

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPreconditioned conjugate gradient algorithms for solving 3D Stokes problems by stable piecewise discontinuous pressure finite elements are presented. The emphasis is on the preconditioning schemes and their numerical implementation for use with Hermitian based discontinuous pressure elements. For the piecewise constant discontinuous pressure elements, a variant implementation of the preconditioner proposed by Cahouet and Chabard for the continuous pressure elements is employed. For the piecewise linear discontinuous pressure elements, a new preconditioner is presented. Numerical examples are presented for the cubic lid‐driven cavity problem with two representative elements, i.e. the Q2‐PO and the Q2‐P1 brick elements. Numerical results show that the preconditioning schemes are very effective in reducing the number of pressure iterations at very reasonable costs. It is also shown that they are insensitive to the mesh Reynolds number except for nearly steady flows (Rem→ 0) and are almost independent of mesh sizes. It is demonstrated that the schemes perform reasonably well on non‐unifo

ISSN:0271-2091    

DOI:10.1002/fld.1650170803

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAn algorithm for the solutions of the two‐dimensional incompressible Navier–Stokes equations is presented. The algorithm can be used to compute both steady‐state and time‐dependent flow problems. It is based on an artificial compressibility method and uses higher‐order upwind finite‐volume techniques for the convective terms and a second‐order finite‐volume technique for the viscous terms. Three upwind schemes for discretizing convective terms are proposed here. An interesting result is that the solutions computed by one of them is not sensitive to the value of the artificial compressibility parameter. A second‐order, two‐step Runge–Kutta integration coupling with an implicit residual smoothing and with a multigrid method is used for achieving fast convergence for both steady‐ and unsteady‐state problems. The numerical results agree well with experimental and other numerical data. A comparison with an analytically exact solution is performed to verify the space and time

ISSN:0271-2091    

DOI:10.1002/fld.1650170804

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA numerical code has been implemented for the numerical solution of the steady, incompressible Navier–Stokes equations using primitive variables in a bifurcating channel. A boundary‐fitted, numerically generated grid is placed onto the domain of the channel which is transformed into either a rectilinear C‐ or T‐shaped region. The differenced equations are solved using Newton's iteration which makes upwinding at high Reynolds number unnecessary. Practical implications of inverting the huge Jacobian matrix of Newton's method are discussed. The results have relative error of 2–3 × 10−3at Reynolds number 100, with T‐geometry being marginally but significantly more accurate than C‐geometry. Results have been obtained for Reynolds numbers up to 1000 for three bifurcations one of which models the carotid arterial bifurcation in the human head. For this latter bifurcation the wall shear stress is calculated in connection with the onset of atherosclerosis. Finally, the results of flows having different daughter tube end pressur

ISSN:0271-2091    

DOI:10.1002/fld.1650170805

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650170801

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY