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direct numerical simulation of incompressible pipe flow using a b-spline spectral methodA numerical method based on b-spline polynomials was developed to study incompressible flows in cylindrical geometries. A b-spline method has the advantages of possessing spectral accuracy and the flexibility of standard finite element methods. Using this method it was possible to ensure regularity of the solution near the origin, i.e. smoothness and boundedness. Because b-splines have compact support, it is also possible to remove b-splines near the center to alleviate the constraint placed on the time step by an overly fine grid. Using the natural periodicity in the azimuthal direction and approximating the streamwise direction as periodic, so-called time evolving flow, greatly reduced the cost and complexity of the computations. A direct numerical simulation of pipe flow was carried out using the method described above at a Reynolds number of 5600 based on diameter and bulk velocity. General knowledge of pipe flow and the availability of experimental measurements make pipe flow the ideal test case with which to validate the numerical method. Results indicated that high flatness levels of the radial component of velocity in the near wall region are physical; regions of high radial velocity were detected and appear to be related to high speed streaks in the boundary layer. Budgets of Reynolds stress transport equations showed close similarity with those of channel flow. However contrary to channel flow, the log layer of pipe flow is not homogeneous for the present Reynolds number. A topological method based on a classification of the invariants of the velocity gradient tensor was used. Plotting iso-surfaces of the discriminant of the invariants proved to be a good method for identifying vortical eddies in the flow field.
Document ID
19970011270
Document Type
Technical Memorandum (TM)
Authors
Loulou, Patrick
(Stanford Univ. Stanford, CA United States)
Moser, Robert D.
(NASA Ames Research Center Moffett Field, CA United States)
Mansour, Nagi N.
(NASA Ames Research Center Moffett Field, CA United States)
Cantwell, Brian J.
(Stanford Univ. Stanford, CA United States)
Date Acquired
September 6, 2013
Publication Date
February 1, 1997
Subject Category
Fluid Mechanics and Heat Transfer
Report/Patent Number
A-975743
NAS 1.15:110436
NASA-TM-110436
Funding Number(s)
PROJECT: RTOP 505-59-53
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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