Direct Numerical Simulation of Shock/Boundary Layer Interaction
Professor N. D. Sandham (University of Southampton)
M. Ashworth and D. R. Emerson (Daresbury Laboratory)
Introduction
Fluid flows encountered in real application are invariably turbulent. There is, therefore, an
ever-increasing need to understand turbulence and, more importantly, be able to model turbulent flows with
improved predictive capabilities. Understanding turbulence remains one of the greatest challenges in science.
However, as computing technology continues to improve, it is becoming more feasible to solve the governing
equations of motion – the Navier-Stokes equations – from first principles. The direct solution of the equations
of motion for a fluid, however, remain a formidable task and simulations are only possible for flows with small
to modest Reynolds numbers.
Within the UK, the UKTC has been at the forefront of simulating turbulent flows by direct numerical simulation (DNS).
The consortium has made extensive use of the Cray T3E/1200 to generate data for other members to investigate.
Turbulence modelling, in general, has therefore benefitted significantly from these new data sets.
The long-term objective of the UKTC is to develop a world lead in turbulence simulation and scientific usage of
the resulting data. In order to achieve this goal, there are two aspects that are critical to success. One, of
course, is access to the latest supercomputer technology. This also requires a significant level of resource to
ensure that the simulations are competitive at the world level and are on a par with those of our competitors.
The second aspect is creating an environment whereby we can choose the right simulations to invest in and exploit
these data once they have been validated.
The consortium has worked closely with CCP12 and staff at Daresbury Laboratory. A recent example of this has been
the development of a parallel version of a code to solve problems associated with shock/boundary-layer interaction.
The code (SBLI) has been developed for the Cray T3E and is a sophisticated DNS code that incorporates a number of
advanced features: namely high-order central differencing; a shock-preserving advection scheme from the total variation
diminishing (TVD) family; entropy splitting of the Euler terms and the stable boundary scheme.
The code has been written using standard Fortran 90 code together with the Message Passing Interface (MPI) in order
to be efficient, scalable and portable across a wide range of high-performance platforms. Results for a channel flow
in which turbulence is triggered by introducing known disturbances into the laminar flow field are shown in the figure.
Performance measurements for this benchmark case are presented for the Cray T3E.
The UKTC is now in a prime position to fully exploit the next generation high end computing facility purchased in
the UK. It has formed a strong link with CCP12 and Daresbury Laboratory to be able to fully exploit the next machine
and has recently submitted a new grant to EPSRC to continue the work.
Results from SBLI code
Schematic of Delery "bump" test case
Figure illustrates instantaneous u-velocity contours
Figure illustrates time-averaged u-velocity contours
The test case flow conditions for the above results
with a turbulent inflow, were M=0.6, Red*=1000,
d*=1.0
Grid size: 512 x 64 x 32
The statistics were accumulated after 2400 and 4800 time units
Parallel Performance of SBLI code
Figure shows the performance of SBLI on the Cray
T3E/1200 with F90 static and dynamic memory allocation
Parallel performance on a range of platforms (Loki
is a Linux cluster located at Daresbury Laboratory)
Contact Details
For further information on this work please contact:
Dr. David Emerson
Daresbury Laboratory
Daresbury
Warrington WA4 4AD
England
Tel. +44 (0)1925 603221
Fax. +44 (0)1925 603634
Email: D.R.Emerson@dl.ac.uk
Web Page: http://www.cse.clrc.ac.uk/
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