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Progress in the numerical simulation of turbulence has been rapid
in the 1990s. New techniques both for the numerical approximation
of the Navier-Stokes equations and for the subgrid-scale models
used in large-eddy simulation have emerged and are being widely
applied for both fundamental and applied engineering studies, along
with novel ideas for the performance and use of simulation for
compressible, chemically reacting and transitional flows. This
collection of papers from the second ERCOFTAC Workshop on Direct
and Large-Eddy Simulation, held in Grenoble in September 1996,
presents the key research being undertaken in Europe and Japan on
these topics. Describing in detail the ambitious use of DNS for
fundamental studies and of LES for complex flows of potential and
actual engineering importance, this volume will be of interest to
all researchers active in the area.
It is a truism that turbulence is an unsolved problem, whether in
scientific, engin eering or geophysical terms. It is strange that
this remains largely the case even though we now know how to solve
directly, with the help of sufficiently large and powerful
computers, accurate approximations to the equations that govern tur
bulent flows. The problem lies not with our numerical
approximations but with the size of the computational task and the
complexity of the solutions we gen erate, which match the
complexity of real turbulence precisely in so far as the
computations mimic the real flows. The fact that we can now solve
some turbu lence in this limited sense is nevertheless an enormous
step towards the goal of full understanding. Direct and large-eddy
simulations are these numerical solutions of turbulence. They
reproduce with remarkable fidelity the statistical, structural and
dynamical properties of physical turbulent and transitional flows,
though since the simula tions are necessarily time-dependent and
three-dimensional they demand the most advanced computer resources
at our disposal. The numerical techniques vary from accurate
spectral methods and high-order finite differences to simple
finite-volume algorithms derived on the principle of embedding
fundamental conservation prop erties in the numerical operations.
Genuine direct simulations resolve all the fluid motions fully, and
require the highest practical accuracy in their numerical and
temporal discretisation. Such simulations have the virtue of great
fidelity when carried out carefully, and repre sent a most powerful
tool for investigating the processes of transition to turbulence.
It is a truism that turbulence is an unsolved problem, whether in
scientific, engin eering or geophysical terms. It is strange that
this remains largely the case even though we now know how to solve
directly, with the help of sufficiently large and powerful
computers, accurate approximations to the equations that govern tur
bulent flows. The problem lies not with our numerical
approximations but with the size of the computational task and the
complexity of the solutions we gen erate, which match the
complexity of real turbulence precisely in so far as the
computations mimic the real flows. The fact that we can now solve
some turbu lence in this limited sense is nevertheless an enormous
step towards the goal of full understanding. Direct and large-eddy
simulations are these numerical solutions of turbulence. They
reproduce with remarkable fidelity the statistical, structural and
dynamical properties of physical turbulent and transitional flows,
though since the simula tions are necessarily time-dependent and
three-dimensional they demand the most advanced computer resources
at our disposal. The numerical techniques vary from accurate
spectral methods and high-order finite differences to simple
finite-volume algorithms derived on the principle of embedding
fundamental conservation prop erties in the numerical operations.
Genuine direct simulations resolve all the fluid motions fully, and
require the highest practical accuracy in their numerical and
temporal discretisation. Such simulations have the virtue of great
fidelity when carried out carefully, and repre sent a most powerful
tool for investigating the processes of transition to turbulence."
Progress in the numerical simulation of turbulence has been rapid
in the 1990s. New techniques both for the numerical approximation
of the Navier-Stokes equations and for the subgrid-scale models
used in large-eddy simulation have emerged and are being widely
applied for both fundamental and applied engineering studies, along
with ideas for the performance and use of simulation for
compressible, chemically reacting and transitional flows. This
collection of papers from the second ERCOFTAC Workshop on Direct
and Large-Eddy Simulation, held in Grenoble in September 1996,
presents the research being undertaken in Europe and Japan on these
topics. Describing in detail the ambitious use of DNS for
fundamental studies and of LES for complex flows of potential and
actual engineering importance, this volume should be of interest to
researchers active in the area.
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