It seems to make sense for us to add 125K and then take up the other 125K
at the next allocations meeting.
Comments?
Ray
On 11/12/13 12:17 PM, "accounts(a)lcrc.anl.gov" <accounts(a)lcrc.anl.gov>
wrote:
>Hello,
>
>A change in allocation has been requested:
>
> Requester: paul (Mark Paul)
> Project: Chaos
> Title: Spatiotemporal chaos and turbulence in fluids
> Description: This is a continuing project with this year's allocation
>request building upon last year's progress. All of our calculations use
>spectral element methods to explore the spatiotemporal chaos and
>turbulence of fluid systems. The code nek5000 has previously demonstrated
>scalability and efficiency for the specific problems that we are
>interested in.
>
>We continue to make significant progress on the numerical simulation of
>Rayleigh-Benard convection for experimentally realistic conditions.
>Rayleigh-Benard convection is the buoyancy induced convection that occurs
>when a fluid layer is heated uniformly from below. We are most
>interested in cases where the fluid dynamics of the convection layer is
>chaotic or turbulent. Specifically, the code integrates the
>three-dimensional time-dependent Boussinesq equations, any associated
>reaction-diffusion-advection equations for the transport of scalar
>quantities of interest, and the linearized tangent-space equations for
>computing Lyapunov diagnostics. The code is geometrically flexible and
>can handle a number of experimentally appropriate boundary conditions.
>The Lyapunov diagnostics we can compute include the spectrum of Lyapunov
>exponents and vectors that can be used to provide fundamental insights
>into the complex dynamics that include the fractal dimension and the
>location of fast
> growing perturbations.
>
>In this allocation we propose to continue exploring the following
>problems.
>
>1) Transport in chaotic flow fields
>
>In this project we are interested in exploring the transport dynamics of
>a scalar species when the underlying fluid dynamics are spatiotemporally
>chaotic. During the previous year's allocation we successfully validated
>our numerical approach through a careful series of numerical tests.
>During this year's allocation we will continue with production level
>simulations for very large spatial domains that include a range of
>transport dynamics to study. We are most interested in the parameter
>regime where the time scales of the chaotic convective fluid motion, the
>reaction of the scalar species, and the diffusion of the scalar species
>are comparable. We have already successfully performed preliminary
>calculations on blues. We would like to compute the transport in a
>cylindrical domain of aspect ratio of 40 over a range of Lewis,
>Damkohler, and Rayleigh numbers. There are may open challenges and open
>questions regarding the active transport of a scalar species in a chaotic
>flow
> field. Nearly all current work to date in the literature has focussed
>upon the case of simple periodic flow fields. With our work we proposed
>to explore well into the chaotic regime and to quantify the dynamics of
>transport.
>
>2) Quantifying spatiotemporal chaos
>
>In this effort we will perform large scale numerical simulations of
>chaotic fluid convection for the precise conditions of experiment. We
>will explore large cylindrical domains with aspect ratios of 30 and
>larger for very long times (several horizontal diffusion times). We are
>particularly interested in using and developing diagnostics that shed
>physical insight upon fundamental features of the underlying
>high-dimensional chaos. We will use our current capability to compute the
>Lyapunov exponents, Lyapunov vectors, and the fractal dimension for a
>range of conditions of current experimental interest in the convection
>community. One aspect we will focus upon is using the temporal and
>spatial averages of the leading order Lyapunov vector to quantify regions
>and dynamics of interest. We are interested in searching for a
>connection between these Lyapunov based diagnostics, which can only be
>computed and are not accessible to experiment, with quantities and
>diagnostics that can be
> measured in experiment. We are in direct communication with
>experimentalists interested in comparing the results of our simulations
>with experimental measurements. We have identified several important test
>problems to explore that we will focus upon during this allocation. We
>have already performed test runs of blues and the runs requested for this
>allocation do not require significant code development.
>
>We have developed the ability to compute the covariant Lyapunov vectors
>to quantify the spatial disorder in the patterns. The covariant Lyapunov
>vectors are much more difficult to calculate than the Gram-Schmidt based
>Lyapunov vectors but have the benefit of providing all of the directions
>of perturbation growth in the high dimensional phase space (called
>Oseledec's splitting). The covariant Lyapunov vectors have not been
>calculated for an experimentally accessible fluid system and have the
>potential to provide new and important insights into the regions and
>directions that contribute most to the chaos. In order to connect with
>experiment we are also going to explore the use of realistic boundary
>conditions such as walls of finite thermal conductivity and varying fluid
>properties. Our current code is a serial implementation of the
>algorithm. We intend to parallelize the code in order to explore much
>larger systems.
>
>3) Turbulent thermal convection.
>
>We would like to continue our three-dimensional numerical simulations of
>fully turbulent Rayleigh-Benard convection cells for lower Prandtl number
>(0.021). By going to very low Prandtl number, we will explore a region of
>parameter space that has not been well-studied, either experimentally or
>numerically. Low Prandtl number has direct application to convection in
>liquid metals, and can also shed light on the convection in the earth’s
>liquid metal core and in the sun and other stars which can have even
>lower Prandtl numbers.
>
>We would also like to perform simulations of turbulent RBC at moderate
>Prandtl number (0.7) and Rayleigh number (10^7-10^{10}). Many experiments
>are currently being performed in this moderate Prandtl number regime (and
>for even higher Rayleigh numbers), but this system is not well understood
>theoretically. Thermal plumes are present in turbulent convection as a
>means of heat transport. In addition, a large-scale circulation (LSC) has
>been found, which sweeps the thermal plumes along like leaves in a wind.
>This LSC is not steady and also undergoes chaotic, abrupt reversals.
>Visualizations are extremely difficult in experiments, so numerical
>simulations are essential for bridging the gap between experiment and
>theory. Heat transport measurements can also be determined from these
>simulations and compared to experiments and theoretical predictions. Thin
>thermal and viscous boundary layers are present, and we can perform a
>detailed analysis of these boundary layers, which are key
> to understanding the nature of turbulence in these cells. Finally
>Lyapunov exponents can be computed for these systems and a correlation is
>expected between the time dependence of the LSC and the time dependence
>of one of the Lyapunov exponents. Turbulent Rayleigh-Benard systems have
>application to such diverse phenomena as weather forecasting and the
>reversal of the earth's magnetic field.
> Current: undetermined amount
>Justification: Not required for our request.
>
> Requested: 250000
>
>A specific reason has been given:
>We have nearly exhausted our current allocation on blues for the chaos
>project and would like to request an additional 250,000 hours for the
>first
>6 months of the fiscal year. We used up our initial 6-month allocation
>in
>the first month. This is partly due to a graduate student who is running
>production level simulations for their thesis. We have several projects
>moving forward that are making good progress on blues that would benefit
>significantly from the additional hours.
>
>Please let me know if there is more information I can provide.
>
>Mark Paul
>
>This needs to be approved and the final allocation amount decided upon.
>
>Thank You,
>The LCRC Accounts System
