Multi-Media
Files Derived From Research (under development)
Professor
Radhakrishna Sureshkumar,
Biomolecular Dynamics
1. Brownian Dynamics Simulation (BDS)
of Wormlike DNA Molecules in Extensional Flow (3.5 MB) This movie
illustrates the influence of extension rate on the dynamics of two molecules
with identical initial conditions. The symbol “Wi” denotes the ratio of the
characteristic time scales associated with chain relaxation and the flow. For
Wi =100, the chain extends from a coiled to fully extended state fairly
rapidly. In comparison, for Wi = 10, the configuration landscape is much more
complex. In the latter case, the chain assumes different configurational
states, i.e., fold, kink, dumbbell, half-dumbbell etc., before reaching a state
with nearly full extension.
2. BDS of wormlike DNA Molecules in Acoustic
Streaming Flow (6.2 MB) The movement of the red dot illustrates the motion
of the center of mass of the molecule along the streamline. The configurations
of three molecules from an ensemble of 2000 are shown inside. The flow is
generated by acoustic wave propagation through the fluid.
3. Breaking of a DNA molecule (modeled as a bead-rod
or Kramers chain) in uniaxial extensional flow (3 MB)
Turbulent Drag
Reduction by Polymeric Additives
4. Contours of large positive (blue) and negative
(red) streamwise vorticity and large molecular extension (yellow) in
turbulent channel flow of a dilute polymer solution. Polymeric additives are
used to reduce turbulent friction (by up to 70%) in fluid transportation lines
(e.g. transatlantic oil transportation). Chain extension, especially around the
vortices, enhances the resistance of the fluid to extensional deformation. This
results in the stabilization of the streamwise vortices. Since a large amount
of turbulent stress (Reynolds stress) is produced during the breakup of these
vortices, their stabilization results in flow with reduced friction losses.
Elastic Flow
Instability in Creeping Flow
5. Nonlinear Evolution of Flow Instability in
Creeping Flow of a Viscoelastic Polymer Solution (1 MB) Elastic normal
stresses created by flow-induced stretching of polymer molecules can trigger
instabilities in viscoelastic flows even when inertial forces are much smaller
than viscous ones (i.e., creeping flow limit realized when the Reynolds number
is much smaller than unity). This movie illustrates the nonlinear evolution of
elastic instability in flow through a channel with sinusoidal walls (only a part
of the bottom portion of the channel is shown; the flow is from left to right).
Small perturbations in polymeric stress are “convected” by velocity gradients.
This results in a new flow state with significantly larger chain extension at
the contraction region.
6. Streamlines (left) and Molecular Extension
(right) in Flow between Eccentric Cylinders Gradient of elastic normal
stress in a curvilinear flow is a harbinger of flow instability.
Nonlinear Dynamics
and Pattern Formation in Curvilinear Flows of Dilute Polymer Solutions
7. Spiral Instability in Taylor-Couette Flow (1.4
MB) Polymeric additives can qualitatively alter flow transitions in Newtonian
liquids. In the absence of viscoelastic polymer additives, centrifugal
instability in Taylor-Couette flow (flow between independently rotating
concentric cylinders) causes the development of stationary and axisymmetric
vortices (Taylor vortices). Elastic forces caused by polymeric additives result
in the formation of time-periodic and non-axisymmetric flow
patterns such as spirals and ribbons (super-position of two spirals traveling
in opposite directions). The movie illustrates the spiral pattern and its
eventual transition to a ribbon-like structure as captured by direct numerical
simulations. Higher order transitions, leading to phenomenon such as elastic
turbulence, are under investigation.
Thermoelastic Instability
8. Traveling Waves in Non-Isothermal Flow
Digital Particle Imaging
Velocimetry (DPIV)
9. Tracking Elastic Flow Instabilities
10. Effect of Surfactants on Mixing
Morphological
Transition in Interfacial Nanostructures
11. Electropolymerized Coatings
12. Effect of Surface Reaction Rate
