Many small planktonic organisms bear spines, some of whose potential functions have been explored, e.g., in increasing drag during gravitational settling or in defense against predators. We have developed full computational fluid dynamic simulations that examine the rotation of a diatom with varying spine number, length and angle in shear flows. We found that motion of spined cells can be accurately predicted from simple theory for spheroid motion by applying that theory to the smallest spheroid inscribing the cell inclusive of its spines.
This is a CCS collaboration with the University of Maine.
Ph. D candidate, Biomedical Engineering
Overlay of the forward- and backward-time Finite-time Lyapunov exponent (FTLE) fields in a fluid displaced by a migrating bubble with both steady an sinusoidal velocity components.
In collaboration with Donald Gaver, Sarah Lukens, and Lisa Fauci.
A star falling through a viscoelastic Christmas tree
The green to red shading shows the accumulating stress in the tree. This work uses a numerical particle method for viscoelastic flow developed at the Center for Computational Science in collaboration with Ricardo Cortez, Lisa Fauci, and John Chrispell.
Muscle activation properties and body stiffness affect the wake structure shed by a virtual lamprey.
This is a CCS collaboration between Chia-yu Hsu, Post-doctorial researcher and Eric Tytell, John Hopkins University.
Spreading of Surfactant over Liquid Surface
The presence of an inhomogeneous distribution of surfactants on air-liquid interfaces, which results in surface tension gradients, causes tangential stresses and Marangoni flow. The Moving Particle Semi-implicit method (MPS) is used. This computation performed on a NVIDIA Tesla C1060 GPU.
Peristaltic Particle Pumping
The attached art shows a snap shot of the velocity field and the trace of the viscoelastic extra stress tensor (denoting polymer distension) for a solid particle in a periodic peristaltic pumping channel.
Ph. D candidate, Biomedical Engineering
The transport of two solutions (blue and pink) that react to form a complex (green) is simulated in spiral geometry. In the left spiral, the blue and pink solutions enter in parallel through the inlet at the top; in the right spiral, the blue and pink solutions sequentially enter the channel. A pressure drop between the inlet and outlet in the center drives the flow. Green indicates where the two solutions have mixed. The velocity field is computed by solving the Stokes equations with the boundary element method. The grid-free particle strength exchange method is implemented to solve the convection-diffusion-reaction equation for the concentrations of the reactants and complex.
This work is funded by NSF EPSCoR.
Fluid flows past an anchored star, shedding vortices in its wake. Computation done with CFD solver Fluent.
Nucleosomes are 147 basepairs (bp) DNA surrounding histone protein in a ~1.7 left handed superhelix. Nucleosomal DNA tends to kink in preferred position around histone. The kink is also a material property of DNA and depends on the bp. This figure shows a series of 21 different nucleosomes formed by inserting one bp at a time from one end and taking out one from the other. Thus 21 bp are replaced keeping 126 bp constant. The relative position of a bp changes with respect to histone and the kinks appear and disappear at a position around the histone (colored gray).
Mosquitoes swarming around a source of a CO2 plume
In the spread of West Nile Virus, birds generate CO2 as they breathe and mosquitoes use Its concentration to eventually reach the birds and bite them. This process contributes to the spread of the virus. The image shows a simulated plume of CO2 concentration emanating from the left and being carried downstream to the right by the air. The mosquitoes have made their way close to the source. The colors indicate concentration levels.
Collaboration between CCS and the Tulane Department of Epidemiology.
The motility of sperm is dictated by the movement of the ﬂagellum, which changes in response to chemical cues. Activated motility is characterized by linear trajectories and hyperactivation is a motility pattern of mammalian sperm that is associated with highly asymmetrical ﬂagellar bending, leading to nonlinear tra jectories, including swimming in circles. It is necessary for the sperm to achieve hyperactivated motility in order to reach and fertilize the egg. Initiation and maintenance of hyperactivated motility is associated with a change in calcium concentration in the ﬂagellum. These pictures are trajectories of a material point on the sperm flagellum for t=0-4 s. In the model, we are accounting for CatSper mediated calcium dynamics, mechanics, and hydrodynamics. Each trajectory corresponds to a change in parameter values for the calcium threshold to change the amplitude or the passive stiffness. Using this model we are able to have trajectories characteristic of hyperactivated motility.
Blood Flow in A Giant Aneurysm
The blood flow in a giant vertebrobasilar junction aneurysm was numerically simulated with computational fluid dynamics (CFD) method. The streamlines of the blood flow indicated a large vortex structure existing inside the aneurysm. Strong jet flow effect was also observed which was caused by the asymmetric distribution of the flow rates between the left and right vertebro arteries. With this effect, a high static pressure region appeared on the aneurysm surface which corresponded to high risks of aneurysm rupture.
This is collaboration between the CCS, the Biomedical Engineering, and the Department of Chemical & Biomedical Engineering, Tulane University and the Department of Neurosurgery, LSU.
Lagrange Polynomials on Triangle
In high-order finite element method, the interpolation error depends on the collocation points used. On the left is a Lagrange polynomial based on a uniform grid, which equals 1 at the point (0.5,0.5) and vanishes at all other collocation points. The rapid oscillation of the function, known as Gibbs phenomena, indicates large interpolation error. On the right is a Lagrange polynomial based on a Lobatto grid, which shows much less interpolation error.
Flow Passes A Snowman
The flow over a model of snowman was computed using the IBAMR software package, which is a distributed-memory parallel implementation of the immersed boundary (IB) method with Cartesian grid adaptive mesh refinement (AMR). (https://code.nyu.edu/wiki/ibamr)
Center for Computational Science, Stanley Thomas Hall 402, New Orleans, LA 70118 email@example.com