11,212 research outputs found
Laser transit anemometer measurements on a slender cone in the Langley unitary plan wind tunnel
A laser transit anemometer (LTA) system was used to probe the boundary layer on a slender (5 degree half angle) cone model in the Langley unitary plan wind tunnel. The anemometer system utilized a pair of laser beams with a diameter of 40 micrometers spaced 1230 micrometers apart to measure the transit times of ensembles of seeding particles using a cross-correlation technique. From these measurements, boundary layer profiles around the model were constructed and compared with CFD calculations. The measured boundary layer profiles representing the boundary layer velocity normalized to the edge velocity as a function of height above the model surface were collected with the model at zero angle of attack for four different flow conditions, and were collected in a vertical plane that bisected the model's longitudinal center line at a location 635 mm from the tip of the forebody cone. The results indicate an excellent ability of the LTA system to make velocity measurements deep into the boundary layer. However, because of disturbances in the flow field caused by onboard seeding, premature transition occurred implying that upstream seeding is mandatory if model flow field integrity is to be maintained. A description and results of the flow field surveys are presented
Some comments on particle image displacement velocimetry
Laser speckle velocimetry (LSV) or particle image displacement velocimetry, is introduced. This technique provides the simultaneous visualization of the two-dimensional streamline pattern in unsteady flows as well as the quantification of the velocity field over an entire plane. The advantage of this technique is that the velocity field can be measured over an entire plane of the flow field simultaneously, with accuracy and spatial resolution. From this the instantaneous vorticity field can be easily obtained. This constitutes a great asset for the study of a variety of flows that evolve stochastically in both space and time. The basic concept of LSV; methods of data acquisition and reduction, examples of its use, and parameters that affect its utilization are described
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Microfluidic Platform for Adherent Single Cell High-Throughput Screening
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Traditionally, in vitro investigations on biology and physiology of cells rely on averaging the
responses eliciting from heterogeneous cell populations, thus being unsuitable for assessing individual cell
behaviors in response to external stimulations. In the last years, great interest has thus been focused on single
cell analysis and screening, which represents a promising tool aiming at pursuing the direct and deterministic
control over cause-effect relationships guiding cell behavior. In this regard, a high-throughput microfluidic
platform for trapping and culturing adherent single cells was presented. A single cell trapping mechanism
was implemented based on dynamic variation of fluidic resistances. A round-shaped culture chamber
(Φ=250μm, h=25μm) was conceived presenting two connections with a main fluidic path: (i) an upper wide
opening, and (ii) a bottom trapping junction which modulates the hydraulic resistance. Several layouts of the
chamber were designed and computationally validated for the optimization of the single cell trapping
efficacy. The optimized chamber layouts were integrated in a polydimethylsiloxane (PDMS) microfluidic
platform presenting two main functionalities: (i) 288 chambers for trapping single cells, and (ii) a chaoticmixer
based serial dilution generator for delivering both soluble factors and non-diffusive molecules under
spatio-temporally controlled chemical patterns. The devices were experimentally validated and allowed for
trapping individual U87-MG (human glioblastoma-astrocytoma epithelial-like) cells and culturing them up to
3 days
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