31,606 research outputs found
The structure of separated flow regions occurring near the leading edge of airfoils, including transition
The structure and behavior of the separation bubble including transition and the redeveloping boundary layer after reattachment over an airfoil at low Reynolds numbers was studied. The intent is to further the understanding of the complex flow phenomena so that analytic methods for predicting their formation and development can be improved. These analytic techniques have applications in the design and performance prediction of airfoils operating in the low Reynolds number flight regime
Laser velocimetry measurement in a transonic tunnel
Some preliminary velocity measurements were carried out inside the transonic tunnel using the laser velocimeter (LV) system in association with the smoke generator. Pressure measurements were also performed using a pressure tap located on the side wall of the test section slightly upstream of the windows. Though the pressure measurements and the LV measurements were not taken at exactly the same location, extrapolation of the pressure data into the location of the LV measurements indicated a very close agreement between the velocity values obtained using the two different methods. Thus it is believed that the smoke particle is following the air flow with little or no velocity slip. Velocity measurements with airfoil at various angles of attack are now being carried out in conjuction with schlieren flow visualization. In the near future pressure distribution around and on the airfoil will be obtained by putting pressure taps on the side windows and using a pressure tap model (currently under construction) of the airfoil
Free-Knot Spline Approximation of Stochastic Processes
We study optimal approximation of stochastic processes by polynomial splines
with free knots. The number of free knots is either a priori fixed or may
depend on the particular trajectory. For the -fold integrated Wiener process
as well as for scalar diffusion processes we determine the asymptotic behavior
of the average -distance to the splines spaces, as the (expected) number
of free knots tends to infinity.Comment: 23 page
Monte Carlo Simulation of Long Chain Polymer Melts: Crossover from Rouse to Reptation Dynamics
We present data of Monte Carlo simulations for monodisperse linear polymer
chains in dense melts with degrees of polymerization between N=16 and N=512.
The aim of this study is to investigate the crossover from Rouse-like dynamics
for short chains to reptation-like dynamics for long chains. To address this
problem we calculate a variety of different quantities: standard mean-square
displacements of inner monomers and of the chain's center of mass, the recently
proposed cubic invariant, persistence of bond-vector orientation with time, and
the auto-correlation functions of the bond vector, the end-to-end vector and
the Rouse modes. This analysis reveals that the crossover from non- to
entangled dynamics is very protracted. Only the largest chain length N=512,
which is about 13 times larger than the entanglement length, shows evidence for
reptation.Comment: 38 pages of REVTeX, 14 PostScript figure
Soil moisture detection from radar imagery of the Phoenix, Arizona test site
The Environmental Research Institute of Michigan (ERIM) dual-polarization X and L band radar was flown to acquire radar imagery over the Phoenix (Arizona) test site. The site was covered by a north-south pass and an east-west pass. Radar response to soil moisture was investigated. Since the ERIM radar does not have accurately measured antenna patterns, analysis of the L band data was performed separately for each of several strips along the flight line, each corresponding to a narrow angle of incidence. For the NS pass, good correlation between the radar return and mositure content was observed for each of the two nearest (to nadir) angular ranges. At higher angular ranges, no correlation was observed. The above procedure was not applied to the EW pass due to flight path misalignments. The results obtained stress the importance of radar calibration, the digitization process, and the angle of incidence
ADJOINT BASED DESIGN OPTIMISATION OF AN INTERNAL COOLING CHANNEL U-BEND FOR MINIMIZED PRESSURE LOSSES
The aim of this paper is to reduce the pressure losses of a U-bend passage of a turbine blade serpentine cooling channel. A steady state Reynolds-Averaged density based Navier-Stokes solver is used to predict the pressure losses at a Reynolds number of 40,000. A novel geometry representation approach is used defining directly the volume of the passage rather than its exterior boundary, which is now the most common approach in CAD systems. The U-bend volume is parameterised using tri-variate B-splines, the deformations of the shape are controlled by the external control points of the B-spline volume, while the internal control points are repositioned using a transfinite interpolation to ensure a smooth and regular internal representation of the shape. This approach ensures a good grid regularity at a large reduced computational cost compared to traditional approaches. The sensitivities of the control points with respect to the objective function are computed using a hand-derived adjoint solver and geometry generation system. A one-shot approach is used to simultaneously converge flow, gradient and design, resulting in a rapid design approach with a design time equivalent to approximately 10 normal CFD runs. A large reduction in pressure loss is obtained, and the optimal geometry is analysed in more detail
Theological Observer. - Kirchlich-Zeitgeschichtliches
Theological Observer. – Klrchllch Zeitgeschichtliches (Theological Observer. – Of course contemporary history
Theological Observer. – Kirchlich Zeitgeschichtliches
Theological Observer. – Klrchllch Zeitgeschichtliches (Theological Observer. – Of course contemporary history
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