Heat Transfer across the Free Surface of a Thermocapillary Liquid Bridge

The heat transfer across the free surface of a millimetric thermocapillary liquid bridge is investigated for two dimensional axisymmetric flows, computed by Newton–Raphson iteration. The coupled multiphase flow in the silicone-oil liquid bridge and in the ambient gas (air) is considered for Marangoni and Prandtl numbers of interest for typical space experiments. Based on the space-resolved heat flux of the two-phase flow for a wide range of parameters, we derive a model for the heat flux in form of Newton’s heat transfer law for a surrogate single phase flow, in which a space-dependent Biot function is considered. A parametric study for a 2 St silicone-oil liquid bridge is conducted for 150 configurations to derive a reliable fit of the Biot function for a wide range of Reynolds numbers and aspect ratios. An explicit form of the parametric fit is provided which takes into account the hot- and cold-wall boundary layers in the liquid

Experimental investigation of transitional flow in a toroidal pipe

The flow instability and further transition to turbulence in a toroidal pipe (torus) with curvature ratio (tube-to-coiling diameter) 0.049 is investigated experimentally. The flow inside the toroidal pipe is driven by a steel sphere fitted to the inner pipe diameter. The sphere is moved with constant azimuthal velocity from outside the torus by a moving magnet. The experiment is designed to investigate curved pipe flow by optical measurement techniques. Using stereoscopic particle image velocimetry, laser Doppler velocimetry and pressure drop measurements, the flow is measured for Reynolds numbers ranging from 1000 to 15 000. Time- and space-resolved velocity fields are obtained and analysed. The steady axisymmetric basic flow is strongly influenced by centrifugal effects. On an increase of the Reynolds number we find a sequence of bifurcations. For $\mathit{Re}= 4075\pm 2\hspace{0.167em} \%$ a supercritical bifurcation to an oscillatory flow is found in which waves travel in the streamwise direction with a phase velocity slightly faster than the mean flow. The oscillatory flow is superseded by a presumably quasi-periodic flow at a further increase of the Reynolds number before turbulence sets in. The results are found to be compatible, in general, with earlier experimental and numerical investigations on transition to turbulence in helical and curved pipes. However, important aspects of the bifurcation scenario differ considerabl

Three-dimensional flow instability in a lid-driven isosceles triangular cavity

Linear three-dimensional modal instability of steady laminar two-dimensional states developing in a lid-driven cavity of isosceles triangular cross-section is investigated theoretically and experimentally for the case in which the equal sides form a rectangular corner. An asymmetric steady two-dimensional motion is driven by the steady motion of one of the equal sides. If the side moves away from the rectangular corner, a stationary three-dimensional instability is found. If the motion is directed towards the corner, the instability is oscillatory. The respective critical Reynolds numbers are identified both theoretically and experimentally. The neutral curves pertinent to the two configurations and the properties of the respective leading eigenmodes are documented and analogies to instabilities in rectangular lid-driven cavities are discussed

Potential for classical biological control of the potato bug Closterotomus norwegicus (Hemiptera: Miridae): description, parasitism and host specificity of Peristenus closterotomae sp. n. (Hymenoptera: Braconidae)

The potato bug, Closterotomus norwegicus (Gmelin) (Hemiptera: Miridae) is an introduced pest of lucerne, white clover and lotus seed crops in New Zealand and a key pest of pistachios in California, USA. Efforts were made to identify potential biological control agents of C. norwegicus in Europe. A total of eight parasitoids, including six primary parasitoids from the genus Peristenus (Hymenoptera: Braconidae) and two hyperparasitoids from the genus Mesochorus (Hymenoptera: Ichneumonidae), were reared from C. norwegicus nymphs collected in various habitats in northern Germany. With a proportion of more than 85% of all C. norwegicus parasitoids, Peristenus closterotomae (Hymenoptera: Braconidae), a new species, was the most dominant parasitoid, whereas other parasitoid species only occurred sporadically. Peristenus closterotomae did not fit in the keys to any described species and is described as new to science. Parasitism caused by P. closterotomae was on average 24% (maximum 77%). To assess the host specificity of parasitoids associated with C. norwegicus, the parasitoid complexes of various Miridae occurring simultaneously with C. norwegicus were studied. Peristenus closterotomae was frequently reared from Calocoris affinis (Herrich-Schaeffer), and a few specimens were reared from Calocoris roseomaculatus (De Geer) and the meadow plant bug, Leptopterna dolobrata (Linnaeus) (all Hemiptera: Miridae). The remaining primary parasitoids associated with C. norwegicus were found to be dominant in hosts other than C. norwegicus. Whether nymphal parasitoids may potentially be used in a classical biological control initiative against the potato bug in countries where it is introduced and considered to be a pest is discusse

AUTOMATIC IN-SITU SELF-CALIBRATION OF A PANORAMIC TLS FROM A SINGLE STATION USING 2D KEYPOINTS

Terrestrial laser scanner (TLS) measurements are unavoidably affected by systematic influences due to internal misalignments. The magnitude of the resulting errors can exceed the magnitude of random errors significantly deteriorating the quality of the obtained point clouds. Hence, the task of calibrating TLSs is important for applications with high demands regarding accuracy. In recent years, multiple in-situ self-calibration approaches were derived allowing the successful estimation of up-to-date calibration parameters. These approaches rely either on using manually placed targets or on using man-made geometric objects found in surroundings. Herein, we widen the existing toolbox with an alternative approach for panoramic TLSs, for the cases where such prerequisites cannot be met. We build upon the existing target-based two-face calibration method by substituting targets with precisely localized 2D keypoints, i.e. local features, detected in panoramic intensity images using the Förstner operator. To overcome the detriment of the perspective change on the feature localization accuracy, we estimate the majority of the relevant calibration parameters from a single station. The approach is verified on real data obtained with the Leica ScanStation P20. The obtained results were tested against the affirmed target-based two-face self-calibration. Analysis proved that the estimated calibration parameters are directly comparable both in the terms of parameter precision and correlation. In the end, we employ an effective evaluation procedure for testing the impact of the calibration results on the point cloud quality

The JEREMI-project on thermocapillary convection in liquid bridges. Part A : Overview of particle accumulation structures

The rapid accumulation of particles suspended in a thermocapillary liquid bridge is planned to be investigated during the JEREMI experiment on the International Space Station scheduled for 2016. An overview is given of the current status of experimental and numerical investigations of this phenomenon

The Luminosity Function Of Field Galaxies And Its Evolution Since z=1

We present the B-band luminosity function and comoving space and luminosity densities for a sample of 2779 I-band selected field galaxies based on multi-color data from the CADIS survey. The sample is complete down to I_815 = 22 without correction and with completeness correction extends to I_815=23.0. By means of a new multi-color analysis the objects are classified according to their spectral energy distributions (SEDs) and their redshifts are determined with typical errors of delta z <= 0.03. We have split our sample into four redshift bins between z=0.1 and z=1.04 and into three SED bins E-Sa,Sa-Sc and starbursting (emission line) galaxies. The evolution of the luminosity function is clearly differential with SED. The normalization phi* of luminosity function for the E-Sa galaxies decreases towards higher redshift, and we find evidence that the comoving galaxy space density decreases with redshift as well. In contrast, we find phi* and the comoving space density increasing with redshift for the Sa-Sc galaxies. For the starburst galaxies we find a steepening of the luminosity function at the faint end and their comoving space density increases with redshift.Comment: 15 pages, 14 figures, accepted by Astronomy&Astrophysic

Development of a custom OMI NO2 data product for evaluating biases in a regional chemistry transport model

In this paper, we present the custom Hong Kong NO2 retrieval (HKOMI) for the Ozone Monitoring Instrument (OMI) on board the Aura satellite which was used to evaluate a high-resolution chemistry transport model (CTM) (3 km x 3 km spatial resolution). The atmospheric chemistry transport was modelled in the Pearl River Delta (PRD) region in southern China by the Models-3 Community Multiscale Air Quality (CMAQ) modelling system from October 2006 to January 2007. In the HKOMI NO2 retrieval, tropospheric air mass factors (AMFs) were recalculated using high-resolution ancillary parameters of surface reflectance, a priori NO2 and aerosol profiles, of which the latter two were taken from the CMAQ simulation. We tested the influence of the ancillary parameters on the data product using four different aerosol parametrizations. Ground-level measurements by the PRD Regional Air Quality Monitoring (RAQM) network were used as additional independent measurements. The HKOMI retrieval increases estimated tropospheric NO2 vertical column densities (VCD) by (+31 +/- 38) %,when compared to NASA's standard product (OMNO2-SP),and improves the normalized mean bias (NMB) between satellite and ground observations by 26 percentage points from -41 to -15 %. The individual influences of the parameters are (+11.4 +/- 13.4)% for NO2 profiles,(+11.0 +/- 20.9)% for surface reflectance and (+6.0 +/- 8.4)% for the best aerosol parametrization. The correlation coefficient r is low between ground and satellite observations (r = 0.35). The low r and the remaining NMB can be explained by the low model performance and the expected differences when comparing point measurements with area-averaged satellite observations. The correlation between CMAQ and the RAQM network is low (r approximate to 0.3) and the model underestimates the NO2 concentrations in the northwestern model domain (Foshan and Guangzhou). We compared the CMAQ NO2 time series of the two main plumes with our best OMI NO2 data set (HKOMI-4). The model overestimates the NO2 VCDs by about 15% in Hong Kong and Shenzhen, while the correlation coefficient is satisfactory (r = 0.56). In Foshan and Guangzhou, the correlation is low (r = 0.37) and the model underestimates the VCDs strongly (NMB = -40 %). In addition, we estimated that the OMI VCDs are also underestimated by about 10 to 20% in Foshan and Guangzhou because of the influence of the model parameters on the AMFs. In this study, we demonstrate that the HKOMI NO2 retrieval reduces the bias of the satellite observations and how the data set can be used to study the magnitude of NO2 concentrations in a regional model at high spatial resolution of 3 x 3 km(2). The low bias was achieved with recalculated AMFs using updated surface reflectance, aerosol profiles and NO2 profiles. Since unbiased concentrations are important, for example, in air pollution studies, the results of this paper can be very helpful in future model evaluation studies