Anti-PIV type 2, 3 Polyclonal antibody

A zonal hybrid unsteady Reynolds-averaged Navier-Stokes/large eddy simulation (URANS-LES) Zonal detached-eddy simulation (ZDES) model is applied to internal combustion engine (ICE) simulation and comparisons of predicted flow morphology and variability are carried out against on the transparent combustion chamber (TCC-III) particle image velocimetry (PIV) data set for motored conditions. To this aim, a previously developed model derived from a standard seamless-detached eddy simulation (DES) formulation is adopted for two different grid resolutions. In particular, two zonalization choices are evaluated based on previous single-grid results, in order to assess the model outcomes based on the joint turbulence treatment/grid density: the seamless-DES mode is applied (1) only to the cylinder (TCC-Z1) and (2) to the cylinder and intake port (TCC-Z2). Multi-cycle simulations (50 samples) are carried out and the results are compared to experimental data in terms of PIV images using multiple quality indices on multiple planes (Y= 0 andX= 0). Finally, comparison of predicted mean flow fields is extended to standard URANS mode. Results show that the use of a cylinder-only seamless-DES treatment on a relatively coarse grid results in a quantitative agreement between simulated and measured (PIV) flow fields, both in terms of average morphology and flow variability, whereas the extension of the DES mode to the intake port does not introduce relevant variations. Quality indicators seem to be moderately sensitive to the grid resolution, thus confirming the adaptive potential of a ZDES-like model and promoting the use of DES-type turbulence modelling even on relatively low-resolution grids. The analysis of average fields compared to URANS simulations highlights the benefit for both grids of a scale-resolving ZDES modelling when the same underlying turbulence model (k-epsilon RNG) is used. This study reinforces the recommendation in the use of hybrid URANS-LES models to simulate ICE flows. The adopted ZDES formulation based on the two-equationk-epsilon RNG model shows that high-quality results can be obtained even on engineering-grade grids, both in terms of average and cycle-to-cycle variation. The numerical results obtained using the two grids with variable resolution are consistent, and this further promotes a wider adoption of this class of models to simulate engine flows in industrial applications.

Optical photography and image analysis technology provide a non-intrusive and efficient research tool for the experimental research of multiphase bubbly flow. This paper presented a multi-frame image processing algorithm for measuring size and velocity of bubbles more accurately with bubble shadow images, especially in bubbly plume with serious overlapping in the bubble image. The raw images are the accurate recording of bubble shadow by high frequency CCD camera. In the shadow image, some of bubbles are isolated and others may overlap resulting in a complex geometric shape. It is easy to obtain the shape and centroid of isolated bubbles. But for the overlapping bubbles, additional effort should be made to detect each one from a cluster. And some of them are highly and completely overlapped, and may be lost during tracking. The main conception of the algorithm is based on the continuity of bubble movement to retrieve those bubbles. In one frame, a bubble which is highly or completely overlapped by others may appear alone in another frame. With the information of previous frames, the centroid and size of highly overlapping bubbles are predicted and then corrected according internal cores and edge information of bubble shadow. The algorithm is tested by artificial bubble images and further applied to the experiment of bubbly plume. It is proved that the algorithm performs well in recognition of bubbles and especially in determination of the size and velocity of bubbles in a cluster. For the artificial bubble images, the proposed algorithm successfully captures all bubbles including an inner bubble which cannot be detected in a single frame. For the experiment of bubbly plume, which is conducted in a tank with a 1 cm diameter nozzle at bottom and with the superficial gas velocity ranging from 31.8 to 53.1 mm/s, the effectiveness of the proposed method also reaches 95% by random sampling. For the case that more than half of bubbles are overlapped, the new algorithm can improve the recognition rate from 4% to 6% comparing with the primary algorithm without predictor-corrector method. (C) 2020 Elsevier Ltd. All rights reserved.