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流体中速度场检测方案(粒子图像测速)

In the present study it is attempted to use the 3D time-resolved velocity field measurements obtained by employing a high-speed tomographic PIV system on a flat plate turbulent boundary layer at Reθ=730. The main objective of the study is the estimation of the wall pressure coherence function for the prediction of aeroacoustic noise radiated by boundary layers and trailing edge flows. The reconstruction of the pressure field from velocity field measurements follows the approach of de Kat and van Oudheusden (2012), whereby the Poisson equation is integrated over the measurement volume in 3D. Due to restriction on the extent of the measurement volume, uniform pressure is applied as boundary condition on stream- and spanwise faces. A direct numerical simulation of the boundary layer at a similar Reynolds number is performed in order to produce reference data for the velocity statistics and for the properties of the spectral fluctuations. The tomographic data agree very well with DNS as far as mean and fluctuating velocity components are concerned. Velocity field results are compared to 2C-PIV and the DNS solution and a collapse of the data is demonstrated. An additional reference measurement is introduced in order to validate the procedure of pressure determination from time-resolved tomographic PIV. Time series of pressure and the scaled power spectral density at a single point are compared to the DNS solution and results available from literature and good agreement is found. The correlation coefficient with respect to pinhole microphone measurements reaches a maximum value above 50% for data band-pass filtered between 250Hz and 3.5kHz. Finally, the coherence of the pressure fluctuations and the resulting spanwise coherence length are computed compared.
检测样品: 其他
检测项: 速度场

北京欧兰科技发展有限公司

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流体,湍动,边界层,流动中3D3C速度场,体视速度场,速度矢量场,速度场检测方案(粒子图像测速)

The spatial and temporal development of turbulent boundary layer flows is governed by the self-organization of coherent structures like hairpin-like or arch vortices and spanwise alternating wall bounded low- and highspeed streaks. For a detailed analysis of the topologies of the wall normal fluid exchange namely of the four quadrants of the instantaneous Reynolds stresses Q1,…,Q4 a 4D- measurement technique is desired. In this feasibility study the tomographic PIV technique (Elsinga et al. 2005) has been applied to time resolved PIV recordings. Four high speed CMOS cameras are imaging tracer particles which were illuminated in a volume inside a boundary layer flow at 4 kHz by using two high repetitive Nd:YAG pulse lasers. The instantaneously acquired single particle images of these cameras have been used for a three dimensional tomographic reconstruction of the light intensity distribution of the particle images in a volume of voxels (volume elements) virtually representing the measurement volume. Each of two subsequently acquired and reconstructed particle image distributions are cross-correlated in small interrogation volumes using iterative multi-grid schemes with volume-deformation in order to determine a time series of instantaneous 3D-3C velocity vector fields.
检测样品: 其他
检测项: 3D3C速度场,体视速度场,速度矢量场,速度场

北京欧兰科技发展有限公司

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