scholarly journals Numerical and experimental studies on the influences of flow field on the measurement accuracy of ultrasonic water meters

2021 ◽  
Vol 18 ◽  
pp. 100137
Author(s):  
Jieqiang Ji ◽  
Jianying Zheng ◽  
GuoFu Chen ◽  
Xiaojie Wu ◽  
NingNing Zhang ◽  
...  
Keyword(s):  
Flow Field ◽  
Measurement Accuracy ◽  
Experimental Studies ◽  
Water Meters

scholarly journals Performance Analysis of Surface Reconstruction Algorithms in Vertical Scanning Interferometry Based on Coherence Envelope Detection

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 164
Author(s):  
Dongxu Wu ◽  
Fusheng Liang ◽  
Chengwei Kang ◽  
Fengzhou Fang
Keyword(s):  
Surface Reconstruction ◽  
Measurement Accuracy ◽  
Experimental Studies ◽  
Reconstruction Algorithm ◽  
Low Noise ◽  
Surface Measurement ◽  
Reconstruction Algorithms ◽  
Centroid Method ◽  
Envelope Detection ◽  
Vertical Scanning Interferometry

Optical interferometry plays an important role in the topographical surface measurement and characterization in precision/ultra-precision manufacturing. An appropriate surface reconstruction algorithm is essential in obtaining accurate topography information from the digitized interferograms. However, the performance of a surface reconstruction algorithm in interferometric measurements is influenced by environmental disturbances and system noise. This paper presents a comparative analysis of three algorithms commonly used for coherence envelope detection in vertical scanning interferometry, including the centroid method, fast Fourier transform (FFT), and Hilbert transform (HT). Numerical analysis and experimental studies were carried out to evaluate the performance of different envelope detection algorithms in terms of measurement accuracy, speed, and noise resistance. Step height standards were measured using a developed interferometer and the step profiles were reconstructed by different algorithms. The results show that the centroid method has a higher measurement speed than the FFT and HT methods, but it can only provide acceptable measurement accuracy at a low noise level. The FFT and HT methods outperform the centroid method in terms of noise immunity and measurement accuracy. Even if the FFT and HT methods provide similar measurement accuracy, the HT method has a superior measurement speed compared to the FFT method.

scholarly journals Optical Inspection Systems for Axisymmetric Parts with Spatial 2D Resolution

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1218
Author(s):  
Aleksandr Kulchitskiy
Keyword(s):  
Control System ◽  
Optical System ◽  
Measurement Accuracy ◽  
Experimental Studies ◽  
Digital Camera ◽  
Digital Cameras ◽  
Bodies Of Revolution ◽  
Optical Inspection ◽  
Inspection Systems ◽  
Projection Error

The article proposes a solution to the problem of increasing the accuracy of determining the main shaping dimensions of axisymmetric parts through a control system that implements the optical method of spatial resolution. The influence of the projection error of a passive optical system for controlling the geometric parameters of bodies of revolution from the image of its sections, obtained by a digital camera with non-telecentric optics, on the measurement accuracy is shown. Analytical dependencies are derived that describe the features of the transmission of measuring information of a system with non-telecentric optics in order to estimate the projection error. On the basis of the obtained dependences, a method for compensating the projection error of the systems for controlling the geometry of the main shaping surfaces of bodies of revolution has been developed, which makes it possible to increase the accuracy of determining dimensions when using digital cameras with a resolution of 5 megapixels or more, equipped with short-focus lenses. The possibility of implementing the proposed technique is confirmed by the results of experimental studies.

Experimental Investigation Into the Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Andreas Krug ◽  
Peter Busse ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Experimental Studies ◽  
Axial Compressor ◽  
Field Measurements ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Unsteady Interaction ◽  
Linear Compressor Cascade ◽  
Tip Clearance Vortex ◽  
The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex (TCV) and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step toward the characterization of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analyzed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. This paper focuses on experimental studies conducted at the newly designed low-speed cascade wind tunnel in Dresden. The general tunnel configuration and details on the specific cascade setup will be presented. Steady state flow field measurements were carried out using five-hole probe traverses up- and downstream of the cascade and accompanied by static wall pressure readings. 2D-particle image velocimetry (PIV) measurements complemented these results by visualizing the blade-to-blade flow field. Hence, the structure of the evolving secondary flow system is evaluated and compared for all tested configurations.

scholarly journals Hydrodynamics of Regular Breaking Wave

2020 ◽  
Author(s):  
Diana De Padova ◽  
Michele Mossa
Keyword(s):  
Flow Field ◽  
Surf Zone ◽  
Laser Doppler Anemometry ◽  
Single Point ◽  
Measurement Techniques ◽  
Experimental Studies ◽  
Outer Region ◽  
Breaking Wave ◽  
Measured Velocity ◽  
Spatial Gradients

Turbulence and undertow currents play an important role in surf-zone mixing and transport processes; therefore, their study is fundamental for the understanding of nearshore dynamics and the related planning and management of coastal engineering activities. Pioneering studies qualitatively described the features of breakers in the outer region of the surf zone. More detailed information on the velocity field under spilling and plunging breakers can be found in experimental works, where single-point measurement techniques, such as Hot Wire Anemometry and Laser Doppler Anemometry (LDA), were used to provide maps of the flow field in a time-averaged or ensemble-averaged sense. Moreover, the advent of non-intrusive measuring techniques, such as Particle Image Velocimetry (PIV) provided accurate and detailed instantaneous spatial maps of the flow field. However, by correlating spatial gradients of the measured velocity components, the instantaneous vorticity maps could be deduced. Moreover, the difficulties of measuring velocity due to the existence of air bubbles entrained by the plunging jet have hindered many experimental studies on wave breaking encouraging the development of numerical model as useful tool to assisting in the interpretation and even the discovery of new phenomena. Therefore, the development of an WCSPH method using the RANS equations coupled with a two-equation k–ε model for turbulent stresses has been employed to study of the turbulence and vorticity distributions in in the breaking region observing that these two aspects greatly influence many coastal processes, such as undertow currents, sediment transport and action on maritime structures.

Experimental Studies of the Primary Zone Flow Field and Combustion Performance of a Triple Swirler Combustor

2005 ◽  
Author(s):  
Yunhui Peng ◽  
Quanhong Xu ◽  
Yuzhen Lin
Keyword(s):  
Flow Field ◽  
Experimental Studies ◽  
Fuel Injector ◽  
Lean Blowout ◽  
Combustion Performance ◽  
Primary Zone ◽  
Image Velocimetry ◽  
Aero Engine ◽  
Exit Temperature ◽  
Promising Solution

Improvement of the lean blowout limit and more uniform combustor exit temperature distribution are particularly desirable for future aero engine. A triple swirler combination plus an airblast fuel injector might be a promising solution. The design with the triple swirler plus the airblast fuel injector including design A and B was presented and investigated in this paper. Single rectangle sector module combustor was used in the experiment for lean blowout (LBO), and three cups rectangle sector combustor was used for pattern factor (PF) experiments. The LBO and PF experiment data were provided. The primary zone flow field was measured by PIV (Particle Image Velocimetry) under atmospheric pressure and temperature. The result showed that the design A was a promising design, and the primary jet played very important role for flow field of primary zone. The insight relation between flow field and combustion performance could be found out from this paper.

A numerical investigation of the Stokes boundary layer in the turbulent regime

2007 ◽  
Vol 570 ◽  
pp. 253-296 ◽  
Author(s):  
S. SALON ◽  
V. ARMENIO ◽  
A. CRISE
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Time Scale ◽  
Mixed Model ◽  
Experimental Studies ◽  
Outer Region ◽  
Transition To Turbulence ◽  
Turbulent Regime ◽  
Turbulent Statistics ◽  
Acceleration And Deceleration

The Stokes boundary layer in the turbulent regime is investigated by using large-eddy simulations (LES). The Reynolds number, based on the thickness of the Stokes boundary layer, is set equal to Reδ = 1790, which corresponds to test 8 of the experimental study of Jensen et al. (J. Fluid Mech. vol. 206, 1989, p. 265).Our results corroborate and extend the findings of relevant experimental studies: the alternating phases of acceleration and deceleration are correctly reproduced, as is the sharp transition to turbulence, observable at a phase angle between 30° and 45°, and its maximum between 90° and 105°. Overall, a very good agreement was found between our LES first- and second-order turbulent statistics and those of Jensen et al. (1989). Some discrepancies were observed when comparing turbulent intensities in the phases of the cycle characterized by a low level of turbulent activity.In the central part of the cycle, namely from the mid acceleration to the late deceleration phases, fully developed equilibrium turbulence is present in the flow field, and the boundary layer resembles that of a canonical, steady, wall-bounded flow. In those phases characterized by low turbulent activity, two separate regions can be detected in the flow field: a near-wall one, where the vertical turbulent kinetic energy varies much more rapidly than the other two components, thus giving rise to the formation of horizontal, pancake-like turbulence; and an outer region where both vertical and spanwise velocity fluctuations vary much faster than the streamwise ones, hence producing cigar-like turbulence.As a side result, the range of application of the plane-averaged dynamic mixed model was assessed based on the qualitative behaviour over the cycle of a significant parameter representing the ratio between a turbulent time scale and a free-stream time scale associated with the oscillatory motion.

The Growth of Vortices in the Vicinity of a Wall of Elastic Moving Airfoils

2013 ◽  
Author(s):  
Masaki Fuchiwaki ◽  
Tomoki Kurinami ◽  
Kazuhiro Tanaka
Keyword(s):  
Flow Field ◽  
Elastic Body ◽  
Elastic Deformation ◽  
Growth Process ◽  
Experimental Studies ◽  
Strain Component ◽  
Pitching Airfoil ◽  
The Impact ◽  
The Relationship ◽  
Significant Attention

There have been a number of studies on the flow field around a pitching airfoil and a heaving airfoil. Especially, the relationship between the wake structure and the characteristics of dynamic thrust has been clarified. Recently, the flow field around an elastic body has been attracted significant attention and the flow field is treated as a coupled problem between the fluid and structure. The flow field around an elastic body has been investigated primarily by numerical means, and there have been experimental studies. However, the details of the impact of elastic deformation effects on the growth process of vortices generated in the vicinity of the wall have not been clarified. In this study, we investigate the growth process of vortices generated in the vicinity of the wall of elastic moving airfoils experimentally. The elastic NACA0010 generates vortices in a large region of a wall and rolls up vortices, with the vortices growing gradually toward the trailing edge as a result of elastic deformation. The elastic NACA0010 has a characteristic whereby vortices having a rotational component that is stronger than the shear-strain component due to the vorticities in the vicinity of a wall of the elastic NACA0010 change not only spatial change of x- and y-components.

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