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Statistical Approach for BTT probes distribution
Mekhalfia, Mohammed Lamine ; Procházka, Pavel ; Šmíd, R. ; Tchawou Tchuisseu, Eder Batista
Blade tip timing (BTT) system is a non-invasive method used for measuring the blade tip timing of rotating machinery. The BTT system typically consists of sensor probes, signal conditioning system, and data acquisition unit. The sensor probes are placed in proximity to the rotating blade tips, Sensors measure the time at which each blade passes by the probe. By measuring the blade tip timing, the BTT system can detect changes in the blade tip vibration, which is an important for the health monitoring and performance optimization of rotating machinery [1]. To ensure accurate measurement of blade tip timing, the probe arrangement is crucial. The placement of the probe relative to the blade tips can affect the measurement accuracy, and thus, several arrangement algorithms have been developed to optimize the placement of the probes. Instead of considering the condition number, a statistical algorithms is followed to optimize the placement of probes for accurate measurement of blade tip timing in turbo-machinery. The statistical approach will be employed to determine the optimal locations for probes, with the aim of reducing errors in the measurement of blade tip timing. \n
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Assessment of Various Converging Inlet Nozzles for Wind Tunnel Using CFD
Kosiak, Pavlo ; Radnic, Tomáš ; Mamula, Milan ; Hála, Jindřich ; Šimurda, David ; Luxa, Martin
A new calibration tunnel intended for pressure probe calibration is being designed at the Aerodynamic Laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences (IT CAS). A critical part of the design is the converging nozzle since it can substantially affect the resulting flow field in the test section. Three types of nozzles were chosen for the CFD investigation: two-sine, Vitoshinski, and Vagt. For each type of nozzle, two configurations were considered: long (645 mm) and short (353mm). Flow of the viscous, compressible fluid through all the variants was simulated using Ansys CFX commercial software. Results proved the Vagt nozzle to have the most uniform velocity profile and zero curvature at its end making it the most suitable for the intended use.
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Investigation of Transonic Flow through Linear Cascade with Single Blade Incidence Angle Offset
Fürst, J. ; Musil, Josef ; Šimurda, David
The contribution deals with numerical and experimental investigation of the effect of incidence angle offset in a two-dimensional section of a flat linear blade cascade in a high-speed wind tunnel. The aim of the work is to complement ongoing research of quasi-stationary approximation of aerodynamic flutter by examination of setups leading to transonic flow regimes. The numerical simulations were realized by finite-volume, in-house code developed on top of the open-source software package OpenFOAM. The experiments were conducted in correspondence with the setting of numerical simulations. The comparison of experimental and numerical data is presented on the isentropic Mach number distributions at various locations in the blade cascade. The description of transonic flow structures in the vicinity of blades is also provided.
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Post-processing the results of the topology optimization with the level set technique
Ježek, Ondřej ; Kopačka, Ján ; Gabriel, Dušan
Topology optimization (TO) has come to the fore with the development of 3D printing. The most commonly used method is SIMP, a density-based approach, which outputs a per-element constant density field and thus requires post-processing to obtain the shape. Conventional post-processing methods extract optimized topologies in the form of brep models. It yields only C0 continuous geometries, which are usually not suitable for downstream applications such as prototyping, design validation, and design exploration. In this paper, we present a new post-processing method based on the level set principle that overcomes common post-processing issues, such as the lack of smoothness.
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The influence of first CNN layer initialization on training convergence
Krejsa, Jiří ; Věchet, Stanislav ; Chen, K.S.
During evaluation of convolution neural networks on the task of sign language single hand alphabet classification we have discovered that in small but not negligible number of cases the training of the network does not converge at all. This paper investigates the problem that we believe is independent of the application. While the true cause of training divergence was not discovered, we can offer the reader an easy solution from practical point of view – initialization of the first CNN layer using pretrained networks parameters.
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Effect of Cylinder Roughness on Strouhal Number
Yanovych, Vitalii ; Duda, D. ; Uruba, Václav ; Procházka, Pavel P. ; Antoš, Pavel
The main goal of this paper is to establish a better understanding of the relationship between a Strouhal number and surface roughness. Hot-wire anemometry was used to evaluations the characteristics of turbulent flow behind circular cylinders with different relative roughness 0% (smooth surface) 0.83%, 1.67%, 3.33%, and 6.67%. At the experimental investigation, the Reynolds number based on the cylinder diameter was 5 × 103 < Red < 2 × 104. The obtained data showed that the Strouhal number decreased with increasing roughness. While, the dissipation rate decreases, and the value of the Kolmogorov and Taylor microscales increases. Also, spectral analysis of streamwise velocity fluctuations allowed us to estimate the location of the vortex-shedding frequency which at growing roughness tends to reduce.
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Simple Rheoscopic Flows Used in Teaching Fluid Mechanics
Duda, D. ; Yanovych, Vitalii ; Uruba, Václav
Four simple demonstration experiments are presented. They are used as a support in the teaching of Fluid Mechanics I (a compulsory lecture at the University of West Bohemia in Pilsen). All mentioned experiments use the rheoscopic fluid obtained as a water solution of mica powder to visualize the flow in a esthetic way, which, as we hope, has a potential to attract students attention. The experiments are: demonstration of Bernoulli equation in a widening and narrowing channel, Taylor-Couette flow, the effect of viscosity to the scales and decay of turbulence, and the Galilean transformation inside an axial compressor.
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