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1

Fuzzy-based prediction for suddenly expanded axisymmetric nozzle flows with microjets

Quadros Jaimon D., Suhas P., Khan Sher A., Aabid Abdul, Baig Muneer, Mogul Yakub I.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 5

art. no. e142654

EN

The current research focuses on the implementation of the fuzzy logic approach for the prediction of base pressure as a function of the input parameters. The relationship of base pressure (β ) with input parameters, namely, Mach number (M), nozzle pressure ratio (η), area ratio (α), length to diameter ratio (ξ ), and jet control (ϑ ) is analyzed. The precise fuzzy modeling approach based on Takagi and Sugeno’s fuzzy system has been used along with linear and non-linear type membership functions (MFs), to evaluate the effectiveness of the developed model. Additionally, the generated models were tested with 20 test cases that were different from the training data. The proposed fuzzy logic method removes the requirement for several trials to determine the most critical input parameters. This will expedite and minimize the expense of experiments. The findings indicate that the developed model can generate accurate predictions

2

Analytical dynamic model of coefficient of friction of air pipeline under pressure

Dmytriv Vasyl, Dmytriv Ihor, Horodetskyy Ivan, Dmytriv Taras

Diagnostyka

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2019

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Vol. 20, No. 4

89--94

EN

To transport of the air in the pipeline, an analytical model is developed that takes into account the gas velocity, its kinematic and dynamic characteristics - density, viscosity depending on the pressure in a given space of the pipeline. The analytical model makes it possible to calculate the coefficient of friction of gas transportation in the pipeline at intervals of the absolute pressure from 220 to 2 kPa and M < 1 Mach numbers, depending on the diameter and length of the pipeline and physical and technological characteristics of the gas. The K1* aspect ratio is proposed, which characterizes in time the ratio of the dynamic force of movement of gas to the static pressure related to the diameter of the pipeline. The coefficient of air friction was modeled according to the vacuum pressure as a parameter of density and air flow. Air flow was taken from 1.917·10-3 m 3/s to 44.5·10-3 m 3/s respectively, diameters from 0.030 to 0.070 m and Mach number was M = 0.005-0.13. At the vacuum and excess pressures with increasing of Reynolds number and decreasing of Mach number the gas friction coefficient increased linearly. According to the simulation results as the pressure loss and the diameter of the pipeline are increased the friction coefficient increased as well. Analogically, at the vacuum metric pressure when the pressure loss and the diameter of the pipeline are increased the friction coefficient increased. At the pipeline internal diameters of 22, 30, 36 mm accordingly for pressure losses from 2 to 14 kPa the coefficient of air friction varies from 0.006 to 54.527 respectively.

3

Nowe rozwiązania środków transportu na przykładzie kolei niskociśnieniowej

Rydzek Marcin

Autobusy : technika, eksploatacja, systemy transportowe

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2019

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R. 20, nr 6

116--119

PL

W pracy przedstawiono przyszłościowy środek lokomocji w postaci technologii kolei niskociśnieniowej - Hyperloop. Opisano stan obecny wdrażanej technologii oraz odniesiono się do problemów związanych prędkościami w tunelu próżniowym, gdzie jednym z podstawowych jest granica Kantrowitza. Montaż turbosprężarek ma temu zapobiec, lecz taka strategia jest zbyt kosztowna. Przedstawiona technologia może stanowić alternatywę dla obecnych środków transportu.

EN

The paper presents a forward-looking means of transport in the form of hyperloop technology. The paper describe current state of the implemented technology and refers to the problems related to speeds in a vacuum tunnel. The basic problem related to speed is the limit of Kantrowitz. The presented technology can be an alternative to the current means of transport.

4

Base pressure behaviour in a suddenly expanded duct at supersonic Mach number regimes using Taguchi design of experiments

Quadros J. D., Khan S. A., Antony A. J.

Mechanics and Mechanical Engineering

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2018

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Vol. 22, nr 4

1077--1097

EN

Experimental investigations are carried out to study the control of base pressure without and with the use of micro-jets through suddenly expanded axi-symmetric passage in the supersonic regime. Four micro jets having an orifice diameter of 1mm were located at 90˚ intervals. In the base area, active controls jets have been placed on a pitch of a circle diameter that is 1.3 times the exit diameter of the nozzle. The jets were dispensed abruptly into the axi-symmetric tube maintained at a cross-sectional area of 4.84 times the exit nozzle area. The variation of base pressure as a function of flow control parameters namely Mach number, nozzle pressure ratio (NPR) and length to diameter) ratio (L=D) are evaluated experimentally. This study also assesses the impact of flow control variables on base pressure for two cases viz. with control and without control respectively. An L9 orthogonal array of Taguchi and the analysis of variance were employed to investigate the percentage of contribution of these parameters and their interactions affecting the base pressure. The correlations between the various factors affecting the base pressure were obtained by using multiple linear regression equations. Confirmation tests were conducted in order to test the developed linear regression equations for their practical significance. Both the regression models were found to be significant and reliable with a percentage deviation lying in the range of -6:12% to 10.26% for base pressure without control and -13:92% to 6.58% for base pressure with control. Analysis of variance was also performed in order to determine the statistical significance of each parameter on the total variability of base pressure. The study concluded that Mach number is the most in fluential parameter affecting base pressure followed by NPR and L=D.

5

Study of base pressure behavior in a suddenly expanded duct at supersonic Mach number regimes using statistical analysis

Quadros J. D., Khan S. A., Antony A. J.

Journal of Applied Mathematics and Computational Mechanics

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2018

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Vol. 17, nr 4

59--72

EN

The present experimental evaluation deals with the behavior of base pressure (BP) in a suddenly expanded duct at supersonic Mach number regimes. The experiments have been conducted for two cases viz. Without and with the use of microjets or active control. The plan of experiments was planned as per Taguchi design of experiments for acquiring data in a controlled manner. An L27 orthogonal array and analysis of variance (ANOVA) has been employed to investigate the contribution (in terms of percentage) of distinct process parameters like Mach number (M), Nozzle Pressure Ratio (N), Area Ratio (A) and their interactions affecting base pressure. The correlation between these parameters affecting base pressure has been obtained using multiple linear regression analysis. It has been concluded that the Mach number and area ratio were the factors that had high statistical significance on the behavior of base pressure for both cases. The performances of the developed linear regression models have been validated for accuracy prediction by use of 15 test cases. The performance of both the base pressure models was found to be better with percentage prediction in deviation lying in the range of –12.92% to +15.88% for base pressure without control and –10.27% to +19.23% for base pressure with control.

6

Low Mach number model for investigation of 3D flows

Zieliński A., Tuliszka-Sznitko E.

Archives of Thermodynamics

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2008

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Vol. 29, no. 3

25-36

EN

In the present paper a computational algorithm based on the low Mach number model is proposed to investigate strongly 3D flow in the rotating cavity with heat exchange. Algorithm is based on a paper by Ouazzani and Garrabos [1]. For the spatial approximation an efficient pseudo-spectral Chebyshev-Fourier method is used [2]. Algorithm was verified by comparing the results with these obtained using the Boussinesq fluid.

7

Modelowanie nieustalonych sił aerodynamicznych

Nowak M.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2000

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nr 117, vol. 1

85-90

PL

Znajomość zlinearyzowanych nieustalonych sil aerodynamicznych (czyli tzw. funkcji aerodynamicznej transmitancji operatorowej) odpowiadających małym zaburzeniom ruchu konstrukcji lub podmuchom, jest istotna dla analizy stabilności mchu układów aeroelastycznych. Na podstawie wyników obliczeń numerycznych oraz rozważań teoretycznych, zaproponowano ogólną postać liniowego (dyskretnego) operatora aerodynamicznego w dziedzinach Laplace* a i czasu, dla dwu- i trojwvmiarowveh nieustalonych oplywów poddźwiekowych. Jest on w pewnym sensie uogólnieniem znanego rozwiązania Theodorsena dla profilu w przepływie nieściśliwym.

EN

The knowledge of linearized unsteady aerodynamic forces i.e. the aerodynamic transfer matrices related to small structural motion and gusts, is essential for stability analyses of aeroelastic systems. On the basis of numerical results and theoretical considerations, a general form of the (unsteady) linear, discretized aerodynamic operator in the Laplace- and in the time-domain, for two- and three-dimensional subsonic flow is proposed. It corresponds to the classical Theodorsen solution lor an airfoil in incompressible flow.

8

A new formulation of the local reflection theory of an oblique shock wave at a rigid wall

Łęgowski Z.

Journal of Technical Physics

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2000

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Vol. 41, no 4

411-428

EN

A complete solution to the local theory of the shock wave reflection at an inclined wall has been obtained for the first time in two particular regions. One is the region near the Mach stem confluence S point with the wall and the other in the vicinity of the triple point T of an irregular shock-wave configuration. The correct lines of regular-irregular transitions have been established for the self-similar reflection problem in shock tubes. The solutions for all shock-fronts geometry have been obtained in the vicinity of the triple point, which are in agreement with the results of experimental measurements. In all the region of interaction the backward-reflected shock waves have been obtained for incident waves of arbitrary intensity. It has been formulated the hypothesis concerning the regular-irregular transition of weak shock waves, as a result of disintegration of an arbitrary discontinuity formed at the terminal stage of regular reflection.

9

Shock-induced dynamics of an elastically turbine cascade at transonic flow

Urban B., Stetter H., Vortmeyer N.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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1999

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nr 115

387--396

EN

This paper presents experimental investigations on shock-induced flutter in a linear transonic turbine cascade. To examine these phenomena, an elastic suspension system has been developed so that only aerodynamic coupling occurs. The profiles are typical for the tip section of a transonic low pressure steam turbine last stage. The examination at the two-dimensional test rig with superheated steam as working fluid mainly deals with the oscillatory behaviour of the blades with respect to a variation of the isentropic outlet Mach number. In addition, the complex shockboundary layer interactions on the blades' suction sides are described.

10

Absolute instability in the compressible three dimensional boundary layer

Tuliszka-Sznitko E.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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1998

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z. 7

453-458

EN

In the present paper the character of instability of compressible three dimensional viscous flow is analyzed. Following the works of Briggs and Bers in the field of plasm a physics - , the absolute instability region is identified by singularities of dispersion relation called pinch - points . Regions of absolute instability in boundary layers of a rotating cone have be n found . Calculations have been made for different Mach numbers , wall temperatures and rotational speeds of the cone.

PL

Badany jest charakter niestabilności przepływu ściśliwego, lepkiego i trójwymiarowego . Zastosowano kryterium Briggsa i Bersana niestabilność absolutną zgodnie z którym o charakterze niestabilności decydują osobliwość i funkcji dyspersji . Obliczenia przeprowadzono dla stożka wirującego w przepływie jednorodnym. Badano wpływ liczby Macha , temperatury ścianki oraz liczby Reynoldsa crossflow na obszary absolutnie niestabilne.