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1

Method for assessing the dynamics and efficiency of diving fins

Grządziela Andrzej, Szymak Piotr, Piskur Paweł

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 4

139--150

EN

This article presents a method for an evaluation of the dynamic ability and efficiency of diving fins. There is paucity in the literature on the process of selecting optimal fins. As a result, there are efforts made to develop a methodology for selecting fins that meet the proposed criteria. In the present study, an analysis on the two types of fins most popular within the commercial market was conducted. The experiment took place in a test water tunnel fully equipped with a measuring system and strain gauges for recording forced interaction between the moving fin and flowing water. The tested fins rested on an artificial leg, which moved respectively, thereby developing movement algorithms. This forced fluid flow was implemented by a pump that was able to control the fluids velocity, and a non-invasive method involving an ultrasonic flow meter was used to measure the fluids velocity. Finally, the fin efficiency was calculated as the ratio of multiplication of generated thrust to electrical energy consumption whilst also considering the mechanical efficiency of the leg manipulator. The results of these experiments are discussed in depth and a method is created for the subsequent stage in which a new type of fins called biomimetic is to be analyzed and compared.

2

Tunelem doprowadzają wodę do afrykańskich zbiorników retencyjnych

Januszek M.

Geoinżynieria : drogi, mosty, tunele

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2018

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nr 1

82--83

PL

The Lesotho Highlands Water Project to międzynarodowy projekt realizowany w partnerstwie przez rządy Lesotho i Republiki Południowej Afryki. Jego celem jest regulacja rzeki Oranje poprzez budowę tam i zbiorników retencyjnych, a także budowę odpowiedniej infrastruktury wodociągowej-w tym budowę tuneli wodnych.

3

Identification of UAV static aerodynamic characteristics in the water tunnel balance research

Lichoń D., Mikołajczyk A., Kiszkowiak Ł., Łącki T

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2016

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z. 88 [293], nr 2

127--140

EN

This work presents the identification of static aerodynamic characteristics in the water tunnel experiments. The tested object was a scale model of unmanned aerial vehicle (UAV) target drone OCP-Jet. The research was performed in the water tunnel Rolling Hills Research Corporation model no. 2436, Military University of Technology, Warsaw. Water tunnel experiments allow to perform static and dynamic balance measurements, dye flow visualizations and PIV flow field measurements. The advantage of the use of the water tunnel are relatively inexpensive researches and the possibility to use small models manufactured with 3D printing technology. However, testing the flying objects in the water medium has limitations due to difficulties in satisfying the flow similarity criteria. In this paper the researches were focused on identification of the static aerodynamic characteristics with the use of balance measurements. The forces and moments characteristics were performed. The experimental results were compared with full scale aircraft characteristics, calculated with analytical methods and vortex lattice method.

PL

W niniejszej pracy przeprowadzono eksperymentalną analizę zmęczeniową łopatki sprężarki lotniczego silnika turbinowego. Rozkład temperatur na łopatce wykorzystano do określenia długości powstałej w trakcie badań szczeliny zmęczeniowej. Łopatka z karbem symulującym uszkodzenie obcym obiektem została poddana drganiom poprzecznym wstanie rezonansu. Podczas badań zarówno amplituda przemieszczenia wierzchołka ostrza, a także długość pęknięcia były monitorowane. W tym samym czasie wykonano kamerą termowizyjną zdjęcia rozkład temperatury. W pierwszej fazie pracy wykresy amplitudowo-częstotliwościowe uzyskano dla różnej wielkości pęknięć. Określono liczbę cykli obciążeń do inicjacji pęknięć, a także dynamikę wzrostu pęknięć w łopatce sprężarki narażonej na drgania. Dodatkowym efektem pracy jest porównanie długości szczelin zmierzonych bezpośrednio na badanej łopatce jak i na obrazie z rozkładami temperatury wokół pęknięcia. Przedstawiono zalety metody pomiaru długości szczeliny z wykorzystaniem zdjęć z kamery termowizyjnej. Wyniki przedstawione w niniejszym artykule mają wartość teoretyczną i praktyczną.

4

An experimental and numerical study of supercavitating flows around axisymmetric cavitators

Javadpour S. M., Farahat S., Ajam H., Salari M., Nezhad A. H.

Journal of Theoretical and Applied Mechanics

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2016

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Vol. 54 nr 3

795--810

EN

It has been shown that developing a supercavitating flow around under-water projectiles has a significant effect on their drag reduction. As such, it has been a subject of growing attention in the recent decades. In this paper, a numerical and experimental study of supercavitating flows around axisymmetric cavitators is presented. The experiments are conducted in a semi-open loop water tunnel. According to the Reynolds-Averaged Navier-Stokes equations and mass transfer model, a three-component cavitation model is proposed to simulate the cavitating flow. The corresponding governing equations are solved using the finite element method and the mixture Rayleigh-Plesset model. The main objective of this research is to study the effects of some important parameters of these flows such as the cavitation number, Reynolds number and conic angle of the cavitators on the drag coefficient as well as the dimensions of cavities developed around the submerged bodies. A comparison of the numerical and experimental results shows that the numerical method is able to predict accurately the shape parameters of the natural cavitation phenomena such as cavity length, cavity diameter and cavity shape. The results also indicate that the cavitation number declines from 0.32 to 0.25 leading to a 28 percent decrease in the drag coefficient for a 30° cone cavitator. By increasing the Reynolds number, the cavity length is extended up to 322% for a 60° cone cavitator.

5

A methodology of identification of the aircraft translational dynamic stability derivatives in water tunnel experiments

Lichoń D.

Journal of KONES

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2016

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Vol. 23, No. 4

291--296

EN

The aircraft dynamic stability derivatives (DSD) describe the variation of aerodynamics forces and moments with respect to disturbances of kinematic parameters (translational or rotational). The knowledge of DSD is important due to determination of aircraft dynamic stability characteristics. Thus, the identification of DSD is an issue of analytical or numerical analysis and experimental researches. Experimental methods use air or water tunnel tests. The investigated model is submitted to forced oscillations with relatively low amplitude, which simulates the disturbances around steady state flight parameters. The variation of forces and moments are measured by strain balance system, which allows identifying DSD. This work is focused on development the methodology of experimental identification the aircraft translational DSD in water tunnel tests. Study of available publications shows that model manipulator system usually provides rotational movements around three axes. Therefore, the measurements can be performed with respect to rotational velocity disturbances. However, by addition the translational manipulator with one degree of freedom the measurements can be expanded into translational velocity disturbances (normal and sideslip). It is necessary to point that axial velocity disturbance is omitted due to lack of axial force component in strain balance construction. The proposed modification does not affect the construction of rotational manipulator or balance. The article contains translational manipulator scheme, modification of data acquisition system and mathematical process of identification the aircraft translational dynamic stability derivatives.

6

Water tunnel for testing the measurement methods of local flow parameters

Najdecki S., Smolny A., Sobczak K.

Transactions of the Institute of Fluid-Flow Machinery

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2006

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nr 118

15-24

EN

A configuration of the water tunnel with two independently controlled concurrent streams is presented. Two important zones of the flow, namely: an inner layer with even parameter profiles and a mixing layer between two streams, can be observed. The numerical simulation results obtained by means of the CFX-TASC flow code are compared with the experimental investigation results measured by a Pitot probe in the velocity range from 1.7 to 16 m/s.